Timing of amino acid-carbohydrate ingestion alters anabolic response of muscle to resistance exercise.

The present study was designed to determine whether consumption of an oral essential amino acid-carbohydrate supplement (EAC) before exercise results in a greater anabolic response than supplementation after resistance exercise. Six healthy human subjects participated in two trials in random order, PRE (EAC consumed immediately before exercise), and POST (EAC consumed immediately after exercise). A primed, continuous infusion of L-[ring-(2)H(5)]phenylalanine, femoral arteriovenous catheterization, and muscle biopsies from the vastus lateralis were used to determine phenylalanine concentrations, enrichments, and net uptake across the leg. Blood and muscle phenylalanine concentrations were increased by approximately 130% after drink consumption in both trials. Amino acid delivery to the leg was increased during exercise and remained elevated for the 2 h after exercise in both trials. Delivery of amino acids (amino acid concentration times blood flow) was significantly greater in PRE than in POST during the exercise bout and in the 1st h after exercise (P < 0.05). Total net phenylalanine uptake across the leg was greater (P = 0.0002) during PRE (209 +/- 42 mg) than during POST (81 +/- 19). Phenylalanine disappearance rate, an indicator of muscle protein synthesis from blood amino acids, increased after EAC consumption in both trials. These results indicate that the response of net muscle protein synthesis to consumption of an EAC solution immediately before resistance exercise is greater than that when the solution is consumed after exercise, primarily because of an increase in muscle protein synthesis as a result of increased delivery of amino acids to the leg.

Molecular mechanisms contributing to necrotizing enterocolitis.

OBJECTIVE: To examine the cellular mechanisms involved in the pathogenesis of necrotizing enterocolitis (NEC). SUMMARY BACKGROUND DATA: Necrotizing enterocolitis is a major cause of death and complications in neonates; the cellular mechanisms responsible for NEC are unknown. The inducible form of cyclooxygenase (i.e., COX-2) is activated by the transcription factor nuclear factor (NF)-kappaB and is thought to play a role in inflammation. METHODS: Segments of perforated and adjacent uninvolved small intestine from neonates with NEC were analyzed for COX-2 expression by immunohistochemistry. NEC was induced in weanling (18 days old) rats by occlusion of superior mesenteric vessels for 1 hour and intraluminal injection of platelet activating factor (50 micro/kg). Small intestine was harvested for protein extraction. Western immunoblot was performed to determine expression of COX-2. Gel shift assays were performed to assess NF-kappaB binding activity. RESULTS: Immunohistochemical analysis showed increased COX-2 protein expression in the perforated intestinal sections of all 36 neonates but not in adjacent normal intestine. Increased expression of COX-2 protein and NF-kappaB binding activity was noted in the small intestine of weanling rats at 0 and 3 hours after induction of NEC. CONCLUSIONS: Increased COX-2 expression was identified in all neonatal intestinal segments resected for perforated NEC. In addition, a coordinate induction of COX-2 expression and NF-kappaB binding was noted in a rodent model of NEC. These findings suggest that the COX-2/NF-kappaB pathway may play a role in the pathogenesis of NEC. Therapeutic agents that target this pathway may prove useful in the treatment or possible prevention of NEC.