Exercise-induced improvements in liver fat and endothelial function are not sustained 12 months following cessation of exercise supervision in nonalcoholic fatty liver disease.

Supervised exercise reduces liver fat and improves endothelial function, a surrogate of cardiovascular disease (CVD) risk, in nonalcoholic fatty liver disease (NAFLD). We hypothesised that after a 16-week supervised exercise program, patients would maintain longer-term improvements in cardiorespiratory fitness, liver fat and endothelial function. Ten NAFLD patients (5/5 males/females, age 51±13 years, body mass index 31±3 kg m-2 (mean±s.d.)) underwent a 16-week supervised moderate-intensity exercise intervention. Biochemical markers, cardiorespiratory fitness (VO2peak), subcutaneous, visceral and liver fat (measured by magnetic resonance imaging and spectroscopy respectively) and brachial artery flow-mediated dilation (FMD) were assessed at baseline, after 16 weeks of supervised training and 12 months after ending supervision. Despite no significant change in body weight, there were significant improvements in VO2peak (6.5 ml kg-1 min-1 (95% confidence interval 2.8, 10.1); P=0.003), FMD (2.9% (1.5, 4.2); P=0.001), liver transaminases (P<0.05) and liver fat (-10.1% (-20.6, 0.5); P=0.048) immediately after the 16-week supervised training. Nevertheless, 12 months after ending supervision, VO2peak (0.9 ml kg-1 min-1 (-3.3, 5.1); P=0.65), FMD (-0.07% (-2.3, 2.2); P=0.95), liver transaminases (P>0.05) and liver fat (1.4% (-13.0, 15.9); P=0.83) were not significantly different from baseline. At 12 months following cessation of supervision, exercise-mediated improvements in liver fat and other cardiometabolic variables had reversed with cardiorespiratory fitness at baseline levels. Maintenance of high cardiorespiratory fitness and stability of body weight are critical public health considerations for the treatment of NAFLD (Clinicaltrials.gov identifier: NCT01834300).

Effect of subcutaneous insulin detemir on glucose flux and lipolysis during hyperglycaemia in people with type 1 diabetes.

AIMS: To investigate, using a novel non-steady-state protocol, the differential effects of subcutaneous (s.c.) detemir and NPH insulin on glucose flux and lipid metabolism after insulin withdrawal. METHODS: After a period of insulin withdrawal resulting in whole-blood glucose concentration of 7 mmol/l, 11 participants (five men, mean age 41.0 years, mean body mass index 25 kg/m(2)) with type 1 diabetes (mean glycated haemoglobin concentration 57 mmol/mol, mean diabetes duration 14 years) received 0.5 units per kg body weight s.c. insulin detemir or NPH insulin in random order. Stable isotopes of glucose and glycerol were infused intravenously throughout the study protocol. RESULTS: Glucose concentration decreased after insulin treatment as a result of suppression of endogenous glucose production, which occurred to a similar extent with both detemir and NPH insulin. The rate of glucose disappearance (Rd) was not increased significantly with either type of insulin. When the effect of detemir and NPH insulin on glucose flux at glucose concentrations between 9 and 6 mmol/l was examined, glucose rate of appearance (Ra) was similar with the two insulins; however, glucose Rd was greater with NPH insulin than with detemir at glucose concentrations of 8.0, 8.5, 7.0 and 6.0 mmol/l (p < 0.05) The percentage change in glycerol Ra, a measure of lipolysis, was greater in the NPH group than in the detemir group (p = 0.04). CONCLUSIONS: The results of the study are consistent with the hypothesis that detemir has a lesser effect on the periphery, as evidenced by a lesser effect on peripheral glucose uptake at specific glucose concentrations.

Effect of subcutaneous insulin detemir on glucose flux, lipolysis and electroencephalography in type 1 diabetes.

The aim of the present study was to investigate the effects of subcutaneous detemir on glucose flux, lipid metabolism and brain function. Twelve people with type 1 diabetes received, in random order, 0.5 units/kg body weight detemir or NPH insulin. Glucose concentration was clamped at 5 mmol/l then increased to 10 mmol/l. Glucose production rate (glucose Ra), glucose uptake (glucose Rd) and glycerol production (glycerol Ra) were measured with a constant intravenous infusion of [6,6(2) H(2)]glucose and [(2)H(5)]glycerol. Electroencephalography direct current (DC) and alternating current (AC) potentials were measured. While detemir induced similar effects on glucose Ra, glucose Rd and glycerol Ra during euglycaemia compared with NPH, it triggered a distinct negative shift in DC potentials, with a significant treatment effect in frontal cerebrocortical channels (p < 0.001). AC spectral power showed significant differences in theta and alpha frequencies during euglycaemia (p = 0.03). Subcutaneous detemir exerts different effects on brain function when compared with NPH in people with type 1 diabetes. This may be an important mechanism behind the limitation of weight gain with detemir.

Safety, efficacy and glucose turnover of reduced prandial boluses during closed-loop therapy in adolescents with type 1 diabetes: a randomized clinical trial.

AIMS: To evaluate safety, efficacy and glucose turnover during closed-loop with meal announcement using reduced prandial insulin boluses in adolescents with type 1 diabetes (T1D). METHODS: We conducted a randomized crossover study comparing closed-loop therapy with standard prandial insulin boluses versus closed-loop therapy with prandial boluses reduced by 25%. Eight adolescents with T1D [3 males; mean (standard deviation) age 15.9 (1.5) years, glycated haemoglobin 74 (17) mmol/mol; median (interquartile range) total daily dose 0.9 (0.7, 1.1) IU/kg/day] were studied on two 36-h-long visits. In random order, subjects received closed-loop therapy with either standard or reduced insulin boluses administered with main meals (50-80 g carbohydrates) but not with snacks (15-30 g carbohydrates). Stable-label tracer dilution methodology measured total glucose appearance (Ra_total) and glucose disposal (Rd). RESULTS: The median (interquartile range) time spent in target (3.9-10 mmol/l) was similar between the two interventions [74 (66, 84)% vs 80 (65, 96)%; p = 0.87] as was time spent above 10 mmol/l [21.8 (16.3, 33.5)% vs 18.0 (4.1, 34.2)%; p = 0.87] and below 3.9 mmol/l [0 (0, 1.5)% vs 0 (0, 1.8)%; p = 0.88]. Mean plasma glucose was identical during the two interventions [8.4 (0.9) mmol/l; p = 0.98]. Hypoglycaemia occurred once 1.5 h post-meal during closed-loop therapy with standard bolus. Overall insulin delivery was lower with reduced prandial boluses [61.9 (55.2, 75.0) vs 72.5 (63.6, 80.3) IU; p = 0.01] and resulted in lower mean plasma insulin concentration [186 (171, 260) vs 252 (198, 336) pmol/l; p = 0.002]. Lower plasma insulin was also documented overnight [160 (136, 192) vs 191 (133, 252) pmol/l; p = 0.01, pooled nights]. Ra_total was similar [26.3 (21.9, 28.0) vs 25.4 (21.0, 29.2) µmol/kg/min; p = 0.19] during the two interventions as was Rd [25.8 (21.0, 26.9) vs 25.2 (21.2, 28.8) µmol/kg/min; p = 0.46]. CONCLUSIONS: A 25% reduction in prandial boluses during closed-loop therapy maintains similar glucose control in adolescents with T1D whilst lowering overall plasma insulin levels. It remains unclear whether closed-loop therapy with a 25% reduction in prandial boluses would prevent postprandial hypoglycaemia.

Absorption patterns of meals containing complex carbohydrates in type 1 diabetes.

AIMS/HYPOTHESIS: Successful postprandial glycaemia management requires understanding of absorption patterns after meals containing variable complex carbohydrates. We studied eight young participants with type 1 diabetes to investigate a large low-glycaemic-load (LG) meal and another eight participants to investigate a high-glycaemic-load (HG) meal matched for carbohydrates (121 g). METHODS: On Visit 1, participants consumed an evening meal. On follow-up Visit 2, a variable-target glucose clamp was performed to reproduce glucose and insulin levels from Visit 1. Adopting stable-label tracer dilution methodology, we measured endogenous glucose production on Visit 2 and subtracted it from total glucose appearance measured on Visit 1 to obtain meal-attributable glucose appearance. RESULTS: After the LG meal, 25%, 50% and 75% of cumulative glucose appearance was at 88 ± 21, 175 ± 39 and 270 ± 54 min (mean ± SD), whereas glucose from the HG meal appeared significantly faster at 56 ± 12, 100 ± 25 and 153 ± 39 min (p < 0.001 to 0.003), and resulted in a 50% higher peak appearance (p < 0.001). Higher apparent bioavailability by 15% (p = 0.037) was observed after the LG meal. We documented a 20 min deceleration of dietary mixed carbohydrates compared with dietary glucose for the HG meal and a twofold deceleration for the LG meal. CONCLUSIONS/INTERPRETATION: Absorption patterns may be influenced by glycaemic load and/or meal composition, affecting optimum prandial insulin dosing in type 1 diabetes.

Pathophysiology of postprandial hyperglycaemia in women with type 1 diabetes during pregnancy.

AIMS/HYPOTHESIS: Although maternal hyperglycaemia is associated with increased risk of adverse pregnancy outcome, the mechanisms of postprandial hyperglycaemia during pregnancy are poorly understood. We aimed to describe glucose turnover in pregnant women with type 1 diabetes, according to stage of gestation (early vs late gestation). METHODS: The rates of systemic glucose appearance (R(a)) and glucose disposal (R(d)) were measured in ten pregnant women with type 1 diabetes during early (12-16 weeks) and late (28-32 weeks) gestation. Women ate standardised meals--a starch-rich 80 g carbohydrate dinner and a sugar-rich 60 g carbohydrate breakfast--and fasted between meals and overnight. Stable-label isotope tracers ([6,6-(2)H(2)]glucose and [U-(13)C]glucose) were used to determine R(a), R(d) and glucose bioavailability. Closed-loop insulin delivery maintained stable glycaemic conditions. RESULTS: There were no changes in fasting R(a) (10 ± 2 vs 11 ± 2 µmol kg(-1) min(-1); p = 0.32) or fasting R(d) (11 ± 2 vs 11 ± 1 µmol kg(-1) min(-1); p = 0.77) in early vs late gestation. There was increased hepatic insulin resistance (381 ± 237 vs 540 ± 242 µmol kg(-1) min(-1) × pmol/l; p = 0.04) and decreased peripheral insulin sensitivity (0.09 ± 0.04 vs 0.05 ± 0.02 µmol kg(-1) min(-1) per pmol/l dinner, 0.11 ± 0.05 vs 0.07 ± 0.03 µmol kg(-1) min(-1) per pmol/l breakfast; p = 0.002) in late gestation. It also took longer for insulin levels to reach maximal concentrations (49 [37-55] vs 71 [52-108] min; p = 0.004) with significantly delayed glucose disposal (108 [87-125] vs 135 [110-158] min; p = 0.005) in late gestation. CONCLUSIONS/INTERPRETATION: Postprandial glucose control is impaired by significantly slower glucose disposal in late gestation. Early prandial insulin dosing may help to accelerate glucose disposal and potentially ameliorate postprandial hyperglycaemia in late pregnancy. TRIAL REGISTRATION: ISRCTN 62568875 FUNDING: Diabetes UK Project Grant BDA 07/003551. H.R. Murphy is funded by a National Institute for Health Research (NIHR) research fellowship (PDF/08/01/036). Supported also by the Juvenile Diabetes Research Foundation (JDRF), Abbott Diabetes Care (Freestyle Navigator CGM and sensors free of charge), Medical Research Council Centre for Obesity and Related Metabolic Diseases and NIHR Cambridge Biomedical Research Centre.

Validity of triple- and dual-tracer techniques to estimate glucose appearance.

The triple-tracer (TT) dilution technique has been proposed to be the gold standard method to measure postprandial glucose appearance. However, validation against an independent standard has been missing. We addressed this issue and also validated the simpler dual-tracer (DT) technique. Sixteen young subjects with type 1 diabetes (age 19.5 ± 3.8 yr, BMI 23.4 ± 1.5 kg/m(2), HbA(1c) 8.7 ± 1.7%, diabetes duration 9.0 ± 6.9 yr, total daily insulin 0.9 ± 0.2 U·kg(-1)·day(-1), mean ± SD) received a variable intravenous 20% dextrose infusion enriched with [U-(13)C]glucose over 8 h to achieve postprandial-resembling glucose excursions while intravenous insulin was administered to achieve postprandial-resembling levels of plasma insulin. Primed [6,6-(2)H(2)]glucose was infused in a manner that mimicked the expected endogenous glucose production and [U-(13)C; 1,2,3,4,5,6,6-(2)H(7)]glucose was infused in a manner that mimicked the expected glucose appearance from a standard meal. Plasma glucose enrichment was measured by gas chromatography-mass spectrometry. The intravenous dextrose infusion served as an independent standard and was reconstructed using the TT and DT techniques with the two-compartment Radziuk/Mari model and an advanced stochastic computational method. The difference between the infused and reconstructed dextrose profile was similar for the two methods (root mean square error 6.6 ± 1.9 vs. 8.0 ± 3.5 µmol·kg(-1)·min(-1), TT vs. DT, P = NS, paired t-test). The TT technique was more accurate in recovering the overall dextrose infusion (100 ± 9 and 92 ± 12%; P = 0.02). The root mean square error associated with the mean dextrose infusion profile was 2.5 and 3.3 µmol·kg(-1)·min(-1) for the TT and DT techniques, respectively. We conclude that the TT and DT techniques combined with the advanced computational method can measure accurately exogenous glucose appearance. The TT technique tends to outperform slightly the DT technique, but the latter benefits from reduced experimental and computational complexity.

Metabolic effects of intensive insulin therapy in critically ill patients.

Our aim was to investigate the effects of glycemic control and insulin concentration on lipolysis, glucose, and protein metabolism in critically ill medical patients. For our methods, the patients were studied twice. In study 1, blood glucose (BG) concentrations were maintained between 7 and 9 mmol/l with intravenous insulin. After study 1, patients entered one of four protocols for 48 h until study 2: low-insulin high-glucose (LIHG; variable insulin, BG of 7-9 mmol/l), low-insulin low-glucose (LILG; variable insulin of BG 4-6 mmol/l), high-insulin high-glucose [HIHG; insulin (2.0 mU . kg(-1).min(-1) plus insulin requirement from study 1), BG of 7-9 mmol/l], or high-insulin low-glucose [HILG; insulin (2.0 mU.kg(-1).min(-1) plus insulin requirement from study 1), BG of 4-6 mmol/l]. Age-matched healthy control subjects received two-step euglycemic hyperinsulinemic clamps achieving insulin levels similar to the LI and HI groups. In our results, whole body proteolysis was higher in patients in study 1 (P < 0.006) compared with control subjects at comparable insulin concentrations and was reduced with LI (P < 0.01) and HI (P = 0.001) in control subjects but not in patients. Endogenous glucose production rate (R(a)), glucose disposal, and lipolysis were not different in all patients in study 1 compared with control subjects at comparable insulin concentrations. Glucose R(a) and lipolysis did not change in any of the study 2 patient groups. HI increased glucose disposal in the patients (HIHG, P = 0.001; HILG, P = 0.07 vs. study 1), but this was less than in controls receiving HI (P < 0.03). In conclusion, low-dose intravenous insulin administered to maintain BG between 7-9 mmol/l is sufficient to limit lipolysis and endogenous glucose R(a) and increase glucose R(d). Neither hyperinsulinemia nor normoglycemia had any protein-sparing effect.

Differential effects of insulin detemir and neutral protamine Hagedorn (NPH) insulin on hepatic glucose production and peripheral glucose uptake during hypoglycaemia in type 1 diabetes.

AIMS/HYPOTHESIS: We compared the symptoms of hypoglycaemia induced by insulin detemir (NN304) (B29Lys(epsilon-tetradecanoyl),desB30 human insulin) and equally effective doses of neutral protamine Hagedorn (NPH) insulin in relation to possible differential effects on hepatic glucose production and peripheral glucose uptake. METHODS: After overnight intravenous infusion of soluble human insulin 18 participants with type 1 diabetes received subcutaneous injections of NPH insulin or insulin detemir (0.5 U/kg body weight) on separate occasions in random order. During the ensuing gradual development of hypoglycaemia cognitive function and levels of counter-regulatory hormones were measured and rates of endogenous glucose production and peripheral glucose uptake continuously evaluated using a primed constant infusion of [6,6-(2)H(2)]glucose. The study was terminated when plasma glucose concentration had fallen to 2.4 mmol/l or had reached a minimum at a higher concentration. RESULTS: During the development of hypoglycaemia no difference between the two insulin preparations was observed in symptoms or hormonal responses. Significant differences were seen in rates of glucose flux. At and below plasma glucose concentrations of 3.5 mmol/l suppression of endogenous glucose production was greater with insulin detemir than with NPH insulin, whereas stimulation of peripheral glucose uptake was greater with NPH insulin than with insulin detemir. CONCLUSIONS/INTERPRETATION: In participants with type 1 diabetes subcutaneously injected insulin detemir exhibits relative hepatoselectivity compared with NPH insulin, but symptoms of hypoglycaemia and hormonal counter-regulation are similar. TRIAL REGISTRATION: ClinicalTrials.gov NCT00760448.

Effects of rosiglitazone and pioglitazone on lipoprotein metabolism in patients with Type 2 diabetes and normal lipids.

AIMS: Previous studies have suggested that plasma lipids are affected differently by the peroxisome proliferators-activated receptor (PPAR)-gamma agonists pioglitazone and rosiglitazone. The aim of this study was to perform a quantitative lipoprotein turnover study to determine the effects of PPAR-gamma agonists on lipoprotein metabolism. METHODS: Twenty-four subjects with Type 2 diabetes treated with diet and/or metformin were randomized in a double-blind study to receive 30 mg pioglitazone, 8 mg rosiglitazone or placebo once daily for 3 months. Before and after treatment, absolute secretion rate (ASR) and fractional catabolic rate (FCR) of very low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL) and low-density lipoprotein (LDL) apolipoprotein B100 were measured with a 10-h infusion of 1-13C leucine. RESULTS: There was a significant decrease in glycated haemoglobin (HbA(1c)) and non-esterified fatty acids with pioglitazone (P = 0.01; P = 0.02) and rosiglitazone (P = 0.04; P = 0.003), respectively, but no change in plasma triglyceride or high-density lipoprotein (HDL) cholesterol. Following rosiglitazone, there was a significant reduction in VLDL apolipoprotein B100 (apoB) ASR (P = 0.01) compared with baseline, a decrease in VLDL triglyceride/apoB (P = 0.01), an increase in LDL2 cholesterol (P = 0.02) and a decrease in LDL3 cholesterol (P = 0.02). There was a decrease in VLDL triglyceride/apoB (P = 0.04) in the pioglitazone group. There was no significant difference in change in VLDL ASR or FCR among the three groups. CONCLUSIONS: In patients with Type 2 diabetes and normal lipids, treatment with rosiglitazone or pioglitazone had no significant effect on lipoprotein metabolism compared with placebo.

Leucine-enriched essential amino acid supplementation in mechanically ventilated trauma patients: a feasibility study.

BACKGROUND: Critically ill patients lose up to 2% of muscle mass per day. We assessed the feasibility of administering a leucine-enriched essential amino acid (L-EAA) supplement to mechanically ventilated trauma patients with the aim of assessing the effect on skeletal muscle mass and function. METHODS: A randomised feasibility study was performed over six months in intensive care (ICU). Patients received 5 g L-EAA five times per day in addition to standard feed (L-EAA group) or standard feed only (control group) for up to 14 days. C-reactive protein, albumin, IL-6, IL-10, urinary 3-MH, nitrogen balance, protein turnover ([1-13C] leucine infusion), muscle depth change (ultrasound), functional change (Katz and Barthel indices) and muscle strength Medical Research Council (MRC) sum score to assess ICU Acquired Weakness were measured sequentially. RESULTS: Eight patients (9.5% of screened patients) were recruited over six months. L-EAA doses were provided on 91/124 (73%) occasions. Inflammatory and urinary marker data were collected; serial muscle depth measurements were lacking due to short length of stay. Protein turnover studies were performed on five occasions. MRC sum score could not be performed as patients were not able to respond to the screening questions. The Katz and Barthel indices did not change. L-EAA delivery was achievable, but meaningful functional and muscle mass outcome measures require careful consideration in the design of a future randomised controlled trial. CONCLUSION: L-EAA was practical to provide, but we found significant barriers to recruitment and measurement of the chosen outcomes which would need to be addressed in the design of a future, large randomised controlled trial. TRIAL REGISTRATION: ISRCTN Registry, ISRCTN79066838 . Registered on 25 July 2012.

Severe intrauterine growth retardation and atypical diabetes associated with a translocation breakpoint disrupting regulation of the insulin-like growth factor 2 gene.

CONTEXT: IGF-II is an imprinted gene (predominantly transcribed from the paternally inherited allele), which has an important role in fetal growth in mice. IGF2 gene expression is regulated by a complex system of enhancers and promoters that determine tissue-specific and development-specific transcription. In mice, enhancers of the IGF2 gene are located up to 260 kb telomeric to the gene. The role of IGF-II in humans is unclear. OBJECTIVE: A woman of short adult stature (1.46 m, -3 sd score) born with severe intrauterine growth retardation (1.25 kg at term, -5.4 SD score) and atypical diabetes diagnosed at the age of 23 yr had a balanced chromosomal translocation t(1;11) (p36.22; p15.5). We hypothesized that her phenotype resulted from disruption of her paternally derived IGF2 gene because her daughter who inherited the identical translocation had normal birth weight. DESIGN: Both chromosomal break points were identified using fluorescent in situ hybridization. Sequence, methylation, and expression of the IGF2 gene was examined. Hyperinsulinemic, euglycemic clamp with glucose tracers and magnetic resonance imaging of the thorax, abdomen, and pelvis were performed. RESULTS: The 11p15.5 break point mapped 184 kb telomeric of the IGF2 gene. Microsatellite markers confirmed paternal origin of this chromosome. IGF2 gene sequence and methylation was normal. IGF2 gene expression was reduced in lymphoblasts. Clamp studies showed marked hepatic and total insulin resistance. Massive excess sc fat was seen on magnetic resonance imaging despite slim body mass index (21.1 kg/m2). CONCLUSIONS: A break point 184 kb upstream of the paternally derived IGF2 gene, separating it from some telomeric enhancers, resulted in reduced expression in some mesoderm-derived adult tissues causing intrauterine growth retardation, short stature, lactation failure, and insulin resistance with altered fat distribution.

Measurement of hepatic insulin sensitivity early after the bypass of the proximal small bowel in humans.

OBJECTIVE: Unlike gastric banding or sleeve gastrectomy procedures, intestinal bypass procedures, Roux-en-Y gastric bypass in particular, lead to rapid improvements in glycaemia early after surgery. The bypass of the proximal small bowel may have weight loss and even caloric restriction-independent glucose-lowering properties on hepatic insulin sensitivity. In this first human mechanistic study, we examined this hypothesis by investigating the early effects of the duodeno-jejunal bypass liner (DJBL; GI Dynamics, USA) on the hepatic insulin sensitivity by using the gold standard euglycaemic hyperinsulinaemic clamp methodology. METHOD: Seven patients with obesity underwent measurement of hepatic insulin sensitivity at baseline, 1 week after a low-calorie liquid diet and after a further 1 week following insertion of the DJBL whilst on the same diet. RESULTS: Duodeno-jejunal bypass liner did not improve the insulin sensitivity of hepatic glucose production beyond the improvements achieved with caloric restriction. CONCLUSIONS: Caloric restriction may be the predominant driver of early increases in hepatic insulin sensitivity after the endoscopic bypass of the proximal small bowel. The same mechanism may be at play after Roux-en-Y gastric bypass and explain, at least in part, the rapid improvements in glycaemia.

Effects of high-dose growth hormone on glucose and glycerol metabolism at rest and during exercise in endurance-trained athletes.

CONTEXT: Recombinant human-GH (r-hGH), in supraphysiological doses, is self-administered by athletes in the belief that it is performance enhancing. OBJECTIVE: The objective of this study was to determine whether r-hGH alters whole-body glucose and glycerol metabolism in endurance-trained athletes at rest and during and after exercise. DESIGN: This was a 4-wk double-blind placebo-controlled trial. SETTING: This study was conducted at St. Thomas Hospital (London, UK). PARTICIPANTS: Twelve endurance-trained male athletes were recruited and randomized to r-hGH (0.2 U/kg.d) (n = 6) or identical placebo (n = 6) for 4 wk. One (placebo group) withdrew after randomization. INTERVENTION: Intervention was conducted by randomization to r-hGH (0.2 U/kg x d) or identical placebo for 4 wk. MAIN OUTCOME MEASURES: Whole-body rates of appearance (Ra) of glucose and glycerol (an index of lipolysis) and rate of disappearance of glucose were measured using infusions of d-[6-6-2H2]glucose and 2H5-glycerol. RESULTS: Plasma levels of glycerol and free fatty acids and glycerol Ra at rest and during and after exercise increased during r-hGH treatment (P < 0.05 vs. placebo). Glucose Ra and glucose rate of disappearance were greater after exercise during r-hGH treatment (P < 0.05 vs. placebo). Resting energy expenditure and fat oxidation were greater under resting conditions during r-hGH treatment (P < 0.05 vs. placebo). CONCLUSIONS: r-hGH in endurance-trained athletes increased lipolysis and fatty acid availability at rest and during and after exercise. r-hGH increased glucose production and uptake rates after exercise. The relevance of these effects for athletic performance is not known.

Exercise Training Reduces Liver Fat and Increases Rates of VLDL Clearance But Not VLDL Production in NAFLD.

CONTEXT: Randomized controlled trials in nonalcoholic fatty liver disease (NAFLD) have shown that regular exercise, even without calorie restriction, reduces liver steatosis. A previous study has shown that 16 weeks of supervised exercise training in NAFLD did not affect total very low-density lipoprotein (VLDL) kinetics. OBJECTIVE: The objective of the study was to determine the effect of exercise training on intrahepatocellular fat (IHCL) and the kinetics of large triglyceride (TG)-rich VLDL1 and smaller denser VLDL2, which has a lower TG content. DESIGN: This was a 16-week randomized controlled trial. PATIENTS: A total of 27 sedentary patients with NAFLD participated in the trial. INTERVENTION: The intervention was composed of supervised exercise with moderate-intensity aerobic exercise or conventional lifestyle advice (control). MAIN OUTCOME: VLDL1 and VLDL2-TG and apolipoprotein B (apoB) kinetics were investigated using stable isotopes before and after the intervention. RESULTS: In the exercise group, maximal oxygen uptake increased by 31% ± 6% (mean ± SEM) and IHCL decreased from 19.6% (14.8%, 30.0%) to 8.9% (5.4%, 17.3%) (median [interquartile range]) with no significant change in maximal oxygen uptake or IHCL in the control group (change between groups, P < .001 and P = .02, respectively). Exercise training increased VLDL1-TG and apoB fractional catabolic rates, a measure of clearance, (change between groups, P = .02 and P = .01, respectively), and VLDL1-apoB production rate (change between groups, P = .006), with no change in VLDL1-TG production rate. Plasma TG did not change in either group. CONCLUSION: An increased clearance of VLDL1 may contribute to the significant decrease in liver fat after 16 weeks of exercise in NAFLD. A longer duration or higher-intensity exercise interventions may be needed to lower the plasma TG and VLDL production rate.

IGF-I treatment in adults with type 1 diabetes: effects on glucose and protein metabolism in the fasting state and during a hyperinsulinemic-euglycemic amino acid clamp.

Type 1 diabetes is associated with abnormalities of the growth hormone (GH)-IGF-I axis. Such abnormalities include decreased circulating levels of IGF-I. We studied the effects of IGF-I therapy (40 microg x kg(-1) x day(-1)) on protein and glucose metabolism in adults with type 1 diabetes in a randomized placebo-controlled trial. A total of 12 subjects participated, and each subject was studied at baseline and after 7 days of treatment, both in the fasting state and during a hyperinsulinemic-euglycemic amino acid clamp. Protein and glucose metabolism were assessed using infusions of [1-13C]leucine and [6-6-2H2]glucose. IGF-I administration resulted in a 51% rise in circulating IGF-I levels (P < 0.005) and a 56% decrease in the mean overnight GH concentration (P < 0.05). After IGF-I treatment, a decrease in the overnight insulin requirement (0.26+/-0.07 vs. 0.17+/-0.06 U/kg, P < 0.05) and an increase in the glucose infusion requirement were observed during the hyperinsulinemic clamp (approximately 67%, P < 0.05). Basal glucose kinetics were unchanged, but an increase in insulin-stimulated peripheral glucose disposal was observed after IGF-I therapy (37+/-6 vs. 52+/-10 micromol x kg(-1) x min(-1), P < 0.05). IGF-I administration increased the basal metabolic clearance rate for leucine (approximately 28%, P < 0.05) and resulted in a net increase in leucine balance, both in the basal state and during the hyperinsulinemic amino acid clamp (-0.17+/-0.03 vs. -0.10+/-0.02, P < 0.01, and 0.25+/-0.08 vs. 0.40+/-0.06, P < 0.05, respectively). No changes in these variables were recorded in the subjects after administration of placebo. These findings demonstrated that IGF-I replacement resulted in significant alterations in glucose and protein metabolism in the basal and insulin-stimulated states. These effects were associated with increased insulin sensitivity, and they underline the major role of IGF-I in protein and glucose metabolism in type 1 diabetes.

Acute hyperinsulinemia decreases the hepatic secretion of very-low-density lipoprotein apolipoprotein B-100 in NIDDM.

In a randomized crossover study, we measured the hepatic secretion rate of very-low-density lipoprotein (VLDL) apolipoprotein B-100 (apoB) in seven patients with well-controlled non-insulin-dependent diabetes mellitus (NIDDM) (HbA1 8.4 +/- 0.4% [mean +/- SE]) on two occasions: during a 13-h hyperinsulinemic (plasma insulin concentration 586 +/- 9.7 pmol/l) euglycemic (plasma glucose concentration 5.2 +/- 0.1 mmol/l) clamp; and during a 13-h saline (control) infusion. After 5 h of the hyperinsulinemic euglycemic clamp (or saline infusion) when a new steady state of apoB turnover was reached, [1-(13)C]leucine was administered by a primed (1 mg/kg), constant 8-h infusion (1 mg.kg-1. h-1). VLDL apoB isotopic enrichment was determined with gas chromatography-mass spectrometry, and a monoexponential model was used to calculate the fractional secretion rate of VLDL apoB. VLDL apoB secretion rate was significantly reduced during the hyperinsulinemic euglycemic clamp compared with the saline study (12.2 +/- 3.6 vs. 24.5 +/- 7.1 mg.kg-1.day-1, P = 0.001), but there was no change in the fractional catabolic rate of VLDL apoB. Concomitantly, plasma concentrations of nonesterified fatty acids (NEFAs), glycerol, and triglycerides (TGs) were significantly lower during the hyperinsulinemic euglycemic clamp compared with the saline study (NEFAs, P < 0.001; glycerol, P = 0.005; TGs P = 0.004). We conclude that acute hyperinsulinemia decreases the hepatic secretion rate of VLDL apoB in NIDDM, probably in part due to reduction in the delivery of NEFA and glycerol substrate to the liver.

Effects of growth hormone (GH) replacement therapy on low-density lipoprotein apolipoprotein B100 kinetics in adult patients with GH deficiency: a stable isotope study.

GH replacement therapy has been shown to improve the dyslipidemic condition in a substantial proportion of patients with adult GH deficiency. The mechanisms are not yet fully elucidated. Low-density lipoprotein (LDL) apolipoprotein B100 (apoB) formation and catabolism are important determinants of plasma cholesterol concentrations. This study examined the effect of GH replacement therapy on LDL apoB metabolism using a stable isotope turnover technique. LDL apoB kinetics was determined in 13 adult patients with GH deficiency before and after 3 months GH/placebo treatment in a randomized, double-blind, placebo-controlled study. LDL apoB (13)C-leucine enrichment was determined by isotope-ratio mass spectrometry. Plasma volume was assessed by standardized radionuclide dilution technique. GH replacement therapy significantly decreased LDL cholesterol, LDL apoB concentrations, and LDL apoB pool size compared with placebo. Compared with baseline, GH replacement therapy resulted in a significant increase in plasma volume and fractional catabolic rate, whereas LDL formation rate remained unchanged. LDL lipid content did not significantly change after GH and placebo. This study suggests that short-term GH replacement therapy decreases the LDL apoB pool by increasing removal of LDL particles without changing LDL composition or LDL apoB production rate. In addition, it is possible that the beneficial effects of GH on the cardiovascular system contribute to these findings.

Effect of growth hormone (GH) on glycerol and free fatty acid metabolism during exhaustive exercise in GH-deficient adults.

GH is an important regulator of fat metabolism at rest, but it is not known whether it regulates fat metabolism during exercise. To determine whether physiologic concentrations of GH influence fat metabolism during exercise, we randomized 16 GH-deficient adults, receiving long-term (mean duration, 5 yr) GH replacement, to either continue GH (n = 8) or receive identical placebo (n = 8) for a 3-month period. Metabolic studies, at rest, during and following exhaustive exercise were carried out at baseline and at the end of the 3 months. The rate of appearance of glycerol (glycerol Ra, an index of lipolysis) and free fatty acids (FFA, FFA Ra) and the rate of disappearance of FFA (FFA Rd) in the plasma were measured using infusions of (2)H(5)-glycerol and 1-(13)C-palmitic acid. Changes in body composition were assessed using dual-energy x-ray absorptiometry scanning and anthropometric measurements. In the baseline studies, exercise resulted in an increase in plasma glycerol and FFA concentrations, glycerol Ra, FFA Ra, and FFA Rd (P < 0.001). Three months of GH withdrawal resulted in reductions in plasma glycerol and FFA, glycerol Ra, FFA Ra, and FFA Rd at rest (P < 0.05 vs. baseline) and during exercise (P < 0.05 vs. baseline and vs. GH treated). Lean body mass decreased after 3 months of GH withdrawal, but total body fat, trunk fat, waist circumference, and the sum of skinfold thicknesses increased after 3 months of GH withdrawal (P < 0.05 vs. baseline and vs. GH treated). Fasting insulin and homeostasis model assessment of insulin resistance decreased after 3 months of GH withdrawal (P < 0.05 vs. baseline and vs. GH treated). In summary, GH withdrawal for 3 months resulted in reductions in release of glycerol and FFA into the circulation and uptake of FFA into the tissues during intense exercise. These changes were accompanied by reduced lean body mass and increased total body and trunk fat. Further studies are required to determine whether reduced mobilization of fat during exercise contributes to reduced exercise capacity and increased body fat in GH-deficient adults.

Abnormalities of very low density lipoprotein apolipoprotein B-100 metabolism contribute to the dyslipidaemia of adult growth hormone deficiency.

Increased cardiovascular mortality in adult growth hormone deficiency (GHD) may be, in part, explained by the dyslipidaemia associated with this condition. It is possible that abnormalities of very low density lipoprotein apolipoprotein B-100 (VLDL apoB) metabolism contribute to this dyslipidaemia. To test this hypothesis, we measured VLDL apoB kinetics in adult GH deficient patients (4 females, 3 males; age 50.1 +/- 4.7 yr (mean +/- SEM); BMI 28.2 +/- 1.1 kg/m2; total cholesterol (TC) 6.6 +/- 0.3 mmol/l; triglyceride (TG) 2.8 +/- 0.6 mmol/l; HDL cholesterol 1.1 +/- 0.1 mmol/l) and in control subjects (4 females, 3 male; age 47.0 +/- 4.7 yr; BMI 27.0 +/- 2.6 kg/m2; TC 5.0 +/- 0.4 mmol/l; TG 0.9 +/- 0.2 mmol/l; HDL cholesterol 1.4 +/- 0.1 mmol/l). [1-(13)C] leucine was administered by a primed (1 mg/kg), constant intravenous infusion (1 mg/kg/hr) and VLDL apoB enrichment with 13C leucine was determined using gas-chromatography mass-spectrometry. The GHD patients had a significantly higher hepatic secretion rate of VLDL apoB (15.5 +/- 1.8 mg/kg/day vs 9.4 +/- 0.6 mg/kg/day p = 0.007) and reduced catabolism ofVLDL apoB (metabolic clearance rate; 12.3 +/- 1.7 ml/min vs 24.3 +/- 4.8 ml/min p < 0.05) compared with control subjects. These findings suggest that GH is integrally involved in the regulation of VLDL apoB metabolism.