Ethnic differences in sympathetic nervous system-mediated energy expenditure

M. F. Saad*, S. A. Alger, F. Zurlo, J. B. Young, C. Bogardus, E. Ravussin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

68 Scopus citations

Abstract

The impact of sympathetic nervous system (SNS) activity on energy expenditure (EE) was evaluated in nondiabetic Caucasian and Pima Indian men while on a weight-maintenance diet using two approaches as follows. 1) The relationship between 24-h EE, measured in a respiratory chamber, and 24-h urinary norepinephrine was studied in 36 Caucasians [32 ± 8 (SD) yr, 95 ± 41 kg, 22 ± 13% fat] and 33 Pimas (29 ± 6 yr, 103 ± 28 kg, 30 ± 9% fat). There was no difference between the two groups in 24-h EE (2,422 vs. 2,523 kcal/24 h) and in urinary norepinephrine (28 vs. 31 μg/24 h), even after adjusting for body size and composition. Twenty-four-hour EE correlated significantly with 24-h urinary norepinephrine in Caucasians (r = 0.78, P < 0.001) but not in Pimas (r = 0.03), independent of fat-free mass (FFM), fat mass, and age. 2) The effect of β-adrenoceptor blockade with propranolol (120 μg/kg FFM bolus and 1.2 μg·kg FFM-1·min-1 for 45 min) on the resting metabolic rate (RMR) was evaluated in 36 Caucasians (30 ± 6 yr, 103 ± 36 kg, 25 ± 11% fat) and 32 Pimas (28 ± 6 yr, 100 ± 34 kg, 27 ± 10% fat). The RMR was similar in the two groups (2,052 vs. 1,973 kcal/24 h) even after adjustment for FFM, fat mass, and age and dropped significantly after propranolol infusion in Caucasians (-3.9%, P < 0.001) but not in Pimas (-0.8%, P = 0.07). The decrease in RMR correlated significantly with the RMR (adjusted for FFM, fat mass, and age) before propranolol infusion in Caucasians (r = -0.57, P < 0.001) but not in Pimas (r = -0.18, P = 0.35). In conclusion, SNS activity is a determinant of EE in Caucasian but not in Pima Indian men.

Original languageEnglish (US)
Pages (from-to)E789-E794
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume261
Issue number6 24-6
DOIs
StatePublished - Jan 1 1991

Keywords

  • Catecholamines
  • Pima Indians
  • Resting metabolic rate

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Physiology
  • Physiology (medical)

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