Aging resting metabolic rate

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J Gerontol A Biol Sci Med Sci. Author manuscript; available in PMC 2009 June 8.
Published in final edited form as: J Gerontol A Biol Sci Med Sci. 2007 July ; 62(7): 752–759.

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Aging, Resting Metabolic Rate, and Oxidative Damage: Results From the Louisiana Healthy Aging StudyMadlyn I. Frisard1, Amanda Broussard1, Sean S. Davies2, L. Jackson Roberts II2, Jennifer Rood1, Lillian de Jonge1, Xiaobing Fang1, S. Michal Jazwinski1, Walter A. Deutsch1, and Eric Ravussin [on behalf of for the Louisiana Healthy Aging Study]1 1Pennington Biomedical Research Center, Baton Rouge, Louisiana. 2Vanderbilt University, Nashville, Tennessee.

Abstract
Background—The aging process occursat variable rates both among and within species and may be related to the variability in oxygen consumption and free radical production impacting oxidative stress. The current study was designed to test whether nonagenarians have a relatively low metabolic rate and whether it is associated with low levels of oxidative stress relative to age. Methods—Resting metabolic rate (RMR) and markers ofoxidative stress to lipids, proteins, and DNA were measured in three groups of individuals aged 20–34 (n = 47), 60–74 (n = 49), and ≥90 years (n = 74). Results—RMR, adjusted for fat-free mass, fat mass, and sex, was lower in both older groups when compared to the young group (p ≤ .0001). There were no significant differences in urinary isoprostanes, serum protein carbonyls, or DNA fragmentationbetween groups, and RMR was not related to any markers of oxidative stress. Conclusions—This study confirms an age-related decline in RMR independent of changes in body composition but surprisingly did not show an accumulation of oxidative damage with increasing age. Our data challenge the theory that RMR is a significant determinant of oxidative stress and therefore contributes to the aging process.There are currently more than 300 theories attempting to explain the aging process (1). However, there is still no agreement regarding the causes or mechanisms of biological aging. Two complementary, closely related theories are the Rate of Living Theory and the Free Radical/Oxidative Stress Hypothesis of Aging. Combined, these theories state that free radicals produced during cellular metabolismreact with biomolecules to produce oxidative damage, which accumulates with age (2,3). There is support for both of these theories. For example, free radical production and metabolic rate are inversely related to life span (4,5). However, there is a discrepancy in the results between intra- and interspecies animal models (2,5–7). In addition, it is now well known that free radicals have importantroles in various physiological functions (8). It appears that only when free radicals are in excess (excessive production and/ or insufficient removal), can they accumulate and cause damage to cells and tissue contributing to disease and the aging process (8). However, it is unknown if there is a relationship between resting metabolic rate (RMR) and oxidative stress in humans and whether these arerelated to the aging process.

Copyright 2007 by The Gerontological Society of America CORRESPONDENCE, Address correspondence to Eric Ravussin, PhD, Pennington Biomedical Research Center, 6400 Perkins Rd., Baton Rouge, LA 70808. E-mail: E-mail: ravusse@pbrc.edu.

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Reactions with oxygen can produce a number of free radicals known as reactive oxygen species (ROS)(9–12). ROS attack lipids, proteins, and DNA generating a number of products that affect normal cell functioning (13–15). However, organisms have adapted a number of mechanisms to protect from free radical production (10,16). The function of many proteins, such as antioxidant enzymes, includes removing free radicals from cells and tissues (11). Recently, uncoupling proteins (UCPs) have been shown to...