Human Integrative Physiology - Michael J. Joyner

Effects of Bariatric Surgery on Sympathetic Neural Control Mechanisms in Humans

Timothy B. Curry, M.D. , Ph.D.

IRB #:06-006709

The role of the autonomic nervous system in obesity is controversial but it has been shown that there is an increase in chronic, resting levels of sympathetic neural activity (SNA) in obesity. SNA has been shown to be reduced by weight loss induced by dieting and exercise, but the effect of bariatric surgery on SNA has not been studied using direct measurements.

In this protocol, we will be performing a cross-sectional study of the effects of bariatric surgery on

• chronic baseline levels of sympathetic activity (measured as muscle SNA and plasma catecholamines)
• the integrative control of sympathetic activity, including its reflex control (baro- and metaboreflexes) and neuroendocrine control (renin, aldosterone, leptin and insulin levels)
• the physiological effects of sympathetic activation (cardiac output, heart rate variability, forearm blood flow, and energy expenditure)

Three groups of subjects (N=42 total) will be studied at the Clinical Research Unit at Mayo Clinic, Rochester, MN: (1) subjects who are >12 months post-bariatric surgery (2) subjects who are obese and (3) subjects who are normal weight. We hypothesize that bariatric surgery will result in a decrease in chronic resting levels of MSNA and associated increases in reflex sympathetic neural responsiveness and physiological responses to sympathetic stimulation.