Ethnic differences in sympathetic nervous system-mediated energy expenditure.
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 micrograms/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 less than 0.001) but not in Pimas (r = 0.03), independent of fat-free mass (FFM), fat mass, and age. 2) The effect of beta-adrenoceptor blockade with propranolol (120 micrograms/kg FFM bolus and 1.2 micrograms.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 less than 0.001) but not in Pimas (-0.8%, P = 0.07).(ABSTRACT TRUNCATED AT 250 WORDS)
Saad
M F
MF
Phoenix Epidemiology and Clinical Research Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Arizona 85014.
Alger
S A
SA
Zurlo
F
F
Young
J B
JB
Bogardus
C
C
Ravussin
E
E
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000328:Adult; D001481:Basal Metabolism / Q000187:drug effects; D004734:Energy Metabolism; D005215:Fasting; D006801:Humans; D007198:Indians, North American; D008297:Male; D009638:Norepinephrine / Q000652:urine; D009765:Obesity / Q000208:ethnology / Q000378:metabolism; D011433:Propranolol / Q000494:pharmacology; D013564:Sympathetic Nervous System / Q000378:metabolism*; D044465:White People
D000319:Adrenergic beta-Antagonists; D011433:Propranolol; D009638:Norepinephrine