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 Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Vozarova, B. Articles by Tataranni, P. A. Search for Related Content PubMed PubMed Citation Articles by Vozarova, B. Articles by Tataranni, P. A.

Effect of Cortisol on Muscle Sympathetic Nerve Activity in Pima Indians and Caucasians

Clinical Diabetes and Nutrition Section (B.V., C.W., P.A.T.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Department of Human Services, Phoenix, Arizona 85016; University of Maryland School of Medicine (S.S.), Department of Medicine, Division of Endocrinology, Diabetes, and Nutrition, Baltimore, Maryland 21210; Service de Diabetologie (J.-F.G.), Hôpital Saint-Louis, 75010 Paris, France; National Institute of Mental Health (G.C.), National Institutes of Health, Bethesda, Maryland; Pediatric and Reproductive Endocrinology Branch (G.C.), National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 70808; and Pennington Medical Research Center (E.R.), Louisiana State University, Baton Rouge, Louisiana 20892

Address all correspondence to: Barbora Vozarova, M.D., Ph.D., Clinical Diabetes and Nutrition Section, National Institutes of Health, 4212 North 16th Street, Room 5-41, Phoenix, Arizona 85016. E-mail: bvozarov{at}mail.nih.gov.

The hypothalamo-pituitary-adrenal axis and sympathetic nervous system (SNS) interact to maintain cardiovascular and metabolic homeostasis, especially during stress. Pima Indians have a low SNS activity, which may contribute to both their increased risk of obesity and reduced risk of hypertension. Although glucocorticoids inhibit SNS activity, Pima Indians are not hypercortisolemic compared with Caucasians. This does not exclude the possibility that the SNS is more responsive to an inhibitory effect of cortisol in the former than in the latter group.

We measured fasting plasma ACTH and cortisol and muscle SNS activity [muscle sympathetic nervous system activity (MSNA), microneurography] in 58 males [27 Pimas/31 Caucasians]. Seven Pimas and 12 Caucasians were randomized to a double-blind, placebo-controlled, cross-over study to examine the effect of overnight partial chemical adrenalectomy (metyrapone) followed by cortisol replacement (hydrocortisone) on plasma ACTH, cortisol, and MSNA.

There were no ethnic differences in fasting plasma ACTH or cortisol, but MSNA adjusted for percent body fat was lower in Pimas than in Caucasians (P < 0.006). No correlation was found between fasting cortisol and basal MSNA. Administration of metyrapone did not lead to significant changes in MSNA. In response to a hydrocortisone infusion, MSNA decreased in Pima Indians (P = 0.03) but not in Caucasians (P = 0.7).

Our data indicate that the low SNS activity that predisposes Pima Indians to obesity is not due to a tonic inhibitory effect of cortisol. However, an acute release of cortisol is likely to more effectively contain sympathoexcitation during stress in Pima Indians than in Caucasians, which may be an important mechanism of cardioprotection in this Native American population.

Abbreviations: DHPG, Dihydroxyphenylglycol; DOPA, dihydroxyphenylalanine; DOPAC, dihydroxyphenyl acetic acid; EPI, epinephrine; HPA, hypothalamo-pituitary adrenal; MSNA, muscle sympathetic nervous system activity; NE, norepinephrine; SNS, sympathetic nervous system.

This article has been cited by other articles:

				N. F. Butte, M. R. Puyau, F. A. Vohra, A. L. Adolph, N. R. Mehta, and I. Zakeri Body Size, Body Composition, and Metabolic Profile Explain Higher Energy Expenditure in Overweight Children J. Nutr., December 1, 2007; 137(12): 2660 - 2667. [Abstract] [Full Text] [PDF]