Abstract
Energy stored in adipocytes as triglycerides is mobilized via lipolysis, releasing fatty acids and glycerol into the circulation. Re-esterification of fatty acids that remain within the adipose tissue is the primary driver of adipocyte ATP consumption. Paradoxically, re-esterification suppresses respiration in lipolytic adipocytes. We previously found that STAT3 drives respiration by inhibiting re-esterification via GPAT3. Here we show that free fatty acids drive uncoupled respiration in complex with the ATP/ADP carriers. The impacts of lipolysis and re-esterification on uncoupled respiration correspond with fatty acids, not fatty acyl-CoAs or beta-oxidation. Under standard housing conditions, brown adipocyte uncoupling via uncoupling protein 1 is the dominant thermogenic pathway. However, in obese thermoneutral-adapted mice, uncoupled respiration in white adipocytes contributes to thermogenesis and cold tolerance, independent of brown adipose tissue or muscle activity. Our results suggest that uncoupled respiration in white adipocytes contributes to whole-body energy expenditure and could be a promising target for obesity treatment.