Acetoacetate and <sc>d</sc>- and <sc>l</sc>-β-hydroxybutyrate have distinct effects on basal and insulin-stimulated glucose uptake in L6 skeletal muscle cells

Ketone bodies (acetoacetate and beta-hydroxybutyrate) are oxidized in skeletal muscle mainly during fasting as an alternative source of energy to glucose. Previous studies suggest that there is a negative relationship between increased muscle ketolysis and muscle glucose metabolism in mice with obesity and/or type 2 diabetes. Therefore, we investigated the connection between increased ketone body exposure and muscle glucose metabolism by measuring the effect of a 3-h exposure to ketone bodies on glucose uptake in differentiated L6 myotubes. We showed that exposure to acetoacetate at a typical concentration (0.2 mM) resulted in increased basal glucose uptake in L6 myotubes, which was dependent on increased membrane glucose transporter type 4 (GLUT4) translocation. Basal and insulin-stimulated glucose uptake was also increased with a concentration of acetoacetate reflective of diabetic ketoacidosis or a ketogenic diet (1 mM). We found that beta-hydroxybutyrate had a variable effect on basal glucose uptake: a racemic mixture of the two beta-hydroxybutyrate enantiomers (d and l) appeared to decrease basal glucose uptake, while 3 mM d-beta-hydroxybutyrate alone increased basal glucose uptake. However, the effects of the ketone bodies individually were not observed when acetoacetate was present in combination with beta-hydroxybutyrate. These results provide insight that will help elucidate the effect of ketone bodies in the context of specific metabolic diseases and nutritional states (e.g., type 2 diabetes and ketogenic diets).