Exercise training increases intramyocellular lipid and oxidative capacity in older adults

• Published in: American journal of physiology: endocrinology and metabolism 2004-11, Vol.287 (5), p.E857-E862
• Main Authors: Pruchnic, Ryan, Katsiaras, Andreas, He, Jing, Kelley, David E, Winters, Carena, Goodpaster, Bret H
• Format: Article
• Language: English
• Subjects: Aged - physiology; Body Composition; Exercise - physiology; Female; Humans; Insulin Resistance; Lipid Metabolism; Lipids - analysis; Male; Muscle Cells - chemistry; Muscle Cells - metabolism; Muscle, Skeletal - chemistry; Muscle, Skeletal - metabolism; Oxidation-Reduction; Oxygen Consumption; Physical Fitness - physiology; Reference Values
• ISSN: 0193-1849; 1522-1555
• DOI: 10.1152/ajpendo.00459.2003

Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213 Submitted 10 October 2003 ; accepted in final form 10 June 2004 Intramyocellular lipid (IMCL) has been associated with insulin resistance. However, an association between IMCL and insulin resistance might be modulated by oxidative capacity in skeletal muscle. We examined the hypothesis that 12 wk of exercise training would increase both IMCL and the oxidative capacity of skeletal muscle in older (67.3 ± 0.7 yr), previously sedentary subjects ( n = 13; 5 men and 8 women). Maximal aerobic capacity ( O 2 max ) increased from 1.65 ± 0.20 to 1.85 ± 0.14 l/min ( P < 0.05), and systemic fat oxidation induced by 1 h of cycle exercise at 45% of O 2 max increased ( P < 0.05) from 15.03 ± 40 to 19.29 ± 0.80 (µmol·min –1 ·kg fat-free mass –1 ). IMCL, determined by quantitative histological staining in vastus lateralis biopsies, increased ( P < 0.05) from 22.9 ± 1.9 to 25.9 ± 2.6 arbitrary units (AU). The oxidative capacity of muscle, determined by succinate dehydrogenase staining intensity, significantly increased ( P < 0.05) from 75.2 ± 5.2 to 83.9 ± 3.6 AU. The percentage of type I fibers significantly increased ( P < 0.05) from 35.4 ± 2.1 to 40.1 ± 2.3%. In conclusion, exercise training increases IMCL in older persons in parallel with an enhanced capacity for fat oxidation. skeletal muscle; physical activity; fiber type; triacylglycerol Address for reprint requests and other correspondence: B. H. Goodpaster, Dept. of Medicine, 809 North MUH, Univ. of Pittsburgh Medical Center, 3459 Fifth Ave., Pittsburgh, PA 15213 (E-mail: bgood{at}pitt.edu )