Whey vs Casein to Combat Post-inflammatory Protein and Muscle Waste in Acute Disease

Muscle Protein Synthesis, Endotoxemia, Nutrition, Milk Protein, Metabolism, Whey, Casein

milk protein, endotoxemia, muscle protein synthesis, whey, casein

This study compares three different protein supplements (casein, whey and leucine-enriched whey) and their effect on post-inflammatory muscle waste in a model of acute disease. Each test person will undergo all three interventions. It is believed that leucine is the primary driver of muscle protein synthesis and therefore we hypothesize that leucine-enriched whey and whey are superior to casein in combating post-inflammatory muscle waste, because of its higher leucine content (16%, 11% and 9% leucine, respectively).

Background: Acute illness is accompanied by infection/inflammation, anorexia and immobilization all contributing to muscle loss, making nutritional supplement optimization an obvious target for investigation and eventually clinical intervention. In the clinical setting large heterogenicity among patients complicates investigations of muscle metabolism during acute illness. Therefore we introduce a disease model by combining Inflammation + 36 hour fast and bedrest. Inflammation/febrile illness will be initiated by using the well-established human endotoxemia model with a bolus injection of Escherichia coli lipopolysaccharide (LPS), known to cause inflammation comparable with the initial phase of sepsis. The amino acid leucine has shown to be particularly anabolic in performance sports, but little is known about its potential beneficial effects during acute illness. Leucine is a powerful activator of muscle protein synthesis and it seems that protein supplements with the highest leucine content elicit a greater increase in protein synthesis than those with a smaller fraction of leucine. The protein supplements used most in hospitals contain casein derived protein, which has a much lower leucine content than the whey protein compounds typically used in performance sports. This study compares three different protein supplements.The study is an open, randomized crossover trial. Laboratory technicians, test subjects and investigators will be blinded. Interventions: I. LPS (1 ng/kg as bolus) + 36 h fasting + 36 h bedrest + Casein (9% leucine) II. LPS (1 ng/kg as bolus) + 36 h fasting + 36 h bedrest + Whey (11% leucine) III. LPS (1 ng/kg as bolus) + 36 h fasting + 36 h bedrest + Leucine-enriched whey (16% leucine) The test objects will be given 0,6 g protein/kg, 1/3 as a bolus and 2/3 as sipping over a period of 3,5 hour. Muscle metabolism will be investigated by phenylalanine tracer using the forearm model and total protein metabolism using a carbamide tracer. Through muscle biopsies intracellular signalling pathways will be investigated.

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