Factors influencing the utilization of ketone bodies by mouse adipose tissue

Abstract

Factors influencing the utilization of ketone bodies by mouse adipose tissue in vitro were studied. Epididymal fat pads can oxidize dl-Β-hydroxybutyrate-3-14C and acetoacetate-3-14C to 14CO2 as well as convert these compounds to fatty acid-14C. An increased output of 14CO2 from Β-hydroxybutyrate-3-14C was noted in response to glucose plus insulin, succinate, oxaloacetate, l-asparate, and l-malate. Fatty acid synthesis from Β-hydroxybutyrate was enhanced by glucose plus insulin, l-aspartate, l-malate, oxaloacetate, and citrate.Nicotinamide stimulated the oxidation of Β-hydroxybutyrate but not of acetoacetate to CO2, and did not affect fatty acid synthesis from either ketone body. Nicotinamide increased NAD+ and NADP+ levels in epididymal fat pads without affecting the concentration of NADH and NADPH. “Superlipogenesis” caused by fasting the mice for 48 hr and re-feeding them for 24 hr sharply enhanced CO2 output and lipogenesis from Β-hydroxybutyrate. The activities of glucose-6-phosphate dehydrogenase, 6-phosphogluconic dehydrogenase, NADP-malic dehydrogenase, and citrate cleavage enzyme from mouse adipose tissue were increased during “superlipogenesis.” Free fatty acid release by epididymal fat pads in vitro was slightly increased by Β-hydroxybutyrate. The relationship of ketone body metabolism and lipogenesis in adipose tissue is discussed.

Keywords

• adipose tissue
• ketone bodies
• metabolism
• oxidation
• conversion to fatty acid
• lipogenesis