AJP - Endocrinology and Metabolism, Vol 250, Issue 4 346-E351, Copyright © 1986 by American Physiological Society
Inhibition of hepatic glucose production by insulin in vivo in rats: contribution of glycolysis
J. Terrettaz, F. Assimacopoulos-Jeannet and B. Jeanrenaud
The action of insulin on hepatic glucose production (HGP) has been studied
in fed anesthetized rats during a euglycemic hyperinsulinemic clamp. At the
end of the clamp, the liver was rapidly removed, frozen, and enzyme
activities and metabolites were measured. When insulin totally suppressed
HGP, it did not modify glycogen phosphorylase or synthase activity, nor did
it "spare" or increase glycogen content. Insulin decreased glucose
6-phosphate while increasing glycolytic intermediates (fructose
1,6-bisphosphate, alpha-glycerophosphate, lactate, and pyruvate) as well as
fructose 2,6-bisphosphate, the potent effector of 6-phosphofructo-1-kinase.
Insulin also increased pyruvate kinase activity of low substrate
concentration. Lipogenesis measured with 3H2O incorporation into fatty
acids was increased four-to fivefold by insulin. The data suggest that in
normal rat liver, when glycemia is maintained at constant basal level,
insulin promotes no change in glycogen metabolism, whereas the hormone
stimulates the glycolytic pathway. This action contributes to the
suppression of hepatic glucose production observed after the addition of
the hormone.
