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Context: Studies in rodents and humans suggest that high-fructose corn syrup (HFCS)-sweetened diets promote greater metabolic dysfunction than sucrose-sweetened diets., Objective: To compare the effects of consuming sucrose-sweetened beverage (SB), HFCS-SB, or a control beverage sweetened with aspartame on metabolic outcomes in humans., Methods: A parallel, double-blinded, NIH-funded study. Experimental procedures were conducted during 3.5 days of inpatient residence with controlled feeding at a research clinic before (baseline) and after a 12-day outpatient intervention period. Seventy-five adults (18-40 years) were assigned to beverage groups matched for sex, body mass index (18-35 kg/m2), and fasting triglyceride, lipoprotein and insulin concentrations. The intervention was 3 servings/day of sucrose- or HFCS-SB providing 25% of energy requirement or aspartame-SB, consumed for 16 days. Main outcome measures were %hepatic lipid, Matsuda insulin sensitivity index (ISI), and Predicted M ISI., Results: Sucrose-SB increased %hepatic lipid (absolute change: 0.6 ± 0.2%) compared with aspartame-SB (-0.2 ± 0.2%, P < 0.05) and compared with baseline (P < 0.001). HFCS-SB increased %hepatic lipid compared with baseline (0.4 ± 0.2%, P < 0.05). Compared with aspartame-SB, Matsuda ISI decreased after consumption of HFCS- (P < 0.01) and sucrose-SB (P < 0.01), and Predicted M ISI decreased after consumption of HFCS-SB (P < 0.05). Sucrose- and HFCS-SB increased plasma concentrations of lipids, lipoproteins, and uric acid compared with aspartame-SB. No outcomes were differentially affected by sucrose- compared with HFCS-SB. Beverage group effects remained significant when analyses were adjusted for changes in body weight., Conclusion: Consumption of both sucrose- and HFCS-SB induced detrimental changes in hepatic lipid, insulin sensitivity, and circulating lipids, lipoproteins and uric acid in 2 weeks., (© The Author(s) 2021. Published by Oxford University Press on behalf of the Endocrine Society.)

Objectives: Urinary tract involvement is a seldom-reported manifestation of SSc that could compromise patients' quality of life. This study compares lower urinary tract symptoms (LUTS) in SSc patients and in healthy subjects and their association with clinical and diagnostic parameters., Methods: LUTS were assessed through self-reported questionnaires in 42 SSc patients and 50 matched healthy subjects. Statistical analyses were performed to explore LUTS in the two populations and their association with SSc variables, including nailfold videocapillaroscopy patterns, SSc-related antibodies and DXA parameters., Results: SSc patients showed significantly higher prevalence and severity of urinary incontinence (UI) and overactive bladder (OAB) than healthy controls (P < 0.005, P < 0.01). SSc was a strong predictor of LUTS, independent of demographic data, comorbidities and treatments (odds ratio 5.57, 95% CI 1.64-18.88). In SSc patients OAB positively correlated with sarcopenia (P < 0.001), and both OAB and UI significantly correlated with reduced BMD (P < 0.05, P = 0.001). UI positively correlated with Scl70 antibodies (P < 0.05) and ciclosporin treatment (P = 0.001) and negatively with RNA polymerase III antibodies (P < 0.05); OAB positively correlated with calcinosis (P < 0.005) and negatively with methotrexate treatment (P < 0.05). Nailfold videocapillaroscopy 'active' and 'late' patterns were predominant among SSc patients presenting urinary symptoms, although no statistical correlation was found., Conclusion: For the first time urinary tract involvement was found to be significantly higher in SSc patients than in healthy matched controls. In addition, sarcopenia, bone damage and calcinosis appeared significantly correlated with LUTS, suggesting a possible interplay., (© The Author(s) 2019. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Objective: The aim of this observational study was to investigate the evolution of scleroderma microangiopathy throughout different nailfold videocapillaroscopy (NVC) patterns ('early', 'active', 'late') as well as the prevalence of organ involvement in SSc patients during a 12-year follow-up., Methods: Thirty-four SSc patients showing at baseline (first capillaroscopic analysis) the 'early' NVC pattern of microangiopathy were enrolled and followed for 12 years (s.d. 2). Complete NVC analysis and clinical and serological findings were collected. Patients were in a standard therapeutic care setting. Statistical analysis was carried out by non-parametric tests., Results: After a 12-year follow-up, the 'early' NVC pattern changed from baseline in 76% of the patients. The NVC pattern was found to be 'active' in 9 patients (26%), 'late' in 13 (38%) and characterized by non-specific capillary abnormalities in 4 (12%). In the subgroup whose microangiopathy progressed from the 'early' to the 'late' NVC pattern, the median time of progression from the 'early' to the 'active' pattern was significantly shorter (11 months) when compared with patients who progressed from the 'early' to the 'active' NVC pattern (55 months) (P = 0.002). The median time of progression between NVC patterns was significantly shorter in SSc patients showing either a nucleolar ANA pattern or Scl70 autoantibodies (P = 0.048). Organ involvement was progressively greater in SSc patients with 'early', 'active' and 'late' NVC patterns, respectively., Conclusions: This longitudinal study confirms over a 12-year follow-up the evolution of specific NVC patterns associated with the progressive severity of organ involvement in SSc patients in a standard clinical care setting., (© The Author(s) 2019. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Objective: Hepatic energy metabolism negatively relates to insulin resistance and liver fat content in patients with type 2 diabetes, but its role in metabolically healthy humans is unclear. We hypothesized that intrahepatocellular γ-adenosine triphosphate (γATP) and inorganic phosphate (Pi) concentrations exhibit similar associations with insulin sensitivity in nondiabetic, nonobese volunteers., Design: A total of 76 participants underwent a four-point sampling, 75-g oral glucose tolerance test (OGTT), as well as in vivo31P/1H magnetic resonance spectroscopy. In 62 of them, targeted plasma metabolomic profiling was performed. Pearson correlation analyses were performed for the dependent variables γATP and Pi., Results: Adjusted for age, sex, and body mass index (BMI), hepatic γATP and Pi related to 2-hour OGTT glucose (r = 0.25 and r = 0.27, both P < 0.05), and Pi further associated with nonesterified fatty acids (NEFAs; r = 0.28, P < 0.05). However, neither γATP nor Pi correlated with several measures of insulin sensitivity. Hepatic γATP correlated with circulating leucine (r = 0.42, P < 0.001) and Pi with C16:1 fatty acids palmitoleic acid and C16:1w5 (r = 0.28 and 0.30, respectively, P < 0.01), as well as with δ-9-desaturase index (r = 0.33, P < 0.05). Only the association of γATP with leucine remained important after correction for multiple testing. Leucine and palmitoleic acid, together with age, sex, and BMI, accounted for 26% and for 15% of the variabilities in γATP and Pi, respectively., Conclusions: Specific circulating amino acids and NEFAs, but not measures of insulin sensitivity, partly affect hepatic phosphorus metabolites, suggesting mutual interaction between hepatic energy metabolism and circulating metabolites in nondiabetic humans., (Copyright © 2017 Endocrine Society)

The steep rise of type 2 diabetes mellitus (T2DM) and associated complications go along with mounting evidence of clinically important sex and gender differences. T2DM is more frequently diagnosed at lower age and body mass index in men; however, the most prominent risk factor, which is obesity, is more common in women. Generally, large sex-ratio differences across countries are observed. Diversities in biology, culture, lifestyle, environment, and socioeconomic status impact differences between males and females in predisposition, development, and clinical presentation. Genetic effects and epigenetic mechanisms, nutritional factors and sedentary lifestyle affect risk and complications differently in both sexes. Furthermore, sex hormones have a great impact on energy metabolism, body composition, vascular function, and inflammatory responses. Thus, endocrine imbalances relate to unfavorable cardiometabolic traits, observable in women with androgen excess or men with hypogonadism. Both biological and psychosocial factors are responsible for sex and gender differences in diabetes risk and outcome. Overall, psychosocial stress appears to have greater impact on women rather than on men. In addition, women have greater increases of cardiovascular risk, myocardial infarction, and stroke mortality than men, compared with nondiabetic subjects. However, when dialysis therapy is initiated, mortality is comparable in both males and females. Diabetes appears to attenuate the protective effect of the female sex in the development of cardiac diseases and nephropathy. Endocrine and behavioral factors are involved in gender inequalities and affect the outcome. More research regarding sex-dimorphic pathophysiological mechanisms of T2DM and its complications could contribute to more personalized diabetes care in the future and would thus promote more awareness in terms of sex- and gender-specific risk factors.

Context: Insulin resistance reflects the inadequate insulin-mediated use of metabolites and predicts type 2 diabetes (T2D) but is also frequently seen in long-standing type 1 diabetes (T1D) and represents a major cardiovascular risk factor., Objective: We hypothesized that plasma metabolome profiles allow the identification of unique and common early biomarkers of insulin resistance in both diabetes types., Design, Setting, and Patients: Two hundred ninety-five plasma metabolites were analyzed by mass spectrometry from patients of the prospective observational German Diabetes Study with T2D (n = 244) or T1D (n = 127) and known diabetes duration of less than 1 year and glucose-tolerant persons (CON; n = 129). Abundance of metabolites was tested for association with insulin sensitivity as assessed by hyperinsulinemic-euglycemic clamps and related metabolic phenotypes., Main Outcomes Measures: Sixty-two metabolites with phenotype-specific patterns were identified using age, sex, and body mass index as covariates., Results: Compared with CON, the metabolome of T2D and T1D showed similar alterations in various phosphatidylcholine species and amino acids. Only T2D exhibited differences in free fatty acids compared with CON. Pairwise comparison of metabolites revealed alterations of 28 and 49 metabolites in T1D and T2D, respectively, when compared with CON. Eleven metabolites allowed differentiation between both diabetes types and alanine, α-amino-adipic acid, isoleucin, and stearic acid showed an inverse association with insulin sensitivity in both T2D and T1D combined., Conclusion: Metabolome analyses from recent-onset T2D and T1D patients enables identification of defined diabetes type-specific differences and detection of biomarkers of insulin sensitivity. These analyses may help to identify novel clinical subphenotypes diabetes.

Context: The incretin effect is the augmented insulin secretion by oral vs iv glucose at matching glucose levels. We previously demonstrated an augmented insulin secretion when fat is given orally rather than iv, suggesting an incretin effect also after fat. However, whether an incretin effect is also present after amino acid ingestion is not known., Objective: The objective of the study was to explore insulin secretion and incretin hormones after oral and iv amino acid administration at matched total amino acid concentrations in healthy subjects., Design: An amino acid mixture (Vaminolac) was administered orally or iv at a rate resulting in matching total amino acid concentrations to 12 male volunteers with age 22.5 ± 1.4 years and a body mass index 22.4 ± 1.4 kg/m(2), who had no history of diabetes., Main Outcome Measures: Main outcome measures were area under the 120-minute curve for insulin, C-peptide, glucagon, intact and total glucagon like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), and the insulin secretory rate and insulin clearance., Results: Insulin, C-peptide, and glucagon levels increased after both oral and iv administration, but insulin secretion was 25% higher after oral than after iv amino acid challenges (P = .006), whereas there was no significant difference in the glucagon response. Intact and total GIP rose after oral but not after iv amino acid administration, whereas intact and total GLP-1 levels did not change significantly in either test., Conclusion: Oral amino acid mixture ingestion elicits a stronger insulin secretory response than iv amino acid at matching amino acid levels and this is associated with increased GIP level, suggesting that an incretin effect exists also after oral amino acids, possibly mediated by GIP.

Context: Appropriate risk stratification is essential in gestational diabetes (GDM) diagnosis to optimize therapeutic strategies during pregnancy. However, there are sparse data related to the newly recommended International Association of Diabetes and Pregnancy Study Groups criteria and their use in early pregnancy., Objective: This study sought to evaluate clinical and pathophysiological characteristics less up to gestational week (GW) 21 in women with early and late GDM onset., Design and Setting: This was a prospective study conducted at the Medical University of Vienna., Patients and Interventions: Pregnant women (n = 211) underwent an oral glucose tolerance test at 16 GW (interquartile range, 14-18 wk) with multiple measurements of glucose, insulin, and C-peptide for evaluation of insulin sensitivity and ß-cell function in addition to detailed obstetrical risk assessment. Clinical followups were performed until end of pregnancy., Main Outcome Measure: We performed a metabolic characterization of early-onset GDM., Results: Of 81 women, 49 (23%) showed early (GDMEarly ≤ 21 GW) and 32 (15%) later manifestation (GDMLate ≥ 24 GW) whereas 130 (62%) remained normal-glucose-tolerant (NGT). In contrast with GDMLate, GDMEarly were affected by decreased insulin sensitivity (GDMEarly vs NGT, P < .001; GDMEarlyvs GDMLate, P < .001; GDMLate vs NGT, P = .410). However, both early and late manifested subjects showed impairments in ß-cell function. GDMEarly showed highest levels of preconceptional and actual body mass index (BMI), which was related to fasting glucose (r = 0.42, P < .001) and particularly insulin sensitivity (r = -0.51, P < .001). Differences in glucose disposal between the subgroups remained constant in multivariable analysis including the strongest risk factors for GDM, ie, age, history of GDM, and BMI in our population., Conclusions: Early manifestation of GDM is affected by insulin resistance that is partly explained by higher degree in obesity. However, ß-cell dysfunction was also detectable in GDMLate, indicating defective compensatory mechanisms emerging already in early pregnancy.

Context: Postprandial glucose homeostasis is regulated through the secretion of glucagon-like peptide 1 (GLP-1) through the stimulation of insulin secretion and inhibition of glucagon secretion. However, how these processes dynamically adapt to demands created by caloric challenges achieved during daily life is not known., Objective: The objective of the study was to explore the adaptation of incretin and islet hormones after mixed meals of increasing size in healthy subjects., Design: Twenty-four healthy lean subjects ingested a standard breakfast after an overnight fast followed, after 4 hours, by a lunch of a different size (511, 743, and 1034 kcal) but with identical nutrient composition together with 1.5 g paracetamol. Glucose, insulin, C-peptide, glucagon, intact GLP-1, and glucose-dependent insulinotropic polypeptide (GIP) and paracetamol were measured after the meals., Main Outcome Measure: Area under the 180-minute curve (AUC) for insulin, C-peptide, glucagon, GLP-1, and GIP and model-derived β-cell function and paracetamol appearance were calculated., Results: Glucose profiles were similar after the two larger meals, whereas after the smaller meal, there was a postpeak reduction below baseline to a nadir of 3.8 ± 0.1 mmol/L after 75 minutes (P < .001). The AUC for GLP-1, GIP, insulin, and C-peptide were significantly higher by increasing the caloric load as was β-cell sensitivity to glucose. In contrast, the AUC glucagon was the same for all three meals, although there was an increase in glucagon after the postpeak glucose reduction in the smaller meal. The 0- to 20-minute paracetamol appearance was increased by increasing meal size., Conclusion: Mixed lunch meals of increasing size elicit a caloric-dependent insulin response due to increased β-cell secretion achieved by increased GIP and GLP-1 levels. The adaptation at larger meals results in identical glucose excursions, whereas after a lower caloric lunch, the insulin response is high, resulting in a postpeak suppression of glucose below baseline.

Context: PATIENTS with acromegaly frequently display disturbances of glucose and lipid metabolism, which might contribute to their increased cardiovascular risk. Because insulin resistance and increased lipolysis have been linked to ectopic lipid deposition, altered lipid accumulation in the liver and the myocardium might contribute to metabolic and cardiac complications in these patients., Objective: The aim of this study was to investigate myocardial (MYCL) and hepatic lipid content (HCL), insulin sensitivity, and cardiac function in active acromegaly and after control of GH excess through transsphenoidal surgery., Patients: Ten patients with newly diagnosed acromegaly (ACRO&#95;active) were compared with 12 healthy controls (CON), matched for age, body mass index, and gender. In seven patients GH excess was controlled, and they were compared with their active state., Methods: MYCL and HCL were assessed by (1)H-magnetic resonance spectroscopy, pericardial fat and cardiac function by (1)H-magnetic resonance imaging, and insulin sensitivity and secretion by an oral glucose tolerance test., Results: Although MYCL tended to be lower, HCL was significantly lower in ACRO&#95;active compared with CON (HCL: 1.2% ± 1.2% vs 4.3% ± 3.5% of (1)H-magnetic resonance spectroscopy signal, P < .02). Parameters of systolic function and hypertrophy were significantly increased in ACRO&#95;active compared with CON, as were insulin secretion and resistance. After the control of GH excess, HCL and MYCL remained unchanged, but pericardial fat was increased in the patients in whom GH excess was controlled (from 11.6 ± 5.5 to 14.7 ± 6.2 cm(2), P = .02)., Conclusion: Acromegaly represents a unique condition characterized by low myocardial and hepatic lipid content despite decreased insulin sensitivity, hyperinsulinemia, and hyperglycemia. Hence, ectopic lipid accumulation does not appear to contribute to cardiac morbidity, and increased lipid oxidation might counteract ectopic lipid accumulation in GH excess.

Objective: To stop smoking is commonly associated with significant weight gain, but the mechanisms for this are poorly understood. We assessed the effects of smoking cessation on body weight, insulin sensitivity, β-cell function, and appetite., Subjects and Methods: Twenty-seven long-term smokers (n=27; nine females/18 males, 28±1 years, 22.9±0.6 kg/m(2)) attending an ambulatory smoking cessation program in a community hospital in Vienna, Austria were examined at baseline (Visit A; still smoking) and after a minimum of 3 months of smoking abstinence (Visit B; n=14); relapsed smokers were not followed up. Participants underwent 3-h oral glucose tolerance tests and body composition measurements at each study visit. Fasting (QUICKI) and dynamic (oral glucose insulin sensitivity (OGIS)) insulin sensitivity and β-cell secretion (insulinogenic index 140 (IGI40)) were calculated. Food intake was quantified with a free choice buffet. Fasting plasma concentrations of neuropeptide-Y (NPY), peptide-YY (PYY), glucagon-like peptide 1 (GLP1), leptin, ghrelin, and visfatin were measured., Results: AFTER 3 MONTHS' SMOKING ABSTINENCE, BODY WEIGHT, AND FAT MASS WERE INCREASED (+4 AND +22% RESPECTIVELY, P0.05) AND FASTING INSULIN SENSITIVITY DETERIORATED (QUICKI: post, 0.37±0.02 vs baseline, 0.41±0.2; P<0.05), while OGIS remained unchanged throughout. IGI40 increased by 31% after >3 months' smoking abstinence (P<0.01). Carbohydrate ingestion increased after stopping smoking (P<0.05). NPY fasting levels were increased after >3 months (P<0.05), PYY, GLP1, leptin, ghrelin, and visfatin were unchanged., Conclusion: Smoking cessation is associated with transient metabolic changes including increased β-cell secretion in response to glucose and fasting insulin resistance. These alterations may be associated with or contribute to the body weight gain after smoking cessation.

New-onset diabetes after transplantation (NODAT) is associated with increased risk of allograft failure, cardiovascular disease and mortality, and therefore, jeopardizes the success of renal transplantation. Increased awareness of NODAT and the prediabetic states (impaired fasting glucose and impaired glucose tolerance, IGT) has fostered previous and present recommendations, based on the management of type 2 diabetes mellitus (T2DM). Unfortunately, the idea that NODAT merely resembles T2DM is potentially misleading, because the opportunity to initiate adequate anti-hyperglycaemic treatment early after transplantation might be given away for 'tailored' immunosuppression in patients who have developed NODAT or carry personal risk factors. Risk factor-independent mechanisms, however, seem to render postoperative hyperglycaemia with subsequent development of overt or 'full-blown' NODAT, the unavoidable consequence of the transplant and immunosuppressive process itself, at least in many cases. A proof of the concept that timely preventive intervention with exogenous insulin against post-transplant hyperglycaemia may decrease NODAT was recently provided by a small clinical trial, which is awaiting confirmation from a multicentre study. However, because early insulin therapy aimed at beta-cell protection seems to contrast the currently recommended, stepwise approach of 'watchful waiting' prior to pancreatic decompensation, we here aim at reviewing recent concepts regarding the development, prevention and treatment of NODAT, some of which seem to challenge the traditional view on T2DM and NODAT. In summary, we suggest a novel, risk factor-independent management approach to NODAT, which includes glycaemic monitoring and anti-hyperglycaemic treatment in virtually everybody after transplantation. This approach has widespread implications for future research and is intended to tackle NODAT and also ultimately cardiovascular disease.

Objective: Progranulin (PGRN) was recently introduced as a novel marker of chronic inflammatory response in obesity and type 2 diabetes capable of directly affecting the insulin signaling pathway. This study aimed to investigate the role of PGRN in gestational diabetes mellitus (GDM), which is regarded as a model for early type 2 diabetes., Methods: PGRN serum levels were measured in 90 pregnant women (45 GDM and 45 normal glucose tolerance (NGT)). In addition, PGRN was measured during a 2-h, 75 g oral glucose tolerance test in 20 pregnant women (ten GDM and ten NGT) and in 16 of them post partum (ten GDM and six NGT)., Results: PGRN concentrations were significantly higher in pregnant women compared with post partum levels (536.79 ± 31.81 vs 241.53 ± 8.86, P<0.001). Multivariate regression analyses showed a strong positive correlation of PGRN with estrogen and progesterone. The insulinogenic index, a marker of early insulin secretion, displayed a positive correlation with PGRN, both during and after pregnancy (R=0.47, P=0.034; R=0.63, P=0.012). HbA1c and the oral glucose insulin sensitivity index showed significant post partum associations with PGRN (R=0.43, P=0.049; R=-0.65, P=0.009)., Conclusions: PGRN concentrations are markedly lower after pregnancy regardless of the gestational glucose tolerance state. PGRN levels per se do not discriminate between mild GDM and NGT in pregnant women. Therefore, the development of GDM appears to be due to impaired β-cell function that is not related to PGRN effect.

Context: The incretin effect is responsible for the higher insulin response to oral glucose than to iv glucose at matching glucose levels. It is not known whether this effect is restricted to glucose only., Objective: The aim of the study was to examine whether insulin and incretin hormone responses are higher after oral vs. iv challenge of a lipid emulsion with matching triglyceride levels in humans., Design, Settings, and Participants: A lipid emulsion (Intralipid) was administered orally (3 ml/kg) or iv (variable infusion rates to match triglyceride levels after oral ingestion) in healthy lean males (n = 12) at a University Clinical Research Unit. Samples were collected during 300 min., Main Outcome Measures: We measured the suprabasal area under the curve for insulin, glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), and the insulin secretory rate based on C-peptide levels by deconvolution., Results: Triglyceride levels increased similarly after oral and iv lipid; also, glucose and free fatty acid levels were similar in the two tests. Oral lipid elicited a clear insulin and C-peptide response, whereas no insulin or C-peptide responses were observed during iv lipid. Total and intact GIP and GLP-1 levels both increased after oral lipid administration but were not significantly altered after iv lipid., Conclusions: At matching triglyceride levels and with no difference in glucose and free fatty acid levels, oral lipid ingestion but not iv lipid infusion elicits a clear insulin response in association with increased GIP and GLP-1 concentrations. This may suggest that the incretin hormones also contribute to the islet response to noncarbohydrate nutrients.

Background: Several epidemiological studies revealed sex-specific differences during oral glucose tolerance tests (OGTTs), such as higher prevalence of glucose intolerance (i.e. increased glucose at the end of the OGTT) in females, which was not yet explained. Thus, we aimed to analyze sex-related distinctions on OGTT glucose metabolism, including gut absorption, in healthy humans., Methods: Females (n = 48) and males (n = 26) with comparable age (females, 45 ± 1 yr; males, 44 ± 2 yr) and body mass index (both, 25 ± 1 kg/m(2)) but different height (females, 166 ± 1 cm; males, 180 ± 2 cm; P < 0.000001), all normally glucose tolerant, as tested by frequently sampled, 3-h (75-g) OGTTs, underwent hyperinsulinemic [40 mU/(min · m(2))] isoglycemic clamp tests with simultaneous measurement of endogenous glucose (d-[6,6-(2)H(2)]glucose) production (EGP). EGP and glucose disappearance during OGTT were calculated from logarithmic relationships with clamp test insulin concentrations. After reliable model validation by double-tracer technique (r = 0.732; P < 0.007), we calculated and modeled gut glucose absorption (ABS)., Results: Females showed lower (P < 0.05) fasting EGP [1.4 ± 0.1 mg/(kg · min)] than males [1.7 ± 0.1 mg/(kg · min)] but comparable whole-body insulin sensitivity in clamp tests [females, 8.1 ± 0.4 mg/(kg · min); males, 8.3 ± 0.6 mg/(kg · min)]. Plasma glucose OGTT concentrations were higher (P < 0.04) from 30-40 min in males but from 120-180 min in females. Glucose absorption rates were 21-46% increased in the initial 40 min in males but in females by 27-40% in the third hour (P < 0.05). Gut glucose half-life was markedly higher in females (79 ± 2 min) than in males (65 ± 3 min, P < 0.0001) and negatively related to body height (r = -0.481; P < 0.0001)., Conclusions: This study in healthy, glucose-tolerant humans shows for the first time different ABS rates during OGTT in women and men and a negative relationship between body height and gut glucose half-life. Prolonged ABS in females might therefore contribute to higher plasma glucose concentrations at the end of OGTT.

Background and Aim: Several basic science studies support the existence of non-genomic glucocorticoid signaling in pancreas, liver, and adipocytes, but its clinical relevance has not yet been elucidated. This study aimed at investigating the rapid effects of hydrocortisone on the human metabolic response to glucose., Subjects and Methods: In a randomized placebo-controlled crossover study, ten healthy men received an i.v. bolus of 0.6 mg/kg hydrocortisone once and placebo once 4 min before the administration of 330 mg/kg glucose. Cortisol, glucose, insulin, C-peptide, ghrelin, and peptide YY (PYY) levels were measured during the following 3 h. Minimal model analysis was performed for evaluating the metabolic response., Results: Hydrocortisone attenuated the rise in plasma glucose during the initial 15 min following glucose administration (P=0.039), and it led to lower glucose levels during the first 2 h (P=0.017). This was accompanied by enhanced circulating insulin (P=0.02) and C-peptide (P=0.03) levels during the initial 15 min, and a 35% increase in the first-phase beta-cell function (P=0.003). Hydrocortisone decreased PYY concentrations during the initial 30 min (P=0.014), but it did not affect the ghrelin response to glucose., Conclusion: One i.v. bolus of hydrocortisone induces rapid effects on carbohydrate metabolism increasing the first-phase beta-cell function. The modulation of PYY plasma levels suggests the possible non-genomic effects of glucocorticoids on appetite-regulatory hormones.

Objective: Polycystic ovary syndrome (PCOS) has been linked to a high risk of type 2 diabetes mellitus. Disturbances in the secretion of the incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) have been observed in states with impaired glucose regulation. This paper considers the secretion of GIP and GLP-1 after oral glucose load in a group of lean, glucose-tolerant PCOS women in comparison with age- and body mass index (BMI)-matched healthy women., Design: Case control., Methods: PCOS (n=21, 25.8+/-4.1 years, BMI 21.6+/-1.7 kg/m(2)) and control healthy women (CT, n=13, 28.5+/-7.2 years, BMI 20.3+/-2.5 kg/m(2)) underwent oral glucose tolerance test (OGTT) with blood sampling for glucose, insulin, C-peptide, total GIP, and active GLP-1. Insulin sensitivity was determined both at fasting and during the test., Statistics: Repeated measures ANOVA., Results: Glucose levels and insulin sensitivity did not differ between PCOS and CT. PCOS had significantly higher levels of C-peptide (P<0.05) and tended to have higher insulin levels. The levels of total GIP were significantly higher in PCOS than in CT (P<0.001). Active GLP-1 levels exhibited a significantly different time-dependent pattern in PCOS (P<0.002 for PCOS versus time interaction). GLP-1 concentrations were similar in PCOS and CT in the early phase of OGTT and then reached significantly lower levels in PCOS than in CT at 180 min (P<0.05)., Conclusions: Increased total GIP and lower late phase active GLP-1 concentrations during OGTT characterize PCOS women with higher C-peptide secretion in comparison with healthy controls, and may be the early markers of a pre-diabetic state.

Objective: Insulin sensitivity and secretion during early and late pregnancy were assessed in women with normal glucose tolerance and gestational diabetes mellitus (GDM)., Research Design and Methods: The oral glucose tolerance test (OGTT) was performed in 903 women at 16-20th gestational week, of whom 37 had GDM (GDM1 group), and 859 repeated the OGTT at wk 26-30. At the second test, 55 had GDM (GDM2 group); the others remained normotolerant (ND group). Insulin sensitivity from OGTT (as quantitative insulin sensitivity check index and OGTT insulin sensitivity) and beta-cell function (as the ratio of the areas under the insulin and glucose concentration curves, adjusted for insulin sensitivity) were assessed in both tests., Results: In early pregnancy the quantitative insulin sensitivity check index was not different in the three groups, whereas OGTT insulin sensitivity was lowest in GDM2, intermediate in GDM1, and highest in ND. In late pregnancy both indices were reduced in GDM compared with ND and lower than in early pregnancy. In early pregnancy GDM1, but not GDM2, had lower beta-cell function than ND. During the late visit, GDM2 also showed impaired beta-cell function compared with ND; furthermore, the adaptation to the increase to insulin resistance from early to late pregnancy was defective in GDM2., Conclusions: In early pregnancy insulin sensitivity, as assessed from the OGTT but not from fasting measurements, is impaired in women who developed GDM. beta-Cell function impairment is evident only when GDM is manifest and is characterized by inappropriate adaptation to the pregnancy induced increase in insulin resistance.

Context: During insulin-modified frequently sampled iv glucose tolerance tests (IM-FSIGT), which allow assessment of insulin action, plasma glucose can markedly decrease., Objective: This study aimed to assess the counterregulatory impact of the insulin-induced fall of glucose on minimal model-derived indices of insulin sensitivity (S(I)) and glucose effectiveness., Participants: Thirteen nondiabetic volunteers (seven males, six females, aged 26 +/- 1 yr, body mass index 22.1 +/- 0.7 kg/m(2)) were studied., Design: All participants were studied in random order during IM-FSIGT (0.3 g/kg glucose; 0.03 U/kg insulin at 20 min) and during identical conditions but with a variable glucose infusion preventing a decrease of plasma glucose concentration below euglycemia (IM-FSIGT-CLAMP). Five participants additionally underwent euglycemic-hyperinsulinemic (1 mU.kg(-1).min(-1)) clamp tests., Results: Plasma glucose declined during IM-FSIGT to its nadir of 50 +/- 3 mg/dl at 60 min in parallel to a rise (P < 0.05 vs. basal) of plasma glucagon, cortisol, epinephrine, and GH. Glucose infusion rates of 4.6 +/- 0.5 mg.kg(-1).min(-1) between 30 and 180 min during IM-FSIGT-CLAMP prevented the decline of plasma glucose and the hypoglycemia counterregulatory hormone response. S(I) was approximately 68% lower during IM-FSIGT (3.40 +/- 0.36 vs. IM-FSIGT-CLAMP: 10.71 +/- 1.06 10(-4).min(-1) per microU/ml, P < 0.0001), whereas glucose effectiveness did not differ between both protocols (0.024 +/- 0.002 vs. 0.021 +/- 0.003 min(-1), P = NS). Compared with the euglycemic hyperinsulinemic clamp test, S(I) expressed in identical units from IM-FSIGT was approximately 66% (P < 0.001) lower but did not differ between the euglycemic hyperinsulinemic clamp test and the IM-FSIGT-CLAMP (P = NS)., Conclusions: The transient fall of plasma glucose during IM-FSIGT results in lower estimates of S(I), which can be explained by hormonal response to hypoglycemia.

Insulin resistance and hyperinsulinemia are often considered intrinsic features of the polycystic ovary syndrome (PCOS). Nevertheless, conflicting results of insulin sensitivity and secretion have been obtained in the subgroup of normal-weight women with PCOS. Differences in body composition, ethnicity, and diet composition and a family history of metabolic diseases may act as confounding variables in women with PCOS. In the present study, insulin sensitivity and secretion were estimated by an iv glucose tolerance test (IVGTT), analyzed by minimal models, in 20 normal-weight healthy women with PCOS and no family history of type 2 diabetes mellitus and in 20 normally ovulating women, matched for age and body mass index. Insulin sensitivity [mean (95% confidence intervals); PCOS 4.0 (2.8-5.1) vs. controls 4.5 (3.5-5.4) 10(-4) min(-1)/microU.ml], and insulin secretion, expressed as the acute insulin response to glucose [PCOS 3.7 (3.3-4.2) vs. controls 3.7 (3.4-4.0) microU/ml] were similar in the two groups. The women with PCOS showed an increased proportion of total body fat (PCOS 29% vs. controls 27.2%; P < 0.01). They also showed decreased glucose effectiveness, i.e. the proportion of glucose uptake independent from insulin activity [PCOS 2.6 (2.1-3.0) vs. controls 3.8 (3.0-4.6) mg x 100 min(-1); P = 0.01]. The levels of insulin sensitivity and of glucose effectiveness did not correlate in either group. Whether the isolated finding of decreased glucose effectiveness could reflect an early stage in the development of the metabolic aberrations often associated with the syndrome remains to be clarified.

Background: The fasting serum lipid profile [triglycerides (TGs), total cholesterol (TC), and LDL- and HDL-cholesterol (LDL-C and HDL-C)] is used to calculate lipid ratios (TC/HDL-C, LDL-C/HDL-C, TG/HDL-C) that allow identification of individuals at increased risk for cardiovascular disease. Because these individuals are also frequently insulin resistant, this study analyzed the relationships between lipid ratios and insulin sensitivity., Methods: In 132 obese [mean (SE) body mass index, 37.5 (0.6) kg/m(2)] outpatients without known diabetes mellitus, fasting serum lipid profiles and 75-g oral glucose tolerance tests were performed. Insulin sensitivity was assessed from surrogate estimates for fasting (QUICKI) and dynamic (OGIS) conditions., Results: After exclusion of other endocrine diseases (n = 35), the remaining patients were classified as glucose tolerant (n = 56), glucose intolerant (n = 22), or as having type 2 diabetes (n = 19). QUICKI and OGIS indicated severe insulin resistance in all individuals with type 2 diabetes and impaired glucose tolerance compared with glucose-tolerant individuals: QUICKI, glucose tolerant, 0.302 (0.002); glucose intolerant, 0.290 (0.002); type 2 diabetes, 0.281 (0.005); P <0.001; OGIS (mL . m(-2) . min(-1)), glucose tolerant, 343 (7), glucose intolerant, 293 (9); type 2 diabetes, 256 (12); P <0.001. Serum TG (P <0.005) and TG/HDL-C ratios (P <0.05) were increased in individuals with impaired glucose tolerance. TG/HDL-C ratios negatively correlated with QUICKI (r = -0.370; P < 0.001) and OGIS (r = -0.333; P < 0.005) in nondiabetic individuals (glucose tolerant plus glucose intolerant), but not in patients with type 2 diabetes (not significant)., Conclusions: This study demonstrates that the TG/HDL-C ratio positively correlates with insulin resistance in severely obese nondiabetic individuals.

Weight reduction after gastric bypass surgery has been attributed to a decrease of the orexigenic peptide ghrelin, which may be regulated by insulin and leptin. This study examined effects of long-term weight loss after laparoscopical adjustable gastric banding on plasma ghrelin and leptin concentrations and their relationship with insulin action. Severely obese patients (15 women, three men, 36 +/- 12 yr) underwent clinical examinations every 3 months and modified oral glucose tolerance tests to assess parameters of insulin sensitivity and secretion every 6 months. After surgery, body mass index fell from 45.3 +/- 5.3 to 37.2 +/- 5.3 and 33.6 +/- 5.5 kg/m(2) at 6 and 12 months, respectively (P < 0.0001). This was associated with lower (P < 0.0001) plasma glucose, insulin, insulin resistance, waist circumference, and blood pressure. Plasma leptin decreased from 27.6 +/- 9.5 to 17.7 +/- 9.8 (P = 0.0005) and 12.7 +/- 5.1 ng/ml (P < 0.0001). Plasma ghrelin was comparable before and at 6 months (234 +/- 53; 232 +/- 53 pmol/liter) but increased at 12 months (261 +/- 72 pmol/liter; P = 0.05 vs. 6 months). At 6 and 12 months, ghrelin levels correlated negatively with fasting plasma insulin levels and hepatic insulin extraction but not with body mass or insulin action. In conclusion, prolonged weight loss results in a rise of fasting ghrelin concentrations that correlates with fasting insulin concentrations but not improvement of insulin sensitivity.

The neuropeptide galanin is expressed in sympathetic nerve terminals that surround islet cells and inhibits insulin secretion. To explore its role for islet function, we studied mice with a loss-of-function mutation in the galanin gene [galanin knockout (KO) mice]. Intravenous 2-deoxy-glucose, which activates both the sympathetic and parasympathetic branches of the autonomic nervous system, caused an initial (1-5 min) inhibition of insulin secretion that was impaired in galanin KO mice (P = 0.027), followed by a subsequent stimulation of insulin secretion that was augmented in galanin KO mice (P < 0.01). Similar effects were seen after chemical sympathectomy by 6-hydroxydopamine. In contrast, galanin KO mice had a reduced insulin response to glucose, both in vivo (P < 0.001) and in isolated islets (P < 0.001), and to arginine, both in vivo (P = 0.012) and in vitro (P = 0.018). During an iv glucose tolerance test, galanin KO mice had impaired glucose disposal (P = 0.005) due to a reduced insulin response (P < 0.001) and a reduced insulin-independent glucose elimination (glucose effectiveness; P = 0.040). Insulin sensitivity, as judged by a euglycemic, hyperinsulinemic clamp technique, was slightly increased in galanin KO mice (P = 0.032). We conclude that 1) galanin may contribute to sympathetic influences inhibiting insulin secretion in mice, and 2) galanin KO mice have a reduced glucose-induced insulin secretion.

Insulin sensitivity and insulin secretion are mutually related such that insulin resistance is compensated by increased insulin secretion. A correct judgement of insulin secretion therefore requires validation in relation to the insulin sensitivity in the same subject. Mathematical analyses of the relationship between insulin sensitivity and insulin secretion has revealed a hyperbolic function, such that the product of the two variables is constant. This product is usually called the disposition index. Several techniques may be used for its estimation such as data derived from the frequently sampled i.v. glucose tolerance test, the oral glucose tolerance test or the glucose-dependent arginine stimulation test or the euglycemic hyperinsulinemic clamp technique in combination with a test on insulin secretion. Using these techniques the compensatory increase in beta cell function in insulin resistance has been verified in obesity, in pregnancy and after glucocorticoid administration as has the defective beta cell function as the underlying cause of impaired glucose tolerance and type 2 diabetes. Similarly, combined analysis of insulin sensitivity and insulin secretion has shown a down-regulation of beta cell function in increased insulin sensitivity accompanying weight reduction in obesity and following exercise. Acknowledging this inverse relationship between insulin secretion and insulin sensitivity therefore requires estimation of both variables for correct assessment in any individual.

Insulin resistance is associated with a low chronic inflammatory state. In this study we investigated the relationship between impaired insulin sensitivity and selected markers of inflammation and thrombin generation in obese healthy women. We examined 32 healthy obese women (body mass index > or = 28), with normal insulin sensitivity (NIS, n = 14) or impaired insulin sensitivity (n = 18), and 10 nonobese women (body mass index < 25). Impaired insulin sensitivity patients had significantly higher levels of C-reactive protein (CRP), TGF-beta 1, plasminogen activator inhibitor-1 (PAI-1), activated factor VII (VIIa), and prothrombin fragment 1 + 2 (F1 + 2) compared with either control subjects or NIS patients. On the other hand, NIS patients had higher CRP, TGF-beta 1, PAI-1, and factor VIIa, but not F1 + 2, levels than controls. Significant inverse correlations were observed between the insulin sensitivity index and TGF-beta 1, CRP, PAI-1, factor VIIa, and F1 + 2 levels. Moreover, significant direct correlations were noted between TGF-beta 1 and CRP, PAI-1, factor VIIa, and F1 + 2 concentrations. Finally, multiple regressions revealed that TGF-beta 1 and the insulin sensitivity index were independently related to F1 + 2. Our results are the first to document an in vivo relationship between insulin sensitivity and coagulative activation in obesity. The elevated TGF-beta 1 levels detected in the obese population may provide a biochemical link between insulin resistance and an increased risk for cardiovascular disease.

Ghrelin is produced by stomach oxyntic cells and thought to be involved in the regulation of body weight and food intake. We demonstrate here that the peptide inhibits insulin secretion from overnight-incubated mouse islets in the presence of 8.3, 11.1, and 22.2 mmol/liter glucose. Ghrelin was most efficient at 1 nmol/liter and its effect disappeared by raising the dose more than 25 nmol/liter. Also, insulin secretion in the presence of high K(+) concentrations (20 mmol/liter) was inhibited by ghrelin. Furthermore, when administered iv to mice together with glucose (1 g/kg), ghrelin (50 nmol/kg) inhibited both the rapid 1-min insulin response (364 +/- 90 vs. 985 +/- 114 pmol/liter in controls, P < 0.001) and the area under the 50 min curve of insulin concentration (12.6 +/- 1.2 vs. 15.6 +/- 1.2 nmol/liter x 50 min; P = 0.046) without affecting the glucose disposal rate, insulin sensitivity or glucose effectiveness, i.e. glucose disposal independent from any dynamic change in insulin. The insulinostatic effect of ghrelin was inversely related to insulin sensitivity. In contrast, ghrelin had no influence at the lower dose of 5 nmol/kg and only slightly inhibited insulin secretion at the higher dose of 150 nmol/kg. These findings therefore show that ghrelin inhibits glucose-stimulated insulin secretion in the mouse. The effect is dependent on the dose and elicited on distal signaling steps in islet cells. The results suggest that the islet beta-cells are targets for ghrelin.

In a family with agenesis of the dorsal pancreas only the mother presents with insulin-dependent diabetes mellitus, whereas her sons are glucose tolerant. We examined whether metabolic defects can be detected early in this disease. Plasma glucose profiles were obtained from patients with dorsal pancreas agenesis and from matched healthy subjects. Hepatic glycogen synthesis and breakdown were determined from the time course of glycogen concentrations using noninvasive (13)C nuclear magnetic resonance spectroscopy. Gluconeogenesis was calculated from the difference between glucose production (measured with D-[6,6-(2)H(2)]glucose) and glycogen breakdown. Frequently sampled iv glucose tolerance tests were performed to assess insulin secretion and sensitivity. The mean plasma glucose level was higher (12.9 +/- 0.4 vs. 5.9 +/- 0.1 mmol/liter), whereas the peak plasma insulin level was lower (236 vs. 397 +/- 23 pmol/liter) in the diabetic mother than in her nondiabetic sons and healthy subjects. In all patients, however, glycogen synthesis and breakdown were reduced by approximately 55% (P < 0.05) and 40% (P < 0.02), respectively. Gluconeogenesis (6.8 +/- 0.8 vs. 4.2 +/- 0.3 micro mol/kg.min; P < 0.05) and hepatic insulin clearance (6.8 +/- 1.3 vs. 2.8 +/- 1.0 ml/kg.min) were increased in all patients. In conclusion, patients with complete agenesis of the dorsal pancreas exhibit marked defects in hepatic glycogen metabolism, which are present even in the nondiabetic offspring.

Gastrin-releasing peptide (GRP) is an islet neuropeptide that stimulates insulin secretion. To explore whether islet GRP contributes to neurally mediated insulin secretion, we studied GRP receptor (GRPR)-deleted mice. By using RT-PCR we showed that GRPR mRNA is expressed in islets of wild-type mice, but is lost in GRPR-deleted mice. Functional studies revealed that GRP potentiates glucose-stimulated insulin secretion in wild-type animals, but not in GRPR-deleted mice. This shows that GRPR is the receptor subtype mediating GRP-induced insulin secretion and that GRPR-deleted mice are tools for studying the physiological role of islet GRP. We found that GRPR-deleted mice display 1) augmentation of the insulin response to glucose by a mechanism inhibited by ganglionic blockade; 2) increased insulin responsiveness also to the cholinergic agonist carbachol, but not to arginine; 3) impaired insulin and glucagon responses to autonomic nerve activation by 2-deoxyglucose; 4) normal islet adaptation to high fat-induced insulin resistance and fasting; and 5) normal islet cytoarchitecture, as revealed by immunocytochemistry of insulin and glucagon. In conclusion, 1) GRPR is the receptor subtype mediating the islet effects of GRP; 2) GRP contributes to insulin secretion induced by activation of the autonomic nerves; and 3) deletion of GRPR is compensated by increased cholinergic sensitivity.

Moderate alcohol (ETOH) intake has been associated with a significant reduction in risk for infarction among general populations. In this study, we assessed the effects of low-dose ETOH (40 g over 3-h period as vodka) on the interaction between glucose (G), insulin, and lactate (L) during the insulin-modified frequently sampled i.v. glucose tolerance test (FSIGT) (0.3 U/kg body weight between 20-25 min) in eight normal volunteers. In the control (C) study, water was administered. An insulin-independent two-compartment model was used to describe G and L kinetics. Insulin sensitivity (S(I)) was significantly higher in the ETOH study than in the C study (2.49 +/- 0.52 vs. 0.92 +/- 0.20 10(-4) min(-1)microU(-1)ml, C vs. ETOH; P = 0.0391). No significant differences were observed in G effectiveness (0.029 +/- 0.004 vs. 0.033 +/- 0.004 min(-1)). Blood L levels were higher during FSIGT when ETOH was administered [area under the curve (AUC), 201 plus minus 16 vs. 123 +/- 23 mmol/liter in 240 min; P = 0.0001]. The dynamic analysis of blood L concentrations showed that ETOH also significantly decreased L clearance (0.0016 +/- 0.0011 vs. 0.0029 +/- 0.0002 min(-1); P = 0.0156), whereas no difference was observed for the fractional conversion of the rate of G disappearance to L (0.0033 +/- 0.0012 vs. 0.0031 +/- 0.0005 min(-1)). ETOH decreased baseline plasma FFA concentration; AUC of FFA was markedly reduced with ETOH (65 +/- 14 vs. 109 plus minus 17 mmol/liter in 240 min; P = 0.0063) and inversely correlated with S(I) (r = 0.693; P = 0.0029). The amount of C-peptide in 240 min as well as the amounts before and after insulin administration were not different between the two tests. We concluded that G and L kinetics derived from FSIGT shows that moderate ETOH intake: 1) improves insulin action; 2) decreases L clearance; and 3) does not affect beta cell function. Because ETOH at moderate doses has a marked antilipolytic action, it might improve insulin action by improving substrate competition. The present findings suggest that moderate alcohol consumption in the diet should not be discouraged.

This study examined whether insulin secretion, insulin sensitivity, glucose effectiveness (SG), and hepatic extraction (HE) of insulin are altered by age when glucose tolerance is normal. A frequently sampled i.v. glucose tolerance test was performed in 20 elderly (E, 10/10 male/female, all 63 yr old) and in 20 young subjects (Y, 10/10 male/female, all 27 yr old), who were similar in body mass index and 2-h blood glucose during oral glucose tolerance test. E exhibited impaired glucose elimination (i.v. tolerance index, 1.31 +/- 0.10 vs. 1.70 +/- 0.12% min-1; P = 0.019). First-phase insulin secretion and SI did not differ between the groups, whereas E had lower glucose sensitivity of second-phase insulin secretion (0.40 +/- 0.07 vs. 0.70 +/- 0.08 (pmol/L)min-2/(mmol/L), P = 0.026), lower SG, 0.017 +/- 0.002 vs. 0.025 +/- 0.002 min-1, P = 0.004), and higher HE (81.3 +/- 2.4 vs. 73.2 +/- 2.1%, P = 0.013). Across both groups, SG correlated positively with glucose tolerance index (r = 0.58, P < 0.001) and negatively with HE (r = -0.54, P < 0.001). Plasma leptin and glucagon did not change by age, whereas plasma pancreatic polypeptide (PP) was higher in E (122 +/- 18 vs. 66 +/- 6 pg/mL, P = 0.004). PP did not, however, correlate to any other parameter. We conclude that E subjects with normal oral glucose tolerance have reduced SG, impaired second-phase insulin secretion, and increased HE, whereas SI and first-phase insulin secretion seem normal. SG seems most related to age-dependent impairment of glucose elimination, whereas leptin, glucagon, and PP do not seem to contribute.

Background: Calculation of Kt/V and assessment of nutrition have so far been dependent upon off-line urea measurements of blood or dialysate samples. Here we describe a biosensor for on-line urea measurement during haemodiafiltration. Methods. The biosensor consisted of a cartridge containing covalently linked urease placed between two conductivity cells. The biosensor was placed on the outlet line of a haemofilter in series with a dialyser in order to obtain an aliquot of plasma ultrafiltrate for on-line measurement of urea., Results: Urea nitrogen concentrations were highly correlated to the difference (Delta) in conductivity measured by the two conductivity cells both in aqueous solutions (in-vitro studies, y=-6. 676+32.12x, R2=0.998, P<0.0001) and in ultrafiltrates (ex-vivo studies, y=-637+32.01x, R2=0.98, P<0.00001). Delta conductivity was highly reproducible (% variation: ).8-5.3%) and stable (maximal % variation at 150 mg/dl after 100 min. 0.9+/-0.3 vs initial values). The intradialytic plasma water urea profile was obtained in 10 haemodialysis patients. To study recirculation, the plasma water urea profile was analysed before and 3 min after stopping the dialysate flow. The pre- and post-stopped flow ratio (1.21+/-0.1, mean+/-1 SD) was superimposable to conventional blood sampling data (opposite arm venous arterial: 1.22+/-0.11) and allowed correction for recirculation. A novel approach to urea kinetic modelling was described and used to reliably project end-dialysis and post-dialysis rebound urea concentration as early as 90 min. Projected (29.2+/-10.4 g) or measured (29.8+/-10.5 g) net urea removal was highly correlated with the amount of urea collected in the total spent dialysate (29.7+/-10.6 g) (R2=0.99, R2=0.97 respectively)., Conclusions: These results indicate that on-line, real-time analysis of urea kinetics may provide information on delivery of adequate dialysis in high-efficiency techniques.

To identify the pathogenic factors responsible for glucose intolerance of aging, we measured a variety of metabolic parameters, including insulin sensitivity and islet cell function, in 10 young (18-36 yr old) and 10 older (57-82 yr old) men of normal body weight. Subject groups had equivalent fasting plasma glucose and fat cell size values. Frequently sampled iv glucose tolerance tests were performed, and the data were analyzed by computer using the minimal model approach. This technique yields the following measures: SI, the insulin sensitivity index; phi 1 and phi 2, indices of first and second phase beta-cell responsiveness to glucose; n, fractional insulin clearance, and SG, a measure of dynamic glucose disappearance dependent on glucose per se. We also evaluated beta-cell responsiveness independently by measuring the plasma insulin response to arginine injections at three levels of glycemia and calculated potentiation slope from the relationship between the acute insulin response to arginine and the prestimulus glucose level. The older men were glucose intolerant (glucose disappearance rate, 1.32% min-1) compared to the younger men (glucose disappearance rate, 2.21% min-1; P less than 0.01). This intolerance was the result of both a beta-cell defect and insulin resistance. The potentiation slope (r = -0.67; P less than 0.02) and phi 2 (r = -0.47; P less than 0.05) both decreased with age. In addition, SI in the older group was diminished 63% (2.4 vs. 6.5; 10(-4) min-1/microU/ml; P less than 0.001) and was unrelated to differences in body fat. No differences were found in either n or SG. These studies suggest that the diminished glucose tolerance of aging in normal weight men has multifactorial causality. Both beta-cell dysfunction and insulin resistance are important. In contrast, we found little evidence for changes in insulin clearance or insulin-independent glucose disappearance contributing to age-related glucose intolerance.