No effect of different bariatric surgery procedures on LINE-1 DNA methylation in diabetic and nondiabetic morbidly obese patients

Abstract

Background: Bariatric surgery (BS) is proposed as a highly effective therapy for reducing weight and improving obesity-related co-morbidities. The molecular mechanisms involved in the metabolic improvement after BS are not completely resolved. Epigenetic modifications could have an important role.

Objective: The aim of this study was to evaluate the effect of different BS procedures (Roux-en-Y gastric bypass and laparoscopic sleeve gastrectomy) on global DNA methylation (long interspersed nucleotide element 1 [LINE-1]) in a group of nondiabetic and diabetic severely obese patients.

Setting: University hospital, Spain.

Methods: This study included 60 patients (30 nondiabetic and 30 diabetic severely obese patients) undergoing BS: 31 patients underwent Roux-en-Y gastric bypass and 29 underwent laparoscopic sleeve gastrectomy. Before and 6 months post-BS, anthropometric data, blood pressure, and metabolic parameters were determined. LINE-1 DNA methylation was quantified by pyrosequencing. We used the methylation levels of tumor necrosis factor-α as a control gene promoter.

Results: There were no differences between LINE-1 methylation levels at baseline and at 6 months after surgery (66.3±1.6 versus 66.2±2.06). Likewise, there was no statistically significant difference on LINE-1 methylation levels when we stratified according to metabolic status (diabetic versus nondiabetic), nor was there regarding the BS procedure. A strong correlation was shown between LINE-1 methylation levels and weight at baseline both in diabetic and nondiabetic obese patients (r = .486; P<.001). Tumor necrosis factor-α methylation levels increased significantly after BS in the group of diabetic obese patients.

Conclusion: After BS, global LINE-1 methylation is not modified in the short term. More studies are required to determine if LINE-1 is a stable epigenetic marker, or, on the contrary, if it is susceptible to modification by external factors such as changes in lifestyle or a surgical intervention.

Keywords: Bariatric surgery; Diabetes; Global DNA methylation; LINE-1 levels; Severe obesity.