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Objective This work aimed to investigate the effect of the SGLT2 inhibitor, dapagliflozin (DAPA), on cardiac function and the metabolic and hormonal response to moderate exercise in people with type 2 diabetes. Methods This was a double-blind, placebo-controlled crossover study with a 4-week washout period. Nine participants were randomly assigned to receive either 4 weeks of DAPA or 4 weeks of placebo. After each treatment, they underwent an exercise protocol with 2 consecutive 10-minute stages at a constant load corresponding to 40% and 70% maximal oxygen consumption (VO2max), coupled with hormonal and metabolic analysis. A blinded transthoracic echocardiogram was performed 3 days later. Results During the exercise protocol, glucose and lactate were lower (P < .0001 and P < .05, respectively) and β-hydroxybutyrate (BOBH) and growth hormone (GH) were higher (P < .0005 and P = .01) following DAPA treatment compared to placebo. There was a trend for lower insulin with DAPA. Adrenalin, noradrenalin, and glucagon were not different. Following DAPA participants demonstrated an increased mean peak diastolic mitral annular velocity (e’) in comparison to placebo (P = .03). The indexed left atrial volume and right ventricular e” were reduced following DAPA compared with placebo (P = .045 and P = .042, respectively). Arterial stiffness was not different between treatments (DAPA 9.35 ± 0.60 m/s; placebo 9.07 ± 0.72 m/s). Conclusion During exercise, GH may be more important than catecholamines in driving the shift from glucose to fatty acid metabolism by SGLT2 inhibitors. The 4-week crossover design showed changes in cardiac function were rapid in onset and reversible.

OBJECTIVE To investigate the mechanism for increased ketogenesis following treatment with the SGLT2 inhibitor dapagliflozin in people with type 2 diabetes. RESEARCH DESIGN AND METHODS The design was a double-blind, placebo-controlled, crossover study with a 4-week washout period. Participants received dapagliflozin or placebo in random order for 4 weeks. After each treatment, they ingested 30 mL of olive oil containing [U-13C]palmitate to measure ketogenesis, with blood sampling for 480 min. Stable isotopes of glucose and glycerol were infused to measure glucose flux and lipolysis, respectively, at 450–480 min. RESULTS Glucose excretion rate was higher and peripheral glucose uptake lower with dapagliflozin than placebo. Plasma β-hydroxybutyrate (BOHB) concentrations and [13C2]BOHB concentrations were higher and glucose concentrations lower with dapagliflozin than placebo. Nonesterified fatty acids (NEFAs) were higher with dapagliflozin at 300 and 420 min, but lipolysis at 450–480 min was not different. Triacylglycerol at all time points and endogenous glucose production rate at 450–480 min were not different between treatments. CONCLUSIONS The increase in ketone enrichment from the ingested palmitic acid tracer suggests that meal-derived fatty acids contribute to the increase in ketones during treatment with dapagliflozin. The increase in BOHB concentration with dapagliflozin occurred with only minimal changes in plasma NEFA concentration and no change in lipolysis. This finding suggests a metabolic switch to increase ketogenesis within the liver.

Scope: Fructose exacerbates post-prandial hypertriacylglycerolaemia. This may be partly due to increased enterocyte de novo lipogenesis (DNL). It is unknown whether this is concentration-dependent or whether fructose has a greater effect on lipid synthesis than glucose. The dose-dependent effects of fructose and glucose on DNL and de novo triacylglycerol (TAG)-glycerol synthesis were investigated in an enterocyte model, Caco-2 cells. Methods and results: Caco-2 cells were treated for 96h with 5mM, 25mM or 50mM fructose or glucose, or 12.5mM fructose/12.5mM glucose mix. DNL was measured following addition of [13C2]-acetate to apical media. In separate experiments, [13C6]-fructose and [13C6]-glucose were used to measure DNL and de novo TAG-glycerol synthesis. DNL from [13C2]-acetate was detected following all treatments, with greater amounts in intracellular than secreted (media) samples (all P

Aim People of Black African ancestry, who are known to be at disproportionately high risk of type 2 diabetes (T2D), typically exhibit lower hepatic insulin clearance compared with White Europeans. However, the mechanisms underlying this metabolic characteristic are poorly understood. We explored whether low insulin clearance in Black African (BA) men could be explained by insulin resistance, subclinical inflammation or adiponectin concentrations. Methods BA and White European (WE) men, categorised as either normal glucose tolerant (NGT) or with T2D, were recruited to undergo the following: a mixed meal tolerance test with C-peptide modelling to determine endogenous insulin clearance; fasting serum adiponectin and cytokine profiles; a hyperinsulinaemic–euglycaemic clamp to measure whole-body insulin sensitivity; and magnetic resonance imaging to quantify visceral adipose tissue. Results Forty BA (20 NGT and 20 T2D) and 41 WE (23 NGT and 18 T2D) men were studied. BA men had significantly lower insulin clearance (P = 0.011) and lower plasma adiponectin (P = 0.031) compared with WE men. In multiple regression analysis, ethnicity, insulin sensitivity and plasma adiponectin were independent predictors of insulin clearance, while age, visceral adiposity and tumour necrosis factor alpha (TNF-α) did not significantly contribute to the variation. Conclusion These data suggest that adiponectin may play a direct role in the upregulation of insulin clearance beyond its insulin-sensitising properties.

Introduction The newer glucose-lowering therapies for type 2 diabetes (T2D), the glucagon-like peptide-1 receptor agonists (GLP1-RAs) and the sodium-glucose co-transporter 2 inhibitors (SGLT2i), have additional clinical benefits beyond improving glycaemic control; promoting weight loss, addressing associated cardiovascular risk factors and reducing macrovascular and microvascular complications. Considering their independent mechanisms of actions, there is a potential for significant synergy with combination therapy, yet limited data exist. This 32-week randomised, double-blind, placebo-controlled trial will gain mechanistic insight into the effects of coadministration of exenatide QW, a weekly subcutaneous GLP1-RA, with dapagliflozin, a once daily oral SGLT2i, on the dynamic, adaptive changes in energy balance, total, regional and organ-specific fat mass and multiorgan insulin sensitivity. Methods and analysis 110 obese patients with diagnosed T2D (glycated haemoglobin, HbA1c ≥48 mmol/mol) will be treated for 32 weeks with dapagliflozin (10 mg once daily either alone or in combination with exenatide QW (2 mg once weekly); active treatments will be compared with a control group (placebo tablet and sham injection). The primary objective of the study is to compare the adjusted mean reduction in total body fat mass (determined by dual-energy X-ray absorptiometry, DEXA) from baseline following 32 weeks of treatment with exenatide QW and dapagliflozin versus dapagliflozin alone compared with control (placebo). Secondary outcome measures include changes in (1) energy balance (energy intake and energy expenditure measured by indirect calorimetry); (2) appetite (between and within meals) and satiety quotient; (3) body composition including visceral adipose tissue, subcutaneous adipose tissue, liver and pancreatic fat. Exploratory outcome measures include metabolic changes in hepatic and peripheral insulin sensitivity (using a two-stage hyperinsulinaemic, euglycaemic clamp), central nervous system responses to food images using blood oxygen level-dependent (BOLD) functional MRI (fMRI) and changes in cardiovascular function (using transthoracic echocardiography, cardiac MR and duplex ultrasonography). Ethics and dissemination This study has been approved by the North West Liverpool Central Research Ethics Committee (14/NW/1147) and is conducted in accordance with the Declaration of Helsinki and the Good Clinical Practice. Results from the study will be published in peer-reviewed scientific and open access journals and/or presented at scientific conferences and summarised for distribution to the participants. Trial sponsor University of Liverpool. Trial registration number ISRCTN 52028580; EUDRACT number 2015-005242-60.

IntroductionThe newer glucose-lowering therapies for type 2 diabetes (T2D), the glucagon-like peptide-1 receptor agonists (GLP1-RAs) and the sodium-glucose co-transporter 2 inhibitors (SGLT2i), have additional clinical benefits beyond improving glycaemic control; promoting weight loss, addressing associated cardiovascular risk factors and reducing macrovascular and microvascular complications. Considering their independent mechanisms of actions, there is a potential for significant synergy with combination therapy, yet limited data exist. This 32-week randomised, double-blind, placebo-controlled trial will gain mechanistic insight into the effects of coadministration of exenatide QW, a weekly subcutaneous GLP1-RA, with dapagliflozin, a once daily oral SGLT2i, on the dynamic, adaptive changes in energy balance, total, regional and organ-specific fat mass and multiorgan insulin sensitivity.Methods and analysis110 obese patients with diagnosed T2D (glycated haemoglobin, HbA1c ≥48 mmol/mol) will be treated for 32 weeks with dapagliflozin (10 mg once daily either alone or in combination with exenatide QW (2 mg once weekly); active treatments will be compared with a control group (placebo tablet and sham injection). The primary objective of the study is to compare the adjusted mean reduction in total body fat mass (determined by dual-energy X-ray absorptiometry, DEXA) from baseline following 32 weeks of treatment with exenatide QW and dapagliflozin versus dapagliflozin alone compared with control (placebo). Secondary outcome measures include changes in (1) energy balance (energy intake and energy expenditure measured by indirect calorimetry); (2) appetite (between and within meals) and satiety quotient; (3) body composition including visceral adipose tissue, subcutaneous adipose tissue, liver and pancreatic fat. Exploratory outcome measures include metabolic changes in hepatic and peripheral insulin sensitivity (using a two-stage hyperinsulinaemic, euglycaemic clamp), central nervous system responses to food images using blood oxygen level-dependent (BOLD) functional MRI (fMRI) and changes in cardiovascular function (using transthoracic echocardiography, cardiac MR and duplex ultrasonography).Ethics and disseminationThis study has been approved by the North West Liverpool Central Research Ethics Committee (14/NW/1147) and is conducted in accordance with the Declaration of Helsinki and the Good Clinical Practice. Results from the study will be published in peer-reviewed scientific and open access journals and/or presented at scientific conferences and summarised for distribution to the participants.Trial sponsorUniversity of Liverpool.Trial registration numberISRCTN 52028580; EUDRACT number 2015-005242-60.

AIMS We aimed to assess ethnic differences in inflammatory markers and their relationships with insulin sensitivity and regional adiposity between white European and black African men. METHODS A total of 53 white European and 53 black African men underwent assessment of inflammatory markers alongside Dixon-magnetic resonance imaging to quantify subcutaneous and visceral adipose tissue and intrahepatic lipid. A hyperinsulinaemic-euglycaemic clamp was used to measure whole-body and adipose tissue insulin sensitivity. To assess ethnic differences in relationships, the statistical significance of an interaction term between adipokines and ethnic group was tested in multivariable regression models. RESULTS The black African men exhibited significantly lower adiponectin and tumour necrosis factor-α (TNF-α) and greater interleukin-10 (IL-10) compared to white European men (all p

The objective of the study was to assess associations of the rs9939609 FTO allele to glucose tolerance, hepatic and total insulin sensitivity (IS) in individuals with obesity. From a low-dose hyperinsulinemic euglycemic clamp with glucose-tracer, hepatic IS was assessed by rates of basal and suppressed glucose appearance (Ra), a measure of endogenous glucose production (EGP), and the hepatic insulin resistance index (HIR). Total IS was assessed by rates of glucose infusion (GIR), disappearance (Rd), and metabolic clearance (MCR). From a meal test we assessed IS by the Matsuda index and glucose tolerance by glucose and insulin measurements in the fasted state and postprandially for 2.5 h. The meal test was performed in 97 healthy individuals with BMI ≥35 in similar-sized risk-allele groups (n = 32 T/T, 31 A/T, and 34 A/A), and 79 of them performed the clamp. We analyzed outcomes separately for males and females, and adjusted glucose Ra, Rd, MCR, GIR, and HIR for fat mass. We did not find genotype effects on EGP. Among males, genotype A/A was associated with a significantly lower glucose Rd, MCR, and Matsuda index score relative to genotype T/T. Glucose tolerance was significantly lower in males with genotype A/T vs. T/T and A/A. For females, there were no genotype effects on hepatic or total IS, or on glucose tolerance. Independently of genotypes, females displayed a significantly better hepatic and total IS, and better glucose tolerance than males. We conclude that in subjects with similar obesity we did not register any FTO risk-allele effect on hepatic IS. A FTO risk-allele effect on total IS was registered in males only, findings which need to be reproduced in further studies. Results confirm marked differences in IS between the biological sexes and extend present knowledge by demonstrating a lower endogenous glucose production in females vs. males in uniformly obese individuals. Copyright: © 2021 de Soysa et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

OBJECTIVE To determine the effect of the sodium–glucose cotransporter 2 inhibitor dapagliflozin on glucose flux, lipolysis, and ketone body concentrations during insulin withdrawal in people with type 1 diabetes. RESEARCH DESIGN AND METHODS A double-blind, placebo-controlled crossover study with a 4-week washout period was performed in 12 people with type 1 diabetes using insulin pump therapy. Participants received dapagliflozin or placebo in random order for 7 days. Stable isotopes were infused to measure the glucose Ra, Rd, and lipolysis. At isotopic steady state, insulin was withdrawn, and the study was terminated after 600 min or earlier if blood glucose reached 18 mmol/L, bicarbonate 5.0 mmol/L. RESULTS At baseline, glucose Ra was significantly higher for the dapagliflozin group than the placebo group. Following insulin withdrawal, plasma glucose concentrations at the end point were significantly lower with dapagliflozin than placebo and glucose Rd area under the curve (AUC)0–180 min and β-hydroxybutyrate (BOHB) AUC0–180 min were significantly higher. There was a small but significantly higher glycerol Ra (measure of lipolysis) AUC0–180 min with dapagliflozin. Nonesterified fatty acid concentrations were not different between treatments. When divided by BMI >27 and CONCLUSIONS During insulin withdrawal, the increase in BOHB with dapagliflozin may be partially due to increased lipolysis. However, reduced renal excretion, reduced BOHB uptake by peripheral tissues, or a metabolic switch to increased ketogenesis within the liver may also play a role.

A high fructose intake exacerbates postprandial plasma triacylglycerol (TAG) concentration, an independent risk factor for cardiovascular disease, although it is unclear whether this is due to increased production or impaired clearance of triacylglycerol (TAG)-rich lipoproteins. We determined the in vivo acute effect of fructose on postprandial intestinal and hepatic lipoprotein TAG kinetics and de novo lipogenesis (DNL). Five overweight men were studied twice, 4 weeks apart. They consumed hourly mixed-nutrient drinks that were high-fructose (30% energy) or low-fructose (&lt, 2% energy) for 11 h. Oral 2H2O was administered to measure fasting and postprandial DNL. Postprandial chylomicron (CM)-TAG and very low-density lipoprotein (VLDL)-TAG kinetics were measured with an intravenous bolus of [2H5]-glycerol. CM and VLDL were separated by their apolipoprotein B content using antibodies. Plasma TAG (p &lt, 0.005) and VLDL-TAG (p = 0.003) were greater, and CM-TAG production rate (PR, p = 0.046) and CM-TAG fractional catabolic rate (FCR, p = 0.073) lower when high-fructose was consumed, with no differences in VLDL-TAG kinetics. Insulin was lower (p = 0.005) and apoB48 (p = 0.039), apoB100 (p = 0.013) and non-esterified fatty acids (NEFA) (p = 0.013) were higher after high-fructose. Postprandial hepatic fractional DNL was higher than intestinal fractional DNL with high-fructose (p = 0.043) and low-fructose (p = 0.043). Fructose consumption had no effect on the rate of intestinal or hepatic DNL. We provide the first measurement of the rate of intestinal DNL in humans. Lower CM-TAG PR and CM-TAG FCR with high-fructose consumption suggests lower clearance of CM, rather than elevated production, may contribute to elevated plasma TAG, possibly due to lower insulin-mediated stimulation of lipoprotein lipase.

Nonalcoholic fatty liver disease (NAFLD) is characterized by low-circulating concentration of high-density lipoprotein cholesterol (HDL-C) and raised triacylglycerol (TAG). Exercise reduces hepatic fat content, improves insulin resistance and increases clearance of very-low-density lipoprotein-1 (VLDL1). However, the effect of exercise on TAG and HDL-C metabolism is unknown. We randomized male participants to 16 wk of supervised, moderate-intensity aerobic exercise ( n = 15), or conventional lifestyle advice ( n = 12). Apolipoprotein A-I (apoA-I) and VLDL-TAG and apolipoprotein B (apoB) kinetics were investigated using stable isotopes (1-[13C]-leucine and 1,1,2,3,3-2H5 glycerol) pre- and postintervention. Participants underwent MRI/spectroscopy to assess changes in visceral fat. Results are means ± SD. At baseline, there were no differences between exercise and control groups for age (52.4 ± 7.5 vs. 52.8 ± 10.3 yr), body mass index (BMI: 31.6 ± 3.2 vs. 31.7 ± 3.6 kg/m2), and waist circumference (109.3 ± 7.5 vs. 110.0 ± 13.6 cm). Percentage of liver fat was 23.8 (interquartile range 9.8–32.5%). Exercise reduced body weight (101.3 ± 10.2 to 97.9 ± 12.2 kg; P < 0.001) and hepatic fat content [from 19.6%, interquartile range (IQR) 14.6–36.1% to 8.9% (4.4–17.8%); P = 0.001] and increased the fraction HDL-C concentration (measured following ultracentrifugation) and apoA-I pool size with no change in the control group. However, plasma and VLDL1-TAG concentrations and HDL-apoA-I fractional catabolic rate (FCR) and production rate (PR) did not change significantly with exercise. Both at baseline (all participants) and after exercise there was an inverse correlation between apoA-I pool size and VLDL-TAG and -apoB pool size. The modest effect of exercise on HDL metabolism may be explained by the lack of effect on plasma and VLDL1-TAG.

Aim Gut microbial dysbiosis is implicated in the pathogenesis of non-alcoholic steatohepatitis (NASH). We investigated downstream effects of gut microbiota modulation on markers of hepatic inflammation, steatosis, and hepatic and peripheral insulin sensitivity in patients with NASH using rifaximin therapy. Methods Patients with biopsy-proven NASH and elevated aminotransferase values were included in this open-label pilot study, all receiving 6 weeks rifaximin 400 mg twice daily, followed by a 6-week observation period. The primary endpoint was change in alanine aminotransferase (ALT) after 6 weeks of rifaximin. Secondary endpoints were change in hepatic lipid content and insulin sensitivity measured with a hyperinsulinemic–euglycemic clamp. Results Fifteen patients (13 men and 2 women) with a median (range) age of 46 (32–63) years were included. Seven had diabetes on oral hypoglycemic medications and 8 had no diabetes. After 6 weeks of therapy, no differences were seen in ALT (55 [33–191] vs. 63 [41–218] IU/L, P = 0.41), peripheral glucose uptake (28.9 [19.4–48.3] to 25.5 [17.7–47.9] μmol/kg/min, P = 0.30), hepatic insulin sensitivity (35.2 [15.3–51.7]% vs. 30.0 [10.8–50.5]%, P = 0.47), or hepatic lipid content (21.6 [2.2–46.2]% vs. 24.8 [1.7–59.3]%, P = 0.59) before and after rifaximin treatment. After 12 weeks from baseline, serum ALT increased to 83 (30–217) IU/L, P = 0.02. There was a significant increase in the homeostasis model assessment–estimated insulin resistance index (P = 0.05). The urinary metabolic profile indicated a significant reduction in urinary hippurate with treatment, which reverted to baseline after cessation of rifaximin, although there was no consistent difference in relative abundance of fecal microbiota with treatment. Conclusion These data do not indicate a beneficial effect of rifaximin in patients with NASH.

BACKGROUND: Anthocyanin-rich blueberry intake is associated with reduced type 2 diabetes and cardiovascular disease (CVD) risk in prospective studies, although long-term randomized controlled trials (RCTs) have not been conducted in at-risk populations.OBJECTIVE: In the longest-duration RCT to date, we examined the effect of 6-mo blueberry intake on insulin resistance and cardiometabolic function in metabolic syndrome.METHODS: A double-blind, parallel RCT (n = 115; age 63 ± 7 y; 68% male; body mass index 31.2 ± 3.0 kg/m2) was conducted, which fed 2 dietarily achievable blueberry intakes [equivalent to 1/2 and 1 cup/d (75/150 g)] compared with matched placebo. Insulin resistance was assessed via the homeostasis model assessment of insulin resistance (primary endpoint) and confirmed by [6-6-2H2]-glucose-labeled, 2-step hyperinsulinemic clamp (n = 20). Clinically relevant cardiometabolic endpoints [including flow-mediated dilatation, augmentation index, lipoprotein status (by nuclear magnetic resonance spectroscopy), and nitric oxide (NO)-related metabolite assay] and anthocyanin metabolism were assessed.RESULTS: A daily intake of 1 cup of blueberries improved endothelial function (flow-mediated dilatation: +1.45%; 95% CI: 0.83%, 2.1%; P = 0.003), systemic arterial stiffness (augmentation index: -2.24%; 95% CI: -3.97%, -0.61%; P = 0.04) and attenuated cyclic guanosine monophosphate concentrations. In statin nonusers (n = 71), elevated high-density lipoprotein cholesterol (+0.08 mmol/L; P = 0.03), high-density lipoprotein particle density (+0.48n, ×10-6; P = 0.002) and apolipoprotein A-I (+0.05 g/L; P = 0.01) concentrations were observed following the 1-cup/d intervention. Treatment compliance was 94.1% (wrapper returns) and total concentrations of anthocyanin-derived phenolic acid metabolites significantly increased, dose-dependently, in serum and 24-h urine (P < 0.01 and P < 0.001, respectively). Insulin resistance, pulse wave velocity, blood pressure, NO, and overall plasma thiol status were unaffected. Likewise, a half cup per day had no effect on any biomarkers.CONCLUSIONS: Despite insulin resistance remaining unchanged we show, to our knowledge, the first sustained improvements in vascular function, lipid status, and underlying NO bioactivity following 1 cup blueberries/d. With effect sizes predictive of 12-15% reductions in CVD risk, blueberries should be included in dietary strategies to reduce individual and population CVD risk. This study was registered at clinicaltrials.gov as NCT02035592.

Aims/hypothesis Type 2 diabetes is more prevalent in black African than white European populations although, paradoxically, black African individuals present with lower levels of visceral fat, which has a known association with insulin resistance. Insulin resistance occurs at a tissue-specific level; however, no study has simultaneously compared whole body, skeletal muscle, hepatic and adipose tissue insulin sensitivity between black and white men. We hypothesised that, in those with early type 2 diabetes, black (West) African men (BAM) have greater hepatic and adipose tissue insulin sensitivity, compared with white European men (WEM), because of their reduced visceral fat. Methods Eighteen BAM and 15 WEM with type 2 diabetes underwent a two-stage hyperinsulinaemic–euglycaemic clamp with stable glucose and glycerol isotope tracers to assess tissue-specific insulin sensitivity and a magnetic resonance imaging scan to assess body composition. Results We found no ethnic differences in whole body, skeletal muscle, hepatic or adipose tissue insulin sensitivity between BAM and WEM. This finding occurred in the presence of lower visceral fat in BAM (3.72 vs 5.68 kg [mean difference −1.96, 95% CI −3.30, 0.62]; p = 0.01). There was an association between skeletal muscle and adipose tissue insulin sensitivity in WEM that was not present in BAM (r = 0.78, p

Context Glucagon-like peptide-1 (GLP-1) agonists control postprandial glucose and lipid excursion in type 2 diabetes; however, the mechanisms are unclear. Objective To determine the mechanisms of postprandial lipid and glucose control with lixisenatide (GLP-1 analog) in type 2 diabetes. Design Randomized, double-blind, cross-over study. Setting Centre for Diabetes, Endocrinology, and Research, Royal Surrey County Hospital, Guildford, United Kingdom. Patients Eight obese men with type 2 diabetes [age, 57.3 ± 1.9 years; body mass index, 30.3 ± 1.0 kg/m2; glycosylated hemoglobin, 66.5 ± 2.6 mmol/mol (8.2% ± 0.3%)]. Interventions Two metabolic studies, 4 weeks after lixisenatide or placebo, with cross-over and repetition of studies. Main Outcome Measures Study one: very-low-density lipoprotein (VLDL) and chylomicron (CM) triacylglycerol (TAG) kinetics were measured with an IV bolus of [2H5]glycerol in a 12-hour study, with hourly feeding. Oral [13C]triolein, in a single meal, labeled enterally derived TAG. Study two: glucose kinetics were measured with [U-13C]glucose in a mixed-meal (plus acetaminophen to measure gastric emptying) and variable IV [6,6-2H2]glucose infusion. Results Study one: CM-TAG (but not VLDL-TAG) pool-size was lower with lixisenatide (P = 0.046). Lixisenatide reduced CM [13C]oleate area under the curve (AUC)60–480min concentration (P = 0.048) and increased CM-TAG clearance, with no effect on CM-TAG production rate. Study two: postprandial glucose and insulin AUC0–240min were reduced with lixisenatide (P = 0.0051; P < 0.05). Total glucose production (P = 0.015), rate of glucose appearance from the meal (P = 0.0098), and acetaminophen AUC0–360min (P = 0.006) were lower with lixisenatide than with placebo. Conclusions Lixisenatide reduced [13C]oleate concentrations, derived from a single meal in CM-TAG and glucose rate of appearance from the meal through delayed gastric emptying. However, day-long CM production, measured with repeated meal feeding, was not reduced by lixisenatide and decreased CM-TAG concentration resulted from increased CM-TAG clearance., Using stable isotopes, lixisenatide acutely slowed gastric emptying, lowering postprandial TAG levels. A more prolonged effect of reduced chylomicron TAG was from increased clearance.

Context: Intrapancreatic lipid (IPL) has been linked with beta-cell dysfunction. Black populations suffer disproportionately from type 2 diabetes (T2D) and show distinctions in beta-cell function compared to Whites.Objective: We aimed to quantify IPL in White European (WE) and Black West African (BWA) men with early T2D, and to investigate relationships between IPL and beta-cell insulin secretory function (ISF).Design, Setting and Participants: We performed a cross-sectional assessment of 18 WE and 19 BWA middle-aged men with early T2D as part of the South London Diabetes and Ethnicity Phenotyping (Soul-Deep) study.Main Outcome Measures: Participants underwent Dixon magnetic resonance imaging to determine IPL in the pancreatic head, body, and tail, and subcutaneous and visceral adipose tissue volumes. Modelled first-phase and second-phase ISF were comprehensively determined using c-peptide measurements during a 3-hour meal tolerance test and a 2-hour hyperglycemic clamp test.Results: WE men had higher mean IPL than BWA men (P=0.029), mainly due to higher IPL in the pancreatic head in WE men (P=0.009). Mean IPL was inversely associated with orally stimulated first-phase ISF in WE but not BWA men (WE: r=-0.554, P=0.026; BWA: r=-0.183, P=0.468); there was no association with orally stimulated second-phase ISF in either WE or BWA men. No significant associations were found between mean IPL and intravenously stimulated ISF.Conclusions: IPL is lower in BWA than WE men with early T2D, and the lack of inverse association with orally stimulated first phase ISF in BWA men indicates that IPL may be a less important determinant of the development of T2D in BWA compared to WE men.

Labelling molecules with stable isotopes to create tracers has become a gold-standard method to study the metabolism of lipids and lipoproteins in humans. There are a range of techniques which use stable isotopes to measure fatty acid flux and oxidation, hepatic fatty synthesis, cholesterol absorption and synthesis and lipoprotein metabolism in humans. Stable isotope tracers are safe to use, enabling repeated studies to be undertaken and allowing studies to be undertaken in children and pregnant women. This review provides details of the most appropriate tracers to use, the techniques which have been developed and validated for measuring different aspects of lipid metabolism and some of the limitations of the methodology.

Formoterol is a β(2)-selective agonist that enhances protein anabolism in rodents. Whether formoterol imparts anabolic benefits in humans is unknown. The objective of the study was to investigate the effects of formoterol on whole body protein rates of turnover, oxidative loss and synthesis.Open label intervention study.Fifteen healthy adults (8 men).Volunteers were treated with oral formoterol 160 μg/day for one week. Changes in leucine turnover (LRa; index of protein breakdown), oxidation (Lox; irreversible protein loss) and incorporation into protein (LIP; index of protein synthesis) were assessed using the whole body 1-[(13)C]leucine turnover technique before/after treatment.LRa, Lox and LIP correlated significantly with lean body mass (LBM). LRa, adjusted for LBM was significantly higher (P0.05, 160±6 vs 109±3 μmol/min) in men but not fractional Lox and LIP (expressed as a proportion of LRa). Formoterol reduced LRa (-9±4%) in men but stimulated LRa (9±3%) in women. Formoterol significantly reduced (P0.05) fractional Lox, an effect greater in women (-4±1 vs -1±1 %). It stimulated fractional LIP in women (∆4±1%, P0.05) but not in men (∆1±1%). Formoterol induced an absolute anabolic effect that was greater in women (30 vs 8%). Heart rate, systolic and diastolic blood pressures were unaffected.In a therapeutic dose, formoterol stimulates protein anabolism in humans. It induced gender-dimorphic effects on protein turnover and on the partitioning of amino acids from oxidative loss toward protein synthesis, effects that are greater in women than in men. Formoterol holds promise as a treatment for sarcopenia.

AimTo test the hypothesis that men of black (West) African ethnicity (black African men [BAM]) with early type 2 diabetes (T2D) would have greater insulin secretory deficits compared with white European men (WEM), following prediabetic hypersecretion.MethodsIn 19 BAM and 15 WEM, matched for age, body mass index and duration of diabetes, we assessed and modelled insulin secretory responses to hyperglycaemia stimulated intravenously (hyperglycaemic clamp) and orally (meal tolerance test).ResultsWith similar post‐challenge glucose responses, BAM had lower second‐phase C‐peptide responses to intravenous glucose (BAM 70.6 vs WEM 115.1 nmol/L/min [ratio of geometric mean 0.55, 95% confidence interval {CI} 0.37, 0.83]; P = .006) and to oral glucose (BAM 65.4 vs WEM 88.5 nmol/L/min [mean difference −23.2, 95% CI −40.0, −6.3]; P = .009). Peripheral insulin response in BAM to oral glucose was preserved (BAM 47.4 vs WEM 59.4 nmol/L/min [ratio of geometric mean 0.89, 95% CI 0.59, 1.35]; P = .566), with relative reductions in insulin clearance (BAM 506.2 vs WEM 630.1 mL/m2 BSA/min [mean difference −123.9, 95% CI −270.5, 22.6]; P = .095), associated with enhanced incretin responses (gastric inhibitory polypeptide incremental area under the curve: BAM 46.8 vs WEM 33.9 μg/L/min [mean difference 12.9, 95% CI 2.1, 23.7]; P = .021).ConclusionsIn early T2D, BAM had significantly lower insulin secretory responses to intravenous and oral stimulation than WEM. Lower insulin clearance, potentially driven by increased incretin responses, may act to preserve peripheral insulin concentrations. Tailoring early management strategies to reflect distinct ethnic‐specific pathophysiology may improve outcomes in this high‐risk population.

Gut microbial dysbiosis is implicated in the pathogenesis of non-alcoholic steatohepatitis (NASH). We investigated downstream effects of gut microbiota modulation on markers of hepatic inflammation, steatosis, and hepatic and peripheral insulin sensitivity in patients with NASH using rifaximin therapy.Patients with biopsy-proven NASH and elevated aminotransferase values were included in this open-label pilot study, all receiving 6 weeks rifaximin 400 mg twice daily, followed by a 6-week observation period. The primary endpoint was change in alanine aminotransferase (ALT) after 6 weeks of rifaximin. Secondary endpoints were change in hepatic lipid content and insulin sensitivity measured with a hyperinsulinemic-euglycemic clamp.Fifteen patients (13 men and 2 women) with a median (range) age of 46 (32-63) years were included. Seven had diabetes on oral hypoglycemic medications and 8 had no diabetes. After 6 weeks of therapy, no differences were seen in ALT (55 [33-191] vs. 63 [41-218] IU/L, P = 0.41), peripheral glucose uptake (28.9 [19.4-48.3] to 25.5 [17.7-47.9] μmol/kg/min, P = 0.30), hepatic insulin sensitivity (35.2 [15.3-51.7]% vs. 30.0 [10.8-50.5]%, P = 0.47), or hepatic lipid content (21.6 [2.2-46.2]% vs. 24.8 [1.7-59.3]%, P = 0.59) before and after rifaximin treatment. After 12 weeks from baseline, serum ALT increased to 83 (30-217) IU/L, P = 0.02. There was a significant increase in the homeostasis model assessment-estimated insulin resistance index (P = 0.05). The urinary metabolic profile indicated a significant reduction in urinary hippurate with treatment, which reverted to baseline after cessation of rifaximin, although there was no consistent difference in relative abundance of fecal microbiota with treatment.These data do not indicate a beneficial effect of rifaximin in patients with NASH.

Dietary fructose has been linked to an increased post-prandial triglyceride (TG) level; which is an established independent risk factor for cardiovascular disease. Although much research has focused on the effects of fructose consumption on liver-derived very-low density lipoprotein (VLDL); emerging evidence also suggests that fructose may raise post-prandial TG levels by affecting the metabolism of enterocytes of the small intestine. Enterocytes have become well recognised for their ability to transiently store lipids following a meal and to thus control post-prandial TG levels according to the rate of chylomicron (CM) lipoprotein synthesis and secretion. The influence of fructose consumption on several aspects of enterocyte lipid metabolism are discussed; including de novo lipogenesis; apolipoprotein B48 and CM-TG production; based on the findings of animal and human isotopic tracer studies. Methodological issues affecting the interpretation of fructose studies conducted to date are highlighted; including the accurate separation of CM and VLDL. Although the available evidence to date is limited; disruption of enterocyte lipid metabolism may make a meaningful contribution to the hypertriglyceridaemia often associated with fructose consumption.

Nonalcoholic fatty liver disease (NAFLD) is an independent risk factor for cardiovascular disease (CVD). Endothelial dysfunction is an early manifestation of atherosclerosis and an important prognostic marker for future cardiovascular events. The aim of this study was twofold: to examine 1) the association between liver fat, visceral adipose tissue (VAT), and endothelial dysfunction in obese NAFLD patients and 2) the impact of supervised exercise training on this vascular defect. Brachial artery endothelial function was assessed by flow-mediated dilatation (FMD) in 34 obese NAFLD patients and 20 obese controls of similar age and cardiorespiratory fitness [peak oxygen uptake (V̇o2 peak)] (48 ± 2 vs. 47 ± 2 yr; 27 ± 1 vs. 26 ± 2 ml·kg−1·min−1−1). Magnetic resonance imaging and spectroscopy quantified abdominal and liver fat, respectively. Twenty-one NAFLD patients completed either 16 wk of supervised moderate-intensity exercise training ( n = 13) or conventional care ( n = 8). Differences between NAFLD and controls were compared using independent t-tests and effects of interventions by analysis of covariance. NAFLD patients had higher liver fat [11.6% (95% CI = 7.4, 18.1), P < 0.0005] and VAT [1.6 liters (95% CI = 1.2, 2.0), P < 0.0001] than controls and exhibited impaired FMD compared with controls [−3.6% (95% CI = −4.9, −2.2), P < 0.0001]. FMD was inversely correlated with VAT ( r = −0.54, P = 0.001) in NAFLD, although the impairment in FMD remained following covariate adjustment for VAT [3.1% (95% CI = 1.8, 4.5), P < 0.001]. Exercise training, but not conventional care, significantly improved V̇o2 peak [9.1 ml·kg−1·min−1 (95% CI = 4.1, 14.1); P = 0.001] and FMD [3.6% (95% CI = 1.6, 5.7), P = 0.002]. Endothelial dysfunction in NAFLD cannot be fully explained by excess VAT but can be reversed with exercise training; this has potential implications for the primary prevention of CVD in NAFLD.

Aims We aimed to assess ethnic differences in visceral adipose tissue (VAT), intrahepatic (IHL), intrapancreatic (IPL) and intramyocellular lipids (IMCL) between healthy white European (WE) and black west African (BWA) men. Methods 23 WE and 20 BWA men underwent Dixon-magnetic resonance imaging to quantify VAT, IHL and IPL; and proton-magnetic resonance spectroscopy to quantify IMCL. Insulin sensitivity and beta-cell function were determined using homeostasis model assessment (HOMA-2). Results BWA men exhibited significantly lower VAT (P = 0.021) and IHL (P = 0.044) than WE men, but comparable IPL (P = 0.92) and IMCL (P = 0.87). VAT was associated with IPL in both ethnicities (WE: P

This study aimed to 1) develop a method that completely separated hepatic (VLDL1, VLDL2) and intestinal [chylomicron (CM)] lipoproteins and 2) use the method to measure triacylglycerol (TAG) kinetics in these lipoproteins in the fed and fasting state in healthy subjects, using intravenous [2H5]glycerol as the tracer. An immunoaffinity method that completely separated hepatic and intestinal particles using sequential binding to three antibodies to apolipoprotein B-100 (apoB-100) was established and validated. Six healthy volunteers were studied in a fasted and continuous feeding study ( study 1). Five additional healthy volunteers were studied in a continuous feeding study that included an oral [13C3]glycerol tripalmitin tracer ( study 2). In both studies, an intravenous bolus of [2H5]glycerol was administered to label TAG in hepatic and intestinal lipoproteins. In both feeding studies there was sufficient incorporation of the [2H5]glycerol tracer into the exogenous lipoproteins to enable isotopic enrichment to be measured. In study 2, the oral tracer enrichment in VLDL1 was

OBJECTIVE Insulin detemir lacks the usual propensity for insulin to cause weight gain. We investigated whether this effect was a result of reduced energy intake and/or increased energy expenditure. RESEARCH DESIGN AND METHODS A 32-week, randomized crossover design trial was undertaken in 23 patients with type 1 diabetes. Patients on a basal-bolus regimen (with insulin aspart as the bolus insulin) were randomly assigned to insulin detemir or NPH insulin as a basal insulin for 16 weeks, followed by the other basal insulin for 16 weeks. At the end of each 16-week period, total energy expenditure, resting energy expenditure, diet-induced thermogenesis, activity energy expenditure, energy intake, weight change, glycemic control, hypoglycemic episodes, and hormones that affect satiety and fuel partitioning were measured. RESULTS After 16 weeks, weight change was −0.69 ± 1.85 kg with insulin detemir and +1.7 ± 2.46 kg with NPH insulin (P < 0.001). Total energy intake was significantly less with insulin detemir (2,016 ± 501 kcal/day) than with NPH insulin (2,181 ± 559 kcal/day) (P = 0.026). There was no significant difference in any measure of energy expenditure, HbA1c percentage, or number of hypoglycemic episodes. Leptin was lower and resistin was higher with insulin detemir compared with NPH insulin (P = 0.039, P = 0.047). After the meal, ghrelin and pancreatic polypeptide levels (P = 0.002, P = 0.001) were higher with insulin detemir. CONCLUSIONS The reduced weight gain with insulin detemir compared with NPH insulin is attributed to reduced energy intake rather than increased energy expenditure. This may be mediated by a direct or indirect effect of insulin detemir on the hormones that control satiety.

Although low-density lipoprotein (LDL) cholesterol is often normal in patients with type 2 diabetes mellitus, there is evidence for a reduced fractional catabolic rate and consequently an increased mean residence time (MRT), which can increase atherogenic risk. The dyslipidemia and insulin resistance of type 2 diabetes mellitus can be improved by aerobic exercise, but effects on LDL kinetics are unknown. The effect of 6-month supervised exercise on LDL apolipoprotein B kinetics was studied in a group of 17 patients with type 2 diabetes mellitus (mean age, 56.8 years; range, 38-68 years). Patients were randomized into a supervised group, who had a weekly training session, and an unsupervised group. LDL kinetics were measured with an infusion of 1-(13)C leucine at baseline in all groups and after 6 months of exercise in the patients. Eight body mass index-matched nondiabetic controls (mean age, 50.3 years; range, 40-67 years) were also studied at baseline only. At baseline, LDL MRT was significantly longer in the diabetic patients, whereas LDL production rate and fractional clearance rates were significantly lower than in controls. Percentage of glycated hemoglobin A(1c), body mass index, insulin sensitivity measured by the homeostasis model assessment, and very low-density lipoprotein triglyceride decreased (P < .02) in the supervised group, with no change in the unsupervised group. After 6 months, LDL cholesterol did not change in either the supervised or unsupervised group; but there was a significant change in LDL MRT between groups (P < .05) that correlated positively with very low-density lipoprotein triglyceride (r = 0.51, P < .04) and negatively with maximal oxygen uptake, a measure of fitness (r = -0.51, P = .035), in all patients. The LDL production and clearance rates did not change in either group. This study suggests that a supervised exercise program can reduce deleterious changes in LDL MRT.

Context: Chronic pharmacological glucocorticoid (GC) use causes substantial morbidity from protein wasting. GH and androgens are anabolic agents that may potentially reverse GC-induced protein loss. Objective: Our objective was to assess the effect of GH and dehydroepiandrosterone (DHEA) on protein metabolism in subjects on long-term GC therapy. Design: This was an open, stepwise GH dose-finding study (study 1), followed by a randomized cross-over intervention study (study 2). Setting: The studies were performed at a clinical research facility. Patients and Intervention: In study 1, six subjects (age 69 ± 4 yr) treated with long-term (>6 months) GCs (prednisone dose 8.3 ± 0.8 mg/d) were studied before and after two sequential GH doses (0.8 and 1.6 mg/d) for 2 wk each. In study 2, 10 women (age 71 ± 3 yr) treated with long-term GCs (prednisone dose 5.4 ± 0.5 mg/d) were studied at baseline and after 2-wk treatment with GH 0.8 mg/d, DHEA 50 mg/d, or GH and DHEA (combination treatment). Main Outcome Measure: Changes in whole body protein metabolism were assessed using a 3-h primed constant infusion of 1-[13C]leucine, from which rates of leucine appearance, leucine oxidation, and leucine incorporation into protein were estimated. Results: In study 1, GH 0.8 and 1.6 mg/d significantly reduced leucine oxidation by 19% (P = 0.03) and 31% (P = 0.02), and increased leucine incorporation into protein by 10% (P = 0.13) and 19% (P = 0.04), respectively. The lower GH dose did not cause hyperglycemia, whereas GH 1.6 mg/d resulted in fasting hyperglycemia in two of six subjects. In study 2, DHEA did not significantly change leucine metabolism alone or when combined with GH. Blood glucose was not affected by DHEA. Conclusion: GH, at a modest supraphysiological dose of 0.8 mg/d, induces protein anabolism in chronic GC users without causing diabetes. DHEA 50 mg/d does not enhance the effect of GH. GH may safely prevent or reverse protein loss induced by chronic GC therapy.

Exercise is a potent stimulator of growth hormone (GH) secretion. We hypothesised that after a short bout of intense exercise GH may increase lipolysis during recovery. In 7 moderately trained young male subjects (21.8 +/- 0.5 years) and 7 moderately trained older male subjects (56.0 +/- 1.0 years) [(2)H(5)] glycerol was infused for 370min to measure glycerol production rate (R(a)), a measure of lipolysis. At 130 min subjects exercised on a cycle ergonometer for 20 min at 70% V(O2 max), followed by rest for 220 min. On a separate occasion the study was repeated in the young subjects with a 1h GH infusion (4microgkg(-1)h(-1)) at 130 min instead of exercise. In response to exercise, catecholamines (p0.02) and glycerol R(a) (p0.01) increased, peaking during exercise. GH concentration increased in response to exercise (p0.01), peaking after exercise (150-160 min) in both groups with no significant difference in peak response between groups. A post-exercise rise in glycerol R(a) was demonstrated in both groups peaking at 265-295 min in the older group (p0.002, peak vs. basal) and continuing to rise until 370 min in the young group (p0.01, peak vs. basal). The timing and magnitude of this was reproduced with the GH infusion. There was a significant correlation between the peak GH response to exercise and the post-exercise rise in glycerol R(a) measured as area under the curve (r=0.57, p0.04). In conclusion, this study provides evidence that the GH response to acute exercise may increase lipolysis during recovery.

We investigated the impact of growth hormone (GH) alone, testosterone (T) alone, and combined GH and T on whole body protein metabolism. Twelve hypopituitary men participated in two studies. Study 1 compared the effects of GH alone with GH plus T, and study 2 compared the effects of T alone with GH plus T. IGF-I, resting energy expenditure (REE), and fat oxidation (Fox) and rates of whole body leucine appearance (Ra), oxidation (Lox), and nonoxidative leucine disposal (NOLD) were measured. In study 1, GH treatment increased mean plasma IGF-I ( P < 0.001). GH did not change leucine Ra but reduced Lox ( P < 0.02) and increased NOLD ( P < 0.02). Addition of T resulted in an additional increase in IGF-I ( P < 0.05), reduction in Lox ( P < 0.002), and increase in NOLD ( P < 0.002). In study 2, T alone did not alter IGF-I levels. T alone did not change leucine Ra but reduced Lox ( P < 0.01) and increased NOLD ( P < 0.01). Addition of GH further reduced Lox ( P < 0.05) and increased NOLD ( P < 0.05). In both studies, combined treatments on REE and Fox were greater than either alone. In summary, GH-induced increase of circulating IGF-I is augmented by T, which does not increase IGF-I in the absence of GH. T and GH exerted independent and additive effects on protein metabolism, Fox and REE. The anabolic effects of T are independent of circulating IGF-I.

The relationship between antiretroviral treatment of HIV infection, body fat distribution, insulin resistance, and very-low-density lipoprotein (VLDL) and intermediate-density lipoprotein (IDL) apolipoprotein-B (apoB) kinetics was investigated in 55 HIV-infected patients taking two nucleoside analogs plus either a protease inhibitor (n = 15) or a nonnucleoside reverse transcriptase inhibitor (n = 25), 15 antiretroviral therapy-naive patients, and 12 HIV-negative controls. Compared with the controls, high-density lipoprotein cholesterol was reduced in all groups (P < 0.01). Plasma triglyceride was increased in patients taking protease inhibitors (P < 0.05). VLDL and IDL apoB fractional catabolic rate (FCR) was lower in all treatment groups (P < 0.05) compared with controls. Trunk fat, VLDL apoB absolute secretion rate, and insulin resistance were not different between groups. Peripheral fat was lower in the treated patients (P < 0.05) and correlated with duration of therapy (r = -0.55; P < 0.001). There was a positive correlation between peripheral fat and VLDL apoB FCR (P = 0.002) and IDL apoB FCR (P = 0.002) and a negative correlation with VLDL apoB pool size, VLDL cholesterol, and triglyceride (P < 0.03; P < 0.01; P < 0.002). These results suggest that mild dyslipidemia resulting from antiretroviral therapy is caused by a decrease in VLDL and IDL apoB FCR, which is associated with a loss of peripheral fat.

Inherited defects in signaling pathways downstream of the insulin receptor have long been suggested to contribute to human type 2 diabetes mellitus. Here we describe a mutation in the gene encoding the protein kinase AKT2/PKBβ in a family that shows autosomal dominant inheritance of severe insulin resistance and diabetes mellitus. Expression of the mutant kinase in cultured cells disrupted insulin signaling to metabolic end points and inhibited the function of coexpressed, wild-type AKT. These findings demonstrate the central importance of AKT signaling to insulin sensitivity in humans.

Protein loss leading to reduced lean body mass is recognized to contribute to the high levels of morbidity and mortality seen in critical illness. This prospective, randomized, controlled study compared the effects of conventional parenteral nutrition (TPN), glutamine-supplemented (0.4 g·kg-1·day-1) TPN (TPNGLN), and TPNGLN with combined growth hormone (GH, 0.2 IU·kg-1·day-1) and IGF-I (160 μg·kg-1·day-1) on protein metabolism in critical illness. Nineteen mechanically ventilated subjects [64 ± 3 yr, body mass index (BMI) 23.8 ± 1.3, kg/m2] were initially studied in the fasting state ( study 1) and subsequently after 3 days of nutritional with/without hormonal support ( study 2). All had recently been admitted to the ICU and the majority were postemergency abdominal surgery (APACHE II 17.5 ± 1.0). Protein metabolism was assessed using a primed constant infusion of [1-13C]leucine. Conventional TPN contained mixed amino acids, Intralipid, and 50% dextrose. TPNGLN, unlike TPN alone, resulted in an increase in plasma glutamine concentration (∼50%, P < 0.05). Both TPN and TPNGLN decreased the rate of protein breakdown (TPN 15%, P < 0.002; TPNGLN 16%, P < 0.05), but during these treatments the patients remained in a net negative protein balance. Combined treatment with TPNGLN + GH/IGF-I increased plasma IGF-I levels (10.3 ± 0.8 vs. 48.1 ± 9.1 nmol/l, study 1 vs. study 2, P < 0.05), and in contrast to therapy with nutrition alone, resulted in net protein gain (-0.75 ± 0.14 vs. 0.33 ± 0.12 g protein·kg-1·day-1, study 1 vs. study 2, P < 0.05). Therapy with GH/IGF-I + TPNGLN, unlike nutrition alone, resulted in net positive protein balance in a group of critically ill patients.

We previously reported a syndrome of severe hyperinsulinemia and early-onset hypertension in three patients with dominant-negative mutations in the nuclear hormone receptor peroxisome proliferator-activated receptor (PPAR)-γ. We now report the results of further detailed pathophysiological evaluation of these subjects, the identification of affected prepubertal children within one of the original families, and the effects of thiazolidinedione therapy in two subjects. These studies 1) definitively demonstrate the presence of severe peripheral and hepatic insulin resistance in the affected subjects; 2) describe a stereotyped pattern of partial lipodystrophy associated with all the features of the metabolic syndrome and nonalcoholic steatohepatitis; 3) document abnormalities in the in vivo function of remaining adipose tissue, including the inability of subcutaneous abdominal adipose tissue to trap and store free fatty acids postprandially and the presence of very low circulating levels of adiponectin; 4) document the presence of severe hyperinsulinemia in prepubertal carriers of the proline-467-leucine (P467L) PPAR-γ mutation; 5) provide the first direct evidence of cellular resistance to PPAR-γ agonists in mononuclear cells derived from the patients; and 6) report on the metabolic response to thiazolidinedione therapy in two affected subjects. Although the condition is rare, the study of humans with dominant-negative mutations in PPAR-γ can provide important insight into the roles of this nuclear receptor in human metabolism.

We have separated the effect of insulin on glucose distribution/transport, glucose disposal, and endogenous production (EGP) during an intravenous glucose tolerance test (IVGTT) by use of a dual-tracer dilution methodology. Six healthy lean male subjects (age 33 ± 3 yr, body mass index 22.7 ± 0.6 kg/m2) underwent a 4-h IVGTT (0.3 g/kg glucose enriched with 3–6% d-[U-13C]glucose and 5–10% 3- O-methyl-d-glucose) preceded by a 2-h investigation under basal conditions (5 mg/kg ofd-[U-13C]glucose and 8 mg/kg of 3- O-methyl-d-glucose). A new model described the kinetics of the two glucose tracers and native glucose with the use of a two-compartment structure for glucose and a one-compartment structure for insulin effects. Insulin sensitivities of distribution/transport, disposal, and EGP were similar (11.5 ± 3.8 vs. 10.4 ± 3.9 vs. 11.1 ± 2.7 × 10−2ml · kg−1· min−1per mU/l; P = nonsignificant, ANOVA). When expressed in terms of ability to lower glucose concentration, stimulation of disposal and stimulation of distribution/transport accounted each independently for 25 and 30%, respectively, of the overall effect. Suppression of EGP was more effective ( P < 0.01, ANOVA) and accounted for 50% of the overall effect. EGP was suppressed by 70% (52–82%) (95% confidence interval relative to basal) within 60 min of the IVGTT; glucose distribution/transport was least responsive to insulin and was maximally activated by 62% (34–96%) above basal at 80 min compared with maximum 279% (116–565%) activation of glucose disposal at 20 min. The deactivation of glucose distribution/transport was slower than that of glucose disposal and EGP ( P < 0.02) with half-times of 207 (84–510), 12 (7–22), and 29 (16–54) min, respectively. The minimal-model insulin sensitivity was tightly correlated with and linearly related to sensitivity of EGP ( r = 0.96, P < 0.005) and correlated positively but nonsignificantly with distribution/transport sensitivity ( r = 0.73, P = 0.10) and disposal sensitivity ( r = 0.55, P = 0.26). We conclude that, in healthy subjects during an IVGTT, the two peripheral insulin effects account jointly for approximately one-half of the overall insulin-stimulated glucose lowering, each effect contributing equally. Suppression of EGP matches the effect in the periphery.

Context and objective: No current biomarker can reliably predict visceral and liver fat content, both of which are risk factors for cardiovascular disease. Vagal tone has been suggested to influence regional fat deposition. Pancreatic polypeptide (PP) is secreted from the endocrine pancreas under vagal control. We investigated the utility of PP in predicting visceral and liver fat. Patients and Methods: Fasting plasma PP concentrations were measured in 104 overweight and obese subjects (46 men and 58 women). In the same subjects, total and regional adipose tissue, including total visceral adipose tissue (VAT) and total subcutaneous adipose tissue (TSAT), were measured using whole-body magnetic resonance imaging. Intrahepatocellular lipid content (IHCL) was quantified by proton magnetic resonance spectroscopy. Results: Fasting plasma PP concentrations positively and significantly correlated with both VAT (r = 0.57, P < .001) and IHCL (r = 0.51, P < .001), but not with TSAT (r = 0.02, P = .88). Fasting PP concentrations independently predicted VAT after controlling for age and sex. Fasting PP concentrations independently predicted IHCL after controlling for age, sex, body mass index (BMI), waist-to-hip ratio, homeostatic model assessment 2-insulin resistance, (HOMA2-IR) and serum concentrations of triglyceride (TG), total cholesterol (TC), and alanine aminotransferase (ALT). Fasting PP concentrations were associated with serum ALT, TG, TC, low- and high-density lipoprotein cholesterol, and blood pressure (P < .05). These associations were mediated by IHCL and/or VAT. Fasting PP and HOMA2-IR were independently significantly associated with hepatic steatosis (P < .01). Conclusions: Pancreatic polypeptide is a novel predictor of visceral and liver fat content, and thus a potential biomarker for cardiovascular risk stratification and targeted treatment of patients with ectopic fat deposition.

We have determined whether oral estrogen reduces the biological effects of growth hormone (GH) in GH-deficient (GHD) women compared with transdermal estrogen treatment. In two separate studies, eight GHD women randomly received either oral or transdermal estrogen for 8 wk before crossing over to the alternate route of administration. The first study assessed the effects of incremental doses of GH (0.5, 1.0, 2.0 IU/day for 1 wk each) on insulin-like growth factor I (IGF-I) levels during each estrogen treatment phase. The second study assessed the effects of GH (2 IU/day) on lipid oxidation and on protein metabolism using the whole body leucine turnover technique. Mean IGF-I level was significantly lower during oral estrogen treatment ( P < 0.05) and rose dose dependently during GH administration by a lesser magnitude ( P < 0.05) compared with transdermal treatment. Postprandial lipid oxidation was significantly lower with oral estrogen treatment, both before ( P < 0.05) and during ( P < 0.05) GH administration, compared with transdermal treatment. Protein synthesis was lower during oral estrogen both before and during GH administration ( P < 0.05). Oral estrogen antagonizes several of the metabolic actions of GH. It may aggravate body composition abnormalities already present in GHD women and attenuate the beneficial effects of GH therapy. Estrogen replacement in GHD women should be administered by a nonoral route.

The extent of the renal contribution to postabsorptive endogenous glucose production (EGP) in humans is controversial. We measured EGP in the absence of the liver during the anhepatic phase (AH) of liver transplantation in five patients (aged 46.4+/-10.2 years, two women). Stable labeling of plasma glucose (PG) was achieved for a 2-h period before the AH by primed continuous infusion of di-deuterated 6,6[2H2]glucose (1.7 mg/min) and continued throughout the AH. PG was maintained above the fasting level (6.1+/-2.73 mmol/l) with 5% dextrose labeled with 6,6[2H2]glucose throughout the AH (mean level during the AH 0.98+/-0.45 mg x kg(-1) x min(-1)). Isotopic enrichment remained stable at 0.84+/-0.21% atom percent excess throughout. EGP, calculated by use of a modified Steele equation, decreased from 2.6+/-1.24 at baseline to 0.97+/-0.9 mg x kg(-1) x min(-1) (36% baseline, P = 0.045) but recovered at approximately 30 min to reach 1.38+/-0.83 mg x kg(-1) x min(-1) (54% baseline) by 60 min. Epinephrine, lactate, free fatty acid, and glycerol levels increased significantly (0.79+/-0.74 to 3.65+/-2.1 nmol/l, P = 0.005; 1.88+/-0.43 to 3.46+/-0.9 mmol/l, P = 0.024; 543.9+/-215.5 to 705.5+/-219.2 micromol/l, P = 0.012; 75.6+/-30.2 to 139+/-96.3 micromol/l, P = 0.003, respectively). These data show that postabsorptive nonhepatic glucose production in humans may contribute to greater than one-third of overall EGP, increasing when required, and that it is associated with a stress response and increased gluconeogenic substrate availability. We conclude that extrahepatic tissues, most notably those of the kidney, make a significant contribution to EGP in humans.

OBJECTIVE Insulin-like growth factor-I (IGF-I) has both insulin-like and anabolic actions but unlike insulin, IGF-I circulates bound to a number of specific binding proteins that regulate its availability and activity. Patients with type 1 diabetes mellitus have low levels of circulating IGF-I despite increased growth hormone (GH) secretion, and are a group that may benefit from rhIGF-I therapy. Understanding the relationship between IGF-I and its binding proteins is necessary to appreciate the actions of exogenously administered rhIGF-I. Therefore, we examined the effects of 19 days' subcutaneous administration of rhIGF-I (50 μg/kg BID) on the levels of IGF-I, IGF-II and the IGF-binding proteins (IGFBPs), as well as the daily dose of insulin necessary to maintain glycaemic control in patients with type 1 diabetes mellitus. DESIGN AND PATIENTS This was an open study, and the patients were studied initially while resident (days 1–5) in the hospital and thereafter (days 6–24) as outpatients. Serum was collected at baseline and at intervals throughout the study for the measurement of total IGF-I, IGF-II, IGFBP-1, -2, -3, free insulin and growth hormone (GH). Daily insulin doses and glucometer readings were recorded throughout the study. The changes in each of these variables were examined. The subjects were six adults (35.3 ± 4.0 years, mean ± SE), with type 1 diabetes, and all had reasonable glycaemic control (HbA1c 7.2 ± 0.5%). RESULTS rhIGF-I administration increased circulating total IGF-I over two-fold (15.3 ± 1.9 vs. 33.7 ± 5.4 nmol/l, mean ± SEM, P