The catabolic effects of prolonged inactivity and acute hypercortisolemia are offset by dietary supplementation

We compared the anabolic stimulus provided by an essential amino acid and carbohydrate (AA/CHO) supplement to a mixed clinical meal during bed rest (BR) and episodic hypercortisolemia ( approximately 24 microg.dl(-1)). In the experimental (EXP; n = 7) and control (CON; n = 6) groups, femoral arteriovenous blood samples and vastus lateralis biopsy samples were obtained during a primed constant infusion of l-[ring-(2)H(5)]phenylalanine and a 14-h infusion of hydrocortisone sodium succinate (60 microg.kg.h(-1)) before (pre-BR) and after (post-BR) 28 d of BR. Muscle protein kinetics were calculated during the postabsorptive state, for 2.5 h after ingestion of a meal and for 2.5 h after ingestion of an AA/CHO supplement (EXP) or placebo (CON). Postabsorptive net phenylalanine balance values were as follows: EXP, -35.14 +/- 2.93, and CON, -32.60 +/- 6.65 (pre-BR); and EXP, -32.91 +/- 5.67, and CON, -30.43 +/- 6.28 nmol phe.ml(-1).100 ml leg volume(-1) (post-BR). After AA/CHO supplementation, net phenylalanine balance improved to 33.51 +/- 8.06 (pre-BR) and 24.15 +/- 11.4 nmol phe.ml(-1).100 ml leg volume(-1) (post-BR), but remained negative after the meal. Cumulative 5.5-h mixed muscle fractional synthetic rate was greater in the EXP group pre-BR (EXP, 0.108 +/- 0.01, and CON, 0.073 +/- 0.04%.h(-1)) and post-BR (EXP, 0.111 +/- 0.015, and CON, 0.05 +/- 0.002%.h(-1)). Unlike a typical clinical meal, AA/CHO supplementation stimulated net muscle protein synthesis despite acute hypercortisolemia and prolonged inactivity.     

Mitochondrial and sarcoplasmic proteins, but not myosin heavy chain, are sensitive to leucine supplementation in old rat skeletal muscle

Leucine has a major anabolic impact on muscle protein synthesis in young as in old animals. However, myosin heavy chain (MHC), sarcoplasmic and mitochondrial proteins may differently respond to anabolic factors, especially during aging. To test this hypothesis, fractional synthesis rates (FSR) of the three muscle protein fractions were measured using a flooding dose of [1-(13)C] phenylalanine, in gastrocnemius muscle of adult (8 months) and old (22 months) rats, either in postabsorptive state (PA), or 90-120 min after ingestion of a alanine-supplemented meal (PP+A) or a leucine-supplemented meal (PP+L). In adult and old rats, in comparison with PA, leucine stimulated mitochondrial (adult: 0.260+/-0.011 vs 0.238+/-0.012%h(-1); old: 0.289+/-0.010 vs 0.250+/-0.010%h(-1); PP+L vs PA, P<0.05) and sarcoplasmic (adult: 0.182+/-0.011 vs 0.143+/-0.006%h(-1); old: 0.195+/-0.010 vs 0.149+/-0.008%h(-1); PP+L vs PA, P<0.05) protein FSR, but not MHC synthesis in old rats (0.101+/-0.009 vs 0.137+/-0.018%h(-1); PP+L vs PA, P=NS). In conclusion, synthesis of specific muscle protein is activated by leucine supplementation, but MHC may be less sensitive to anabolic factors with aging.     

Liquid carbohydrate/essential amino acid ingestion during a short-term bout of resistance exercise suppresses myofibrillar protein degradation

A number of physiological events including the level of contractile activity, nutrient status, and hormonal action influence the magnitude of exercise-induced skeletal muscle growth. However, it is not the independent action of a single mechanism, but the complex interaction between events that enhance the long-term adaptations to resistance training. The purpose of the present investigation was to examine the influence of liquid carbohydrate (CHO) and essential amino acid (EAA) ingestion during resistance exercise and modification of the immediate hormonal response on myofibrillar protein degradation as assessed by 3-methylhistidine (3-MH) excretion. After a 4-hour fast, 32 untrained young men (18-29 years) performed a single bout of resistance exercise (complete body; 3 setsx10 repetitions at 75% of 1-repetition maximum; 1-minute rest between sets), during which they consumed a 6% CHO (n=8) solution, a 6-g EAA (n=8) mixture, a combined CHO+EAA (n=8) supplement, or placebo (PLA; n=8) beverage. Resistance exercise performed in conjunction with CHO and CHO+EAA ingestion resulted in significantly elevated (P<.001) glucose and insulin concentrations above baseline, whereas EAA ingestion only increased the postexercise insulin response (P<.05). Time matched at 60 minutes, the PLA group exhibited a peak cortisol increase of 105% (P<.001) with no significant change in glucose or insulin concentrations. Conversely, the CHO and CHO+EAA groups displayed a decrease in cortisol levels of 11% and 7%, respectively. Coinciding with these hormonal response patterns were significant differences in myofibrillar protein degradation. Ingestion of the EAA and CHO treatments attenuated 3-MH excretion 48 hours after the exercise bout. Moreover, this response was synergistically potentiated when the 2 treatments were combined, with CHO+EAA ingestion resulting in a 27% reduction (P<.01) in 3-MH excretion. In contrast, the PLA group displayed a 56% increase (P<.01) in 3-MH excretion. These data demonstrate that not only does CHO and EAA ingestion during the exercise bout suppress exercise-induced cortisol release; the stimulatory effect of resistance exercise on myofibrillar protein degradation can be attenuated, most dramatically when the treatments are combined (CHO+EAA). Through an "anticatabolic effect," this altered balance may better favor the conservation of myofibrillar protein.     

Androgen therapy induces muscle protein anabolism in older women

CONTEXT: Normal healthy men and women undergo a gradual loss of skeletal muscle mass and strength with advancing age. While androgens are protein anabolic in older men, the metabolic effects in older women are poorly understood. OBJECTIVE AND DESIGN: The objective of this study was to determine whether oral administration of a synthetic derivative of testosterone [oxandrolone, Oxandrin (OX)] (7.5 mg orally twice daily for 14 d) to five older women (age, 65 +/- 2 yr) would enhance skeletal muscle anabolic biomarkers including mixed muscle fractional synthetic rate (FSR), net phenylalanine balance, androgen receptor, and IGF-I protein expression at d 0, 5, and 14 of treatment. As a positive control, seven older men were examined after 14 d of OX (10 mg orally twice daily). SETTING: The study was performed at the General Clinical Research Center. RESULTS: Fourteen days of OX significantly increased skeletal muscle FSR in older women (d 0, 0.073 +/- 0.006 vs. d 5, 0.092 +/- 0.006 vs. d 14, 0.115 +/- 0.007%/h) (P < 0.05, d 0 vs. d 14). Conversely, OX stimulated FSR in older men after only 5 d (d 0, 0.061 +/- 0.003 vs. d 5, 0.101 +/- 0.01 vs. d 14, 0.084 +/- 0.01%/h) (P < 0.05, d 0 vs. d 5). Androgen receptor expression was significantly increased in older men by d 14, but had not increased in older women. No change was noted in IGF-I expression in either group. We conclude that the skeletal muscle of older women and men responds to androgen administration, although the time course of anabolism appears to be gender specific.     

Effectiveness of essential amino acid supplementation in stimulating whole body net protein anabolism is comparable between COPD patients and healthy older adults

BackgroundThe development of effective nutritional strategies in support of muscle growth for patients with chronic obstructive pulmonary disease (COPD) remains challenging. Dietary essential amino acids (EAAs) are the main driver of postprandial net protein anabolism. In agreement, EAA supplements in healthy older adults are more effective than supplements with the composition of complete proteins. In patients with COPD it is still unknown whether complete protein supplements can be substituted with only EAAs, and whether they are as effective as in healthy older adults.MethodsAccording to a double-blind randomized crossover design, we examined in 23 patients with moderate to very severe COPD (age: 65 ± 2 years, FEV₁: 40 ± 2% of predicted) and 19 healthy age-matched subjects (age: 64 ± 2 years), whether a free EAA mixture with a high proportion (40%) of leucine (EAA mixture) stimulated whole body net protein gain more than a similar mixture of balanced free EAAs and non-EAAs as present in whey protein (TAA mixture). Whole body net protein gain and splanchnic extraction of phenylalanine (PHE) were assessed by continuous IV infusion of L-[ring-²H₅]-PHE and L-[ring-²H₂]-tyrosine, and enteral intake of L-[¹⁵N]-PHE (added to the mixtures).ResultsBesides an excellent positive linear relationship between PHE intake and net protein gain in both groups (r = 0.84–0.91, P < 0.001), net protein gain was 42% higher in healthy controls and 49% higher in COPD patients after intake of the EAA mixture compared to the TAA mixture (P < 0.0001). These findings could not be attributed to the high LEU content, as in both groups net protein gain per gram EAA intake was lower for the EAA mixture (P < 0.0001). Net protein gain was higher in COPD patients for both mixtures due to a 40% lower splanchnic extraction (P < 0.0001), but was similarly related to dietary PHE (i.e. EAA) plasma appearance.ConclusionsIn COPD patients, similarly to healthy older adults, free EAA supplements stimulate whole body protein anabolism more than free amino acid supplements with the composition of complete proteins. Therefore, free EAA supplements may aid in the prevention and treatment of muscle wasting in this patient population.     

Essential amino acid and carbohydrate supplementation ameliorates muscle protein loss in humans during 28 days bedrest

We determined whether essential amino acid and carbohydrate supplementation could offset the catabolic response to prolonged inactivity. Major outcome measures included mixed muscle fractional synthetic rate (FSR), phenylalanine net balance, lean leg mass, and leg extension strength. On d 1 and 28, vastus lateralis muscle biopsies and femoral arterio-venous blood samples were obtained during a primed constant infusion of l-[ring-(2)H(5)]phenylalanine. Net balance and FSR were calculated over 16 h, during which the control group (CON) received a nutritionally mixed meal every 5 h (0830, 1330, and 1830 h). The experimental group (EXP) also consumed 16.5 g essential amino acids and 30 g carbohydrate (1100, 1600, and 2100 h). The dietary regimen was maintained during bedrest. FSR was higher in the EXP group on d 1 (EXP, 0.099 +/- 0.008%/h; CON: 0.075 +/- 0.005%/h) and d 28 (EXP, 0.093 +/- 0.006%/h; CON, 0.055 +/- 0.007%/h). Lean leg mass was maintained throughout bedrest in the EXP group (+0.2 +/- 0.3 kg), but fell in the CON group (-0.4 +/- 0.1 kg). Strength loss was more pronounced in the CON group (EXP, -8.8 +/- 1.4 kg; CON, -17.8 +/- 4.4 kg). Essential amino acid and carbohydrate supplementation may represent a viable intervention for individuals at risk of sarcopenia due to immobility or prolonged bedrest.     

The reliability of using the single-biopsy approach to assess basal muscle protein synthesis rates in vivo in humans

It has recently been proposed that basal muscle protein synthesis can be effectively assessed by measuring the background enrichment in total plasma protein, thereby omitting the initial biopsy, and determining the difference in enrichment from a single muscle biopsy obtained during a primed continuous infusion of isotope-labeled amino acids. We determined the reliability of calculating basal mixed muscle protein fractional synthetic rates (FSRs) from mixed plasma proteins and a single muscle biopsy compared against the sequential muscle biopsy approach. Ten men (age, 23 ± 1 years; body mass index, 22 ± 1 kg?m^?2) received muscle biopsies of the vastus lateralis after 2 and 4 hours of a primed continuous infusion of l-[ring-¹³C₆]phenylalanine. Mixed muscle protein FSR was calculated from baseline plasma enrichments and muscle protein enrichments determined from the biopsy at 2 hours (1BX SHORT) or 4 hours (1BX LONG), or between muscle protein enrichments at 2 and 4 hours (2BX) of the infusion. No differences (P = .50) were observed in mixed muscle protein FSR, using plasma [ring-¹³C₆]phenylalanine enrichments as the precursor, between the 1BX SHORT (0.031% ± 0.010%?h^?1), 1BX LONG (0.032% ± 0.007%?h^?1), or 2BX (0.035% ± 0.011%?h^?1) approach. A significant correlation was observed between the calculated muscle protein FSR assessed using the 1BX LONG and 2BX approach (r = 0.7, P = .02). Our data demonstrate that the single-biopsy approach, irrespective of whether the biopsy is obtained at 2 or 4 hours, can be used as a surrogate for the sequential-biopsy approach to determine basal muscle protein synthesis in a group.     

The synthesis rates of total liver protein and plasma albumin determined simultaneously in vivo in humans

Although the metabolism of liver-derived plasma proteins such as albumin has been extensively studied, human hepatic protein synthesis as a whole has not been well characterized, because a reproducible model for obtaining human liver tissue has not been available. In this study, the fractional synthesis rates of total liver protein and albumin in vivo were determined simultaneously in nine subjects undergoing elective laparoscopic cholecystectomy. L-[²H₅]phenylalanine (45 mg/kg body wt) was administered for 10 minutes intravenously. Blood samples were collected at regular intervals for 90 minutes and a liver biopsy specimen was taken at 35 +/- 7 minutes. The enrichments of plasma free phenylalanine, plasma albumin, and total liver protein were measured with gas chromatography mass spectrometry (GC-MS). The fractional synthesis rate (FSR) of total liver protein was 24.7 +/- 3.1 %/d (mean +/- SD), and that of albumin was 5.9 +/-1.2%/d. The amount of albumin synthesized per day (absolute synthesis rate, ASR) was 109 +/- 21 mg/kg body wt. No correlation between FSR of total liver protein and ASR of albumin was found. It is concluded that the technique of obtaining liver tissue specimens during laparoscopic surgery may serve as a human in vivo model to study total liver protein synthesis. The fractional synthesis rate of total liver proteins (stationary and exported), equals approximately 25% of the liver protein content daily. Within the range of values of this study, the absolute synthesis rate of albumin was not correlated to the fractional synthesis rate of total liver protein.(Hepatology 1997 Jan;25(1):154-8)     

Amino acids stimulate translation initiation and protein synthesis through an Akt-independent pathway in human skeletal muscle

Studies in vitro as well as in vivo in rodents have suggested that amino acids (AA) not only serve as substrates for protein synthesis, but also as nutrient signals to enhance mRNA translation and protein synthesis in skeletal muscle. However, the physiological relevance of these findings to normal humans is uncertain. To examine whether AA regulate the protein synthetic apparatus in human skeletal muscle, we infused an AA mixture (10% Travesol) systemically into 10 young healthy male volunteers for 6 h. Forearm muscle protein synthesis and degradation (phenylalanine tracer method) and the phosphorylation of protein kinase B (or Akt), eukaryotic initiation factor 4E-binding protein 1, and ribosomal protein S6 kinase (p70(S6K)) in vastus lateralis muscle were measured before and after AA infusion. We also examined whether AA affect urinary nitrogen excretion and whole body protein turnover. Postabsorptively all subjects had negative forearm phenylalanine balances. AA infusion significantly improved the net phenylalanine balance at both 3 h (P < 0.002) and 6 h (P < 0.02). This improvement in phenylalanine balance was solely from increased protein synthesis (P = 0.02 at 3 h and P < 0.003 at 6 h), as protein degradation was not changed. AA also significantly decreased whole body phenylalanine flux (P < 0.004). AA did not activate Akt phosphorylation at Ser(473), but significantly increased the phosphorylation of both eukaryotic initiation factor 4E-binding protein 1 (P < 0.04) and p70(S6K) (P < 0.001). We conclude that AA act directly as nutrient signals to stimulate protein synthesis through Akt-independent activation of the protein synthetic apparatus in human skeletal muscle.     

Effect of dietary copper supplementation on cell composition and apoptosis in atherosclerotic lesions of cholesterol-fed rabbits

We have previously shown that dietary copper supplementation modulates the formation of atherosclerotic lesions in the cholesterol-fed rabbit. In the present study, we have investigated the effects of copper supplementation on the cellular composition and characteristics of atherosclerotic lesions in cholesterol-fed NZW rabbits. Rabbits received a 1% cholesterol diet with or without 0.02% copper acetate (containing 12 and 0.3 mg copper per 100 g diet, respectively) for 12 weeks. The tunica intima was significantly smaller in the animals receiving copper supplements (0.016+/-0.005 vs. 0.068+/-0.019 mm(2), P<0.05) and this was accompanied by a significant increase in aortic copper content (4.0+/-0.8 vs. 1.8+/-0.2 microg/g tissue, P<0.05). The percentage area staining for smooth muscle cells (HHF-35 positive) was significantly lower in the intima of animals receiving copper supplements (7.13+/-1.02 vs. 9.72+/-0.82%, P<0.05). However, there were no significant differences in area staining for macrophages (RAM-11 positive) between groups (22.6+/-7.9 vs. 23.3+/-4.9%). There were also significantly fewer apoptotic cells (0.96+/-0.33 vs. 2.54+/-0.56%, P<0.005) in the aortic intima from animals supplemented with copper, but no difference in the number of proliferating cells. However, there was a reduction in intimal collagen staining (Sirius red positivity) in the animals receiving a copper supplement. Taken together, these data show that dietary copper can significantly affect the composition and progression of atherosclerotic lesions.     

The response of muscle protein anabolism to combined hyperaminoacidemia and glucose-induced hyperinsulinemia is impaired in the elderly

Muscle mass declines with aging. Amino acids alone stimulate muscle protein synthesis in the elderly. However, mixed nutritional supplementation failed to improve muscle mass. We hypothesized that the failure of nutritional supplements is due to altered responsiveness of muscle protein anabolism to increased amino acid availability associated with endogenous hyperinsulinemia. We measured muscle protein synthesis and breakdown, and amino acid transport in healthy young (30 +/- 3 yr) and elderly (72 +/- 1 yr) volunteers in the basal postabsorptive state and during the administration of an amino acid-glucose mixture, using L-[ring-(2)H(5)]phenylalanine infusion, femoral artery and vein catheterization, and muscle biopsies. Basal muscle amino acid turnover was similar in young and elderly subjects. The mixture increased phenylalanine leg delivery and transport into the muscle in both groups. Phenylalanine net balance increased in both groups (young, -27 +/- 8 to 64 +/- 17; elderly, -16 +/- 4 to 29 +/- 7 nmol/(min.100 mL); P: < 0.0001, basal vs. mixture), but the increase was significantly blunted in the elderly (P: = 0.030 vs. young). Muscle protein synthesis increased in the young, but remained unchanged in the elderly [young, 61 +/- 17 to 133 +/- 30 (P: = 0. 005); elderly, 62 +/- 9 to 70 +/- 14 nmol/(min.100 mL) (P: = NS)]. In both groups, protein breakdown decreased (P: = 0.012) and leg glucose uptake increased (P: = 0.0258) with the mixture. We conclude that the response of muscle protein anabolism to hyperaminoacidemia with endogenous hyperinsulinemia is impaired in healthy elderly due to the unresponsiveness of protein synthesis.     

Androstenedione does not stimulate muscle protein anabolism in young healthy men

Androstenedione is the immediate precursor of testosterone. Androstenedione intake has been speculated to increase plasma testosterone levels and muscle anabolism. Thus, androstenedione supplements have become widely popular in the sport community to improve performance. This study was designed to determine whether 5 days of oral androstenedione (100 mg/day) supplementation increases skeletal muscle anabolism. Six healthy young men were studied before the treatment period and after 5 days of oral androstenedione supplementation. Muscle protein turnover parameters were compared to those of a control group studied twice as well and receiving no treatment. We measured muscle protein kinetics using a three-compartment model involving infusion of L-[ring-2H5]phenylalanine, blood sampling from femoral artery and vein, and muscle biopsies. Plasma testosterone, androstenedione, LH, and estradiol concentrations were determined by RIA. After ingestion of oral androstenedione, plasma testosterone and LH concentrations did not change from basal, whereas plasma androstenedione and estradiol concentrations were significantly increased (P<0.05). Compared to a control group, androstenedione did not affect muscle protein synthesis and breakdown, or phenylalanine net balance across the leg. We conclude that oral androstenedione does not increase plasma testosterone concentrations and has no anabolic effect on muscle protein metabolism in young eugonadal men.     

Appetite hormones and energy intake in obese men after consumption of fructose, glucose and whey protein beverages

OBJECTIVE: To investigate appetite responses over 4 h to fructose beverages in obese men, relative to glucose and whey protein. Second, to investigate the effect of combining whey and fructose on postprandial appetite hormones. DESIGN: Randomized, double-blind crossover study of four beverages (1.1 MJ) containing 50 g of whey, fructose, glucose or 25 g whey+25 g fructose. Blood samples and appetite ratings were collected for 4 h then a buffet meal was offered. SUBJECTS: Twenty-eight obese men (age: 57.0+/-1.6 years, body mass index: 32.5+/-0.6 kg/m(2)). MEASUREMENTS: Plasma ghrelin (total), glucagon-like peptide-1 (GLP-1 7-36), cholecystokinin-8, glucose, insulin and appetite ratings were assessed at baseline and 30, 45, 60, 90, 120, 180, 240 min after beverages, followed by measurement of ad libitum energy intake. RESULTS: Fructose produced lower glycaemia and insulinaemia compared to the glucose treatment (P<0.0001); whereas postprandial ghrelin, GLP-1 and cholecystokinin responses were similar after both treatments. Whey protein produced a prolonged (2-4 h) suppression of ghrelin (P=0.001) and elevation of GLP-1 (P=0.002) and cholecystokinin (P=0.003) that were reduced when combined with fructose, while glucose and insulin responses were similar. Energy intake after 4 h was independent of beverage type (glucose 4.7+/-0.2 MJ; fructose 4.9+/-0.3 MJ; whey 4.6+/-0.3 MJ; whey/fructose 4.8+/-0.3 MJ; P>0.05). CONCLUSION: In obese men, fructose- and glucose-based beverages had similar effects on appetite and associated regulatory hormones, independent of the differing glycaemic and insulinaemic responses. The contrasting profile of plasma ghrelin, GLP-1 and cholecystokinin after whey protein consumption did not impact on ad libitum intake 4 h later and was attenuated when 50% of whey was replaced with fructose.     

Measurement of protein fractional synthesis and breakdown rates in the skin of rabbits using a subflooding dose method

The flooding dose method continues to be useful in measuring protein fractional synthetic rate (FSR) in a tissue. However, flooding of free amino acid pools eliminates enrichment difference between plasma and tissue free amino acid pools, which makes it impossible to concomitantly measure protein fractional breakdown rate (FBR). We hypothesized that a subflooding dose of an amino acid reduces the enrichment difference between plasma and tissue free amino acid pool to a minimal measurable level, thus allowing concomitant measurement of protein FSR and FBR. Phenylalanine (40% enriched) at 50 mg/kg was intravenously injected as a bolus in 6 anesthetized rabbits. Arterial blood and chest skin samples were taken before the injection and for 120 minutes after the injection. Fractional breakdown rate of skin protein calculated from 15-60-120–minute sampling times was 11.3%/d ± 2.0%/d, which was close (P = .66) to the corresponding FSR of 10.0%/d ± 2.3%/d. The subflooding dose injection did not disturb the FBR approach because modifications on the FBR equation to account for the changes of plasma phenylalanine concentration resulted in the same value (11.5%/d ± 1.4%/d). The FBR was positively correlated with the FSR (r = 0.80, P < .05). These findings indicate maintenance of protein mass in the skin, which is a metabolic characteristic of the skin. This subflooding dose method provides a methodological choice to concomitantly measure both FSR and FBR in a tissue.     

The muscle protein synthetic response to the combined ingestion of protein and carbohydrate is not impaired in healthy older men

Aging is associated with a progressive decline in skeletal muscle mass. It has been hypothesized that an attenuated muscle protein synthetic response to the main anabolic stimuli may contribute to the age-related loss of muscle tissue. The aim of the present study was to compare the muscle protein synthetic response following ingestion of a meal-like amount of dietary protein plus carbohydrate between healthy young and older men. Twelve young (21 ± 1 years) and 12 older (75 ± 1 years) men consumed 20 g of intrinsically l-[1-¹³C]phenylalanine-labeled protein with 40 g of carbohydrate. Ingestion of specifically produced intrinsically l-[1-¹³C]phenylalanine-labeled protein allowed us to assess the subsequent incorporation of casein-derived amino acids into muscle protein. Blood samples were collected at regular intervals, with muscle biopsies obtained prior to and 2 and 6 h after protein plus carbohydrate ingestion. The acute post-prandial rise in plasma glucose and insulin concentrations was significantly greater in the older compared with the younger males. Plasma amino acid concentrations increased rapidly following drink ingestion in both groups. However, plasma leucine concentrations were significantly lower at t = 90 min in the older when compared with the young group (P < 0.05). Muscle protein-bound l-[1-¹³C]phenylalanine enrichments increased to 0.0071 ± 0.0016 and 0.0072 ± 0.0013 mole percent excess (MPE) at 2 h and 0.0229 ± 0.0016 and 0.0213 ± 0.0024 MPE at 6 h following ingestion of the intrinsically labeled protein in the young and older males, respectively, with no differences between groups (P > 0.05). We conclude that the use of dietary protein-derived amino acids for muscle protein synthesis is not impaired in healthy older men following intake of protein plus carbohydrate.     

Adequate energy-protein intake is not enough to improve nutritional and metabolic status in muscle-depleted patients with chronic heart failure

BACKGROUND: An adequate energy-protein intake (EPI) when combined with amino acid supplementation may have a positive impact on nutritional and metabolic status in patients with chronic heart failure (CHF). METHODS AND RESULTS: Thirty eight stable CHF patients (27 males, 73.5+/-4 years; BMI 22.5+/-1.4 kg/m2), with severe depletion of muscle mass and were randomised to oral supplements of essential amino acids 8 g/day (EAA group; n=21) or no supplements (controls; n=17). All patients had adequate EPI (energy> or =30 kcal/kg; proteins >1.1 g/kg). At baseline and 2-months after randomisation, the patients underwent metabolic (plasma lactate, pyruvate concentration; serum insulin level; estimate of insulin resistance by HOMA index), nutritional (measure of nitrogen balance), and functional (exercise test, walking test) evaluations. Body weight increased by >1 kg in 80% of supplemented patients (mean 2.96 kg) and in 30% of controls (mean 2.3 kg) (interaction <0.05). Changes in arm muscle area, nitrogen balance, and HOMA index were similar between the two treatment groups. Plasma lactate and pyruvate levels increased in controls (p<0.01 for both) but decreased in the supplemented group (p<0.01 and 0.02 respectively). EAA supplemented patients but not controls improved both exercise output and peak oxygen consumption and walking test. CONCLUSIONS: Adequate EPI when combined with essential amino acid supplementation may improve nutritional and metabolic status in most muscle-depleted CHF patients.     

Effects of whey protein nutritional supplement on muscle function among community-dwelling frail older people: A multicenter study in China

BackgroundFrailty, featured by the presence of fatigue, weight loss, decrease in grip strength, decline gait speed and reduced activities substantially increase the risk of falls, disability, hospitalizations, and mortality of older people. Nutritional supplementation and resistance exercise may improve muscle function and reverse frailty status.ObjectiveTo evaluate whether whey protein supplements can improve muscle function of frail older people in addition to resistance exercise.Methods115 community-dwelling older adults who met the Fried's criteria for frailty from four hospitals’ out-patients clinic in Beijing, China completed the study. It's a case–control study which whey protein was used as daily supplementation for 12 weeks for active group and regular resistance exercise for active group and control group. Handgrip strength, gait speed, chair-stand test, balance score, and SPPB score were compared in both groups during the 12-week follow-up.ResultsOverall, 115 subjects were enrolled for study with 66 in active group and 49 in control group. Handgrip strength, gait speed, and chair-stand time were all significantly improved in both groups with significant between-group differences. The active group improved significantly in handgrip strength compared with the control group, which between-group effect (95% confidence interval) for female was 0.107 kg (0.066–0.149), p = 0.008 and for male was 0.89 kg (0.579–1.201), p = 0.007. For chair-stand time, between-group effect (95% confidence interval) was −2.875 s (−3.62 to −2.124), p = 0.004 and for gait speed, between-group effect (95% confidence interval) was 0.109 m/s (0.090 to 0.130), p = 0.003.ConclusionsThe 12-week intervention of whey protein oral nutritional supplement revealed significant improvements in muscle function among the frailty elderly besides aiding with resistance exercise. These results warrant further investigations into the role of a multi-modal supplementation approach which could prevent adverse outcomes among frailty elderly at risk for various disabilities.     

Overexpression of a constitutively active protein kinase G mutant reduces neointima formation and in-stent restenosis

BACKGROUND: Neointima formation after arterial injury is associated with reduced vascular cyclic guanosine monophosphate (cGMP) and cGMP-dependent protein kinase (PKG), a major cGMP effector in vascular smooth muscle. We tested the effect of PKG overexpression on the neointimal response to vascular injury. Methods and Results- Infection of cultured rat aortic smooth muscle cells (RASMCs) with an adenoviral vector specifying a cGMP-independent, constitutively active PKG mutant (AdPKGcat) reduced serum-induced migration by 33% and increased serum-deprivation-induced apoptosis 2-fold (P<0.05 for both). Infection with wild-type PKG (AdPKG), in the absence of cGMP, did not affect migration or apoptosis. Two weeks after balloon-injured rat carotid arteries were infected with 1x 10(10) pfu AdPKGcat (n=12), AdPKG (n=8), or a control adenovirus (n=8), intima-to-media ratio was less in AdPKGcat-infected arteries than in AdPKG- or control adenovirus-infected vessels (0.26+/-0.06 versus 0.61+/-0.12 and 0.70+/-0.12, respectively, P<0.05 for both). Two weeks after intramural administration of 1.75x10(10) pfu AdPKGcat (n=8) or a control adenovirus (n=8) into porcine coronary arteries with in-stent restenosis, luminal diameter was greater in AdPKGcat-infected arteries than in control adenovirus-infected vessels (2.32+/-0.16 versus 1.81+/-0.13 mm, P=0.028), associated with reduced neointimal area (3.30+/-0.24 versus 4.15+/-0.13 mm(2), P=0.008), neointima-to-vessel area ratio (0.42+/-0.05 versus 0.58+/-0.04, P<0.05), and percent stenosis (45+/-6% versus 70+/-4%, P<0.05). CONCLUSIONS: Expression of a constitutively active PKG reduces neointima formation after balloon injury in rats and reduces coronary in-stent restenosis in pigs. PKGcat gene transfer may be a promising strategy for vasculoproliferative disorders.     

Abnormalities of whole body protein turnover, muscle metabolism and levels of metabolic hormones in patients with chronic heart failure

OBJECTIVE: It is well known that chronic heart failure (CHF) is associated with insulin resistance and cachexia, but little is known about the underlying substrate metabolism. The present study was undertaken to identify disturbances of basal glucose, lipid and protein metabolism. DESIGN: We studied eight nondiabetic patients with CHF (ejection fraction 30 +/- 4%) and eight healthy controls. Protein metabolism (whole body and regional muscle fluxes) and total glucose turnover were isotopically assayed. Substrate oxidation were obtained by indirect calorimetry. The metabolic response to exercise was studied by bicycle ergometry exercise. RESULTS: Our data confirm that CHF patients have a decreased lean body mass. CHF patients are characterised by (i) decreased glucose oxidation [glucose oxidation (mg kg(-1) min(-1)): 1.25 +/- 0.09 (patients) vs. 1.55 +/- 0.09 (controls), P < 0.01] and muscle glucose uptake [a - v diff(glucose) (micromol L(-1)): -10 +/- 25 (patients) vs. 70 +/- 22 (controls), P < 0.01], (ii) elevated levels of free fatty acids (FFA) [FFA (mmol L(-1)): 0.72 +/- 0.05 (patients) vs. 0.48 +/- 0.03 (controls), P < 0.01] and 3-hydroxybutyrate and signs of elevated fat oxidation and muscle fat utilization [a - v diff(FFA) (mmol L(-1)): 0.12 +/- 0.02 (patients) vs. 0.05 +/- 0.01 (controls), P < 0.05] and (iii) elevated protein turnover and protein breakdown [phenylalanine flux (micromol kg(-1) h(-1)): 36.4 +/- 1.5 (patients) vs. 29.6 +/- 1.3 (controls), P < 0.01]. Patients had high circulating levels of noradrenaline, glucagon, and adiponectin, and low levels of ghrelin. We failed to observe any differences in metabolic responses between controls and patients during short-term exercise. CONCLUSIONS: In the basal fasting state patients with CHF are characterized by several metabolic abnormalities which may contribute to CHF pathophysiology and may provide a basis for targeted intervention.     

Milk whey protein decreases oxygen free radical production in a murine model of chronic iron-overload cardiomyopathy

BACKGROUND: Chronic iron overload is a major cause of organ failure worldwide, but its pathogenesis remains to be elucidated. OBJECTIVES: To examine in an experimental murine model of iron-overload cardiomyopathy the relation between milk whey protein and, first, the production of reactive oxygen free radical species and, second, antioxidant reserve status. METHODS: B6D2F1 mice were randomly assigned to four treatment groups (n=8 per treatment group): placebo control; iron only; whey only; and iron with whey. Reactive oxygen free radical species in the heart were quantified by the cytotoxic aldehydes malondialdehyde (MDA), 4-hydroxy-nonenal (HNE) and hexanal, while antioxidant reserve status was quantified by glutathione (GSH) and glutathione peroxidase (GPx) activity in the heart tissue. RESULTS: Significantly decreased concentrations (pmol/100 mg wet weight tissue) of MDA (2468+/-261), HNE (912+/-38) and hexanal (5385+/-927) were observed in the heart tissue of the group receiving iron with whey, in comparison with the iron-only treatment group (MDA 9307+/-387, HNE 1416+/-157, hexanal 14,874+/-2955; P<0.001). Significantly increased GPx (141+/-38 IU/L) and GSH (521+/-136 IU/L) activity were observed in mice receiving iron with whey, in comparison with mice receiving iron only (GPx 100+/-10 IU/L, GSH 446+/-33 IU/L; P<0.001). CONCLUSION: Mice receiving iron treatments with whey supplementation had significantly lower concentrations of cytotoxic aldehydes and significantly higher cardiac levels of GPx and GSH activity than did iron-only treated mice. Additional basic research is warranted to examine the exact mechanisms by which milk whey protein protects the heart.