EFFECTS OF AGE AND PHYSICAL ACTIVITY LEVEL ON RESTING METABOLIC RATE AND SYMPATHETIC NERVOUS SYSTEM ACTIVITY

Abstract Background Interindividual variability in 24-hour energy expenditure (24EE) during energy-balance conditions is mainly determined by differences in body composition and demographic factors. Previous studies suggested that 24EE might also be influenced by sympathetic nervous system activity via catecholamine (norepinephrine, epinephrine) secretion. Therefore, we analyzed the association between catecholamines and energy expenditure in 202 individuals from a heterogeneous population of mixed ethnicities. Methods Participants (n = 202, 33% female, 14% black, 32% white, 41% Native American, 11% Hispanic, age: 36.9 ± 10.3 y [mean ± SD], percentage body fat: 30.3 ± 9.4) resided in a whole-room calorimeter over 24 hours during carefully controlled energy-balance conditions to measure 24EE and its components: sleeping metabolic rate (SMR), awake-fed thermogenesis (AFT), and spontaneous physical activity (SPA). Urine samples were collected, and 24-h urinary epinephrine and norepinephrine excretion rates were assessed by high-performance liquid chromatography. Results Both catecholamines were associated with 24EE and SMR (norepinephrine: +27 and +19 kcal/d per 10 μg/24h; epinephrine: +18 and +10 kcal/d per 1 μg/24h) in separate analyses after adjustment for age, sex, ethnicity, fat mass, fat-free mass, calorimeter room, temperature, and physical activity. In a multivariate model including both norepinephrine and epinephrine, only norepinephrine was independently associated with both 24EE and SMR (both P < .008), whereas epinephrine became insignificant. Neither epinephrine nor norepinephrine were associated with adjusted AFT (both P = .37) but epinephrine was associated with adjusted SPA (+0.5% per 1 μg/24h). Conclusions Our data provide compelling evidence that sympathetic nervous system activity, mediated via norepinephrine, is a determinant of human energy expenditure during nonstressed, eucaloric conditions.

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EXERCISE TRAINING AND SYMPATHETIC NERVOUS SYSTEM ACTIVITY: EVIDENCE FOR PHYSICAL ACTIVITY DEPENDENT NEURAL PLASTICITY

Clinical and Experimental Pharmacology and Physiology ◽

10.1111/j.1440-1681.2007.04590.x ◽

2007 ◽

Vol 34 (4) ◽

pp. 377-384 ◽

Cited By ~ 117

Author(s):

Patrick J Mueller

Keyword(s):

Physical Activity ◽

Nervous System ◽

Exercise Training ◽

Sympathetic Nervous System ◽

Neural Plasticity ◽

Sympathetic Nervous System Activity ◽

System Activity ◽

Nervous System Activity ◽

Sympathetic Nervous ◽

Activity Dependent

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Physical Activity and Sympathetic Nervous System Activity

Physical Activity and Obesity ◽

10.5040/9781492595731.ch-035 ◽

2015 ◽

Author(s):

Ian A. Macdonald

Keyword(s):

Physical Activity ◽

Nervous System ◽

Sympathetic Nervous System ◽

Sympathetic Nervous System Activity ◽

System Activity ◽

Nervous System Activity ◽

Sympathetic Nervous

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Chemical sympathectomy alters regulation of body weight during prolonged ICV leptin infusion

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00128.2002 ◽

2003 ◽

Vol 284 (4) ◽

pp. E778-E787 ◽

Cited By ~ 23

Author(s):

Robert L. Dobbins ◽

Lidia S. Szczepaniak ◽

Weiguo Zhang ◽

J. Denis McGarry

Keyword(s):

Physical Activity ◽

Nervous System ◽

Body Weight ◽

Food Intake ◽

Energy Expenditure ◽

Sympathetic Nervous System ◽

Metabolic Rate ◽

Resting Metabolic Rate ◽

Chemical Sympathectomy ◽

Sympathetic Nervous

To assess the importance of the sympathetic nervous system in regulating body weight during prolonged leptin infusion, we evaluated food intake, body weight, and physical activity in conscious, unrestrained rats. Initial studies illustrated that prolonged intracerebroventricular (ICV) infusion of leptin enhanced substrate oxidation so that adipose tissue lipid stores were completely ablated, and muscle triglyceride and liver glycogen stores were depleted. After neonatal chemical sympathectomy, changes in weight and food intake were compared in groups of sympathectomized (SYM) and control (CON) adult animals during ICV infusion of leptin. CON animals lost 60 ± 9 g over 10 days vs. 25 ± 3 g in the SYM animals when food intake was matched between the two groups. Greater weight loss despite similar energy intake points to an important role of the sympathetic nervous system in stimulating energy expenditure during ICV leptin infusion by increasing the resting metabolic rate, since no differences in physical activity were observed between CON and SYM groups. In conclusion, activation of the SNS by leptin increases energy expenditure by augmenting the resting metabolic rate.

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