Reactivation of adiponectin expression in obese patients after bariatric surgery

Bariatric surgery can resolve type 2 diabetes in morbidly obese patients. However, the underlying mechanism is unknown. This study aimed to identify potential biomarkers or molecular pathways that are altered after bariatric surgery in diabetic and nondiabetic patients.

The study enrolled 17 morbidly obese patients undergoing bariatric surgery. Eight of the patients were diabetic, and nine were nondiabetic. In addition, a control group of four nonobese, nondiabetic volunteers was included. Patient blood samples were drawn before and after the operation. All blood samples were stabilized in Paxgene tubes (PreAnalytix). Total RNA was extracted and purified using the Paxgene Blood RNA Kit. For each sample, 100 ng of total RNA was amplified and labeled using the Ovation RNA Amplification System V2 with the Ovation Whole Blood reagent before hybridization to an Affymetrix Focus array containing more than 8,500 verified genes. Microarray results were analyzed with the GeneSpring GX 10.0 program, which uses an analysis of variance (ANOVA), and verified with real-time quantitative polymerase chain reaction (QPCR) using SYBR green (ABI).

Microarray analysis showed that 167 genes were upregulated and 39 were downregulated in the obese diabetic patients. Preoperatively, adiponectin was downregulated 1.5-fold in diabetic versus nondiabetic patients. This was confirmed with quantitative PCR analysis. Preoperatively, morbidly obese patients showed a 3.12-fold downregulation of adiponectin expression versus the control group (p = 0.05). Interestingly, postoperative adiponectin levels were upregulated 2.79-fold (p = 0.02), which is close to the level of the normal control group.

Adiponectin is dysregulated in obese patients and significantly dysregulated in obese diabetic patients. These findings correlate with the association between low levels of adiponectin and a predisposition to insulin resistance or diabetes. The data suggest that reactivation of adiponectin expression may play a part in the resolution of type 2 diabetes after bariatric surgery. Therefore, targeting adiponectin may help to develop alternative treatments for diabetes.