Assessment of global long interspersed nucleotide element-1 (LINE-1) DNA methylation in a longitudinal cohort of type 2 diabetes mellitus (T2DM) individuals.

Introduction: Recent studies have indicated that methylation of the LINE-1 elements is associated with an increased risk of worsening carbohydrate metabolism. It has been shown that overall DNA methylation of LINE-1 elements could be considered as a risk factor for T2DM and its complications, independent of other established risk factors.

Methods: A total of 794 T2DM individuals from Salford, UK were included in this study (60% men n = 470). All patients had clinical and metabolic variables measured in 2002 (baseline outcomes) and annually through to 2016. Global LINE-1 DNA methylation was measured at four CpG sites. The QIAGEN PyroMark Q96 MD pyrosequencer was used to quantify methylation.

Results: The overall mean ± SD global LINE-1 methylation was 75.81 ± 3.25%. Cross-sectional linear regression analysis at baseline year 2002 showed that LINE-1 methylation was a significant predictor of diastolic BP (adjusted beta coefficient β = -0.25), estimated glomerular filtration rate (eGFR) (β = -0.48) and cholesterol HDL ratio (β = -0.04). A 10% increase in LINE-1 methylation was associated with a lower diastolic BP by 2.5 mm Hg, a lower eGFR by 4.8 ml/min/1.73 m and decreased cholesterol/HDL ratio by 0.4 mmol/L. Longitudinal analysis over the 14-year-follow-up periods showed that global LINE-1 methylation at baseline was associated with lower BMI in women [β = -0.25] and lower cholesterol: HDL ratio [β = -0.07]. A 10% increase in LINE-1 methylation was associated with reduction in BMI by 2.5 kg/m in women and reduction in cholesterol:HDL ratio by 0.7 mmol/L.

Conclusion: In a 14-year longitudinal cohort of T2DM individuals, relations between global LINE-1 DNA methylation status and specific metabolic markers were seen. Also, a higher degree of DNA methylation was predictive of less weight gain over time in women.