165-OR: High- and Moderate-Intensity Exercise Training Increased Skeletal Muscle Acylcarnitine and Phospholipid Abundance in Obese Adults

The primary aim of this study was to determine the impact of high-intensity interval training [HIIT] and moderate-intensity continuous training [MICT] on skeletal muscle lipidomic profile in obese adults. 17 obese adults (BMI = 34±3 kg·m^-2; age = 31±6 years) completed 12 weeks of either HIIT (10 x 1 min @ 90%HRmax + 1 min recovery between intervals; n=8) or MICT (45 min steady-state exercise at 70% HRmax; n=9). Subjects exercised 4d/week and body weight was strictly maintained to assess the direct effects of exercise, independent of changes in body weight or fat mass. Skeletal muscle samples were collected from the vastus lateralis after an overnight fast both before training and 4 days after the last exercise session (to wash out the acute effects of exercise). Using shotgun lipidomics (LC MS/MS) we detected 734 lipid species from 26 different classes. Neither MICT nor HIIT significantly altered abundance of the primary muscle acylglycerides (tri- and di-acylglyceride) or ceramide abundance. Muscle acylcarnitine abundance increased after both MICT and HIIT (main effect, P = 0.04), specifically polyunsaturated acylcarnitines (P = 0.03). We also found phosphatidylcholine (PC) increased after training in both groups (main effect, P = 0.03), while the increase in phosphatidylethanolamine (PE) was greater after HIIT compared with MICT (P = 0.01). When normalized to cardiolipin (which is found almost exclusively in the inner mitochondrial membrane), the increased abundances of PC and PE were no longer apparent. Therefore, the training-induced increase in these phospholipids may largely reflect increased mitochondrial biosynthesis with training. In contrast, the observed increase in polyunsaturated acylcarnitines may represent an important adaptive response in the coordination of fatty acid metabolism in skeletal muscle after training. Overall, changes in muscle lipid profile were surprisingly similar in HIIT and MICT.