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Glycemic traits are used to diagnose and monitor type 2 diabetes and cardiometabolic health. To date, most genetic studies of glycemic traits have focused on individuals of European ancestry. Here we aggregated genome-wide association studies comprising up to 281,416 individuals without diabetes (30% non-European ancestry) for whom fasting glucose, 2-h glucose after an oral glucose challenge, glycated hemoglobin and fasting insulin data were available. Trans-ancestry and single-ancestry meta-analyses identified 242 loci (99 novel; P < 5 × 10 -8 ), 80% of which had no significant evidence of between-ancestry heterogeneity. Analyses restricted to individuals of European ancestry with equivalent sample size would have led to 24 fewer new loci. Compared with single-ancestry analyses, equivalent-sized trans-ancestry fine-mapping reduced the number of estimated variants in 99% credible sets by a median of 37.5%. Genomic-feature, gene-expression and gene-set analyses revealed distinct biological signatures for each trait, highlighting different underlying biological pathways. Our results increase our understanding of diabetes pathophysiology by using trans-ancestry studies for improved power and resolution.

Introduction: Sclerostin, an inhibitor of bone formation, has emerged as a potential negative regulator of glucose homeostasis. We aimed to investigate if serum sclerostin associates with insulin sensitivity, beta cell function, prediabetes or metabolic syndrome in healthy men., Materials and Methods: Serum sclerostin was measured in basal and insulin-stimulated samples from 526 men without diabetes from the RISC cohort study. An OGTT was performed at baseline and after 3 years. An IVGTT and a hyperinsulinaemic-euglycaemic clamp were performed at baseline. Insulin sensitivity was estimated by the oral glucose sensitivity index (OGIS) and the M-value relative to insulin levels. Beta cell function was assessed by the acute and total insulin secretion (ISR tot ) and by beta cell glucose sensitivity., Results: Serum sclerostin levels correlated positively with age but were similar in individuals with (n = 69) and without (n = 457) prediabetes or the metabolic syndrome. Serum sclerostin was associated with measures of neither insulin sensitivity nor beta cell function at baseline in age-adjusted analyses including all participants. However, baseline serum sclerostin correlated inversely with OGIS at follow-up in men without prediabetes (B: -0.29 (-0.57, -0.01) p = 0.045), and inversely with beta cell glucose sensitivity in men with prediabetes (B: -13.3 (-26.3, -0.2) p = 0.046). Associations between serum sclerostin and 3-year changes in measures of glucose homeostasis were not observed. Acute hyperinsulinemia suppressed serum sclerostin (p = 0.02), and this reduction correlated with OGIS and ISR tot ., Conclusions: Overall, serum sclerostin was not associated with prediabetes, insulin sensitivity or insulin secretion in healthy men. The inverse relationship between serum sclerostin and insulin sensitivity at follow-up was weak and likely not of clinical relevance. The ability of insulin to reduce sclerostin, possibly promoting bone formation, needs to be clarified., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Sodium-glucose transporter (SGLT)2 inhibitors increase plasma magnesium and plasma phosphate and may cause ketoacidosis, but the contribution of improved glycemic control to these observations as well as effects on other electrolytes and acid-base parameters remain unknown. Therefore, our objective was to compare the effects of SGLT2 inhibitors dapagliflozin and sulfonylurea gliclazide on plasma electrolytes, urinary electrolyte excretion, and acid-base balance in people with Type 2 diabetes (T2D). We assessed the effects of dapagliflozin and gliclazide treatment on plasma electrolytes and bicarbonate, 24-hour urinary pH and excretions of electrolytes, ammonium, citrate, and sulfate in 44 metformin-treated people with T2D and preserved kidney function. Compared with gliclazide, dapagliflozin increased plasma chloride by 1.4 mmol/l (95% CI 0.4-2.4), plasma magnesium by 0.03 mmol/l (95% CI 0.01-0.06), and plasma sulfate by 0.02 mmol/l (95% CI 0.01-0.04). Compared with baseline, dapagliflozin also significantly increased plasma phosphate, but the same trend was observed with gliclazide. From baseline to week 12, dapagliflozin increased the urinary excretion of citrate by 0.93 ± 1.72 mmol/day, acetoacetate by 48 μmol/day (IQR 17-138), and β-hydroxybutyrate by 59 μmol/day (IQR 0-336), without disturbing acid-base balance. In conclusion, dapagliflozin increases plasma magnesium, chloride, and sulfate compared with gliclazide, while reaching similar glucose-lowering in people with T2D. Dapagliflozin also increases urinary ketone excretion without changing acid-base balance. Therefore, the increase in urinary citrate excretion by dapagliflozin may reflect an effect on cellular metabolism including the tricarboxylic acid cycle. This potentially contributes to kidney protection., (© 2020 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society.)

Objective: Tachyphylaxis for slowing of gastric emptying is seen with continuous exposure to glucagon-like peptide 1 (GLP-1). We therefore aimed to establish whether prolonged use of a "short-acting" GLP-1 receptor agonist, lixisenatide, achieves sustained slowing of gastric emptying and reduction in postprandial glycemia., Research Design and Methods: A total of 30 patients with metformin-treated type 2 diabetes underwent assessment of gastric emptying (scintigraphy) and glucose metabolism (dual tracer technique) after a 75-g glucose drink, before and after 8 weeks' treatment with lixisenatide (20 μg subcutaneously daily) or placebo, in a double-blind randomized parallel design., Results: Gastric retention of the glucose drink was markedly increased after lixisenatide versus placebo (ratio of adjusted geometric means for area under the curve [AUC] over 240 min of 2.19 [95% CI 1.82, 2.64], P < 0.001), associated with substantial reductions in the rate of systemic appearance of oral glucose ( P < 0.001) and incremental AUC for blood glucose ( P < 0.001). Lixisenatide suppressed both glucagon ( P = 0.003) and insulin ( P = 0.032), but not endogenous glucose production, over 120 min after oral glucose intake. Postprandial glucose lowering over 240 min was strongly related to the magnitude of slowing of gastric emptying by lixisenatide ( r = -0.74, P = 0.002) and to the baseline rate of emptying ( r = 0.52, P = 0.048) but unrelated to β-cell function (assessed by β-cell glucose sensitivity)., Conclusions: Eight weeks' treatment with lixisenatide is associated with sustained slowing of gastric emptying and marked reductions in postprandial glycemia and appearance of ingested glucose. Short-acting GLP-1 receptor agonists therefore potentially represent an effective long-term therapy for specifically targeting postprandial glucose excursions., (© 2020 by the American Diabetes Association.)

Objective: Interleukin (IL)-1β is involved in obesity-associated inflammation and in the pathogenesis of type 2 diabetes (T2D) mellitus. Our aim was to correlate serum IL-1β and caspase-1 levels with weight loss, glucose metabolism, and insulin resistance (IR) after bariatric surgery., Methods: A total of 32 patients with morbid obesity and T2D (Ob-T2D) and 29 patients with morbid obesity and normal glucose tolerance (Ob-NGT), treated by Roux-en-Y gastric bypass, were studied before and 1 year after surgery. Sixteen healthy individuals served as a control (HC) group. IR was assessed by the oral glucose insulin sensitivity method. Plasma IL-1β levels and caspase-1 were measured., Results: Presurgery BMI was similar in Ob-NGT and Ob-T2D. IR was progressively impaired in Ob-NGT and Ob-T2D (P < 0.0001). Fasting plasma IL-1β and caspase-1 levels were lower in HCs than in patients with Ob-NGT or Ob-T2D (P < 0.02; P = 0.05), and both were inversely correlated with IR (P = 0.01; P = 0.02). After surgery, BMI decreased and IR improved to a similar extent in Ob-NGT and Ob-T2D (P < 0.0001). Plasma caspase-1 concentrations normalized in both groups (P < 0.0001), whereas plasma IL-1β levels normalized only in Ob-NGT., Conclusions: Plasma IL-1β and caspase-1 levels were inversely correlated with IR. Caspase-1 levels normalized after weight loss, whereas IL-1β normalized only in people without T2D, suggesting the persistence of a systemic inflammatory condition in people with T2D., (© 2020 The Obesity Society.)

Aims/hypothesis: The euglycaemic-hyperinsulinaemic clamp is the gold-standard method for measuring insulin sensitivity, but is less suitable for large clinical trials. Thus, several indices have been developed for evaluating insulin sensitivity from the oral glucose tolerance test (OGTT). However, most of them yield values different from those obtained by the clamp method. The aim of this study was to develop a new index to predict clamp-derived insulin sensitivity (M value) from the OGTT-derived oral glucose insulin sensitivity index (OGIS)., Methods: We analysed datasets of people that underwent both a clamp and an OGTT or meal test, thereby allowing calculation of both the M value and OGIS. The population was divided into a training and a validation cohort (n = 359 and n = 154, respectively). After a stepwise selection approach, the best model for M value prediction was applied to the validation cohort. This cohort was also divided into subgroups according to glucose tolerance, obesity category and age., Results: The new index, called PREDIcted M (PREDIM), was based on OGIS, BMI, 2 h glucose during OGTT and fasting insulin. Bland-Altman analysis revealed a good relationship between the M value and PREDIM in the validation dataset (only 9 of 154 observations outside limits of agreement). Also, no significant differences were found between the M value and PREDIM (equivalence test: p < 0.0063). Subgroup stratification showed that measured M value and PREDIM have a similar ability to detect intergroup differences (p < 0.02, both M value and PREDIM)., Conclusions/interpretation: The new index PREDIM provides excellent prediction of M values from OGTT or meal data, thereby allowing comparison of insulin sensitivity between studies using different tests.

Background and Aims: The incretin effect is impaired in type 2 diabetes (T2D), but the underlying mechanisms are only partially understood. We investigated the relationships between the time course of the incretin effect and that of glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) during oral glucose tolerance tests (OGTTs), thereby estimating incretin sensitivity of the beta cell, and its associated factors., Methods and Results: Eight patients with T2D and eight matched subjects with normal glucose tolerance (NGT) received 25, 75, and 125 g OGTTs and corresponding isoglycemic glucose infusions (IIGI). The time course of the incretin effect, representing potentiation of insulin secretion by incretins (P INCR ), was determined by mathematical modelling as the time-dependent fold increase in insulin secretion during OGTT compared to IIGI. The time course of P INCR was correlated with that of both GIP and GLP-1 in each subject (median r = 0.67 in NGT and 0.45 in T2D). We calculated an individual beta cell sensitivity to incretins (S INCR ) using a weighted average of GIP and GLP-1 (pooled incretin concentration, PIC), as the slope of the relationship between P INCR and PIC. S INCR was reduced in T2D (p < 0.01). In the whole group, mean PIC, GIP and GLP-1 concentrations during the OGTT were inversely correlated with S INCR , but T2D had lower PIC, GIP and GLP-1 levels at the same S INCR (p < 0.05)., Conclusion: Relative incretin insensitivity is partly compensated for by higher incretin secretory responses. However, T2D shows both impairment in incretin sensitivity and abnormal compensation by incretin secretion., (Copyright © 2017 The Italian Society of Diabetology, the Italian Society for the Study of Atherosclerosis, the Italian Society of Human Nutrition, and the Department of Clinical Medicine and Surgery, Federico II University. Published by Elsevier B.V. All rights reserved.)

A decline in β-cell function is a prerequisite for the development of type 2 diabetes, yet the level of β-cell function in individuals at risk of the condition is rarely measured. This is due, in part, to the fact that current methods for assessing β-cell function are inaccurate, prone to error, labor-intensive, or affected by glucose-lowering therapy. The aim of the current study was to identify novel circulating biomarkers to monitor β-cell function and to identify individuals at high risk of developing β-cell dysfunction. In a nested case-control study from the Relationship between Insulin Sensitivity and Cardiovascular disease (RISC) cohort (n = 1157), proteomics and miRNA profiling were performed on fasting plasma samples from 43 individuals who progressed to impaired glucose tolerance (IGT) and 43 controls who maintained normal glucose tolerance (NGT) over three years. Groups were matched at baseline for age, gender, body mass index (BMI), insulin sensitivity (euglycemic clamp) and β-cell glucose sensitivity (mathematical modeling). Proteomic profiling was performed using the SomaLogic platform (Colorado, USA); miRNA expression was performed using a modified RT-PCR protocol (Regulus Therapeutics, California, USA). Results showed differentially expressed proteins and miRNAs including some with known links to type 2 diabetes, such as adiponectin, but also novel biomarkers and pathways. In cross sectional analysis at year 3, the top differentially expressed biomarkers in people with IGT/ reduced β-cell glucose sensitivity were adiponectin, alpha1-antitrypsin (known to regulate adiponectin levels), endocan, miR-181a, miR-342, and miR-323. At baseline, adiponectin, cathepsin D and NCAM.L1 (proteins expressed by pancreatic β-cells) were significantly lower in those that progressed to IGT. Many of the novel prognostic biomarker candidates were within the epithelial-mesenchymal transition (EMT) pathway: for example, Noggin, DLL4 and miR-181a. Further validation studies are required in additional clinical cohorts and in patients with type 2 diabetes, but these results identify novel pathways and biomarkers that may have utility in monitoring β-cell function and/ or predicting future decline, allowing more targeted efforts to prevent and intercept type 2 diabetes.

While hyperthyroidism and hypothyroidism cause dysglycemia, the relationship between thyroid hormone levels within the normal range and insulin resistance (IR) is unclear. In 940 participants with strictly normal serum concentrations of free triiodothyronine (fT 3 ), free thyroxine (fT 4 ), and thyroid-stimulating hormone (TSH) followed up for 3 yr, we measured insulin sensitivity (by the insulin clamp technique) and 35 circulating metabolites. At baseline, across quartiles of increasing fT 3 levels (or fT 3 /fT 4 ratio) most features of IR emerged [i.e., male sex, greater body mass index (BMI), waist circumference, heart rate, blood pressure, fatty liver index, free fatty acids, and triglycerides; reduced insulin-mediated glucose disposal; and β-cell glucose sensitivity). In multiadjusted analyses, fT 3 was reciprocally related to insulin sensitivity and, in a subset of 303 subjects, directly related to endogenous glucose production. In multiple regression models adjusting for sex, age, BMI, and baseline value of insulin sensitivity, higher baseline fT 3 levels were significant predictors of decreases in insulin sensitivity. Moreover, baseline fT 3 predicted follow-up increases in glycemia independently of sex, age, BMI, insulin sensitivity, β-cell glucose sensitivity, and baseline glycemia. Serum tyrosine levels were higher with IR and were directly associated with fT 3 ; higher α-hydroxybutyrate levels signaled enhanced oxidative stress, thereby impairing tyrosine degradation. In 25 patients with morbid obesity, surgery-induced weight loss improved IR and consensually lowered fT 3 levels. High-normal fT 3 levels are associated with IR both cross-sectionally and longitudinally, and predict deterioration of glucose tolerance. This association is supported by a metabolite pattern that points at increased oxidative stress as part of the IR syndrome., (Copyright © 2017 the American Physiological Society.)

Aims: To investigate the effect of exenatide on glucose disposal, insulin secretion, ß-cell function, lipolysis and hormone concentrations in non-diabetic, morbidly obese subjects under physiological conditions., Materials and Methods: Patients were assigned to exenatide 10 µg twice daily (EXE, n = 15) or control (CT, n = 15) for 3 months. Patients received a meal test/tracer study (MTT) to measure endogenous glucose production (EGP), rate of oral glucose appearance (RaO), insulin secretion rate (ISR), ß-cell function, hepatic insulin resistance (HIR) and adipose tissue insulin resistance (AT-IR) and insulin sensitivity (IS)., Results: Post treatment, the EXE group showed a significant reduction in body weight ( P < .001). The postmeal time-course of glucose, insulin and ISR showed a lower peak between 60 and 180 minutes in phase with a reduction in RaO ( P < .01). After an initial similar suppression, EGP resumed at higher rates between 60 and 180 minutes ( P = .02) in EXE vs CT, while total RaO and EGP were similar throughout the MTT. In EXE, the postmeal glucagon, GLP1 and GIP responses were reduced ( P < .05). Fasting and postprandial lipolysis and ß-cell function were unaltered by active treatment. HIR, AT-IR and IS were all improved after exenatide treatment ( P < .05)., Conclusions: In morbidly obese non-diabetic subjects, exenatide causes weight loss, decreased postprandial glycaemia and glucagon response without changes in ß-cell function. These effects are consequent upon delayed oral glucose appearance in the circulation. Exenatide treatment is also associated with an improvement in hepatic, adipose tissue and whole-body IS with no influence on postprandial lipolysis., (© 2016 John Wiley & Sons Ltd.)

Restoring euglycaemia for weeks or months improves insulin secretion in patients with type 2 diabetes (T2D). We tested whether mild decrements in fasting glucose (FPG) acutely affect β-cell function and insulin sensitivity. Thirteen normotolerant (NGT) and 10 T2D patients volunteered in pairs. In an isoglycemic test (Iso), after 100 min of stabilization, an incremental glucose infusion over 3 h was applied to raise plasma glucose to >22 mmol/l, followed by an arginine challenge; in a subisoglycemic test (Sub), a glucose infusion matching the plasma glucose time course of Iso was preceded by an insulin infusion period (100 min) aimed at maintaining a mild FPG reduction while avoiding hypoglycaemia. β-Cell function was assessed by mathematical modeling, whereas the acute insulin response (AIR) to arginine was determined from C-peptide levels. In the Sub, FPG was lowered by 17% in NGT and 31% in T2D patients. On the glucose ramp, total insulin release was lower in Sub than in Iso in both groups [from 106 (43) to 75 (39) nmol/m(-2) in NGT and from 71 (63) to 64 (41) nmol/m(-2) in T2D, P = 0.001]. In the Sub, β-cell glucose sensitivity was significantly (P = 0.008) reduced in NGT [from 50 (31) to 43 (21) pmol·min(-1)·m(-2)·mM(-1)] but not in T2D [19 (20) to 20 (20) pmol·min(-1)·m(-2)·mM(-1)]. Likewise, AIR was lowered in NGT [8.9 (4.6) to 7.1 (4.4) nmol/l, P = 0.048] but not in T2D [4.7 (3.3) to 5.3 (3.2) nmol/l]. Insulin sensitivity improved in NGT but only marginally in T2D. Prestimulatory glucose levels acutely influence both β-cell function and insulin sensitivity differentially in nondiabetic and type 2 diabetic individuals., (Copyright © 2016 the American Physiological Society.)

Aims/hypothesis: Small protein or lipid preloads are able to improve glucose tolerance to a different extent and through different and poorly defined mechanisms. We aimed at quantifying the effect of a mixed protein and lipid preload and at evaluating the underlying mechanisms., Methods: Volunteers with normal (NGT, n = 12) or impaired (IGT, n = 13) glucose tolerance and patients with type 2 diabetes (n = 10) underwent two OGTTs coupled to the double glucose tracer protocol, preceded by either 50 g of parmesan cheese, a boiled egg and 300 ml of water, or 500 ml of water. We measured plasma glucose, insulin, C-peptide, glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), pancreatic polypeptide (PP), NEFA and glucose tracers, and calculated glucose fluxes, beta cell function variables, insulin sensitivity and clearance., Results: After the nutrient preload, the OGTT-induced rise of plasma glucose was lower than after water alone in each study group. This reduction—more pronounced across classes of glucose tolerance (NGT -32%, IGT -37%, type 2 diabetes -49%; p < 0.002)—was the result of different combinations of slower exogenous glucose rate of appearance, improved beta cell function and reduced insulin clearance, in this order of relevance, which were associated with an only mild stimulation of GIP and GLP-1., Conclusions/interpretation: After a non-glucidic nutrient preload, glucose tolerance improved in proportion to the degree of its baseline deterioration through mechanisms that appear particularly effective in type 2 diabetes. Exploiting the physiological responses to nutrient ingestion might reveal, at least in the first stages of the diabetic disease, a potent tool to improve daily life glycaemic control., Trial Registration: ClinicalTrials.gov NCT02342834 FUNDING: This work was supported by grants from the University of Pisa (Fondi di Ateneo) and by FCT grant (PIC/IC/82956/2007).

Aims/hypothesis: It is a commonly held view that chronically elevated NEFA levels adversely affect insulin secretion and insulin action (lipotoxicity). However, the effect of NEFA on beta cell function has only been explored using acute NEFA elevations. Our aim was to analyse the relationship between endogenous NEFA levels and beta cell function., Methods: In 1,267 individuals followed-up for 3 years, we measured insulin sensitivity (by clamp) and beta cell function (by C-peptide modelling during OGTT and as the acute insulin response [AIR] to IVGTT)., Results: At baseline, both fasting and insulin-suppressed NEFA levels were higher across glucose tolerance groups, while insulin sensitivity was lower, insulin output was higher, and beta cell glucose sensitivity and AIR were lower (all p < 0.0001). In multiple logistic analyses adjusting for age, BMI, WHR and glucose tolerance, both fasting and insulin-suppressed NEFA levels were inversely related to insulin sensitivity, as expected (both p < 0.0001). Furthermore, after adjusting for insulin sensitivity, insulin-suppressed NEFA were positively associated with total insulin output (p = 0.0042). In contrast, neither fasting nor insulin-suppressed NEFA were related to beta cell glucose sensitivity or AIR. At follow-up, worsening of glucose tolerance (n = 126) was predicted by lower insulin and beta cell glucose sensitivity. In this model, baseline NEFA were not significant predictors of progression., Conclusions/interpretation: In the non-diabetic state and in subjects with impaired glucose tolerance, circulating endogenous NEFA are not independently associated measures of beta cell function, and do not predict deterioration of glucose tolerance. Thus, in the Relationship Between Insulin Sensitivity and Cardiovascular Disease (RISC) cohort there is no evidence for beta cell lipotoxicity of endogenous total NEFA concentrations.

Objective: The objective was to test the clinical utility of Quantose M(Q) to monitor changes in insulin sensitivity after pioglitazone therapy in prediabetic subjects. Quantose M(Q) is derived from fasting measurements of insulin, α-hydroxybutyrate, linoleoyl-glycerophosphocholine, and oleate, three nonglucose metabolites shown to correlate with insulin-stimulated glucose disposal., Research Design and Methods: Participants were 428 of the total of 602 ACT NOW impaired glucose tolerance (IGT) subjects randomized to pioglitazone (45 mg/d) or placebo and followed for 2.4 years. At baseline and study end, fasting plasma metabolites required for determination of Quantose, glycated hemoglobin, and oral glucose tolerance test with frequent plasma insulin and glucose measurements to calculate the Matsuda index of insulin sensitivity were obtained., Results: Pioglitazone treatment lowered IGT conversion to diabetes (hazard ratio = 0.25; 95% confidence interval = 0.13-0.50; P < .0001). Although glycated hemoglobin did not track with insulin sensitivity, Quantose M(Q) increased in pioglitazone-treated subjects (by 1.45 [3.45] mg·min(-1)·kgwbm(-1)) (median [interquartile range]) (P < .001 vs placebo), as did the Matsuda index (by 3.05 [4.77] units; P < .0001). Quantose M(Q) correlated with the Matsuda index at baseline and change in the Matsuda index from baseline (rho, 0.85 and 0.79, respectively; P < .0001) and was progressively higher across closeout glucose tolerance status (diabetes, IGT, normal glucose tolerance). In logistic models including only anthropometric and fasting measurements, Quantose M(Q) outperformed both Matsuda and fasting insulin in predicting incident diabetes., Conclusions: In IGT subjects, Quantose M(Q) parallels changes in insulin sensitivity and glucose tolerance with pioglitazone therapy. Due to its strong correlation with improved insulin sensitivity and its ease of use, Quantose M(Q) may serve as a useful clinical test to identify and monitor therapy in insulin-resistant patients.

Plasma glucose thresholds for diagnosis of type 2 diabetes are currently based on outcome data (risk of retinopathy), an inherently ill-conditioned approach. A radically different approach is to consider the mechanisms that control plasma glucose, rather than its relation to an outcome. We developed a constraint optimization algorithm to find the minimal glucose levels associated with the maximized combination of insulin sensitivity and β-cell function, the two main mechanisms of glucose homeostasis. We used a training cohort of 1,474 subjects (22% prediabetic, 7.7% diabetic) in whom insulin sensitivity was measured by the clamp technique and β-cell function was determined by mathematical modeling of an oral glucose tolerance test. Optimized fasting glucose levels were ≤ 87 and ≤ 89 mg/dl in ≤ 45-yr-old women and men, respectively, and ≤ 92 and ≤ 95 mg/dl in >45-yr-old women and men, respectively; the corresponding optimized 2-h glucose levels were ≤ 96, ≤ 98, ≤ 103, and ≤ 105 mg/dl. These thresholds were validated in three prospective cohorts of nondiabetic subjects (Relationship Between Insulin Sensitivity and Cardiovascular Disease Study, Botnia Study, and Mexico City Diabetes Study) with baseline and follow-up oral glucose tolerance tests. Of 5,593 participants, 452 progressed to diabetes. Similarly, in the three cohorts, subjects with glucose levels above the estimated thresholds had an odds ratio of 3.74 (95% confidence interval = 2.64-5.48) of progressing, substantially higher than the risk carried by baseline conventionally defined prediabetes [odds ratio = 2.32 (95% confidence interval = 1.91-2.81)]. The concept that optimization of glucose concentrations by direct measures of insulin sensitivity and β-cell function identifies gender- and age-specific thresholds that bear on disease progression is proven in a physiologically sound, quantifiable manner., (Copyright © 2015 the American Physiological Society.)

Fasting glucose and insulin are intermediate traits for type 2 diabetes. Here we explore the role of coding variation on these traits by analysis of variants on the HumanExome BeadChip in 60,564 non-diabetic individuals and in 16,491 T2D cases and 81,877 controls. We identify a novel association of a low-frequency nonsynonymous SNV in GLP1R (A316T; rs10305492; MAF=1.4%) with lower FG (β=-0.09±0.01 mmol l(-1), P=3.4 × 10(-12)), T2D risk (OR[95%CI]=0.86[0.76-0.96], P=0.010), early insulin secretion (β=-0.07±0.035 pmolinsulin mmolglucose(-1), P=0.048), but higher 2-h glucose (β=0.16±0.05 mmol l(-1), P=4.3 × 10(-4)). We identify a gene-based association with FG at G6PC2 (pSKAT=6.8 × 10(-6)) driven by four rare protein-coding SNVs (H177Y, Y207S, R283X and S324P). We identify rs651007 (MAF=20%) in the first intron of ABO at the putative promoter of an antisense lncRNA, associating with higher FG (β=0.02±0.004 mmol l(-1), P=1.3 × 10(-8)). Our approach identifies novel coding variant associations and extends the allelic spectrum of variation underlying diabetes-related quantitative traits and T2D susceptibility.

The oral glucose tolerance test (OGTT) is the only method to diagnose patients having impaired glucose tolerance (IGT), but its use has diminished considerably in recent years. Metabolomic profiling studies have identified a number of metabolites whose fasting levels are associated with dysglycemia and type 2 diabetes. These metabolites may serve as the basis of an alternative test for IGT. Using the stable isotope dilution technique, quantitative assays were developed for 23 candidate biomarker metabolites. These metabolites were measured in fasting plasma samples taken just prior to an OGTT from 1623 nondiabetic subjects: 955 from the Relationship between Insulin Sensitivity and Cardiovascular Disease Study (RISC Study; 11.7% IGT) and 668 subjects from the Diabetes Mellitus and Vascular Health Initiative (DMVhi) cohort from the DEXLIFE project (11.8% IGT). The associations between metabolites, anthropometric, and metabolic parameters and 2hPG values were assessed by Pearson correlation coefficients and Random Forest classification analysis to rank variables for their ability to distinguish IGT from normal glucose tolerance (NGT). Multivariate logistic regression models for estimating risk of IGT were developed and evaluated using AUCs calculated from the corresponding ROC curves. A model based on the fasting plasma levels of glucose, α-hydroxybutyric acid, β-hydroxybutyric acid, 4-methyl-2-oxopentanoic acid, linoleoylglycerophosphocholine, oleic acid, serine and vitamin B5 was optimized in the RISC cohort (AUC = 0.82) and validated in the DMVhi cohort (AUC = 0.83). A novel, all-metabolite-based test is shown to be a discriminate marker of IGT. It requires only a single fasted blood draw and may serve as a more convenient surrogate for the OGTT or as a means of identifying subjects likely to be IGT., (© 2014 Diabetes Technology Society.)

Aims: Amino acid (AA) metabolism is altered in type 2 diabetes (T2D), and fasting levels of α-hydroxybutyrate (α-HB), a biomarker for insulin resistance, have been suggested to track AA metabolism. We investigated the changes in AA and α-HB induced by a mixed-meal tolerance test (MTT) and the effects of sitagliptin treatment., Methods: Forty-seven T2D patients [56 ± 7 years, body mass index (BMI) 29.9 ± 4.2 kg/m(2) ] were randomized to sitagliptin (100 mg/day, 6 weeks) or placebo. Seven age- and BMI-matched non-diabetic subjects served as control (CT)., Results: During a 5-h MTT, branched-chain AA (BCAA) peaked earlier in T2D than CT [75(25) vs. 62(3) mmol/l · h over 2 h, median(interquartile range), p = 0.05], and rose higher [5-h increment: 31(23) vs. 19(24) mmol/l · h, p = 0.05]. Fasting α-HB was higher [7.5(2.7) vs. 5.9(1.3) µg/ml, p = 0.04 T2D vs. CT], and its meal-induced increments were larger [24(99) vs. -41(86) µg/ml · h, p = 0.006]. Plasma non-esterified fatty acids (NEFA) declined during MTT, but their increments were greater in patients (53 ± 16 vs. 35 ± 10 mEq/l · h, p = 0.005). Compared to placebo, both BCAA [-6.4(21.1) vs. 0.0(48.0) mmol/l · h, p = 0.01] and α-HB increments [-114(250) vs. 114(428) µg/ml · h, p = 0.002] decreased with sitagliptin, and meal-induced NEFA suppression was improved. Changes in BCAA and α-HB were reciprocally related to changes in insulin sensitivity (ρ = -0.37 and -0.43, p ≤ 0.01)., Conclusions: T2D is associated with a hyperaminoacidaemic response to MTT, which circulating α-HB levels track. Sitagliptin-induced glycaemic improvement was associated with reductions in BCAA and α-HB excursions and better NEFA suppression, in parallel with improved insulin sensitivity, confirming that α-HB is a readout of metabolic overload., (© 2014 John Wiley & Sons Ltd.)

Although GLP-1 has been suggested as a major factor for the marked improvement of glucose tolerance commonly seen after sleeve gastrectomy (SG), several observations challenge this hypothesis. To better understand the role of GLP-1 in the remission of type 2 diabetes mellitus (T2DM) long term after SG in humans, we conducted two separate cross-sectional studies: 1) the GLP-1 response to a standardized mixed liquid meal (SMLM) was compared in subjects with T2DM antedating SG but with different long-term (>2 years) T2DM outcomes (remission, relapse, or lack of remission) (study 1) and 2) the effect of GLP-1 receptor blockade with exendin (9-39) on glucose tolerance was examined in subjects with T2DM antedating surgery, who had undergone SG and presented with long-term T2DM remission (study 2). In study 1, we observed a comparable GLP-1 response to the SMLM regardless of the post-SG outcome of T2DM. In study 2, the blockade of GLP-1 action resulted in impaired insulin secretion but limited deterioration of glucose tolerance. Thus, our data suggest the enhanced GLP-1 secretion observed long term after SG is neither sufficient nor critical to maintain normal glucose tolerance in subjects with T2DM antedating the surgery., (© 2014 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.)

Objective: We evaluated whether the association of insulin sensitivity with HDL cholesterol (HDL) and triglycerides is influenced by major plasma apolipoproteins, as suggested by recent experimental evidence., Research Design and Methods: This study included a cross-sectional analysis of the RISC Study, a multicenter European clinical investigation in 1,017 healthy volunteers balanced in sex (women 54%) and age strata (range 30-60 years). Insulin sensitivity (M/I in µmol ⋅ min(-1) ⋅ kgFFM(-1) ⋅ nM(-1)) was measured by the clamp technique and apolipoproteins (ApoB, -C3, -A1, and -E) by Multiplex Technology., Results: The center-, sex-, and age-adjusted standardized regression coefficients (STDβ) with M/I were similar for HDL and triglycerides (+19.9 ± 1.9 vs. -20.0 ± 2.0, P < 0.0001). Further adjustment for triglycerides (or HDL), BMI, and adiponectin (or nonesterified fatty acid) attenuated the strength of the association of M/I with both HDL (STDβ +6.4 ± 2.3, P < 0.01) and triglycerides (-9.5 ± 2.1, P < 0.001). Neither ApoA1 nor ApoE and ApoB showed any association with M/I independent from plasma HDL cholesterol and triglycerides. ApoC3, in contrast, in both men and women, was positively associated with M/I independently of plasma lipids. A relative enrichment of plasma lipids with ApoC3 is associated with lower body fat percentage and lower plasma alanine amino transferase., Conclusions: Our results suggest that HDL cholesterol modulates insulin sensitivity through a mechanism that is partially mediated by BMI and adiponectin but not by ApoA1. Similarly, the influence of triglycerides on insulin sensitivity is in part mediated by BMI and is unrelated to ApoE or ApoB, but it is significantly modulated by ApoC3, which appears to protect from the negative effect of plasma lipids.

Objective: To investigate the long-term safety and efficacy of empagliflozin, a sodium glucose cotransporter 2 inhibitor; sitagliptin; and metformin in patients with type 2 diabetes., Research Design and Methods: In this randomized, open-label, 78-week extension study of two 12-week, blinded, dose-finding studies of empagliflozin (monotherapy and add-on to metformin) with open-label comparators, 272 patients received 10 mg empagliflozin (166 as add-on to metformin), 275 received 25 mg empagliflozin (166 as add-on to metformin), 56 patients received metformin, and 56 patients received sitagliptin as add-on to metformin., Results: Changes from baseline in HbA1c at week 90 were -0.34 to -0.63% (-3.7 to -6.9 mmol/mol) with empagliflozin, -0.56% (-6.1 mmol/mol) with metformin, and -0.40% (-4.4 mmol/mol) with sitagliptin. Changes from baseline in weight at week 90 were -2.2 to -4.0 kg with empagliflozin, -1.3 kg with metformin, and -0.4 kg with sitagliptin. Adverse events (AEs) were reported in 63.2-74.1% of patients on empagliflozin and 69.6% on metformin or sitagliptin; most AEs were mild or moderate in intensity. Hypoglycemic events were rare in all treatment groups, and none required assistance. AEs consistent with genital infections were reported in 3.0-5.5% of patients on empagliflozin, 1.8% on metformin, and none on sitagliptin. AEs consistent with urinary tract infections were reported in 3.8-12.7% of patients on empagliflozin, 3.6% on metformin, and 12.5% on sitagliptin., Conclusions: Long-term empagliflozin treatment provided sustained glycemic and weight control and was well tolerated with a low risk of hypoglycemia in patients with type 2 diabetes.

Objective: Despite a wealth of experimental data in animal models, the independent association of insulin resistance with early carotid atherosclerosis in man has not been demonstrated., Approach and Results: We studied a European cohort of 525 men and 655 women (mean age, 44 ± 8 years) free of conditions known to affect carotid wall (diabetes mellitus, hypertension, and dyslipidemia). All subjects received an oral glucose tolerance test, a euglycemic hyperinsulinemic clamp (M/I as a measure of insulin sensitivity), and B-mode carotid ultrasound. In 833 participants (380 men), the carotid ultrasound was repeated after 3 years. In men, baseline intima-media thickness in the common carotid artery (CCA-IMT) was significantly higher (P<0.05) in the lowest M/I tertile, whereas in women CCA-IMT was higher (P<0.0005) in the highest fasting plasma glucose tertile (after adjustment for established risk factors). In multiple regression models, with CCA-IMT as the dependent variable and with risk factors and univariate metabolic correlates as independent variables, circulating free fatty acids and the leptin:adiponectin ratio replaced M/I as independent metabolic determinants of CCA-IMT in men. The strongest metabolic determinant of CCA-IMT in women was fasting plasma glucose. Three-year CCA-IMT changes were not associated with any cardio-metabolic risk factor., Conclusions: In young-to-middle aged apparently healthy people, the association of CCA-IMT with insulin sensitivity and its metabolic correlates differs between men and women. Lower insulin sensitivity is associated with higher IMT only in men; this association seems to be mediated by circulating free fatty acids and adipocytokines. In women, CCA-IMT is independently associated with fasting plasma glucose.

Aims: Ipragliflozin is a novel, selective inhibitor of sodium glucose co-transporter 2 (SGLT2 inhibitor) in clinical development for type 2 diabetes mellitus (T2DM) treatment. This study assessed the efficacy and safety of different doses of ipragliflozin., Methods: In a 12-week, multicentre, double-blind, randomized, placebo-controlled, dose-finding study patients with inadequate glycaemic control on metformin monotherapy (≥1500 mg/day) were randomized to one of four ipragliflozin treatment groups (12.5, 50, 150 or 300 mg once daily) or placebo. Primary efficacy outcome was mean change from baseline in haemoglobin A1c (HbA1c) compared to placebo at week 12. Adverse events (AEs), vital signs and laboratory safety measurements were assessed., Results: Ipragliflozin dose dependently decreased HbA1c from baseline to week 12 compared to placebo (-0.22, -0.34, -0.40 and -0.48% for ipragliflozin 12.5, 50, 150 and 300 mg, respectively). Decreases in body weight and blood pressure were observed for all ipragliflozin groups. AEs occurred in 39.7-51.4% of the ipragliflozin groups and 39.4% of placebo patients. Urinary tract infections (1.4-6.9 vs. 6.1%), genital infections (0-4.3 vs. 1.5%) and hypoglycaemia (0-5.9 vs. 3.0%) were similar in the ipragliflozin and placebo groups, respectively, without dose dependency. There were no clinically relevant effects on other safety measurements., Conclusions: Ipragliflozin treatment improved glycaemic control when added to metformin therapy and may be associated with weight loss and reductions in blood pressure compared to placebo. No safety or tolerability concerns were identified at any of the tested doses supporting the further development of ipragliflozin at ≥50 mg doses in T2DM patients., (© 2012 Blackwell Publishing Ltd.)

Background: Insulin resistance (IR) can precede the dysglycemic states of prediabetes and type 2 diabetes mellitus (T2DM) by a number of years and is an early marker of risk for metabolic and cardiovascular disease. There is an unmet need for a simple method to measure IR that can be used for routine screening, prospective study, risk assessment, and therapeutic monitoring. We have reported several metabolites whose fasting plasma levels correlated with insulin sensitivity. These metabolites were used in the development of a novel test for IR and prediabetes., Methods: Data from the Relationship between Insulin Sensitivity and Cardiovascular Disease Study were used in an iterative process of algorithm development to define the best combination of metabolites for predicting the M value derived from the hyperinsulinemic euglycemic clamp, the gold standard measure of IR. Subjects were divided into a training set and a test set for algorithm development and validation. The resulting calculated M score, M(Q), was utilized to predict IR and the risk of progressing from normal glucose tolerance to impaired glucose tolerance (IGT) over a 3 year period., Results: M(Q) correlated with actual M values, with an r value of 0.66. In addition, the test detects IR and predicts 3 year IGT progression with areas under the curve of 0.79 and 0.70, respectively, outperforming other simple measures such as fasting insulin, fasting glucose, homeostatic model assessment of IR, or body mass index., Conclusions: The result, Quantose(TM), is a simple test for IR based on a single fasting blood sample and may have value as an early indicator of risk for the development of prediabetes and T2DM., (© 2013 Diabetes Technology Society.)

An input-output schematization of plasma glucose homeostasis provides quantitative information on glucose fluxes and their control by insulin. Insulin action is dependent on the target tissue, the route of delivery, and the kinetics of insulin activation and deactivation, which are different for glucose production and disposal and are a function of insulin resistance. Under normal conditions, the closed-loop control of minute-by-minute insulin release by arterial glucose levels protects against both hyperglycemia and hypoglycemia. Open-loop insulin therapy faces the complexities of insulin pharmacokinetics and pharmacodynamics. Insulin therapy thus remains defiantly empiric., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Aims/hypothesis: The value of diagnostic categories of glucose intolerance for predicting type 2 diabetes is much debated. We therefore sought to estimate relative and population-attributable risk of different definitions based on fasting (impaired fasting glucose [IFG]) or 2 h plasma glucose concentrations (impaired glucose tolerance [IGT]) and to describe the associated clinical phenotypes., Methods: We prospectively observed a population-based cohort of 1,963 non-diabetic participants (mean age 47 years), in whom an OGTT was performed at baseline and 7 years later., Results: IGT was fivefold more prevalent (13.5%) than IFG. In both categories, participants were older, heavier, hyperinsulinaemic, hyperproinsulinaemic and dyslipidaemic compared with participants with normal glucose tolerance. Relative risk of incident diabetes was similar for IFG and IGT categories (3.73 [95% CI: 2.18-6.39] and 4.01 [95% CI: 3.12-5.14], respectively), but the population-attributable risk was fivefold higher for IGT (29% [95% CI: 26-32]) than for IFG (6% [95% CI: 5-7]). Isolated IFG carried no increase in risk. Lowering the threshold to 5.6 mmol/l raised the population-attributable risk of IFG to 23% (95% CI: 20-25); its contribution to diabetes progression, however, was largely due to co-existent IGT. In multivariate analysis adjusting for sex, age, familial diabetes and BMI, fasting and 2 h glucose were independent predictors., Conclusions/interpretation: Fasting and 2 h glucose values are independent predictors of incident diabetes. Isolated IFG is not a high-risk condition; lowering the diagnostic threshold increases the population-attributable risk of IFG fourfold, but performing an OGTT captures additional diabetes progressors compared with the number identified by IFG.

The quantitative study of beta-cell function has relied on mathematical models for almost 40 years. During the last decades, the initial elaborate models have been simplified with the aim of obtaining mathematical methods suitable for the assessment of beta-cell function in an individual from an intravenous test. In more recent times, modelling methods have been proposed for analysing oral glucose tolerance tests or meal tests. In this review, we describe these methods with particular emphasis on an approach we have developed. We discuss the relevance of potentiation of insulin secretion in an oral glucose test, which our model has reintroduced after the historical models. We provide evidence on the validity of the method and illustrate significant applications. We emphasize the importance of quantifying beta-cell function through multiple indices and highlight how our approach has provided new insight on the relationships between beta-cell function and insulin sensitivity and on the role of beta-cell function in glucose intolerance and diabetes.

Aims/hypothesis: Hyperglycaemia and hyperinsulinaemia have opposite effects on endothelium-dependent vasodilatation in microcirculation, but the net effect elicited by glucose ingestion and the separate influence of glucose tolerance are unknown., Methods: In participants with normal glucose tolerance (NGT), impaired glucose tolerance (IGT) or diabetic glucose tolerance, multiple plasma markers of both oxidative stress and endothelial activation, and forearm vascular responses (plethysmography) to intra-arterial acetylcholine (ACh) and sodium nitroprusside (SNP) infusions were measured before and after glucose ingestion. In another IGT group, we evaluated the time-course of the skin vascular responses (laser Doppler) to ACh and SNP (by iontophoresis) 1, 2 and 3 h into the OGTT; the plasma glucose profile was then reproduced by means of a variable intravenous glucose infusion and the vascular measurements repeated., Results: Following oral glucose, plasma antioxidants were reduced by 5% to 10% (p < 0.01) in all patient groups. The response to acetylcholine was not affected by glucose ingestion in any group, while the response to SNP was attenuated, particularly in the IGT group. The ACh:SNP ratio was slightly improved therefore in all groups, even in diabetic participants, in whom it was impaired basally. A time-dependent improvement in ACh:SNP ratio was also observed in skin microcirculation following oral glucose; this improvement was blunted when matched hyperglycaemia was coupled with lower hyperinsulinaemia (intravenous glucose)., Conclusions/interpretation: Regardless of glucose tolerance, oral glucose does not impair endothelium-dependent vasodilatation either in resistance arteries or in the microcirculation, despite causing increased oxidative stress; the endogenous insulin response is probably responsible for countering any inhibitory effect on vascular function.

Objective: To quantitate the separate impact of obesity and hyperglycemia on the incretin effect (i.e., the gain in beta-cell function after oral glucose versus intravenous glucose)., Research Design and Methods: Isoglycemic oral (75 g) and intravenous glucose administration was performed in 51 subjects (24 with normal glucose tolerance [NGT], 17 with impaired glucose tolerance [IGT], and 10 with type 2 diabetes) with a wide range of BMI (20-61 kg/m(2)). C-peptide deconvolution was used to reconstruct insulin secretion rates, and beta-cell glucose sensitivity (slope of the insulin secretion/glucose concentration dose-response curve) was determined by mathematical modeling. The incretin effect was defined as the oral-to-intravenous ratio of responses. In 8 subjects with NGT and 10 with diabetes, oral glucose appearance was measured by the double-tracer technique., Results: The incretin effect on total insulin secretion and beta-cell glucose sensitivity and the GLP-1 response to oral glucose were significantly reduced in diabetes compared with NGT or IGT (P

Aims/hypothesis: Both energy restriction (ER) per se and weight loss improve glucose metabolism in obese insulin-treated type 2 diabetic patients. Short-term ER decreases basal endogenous glucose production (EGP) but not glucose disposal. In contrast the blood glucose-lowering mechanism of long-term ER with substantial weight loss has not been fully elucidated. The aim of this study was to investigate the effect of loss of 50% of excess weight [50% excess weight reduction (EWR)] on EGP, whole-body insulin sensitivity and the disturbed myocellular insulin-signalling pathway in ten obese insulin-treated type 2 diabetic patients., Methods: A euglycaemic-hyperinsulinaemic clamp with stable isotopes ([6,6-(2)H2]glucose and [2H5]glycerol) combined with skeletal muscle biopsies was performed during a very low energy diet (VLED; 1,883 kJ/day) on day 2 and again after 50% EWR. Oral blood glucose-lowering agents and insulin were discontinued 3 weeks prior to the VLED and at the start of the VLED, respectively., Results: Loss of 50% EWR (20.3+/-2.2 kg from day 2 to day of 50% EWR) normalised basal EGP and improved insulin sensitivity, especially insulin-stimulated glucose disposal (18.8+/-2.0 to 39.1+/-2.8 micromol kg fat-free mass(-1) min(-1), p=0.001). The latter was accompanied by improved insulin signalling at the level of the recently discovered protein kinase B/Akt substrates AS160 and PRAS40 along with a decrease in intramyocellular lipid (IMCL) content., Conclusions/interpretation: Considerable weight loss in obese, insulin-treated type 2 diabetic patients normalises basal EGP and improves insulin sensitivity resulting from an improvement in insulin signal transduction in skeletal muscle. The decrease in IMCL might contribute to this effect.

Aims/hypothesis: Gestational diabetes (GDM) carries a high risk of subsequent diabetes. We asked what impact prior GDM has on beta cell function and insulin action in women who maintain normal glucose tolerance (NGT) for a long time., Methods: Ninety-one women with NGT (aged 41 +/- 8 years, mean+/-SD) were studied (by mathematical modelling of the C-peptide response to an OGTT) 7 [6] years (median [interquartile range]) after the index pregnancy, during which 52 had GDM (pGDM) and 39 had NGT (pNGT). In all women an OGTT had also been performed at 29 +/- 3 weeks of the index pregnancy., Results: Women with pGDM were matched with women with pNGT for age, familial diabetes, time and weight gain since index pregnancy, parity, BMI (25.4 +/- 3.9 vs 26.8 +/- 6.4 kg/m(2)), and fasting (4.64 +/- 0.56 vs 4.97 +/- 0.46 mmol/l) and 2 h plasma glucose levels (5.91 +/- 1.14 vs 5.91 +/- 1.21 mmol/l). Nonetheless, fasting (49 [29] vs 70 [45] pmol min(-1) m(-2), p < 0.001) and total insulin secretion (32 [17] vs 48 [21] nmol m(-2), p < 0.0001) and beta cell glucose sensitivity (slope of the insulin secretion/plasma glucose concentration-response function) (95 [71] vs 115 [79] pmol min(-1) m(-2) (mmol/l)(-1), p = 0.025) were reduced in the pGDM group compared with the pNGT group, while insulin sensitivity was preserved (424 [98] vs 398 [77] ml min(-1) m(-2)). At index pregnancy, women with pGDM and those with pNGT had similar age and BMI. However, both insulin sensitivity (359 [93] vs 417 [92] ml min(-1) m(-2), p = 0.0012) and the insulin/glucose incremental area ratio (an empirical index of beta cell function; 98 [74] vs 138 [122] pmol/mmol, p = 0.028) were reduced in women with pGDM., Conclusions: Even in women who maintain normal insulin sensitivity, impaired beta cell function is carried over into the NGT status several years after a GDM pregnancy.

Context: The interaction of advanced glycation end products, including Nepsilon-(carboxymethyl)lysine-protein adducts (CML) and S100A12 protein, with their cellular receptor (RAGE) is implicated in the pathogenesis of diabetic vascular complications. RAGE has a circulating secretory receptor form, soluble RAGE (sRAGE), which, by neutralizing the action of advanced glycation end products, might exert a protective role against the development of cardiovascular disease., Objective: The objective of the study was to investigate whether plasma sRAGE levels are associated with glycemic control, proinflammatory factors, or circulating ligands of RAGE such as plasma CML and S100A12 protein., Study Design: We studied 160 subjects, 84 subjects with type 2 diabetes (aged 60 +/- 7 yr) and 76 nondiabetic controls (aged 45 +/- 10 yr)., Results: Plasma sRAGE was lower in diabetic patients than controls [141 (53-345) vs. 735 (519-1001) pg/ml, median (interquartile range), P < 0.0001], whereas CML levels were higher in diabetic patients than controls [67.9 (46.0-84.7) vs. 43.4 (28.0-65.0) microg/ml, P < 0.0001]. In stepwise regression analysis of the whole data set, hemoglobin A1c, insulin resistance (as homeostasis model assessment), and C-reactive protein were independently associated with plasma sRAGE, whereas age was not. In a subgroup of 26 diabetic and 24 nondiabetic subjects of similar age (54 +/- 3 yr), plasma S100A12 levels were higher in diabetic subjects [49 (39-126) vs. 28 (21-39) ng/ml]. Moreover, low sRAGE and high S100A12 were strongly associated with increased risk for cardiovascular disease (Framingham score). In this subgroup, the plasma S100A12 level was the only determinant of plasma sRAGE concentration., Conclusion: Plasma level of sRAGE is down-regulated in chronic hyperglycemia; among its ligands, S100A12 protein, but not CML, appears to be associated with this effect.

Insulin resistance is a treatable precursor of diabetes and potentially of cardiovascular disease as well. To identify insulin-resistant patients, we developed decision rules from measurements of obesity, fasting glucose, insulin, lipids, and blood pressure and family history in 2,321 (2,138 nondiabetic) individuals studied with the euglycemic insulin clamp technique at 17 European sites; San Antonio, Texas; and the Pima Indian reservation. The distribution of whole-body glucose disposal appeared to be bimodal, with an optimal insulin resistance cutoff of <28 micromol/min . kg lean body mass. Using recursive partitioning, we developed three types of classification tree models: the first, based on clinical measurements and all available laboratory determinations, had an area under the receiver operator characteristic curve (aROC) of 90.0% and generated a simple decision rule: diagnose insulin resistance if any of the following conditions are met: BMI >28.9 kg/m(2), homeostasis model assessment of insulin resistance (HOMA-IR) >4.65, or BMI >27.5 kg/m(2) and HOMA-IR >3.60. The fasting serum insulin concentrations corresponding to these HOMA-IR cut points were 20.7 and 16.3 microU/ml, respectively. This rule had a sensitivity and specificity of 84.9 and 78.7%, respectively. The second model, which included clinical measurements but no laboratory determinations, had an aROC of 85.0% and generated a decision rule that had a sensitivity and specificity of 78.7 and 79.6%, respectively. The third model, which included clinical measurements and lipid measurements but not insulin (and thus excluded HOMA-IR as well), had a similar aROC (85.1%), sensitivity (81.3%), and specificity (76.3%). Thus, insulin-resistant individuals can be identified using simple decision rules that can be tailored to specific needs.

The nature of the progressive beta-cell failure occurring as normal glucose tolerant (NGT) individuals progress to type 2 diabetes (T2DM) is incompletely understood. We measured insulin sensitivity (by a euglycemic insulin clamp) and insulin secretion rate (by deconvolution of plasma C-peptide levels during an oral glucose tolerance test) in 188 subjects [19 lean NGT (body mass index [BMI]

Fasting plasma glucose concentrations (FPG) predict development of type 2 diabetes. Whether hyperglycemia evolves from normoglycemia gradually over time or as a step increase is not known. We measured plasma glucose and insulin levels during oral glucose testing in 35- to 64-year-old men and nonpregnant women from a population-based survey (Mexico City Diabetes Study) at baseline (n = 2,279) and after 3.25 (n = 1,740) and 7 years (n = 1,711) of follow-up. In subjects with normal glucose tolerance (NGT) on all three occasions (nonconverters; n = 911), FPG increased only slightly (0.23 +/- 0.79 mmol/l, mean +/- SD; P < 0.0001) over 7 years. In contrast, conversion to diabetes among NGT subjects (n = 98) was marked by a large step-up in FPG regardless of time of conversion (3.06 +/- 2.57 and 2.94 +/- 3.11 mmol/l, respectively, at 3.25 and 7 years; P < 0.0001 vs. nonconverters). Likewise, in subjects who converted to diabetes from impaired glucose tolerance (n = 75), FPG rose by 3.14 +/- 3.83 and 3.12 +/- 3.61 mmol/l (P < 0.0001 vs. nonconverters). Three-quarters of converters had increments in FPG above the 90th percentile of the corresponding increments in nonconverters. Converters had higher baseline BMI (30.4 +/- 4.9 vs. 27.3 +/- 4.0 kg/m(2); P < 0.001) and fasting plasma insulin values (120 +/- 78 vs. 84 +/- 84 pmol/l; P < 0.02) than nonconverters; however, no consistent change in either parameter had occurred before conversion. In contrast, changes in 2-h postglucose insulin levels between time of conversion and preceding measurement were significantly (P < 0.0001) related to the corresponding changes in FPG in an inverse manner. We conclude that, within a 3-year time frame, the onset of diabetes is very often rapid rather than gradual and is in part explained by a fall in glucose-stimulated insulin response.

Objective: Impaired insulin-mediated hepatic glucose uptake (HGU) has been implicated in the hyperglycemia of type 2 diabetes. We examined the effects of metformin (2 g/day) and rosiglitazone (8 mg/day) monotherapy on HGU and its relation to subcutaneous fat, visceral fat (VF), and whole-body insulin-mediated glucose metabolism in type 2 diabetic patients., Research Design and Methods: Glucose uptake was measured before and after 26 weeks of treatment using positron emission tomography with [(18)F]2-fluoro-2-deoxyglucose during euglycemic hyperinsulinemia; fat depots were quantified by magnetic resonance imaging., Results: Fasting plasma glucose levels were significantly decreased after either rosiglitazone (-0.9 +/- 0.5 mmol/l) or metformin treatment (-1.1 +/- 0.5 mmol/l) in comparison with placebo; only metformin was associated with weight loss (P < 0.02 vs. placebo). When controlling for the latter, the placebo-subtracted change in whole-body glucose uptake averaged -1 +/- 4 micromol x min(-1) x kg(-1) in metformin-treated patients (NS) and +9 +/- 3 micromol x min(-1) x kg(-1) in rosiglitazone-treated patients (P = 0.01). Both rosiglitazone and metformin treatment were associated with an increase in HGU; versus placebo, the change reached statistical significance when controlling for sex (placebo-subtracted values = +0.008 +/- 0.004 micromol x min(-1) x kg(-1) x pmol/l(-1), P < 0.03, for metformin; and +0.007 +/- 0.004, P < 0.07, for rosiglitazone). After treatment with either drug, insulin-mediated VF glucose uptake (VFGU) was higher than with placebo. In the whole dataset, changes in HGU were negatively related to changes in HbA(1c) (r = 0.43, P = 0.01) and positively associated with changes in VFGU (r = 0.48, P < 0.01)., Conclusions: We conclude that both metformin and rosiglitazone monotherapy increase HGU in type 2 diabetes; direct drug actions, better glycemic control, and enhanced VF insulin sensitivity are likely determinants of this phenomenon.

Impaired hepatic glucose uptake (HGU) has been implicated in the development of hyperglycemia in type 2 diabetes; the relative impact of plasma glucose and insulin levels on this process remains controversial. We compared the effects of euglycemic hyperinsulinemia on HGU, skeletal muscle glucose uptake, and hepatic influx rate-constant (H-Ki) in 38 diet-treated diabetic patients and 22 nondiabetic controls, using positron emission tomography with (18)F-fluorodeoxyglucose and the insulin clamp technique. Control subjects were divided into two subgroups: one including older, heavier, insulin-resistant controls (whole-body glucose uptake, M = 21.4 +/- 5.4 micromol x min(-1) x kg(-1)) to match characteristics of diabetic patients (M = 20.4 +/- 9.9); the other including younger, leaner, insulin-sensitive controls (M = 48.2 +/- 9.9, P < 0.01). Skeletal muscle glucose uptake showed a similar group distribution as the M value. Insulin clearance rates were lower, whereas glycosylated hemoglobin and clamp plasma insulin levels were higher in diabetic patients than in controls. HGU and H-Ki were similar in the two nondiabetic subgroups and lower in diabetic patients than in controls (1.9 +/- 0.5 vs. 2.3 +/- 0.7 micromol x min(-1) x 100 ml(-1), and 0.37 +/- 0.09 vs. 0.44 +/- 0.14 ml x min(-1) x 100 ml(-1), P < or = 0.01). In the whole dataset, H-Ki was inversely related to fasting plasma glucose (correlation coefficient = -0.40, P = 0.0018). In diabetic subjects, H-Ki was reciprocally related to glycosylated hemoglobin (correlation coefficient = -0.36, P = 0.029). We conclude that insulin-mediated HGU is impaired, in type 2 diabetes, in some proportion to the degree of glycemic control.

Visceral fat (VF) excess has been associated with decreased peripheral insulin sensitivity and has been suggested to contribute to hepatic insulin resistance. However, the mechanisms by which VF impacts on hepatic glucose metabolism and the quantitative role of VF in glycemic control have not been investigated. In the present study 63 type 2 diabetic subjects (age, 55 +/- 1 yr; fasting plasma glucose, 5.5-14.4 mmol/liter; hemoglobin A(1c), 6.1-11.7%) underwent measurement of 1) fat-free mass ((3)H(2)O technique), 2) sc and visceral abdominal fat area (magnetic resonance imaging), 3) insulin sensitivity (euglycemic insulin clamp), 4) endogenous glucose output ([(3)H]glucose infusion technique), and 5) gluconeogenesis ((2)H(2)O method). After adjustment for sex, age, body mass index, diabetes duration, ethnicity, and sc fat area, VF area was positively related to fasting hyperglycemia (partial r = 0.46; P = 0.001) as well as to hemoglobin A(1c) (partial r = 0.50; P = 0.0003). Insulin sensitivity was reciprocally related to VF independently of body mass index (partial r = 0.33; P = 0.01). In contrast, the relation of basal endogenous glucose output to VF was not statistically significant. This lack of association was explained by the fact that VF was positively associated with gluconeogenesis flux (confounder-adjusted, partial r = 0.45; P = 0.003), but was reciprocally associated with glycogenolysis (partial r = 0.31; P < 0.05). We conclude that in patients with established type 2 diabetes, VF accumulation has a significant negative impact on glycemic control through a decrease in peripheral insulin sensitivity and an enhancement of gluconeogenesis.

Aims/hypothesis: We investigated the effect of physiological hyperinsulinaemia on global and regional myocardial blood flow and glucose uptake in five patients with Type II (non-insulin-dependent) diabetes mellitus and seven healthy control subjects., Methods: Myocardial blood flow was assessed by positron emission tomography with oxygen-15 labelled water (H(2)(15)O) either before or after 1 h of euglycaemic hyperinsulinaemia. Myocardial glucose uptake was assessed by positron emission tomography and fluorine-18 labelled fluorodeoxyglucose ((18)FDG)., Results: During hyperinsulinaemia, myocardial blood flow increased from 0.91+/-0.03 to 1.00+/-0.03 ml(.)min(-1.)g(-1) in control subjects ( p<0.005) and from 0.81+/-0.02 to 0.95+/-0.04 ml(.)min(-1.)g(-1) in diabetic patients ( p<0.0005). Corresponding glucose uptakes were 0.56+/-0.01 and 0.36+/-0.02 micro mol(.)min(-1.)g(-1) ( p<0.0001), respectively. During hyperinsulinaemia, the regional distribution of myocardial blood flow and glucose uptake showed higher values in the septum and anterolateral wall (short axis) and in the mid-ventricle (long axis) in control subjects, and insulin action was circumscribed to these regions. In diabetic patients, the regional distribution of glucose uptake was similar; however, insulin-induced increase of myocardial blood flow was mainly directed to the postero-inferior areas (short axis) and to the base (long axis) of the heart, thus cancelling the predominance of the anterior wall observed before insulin administration., Conclusion/interpretation: These results provide evidence that insulin-mediated regulation of global myocardial blood flow is preserved in Type II diabetic patients. In contrast, the regional re-distribution of myocardial blood flow induced by insulin is directed to different target areas when compared with healthy subjects, thereby resulting in a mismatch between blood flow and glucose metabolism.

Objective: To elucidate the effects of pioglitazone treatment on glucose and lipid metabolism in patients with type 2 diabetes., Research Design and Methods: A total of 23 diabetic patients (age 30-70 years BMI < 36 kg/m2) who being treated with a stable dose of sulfonylurea were randomly assigned to receive either placebo (n = 11) or pioglitazone (45 mg/day) (n = 12) for 16 weeks. Before and after 16 weeks of treatment, all subjects received a 75-g oral glucose tolerance test (OGTT) and hepatic peripheral insulin sensitivity was measured with a two-step euglycemic insulin (40 and 160 mU x min(-1) x m(-2) clamp performed with 3-[3H]glucose and indirect calorimetry HbA1c measured monthly throughout the study period., Results: After 16 weeks of pioglitazone treatment, the fasting plasma glucose (FPG; 184 +/- 15 to 135 +/- 11 mg/dl, P < 0.01), mean plasma glucose during OGTT(293 +/- 12 to 225 +/- 14 mg/dl, P < 0.01), and HbA1c (8.9 +/- 0.3 to 7.2 +/- 0.5%, P < 0.01 ) decreased significantly without change in fasting or glucose-stimulated insulin/C-peptide concentrations. Fasting plasma free fatty acid (FFA; 647 +/- 39 to 478 +/- 49) microEq/l, P < 0.01) and mean plasma FFA during OGTT (485 +/- 30 to 347 +/- 33 microEq/l, P < 0.01) decreased significantly after pioglitazone treatment. Before and after pioglitazone treatment, basal endogenous glucose prodution (EGP) and FPG were strongly correlated (r = 0.67, P < 0.01). EGP during the first insulin clamp step was significantly decreased after pioglitazone treatment (P < 0.05) whereas insulin-stimulated total and nonoxidative glucose disposal during the second insulin clamp was increased (P < 0.01). The change in FPG was related to the change in basal EGP, EGP during the first insulin clamp step, and total glucose disposal during the second insulin clamp step. The change in mean plasma glucose concentration during the OGGTT was strongly related to the change in total body glucose disposl during the second insulin clamp step., Conclusions: These results suggest that pioglitazone therapy in type 2 diabetic patients decreases lasting and postprandial plasma glucose levels by improving hepatic and peripheral (muscle) tissue sensitivity to insulin.

The aim of this work was to develop a mathematical model describing the functional dependence of insulin secretion on plasma glucose concentrations during 24 h of free living. We obtained hourly central venous blood samples from a group of healthy volunteers who spent 24 h in a calorimetric chamber, where they consumed standardized meals. Insulin secretory rates were reconstructed from plasma C-peptide concentrations by deconvolution. The relationship between insulin release and plasma glucose concentrations was modeled as the sum of three components: a static component (describing the dependence on plasma glucose concentration itself, with an embedded circadian oscillation), a dynamic component (modeling the dependence on glucose rate of change), and a residual component (including the fraction of insulin secretion not explained by glucose levels). The model fit of the individual 24-h secretion profiles was satisfactory (within the assigned experimental error of glucose and C-peptide concentrations). The static component yielded a dose-response function in which insulin release increased quasi-linearly (from 40 to 400 pmol/min on average) over the range of 4-9 mmol/l glucose. The dynamic component was significantly different from zero in coincidence with meal-related glucose excursions. The circadian oscillation and the residual component accounted for the day/night difference in the ability of glucose to stimulate insulin release. Over 24 h, total insulin release averaged 257+/-58 nmol (or 43+/-10 U). The static and dynamic component together accounted for approximately 80% of total insulin release. The model proposed here provides a detailed robust description of glucose-related insulin release during free-living conditions. In nondiabetic subjects, non-glucose-dependent insulin release is a small fraction of total insulin secretion.

In 9 patients with essential hypertension, we tested whether a high-dose (12 mg. min(-1)) vitamin C infusion into the brachial artery, by improving endothelium-dependent vasodilatation, would also attenuate the insulin resistance of deep forearm tissues. We measured the effect of vitamin C on acetylcholine (Ach)-induced vasodilatation and on forearm glucose uptake during systemic hyperinsulinemia; in all studies, the contralateral forearm served as the control. Intrabrachial Ach infusion produced a stable increase in forearm blood flow, from 2.6+/-0.3 to 10.6+/-2.1 mL. min(-1). dL(-1); when vitamin C was added, a further rise in forearm blood flow (to 13.4 mL. min(-1). dL(-1); P<0.03 vs Ach alone) was observed. In response to insulin, blood flow in both the infused and control forearms did not significantly change from baseline values (+10+/-16% and +2+/-11%, respectively). In contrast, when vitamin C was added, blood flow in the infused forearm increased significantly (to 3.7+/-0.7 mL. min(-1). dL(-1); P<0.02 vs 2.8+/-0.6 mL. min(-1). dL(-1) in the control forearm). Insulin stimulated whole-body glucose disposal to 20+/-2 micromol. min(-1). kg(-1), compatible with the presence of marked insulin resistance. Forearm glucose uptake was similarly stimulated after 80 minutes of insulin infusion (to 2.11+/-0.42 and 2.06+/-0.43 micromol. min(-1). dL(-1), infused and control, respectively). When intrabrachial vitamin C was added, no difference in glucose uptake was observed between the 2 forearms (infused, 2.37+/-0.44 micromol. min(-1). dL(-1)and control, 2.36+/-0. 53 micromol. min(-1). dL(-1)). Forearm O(2) uptake at baseline was also similar in the 2 forearms (infused, 9.7+/-0.7 micromol. min(-1). dL(-1) and control, 9.6+/-1.1 micromol. min(-1). dL(-1)) and was not changed by either insulin or vitamin C. We conclude that in the deep forearm tissues of patients with essential hypertension and insulin resistance, an acute improvement in endothelial function, obtained with pharmacological doses of vitamin C, restores insulin-mediated vasodilatation but does not improve insulin-mediated glucose uptake. Thus, the endothelial dysfunction of essential hypertension is unlikely to be responsible for their metabolic insulin resistance.

The traditional methods for the assessment of insulin sensitivity yield only a single index, not the whole dose-response curve information. This curve is typically characterized by a maximally insulin-stimulated glucose clearance (Cl(max)) and an insulin concentration at half-maximal response (EC(50)). We developed an approach for estimating the whole dose-response curve with a single in vivo test, based on the use of tracer glucose and exogenous insulin administration (two steps of 20 and 200 mU x min(-1) x m(-2), 100 min each). The effect of insulin on plasma glucose clearance was calculated from non-steady-state data by use of a circulatory model of glucose kinetics and a model of insulin action in which glucose clearance is represented as a Michaelis-Menten function of insulin concentration with a delay (t(1/2)). In seven nondiabetic subjects, the model predicted adequately the tracer concentration: the model residuals were unbiased, and their coefficient of variation was similar to the expected measurement error (approximately 3%), indicating that the model did not introduce significant systematic errors. Lean (n = 4) and obese (n = 3) subjects had similar half-times for insulin action (t(1/2) = 25 +/- 9 vs. 25 +/- 8 min) and maximal responses (Cl(max) = 705 +/- 46 vs. 668 +/- 259 ml x min(-1) x m(-2), respectively), whereas EC(50) was 240 +/- 84 microU/ml in the lean vs. 364 +/- 229 microU/ml in the obese (P < 0.04). EC(50) and the insulin sensitivity index (ISI, initial slope of the dose-response curve), but not Cl(max), were related to body adiposity and fat distribution with r of 0.6-0.8 (P < 0.05). Thus, despite the small number of study subjects, we were able to reproduce information consistent with the literature. In addition, among the lean individuals, t(1/2) was positively related to the ISI (r = 0.72, P < 0.02). We conclude that the test here presented, based on a more elaborate representation of glucose kinetics and insulin action, allows a reliable quantitation of the insulin dose-response curve for whole body glucose utilization in a single session of relatively short duration.

We tested whether acute alpha 2-blockade affects insulin secretion, glucose and fat metabolism, thermogenesis, and hemodynamics in humans. During a 5-h epinephrine infusion (50 ng.min-1.kg-1) in five volunteers, deriglidole, a selective alpha 2-receptor inhibitor, led to a more sustained rise in plasma insulin and C-peptide levels (+59 +/- 14 vs. +28 +/- 6, and +273 +/- 18 vs. +53 +/- 14 pM, P < 0.01 vs. placebo) despite a smaller rise in plasma glucose (+0.90 +/- 0.4 vs. +1.5 +/- 0.3 mM, P < 0.01). Another 10 subjects were studied in the postabsorptive state and during a 4-h hyperglycemic (+4 mM) clamp, coupled with the ingestion of 75 g of glucose at 2 h. In the postabsorptive state, hepatic glucose production, resting energy expenditure, and plasma insulin, free fatty acid (FFA), and potassium concentrations were not affected by acute alpha 2-blockade. Hyperglycemia elicited a biphasic rise in plasma insulin (to a peak of 140 +/- 24 pM), C-peptide levels (1,520 +/- 344 pM), and insulin secretion (to 410 +/- 22 pmol/min); superimposed glucose ingestion elicited a further twofold rise in insulin and C-peptide levels, and insulin secretion. However, alpha 2-blockade failed to change these secretory responses. Fasting blood beta-hydroxybutyrate and glycerol and plasma FFA and potassium concentrations all declined with hyperglycemia; time course and extent of these changes were not affected by alpha 2-blockade. Resting energy expenditure (+25 vs. +16%, P < 0.01) and external cardiac work (+28% vs. +19%, P < 0.01) showed larger increments after alpha 2-blockade. We conclude that acute alpha 2-blockade in humans 1) prevents epinephrine-induced inhibition of insulin secretion, 2) does not potentiate basal or intravenous- or oral glucose-induced insulin release, 3) enhances thermogenesis, and 4) increases cardiac work.

The study of blood-tissue exchange by the multiple indicator dilution technique often needs frequent sampling in the blood of the indicator dilution curves (IDC). Usually, this requires the use of a catheter supported by a pump. This causes a distortion in the IDC, which must be removed for proper interpretation of the data. A deconvolution-based methodology to remove IDC distortion is presented. First, the catheter impulse response is modelled by means of data obtained from a suitable experiment. Then the reconstruction of the blood IDC is tackled by a new nonparametric deconvolution algorithm, which provides (quasi) time-continuous signals and exploits statistically based criteria for the choice of the regularisation parameter. The methodology is applied to the removal of catheter distortion in studies of glucose blood-tissue exchange in the human forearm and myocardium.

Pharmacological treatment of hyperlipidemia may be associated with deterioration of glucose tolerance. We randomized 20 nonobese patients with primary familial hypercholesterolemia (serum total cholesterol 7.8 +/- 0.4 mM, triglycerides 1.4 +/- 0.2 mM) to an isocaloric, reduced fat (< 30%) low-cholesterol (200 mg/day) diet with placebo or pravastatin (40 mg/day). Oral glucose tolerance, endogenous insulin response to glucose, insulin sensitivity (determined by the euglycemic insulin clamp technique), hepatic glucose production (by the tritiated glucose technique), and substrate utilization (by indirect calorimetry) were measured at baseline and after 8 weeks of treatment. Ten normocholesterolemic healthy subjects, matched to the patients by age, sex, and body weight, served as the control group. Diet alone (with no change in body weight) was associated with a significant 15% decrease in both serum low density lipoprotein (LDL)-cholesterol and triglycerides (p < 0.001 for both), and a slight decrease in high density lipoprotein (HDL)-cholesterol concentrations, paralleled by reductions in Apo B, C2, C3, and E levels (p < 0.05 or less). The addition of pravastatin led to a significantly larger reduction in LDL-cholesterol (30%, p < 0.05) and an 8% increase (p < 0.02) in total HDL-cholesterol concentrations. Accordingly, the ratio of LDL:HDL cholesterol (which was 60% higher than in controls at baseline) remained unchanged in the placebo-diet group whereas it was restored to normal in the pravastatin-diet group. Glucose tolerance, insulin response, insulin-induced inhibition of hepatic glucose production and lipolysis, and insulin-mediated glucose uptake and oxidation were all slightly but not significantly improved after treatment, with no significant differences between pravastatin and placebo. In nonobese patients with primary hypercholesterolemia, pravastatin treatment in combination with an isocaloric, reduced-fat diet leads to a marked reduction in LDL-cholesterol and triglycerides levels and a normalization of the LDL:HDL ratio without affecting glucose tolerance or insulin sensitivity.

Evidence that age is associated with insulin resistance is discordant. We analyzed euglycemic insulin clamp (1 mU x min(-1) x kg(-1)) data collected at 20 centers throughout Europe from 1,146 men and women with normal glucose tolerance, ranging in age from 18 to 85 years. In the whole group, insulin action (as the M value) declined slightly with age (at a rate of 0.9 micromol x min(-1)-kg(-1) per decade of life, 95% CI = 0.4-1.3, P = 0.0002). When adjusted for BMI, this relationship was no longer statistically significant. The same result was obtained whether insulin action was expressed per kilogram of body weight or per kilogram of fat-free mass, expressed as the M:I ratio, or estimated from fasting plasma insulin concentrations. Subgroup analysis showed that a significant BMI-adjusted decrease in insulin action with age was present only in lean (BMI <25 kg/m2) women (a rate of 1.6 micromol x min(-1) x kg(-1) per decade, 95% CI = 0.6-2.5, P = 0.001), in whom percentage fat mass also increased with age (by 0.38% body weight per decade, P = 0.0007). Insulin action was positively associated with insulin suppression of circulating free fatty acids (FFAs) (+1.5 micromol x min(-1) x kg(-1) for each 10% increase in FFA suppression, P < 0.0001) in a multivariate model accounting for sex, BMI, age, and fasting FFA levels. Furthermore, insulin suppression of FFAs improved with age in men (2% per decade, P < 0.0001) but not in women. In the subgroup of lean women in whom insulin action declined with age, adding FFA suppression to a multiple regression equation canceled the association between age and insulin action. Thus, the small effect of age on insulin action could be adequately explained on the basis of age-related changes in body composition and substrate competition. We conclude that in healthy Europeans, age per se is not a significant cause of insulin resistance of glucose metabolism or lipolysis.

Essential hypertension is associated with insulin resistance and hyperinsulinemia. To assess whether hyperinsulinemia is also present in hypertensive disease induced by pregnancy, we studied the plasma glucose and insulin responses to 50 g of oral glucose in 10 women with definite, severe preeclampsia but normal glucose tolerance, and compared them with the responses observed in a well-matched control group of healthy pregnant women. Fasting plasma glucose concentrations were similar in healthy and preeclamptic pregnant mothers (4.1 +/- 0.4 mmol/L v 4.5 +/- 0.4 mmol/L, respectively, P = NS). Similar plasma glucose levels were also observed after glucose ingestion (5.5 +/- 0.3 mmol/L v 6.2 +/- 0.3 mmol/L in healthy and preeclamptic women, respectively P = NS). In contrast, fasting plasma insulin concentrations in the preeclamptic women were significantly higher than in normal pregnant mothers (175 +/- 29 pmol/L v 101 +/- 11 pmol/L, P < .05). Postload plasma insulin concentrations were nearly fourfold higher in the preeclamptic group as compared with the control group (1162 +/- 70 pmol/L v 366 +/- 39 pmol/L, P < .01). We conclude that preeclampsia is associated with marked hyperinsulinemia both in the fasting state and after oral glucose ingestion, suggesting that insulin resistance may play a role in pregnancy-induced hypertension.

Both whole-body models and the regional arteriovenous (AV)-difference method have been used to calculate systemic glucose rates of appearance (Ras) under non-steady-state conditions. Although whole-body models have been experimentally validated in the dog, direct comparison of the whole-body and regional-balance approach has not been made in man. We reanalyzed published data obtained by combining the double-tracer technique ([3H]glucose infusion with ingestion of a [14C]glucose-labeled load) with hepatic vein catheterization. Steele's monocompartmental model underestimated the Ra of oral glucose ([RaO] by 12%, P < .0001) and overestimated the Ra of endogenous glucose ([RaE] by 19%, P < .0001) in comparison to a two-compartment (2-c) model calculation. Splanchnic balance data were used to compute the total glucose Ra (RaT) with either steady-state or non-steady-state equations (the latter by estimating splanchnic transit times). Except for one early time point (15 minutes), the two calculations agreed well with one another. The glucose RaT by the balance method was well correlated with that calculated by the 2-c whole-body model (r = .72, P < .0001 on all data points); however, the former significantly underestimated the latter by 0.62 mg.min-1.kg-1 (or 13%, P < .01) on average throughout the absorptive period. This bias was small in comparison to the estimated random error affecting the calculation of glucose RaT by the model, which averaged 1.4 mg.min-1.kg-1 (corresponding to a variation coefficient of approximately 30%).(ABSTRACT TRUNCATED AT 250 WORDS)

To establish the antihyperglycemic mechanisms of metformin in non-insulin-dependent diabetes mellitus (NIDDM) independently of the long-term, aspecific effects of removal of glucotoxicity, 21 NIDDM subjects (14 obese, 7 nonobese) were studied on two separate occasions, with an isoglycemic (plasma glucose approximately 9 mM) hyperinsulinemic (two-step insulin infusion, 2 h each, at the rate of 4 and 40 mU.m-2.min-1) clamp combined with [3-3H]glucose infusion and indirect calorimetry, after administration of either metformin (500 mg per os, at -5 and -1 h before the clamp) or placebo. Compared with placebo, hepatic glucose production (HGP) decreased approximately 30% more after metformin (from 469 +/- 50 to 330 +/- 54 mumol/min), but glucose uptake did not increase. Metformin suppressed free fatty acids (FFAs) by approximately 17% (from 0.42 +/- 0.04 to 0.35 +/- 0.04 mM) and lipid oxidation by approximately 25% (from 4.5 +/- 0.4 to 3.4 +/- 0.4 mumol.kg-1.min-1) and increased glucose oxidation by approximately 16% (from 16.2 +/- 1.4 to 19.3 +/- 1.3 mumol.kg-1.min-1) compared with placebo (P < 0.05), but did not affect nonoxidative glucose metabolism, protein oxidation, or total energy expenditure. Suppression of FFA and lipid oxidation after metformin correlated with suppression of HGP (r = 0.70 and r = 0.51, P < 0.001). The effects of metformin in obese and nonobese subjects were no different. We conclude that the specific, antihyperglycemic effects of metformin in the clinical condition of hyperglycemia in NIDDM are primarily due to suppression of HGP, not stimulation of glucose uptake, and are mediated, at least in part, by suppression of FFA and lipid oxidation.