Rapid Accumulation of Triacylglycerol in the Liver is a Component of the Acute Exercise Response and May Serve a Protective Role Against Lipotoxicity

Abstract

We have previously shown that the content of triacylglycerol (TAG) in the liver transiently increases after a single bout of exercise in untrained mice, and this phenomenon has been observed in human subjects as well. This discovery depicted a new phenomenon in the metabolic exercise response. Here we propose the term “lipogenic flexibility” to describe this ability to rapidly alter hepatic TAG content in response to FFA supply. To explore lipogenic flexibility after exercise, we performed lipidomics analysis on liver samples obtained 3 hours after exercise and the following day. Female mice performed a single bout of continuous exercise (CE), high intensity interval exercise (HIIE), or no exercise (CON). The total concentration of hepatic TAG rose 3 hours after exercise (P < 0.05 for both CE and HIIE vs CON), but the total concentration of all other measured lipid classes remained unchanged after exercise (NSD). Hepatic TAG declined back to control levels by the day after exercise. We performed correlation analysis to test the association of TAG (an inert lipid depot) with lipotoxic lipid classes in the liver. Hepatic TAG was positively correlated with hepatic diacylglycerol (DAG) in CON (P < 0.05); however, during the hepatic TAG pool expansion after exercise, liver TAG and DAG were no longer significantly correlated with one another (NSD). Exhibiting lipogenic flexibility after exercise appears to break the equilibration between DAG and TAG, allowing fatty acids to be drawn toward the inert lipid pool (TAG) and away from the lipotoxic lipid pool (DAG). The results suggest that the TAG pool actively expands to buffer elevated FFA supply after exercise and may act to prevent lipotoxicity.Support or Funding InformationThis work was supported by the Faculty Research Grant Program of Rutgers University, the American Diabetes Association grant # 7‐13‐JF‐27‐BR to G Henderson, and the Purdue University College of Health and Human Sciences.