The Effect of a 3-Month Low-Intensity Endurance Training Program on Fat Oxidation and Acetyl-CoA Carboxylase-2 Expression

Abstract

Endurance training has been shown to increase fat oxidation both at rest and during exercise. However, most exercise training studies have been performed at high exercise intensity in well-trained athletes, and not much is known about the effect of a low-intensity training program on fat oxidation capacity in lean sedentary humans. Here, we examine the effect of 3-month low-intensity training program on total and intramuscular triglyceride (IMTG)- and/or VLDL-derived fat oxidation capacity and skeletal muscle mRNA expression. Six healthy untrained subjects (aged 43 ± 2 years, BMI 22.7 ± 1.1 kg/ m², Vo_2max 3.2 ± 0.2 l/min) participated in a supervised 12-week training program at 40% Vo_2max three times weekly. Total and plasma-derived fatty acid oxidation at rest and during 1 h exercise was measured using [¹³C]palmitate, and in a separate test, [¹³C]acetate recovery was determined. Muscle biopsies were taken after an overnight fast. Total fat oxidation during exercise increased from 1,241 ± 93 to 1,591 ± 130 μmol/min (P = 0.06), and IMTG- and/or VLDL-derived fatty acid oxidation increased from 236 ± 84 to 639 ± 172 μmol/min (P = 0.09). Acetyl-CoA carboxylase-2 mRNA expression was significantly decreased after training (P = 0.005), whereas lipoprotein lipase mRNA expression tended to increase (P = 0.07). In conclusion, a minimal amount of physical activity tends to increase fat oxidation and leads to marked changes in the expression of genes encoding for key enzymes in fat metabolism.