Effect of short-term exercise training on intramyocellular lipid content

Abstract

The purpose of this study was to investigate the influence of exercise training on intramyocellular lipid (IMCL) content and test the hypothesis that the effect of endurance-oriented exercise training on IMCL is dependent on characteristics of the population studied. Lean (N = 11, body mass index (BMI) = 22.2 ± 0.7 kg·m⁻²), obese (N = 14, BMI = 38.8 ± 1.7 kg·m⁻²), and type 2 diabetic (N = 9, BMI = 35.5 ± 2.5 kg·m⁻²) participants were examined before and after 10 consecutive days of endurance-oriented (60 min·day⁻¹ at ~70% [Formula: see text]O(2peak)) exercise training. IMCL and muscle glycogen were measured by Oil-Red-O and periodic acid - Schiff staining, respectively. The results indicated that IMCL was elevated (p < 0.05) in the obese and diabetic groups compared with the lean subjects prior to training. After training, IMCL content decreased (-35%) in the participants with type 2 diabetes; there were no changes in IMCL in the lean or obese groups. Muscle glycogen content was lower in the diabetic subjects than in the lean subjects both before and after training. These data indicate that changes in IMCL with exercise training do not exhibit a universal response but rather depend on the metabolic status of the population studied.

Fig. 1

(A) Total and (B and C) fiber type specific (B, type I fibers; C, type II fibers) intramyocellular lipid (IMCL) content before and after 10 days of endurance-oriented exercise training in lean, obese, and type 2 diabetic subjects. Values are expressed as mean ± SE. Bars with different letters denote statistically significant differences (p < 0.05).

Fig. 2

Skeletal muscle glycogen content determined by periodic acid – Schiff stain (PAS) in skeletal muscle of sedentary lean, obese, and type 2 diabetic patients. Values are expressed as mean ± SE. Bars with different letters denote statistically significant differences (p < 0.05).

Fig. 3

(A) Total and (B and C) fiber type specific (B, type I fibers; C, type II fibers) skeletal muscle oxidative capacity measured by NADH tetrazoluum reductase stain. Values are expressed as mean ± SE.