Modulation of muscle protein synthesis by insulin is maintained during neonatal endotoxemia.
Sepsis promotes insulin resistance and reduces protein synthesis in skeletal muscle of adults. The effect of sepsis on insulin-stimulated muscle protein synthesis has not been determined in neonates, a highly anabolic population that is uniquely sensitive to insulin. Overnight fasted neonatal pigs were infused for 8 h with endotoxin [lipopolysaccharide (LPS), 0 and 10 mug.kg(-1).h(-1)]. Glucose and amino acids were maintained at fasting levels, insulin was clamped at either fasting or fed (2 or 10 muU/ml) levels, and fractional protein synthesis rates were determined at the end of the infusion. LPS infusion induced a septic-like state, as indicated by a sustained elevation in body temperature, heart rate, and cortisol. At fasting insulin levels, LPS reduced fractional protein synthesis rates in gastrocnemius muscle (-26%) but had no effect on the masseter and heart. By contrast, LPS stimulated liver protein synthesis (+28%). Increasing insulin to fed levels accelerated protein synthesis rates in gastrocnemius (controls by +38%, LPS by +60%), masseter (controls by +50%, LPS by +43%), heart (controls by +34%, LPS by +40%), and diaphragm (controls by +54%, LPS by +29%), and the response to insulin was similar in LPS and controls. Insulin did not alter protein synthesis in liver, kidney, or jejunum in either group. These findings suggest that acute endotoxemia lowers basal fasting muscle protein synthesis in neonates but does not alter the response of protein synthesis to insulin.
USDA/ARS Children's Nutrition Research Center, Baylor College of Medicine, 1100 Bates St., Suite 9064, Houston, TX 77030-2600, USA.
Renan A
RA
Orellana
Pamela M J
PM
O'Connor
Jill A
JA
Bush
Agus
A
Suryawan
M Carole
MC
Thivierge
Hanh V
HV
Nguyen
Marta L
ML
Fiorotto
Teresa A
TA
Davis
D000597:Amino Acids, Branched-Chain / Q000097:blood / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D001786:Blood Glucose / Q000378:metabolism; D019446:Endotoxemia / Q000097:blood / Q000378:metabolism*; D005260:Female; D015309:Glucose Clamp Technique; D006854:Hydrocortisone / Q000097:blood; D007328:Insulin / Q000097:blood / Q000494:pharmacology*; D008070:Lipopolysaccharides; D009124:Muscle Proteins / Q000096:biosynthesis* / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000503:physiopathology; D011247:Pregnancy; D014176:Protein Biosynthesis / Q000187:drug effects; D011897:Random Allocation; D013552:Swine
D000597:Amino Acids, Branched-Chain; D001786:Blood Glucose; D007328:Insulin; D008070:Lipopolysaccharides; D009124:Muscle Proteins; D006854:Hydrocortisone