Dube, John J., Coen, Paul M., DiStefano, Giovanna, Chacon, Alexander C., Helbling, Nicole L., Desimone, Marisa E., Stafanovic-Racic, Maja, Hames, Kazanna C., Despines, Alex A., Toledo, Frederico G. S., Goodpaster, Bret H.
funding text
The work was funded by National Institute of Diabetes and Digestive and Kidney Diseases Grant K01-DK-084213-01 (J. J. Dube), the University of Pittsburgh CTRC (M01-RR-00056), the Lipidomics Shared Resource, Hollings Cancer Center, the Medical University of South Carolina (P30 CA138313), and the Lipidomics Core in the SC Lipidomics and Pathobiology COBRE (P20 RR017677).
abstract
We hypothesized that acute lipid-induced insulin resistance would be attenuated in high-oxidative muscle of lean trained (LT) endurance athletes due to their enhanced metabolic flexibility and mitochondrial capacity. Lean sedentary (LS), obese sedentary (OS), and LT participants completed two hyperinsulinemic euglycemic clamp studies with and without (glycerol control) the coinfusion of Intralipid. Metabolic flexibility was measured by indirect calorimetry as the oxidation of fatty acids and glucose during fasted and insulin-stimulated conditions, the latter with and without lipid oversupply. Muscle biopsies were obtained for mitochondrial and insulin-signaling studies. During hyperinsulinemia without lipid, glucose infusion rate (GIR) was lowest in OS due to lower rates of nonoxidative glucose disposal (NOGD), whereas state 4 respiration was increased in all groups. Lipid infusion reduced GIR similarly in all subjects and reduced state 4 respiration. However, in LT subjects, fat oxidation was higher with lipid oversupply, and although glucose oxidation was reduced, NOGD was better preserved compared with LS and OS subjects. Mitochondrial performance was positively associated with better NOGD and insulin sensitivity in both conditions. We conclude that enhanced mitochondrial performance with exercise is related to better metabolic flexibility and insulin sensitivity in response to lipid overload.