Endurance Exercise Elicits a Hepatic Memory Associated with Improved Metabolic Function and Protein Secretion.

Endurance exercise protects against metabolic dysfunction-associated steatotic liver disease (MASLD), yet whether these effects persist following cessation of training remains unclear. Here, we employed endurance training cycles in mice to isolate the hepatic memory of exercise. Our results indicate that endurance retraining potentiates systemic and hepatic glucoregulatory benefits. Exercise retraining persistently reduced hepatic steatosis, hallmarked by decreases in diacylglycerols and increased phosphatidylcholines (PC). Liver transcriptomic analysis identified lipid and protein secretory pathways induced by endurance retraining. Importantly, retraining enhanced hepatic expression of carboxylesterases, including Ces2b, Ces3a, Ces3b, and Ces4a, and increased circulating carboxylesterase activity and CES4A protein levels. Exercise retraining reduced serum LDL-c and increased HDL-c, while enhancing the delivery of lysoPC and PC, predicted targets of carboxylesterases, to the working muscle. Similarly, mice fed an obesogenic diet demonstrate that this hepatic memory of exercise persists under an obesogenic challenge. In humans, we show that a 6-week training period increases serum CES activity primarily in individuals with prior training. Lastly, our studies identify the PPAR-RXR-clock axis as a potential trigger that may engage the synchronized lipid delivery to skeletal muscle and support fatty acid oxidation. Together, these findings suggest that endurance retraining elicits a hepatic exercise memory characterized by persistent transcriptional reprogramming and lipid remodeling that restore metabolic benefits after inactivity and confer resilience against MASLD.