Effects of food restriction on lactate production from glucose by rat adipocytes

We investigated the effects of acute food deprivation on the rates of glucose metabolism and lactate production by epididymal fat cells isolated from 2- and 8-mo-old Wistar rats in one of three nutritional states: fed ad libitum, restricted to 50% of ad libitum, or fasted for 48 h. Food restriction did not affect total rates of basal glucose metabolism but significantly altered its pattern. In small fat cells from 2-mo-old rats, donor's food restriction led to decreased basal and insulin-stimulated glucose oxidation and fatty acid synthesis but led to increased lactate production, which increased from 4% of total glucose metabolized by cells from fed rats to 62% by cells from fasted rats. In large fat cells from 8-mo-old rats, donor's food restriction produced minimal changes in basal glucose metabolism and lactate production (already elevated at 37% of total) but caused insulin-stimulated lactate production to increase. These findings indicate that adipose tissue can produce significant amounts of lactate (with adipocyte enlargement and/or food deprivation) and may play an important role in extrahepatic generation of triose intermediates and in the Cori cycle.