Adenosine 3',5'-monophosphate-dependent protein kinase activity decreases in human muscle after insulin infusion.
We have previously reported that the increase in glycogen synthase activity in human muscle during a euglycemic clamp was not associated with a measured increase in glycogen synthase phosphatase activity after a 200-min insulin administration. To investigate further the mechanism of the regulation of human muscle glycogen synthase by insulin, we measured the activity of cAMP-dependent protein kinase before and after a 200-min hyperinsulinemic euglycemic clamp in Southwest American Indians. Insulin infusion resulted in a decreased cAMP-dependent protein kinase activity assayed at physiological cAMP concentration with increased glycogen synthase activity in all subjects (n = 5; P less than 0.01). No significant change was observed in cAMP-independent protein kinase activity. These results suggest that 200 min of insulin administration during a euglycemic clamp may regulate human muscle glycogen synthase activity by mechanisms other than the stimulation of phosphatase; one probable mechanism is by decreasing the activity of cAMP-dependent protein kinase.
Okubo
M
M
Clinical Diabetes and Nutrition Section, National Institute of Diabetes, Digestive and Kidney Diseases, Phoenix, Arizona 85016.
Bogardus
C
C
Lillioja
S
S
Mott
D M
DM
D000328:Adult; D001130:Arizona; D001786:Blood Glucose / Q000378:metabolism; D005260:Female; D006006:Glycogen Synthase / Q000378:metabolism; D006801:Humans; D007198:Indians, North American; D007328:Insulin / Q000097:blood / Q000494:pharmacology*; D007700:Kinetics; D008297:Male; D009132:Muscles / Q000187:drug effects / Q000201:enzymology*; D011494:Protein Kinases / Q000378:metabolism*
D001786:Blood Glucose; D007328:Insulin; D006006:Glycogen Synthase; D011494:Protein Kinases