LACTATE SPARES GLUCOSE AS A METABOLIC FUEL IN NEURONS AND ASTROCYTES FROM PRIMARY CULTURE

The effect of lactate on glucose metabolism in neurons and astrocytes from primary culture has been studied. The rates of glucose metabolism through the pentose-phosphate shunt, the pyruvate dehydrogenase-catal yzed reaction, the tricarboxylic acid cycle, the total lipogenesis and the synthesis of glycerol-borne lipids in astrocytes were 2-3 fold hi gher than in neurons. However, the rate of glucose incorporation into sterols and esterified fatty acids was similar in both types of cells. Total glucose utilization was inhibited by lactate to the same extend in both neurons and astrocytes. Lactate strongly inhibited glucose ox idation through the pyruvate dehydrogenase-catalyzed reaction and the tricarboxylic acid cycle, in both neurons (60 and 44%, respectively) a nd astrocytes (64 and 62%, respectively). Glucose incorporation into s terols and fatty acids was also inhibited by lactate in both neurons a nd astrocytes (57 and 76%, respectively) while the oxidation of glucos e in the pentose-phosphate shunt and the synthesis of glycerol-borne l ipids was not significantly affected. These results suggest that in th e presence of lactate both neurons and astrocytes can utilize lactate as the major metabolic substrate, sparing glucose for the synthesis of NADPH(H+), ribose-5-phosphate and/or glycerol-borne lipids. An intera ction between glucose and lactate metabolism at the level of the pyruv ate dehydrogenase-catalyzed reaction is suggested. Copyright (C) 1996 Elsevier Science Ireland Ltd