This Article Full Text Full Text (PDF) Submit a related Letter to the Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints, Permissions and Rights Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Bell, C. Articles by Seals, D. R. Search for Related Content PubMed PubMed Citation Articles by Bell, C. Articles by Seals, D. R.

Oxidative Stress Does Not Modulate Metabolic Rate or Skeletal Muscle Sympathetic Activity with Primary Aging in Adult Humans

Department of Integrative Physiology (C.B., P.P.J., D.R.S.), University of Colorado, Boulder, Colorado 80309-0354; and Department of Medicine (D.R.S.), University of Colorado Health Sciences Center, Denver, Colorado 80262

Address all correspondence and requests for reprints to: Christopher Bell, Ph.D., Department of Integrative Physiology, 354UCB, University of Colorado, Boulder, Colorado 80309-0354. E-mail: Christopher.Bell{at}Colorado.edu.

Support of resting metabolic rate (RMR) by the ß-adrenergic receptors of the sympathetic nervous system is attenuated with age and contributes to declines in RMR. This may be mediated by an age-associated increase in oxidative stress that can suppress ß-adrenergic responsiveness and/or modulate sympathetic activity. To address these issues, RMR was determined in 12 young (23 ± 1 yr, mean ± SE) and 21 older (68 ± 3 yr) adults before and during systemic infusion of ascorbic acid [bolus, 0.06 g/kg fat free mass (FFM); drip, 0.02]. Ascorbic acid increased plasma concentrations similarly in young (72 ± 5 to 1107 ± 114 µmol/liter) and older (70 ± 6 to 1022 ± 63 µmol/liter) adults, and reduced (P = 0.001) plasma concentrations of isoprostanes (young, -82.8 ± 47; older, -107 ± 29 pg/ml). Baseline RMR_FFM was lower (5719 ± 215 vs. 6703 ± 328 kJ/d; P = 0.001) and muscle sympathetic nerve activity (MSNA) was greater (MSNA, 28 ± 2 vs. 23 ± 3 bursts/min; P < 0.05) in older compared with young. However, neither RMR_FFM (young, +117 ± 63; older, +163 ± 48 kJ/d; P = 0.14) or MSNA (young, 0 ± 2; older, -1 ± 1 bursts/min; P = 0.71) changed in either age group during ascorbic acid infusion compared with saline control. These results indicate that increased oxidative stress: 1) is not a mechanism contributing to decreases in RMR with primary aging; and 2) does not modulate MSNA in healthy adult humans.

This research was supported by NIH Grants AG06537, AG00828, 1 P30 DK48520, and AHA 0225438Z.

Abbreviations: ß-AR, ß-Adrenergic receptor; ECG, electrocardiogram; FFM, fat free mass; MSNA, muscle sympathetic nerve activity; RMR, resting metabolic rate.

This article has been cited by other articles:

				K. L. Jablonski, D. R. Seals, I. Eskurza, K. D. Monahan, and A. J. Donato High-dose ascorbic acid infusion abolishes chronic vasoconstriction and restores resting leg blood flow in healthy older men J Appl Physiol, November 1, 2007; 103(5): 1715 - 1721. [Abstract] [Full Text] [PDF]

				K. L. Moreau, A. R. DePaulis, K. M. Gavin, and D. R. Seals Oxidative stress contributes to chronic leg vasoconstriction in estrogen-deficient postmenopausal women J Appl Physiol, March 1, 2007; 102(3): 890 - 895. [Abstract] [Full Text] [PDF]

				C. Bell, N. R. Stob, and D. R. Seals Thermogenic responsiveness to nonspecific beta-adrenergic stimulation is not related to genetic variation in codon 16 of the beta2-adrenergic receptor Am J Physiol Endocrinol Metab, April 1, 2006; 290(4): E703 - E707. [Abstract] [Full Text] [PDF]

				C. Bell, N. R. Stob, and D. R. Seals Thermogenic responsiveness to {beta}-adrenergic stimulation is augmented in exercising versus sedentary adults: role of oxidative stress J. Physiol., February 1, 2006; 570(3): 629 - 635. [Abstract] [Full Text] [PDF]

				K. L. Moreau, K. M. Gavin, A. E. Plum, and D. R. Seals Ascorbic Acid Selectively Improves Large Elastic Artery Compliance in Postmenopausal Women Hypertension, June 1, 2005; 45(6): 1107 - 1112. [Abstract] [Full Text] [PDF]

				C. Bell, J. M. Carson, N. W. Motte, and D. R. Seals Ascorbic acid does not affect the age-associated reduction in maximal cardiac output and oxygen consumption in healthy adults J Appl Physiol, March 1, 2005; 98(3): 845 - 849. [Abstract] [Full Text] [PDF]

				C. Bell, D. S. Day, P. P. Jones, D. D. Christou, D. S. Petitt, K. Osterberg, C. L. Melby, and D. R. Seals High Energy Flux Mediates the Tonically Augmented {beta}-Adrenergic Support of Resting Metabolic Rate in Habitually Exercising Older Adults J. Clin. Endocrinol. Metab., July 1, 2004; 89(7): 3573 - 3578. [Abstract] [Full Text] [PDF]

				I. Eskurza, K. D. Monahan, J. A. Robinson, and D. R. Seals Effect of acute and chronic ascorbic acid on flow-mediated dilatation with sedentary and physically active human ageing J. Physiol., April 1, 2004; 556(1): 315 - 324. [Abstract] [Full Text] [PDF]