Effect of brief exercise on circulating insulin-like growth factor I.
An acute insulin-like growth factor I (IGF-I) response to 10 min of above-lactate threshold cycle ergometer exercise was studied in 10 subjects (age 22-35 yr). Each subject exercised on three separate mornings after ingesting one of two isocaloric isovolemic liquid meals high in either fat or glucose or an isovolemic noncaloric placebo. The high-fat meal attenuated the growth hormone (GH) response (Cappon et al., J. Clin. Endocrinol. Metab. 76: 1418-1422, 1993). In contrast, IGF-I increased equally for all protocols [e.g., after the placebo meal IGF-I increased from 21,716 (SE) ng/ml preexercise to 25,316 ng/ml at 10 min of exercise; P < 0.05]. IGF-I peaked by the 10th min of exercise, like GH, and remained significantly elevated for only 20 min of recovery. We tested for possible GH-dependent mechanisms in which circulating IGF-I would increase 12-24 h after exercise. Ten subjects (age 23-32 yr) performed 10 min of above-lactate threshold exercise at 9, 10, and 11 A.M. GH was elevated after the first exercise bout (peak GH 6.05 +/- 1.45 ng/ml; P < 0.001) but was significantly reduced for the second and third bouts (peak GH 2.52 +/- 0.76 and 1.50 +/- 0.40 ng/ml, respectively). No increase in IGF-I was observed by 8 A.M. on the following day. Heavy ergometer exercise led to brief and small increases in circulating IGF-I that were independent of circulating GH.(ABSTRACT TRUNCATED AT 250 WORDS)
Cappon
J
J
Department of Pediatrics, Harbor-University of California at Los Angeles Medical Center, Torrance 90509.
Brasel
J A
JA
Mohan
S
S
Cooper
D M
DM
D000328:Adult; D015308:Anaerobic Threshold / Q000502:physiology; D001786:Blood Glucose / Q000378:metabolism; D015444:Exercise / Q000502:physiology*; D005260:Female; D013006:Growth Hormone / Q000502:physiology; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007773:Lactates / Q000097:blood; D019344:Lactic Acid; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D011659:Pulmonary Gas Exchange / Q000502:physiology; D011773:Pyruvates / Q000097:blood; D019289:Pyruvic Acid; D013004:Somatostatin / Q000097:blood
D001786:Blood Glucose; D007773:Lactates; D011773:Pyruvates; D019344:Lactic Acid; D013004:Somatostatin; D007334:Insulin-Like Growth Factor I; D019289:Pyruvic Acid; D013006:Growth Hormone