Diabetes, Vol 37, Issue 1 28-32, Copyright © 1988 by American Diabetes Association
Additive hypoglycemic effects of drugs that modify free-fatty acid metabolism by different mechanisms in rats with streptozocin-induced diabetes
GM Reaven, H Chang and BB Hoffman
Department of Medicine, Stanford University School of Medicine, Palo Alto, California.
In this study the effect of two drugs [etomoxir and nicotinic acid (NA)] on
plasma glucose, free-fatty acid (FFA), and triglyceride (TG) concentrations
was determined in rats with streptozocin (STZ)-induced diabetes. The two
compounds modify FFA metabolism by different mechanisms, etomoxir
(ethyl-2-[6-(4-cholorophenoxyl)-hexyl]oxirane-2-carboxylate) by inhibiting
hepatic fatty acid oxidation, and NA by inhibiting lipolysis in adipose
tissue. Diabetes was induced in male Sprague-Dawley rats, weighing
approximately 400 g, by STZ injection (30 mg/kg i.v.), and the metabolic
effects of the two drugs were studied 7-10 days later. The acute
administration of either etomoxir or NA lowered plasma glucose
concentrations in diabetic rats by approximately 150 mg/dl (P less than
.001) in 4 h. However, the two drugs differed dramatically in their effects
on plasma FFA and TG concentrations. Specifically, etomoxir produced
striking increases in plasma FFA and TG concentrations, whereas NA
administration caused a marked decrease. However, when NA was given in
conjunction with etomoxir, NA prevented the increase in plasma FFA and TG
concentration seen with etomoxir; the combination of NA and etomoxir
approximately doubled the decrease in plasma glucose concentration produced
by NA or etomoxir when given alone. Because plasma insulin concentrations
did not change in response to either drug, whether administered singly or
in combination, these metabolic effects do not result from a change in
insulin secretion. These results suggest that modulation of FFA metabolism
at the level of the adipocyte or the liver can have dramatic effects on
carbohydrate and lipid metabolism.