Metabolic and autonomic nervous system effects of bariatric surgery

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Despite avid attempts, non-surgical methods such as diet aids, behavioral modification and exercise are typically unsuccessful in achieving long term weight loss in the obese. However, bariatric surgery maintains a 65 percent success rate making it the most effective means of sustained weight loss. A primary metabolic impairment with obesity is insulin resistance (IR), which has been shown to be associated with impaired cardiac autonomic function. Recent studies have indicated that there are marked improvements in IR, within days of bariatric surgery even before significant weight loss occurs. On the other hand, cardiac autonomic function has not been studied immediately after bariatric surgery, although improvements in autonomic function have been demonstrated at later time points (i.e., 6 to 12 months post surgery) when significant weight loss has occurred. Moreover, the relationship between IR and cardiac autonomic function has not been explored following surgically-induced weight loss. Therefore, we hypothesized that a minimal weight reduction induced by bariatric surgery will produce restoration of cardiac autonomic control associated with improvements in IR. We tested six morbidly obese subjects (42±3 years) before and one month after Rouxen- Y Gastric Bypass surgery. Our findings suggest that despite marked reductions in body weight (158±15 pre vs. 139±12 post Kg; P=0.001) and improvements in insulin resistance (7.2±1.4 pre vs. 5.1±0.9 post; P=0.038) one month following bariatric surgery, cardiac autonomic function and baroreflex sensitivity are unaltered. Therefore, there was no significant short term effect of bariatric surgery on cardiac autonomic control.