Stimulation of protein synthesis by both insulin and amino acids is unique to skeletal muscle in neonatal pigs.
In neonatal pigs, the feeding-induced stimulation of protein synthesis in skeletal muscle, but not liver, can be reproduced by insulin infusion when essential amino acids and glucose are maintained at fasting levels. In the present study, 7- and 26-day-old pigs were studied during 1) fasting, 2) hyperinsulinemic-euglycemic-euaminoacidemic clamps, 3) euinsulinemic-euglycemic-hyperaminoacidemic clamps, and 4) hyperinsulinemic-euglycemic-hyperaminoacidemic clamps. Amino acids were clamped using a new amino acid mixture enriched in nonessential amino acids. Tissue protein synthesis was measured using a flooding dose of L-[4-(3)H]phenylalanine. In 7-day-old pigs, insulin infusion alone increased protein synthesis in various skeletal muscles (from +35 to +64%), with equivalent contribution of myofibrillar and sarcoplasmic proteins, as well as cardiac muscle (+50%), skin (+34%), and spleen (+26%). Amino acid infusion alone increased protein synthesis in skeletal muscles (from +28 to +50%), also with equivalent contribution of myofibrillar and sarcoplasmic proteins, as well as liver (+27%), pancreas (+28%), and kidney (+10%). An elevation of both insulin and amino acids did not have an additive effect. Similar qualitative results were obtained in 26-day-old pigs, but the magnitude of the stimulation of protein synthesis by insulin and/or amino acids was lower. The results suggest that, in the neonate, the stimulation of protein synthesis by feeding is mediated by either amino acids or insulin in most tissues; however, the feeding-induced stimulation of protein synthesis in skeletal muscle is uniquely regulated by both insulin and amino acids.
Davis
Teresa A
TA
United States Department of Agriculture/Agricultural Research Service, Children's Nutrition Research Center, and Endocrinology and Metabolism Section, Baylor College of Medicine, Houston, Texas 77030, USA. tdavis@bcm.tmc.edu
Fiorotto
Marta L
ML
Burrin
Douglas G
DG
Reeds
Peter J
PJ
Nguyen
Hanh V
HV
Beckett
Philip R
PR
Vann
Rhonda C
RC
O'Connor
Pamela M J
PM
D000596:Amino Acids / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism*; D001786:Blood Glucose / Q000378:metabolism; D004347:Drug Interactions; D005215:Fasting; D005260:Female; D005947:Glucose / Q000008:administration & dosage; D015309:Glucose Clamp Technique; D007328:Insulin / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D007700:Kinetics; D009124:Muscle Proteins / Q000096:biosynthesis*; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D010649:Phenylalanine / Q000378:metabolism; D013552:Swine / Q000378:metabolism*; D014316:Tritium
D000596:Amino Acids; D001786:Blood Glucose; D007328:Insulin; D009124:Muscle Proteins; D014316:Tritium; D010649:Phenylalanine; D005947:Glucose