Gastric Bypass Surgery Improves the Skeletal Muscle Ceramide/S1P Ratio and Upregulates the AMPK/ SIRT1/ PGC-1α Pathway in Zucker Diabetic Fatty Rats

Purpose Roux-en-Y gastric bypass (RYGB) is associated with remission of type 2 diabetes. However, the cellular and molecular mechanisms remain unknown. We hypothesized that RYGB would increase peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1 alpha), sirtuin-1 (SIRT1), AMPK/pAMPK, and citrate synthase (CS) protein expression and decrease insulin resistance and these changes would bemediated by sphingolipids, including ceramides and the sphingolipid metabolite sphingosine-1 phosphate (S1P). Materials and Methods Male ZDF rats were randomized to RYGB (n = 7) or sham surgery (n = 7) and harvested after 28 days. Total tissue ceramide, ceramide subspecies (C14:0, C16:0, C18:0, C18:1, C20:0, C24:0, and C24:1), and S1P were quantified in the white gastrocnemius muscle using LC-ESI-MS/MS after separation with HPLC. Total SIRT1, AMPK, PGC-1 alpha, and CS protein expression were measured by Western blot. Results Body weight, fasting glucose, insulin, and HOMA-IR decreased significantly after RYGB compared with sham control. These changes were paralleled by lower total ceramide (483.7 +/- 32.3 vs. 280.1 +/- 38.8 nmol/g wwt), C18:0 ceramide subspecies (P < 0.05), higher S1P (0.83 +/- 0.05 vs. 1.54 +/- 0.21 nmol/g wwt, P < 0.05), and a lower ceramide/S1P ratio (P < 0.05) in the RYGB versus sham group. AMPK, pAMPK, SIRT1, PGC-1 alpha, and CS protein expression was also higher after RYGB (P < 0.05). The ceramide/S1P ratio correlated with weight loss (r = 0.48, P = 0.08), insulin resistance (r = 0.61, P = 0.02), PGC-1 alpha (r = -0.51, P < 0.06), CS (r = -0.63, P = 0.01), and SIRT1 (r = -0.54, P < 0.04). Conclusion Our data demonstrate that sphingolipid balance, and increased AMPK, SIRT1, PGC-1 alpha, and CS protein expression are part of the mechanism that contributes to the remission of diabetes after RYGB surgery.