The Effect of Bariatric Surgery on Neprilysin and Vasoactive Factors

Objective: Since morbid obesity is associated with congestive cardiac failure and hypertension, and gastric bypass surgery is followed by a reduction in blood pressure and a reduction in the risk of congestive cardiac failure, we hypothesized that weight loss following bariatric surgery in morbidly obese patients is associated with a decrease in plasma concentrations of neprilysin, mediators of renin angiotensin system, catecholamines and endothelin-1 with an increase in the concentrations of vasodilators.

Method: Fasting blood samples were obtained from fourteen patients with morbid obesity and diabetes prior to and 6 months after Roux-en-Y gastric bypass (RYGB) surgery. Plasma and serum were separated for the measurement of neprilysin; vasoconstrictors, angiotensinogen, renin, angiotensin II, endothelin-1, epinephrine and norepinephrine; and vasodilators, ANP, BNP, cGMP, and cAMP. The mRNA expression of angiotensin converting enzyme (ACE) and adenylate and guanylate cyclases in circulating mononuclear cells (MNC) was also measured.

Results: Six months after RYGB, BMI fell from 52.1±4.8 to 40.4±4.0 kg/m² and there were significant improvements in the HbA₁c. Plasma concentrations of neprilysin, angiotensinogen, angiotensin II, renin and endothelin-1 fell significantly by 27±16%, 22±10% 22±8%, 35±13% and 17±6% (p<0.for all) respectively, while ANP concentrations increased significantly by 24±13% at 6 month following surgery. There was no significant change in aldosterone, BNP, cAMP or cGMP concentrations and ACE mRNA expression.

Conclusion: RYGB suppressed neprilysin concentrations, which may contribute the observed increase in plasma ANP concentrations. In addition, RYGB resulted in a reduction in plasma angiotensinogen, angiotensin II, renin and endothelin-1 concentrations. These changes may contribute to the reduction in the risk of congestive cardiac failure and blood pressure after RYGB.