AJP - Endocrinology and Metabolism, Vol 247, Issue 4 462-E467, Copyright © 1984 by American Physiological Society
Diabetes-induced alterations of glucose metabolism in rat cerebral microvessels
A. L. McCall, J. B. Gould and N. B. Ruderman
The effect of diabetes on the metabolism of glucose and lactate was
examined in isolated rat cerebral microvessels. In rats with diabetes
induced with streptozotocin, glucose oxidation to CO2 by the microvessels
was decreased by 54-83% and its conversion to lactate by 21-61%. Insulin
therapy for several days or starvation for 48 h both lowered blood glucose
levels in the diabetic rats and restored microvessel glucose metabolism to
normal. Cerebral microvessels consist principally of the capillaries that
constitute the blood-brain barrier. Direct assessment of the blood-brain
barrier in vivo using the brain uptake index (BUI) technique revealed a
close parallel to the findings in the microvessels. Thus, hexose transport
was diminished in diabetic rats and restored to normal by both insulin
therapy and starvation. The oxidation of [1-14C]lactate to CO2 like that of
glucose was depressed in microvessels of diabetic rats. In contrast to
glucose, however, the transport of lactate across the blood-brain barrier
in vivo was not altered. These findings suggest that diabetes suppresses
glucose metabolism in rat cerebral microvessels and downregulates glucose
transport across the blood-brain barrier. They also suggest that both of
these processes are regulated by chronic alterations in blood glucose
concentration rather than by insulin per se.
