Gender differences in leucine, but not lysine, kinetics

• Published in: Journal of applied physiology (1985) Vol. 91; no. 1; pp. 357 - 362
• Main Authors: Lamont, Linda S, McCullough, Arthur J, Kalhan, Satish C
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01.07.2001; American Physiological Society
• Subjects: Adult; Aminoacids, peptides. Hormones. Neuropeptides; Analytical, structural and metabolic biochemistry; Biological and medical sciences; Blood - metabolism; Calorimetry, Indirect; Carbohydrate Metabolism; Differences; Energy Metabolism; Exercise - physiology; Fats - metabolism; Female; Fundamental and applied biological sciences. Psychology; Gender; Homeostasis; Humans; Kinetics; Leucine - metabolism; Lysine - metabolism; Male; Oxidation-Reduction; Proteins; Sex Characteristics; Urine - chemistry; Physical exercise; Human; Menstrual cycle; Aminoacid; Sex; Kinetics; Leucine; Metabolism
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/jappl.2001.91.1.357

1  Exercise Science Program, University of Rhode Island, Kingston, Rhode Island 02881; and 2  The Schwartz Center for Metabolism and Nutrition, Case Western Reserve University School of Medicine at MetroHealth Medical Center, Cleveland, Ohio 44109 There is a controversy in the literature as to the effects of gender on leucine kinetics. Two research groups found that men oxidize more leucine during exercise, whereas another group showed no gender effects. The purpose of our study was to examine the effects of gender on leucine and, for comparison purposes, lysine kinetics. Our subjects ( n  = 14) were seven matched pairs of men and women selected for their exercise habits and age. After 1   wk of a standardized diet, they exercised at 50% of maximal O 2 uptake for 1 h. There was an effect of exercise in both genders: an increased leucine oxidation and an attenuation in nonoxidative leucine disposal compared with rest ( P  < 0.05). Furthermore, our study confirms that there are gender differences in leucine, but not lysine, kinetics. Men had a higher rate of leucine oxidation and a lower rate of nonoxidative leucine disposal during exercise ( P  < 0.05). For women, a larger proportion of their exercise energy needs came from fat; for men, a greater fraction came from carbohydrate ( P  < 0.05). We conclude that female exercisers rely to a greater extent on fat as an energy source, thereby using less carbohydrate, amino acid, and protein as a fuel source. L -[1- 13 C]leucine; L -[ - 15 N]lysine; moderate-intensity exercise