Professor A. Margot Umpleby

Context Randomised controlled trials in non-alcoholic fatty liver disease (NAFLD) have shown that regular exercise, even without calorie restriction, reduces liver steatosis. A previous study has shown that 16 weeks supervised exercise training in NAFLD did not affect total VLDL kinetics. Objective 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 A 16 week randomised controlled trial. Patients 27 sedentary patients with NAFLD. Intervention Supervised exercise with moderate-intensity aerobic exercise or conventional lifestyle advice (control). Main outcome Very low density lipoprotein1 (VLDL1) and VLDL2-TG and apolipoproteinB (apoB) kinetics investigated using stable isotopes before and after the intervention. Results In the exercise group VO2max increased by 31±6% (mean±SEM) and IHCL decreased from 19.6% (14.8, 30.0) to 8.9% (5.4, 17.3) (median (IQR)) with no significant change in VO2max or IHCL in the control group (change between groups p

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 (

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).

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.

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).

Context GLP-1 agonists control postprandial glucose and lipid excursion in type 2 diabetes; however the mechanism(s) are unclear. Objective To determine the mechanism(s) of postprandial lipid and glucose control with lixisenatide (GLP-1 analogue) in type 2 diabetes. Design Randomised, double-blind, cross-over study. Setting Centre for Diabetes, Endocrinology, and Research, Royal Surrey County Hospital, Guildford, UK Patients Eight obese men with type 2 diabetes (57.3±1.9yrs; BMI 30.3±1.0kg/m2, HbA1C 66.5±2.6mmol/mol, [8.2±0.3%]). Interventions Two metabolic studies, four-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 iv bolus of [2H5]glycerol in a 12h study, with hourly feeding. Oral [13C]triolein, in a single meal, labelled 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 AUC60-480min 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 rate (Ra) (P=0.015), Rameal (P=0.0098) and acetaminophen AUC0-360min (P=0.006) were lower with lixisenatide than placebo. Conclusions Lixisenatide reduced [13C]oleate concentration, derived from a single meal in CM-TAG, as well as glucose Rameal, through delayed gastric emptying. However day-long CM production, measured with repeated meal-feeding, was not reduced by lixisenatide and decreased CM-TAG concentration was due to increased CM-TAG clearance.

Context:High plasma triglycerides (TG) have been shown to be independent and better predictors of cardiovascular disease than low-density lipoprotein (LDL) cholesterol in women. This may be due to gender differences in very-low-density lipoprotein 1 (VLDL(1))- and VLDL(2)-TG and fatty acid kinetics.Objective:Our objective was to investigate whether there are differences in VLDL(1)- and VLDL(2)-TG and fatty acid kinetics in obese men and postmenopausal women, a high risk group for cardiovascular disease.Research Design and Methods:Stable isotopes techniques were used to measure fasting palmitate rate of appearance, metabolic clearance rate, oxidation rate, and nonoxidative disposal rate, VLDL(1)-TG and VLDL(2)-TG fractional catabolic rate (FCR) and production rate (PR). Whole-body fat distribution was measured by magnetic resonance imaging.Participants:Participants included 10 postmenopausal obese women and eight obese men matched for age, body mass index, and fasting plasma TG.Results:The women had lower visceral fat and higher sc fat than the men (P < 0.001 and P < 0.002). Palmitate rate of appearance, metabolic clearance rate, nonoxidative disposal rate, and oxidation rate corrected for resting energy expenditure were greater in the women than the men (all P < 0.03). VLDL(2)-TG PR corrected for fat-free mass was higher in the women (P < 0.001). VLDL(2)-TG and VLDL(2)-cholesterol pools were higher in the women (P < 0.001 and P < 0.008). VLDL(1)-TG FCR and PR and VLDL(2)-TG FCR were not different between genders.Conclusion:Fatty acid and VLDL(2)-TG flux is higher in postmenopausal obese women than in obese men matched for fasting plasma TG levels.

Context: Data on metabolic effects of Growth Hormone (GH) derived from studies using GH suppression by pharmacological agents may not reflect selective actions. Objective: To evaluate the effects of GH antagonism on glucose and lipid metabolism using pegvisomant, a selective GH receptor antagonist in patients with type 1 diabetes (T1D). Design & participants: In a randomised, placebo-controlled, crossover study, 10 young adults with T1D were evaluated at baseline, and after 4 weeks of treatment with either 10mg of pegvisomant or placebo. The assessments included an overnight euglycaemic steady state followed by a hyperinsulinaemic euglycaemic clamp, and employed glucose and glycerol cold stable isotopes. Outcome measures: Hepatic and peripheral insulin sensitivity (IS), lipid turnover and intramyocellular lipid (IMCL) Results: Compared with placebo, pegvisomant treatment resulted in lower IGF-I levels (p

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 microg.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 ( approximately 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.

Dietary sugars are linked to the development of non-alcoholic fatty liver disease (NAFLD) and dyslipidaemia, but it is unknown if NAFLD itself influences the effects of sugars on plasma lipoproteins. To study this further, men with NAFLD (n=11) and low liver fat ‘controls’ (n= 14) were fed two iso-energetic diets, high or low in sugars (26% or 6% total energy) for 12 weeks, in a randomised, cross-over design. Fasting plasma lipid and lipoprotein kinetics were measured after each diet by stable isotope trace-labelling. There were significant differences in the production and catabolic rates of VLDL subclasses between men with NAFLD and controls, in response to the high and low sugar diets. Men with NAFLD had higher plasma concentrations of VLDL1-triacylglycerol (TAG) after the high (P

The study aimed to 1] develop a method which 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 (2)H5-glycerol as the tracer. An immunoaffinity method which completely separated hepatic and intestinal particles using sequential binding to three antibodies to apolipoprotein B100 (apoB100) 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 which included an oral (13)C3-glycerol tripalmitin tracer (study 2). In both studies an intravenous bolus of (2)H5-glycerol was administered to label TAG in hepatic and intestinal lipoproteins. In both feeding studies there was sufficient incorporation of the glycerol tracer into the exogenous lipoproteins to enable isotopic enrichment to be measured. In study 2 the oral tracer enrichment in VLDL1 was

Abstract: 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.

A new stochastic computational method was developed to estimate the endogenous glucose production, the meal-related glucose appearance rate (R(a meal)), and the glucose disposal (R(d)) during the meal tolerance test. A prior probability distribution was adopted which assumes smooth glucose fluxes with individualized smoothness level within the context of a Bayes hierarchical model. The new method was contrasted with the maximum likelihood method using data collected in 18 subjects with type 2 diabetes who ingested a mixed meal containing [U-(13)C]glucose. Primed [6,6-(2)H(2)]glucose was infused in a manner that mimicked the expected endogenous glucose production. The mean endogenous glucose production, R(a meal), and R(d) calculated by the new method and maximum likelihood method were nearly identical. However, the maximum likelihood gave constant, nonphysiological postprandial endogenous glucose production in two subjects whilst the new method gave plausible estimates of endogenous glucose production in all subjects. Additionally, the two methods were compared using a simulated triple-tracer experiment in 12 virtual subjects. The accuracy of the estimates of the endogenous glucose production and R(a meal) profiles was similar [root mean square error (RMSE) 1.0±0.3 vs. 1.4±0.7μmol/kg/min for EGP and 2.6±1.0 vs. 2.9±0.9μmol/kg/min for R(a meal); new method vs. maximum likelihood method; P=NS, paired t-test]. The accuracy of R(d) estimates was significantly increased by the new method (RMSE 5.3±1.9 vs. 4.2±1.3; new method vs. ML method; P

Acromegaly is complicated by an increased incidence of diabetes mellitus caused by impaired insulin sensitivity and reduced beta-cell function. Pegvisomant blocks activity at GH receptors, normalizing IGF-I in over 90% of patients and improving insulin sensitivity. The mechanisms for this increase in insulin sensitivity are not fully determined. We used stable isotope techniques to investigate the effects of pegvisomant on glucose and lipid metabolism in acromegaly.

The leading causes of mortality in nonalcoholic fatty liver disease (NAFLD) relate to cardiovascular disease (CVD). The contribution of nitric oxide (NO) to endothelial function, a surrogate of CVD risk, is currently unknown in NAFLD. We hypothesize that NO-mediated cutaneous microvessel function would be impaired in NAFLD compared with controls and that exercise would enhance microvessel function compared with conventional care. Thirteen NAFLD patients (aged 50 ± 3 yr, BMI 31 ± 1 kg/m(2)) and seven controls (48 ± 4 yr, 30 ± 2 kg/m(2)) were studied. NAFLD patients were randomized to either 16 wk of exercise or conventional care. Cutaneous microvessel function was examined using laser Doppler flowmetry combined with intradermal microdialysis of N(G)-monomethyl-l-arginine to assay the NO dilator response to local forearm heating. Magnetic resonance imaging and spectroscopy quantified abdominal and liver fat, respectively, and cardiorespiratory fitness was assessed. Differences in NO contribution to cutaneous blood flow between NAFLD and control individuals and between interventions were analyzed using general linear modeling. NO contribution to cutaneous blood flow was similar between NAFLD and controls (P = 0.47). Cardiorespiratory fitness was greater following exercise training compared with conventional care. NO contribution to cutaneous blood flow in response to heating at 42°C was 20.4% CVCmax (95% CI = 4.4, 36.4) greater following exercise training compared with conventional care (P = 0.02). Exercise training improves cutaneous microvascular NO function in NAFLD patients. The benefit of exercise training compared with conventional care strongly supports a role for exercise in the prevention of CVD in NAFLD.

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.

CONTEXT: Declines in GH and testosterone (Te) secretion may contribute to the detrimental aging changes of elderly men. OBJECTIVE: To assess the effects of near-physiological GH with/without Te administration on lean body mass, total body fat, midthigh muscle cross-section area, muscle strength, aerobic capacity, condition-specific quality of life (Age-Related Hormone Deficiency-Dependent Quality of Life questionnaire), and generic health status (36-Item Short-Form Health Survey) of older men. DESIGN, SETTINGS, AND PARTICIPANTS: A 6-month, randomized, double-blind, placebo-controlled trial was performed on 80 healthy, community-dwelling, older men (age, 65-80 yr). INTERVENTIONS: Participants were randomized to receive 1) placebo GH or placebo Te, 2) recombinant human GH (rhGH) and placebo Te (GH), 3) Te and placebo rhGH (Te), or 4) rhGH and Te (GHTe). GH doses were titrated over 8 wk to produce IGF-I levels in the upper half of the age-specific reference range. A fixed dose of Te (5 mg) was given by transdermal patches. RESULTS: Lean body mass increased with GHTe (P = 0.008) and GH (P = 0.004), compared with placebo. Total body fat decreased with GHTe only (P = 0.02). Midthigh muscle (P = 0.006) and aerobic capacity (P < 0.001) increased only after GHTe. Muscle strength changes were variable; one of six measures significantly increased with GHTe. Significant treatment group by time interactions indicated an improved Age-Related Hormone Deficiency-Dependent Quality of Life questionnaire score (P = 0.007) in the GH and GHTe groups. Bodily pain increased with GH alone, as determined by the Short-Form Health Survey (P = 0.003). There were no major adverse effects. CONCLUSION: Coadministration of low dose GH with Te resulted in beneficial changes being observed more often than with either GH or Te alone.

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.

Existing methods of measuring glucose kinetics are subject to errors. There is considerable interest in improved methods of measuring glucose kinetics to allow the development of new regimes for the treatment of diabetes mellitus. 3-O-Methyl-D-glucose is transported but not metabolized and therefore allows independent estimation of transport parameters. We describe a method by which 3-O-methyl-D-glucose in plasma samples can be measured in protocols during which glucose flux is assessed with simultaneous use of two isotopically labeled glucoses to quantitate and validate measurements of the rate of glucose appearance and disappearance. Quantitative gas chromatographic/mass spectrometric (GC/MS) analysis of 3-O-methyl-D-glucose, D-glucose, D-[U-13C] glucose and D-[6,6-2H2] glucose in human plasma using methoxime-trimethylsilyl ether derivatives is described. Measurements of all four derivatives were performed together in a small sample volume (50 microliters) with high precision. The intra-assay (inter-assay) coefficients of variation at an isotope content of 0.25 atom% excess for D-[6,6-2H2] glucose, D-[U-13C] glucose and 3-O-methyl-D-glucose were 0.8% (1.0%), 0.5% (4.0%) and 0.1% (3.7%), respectively. This method provides the basis for quantitative estimation of parameters of glucose kinetics in man and the rates of glucose flux across the cell membrane.

AIMS/HYPOTHESIS: It is not known whether the beneficial effects of exercise training on insulin sensitivity are due to changes in hepatic and peripheral insulin sensitivity or whether the changes in insulin sensitivity can be explained by adaptive changes in fatty acid metabolism, changes in visceral fat or changes in liver and muscle triacylglycerol content. We investigated the effects of 6 weeks of supervised exercise in sedentary men on these variables. SUBJECTS AND METHODS: We randomised 17 sedentary overweight male subjects (age 50 +/- 2.6 years, BMI 27.6 +/- 0.5 kg/m(2)) to a 6-week exercise programme (n = 10) or control group (n = 7). The insulin sensitivity of palmitic acid production rate (Ra), glycerol Ra, endogenous glucose Ra (EGP), glucose uptake and glucose metabolic clearance rate were measured at 0 and 6 weeks with a two-step hyperinsulinaemic-euglycaemic clamp [step 1, 0.3 (low dose); step 2, 1.5 (high dose) mU kg(-1) min(-1)]. In the exercise group subjects were studied >72 h after the last training session. Liver and skeletal muscle triacylglycerol content was measured by magnetic resonance spectroscopy and visceral adipose tissue by cross-sectional computer tomography scanning. RESULTS: After 6 weeks, fasting glycerol, palmitic acid Ra (p = 0.003, p = 0.042) and NEFA concentration (p = 0.005) were decreased in the exercise group with no change in the control group. The effects of low-dose insulin on EGP and of high-dose insulin on glucose uptake and metabolic clearance rate were enhanced in the exercise group but not in the control group (p = 0.026; p = 0.007 and p = 0.04). There was no change in muscle triacylglycerol and liver fat in either group. CONCLUSIONS/INTERPRETATION: Decreased availability of circulating NEFA may contribute to the observed improvement in the insulin sensitivity of EGP and glucose uptake following 6 weeks of moderate exercise.

Improving physical function and mobility in a continuously expanding elderly population emerges as a high priority of medicine today. Muscle mass, strength/power, and maximal exercise capacity are major determinants of physical function, and all decline with aging. This contributes to the incidence of frailty and disability observed in older men. Furthermore, it facilitates the accumulation of body fat and development of insulin resistance. Muscle adaptation to exercise is strongly influenced by anabolic endocrine hormones and local load-sensitive autocrine/paracrine growth factors. GH, IGF-I, and testosterone (T) are directly involved in muscle adaptation to exercise because they promote muscle protein synthesis, whereas T and locally expressed IGF-I have been reported to activate muscle stem cells. Although exercise programs improve physical function, in the long-term most older men fail to comply. The GH/IGF-I axis and T levels decline markedly with aging, whereas accumulating evidence supports their indispensable role in maintaining physical function integrity. Several studies have reported that the administration of T improves lean body mass and maximal voluntary strength in healthy older men. On the other hand, most studies have shown that administration of GH alone failed to improve muscle strength despite amelioration of the detrimental somatic changes of aging. Both GH and T are anabolic agents that promote muscle protein synthesis and hypertrophy but work through separate mechanisms, and the combined administration of GH and T, albeit in only a few studies, has resulted in greater efficacy than either hormone alone. Although it is clear that this combined approach is effective, this review concludes that further studies are needed to assess the long-term efficacy and safety of combined hormone replacement therapy in older men before the medical rationale of prescribing hormone replacement therapy for combating the sarcopenia of aging can be established.

The aim was to determine whether fed VLDL and chylomicron (CM) triacylglycerol (TAG) production rates are elevated in metabolic syndrome (MetS). Eight men with MetS (BMI 29.7 ± 1.1) and eight lean age-matched healthy men (BMI 23.1 ± 0.4) were studied using a frequent feeding protocol. After 4 h of feeding, an intravenous bolus of (2)H5-glycerol was administered to label VLDL1, VLDL2, and TAG. (13)C-glycerol tripalmitin was administered orally as an independent measure of CM TAG metabolism. Hepatic and intestinal lipoproteins were separated by an immunoaffinity method. In MetS, fed TAG and the increment in TAG from fasting to feeding were higher (P = 0.03 and P = 0.04, respectively) than in lean men. Fed CM, VLDL1, and VLDL2 TAG pool sizes were higher (P = 0.006, P = 0.03, and P < 0.02, respectively), and CM, VLDL1, and VLDL2 TAG production rates were higher (P < 0.002, P < 0.05, and P = 0.06, respectively) than in lean men. VLDL1, VLDL2, and CM TAG clearance rates were not different between groups. In conclusion, prandial hypertriglyceridemia in men with MetS was due to an increased production rate of both VLDL and CM TAG. Since both groups received identical meals, this suggests that in MetS the intestine is synthesizing more TAG de novo for export in CMs.

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.

Antiretroviral (ARV) treatment has been associated with abnormalities in lipid and mitochondrial metabolism. We compared patterns of gene expression in the subcutaneous adipose tissue (SAT) of HIV-positive subjects before and after 18-24 months of ARV therapy with HIV-negative controls.

Objectives: Evidence for a causal relationship between sleep-loss and metabolism is derived primarily from short-term sleep deprivation studies in the laboratory. The objective of this study was to investigate whether small changes in sleep duration over a three week period while participants are living in their normal environment lead to changes in insulin sensitivity and other metabolic parameters. Methods: Nineteen healthy, young, normal-weight men were randomised to either sleep restriction (habitual bedtime minus 1.5 h) or a control condition (habitual bedtime) for three weeks. Weekly assessments of insulin sensitivity by hyperinsulinaemic-euglycaemic clamp, anthropometry, vascular function, leptin and adiponectin were made. Sleep was assessed continuously using actigraphy and diaries. Results: Assessment of sleep by actigraphy confirmed that the intervention reduced daily sleep duration by 01:19 ± 00:15 (SE; p < 0.001). Sleep restriction led to changes in insulin sensitivity, body weight and plasma concentrations of leptin which varied during the three week period. There was no effect on plasma adiponectin or vascular function. Conclusions: Even minor reductions in sleep duration lead to changes in insulin sensitivity, body weight and other metabolic parameters which vary during the exposure period. Larger and longer longitudinal studies of sleep restriction and sleep extension are warranted. © 2013 Elsevier Inc.

Objective: To determine the effect of SGLT2 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 wash out 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 rate of glucose production (Ra), disappearance (Rd) and lipolysis. At isotopic steady state insulin was withdrawn and the study terminated after 600 minutes or earlier if blood glucose reached 18mmol/L, bicarbonate 27 and

Context: Dietary fibers have been associated with a reduced incidence of type 2 diabetes mellitus in epidemiological studies; however, the precise mechanisms are unknown. Objective: The objective of the study was to evaluate the efficacy and site of action of an insoluble dietary fiber derived from maize (HAM-RS2) in improving insulin resistance in subjects at increased risk of type 2 diabetes mellitus. Design: This study was a randomized, controlled crossover, dietary intervention study. Setting: The study was conducted at the Centre for Diabetes, Endocrinology, and Research, Royal Surrey County Hospital, Guildford, United Kingdom. Participants: Fifteen men and women with insulin resistance participated in the study. Intervention: The intervention included 40 g/d HAM-RS2 compared with a matched placebo for 8 wk. Main Outcome Measures: After each supplement, participants underwent a two-step hyperinsulinemic-euglycemic clamp study with the addition of glucose tracers; a meal tolerance test; arteriovenous sampling across forearm muscle tissue; and a sc adipose tissue biopsy for assessment of gene expression. Results: There was enhanced uptake of glucose into the forearm muscle measured by arteriovenous sampling (65 ± 15% increase after resistant starch; P < 0.001). Adipose tissue function was also affected, with enhanced fatty acid suppression after HAM-RS2 treatment and an increase in gene expression for hormone sensitive lipase (P = 0.005), perilipin (P = 0.011), lipoprotein lipase (P = 0.014), and adipose triglyceride lipase (P = 0.03) in biopsy samples. There was no effect on the insulin sensitivity of hepatic glucose production or plasma lipids after HAM-RS2. Conclusion: HAM-RS2 improved peripheral but not hepatic insulin resistance and requires further study as an intervention in patients with or at risk for type 2 diabetes.

Non-alcoholic fatty liver disease (NAFLD) is associated with multi-organ (hepatic, skeletal muscle, adipose tissue) insulin resistance (IR). Exercise is an effective treatment for lowering liver fat but its effect on IR in NAFLD is unknown. We aimed to determine whether supervised exercise in NAFLD would reduce liver fat and improve hepatic and peripheral (skeletal muscle and adipose tissue) insulin sensitivity. Sixty nine NAFLD patients were randomized to 16 weeks exercise supervision (n=38) or counselling (n=31) without dietary modification. All participants underwent MRI/spectroscopy to assess changes in body fat and in liver and skeletal muscle triglyceride, before and following exercise/counselling. To quantify changes in hepatic and peripheral insulin sensitivity, a pre-determined subset (n=12 per group) underwent a two-stage hyperinsulinaemic euglycaemic clamp pre- and post-intervention. Results are shown as mean [95% confidence interval (CI)]. Fifty participants (30 exercise, 20 counselling), 51 years (IQR 40, 56), body mass index (BMI) 31 kg/m(2) (IQR 29, 35) with baseline liver fat/water % of 18.8% (IQR 10.7, 34.6) completed the study (12/12 exercise and 7/12 counselling completed the clamp studies). Supervised exercise mediated a greater reduction in liver fat/water percentage than counselling [Δ mean change 4.7% (0.01, 9.4); P

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 0.5Units/kgBW detemir or NPH insulin. Glucose concentration was clamped at 5mmol/L then increased to 10mmol/L. Glucose production rate (glucose Ra), glucose uptake (glucose Rd) and glycerol production (glycerol Ra) were measured with a constant iv infusion of [6,6(2) H2 ]glucose and [(2) H5 ]glycerol. Electroencephalography direct (DC) and alternating (AC) current potentials were measured. While detemir induced comparable effects on glucose Ra, glucose Rd and glycerol Ra during euglycaemia, compared with NPH, it triggered a distinct negative shift in DC-potentials, with significant treatment effect in frontal cerebrocortical channels (p

OBJECTIVE: In hypopituitary men, oral delivery of unesterified testosterone in doses that result in a solely hepatic androgen effect enhances protein anabolism during GH treatment. In this study, we aimed to determine whether liver-targeted androgen supplementation induces protein anabolism in GH-replete normal women. DESIGN: Eight healthy postmenopausal women received 2-week treatment with oral testosterone at a dose of 40 mg/day (crystalline testosterone USP). This dose increases portal concentrations of testosterone, exerting androgenic effects on the liver without a spillover into the systemic circulation. OUTCOME MEASURES: The outcome measures were whole-body leucine turnover, from which leucine rate of appearance (LRa, an index of protein breakdown) and leucine oxidation (Lox, a measure of irreversible protein loss) were estimated, energy expenditure and substrate utilization. We measured the concentration of liver transaminases as well as of testosterone, SHBG and IGF1. RESULTS: Testosterone treatment significantly reduced LRa by 7.1 ± 2.5% and Lox by 14.6 ± 4.5% (P

Objective. To investigate the mechanism for increased ketogenesis following treatment with SGLT2 inhibitor, dapagliflozin in people with type 2 diabetes. Research, Design & Methods. This 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 30ml 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 beta-hydroxybutyrate (BOHB) concentrations and [13C2] BOHB concentrations were higher and glucose concentrations lower with dapagliflozin than placebo. Non-esterified fatty acids (NEFA) were higher with dapagliflozin at 300 and 420 min but lipolysis at 450-480 min was not different. Triacylglycerol (TAG) 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 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 suggests a metabolic switch to increase ketogenesis within the liver.

The metabolic and cardiovascular effects of recombinant human IGF-I were compared to insulin in six normal subjects. Subjects were studied twice and intravenously received an infusion of [6,6-2H2]glucose (0-480 min) and in random order either IGF-I 20 micrograms kg-1 h-1 (43.7 pmol kg-1 min-1 or insulin 0.5 mU kg-1 min-1 (3.4 pmol kg-1 min-1) with an euglycaemic clamp. One subject was withdrawn following a serious adverse event. During the IGF-I infusion glucose appearance rate (Ra) decreased from 1.79 +/- 0.13 at baseline (150-180 min) to 0.35 +/- 0.26 mg kg-1 min-1 (P < 0.01) at 360 min, and glucose utilization rate (Rd) increased from 1.79 +/- 0.28 to 4.17 +/- 0.84 mg kg-1 min-1 (P < 0.01). There was no change in free fatty acids (FFA) and an increase (percentage change from pre-infusion mean) in cardiac output +l37.3% +/- 9% (P < 0.01), heart rate +13% +/- 2% (P < 0.01) and stroke volume +21% +/- 7% (P < 0.05). During the insulin infusion glucose Ra decreased from 1.89 +/- 0.13 to 0.34 +/- 0.33 mg kg-1 min-1 (P < 0.01) and FFA from 0.546 mmol l-1 to 0.198 mmol l-1 (P < 0.01), glucose Rd increased from 1.89 +/- 0.18 to 5.41 +/- 1.47 mg kg-1 min-1 (P < 0.01) and there were no significant changes in the cardiovascular variables.

Background and aims: Recent data suggest that the use of insulin to maintain intensive glycaemic control amongst surgical ICU patients can improve morbidity and mortality. The value of this procedure in non-surgical patients is not known. Current insulin therapy for non-surgical patients in many ICUs aims to keep plasma glucose below 9 mmolll. The effect of this insulin therapy protocol on the catabolic response of critical illness, characterised by increased glucose production, increased lipolysis and proteolysis is unknown. Materials and methods: A prospective study was conducted in seven critically ill non-surgical patients (6M:1F, age 64±2.72 years; BMI 24.77 ± 0.77 kg/m2) within 36 hours of their admission to the ICU. Patients with diabetes mellitus, pancreatitis, oral steroid use within 1 month of entering the ICU, or liver disease (LFTs > twice normal range), were excluded. All patients were receiving 20% dextrose intravenously to provide 25kcal.kg-lday-l. Insulin was infused at a variable rate to maintain plasma glucose below 9 mmollL. Glucose production rate (Ra) and rate of uptake (Rd), glycerol Ra (a measure oflipolysis) and leucine Ra (a measure of proteolysis) were measured with a 3 hour primed infusion of [6,6- 2H2]glucose (l70mg, 1.7mg.min-I), [2H5]glycerol (0.15mg/kg, 0.61mg· kg-lhc1) and [l-l3C]leucine (1 mg/kg, 1 mg.kg-lhcl). Steady state sampling was performed at 150 to 180 minutes. Results are compared with fasting values from an age and weight matched healthy control group. All data presented are mean ± SEM. Results: The mean APACHE II score on the day of study was 15.43 ± 1.87. Mean plasma glucose at steady state was 7.95±0.73mmol· L-l. The mean glucose infusion rate was 22.83 ± 0.74 f.lmol.kg-lmin-l. The average insulin infusion rate was 4.31 ±0.73 U.hr-l which achieved plasma insulin concentrations of 655.21 ± 181.38 pmol.L-I. Endogenous glucose Ra was decreased (2.24±3.02f.lmol.kg-lmin-l, p

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 net catabolic effect of glucocorticoids on protein metabolism is well documented but the acute and chronic effect of glucocorticoids on protein breakdown remains controversial. In the present studies protein breakdown was measured by the release of tyrosine from the isolated soleus and extensor digitorum longus (EDL) muscles of control rats and rats treated with corticosterone (10 mg/100 g body weight/day) for 5 days. The effect of corticosterone in arresting growth was confirmed since corticosterone-treated rats weighed significantly less than control rats after 2, 3, 4 and 5 days of treatment (P < 0.001). Furthermore, the weights of soleus and EDL muscles from corticosterone-treated rats were significantly reduced (P < 0.001, at least P < 0.05 respectively) compared with muscles from control rats on days 3-5. In the EDL muscle tyrosine release was significantly elevated after corticosterone treatment for 2 days (257 +/- 21 nmol/g tissue/h, P < 0.05), 3 days (205 +/- 9 nmol/g tissue/h, P < 0.01), 4 days (255 +/- 20 nmol/g tissue/h, P < 0.005) and 5 days (218 +/- 8 nmol/g tissue/h, P < 0.05) compared with EDL from control rats (192 +/- 13, 171 +/- 7, 187 +/- 7, 180 +/- 12 nmol/g tissue/h respectively). In the soleus muscle, tyrosine release was significantly elevated after corticosterone treatment for 2 days (226 +/- 14 nmol/g tissue/h, P < 0.001), 3 days (223 +/- 16 nmol/g tissue/h, P < 0.001) and 4 days (199 +/- 10 nmol/g tissue/h, P < 0.001) compared with control rats (158 +/- 7, 132 +/- 6 and 153 +/- 7 nmol/g tissue/h respectively). After 5 days there was no significant difference in tyrosine release from soleus muscle between corticosterone-treated (176 +/- 15 nmol/g tissue/h) and control rats (157 +/- 6 nmol/g tissue/h). Plasma glucose concentrations were not significantly different in rats treated with corticosterone and control rats whilst insulin levels were significantly raised in the corticosterone-treated rats on all days compared with control rats (P < 0.05 on day 1; P < 0.001 on days 2, 3, 4 and 5). It is suggested that insulin may have prevented hyperglycaemia developing in the corticosterone-treated rats. Results from these studies indicate that the acute effect of glucocorticoids is to increase muscle proteolysis but this is not maintained with longer-term treatment.

Net protein loss and large decreases in plasma glutamine concentration are characteristics of critical illness. We have used [2-15N]glutamine and [1-13C]leucine to investigate whole body glutamine and leucine kinetics in a group of critically ill patients and matched healthy controls. Glutamine appearance rate (Ra,Gln) was similar in both groups. However, in the patients, the proportion of Ra,Gln arising from protein breakdown was higher than in the control group (43 +/- 3 vs. 32 +/- 2%, P < 0.05). Glutamine metabolic clearance rate (MCR) was 92 +/- 8% higher (P < 0.001), whereas plasma glutamine concentration was 38 +/- 5% lower (P < 0.001) than in the control group. Leucine appearance rate (whole body proteolysis) and nonoxidative leucine disposal (whole body protein synthesis) were 59 +/- 14 and 49 +/- 15% higher in the patients (P < 0.001). Leucine oxidation and MCR were increased in the patients by 104 +/- 37 and 129 +/- 39%, respectively (P < 0.05). These results demonstrate that critical illness is associated with a major increase in protein turnover. The acute decrease in plasma glutamine concentration and the unaltered plasma Ra,Gln suggest that the increase in proteolysis is insufficient to meet increased demand for glutamine in this severe catabolic state.

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.

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.

Background and Aims: Evidence suggests that tight glycaemic control in critically ill patients can improve morbidity and mortality. The mechanism( s) underlying its benefit remain speculative but might involve an amelioration of catabolism. This study was designed to differentiate the contribution of the insulin dose to the level of glycaemia achieved, on the catabolic response. Materials and Methods: A prospective study was conducted in 16 critically ill patients. Subjects with diabetes mellitus, pancreatitis, or liver disease were excluded. Patients were studied on 2 occasions, 48 hours apart. The baseline study was within 36 hours of admission to the ICU with blood glucose at 7–9 mmol/L. Patients were then randomised to one of four groups: Variable insulin with plasma glucose 4–6 mmol/L (LILG); Variable insulin with plasma glucose 7–9mmol/L (LIHG); High-dose insulin (2mU· kg–1·min–1 plus requirement from baseline) and variable dextrose to maintain glucose 4–6 mmol/L (HILG); High-dose insulin and variable dextrose to maintain glucose 7–9 mmol/L (HIHG). Glucose production rate (Ra) and leucine Ra (a measure of protein degradation) were measured with a 3-hour infusion of [6,62H2]glucose and [1-13C]leucine. Steady state sampling was performed at 150 to 180 mins. Endogenous glucose Ra was calculated by subtracting the dextrose infusion rate from total glucose Ra. Leucine oxidation rate (Ox) was calculated from CO2 enrichment and CO2 production rate.Non-oxidative leucine disposal (a measure of protein synthesis) was calculated as leucine Ra minus leucine Ox. Non-esterified fatty acid concentrations provide an estimate of lipolysis. Results: Protein turnover data (mean±SEM) was compared with 12 fasted age-matched controls. Glucose turnover data was compared to a separate control group of 8 subjects. Conclusions: Amongst non-surgical ICU admissions, the use of insulin to achieve less-stringent glycaemic targets was able to suppress glucose Ra and lipolysis and increase glucose uptake. No further suppression of glucose Ra was found with high dose insulin or with tighter glycaemic control. Leucine Ra was not decreased, even by pharmacological doses of insulin, whereas glucose Rd was significantly increased in the HILG and HIHG groups. These results suggest that the use of insulin to achieve normoglycaemia in the critical care setting does not promote whole body protein anabolism.

During critical illness glutamine deficiency may develop. Glutamine supplementation can restore plasma concentration to normal, but the effect on glutamine metabolism is unknown. The use of growth hormone (GH) and insulin-like growth factor I (IGF-I) to prevent protein catabolism in these patients may exacerbate the glutamine deficiency. We have investigated, in critically ill patients, the effects of 72 h of treatment with standard parenteral nutrition (TPN; n = 6), TPN supplemented with glutamine (TPNGLN; 0.4 g x kg(-1) x day(-1), n = 6), or TPNGLN with combined GH (0.2 IU. kg(-1). day(-1)) and IGF-I (160 microg x kg (-1) x day(-1)) (TPNGLN+GH/IGF-I; n = 5) on glutamine metabolism using [2-(15)N]glutamine. In patients receiving TPNGLN and TPNGLN+GH/IGF-I, plasma glutamine concentration was increased (338 +/- 22 vs. 461 +/- 24 micromol/l, P < 0.001, and 307 +/- 65 vs. 524 +/- 71 micromol/l, P < 0.05, respectively) and glutamine uptake was increased (5.2 +/- 0.5 vs. 7.4 +/- 0.7 micromol x kg(-1) x min(-1), P < 0.05 and 5.2 +/- 1.1 vs. 7.6 +/- 0.8 micromol x kg(-1) x min(-1), P < 0.05). Glutamine production and metabolic clearance rates were not altered by the three treatments. These results suggest that there is an increased requirement for glutamine in critically ill patients. Combined GH/IGF-I treatment with TPNGLN did not have adverse effects on glutamine metabolism.

Insulin-like growth factor I (IGF-I) is thought to mediate the anabolic action of growth hormone. A glucose and amino acid clamp technique was used to investigate the effects of a 3-h intravenous infusion of either 43.7 pmol · kg-1 · min-1 (20 μg · kg-1 · h-1) IGF-I or 3.4 pmol · kg-1 · min-1 (0.5 mU · kg-1 · min-1) insulin on whole body leucine turnover in five normal human volunteers. During the IGF-I infusion, IGF-I levels increased (P < 0.01; 26.6 ± 2.8 to 88.9 ± 14.2 nmol/l) and insulin levels fell (P < 0.05; 0.096 ± 0.018 to 0.043 ± 0.009 nmol/l). During the insulin infusion, insulin levels increased (P < 0.01; 0.057 ± 0.013 to 0.340 ± 0.099 nmol/l), and there was no change in IGF-I. There was no significant change in leucine production rate (R(a); a measure of protein degradation) during the IGF-I infusion (2.23 ± 0.17 to 2.13 ± 0.2 μmol · kg-1 · min-1), but there was an increase (P < 0.03) in nonoxidative leucine disposal rate (R(d); a measure of protein synthesis; 1.83 ± 0.15 to 2.05 ± 0.21 μmol · kg-1 · min-1). In contrast, insulin reduced (P < 0.02) leucine R(a) (1.81 ± 0.24 to 1.47 ± 0.24 μmol · kg-1 · min-1) and had no effect on nonoxidative leucine R(d) (1.44 ± 0.25 to 1.41 ± 0.22 μmol · kg-1 · min-1). We conclude that IGF-I under conditions of adequate substrate supply, directly increases protein synthesis in contrast to insulin, which exerts its anabolic action by reducing proteolysis.

Mitochondrial encephalomyopathy is a genetic disorder for which there is at present no cure. Conventional treatment regimes may not be effective in preventing weight loss and muscle wasting in many patients. Recombinant human GH has been shown to have anabolic effects on protein metabolism and to reduce muscle wasting in various diseases. We have treated a patient known to have myoclonus, epilepsy with ragged red fibres (MERRF) with a high protein diet for 1 month followed by a high protein diet and GH therapy for 1 month. To assess the benefit of these treatments the patient underwent whole body protein turnover, myometric and body composition studies at baseline, following the high protein diet (100 g/day) and following GH therapy. Whole body protein synthesis (and protein breakdown) increased following a high protein intake and was further enhanced by treatment with GH and in a high protein diet. Body composition did not change significantly following treatment with either the high protein diet or GH but there was an improvement in muscle performance following GH treatment. Mitochondrial encephalomyopathy, a wasting disorder, may be a disease in which the known protein anabolic effect of GH may have a therapeutic benefit.

Our understanding of HDL metabolism would be enhanced by the measurement of the kinetics of preβHDL, the nascent form of HDL, since elevated levels have been reported in patients with coronary artery disease. Stable isotope methodology is an established technique that has enabled the determination of the kinetics (production and catabolism) of total HDL apoA-I in vivo. The development of separation procedures to obtain a preβHDL fraction, the isotopic enrichment of which could then be measured, would enable further understanding of the pathways in vivo for determining the fate of preβHDL and the formation of αHDL. A method was developed and optimised to separate and measure preβHDL and αHDL apoA-I enrichment. Agarose gel electrophoresis was first used to separate lipoprotein subclasses, and then a 4-10 % discontinuous SDS-PAGE used to isolate apoA-I. Measures of preβHDL enrichment in six healthy subjects were undertaken following an infusion of L-[1-13C-leucine]. After isolation of preβ and αHDL, the isotopic enrichment of apoA-I for each fraction was measured by gas chromatography-mass spectrometry. PreβHDL apoA-I enrichment was measured with a CV of 0.51 % and aHDL apoA-I with a CV of 0.34 %. The fractional catabolic rate (FCR) of preβHDL apoA-I was significantly higher than the FCR of aHDL apoA-I (p < 0.005). This methodology can be used to selectively isolate preβ and aHDL apoA-I for the measurement of apoA-I isotopic enrichment for kinetics studies of HDL subclass metabolism in a research setting. © AOCS 2012.

Growth hormone (GH) treatment of GH-deficient adults increases lean body mass. To investigate this anabolic effect of GH, body composition and postabsorptive and postprandial protein metabolism were measured in 12 GH-deficient adults randomized to placebo or GH treatment. Protein metabolism was measured after an infusion of [1-13C]leucine before and after a standard meal at 0 and 2 mo. After 2 mo, there was an increase in lean body mass in the GH group (P < 0. 05) but no change in the placebo group. In the postabsorptive state, there was increased nonoxidative leucine disappearance (NOLD; a measure of protein synthesis) and leucine metabolic clearance rate and decreased leucine oxidation in the GH group (P < 0.05) but no change in the placebo group. After the meal, there was an increase in NOLD and oxidation in all studies (P < 0.05), but the increase in NOLD, measured as area under the curve, was greater in the GH group (P < 0.05). This study clearly demonstrates for the first time that the increase in protein synthesis in the postabsorptive state after GH treatment of GH-deficient adults is maintained in the postprandial state.

Background and aims: Adaptive changes in fatty acid metabolism, liver and muscle fat content and adipocyte-derived cytokines may potentially explain the beneficial effects of exercise on insulin action. We investigated this in sedentary men before and after 6 weeks of supervised exercise. Materials and methods: Thirteen sedentary overweight male subjects (age 50 ± 304yr, BMI 28.2 ± 0.5) were recruited, seven were randomised to a 6 week exercise programme and six remained sedentary. After completion of the baseline (0 weeks) metabolic study and body composition measurements subjects who were allocated to the exercise group started the exercise programme. Subjects exercised at 60-85% ofV02 max for a minimum of 20 minutes at least 3 times a week for 6 weeks. Insulin sensitivity of fatty acid (NEFA) production rate (Ra), glycerol Ra, glucose Ra and glucose disposal rate (Rd) were measured with stable isotopes of palmitic acid, glycerol and glucose at 0 and 6 weeks with a 2 step hyperinsulinaemic euglycaemic clamp (step 1, 0.3 (low dose); step 2, 1.5 (high dose) mU. kg-I. min-I). Intrahepatocellular lipid (IHCL) and intramyocellular lipid (IMCL) were measured by magnetic resonance spectroscopy and visceral fat by cross-sectional CT scanning. Results: In the exercise group V02 max increased by 20 ± 5% after 6 weeks (p

Gestational diabetes affects 2-3% of pregnant women and is associated with foetal complications including macrosomia and an increased likelihood of developing diabetes in later life. We have therefore studied seven women with gestational diabetes and five control women both during the third trimester of pregnancy and again 2-3 months post-partum, using the minimal model analysis of the frequently sampled labelled ([6,6-2H2]-glucose) intravenous glucose tolerance test. Glucose tolerance (glucose Kd) was significantly reduced in the women with gestational diabetes compared with the normal pregnant women both in pregnancy (1.16 +/- 0.11 vs 1.78 +/- 0.23%/min; p < 0.05) and post-partum (1.47 +/- 0.22 vs 2.59 +/- 0.43%/min; p < 0.05) and increased significantly in the control women after delivery (p < 0.05). Glucose effectiveness was not significantly different between the women with gestational diabetes and the control group either during or after pregnancy. Insulin sensitivity was significantly lower during pregnancy than after delivery in the women with gestational diabetes (p < 0.05). There was no significant difference in basal insulin secretion in the two groups during pregnancy or post-partum. However, during pregnancy the control subjects significantly increased (p < 0.001) their insulin secretion over a period of 20 min in response to an intravenous glucose tolerance test (96.2 +/- 42.7 pmol/kg) compared with post-partum values (58.3 +/- 25.2 pmol/kg) while in the women with gestational diabetes insulin secretion was similar in pregnancy (65.5 +/- 9.3 pmol/kg) and after delivery (57.7 +/- 15.7 pmol/kg). These data suggest that the glucose intolerance in gestational diabetes compared to normal pregnancy is due to reduced insulin sensitivity and an impaired ability in gestational diabetes to increase insulin secretion in response to glucose.

Based on a mass-balance model, a surrogate measure of the whole body leucine transport into and out of cells under steady-state conditions was calculated as u/DeltaTTR, where u is the infusion rate of (stable label) leucine tracer and DeltaTTR is the difference between the tracer-to-tracee ratio of extracellular and intracellular leucine. The approach was evaluated in ten healthy subjects [8 males and 2 females; age, 31 +/- 9 (SD) yr; body mass index, 24.0 +/- 1.6 kg/m2] who received a primed (7.58 micromol/kg) constant intravenous infusion (7.58 micromol. kg-1. h-1) of L-[1-13C]leucine over 180 min (7 subjects) or 240 min (3 subjects). Five subjects were studied on two occasions >/=1 wk apart to assess reproducibility. Blood samples taken during the last 30 min of the leucine infusion were used to determine plasma leucine concentration (129 +/- 35 micromol/l), TTR of leucine (9.0 +/- 1.5%), and TTR of alpha-ketoisocaproic acid (6.7 +/- 0.8%). The latter TTR was taken as the measure of the free intracellular leucine TTR. The whole body inward and outward transport was 6.66 +/- 3.82 micromol. kg-1. min-1; the rate of leucine appearance due to proteolysis was 1.93 +/- 0.24 micromol. kg-1. min-1. A positive linear relationship between the inward transport and plasma leucine was observed (P < 0.01), indicating the presence of the mass effect of leucine on its own transport. The transport was highly variable between subjects (between-subject coefficient of variation 57%) but reproducible (within-subject coefficient of variation 17%). We conclude that reproducible estimates of whole body transport of leucine across the cell membrane can be obtained under steady-state conditions with existing experimental and analytical procedures.

The effect of infusions of recombinant insulin-like growth factor-I (IGF-I) (34, 103 or 688 pmol kg-1 min-1), insulin (3.4, 10.3 or 68.8 pmol kg-1 min-1) or combined infusions (34 pmol IGF-I + 3.4 pmol kg-1 min-1 insulin or 103 pmol IGF-I + 3.4 pmol kg-1 min-1 insulin) on glucose metabolism was investigated in dogs using a [3-3H]-glucose infusion and euglycaemic clamp. All insulin doses decreased glucose production rate (Ra) in a dose-dependent manner (P < 0.05). All IGF-I doses decreased glucose Ra (P < 0.05) but this decrease was not dose dependent. The decrease in glucose Ra with the combined infusion of 34 pmol kg-1 min-1 IGF-I + 3.4 pmol kg-1 min-1 insulin was greater than 34 pmol kg-1 min-1 IGF-I (P < 0.05) but not different from 3-4 pmol kg-1 min-1 insulin. All insulin and IGF-I doses increased glucose utilization rate (Rd) in a dose-dependent manner (P < 0.01). The increase in glucose utilization was greater following both combined infusions than with either component infused alone (P < 0.05). Although at the doses selected, insulin and IGF-I had similar effects on glucose utilization with additive effects when the two peptides were combined, IGF-I was less effective than insulin in suppressing glucose production.

Insulin-like growth factor I (IGF-I) is thought to mediate the anabolic action of growth hormone. A glucose and amino acid clamp technique was used to investigate the effects of a 3-h intravenous infusion of either 43.7 pmol.kg-1.min-1 (20 micrograms.kg-1.h-1) IGF-I or 3.4 pmol.kg-1.min-1 (0.5 mU.kg-1.min-1) insulin on whole body leucine turnover in five normal human volunteers. During the IGF-I infusion, IGF-I levels increased (P < 0.01; 26.6 +/- 2.8 to 88.9 +/- 14.2 nmol/l) and insulin levels fell (P < 0.05; 0.096 +/- 0.018 to 0.043 +/- 0.009 nmol/l). During the insulin infusion, insulin levels increased (P < 0.01; 0.057 +/- 0.013 to 0.340 +/- 0.099 nmol/l), and there was no change in IGF-I. There was no significant change in leucine production rate (Ra; a measure of protein degradation) during the IGF-I infusion (2.23 +/- 0.17 to 2.13 +/- 0.2 mumol.kg-1.min-1), but there was an increase (P < 0.03) in nonoxidative leucine disposal rate (Rd; a measure of protein synthesis; 1.83 +/- 0.15 to 2.05 +/- 0.21 mumol.kg-1.min-1). In contrast, insulin reduced (P < 0.02) leucine Ra (1.81 +/- 0.24 to 1.47 +/- 0.24 mumol.kg-1.min-1) and had no effect on nonoxidative leucine Rd (1.44 +/- 0.25 to 1.41 +/- 0.22 mumol.kg-1.min-1). We conclude that IGF-I, under conditions of adequate substrate supply, directly increases protein synthesis in contrast to insulin, which exerts its anabolic action by reducing proteolysis.

A Nutrition Society member-led meeting was held on 9 January 2020 at The University of Surrey, UK. Sixty people registered for the event, and all were invited to participate, either through chairing a session, presenting a ‘3 min lightning talk’ or by presenting a poster. The meeting consisted of an introduction to the topic by Dr Barbara Fielding, with presentations from eight invited speakers. There were also eight lightning talks and a poster session. The meeting aimed to highlight recent research that has used stable isotope tracer techniques to understand human metabolism. Such studies have irrefutably shaped our current understanding of metabolism and yet remain a mystery to many. The meeting aimed to de-mystify their use in nutrition research.

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 of D-[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 X 10-2 ml·kg-1·min-1 per Mu/1; 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.

BACKGROUND: Dyslipidaemia and lipodystrophy have been described in treated HIV patients and in a small percentage of untreated HIV patients. Lipodystrophy in these patients has been shown to be associated with a lower expression of low density lipoprotein (LDL) receptors. METHODS: We have investigated the effect of antiretroviral treatment with either a protease inhibitor (PI) or a non-nucleoside reverse transcriptase inhibitor (NNRTI) on body fat distribution and LDL apolipoprotein B (apoB) kinetics in 12 HIV-negative controls and 52 HIV-infected patients, including antiretroviral treatment-naive (TN) patients (n=13) and patients taking two nucleoside analogues plus either a PI (n=15) or an NNRTI (n=24). RESULTS: LDL cholesterol was not different between groups. Compared with the controls, LDL apoB absolute synthetic rate (ASR) and fractional catabolic rate (FCR) were lower and residence time (RT) was higher in the PI and NNRTI groups (P