Abstract 13780: JNK Inhibition Mimics the Beneficial Effect of Roux-en-Y Gastric Bypass Surgery on Obesity-Induced Endothelial Dysfunction

Abstract

Introduction: Roux-en-Y gastric bypass surgery (RYGB) reduces weight and long-term cardiovascular risk in obese patients. We previously demonstrated that in diet-induced obese rats RYGB improves aortic endothelial vasorelaxation 8 days after surgery in a weight loss-independent manner. Improved endothelial function was associated with decreased JNK phosphorylation and increased Akt and eNOS phosphorylation in the aorta. Hypothesis: We investigated whether in vivo inhibition of JNK activity in sham-operated ad libitum-fed rats mimics these endothelial effects of RYGB. Methods: Male Wistar rats were fed a high fat (60%) high cholesterol (1.25%) diet for 7 weeks before undergoing either RYGB or sham surgery; sham-operated rats received vehicle (sham_AL) or the JNK-specific inhibitor SP600125 40mg/kg/day s.c. for 8 days post-surgery (sham_SP). Then, thoracic aortic rings were isolated and subjected to ex vivo isometric tension recordings. After submaximal contraction with norepinephrine (10-6mol/L), cumulative relaxation responses were performed to GLP-1 (7-36) amide (10-12 to 10-6mol/L) or insulin (10-12 to 10-5mol/L); tests were repeated after preincubation with the eNOS inhibitor L-NAME (10-4mol/L). Western blot analysis of JNK, Akt and eNOS was also performed on aortic tissue lysates. Results: Body weight did not differ between sham_SP and sham_AL rats, while the weight loss of RYGB rats was significant 8 days after surgery. GLP-1- and insulin-induced vasorelaxation responses improved in RYGB compared to sham_AL rats; interestingly, sham_SP rats had endothelial relaxation similar to RYGB rats. All responses were blocked by preincubation with L-NAME, suggesting an eNOS-dependent effect. JNK protein phosphorylation in aortic lysates was decreased in RYGB and sham_SP rats compared to sham_AL, while Akt phosphorylation was increased. eNOS phosphorylation and dimerization were also increased in RYGB and sham_SP compared to sham_AL rats. Conclusion: JNK inhibition seems to mimic the immediate eNOS-mediated endothelial protective effects of RYGB. Further, our study underlines a crucial role of JNK in obesity-associated endothelial dysfunction, suggesting a novel mechanism for the cardiovascular effects of RYGB.