Effects of aerobic and resistance training on abdominal fat, apolipoproteins and high-sensitivity C-reactive protein in adolescents with obesity: the HEARTY randomized clinical trial.

OBJECTIVES: To investigate the effects of aerobic training, resistance training, or both on abdominal subcutaneous fat (subcutaneous adipose tissue (SAT)) (deep and superficial), visceral fat (visceral adipose tissue (VAT)), apolipoproteins A-1 and B (ApoA-1, ApoB), ApoB/ApoA-1 ratio and high-sensitivity C-reactive protein (HSCRP) in post-pubertal adolescents with obesity. PARTICIPANTS: After a 4-week supervised moderate-intensity exercise run-in period, 304 postpubertal adolescents with overweight (body mass index (BMI) ⩾85th percentile for age and sex+diabetes risk factor) or obesity (⩾95th BMI percentile) aged 14-18 years were randomized to four groups for 22 weeks (5 months): aerobic training, resistance training, combined training or a non-exercising control. METHODS: This study used a randomized controlled design. All groups received dietary counseling designed to promote healthy eating with a maximum daily energy deficit of 250 kcal. Abdominal fat (SAT and VAT) at the level of the fourth and fifth lumbar vertebrae (L4-L5) was measured by magnetic resonance imaging and ApoA-1, ApoB and HSCRP were measured after a 12-h fast at baseline and after 6 months. RESULTS: Changes in SAT at L4-L5 were -16.2 cm(2) in aerobic (P=0.04 vs control), -22.7 cm(2) in resistance (P=0.009 vs control) and -18.7 cm(2) in combined (P=0.02 vs control). Combined training reduced ApoB levels from 0.81±0.02 to 0.78±0.02 g l(-1) (P=0.04 vs control) and ApoB/ApoA-1 ratio from 0.67±0.02 to 0.64±0.02 (P=0.02 vs control and P=0.04 vs aerobic). There were no significant differences in VAT, ApoA-1 or HSCRP levels between groups. CONCLUSIONS: Aerobic and resistance training and their combination decreased abdominal SAT in adolescents with obesity. Combined training caused greater improvements in ApoB/ApoA-1 ratio compared with aerobic training alone.

Vitamin supplementation and blood pressure in Type 2 diabetes.

AIMS: Vitamin D levels are inversely related to blood pressure. Given that low sun exposure can create a greater reliance on dietary sources of vitamin D, we aimed to determine whether dietary vitamin D and blood pressure associations differ between periods of low and high sun exposure. METHODS: Dietary intake, vitamin supplementation, blood pressure, and anthropometric parameters were assessed each season for 1 year (174 adults with Type 2 diabetes). Separate linear regression models were constructed for high and low sun exposure periods to examine associations of systolic blood pressure with dietary vitamin D intake and vitamin supplement use (adjusted for age, gender, BMI, ethnicity, smoking, alcohol, physical activity, antihypertensive medication and nutrient intake). Robustness of findings was confirmed with within-subject repeated measures analysis, including an interaction term for sun exposure period. RESULTS: Vitamin D intake from food sources was low year-round and no conclusive association with blood pressure was identified during either period. Systolic blood pressure was 5.1 mmHg lower during the low sun exposure period (95% CI 0.5-9.7) in daily supplement users compared with non-users. The interaction term between supplement use and sun exposure period was significant (low sun exposure* no supplement, P = 0.02). Systolic blood pressure was relatively stable in users (low and high sun exposure periods, respectively, mean ± SE: 135.2 ± 2.6 mmHg and 134.2 ± 2.5 mmHg), but not in non-users (140.2 ± 2.7 mmHg and 130.5 ± 2.5 mmHg). CONCLUSIONS: Vitamin supplementation may stabilize systolic blood pressure in adults with Type 2 diabetes across seasons.

Postprandial hyperaminoacidaemia overcomes insulin resistance of protein anabolism in men with type 2 diabetes.

AIMS/HYPOTHESIS: Although protein is usually ignored when considering insulin resistance, we have shown resistance of protein concurrent with glucose metabolism in men with type 2 diabetes during a hyperinsulinaemic clamp at euglycaemia and fasting aminoacidaemia. We hypothesised that this resistance is even worse during conditions that simulate the postprandial state, when anabolism should be maximal. METHODS: Eight overweight and obese men with type 2 diabetes underwent a hyperinsulinaemic-hyperglycaemic (8 mmol/l) clamp, first with plasma amino acids at postabsorptive (Hyper-2) then at postprandial concentrations (Hyper-3). Whole-body protein kinetics were assessed using L-: [1-(13)C]leucine. Hyper-2 results were compared with those of diabetic men whose plasma glucose was lowered to 5.5 mmol/l and fasting aminoacidaemia maintained during the hyperinsulinaemic clamp (Hyper-1). RESULTS: In Hyper-2 vs Hyper-1 clamps, leucine flux (2.99 ± 0.16 vs 2.62 ± 0.06 µmol kg [fat-free mass (FFM)](-1) min(-1)), rates of synthesis (2.31 ± 0.15 vs 1.98 ± 0.06) and breakdown (2.38 ± 0.16 vs 2.00 ± 0.07) were higher (p < 0.05), but leucine oxidation and net balance did not differ. In Hyper-3 vs Hyper-2 clamps, leucine flux and synthesis and oxidation rates increased markedly as did net balance (0.84 ± 0.09 vs -0.07 ± 0.04 µmol [kg FFM](-1) min(-1), p < 0.0001). CONCLUSIONS/INTERPRETATION: In type 2 diabetic men, insulin resistance of protein metabolism is of the same magnitude at 8 vs 5.5 mmol/l, but turnover rates are higher with hyperglycaemia. Contrary to our hypothesis, sustained postprandial-level hyperaminoacidaemia stimulated positive net protein balance comparable with that previously found in lean non-diabetic men. This was sufficient to overcome the insulin resistance of protein anabolism.

Hyperaminoacidaemia at postprandial levels does not modulate glucose metabolism in type 2 diabetes mellitus.

AIMS/HYPOTHESIS: Hyperaminoacidaemia attenuates glucose disposal during hyperinsulinaemic clamps in healthy lean individuals, an effect thought to be mediated by negative feedback on insulin signalling, downstream of the mammalian target of rapamycin (mTOR) signalling pathway. This has been interpreted as amino acids causing insulin resistance in healthy people, and contributing to it in type 2 diabetes. However, the effect of hyperaminoacidaemia on glucose disposal in type 2 diabetic individuals remains to be determined. METHODS: Eight obese men with type 2 diabetes underwent a two-step hyperinsulinaemic-hyperglycaemic (8 mmol/l) clamp, first with amino acids at postabsorptive concentrations, followed by postprandial concentrations. Whole-body glucose turnover was assessed using D: -[3-(3)H]glucose. Vastus lateralis biopsies were obtained at baseline and during each step of the clamp to determine the phosphorylation states of AKT, mTOR, ribosomal protein (rp) S6, and insulin receptor substrate (IRS)-1. RESULTS: Rates of glucose infusion (1.30 ± 0.19 vs 1.15 ± 0.13 mmol/min), endogenous glucose production (0.48 ± 0.06 vs 0.53 ± 0.05 mmol/min) and disposal (1.24 ± 0.17 vs 1.17 ± 0.14 mmol/min) did not differ between postabsorptive and postprandial amino acid concentrations (p > 0.05). Whereas phosphorylation of AKT(Ser473), AKT(Thr308) mTOR(Ser2448) and rpS6(Ser235/236) increased (p < 0.05) with elevated amino acids, that of IRS-1(Ser636/639) and IRS-1(Ser1101) did not change. CONCLUSIONS/INTERPRETATION: Postprandial circulating amino acid concentrations do not worsen the already attenuated glucose disposal in hyperglycaemic type 2 diabetic men, and cell-signalling events are consistent with this. Our results do not support recommendations to restrict dietary protein in type 2 diabetes.

Antihyperglycaemic medication modifies factors of postprandial satiety in type 2 diabetes.

AIM: Type 2 diabetes is characterized by hyperglycaemia, delayed gastric emptying and a blunted response of gut hormones during feeding that may modulate satiety. We hypothesized that it is associated with more hunger when treated by medication. METHODS: We studied nine type 2 diabetic men (A1C: 6.7+/-0.3%, waist circumference: 104+/-4 cm) after an overnight fast, during 5 h in response to a 2.88 MJ breakfast, twice, in a crossover design, with or without antihyperglycaemic agents. Satiety ratings, thermic effect of meal, gastric emptying, plasma concentrations of gut peptides, leptin, insulin and substrates and intake from a subsequent buffet were determined. RESULTS: With medication, fasting and postprandial plasma glucose levels were lower but area under the curve (AUC) did not vary vs. without medication. Gastric emptying was shortened, branched chain amino acids (BCAA) AUC and thermic effect were lower, and postprandial glucagon-like peptide-1 (GLP-1) and peptide tyrosine tyrosine (PYY3-36) were maintained at higher levels beyond 4 h. Correlations were significant between duration of diabetes and fasting ghrelin (r=0.779, p=0.013) and peak insulin (r=-0.769, p=0.016), 5-h postmeal ghrelin and peak glucose (r=0.822, p=0.007), 5-h glucose and GLP-1 (r=-0.788, p=0.012), and 5-h hunger scores and energy intake at buffet (r=0.828, p=0.006). Without medication, fullness scores correlated with BCAA levels. Visual analogue scale scores, ghrelin and leptin levels did not differ between studies. CONCLUSIONS: The decrease in factors associated with postprandial satiety with treatment is counterbalanced by higher GLP-1 and PYY3-36. Medication may normalize the link between perception of hunger and subsequent food intake.

Protein turnover and requirements in the healthy and frail elderly.

There are as yet no definitive data that warrant the establishment of evidence-based dietary protein recommendations for the elderly. We reviewed the relevance of the new 2002 recommended protein intake of 0.80 g/kg body weight.d for adults to healthy and frail elderly persons. We found that data from published nitrogen balance studies indicate that, a higher protein intake of 1.0 - 1.3 g/k.d is required to maintain nitrogen balance in the healthy elderly, which may be explained by their lower energy intake and impaired insulin action during feeding compared with young persons. Although it needs to be confirmed, a decrease in efficiency of protein utilization with aging may also dictate a higher protein-intake recommendation. Measures of the dynamic aspects of protein metabolism done in the postabsorptive state have shown no change in whole body protein turnover per unit of active metabolic tissue with aging. However, the contribution of muscle protein to wholebody protein metabolism was significantly reduced in the elderly, and explained by their reduced muscle mass and lower rates of myofibrillar protein turnover. Consequently, the contribution of nonmuscle protein, especially that of visceral tissue whose rates of protein turnover are known to be more rapid was proportionally greater with aging. It is conceivable that higher protein consumption rates could compensate for the decrease in availability of muscle amino acids and spare the muscle mass. Despite a paucity of data on the frail elderly population, we present a rationale to justify a greater protein intake of at least equivalent to that of their healthy counterparts. We propose that higher protein intakes for the elderly, and especially the frail population, than those presently recommended may minimize the sarcopenia of aging and thereby protect against some of the health risks of aging.

Effect of NIDDM on the kinetics of whole-body protein metabolism.

We postulated that dietary protein utilization and body protein metabolism are altered in hyperglycemic individuals with non-insulin-dependent diabetes mellitus (NIDDM). This was tested by estimating the kinetics of protein metabolism in obese NIDDM patients in the hyperglycemic state of isoenergetic feeding and in the normoglycemic state induced by the prolonged use of a very-low-energy diet (VLED) and comparing them with results in obese nondiabetic subjects studied previously. Seven obese subjects with NIDDM (one male, six females, body mass index = 35.8 +/- 2.0 kg/m2) were given a 1.7 MJ (410 kcal) all protein (93 g/day) diet derived from hydrolyzed collagen and supplemented with tryptophan and methionine, which provides 16% of its amino acids as essential, a multivitamin and mineral supplement, and 16 mmol KCl for 42 days. During the seven-day isoenergetic diet and at weeks 4 and 6 of the VLED, amino nitrogen (N) flux rate was calculated from the urine [15N]urea enrichment by using the 60-h oral [15N]glycine method to obtain the integrated feeding-fasting metabolism. Rates of synthesis (S) and breakdown (B) were calculated from N flux. At day 7 of the isoenergetic diet, whole-body N flux, S, B, and resting metabolic rate (RMR) were 12-24% greater (P < 0.05) in the NIDDM subjects than observed in nondiabetic obese subjects. Mean plasma glucose decreased (P < 0.05) from the isoenergetic period (14.9 +/- 2.4 mM) to 7.2 +/- 1.2 mM at week 4 and 6.5 +/- 1.1 mM at week 6 of the VLED. RMR declined progressively by 25% at week 5 of the VLED. Corresponding significant (P < 0.05) decreases from isoenergetic feeding to weeks 4 and 6 of the VLED occurred in whole-body N flux (from 51 +/- 2 to 42 +/- 1 g N/day), in S (from 38 +/- 3 to 24 +/- 1 g N/day), and in B (from 39 +/- 3 to 26 +/- 1 g N/day) resulting in net losses (S-B). S-B was significantly more negative (P < 0.05) in NIDDM than in the nondiabetic obese subjects at week 4 (-1.5 +/- 0.5 vs. 0.9 +/- 0.3 g N/day) but not at week 6 (-1.3 +/- 0.4 vs. -0.9 +/- 4 g N/day). During the VLED, N balance became less negative with time but never reached equilibrium in NIDDM. Thus, abnormal protein metabolism is present in NIDDM in the isoenergetic fed state with moderate hyperglycemia and persists during a VLED that restores glycemia to near normal.

Effects of oral hypoglycemic agents and diet on protein metabolism in type 2 diabetes.

OBJECTIVE: We tested whether oral hypoglycemic agents (OHA), gliclazide with or without metformin, during an isoenergetic (ISO) and then a low-energy diet (LED) improve the altered kinetics of whole-body protein metabolism in type 2 diabetes. RESEARCH DESIGN AND METHODS: A total of 13 type 2 diabetic patients (aged 51+/-2 years, weight 110+/-5 kg, BMI 41+/-1 kg/m2, fasting glucose [FSG] 11.5+/-0.9 mmol/l) (means+/-SEM) and 10 obese control subjects (48+/-3 years, 98+/-6 kg, 37+/-2 kg/m2, FSG 5.5+/-0.3 mmol/l) consumed an ISO, 1.5 g x kg(-1) x day(-1) protein for a body weight corresponding to a BMI of 25 (BMI25), a formula diet (7 days for obese control subjects, 15 days for diabetic patients), and then a 28-day LED with 50% of the energy of ISO but the same protein intake (101+/-2 g/day). OHAs were given during ISO (days 8-15) and LED. On days 6-8 (and 12-14 for diabetic subjects) of ISO and 26-28 of LED, the 60-h oral 15N-glycine method was used to obtain nitrogen flux (Q), synthesis (S), and breakdown (B). Muscle protein catabolism was estimated from N(tau)-methylhistidine (3MH) excretion. RESULTS: During ISO with hyperglycemia, Q, and B adjusted for fat-free mass, sex, and age were higher and nitrogen balance and net endogenous protein synthesis (S-B) lower than in control subjects (P<0.05). OHA decreased FSG (9+/-1 mmol/l) and 3MH and increased plasma insulin-to-glucose ratio, nitrogen retention, and S-B to levels in control subjects. The change in S-B correlated with that in FSG (r = -0.845, P = 0.001) and in fasting plasma C-peptide (r = 0.852, P = 0.0005). With LED and OHA, weight decreased 6.3 kg, glycemia reached near-normal levels, and nitrogen equilibrium was maintained; Q decreased by 7%, S and B by 11% (P<0.05) to values found in control subjects. CONCLUSIONS: OHA during ISO corrected protein turnover in relation to glycemia and plasma C-peptide. The LED maintained protein homeostasis in obese control subjects and, in diabetes patients with OHA, normalized protein metabolism. These findings have implications for diet and OHA prescription.

Effects of sodium supplementation during energy restriction on plasma norepinephrine levels in obese women.

We tested whether sodium restriction would counteract the decrease in sympathetic nervous system activity usually associated with marked energy restriction. The effects of two levels of energy restriction, with different sodium intakes, on plasma norepinephrine (NE) levels while supine and in response to standing were studied. Twenty-two healthy normotensive obese female subjects (body mass index, 34 +/- 1 kg/m2; weight, 90 +/- 2 kg) followed one of three 3-week protocols: 1) total fasting with 80 mmol/day NaCl, 2) a very low energy diet (VLED) containing 1.7 MJ, 93 g protein, and 90 mmol Na/day, with an additional 60 mmol/day NaCl supplement, or 3) total fasting without NaCl (0 Na fast). At the end of the baseline isocaloric diet and of total fasts or VLED, pulse, blood pressure, and plasma NE were measured after 4 h of recumbency and 5 and 10 min after assuming the upright posture. These measurements were repeated after 1 L physiological saline was infused into the 0 Na fast subjects. Cumulative negative sodium balance was observed only in the 0 Na fasting subjects. Supine blood pressure decreased from baseline with fasting, but not with the VLED. The decreases in systolic pressure and increases in heart rate on standing observed with all diets were greatest with the 0 Na fast. Supine plasma NE (vs. baseline value) declined (P less than 0.05) with the VLED, remained unchanged with the Na supplemented fast, but increased with the 0 Na fast (P less than 0.05). The upright plasma NE values were highest in the 0 Na fast subjects, but lower after the saline infusion as well as in the subjects on the VLED. Thus, the decrease in NE due to energy restriction with normal sodium intake was counteracted by moderate sodium restriction, and levels increased with zero sodium intake. Therefore, sodium depletion can override the suppressive effect of energy restriction and, instead, increase the activity of the sympathetic nervous system, as reflected by plasma NE.

Thermic and metabolic responses to oral glucose in obese subjects with non-insulin-dependent diabetes mellitus treated with insulin or a very-low-energy diet.

Increased resting energy expenditure (REE) and a blunted thermic effect of glucose (TEF) have been reported in obese subjects with non-insulin-dependent diabetes mellitus (NIDDM). I questioned whether the abnormal REE and TEF would be corrected by normalizing glycemia with insulin or a very-low-energy diet (VLED). Three male and four female obese subjects with NIDDM [weighing 108 +/- 6 kg and with body mass index (in kg/m2) of 39 +/- 2] received a weight-maintaing formula diet containing 95 g protein/d for 15 d then a 1.7-MJ, 93-g-protein VLED for 27 d. Insulin was given from days 1 to 8 in doses sufficient to normalize glycemia. REE was measured weekly and TEF was measured on days 8 and 15 of isoenergetic feeding and 28 d after the VLED by using a ventilated-hood indirect calorimeter. Weight decreased 9.8 +/- 1 kg during the VLED. REE was 3% lower with insulin treatment than during hyperglycemia (7878 +/- 364 compared with 8125 +/- 381 kJ/d, P = 0.002). REE decreased by 20% to 6494 +/- 280 kJ/d by week 4 of the VLED. After 112 g oral glucose, increments in energy expenditure were significantly greater during isoenergetic feeding with insulin than without (7.5 +/- 1.3% compared with 4.3 +/- 0.9% above REE) and after the VLED (10.5 +/- 1.0% above REE, P < 0.05). Plasma glucose excursions were greatest without exogenous insulin (peak 21.5 +/- 1.8 mmol/L at 120 min, 16.3 +/- 1.9 mmol/L at 225 min). Plasma fatty acid excursions were the lowest with insulin treatment. The integrated plasma glucose and fatty acid responses above baseline did not differ among studies; the integrated insulin and C-peptide responses were greater after the VLED. Cumulative nonoxidative glucose disposal (stored glucose) was higher with insulin therapy than without (52 +/- 6 compared with 35 +/- 7 g/210 min, P < 0.05) and increased significantly to 66 +/- 6 g after the VLED (compared with the isoenergetic diet without insulin). TEF correlated significantly with integrated C-peptide and insulin responses. The percentage increase in TEF with euglycemia (with insulin and VLED) correlated with the percentage increase in stored glucose (P < 0.05). The greater TEF was associated with a greater insulin response, which was probably responsible for the greater stored glucose.

Changes in circulating leukocytes and mitogen responses during very-low-energy all-protein reducing diets.

Chronic and acute protein-energy malnutrition impairs immune function but little is known of the effects of energy deprivation alone. Indexes of cell-mediated immunity (CMI) were therefore studied during a 6-wk very-low-energy diet (VLED) (1.7 MJ/d, weight loss 13 +/- 1 kg, means +/- SEM) in 12 nondiabetic obese [body mass index 33 +/- 1 (in kg/m2)] subjects. Significant decreases (P less than 0.05) were observed in the numbers of total leukocytes, neutrophils, lymphocytes, and monocytes from 1 to 2 wk of the VLED and onward. Only lymphocyte counts returned to baseline levels with refeeding. The proportions of other monoclonal-antibody-defined mononuclear cell populations (except a small decrease in CD4+) did not change during dieting. [3H]Thymidine uptake by mononuclear cells cultured for 96 h decreased significantly (P less than 0.05) at wk 6 in response to concanavalin A, phytohemagglutinin, and pokeweed mitogen and after only 1 wk to phorbol myristate acetate + ionomycin. Delayed-type-hypersensitivity skin-test responses did not decrease at wk 5 vs those at baseline. The VLED produced nonspecific decreases in circulating leukocyte numbers and in vitro responses to several mitogens (of different cell-subset specificity), suggesting that in susceptible individuals or if there is longer exposure to such diets, such responses could assume clinical significance.

Effect of glycemic control on the kinetics of whole-body protein metabolism in obese subjects with non-insulin-dependent diabetes mellitus during iso- and hypoenergetic feeding.

We postulated whether interventions capable of restoring euglycemia would correct whole-body protein metabolism, shown previously to be elevated in hyperglycemic persons with non-insulin-dependent diabetes (NIDDM). The kinetics of protein metabolism were estimated in obese subjects with NIDDM in the hyper- and normoglycemic states during isoenergetic feeding and in the normoglycemic state induced by 4 wk of a very-low-energy diet (VLED) with constant protein intake. Seven NIDDM subjects [three males and four females with a body mass index (in kg/m2) of 39 +/- 2] were given a weight-maintaining, liquid formula providing 95 g protein/d for 15 d, followed in six subjects (two males and four females) for 27 d by a diet providing 1.7 MJ, 93 g protein derived from casein-soy, 13 g carbohydrate, 2 g fat, multivitamins and minerals, and a potassium bicarbonate supplement (32 mmol) per day. Exogenous insulin was given to achieve normoglycemia during the first 8 d of isoenergetic feeding. On days 6-8, 12-14, and 25-27, nitrogen flux rate was calculated from the urine [15N]urea enrichment by using the 60-h oral [15N]glycine method to obtain "integrated" feeding and fasting values. Rates of synthesis and breakdown were calculated from nitrogen flux. During isoenergetic feeding, normoglycemia was associated with more positive nitrogen balance (2.6 +/- 0.5 compared with -0.6 +/- 0.6 g N/d, P < 0.05); 18-23% lower nitrogen flux, and synthesis and breakdown rates (P < 0.05), and a 3% decrease in resting energy expenditure (P < 0.05). During the VLED, euglycemia was achieved but nitrogen balance, although it became less negative with time, never reached equilibrium. This was associated with significant (P < 0.05) decreases in the synthesis rate, resulting in net protein losses. Thus, the altered protein metabolism in moderately hyperglycemic NIDDM subjects was improved with exogenous insulin in doses sufficient to restore normoglycemia in the isoenergetic fed state, but it remained abnormal with a reduced non-protein energy intake. This suggests that protein metabolism is more sensitive to insulinization than was thought previously.

Protein metabolism in obese subjects during a very-low-energy diet.

We postulated that the return to nitrogen equilibrium after 3 wk of a negative balance during a very-low-calorie diet (VLCD) providing low-quality protein in obese subjects was due to availability of endogenously originating amino acids from a "pool" that, when depleted, would result in worsening balance. This should be reflected in altered kinetics of protein metabolism with the requirement for increased breakdown to maintain synthesis constant. Seven female obese subjects [body mass index (BMI) = 34.4 +/- 1.8 kg/m2] were given a 1.7-MJ/d all-protein diet (16.8 g N) derived from hydrolyzed gelatin (supplemented with tryptophan and methionine) that provides 18% of its amino acids as essential, a multivitamin-mineral supplement, and 16 mmol KCl for 42 d. At baseline (7-d isocaloric diet), and weeks 4 and 6 of VLCD, amino nitrogen flux rate was calculated from the 15N abundance in urinary urea using the oral 15N-glycine method and rates of synthesis (S) and breakdown (B) inferred from N flux. Whole-body N flux did not change from baseline to weeks 4 and 6 (39.5 +/- 2.0 vs 37.4 +/- 2.0 vs 39.2 +/- 1.9 g N/d). By contrast, S and B decreased at weeks 4 and 6 with S decreasing more so that net protein synthesis (S-B) was less positive at week 4 than at baseline (2.2 +/- 0.2 and 0.9 +/- 0.3 g N/d; P less than 0.05) and became negative at week 6 (-0.9 +/- 0.2 g N/d; P less than 0.05). Concurrently, N equilibrium was achieved by week 4 but returned to negative balance by week 6.(ABSTRACT TRUNCATED AT 250 WORDS)

Whole-body protein turnover in the healthy elderly.

We tested the hypothesis that aging affects whole-body protein turnover via altered fat-free mass (FFM). Whole-body protein kinetics were estimated by the 60-h oral [15N]glycine method. Results from 16 healthy, elderly subjects (8 men and 8 women with a mean age of 72.6 y) were compared for age and sex effects with those of 15 lean young subjects (8 men and 7 women with a mean age of 28.4 y) during isoenergetic formula diets. Per kilogram body weight, nitrogen flux was lower only as an effect of age (P = 0.006) whereas age and female sex significantly lowered synthesis and breakdown (P < or = 0.04). However, per kilogram FFM, no significant age or sex effects on rates of protein kinetics remained. Age and female sex contributed significantly to decreased muscle protein catabolism (based on 3-methylhistidine excretion), both in absolute terms and as a percentage of whole-body protein breakdown in the elderly compared with the young: 20.2% compared with 30.9% in women and 27.9% compared with 39.8% in men. No significant age or sex effects on rates of nonmuscle lean tissue protein breakdown were observed with or without correction for body composition. We conclude that the lower rates of flux, synthesis, and breakdown per kilogram body weight in elderly compared with young persons are due to changes in body composition with aging because rates are not different per kilogram FFM. However, there is a reduced contribution by muscle to whole-body protein catabolism in older persons. This has potential implications for the nutrition of both normal and sick elderly persons.

Effect of prolonged moderate and severe energy restriction and refeeding on plasma leptin concentrations in obese women.

BACKGROUND: Plasma leptin in humans is subject to both long- and short-term regulation; it correlates with indexes of body fat that can only change slowly. However, short-term fasting causes large and rapid decreases. OBJECTIVE: We tested the interactions between energy intake and fat loss on plasma leptin during prolonged moderate and severe energy restriction, with a view to understanding mechanisms of control. DESIGN: Postabsorptive leptin was measured with an enzyme-linked immunosorbent assay specific for the human peptide in 21 obese women aged 41 +/- 3 y (weight: 102 +/- 4 kg; 48 +/- 1% body fat) after 1 wk of a weight-maintaining diet and then weekly for 4 wk during a total fast (group 1); a 1.9-MJ/d all-protein, very-low-energy diet (VLED) (group 2); or a low-energy, balanced-deficit diet (BDD) providing 50% of maintenance energy (group 3). In groups 1 and 2, leptin was also measured after 1 wk of refeeding with a diet equivalent to the BDD. RESULTS: Mean leptin decreased markedly by up to 66% (P < 0.001) at week 1 of energy restriction and then gradually thereafter. The change in leptin per kilogram fat mass correlated with that in glucose concentrations [r = 0.538 (P = 0.012) at week 1 and r = 0.447 (P = 0.042) at week 4] but not with that in fat mass. During refeeding postfasting, leptin increased (P = 0.008), despite an ongoing loss of fat mass and correlated positively with changes in resting energy expenditure. At times with comparable cumulative energy restriction and fat loss between diets, the percentage change in leptin paralleled that in glucose. CONCLUSIONS: In obesity, changes in energy intake over days to weeks are a primary modulator of plasma leptin concentrations that are related to the change in glycemia and are able to override the regulatory influence of fat mass.

Circulating mononuclear cell numbers and function during intense exercise and recovery.

To investigate the effect of intense exercise on immune function, 12 healthy males (26 +/- 1 yr) underwent cycle exercise to exhaustion at 80% maximum work load. One hour later, six of the subjects underwent a second identical bout. Blood was drawn preexercise (C), at exhaustion (Ex-1, Ex-2), and at 1 h of recovery (Rec-1, Rec-2). At Ex-1 and Ex-2, total leukocytes (monocytes, neutrophils, and lymphocytes) increased significantly (P less than 0.05), and all returned to C levels by Rec-1 except lymphocytes, which were lower than at C. At Rec-2 total leukocytes remained higher (P less than 0.05) than at C, primarily because of elevated neutrophil counts. Phenotype analysis indicated a 2.5-fold increase in CD16+ (natural killer) cells at Ex-1 and a decrease primarily in CD4+ (T-helper) cells. All phenotype changes returned to C levels at Rec-1. At Ex-1 the in vitro mitogenic response to concanavalin A, phorbol myristate acetate + ionomycin, phytohemagglutinin, and pokeweed mitogen decreased (P less than 0.05) but returned to levels not different from C at Rec-1. Both the in vitro percent specific lysis of a target natural killer cell (K562) and the lytic activity per cell increased (P less than 0.05) in peripheral mononuclear cells at Ex-1, returning to C levels at Rec-1. The total leukocyte counts with exercise were significantly correlated with plasma epinephrine concentration, and a causal effect is thus possible. Such acute changes in numbers and function of circulating cells of the immune system may possibly have functional and clinical correlates.

Glucoregulatory and hormonal responses to repeated bouts of intense exercise in normal male subjects.

Glucose turnover and its regulation were studied during and after two identical bouts of intense exhaustive exercise separated by 1 h to define differences in response. Six lean young postabsorptive male subjects exercised at approximately 100% maximal O2 uptake (3.7 +/- 0.3 l/min) for 13.0 +/- 0.7 min for the first (EX1) and 13.2 +/- 0.8 min for the second (EX2) bout. Plasma glucose increased during EX1 and peaked at 7.0 +/- 0.6 mmol/l in early recovery but to 5.8 +/- 0.5 mmol/l (P less than 0.05) after EX2, and both the hyperglycemic and the hyperinsulinemic responses were less after EX2 (P less than 0.015, analysis of variance). The hyperglycemia was due to lesser increments in glucose utilization (Rd) (3-fold resting) than glucose production (Ra) (7-fold) toward exhaustion and for 7 min of recovery. The rise in Rd was more rapid (P less than 0.05) and metabolic clearance rate was greater during (P = 0.015) and from 9 to 60 min after EX2, and Ra also remained higher during recovery (P less than 0.05). Marked and similar increments in plasma norepinephrine (18-fold) and epinephrine (14-fold) occurred with both bouts. Plasma glucagon increments were small and not different. Therefore, 1) more circulating glucose was used with EX2, 2) greater metabolic clearance rate during and after EX2 suggests local muscle adaptations due to EX1, and 3) significant correlations (P less than 0.002) between plasma norepinephrine and Ra (r = 0.82) and Ra - Rd (r = 0.52) and between epinephrine and Ra (r = 0.71) and Ra - Rd (r = 0.48) suggest a major regulatory role for the catecholamine responses.

Healthy Eating, Aerobic and Resistance Training in Youth (HEARTY): study rationale, design and methods.

PURPOSE: The objective of the Healthy Eating Aerobic and Resistance Training in Youth (HEARTY) trial (ClinicalTrials.Gov # NCT00195858) was to examine the effects of resistance training, with and without aerobic training, on percent body fat in sedentary, post-pubertal overweight or obese adolescents aged 14-18 years. This paper describes the HEARTY study rationale, design and methods. METHODS: After a 4-week supervised low-intensity exercise run-in period, 304 overweight or obese adolescents with a body mass index≥85th percentile for age and sex were randomized to 4 groups for 22 weeks (5 months): diet+aerobic exercise, diet+resistance exercise, diet+combined aerobic and resistance exercise, or a diet only waiting-list control. All participants received dietary counseling designed to promote healthy eating with a maximum daily energy deficit of -250 kcal. OUTCOMES: The primary outcome is percent body fat measured by Magnetic Resonance Imaging. Secondary outcomes include changes in anthropometry, regional body composition, resting energy expenditure, cardiorespiratory fitness, musculoskeletal fitness, cardiometabolic risk markers, and psychological health. SUMMARY: To our knowledge, HEARTY is the largest clinical trial examining effects of aerobic training, resistance training, and combined aerobic and resistance training on changes in adiposity and cardiometabolic risk markers in overweight and obese adolescents. The findings will have important clinical implications regarding the role that resistance training should play in the management of adolescent obesity and its co-morbidities.

Elevations of plasma methylarginines in obesity and ageing are related to insulin sensitivity and rates of protein turnover.

AIMS/HYPOTHESIS: Increased circulating methylarginines (MA) have been linked to the metabolic syndrome to explain endothelial dysfunction and cardiovascular disease risk. Proteins that contain MA are regulatory and release them during catabolism. We hypothesised that increased protein turnover in insulin-resistant states contributes to an increase in circulating MA. MATWERIALS AND METHODS: We performed hyperinsulinaemic, euglycaemic, and isoaminoacidaemic experiments on 49 lean, obese and elderly subjects, with measurements of the kinetics of glucose and protein metabolism. Plasma MA, i.e. asymmetrical dimethylarginine (ADMA), symmetrical dimethylarginine (SDMA), and N -monomethyl-L-arginine (NMMA), lipids and body composition were measured. RESULTS: Insulin resistance of glucose and protein metabolism occurred in obese and elderly subjects. ADMA concentrations were 29 to 120% higher in obese and 34% higher in elderly than in lean subjects. SDMA were 34 and 20% higher in obese than in lean and than in elderly subjects, respectively. NMMA were 32% higher in obese than in lean subjects. ADMA differed by sex, being higher in men, namely by 1.75x in obese men and by 1.27x in elderly men. Postabsorptive ADMA (r=0.71), SDMA (r=0.46), and NMMA (r=0.31) correlated (all p<0.05) with rates of protein flux. All three MA correlated negatively with clamp glucose infusion rates and uptake (p<0.001). ADMA and SDMA correlated negatively with net protein synthesis and clamp amino acid infusion rates (p<0.05). All MA also correlated with adiposity indices and fasting insulin and triglycerides (p<0.05). CONCLUSIONS/INTERPRETATION: Obesity, sex and ageing affect MA. Elevations of the three MA in obese, and of ADMA in elderly men, are related to increased protein turnover and to lesser insulin sensitivity of protein metabolism. These interrelationships might amplify insulin resistance and endothelial dysfunction.

The metabolic response to two very low energy diets (VLED) of differing amino acid composition during weight reduction.

Nitrogen (N) sparing and even equilibrium have been achieved in obese subjects with all-protein weight-reducing very low energy diets (VLED) apparently independently of the content of essential amino acids. This study assessed whether the metabolic response observed at week 3 of an all-protein VLED with 46% of amino acids (aa) as essential was modified during week 4, when consuming a protein source that provided 16% of amino acids as essential. Six healthy obese subjects (BMI: 35.3 +/- 1.3 kg/m2, weight 90 +/- 9 kg) were given a 1.72 MJ (400 kcal) all protein (93 g) VLED and a multi-vitamin-mineral supplement daily for four weeks. During weeks 1 to 3, the protein was casein-soy (46% essential aa) and during week 4, tryptophan- and methionine-supplemented collagen hydrolysate (16% essential aa). At week 3, decreases in plasma glucose, insulin, cholesterol, blood pH and bicarbonate, and increases in plasma free fatty acids, serum urea, uric acid and blood and urine ketones occurred compared to baseline. These adaptations were unchanged at week 4. N balance returned toward equilibrium by day 23 remaining at values close to 0 despite the change in diet composition. Mean negative N balance did not differ between weeks 3 and 4 (-1.1 +/- 0.5 g vs. -0.6 +/- 0.5 g/day) and neither did mean urinary ammonium N excretion (0.71 +/- 0.08 vs. 0.73 +/- 0.07 g/day). Urinary urea N excretion tended to increase with the collagen-based diet reflecting the greater proportion of N in this protein source (18 vs. 15%).(ABSTRACT TRUNCATED AT 250 WORDS)