AJP - Endocrinology and Metabolism, Vol 254, Issue 3 E272-E278, Copyright © 1988 by American Physiological Society
Effects of hypoglycemia and diabetes on fuel metabolism by rat brain microvessels
A. L. McCall, I. Sussman, K. Tornheim, R. Cordero and N. B. Ruderman
Evans Memorial Department of Medicine, Boston University School of Medicine, Massachusetts.
Glucose and beta-hydroxybutyrate metabolism were compared in isolated
cerebral microvessels from chronically diabetic and hypoglycemic rats. As
noted previously, glucose oxidation and conversion to lactate are
diminished in rats with streptozotocin-induced diabetes. The decrease in
glucose metabolism did not result from selective damage to diabetic vessels
during isolation, since the ATP level and the ATP/ADP ratio were similar to
those of nondiabetic rats, and O2 consumption was increased. In addition,
cerebral microvessel oxidation of beta-hydroxybutyrate was enhanced by
diabetes. By contrast, microvessels from rats made chronically hypoglycemic
by insulinoma engrafting 30 days earlier had a more than twofold increase
in glucose oxidation and conversion to lactate, whereas their oxidation of
beta-hydroxybutyrate was diminished by 50%. Unlike the insulinoma rats, no
consistent increase in glucose metabolism was observed in microvessels from
rats made hypoglycemic either by acute insulin administration or by a 4-day
infusion of insulin. These results indicate that diabetes, and under some
circumstances chronic hypoglycemia, markedly alters fuel metabolism in the
cerebral microvasculature.
