Acute exposure to GH during exercise stimulates the turnover of free fatty acids in GH-deficient men

• Published in: Journal of applied physiology (1985) 2004-02, Vol.96 (2), p.747-753
• Main Authors: Kanaley, Jill A, Dall, Rolf, Moller, Niels, Nielsen, Sven C, Christiansen, Jens Sandahl, Jensen, Michael D, Jorgensen, Jens Otto Lunde
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Biological and medical sciences; Blood Glucose - metabolism; Body Mass Index; C-Peptide - blood; Calorimetry, Indirect; Energy Metabolism - drug effects; Exercise; Exercise - physiology; Fatty acids; Fatty Acids, Nonesterified - metabolism; Fundamental and applied biological sciences. Psychology; Glucose; Hormones; Human Growth Hormone - administration & dosage; Human Growth Hormone - blood; Human Growth Hormone - deficiency; Humans; Insulin - blood; Male; Men; Metabolism; Middle Aged; Muscle Proteins - metabolism; Palmitates - pharmacokinetics; Phenylalanine - pharmacokinetics; Proteins; Tyrosine - pharmacokinetics
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00711.2003

1 Department of Exercise Science, Syracuse University, Syracuse, New York 13244; 2 Medical Department M (Endocrinology and Diabetes), 3 Department of Respiratory Diseases and Institute of Experimental Clinical Research, Aarhus University Hospital, DK 5000 Aarhus, Denmark; and 4 Endocrine Research Unit, Mayo Clinic, Rochester, Minnesota 55905 Submitted 9 July 2003 ; accepted in final form 23 October 2003 The secretion of growth hormone (GH) increases acutely during exercise, but whether this is associated with the concomitant alterations in substrate metabolism has not previously been studied. We examined the effects of acute GH administration on palmitate, glucose, and protein metabolism before, during, and after 45 min of moderate-intensity aerobic exercise in eight GH-deficient men (mean age = 40.8 ± 2.9 yr) on two occasions, with (+GH; 0.4 IU GH) and without GH administered (-GH). A group of healthy controls ( n = 8, mean age = 40.4 ± 4.2 yr) were studied without GH. The GH replacement during exercise on the +GH study mimicked the endogenous GH profile seen in healthy controls. No significant difference in resting free fatty acid (FFA) flux was found between study days, but during exercise a greater FFA flux was found when GH was administered (211 ± 26 vs. 168 ± 28 µmol/min, P < 0.05) and remained elevated throughout recovery ( P < 0.05). With GH administered, the exercise FFA flux was not significantly different from that observed in control subjects (188 ± 14 µmol/min), but the recovery flux was greater on the +GH day than in the controls (169 ± 17 vs. 119 ± 11 µmol/min, respectively, P < 0.01). A significant time effect ( P < 0.01) for glucose rate of appearance from rest to exercise and recovery occurred in the GH-deficient adults and the controls, whereas there were no differences in glucose rate of disappearance. No significant effect across time was found for protein muscle balance. In conclusion, 1 ) acute exposure to GH during exercise stimulates the FFA release and turnover in GH-deficient adults, 2 ) GH does not significantly impact glucose or protein metabolism during exercise, and 3 ) the exercise-induced secretion of GH plays a significant role in the regulation of fatty acid metabolism. lipolysis; glucose turnover; protein turnover; growth hormone Address for reprint requests and other correspondence: J. A. Kanaley, 820 Comstock Ave., Rm. 201, Syracuse, NY 13244 (E-mail: jakanale{at}syr.edu ).