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The Journals of Gerontology Series A: Biological Sciences and Medical Sciences Advance Access published online on March 13, 2009
The Journals of Gerontology Series A: Biological Sciences and Medical Sciences, doi:10.1093/gerona/gln075
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© The Author 2009. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oxfordjournals.org.

Alterations in Oxygen Consumption, Respiratory Quotient, and Heat Production in Long-Lived GHRKO and Ames Dwarf Mice, and Short-Lived bGH Transgenic Mice

Reyhan Westbrook1,2, Michael S. Bonkowski1, April D. Strader3 and Andrzej Bartke1

1 Department of Physiology and Internal Medicine-Geriatrics Research
2 Department of Medical Microbiology and Immunology and Cell Biology, Southern Illinois University School of Medicine, Springfield
3 Department of Physiology, Southern Illinois University School of Medicine, Carbondale

Address correspondence to Reyhan Westbrook, BA, Department of Internal Medicine, Division of Geriatric Research, Southern Illinois University School of Medicine, 801 North Rutledge Street, Room 4389 P.O. Box 19628, Springfield, IL 62794-9628. Email: rwestbrook{at}siumed.edu


  Abstract

Growth hormone (GH) signaling influences longevity in mice, with decreased GH signaling associated with longer life span and increased GH signaling with shortened life span. A proposed mechanism through which GH signaling influences life span postulates that decreased GH signaling lowers metabolic rate, thus slowing aging by decreasing production of damaging free radicals. The influence of altered GH signaling on metabolism was tested by monitoring oxygen consumption (VO2), respiratory quotient (RQ), and heat production in long-lived GH receptor knockout (GHRKO) and Ames dwarf mice, and short-lived bovine GH-overexpressing transgenic (bGH TG) mice. Intriguingly, both GHRKO and Ames dwarf mice have increased VO2 and heat per gram body weight, and decreased RQ, whereas bGH TG mice have decreased VO2 and heat per gram body weight and increased RQ. In conclusion, decreased GH signaling associates with increased metabolism per body weight and may beneficially affect mitochondrial flexibility by increasing the capacity for fat oxidation; generally, GH excess produces opposite metabolic effects.

Keywords Metabolism; Altered growth hormone signaling; Thyroid hormone; Oxygen consumption; Respiratory quotient

Received: February 7, 2008; Accepted: December 18, 2008

Decision Editor: Huber R. Warner, PhD


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