LINE-1 methylation in visceral adipose tissue of severely obese individuals is associated with metabolic syndrome status and related phenotypes

Background: Epigenetic mechanisms may be involved in the regulation of genes found to be differentially expressed in the visceral adipose tissue (VAT) of severely obese subjects with (MetS+) versus without (MetS-) metabolic syndrome (MetS). Long interspersed nuclear element 1 (LINE-1) elements DNA methylation levels (% meth) in blood, a marker of global DNA methylation, have recently been associated with fasting glucose, blood lipids, heart diseases and stroke. Aim: To test whether LINE-1% meth levels in VAT are associated with MetS phenotypes and whether they can predict MetS risk in severely obese individuals. Methods: DNA was extracted from VAT of 34 men (MetS-: n = 14, MetS+: n = 20) and 152 premenopausal women (MetS-: n = 84; MetS+: n = 68) undergoing biliopancreatic diversion for the treatment of obesity. LINE-1% meth levels were assessed by pyrosequencing of sodium bisulfite-treated DNA. Results: The mean LINE-1% meth in VAT was of 75.8% (SD = 3.0%). Multiple linear regression analyses revealed that LINE-1% meth was negatively associated with fasting glucose levels (beta = -0.04; P = 0.03), diastolic blood pressure (beta = -0.65; P = 0.03) and MetS status (beta = -0.04; P = 0.004) after adjustments for the effects of age, sex, waist circumference (except for MetS status) and smoking. While dividing subjects into quartiles based on their LINE-1% meth (Q1 to Q4: lower % meth to higher % meth levels), greater risk were observed in the first (Q1: odds ratio (OR) = 4.37, P = 0.004) and the second (Q2: OR = 4.76, P = 0.002) quartiles compared to Q4 (1.00) when adjusting for age, sex and smoking. Conclusions: These results suggest that lower global DNA methylation, assessed by LINE-1 repetitive elements methylation analysis, would be associated with a greater risk for MetS in the presence of obesity.