Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/8/2006
Publication Date: 2/1/2007
Publication URL: http://jn.nutrition.org/cgi/reprint/137/2/315
Citation: Frank, J.W., Escobar, J., Nguyen, H.V., Jobgen, S.C., Jobgen, W.S., Davis, T.A., Wu, G. 2007. Oral "N"-Carbamylglutamate supplementation increases protein synthesis in skeletal muscle of piglets. Journal of Nutrition. 137(2):315-319. Interpretive Summary: The amino acid arginine is low in milk and may limit the growth of suckling, neonatal animal. In this study, we tested whether providing an activator of arginine synthesis, N-carbamylglutamate, could increase growth of neonatal pigs and whether it may do so by increasing the synthesis of tissue proteins. We found that pigs treated with N-carbamylglutamate had higher levels of arginine and growth hormone in their blood. N-carbamylglutamate treated pigs also gained more weight than control pigs. The increase in growth was due, in part, to an increase in the synthesis of proteins in the skeletal muscle and in the intestine. The results suggest that oral supplementation of young growing mammals with N-carbamylglutamate increases plasma arginine and growth hormone levels, leading to an increase in growth rate and tissue protein synthesis.
Technical Abstract: This study investigated the potential mechanisms by which oral supplementation of “N”-carbamylglutamate (NCG), an analogue of endogenous “N“-acetylglutamate (an activator of arginine synthesis) increases growth rate in sow-reared piglets. Two piglets of equal body weight (BW) and of the same gender from each lactating sow were allotted to receive oral administration of 0 (control) or 50 mg of NCG/kg BW every 12 h for 7 d. Piglets (“n”=32; BW=3 kg) were studied in the food-deprived or fed state following the 7 d of treatment. Overnight food-deprived piglets were given NCG or water (control) at time 0 and 60 min. Piglets studied in the fed state were gavage-fed sow’s milk with their respective NCG treatment at 0 and 60 min. At 60 min, the piglets were administered a flooding dose of [(3)H]phenylalanine and killed at 90 min to measure tissue protein synthesis. Piglets treated with NCG gained 28% more weight than control pigs (“P”<0.001) over the 7-d period. Fed pigs had greater rates of protein synthesis in longissimus dorsi and gastrocnemius muscles and duodenum compared with food-deprived pigs (“P”<0.001). Absolute protein synthesis rates in longissimus dorsi (“P”=0.050) and gastrocnemius (“P”=0.068) muscles were 30 and 21% greater, respectively, in NCG-treated compared with control pigs. Piglets supplemented with NCG also had greater plasma concentrations of arginine and somatotropin than control pigs (“P”<0.001). The results suggest that oral NCG supplementation increases plasma arginine and somatotropin levels, leading to an increase in growth rate and muscle protein synthesis in nursing piglets.