Sympathetic nervous system activity after gastric bypass surgery

Abstract

The effect of gastric bypass surgery (GBS) on MSNA and the relationship between MSNA and NE in these individuals has not been well described. We measured MSNA in subjects who were 38±5 months post surgery (GBS, BMI= 28±0.8 kg/m2, N=10) and in lean (L, BMI= 23±0.4 kg/m2, N=13), and obese (O, BMI= 39±1.0 kg/m2, N=13) control subjects. MSNA (bursts/min) trended to be lower in GBS (15.0±3.2) and L (17.2±3.2) compared with O (24.3±2.8), although this difference was not significant (P=0.08). Similarly, there was trend for NE to be lower in GBS (88.9±31.9) compared with both L (180.1±28.0) and O (182.3±28.0) but again this was not significant (P=0.06). A weak relationship was present between NE and MSNA for all subjects (R2=0.15, P<0.05). There was a trend for this relationship to be stronger in L (R2=0.40, P=0.07) and also O (R2=0.32, P=0.06) but there was clearly no relationship in GBS (R2=0.03, P=0.63). This preliminary data indicates that a reduction in sympathetic activity probably occurs after GBS. This is likely due to weight loss as MSNA was significantly related to weight (R2=0.22, P<0.01). However, the relationship between MSNA and NE is not present after GBS due to markedly lower NE levels. Based on this preliminary data it does not appear that plasma NE should be used a measure of sympathetic activity after GBS. Supported by Mayo Clinic and NIH Grant Numbers K23 DK82424 (TC) and UL1 RR024150 (Mayo Clinic).