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OBJECTIVE: The optimal protein intake for elderly individuals who exercise regularly has not yet been clearly defined. The aim of this study was to test the hypothesis that protein intake level is associated with muscle strength in elderly elite athletes. METHODS: We evaluated 50 elite senior athletes (38 men and 12 women) participating in the European Master Games 2011 in an observational cross-sectional study. Participants were divided into two groups-lower (LPI) or higher (HPI) protein intake-according to the median value of their ratio of urinary urea nitrogen to urinary creatinine (i.e., 8.8 g/L), as a marker of protein intake. A dietary interview confirmed differences in protein consumption between the LPI and HPI groups. We also evaluated body composition (bioimpedance), muscle strength, and hematochemical indices. RESULTS: LPI and HPI groups were homogeneous for age (72 [68-74] and 71 [68-74] y, respectively), fat-free mass index (18.4 [17-19.4] and 18.2 [17-19.1] kg/m2), body fat (18.3% [12.3-20.7%] and 16.6% [13.6-21.2%]), and glomerular filtration rate (57.7 [53.8-64.9] and 62.7 [56.1-69.3] mL/min/1.73 m2). The HPI group showed greater leg and trunk muscle strength (N) compared with the LPI group (left leg extension, 339 [238-369] versus 454 [273-561], respectively, P < 0.05; right leg extension, 319 [249-417] versus 432 [334-635], P ≤ 0.05; trunk extension, 435 [370-467] versus 464 [390-568], P ≤ 0.05). CONCLUSIONS: Higher protein intake in elite senior athletes is associated with a greater muscle strength.

We investigated the ability of pentoxifylline, a drug with hemorheological actions known to block tumor necrosis factor-alpha (TNF-alpha) release, to modulate whole-body protein kinetics in undialyzed patients with chronic uremia.Leucine rate of appearance (Ra) from proteolysis and leucine oxidation, a marker of net protein loss, were determined by infusing l-[1-13C]leucine and using the reciprocal pool model for calculations.Intravenous infusion of pentoxifylline in the postabsorptive state (1 mg/kg within 3 hours) decreased the intracellular leucine Ra from proteolysis by -16% +/- 4% versus -3% +/- 2% of saline (P = 0.02) and leucine oxidation by -16% +/- 4% versus +4% +/- 2% of saline (P = 0.003). Combined infusions of pentoxifylline and a balanced amino acid mixture (0.2 mg/kg/min) decreased whole-body proteolysis by -53% +/- 7% versus -26% +/- 6% of amino acid infusion alone (P = 0.02). Circulating levels of TNF-alpha and TNF-alpha soluble receptors (sTNF-Rs) were elevated (P0.001) in patients compared with healthy controls. Pentoxifylline infusion did not significantly affect TNF-alpha levels, but decreased sTNF-Rs both in the postabsorptive state and during hyperaminoacidemia.Pentoxifylline acutely decreased whole-body proteolysis in chronically uremic patients. Potential explanations for these pharmacological effects may include downregulation of the TNF-alpha system or other mechanisms related to the rheological action of the drug (eg, increased amino acid or insulin delivery to target cells).

Background & aims: The lysosomal cathepsin system contributes to degrading cellular skeletal muscle proteins in many catabolic diseases. We have assessed the relationships between cathepsin B mRNA levels and the enzyme activity for this protease in the skeletal muscle of acutely ill patients with severe trauma (n=7) and in patients with a variety of chronic disease states (hemodialysis, n=3; nervous anorexia, n=1; type 2 diabetes, n=2; prolonged immobilization, n=1). Methods: Muscle biopsies were taken from the vastus lateralis muscle in patients and controls to assess tissue levels of cathepsin B mRNA by competitive–quantitative polymerase chain reaction, cathepsin B proteolytic activity and myofibrillar protein content as alkali-soluble protein to DNA ratio (ASP/DNA). In the trauma patients, muscle protein loss was assessed by the arteriovenous balance technique as rate of phenylalanine release from leg muscle. Results: The acute trauma patients exhibited a significant net phenylalanine release from leg muscle (33±4 nmol phenylalanine/min/100 ml leg volume) despite a continuous nutritional support. The muscle ASP/DNA ratio was lower (P

Carnitine is a conditionally essential metabolite that plays a critical role in cell physiology by participating in transesterification reactions and preventing organic acid accumulation. A number of disease states are characterized by carnitine depletion that may lead to metabolic and clinical disturbances. In maintenance hemodialysis, carnitine is lost through dialytic membranes, leading in selected patients to carnitine depletion with a relative increase of the esterified forms. Carnitine supplementation after or during dialysis counteracts such alterations and may be associated with some clinical benefits. Recent meta-analyses of the literature indicate that carnitine supplementation in hemodialysis patients may improve the hematological status (allowing a reduction of the requirement for erythropoietin), the exercise tolerance, the plasma lipid profile, and the intradialytic symptoms. In addition, carnitine supplementation may improve cardiac functions, protein metabolism, and insulin resistance. Carnitine supplementation has been recently approved by the US Food and Drug Administration not only for the treatment, but also for the prevention of carnitine depletion in dialysis patients. Furthermore, clinical guidelines developed by both American and European nephrological societies suggest that a trial with carnitine supplementation could be recommended in selected dialysis patients who do not adequately respond to standard therapy for certain conditions, such as severe and persistent muscle cramps or hypotension during dialysis, lack of energy affecting quality of life, skeletal muscle weakness or myopathy, cardiomyopathy, and anemia of uremia unresponsive to or requiring large doses of erythropoietin.

The metabolic response to trauma and sepsis involves an increased loss of body proteins. Specific sites of changes of protein and amino acid metabolism have been identified. In skeletal muscle, the rate of proteolysis is accelerated greatly. The rate of protein synthesis also may be increased but not enough to match the increase in degradation. Intramuscular glutamine concentration is decreased because of increased efflux and possibly decreased de novo synthesis. In the liver, the rate of synthesis of selected proteins (i.e., albumin, transferrin, prealbumin, retinol-binding protein, and fibronectin) is decreased, whereas acute phase protein synthesis is accelerated. Tissues characterized by rapidly replicating cells, such as enterocytes, immune cells, granulation tissue, and keratinocytes, exhibit early alterations in the case of decreased protein synthesis capacity. In these tissues, glutamine use is accelerated. Increased stress hormone (cortisol and glucagon) and cytokine secretion, as well as intracellular glutamine depletion, are potential mediators of altered protein metabolism in trauma and sepsis. However, the relative importance of these factors has not been clarified. Therapy of acute protein catabolism may include the use of biosynthetic human growth hormone, possibly in combination with insulin-like growth factor-1, and the administration of metabolites at pharmacologic doses. We recently studied the effects of carnitine and alanyl-glutamine administration in severely traumatized patients. We found that both carnitine and the glutamine dipeptide restrained whole-body nitrogen loss without affecting selected indices of protein metabolism in the skeletal muscle.