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 lowintensity 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/m 2 , 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 [13 C]palmitate, and in a separate test, [ 13 C]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 mol/min (P ‫؍‬ 0.06), and IMTG-and/or VLDL-derived fatty acid oxidation increased from 236 ؎ 84 to 639 ؎ 172 mol/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. Diabetes 51:2220 -2226, 2002

Acylation-stimulating protein: effect of acute exercise and endurance training

“…It should be noted that, in the trained state, the skeletal muscle relies less on the oxidation of plasma FFA but also uses intramuscular triglycerides and VLDL triglycerides as a source of energy. 38,18 In conclusion, our data show that short-term endurance training reduces baseline ASP levels. This reduction is accompanied by a diminished exercise-induced increase in NEFA.…”

“…[15][16][17][18] In a recent study, we showed that a 3-month low-intensity endurance training program in previously untrained, sedentary males improved fat oxidative capacity and lowered plasma triglyceride levels. 18 In the present study, we could not detect any changes in fat oxidative capacity at the whole body level, probably due to the shortterm nature of the present training program. However, we did find that the increase in plasma FFA levels during exercise was already diminished after 2 weeks of endurance training, indicating improved fatty acid handling.…”

“…However, regular exercise training improves many aspects of fatty acid metabolism. [15][16][17][18] For example, the increase in plasma FFA levels during acute exercise of a similar intensity is lower in trained subjects, probably due to a blunted sympatho-adrenic-induced lipolysis [19][20][21][22] and an improved fatty acid re-esterification, 23,16 both indicating an improved fatty acid handling. It could therefore be hypothesized that endurance training might lead to a reduction in basal ASP levels, indicating improved ASP sensitivity.…”

Lipotoxicity: the obese and endurance-trained paradox

“…We have recently termed these different IMTG pools as 'good' and 'bad' lipids, with the IMTG stored as an adaptation to ETr and continually utilised for energy production as the 'good lipids', while the stagnant IMTGs accumulated in the obese skeletal muscle as the 'bad lipids'. 9 Other adaptations to Etr, such as increases in the activity of antioxidant molecules (such as glutathione peroxidase (GPX) and superoxide dismutase (SOD)), 57 increases in the percentage of the highly oxidative and insulinsensitive type I muscle fibres 61,62 as well as the increases in the b-oxidation pathway, 63,64 would also assist with the reduced risk of lipid peroxidation and insulin resistance.…”

Disassociation of muscle triglyceride content and insulin sensitivity after exercise training in patients with Type 2 diabetes

“…Indeed, exercise training has been shown to increase TG m content in muscle from healthy individuals [11], suggesting that the presence of triacyglycerol in the myocyte is not always associated with insulin insensitivity. In addition, it has been reported that the capacity to oxidize TG m and/or VLDL-derived fatty acids is increased both at rest and during exercise following a 3-month low intensity (40% of VO 2 peak) training program, and that increased rates of TG m oxidation could be beneficial in the prevention/treatment of Type 2 diabetes [12]. However, to date the effects of exercise training on insulin sensitivity and muscle lipid status in Type 2 diabetic patients has not been determined.…”