Response of skeletal muscle protein synthesis to insulin in suckling pigs decreases with development.
The elevated rate of muscle protein deposition in the neonate is largely due to an enhanced stimulation of skeletal muscle protein synthesis by feeding. To examine the role of insulin in this response, hyperinsulinemic-euglycemic-amino acid clamps were performed in 7- and 26-day-old pigs. Pigs were infused with 0, 30, 100, or 1,000 ng . kg-0.66 . min-1 of insulin to mimic the plasma insulin levels observed under fasted, fed, refed, and supraphysiological conditions, respectively. Whole body amino acid disposal was determined from the rate of infusion of an amino acid mixture necessary to maintain plasma essential amino acid concentrations near their basal fasting levels. A flooding dose of L-[4-3H]phenylalanine was used to measure skeletal muscle protein synthesis. Whole body amino acid disposal increased progressively as the insulin infusion rate increased, and this response was greater in 7- than in 26-day-old pigs. Skeletal muscle protein synthesis was stimulated by insulin, and this response was maximal at a low insulin infusion rate (30 ng . kg-0.66 . min-1). The stimulation of muscle protein synthesis by insulin was also greater in 7- than in 26- day-old pigs. These data suggest that muscle protein synthesis is more sensitive to insulin than whole body amino acid disposal. The results further suggest that insulin is a central regulatory factor in the elevated rate of muscle protein deposition and the increased response of skeletal muscle protein synthesis to feeding in the neonate.
Wray-Cahen
D
D
United States Department of Agriculture, Agricultural Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030, USA.
Nguyen
H V
HV
Burrin
D G
DG
Beckett
P R
PR
Fiorotto
M L
ML
Reeds
P J
PJ
Wester
T J
TJ
Davis
T A
TA
D000596:Amino Acids / Q000097:blood; D000818:Animals; D000831:Animals, Newborn; D000833:Animals, Suckling; D001786:Blood Glucose / Q000378:metabolism; D003433:Crosses, Genetic; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D015309:Glucose Clamp Technique; D006946:Hyperinsulinism / Q000503:physiopathology; D007262:Infusions, Intravenous; D007328:Insulin / Q000008:administration & dosage / Q000494:pharmacology* / Q000502:physiology; D008297:Male; D024510:Muscle Development; D009124:Muscle Proteins / Q000096:biosynthesis* / Q000235:genetics; D018482:Muscle, Skeletal / Q000254:growth & development / Q000378:metabolism*; D013552:Swine
D000596:Amino Acids; D001786:Blood Glucose; D007328:Insulin; D009124:Muscle Proteins