Correlation of methylation of toll-like receptor 4 (TLR4) and interleukin-6 (IL6) promoter with insulin resistance in obese adolescents

ABSTRACT: Chronic inflammation can lead to insulin resistance in obesity. Increased mRNA expression of inflammatory markers such as toll-like receptor 4 (TLR4) and interleukin 6 (IL6) were reported both in the tissue and the peripheral blood of obese adolescent and correlated with insulin resistance. DNA methylation surrounding TSS region is known to regulate thelevel of a gene expression. The aim of the study was to investigate the methylation status of TLR4 and IL6 promoter in peripheral blood of obese adolescent and its correlation to insulin resistance. This was a cross sectional study with observational analytic approached. Fifty adolescents with obesity from Yogyakarta Special Region, aged 15-18 years, z-score value >2 SD, no experience of any acute infections within 2 weeks and signed in informed consent, were selected in this study. Subjects with diabetic mellitus, incompletedata and DNA concentration of <20 µg/mL were excluded. DNA samples were extracted from peripheral blood of the subjects. The bisulfte converted DNA was analyzed for methylation level with direct sequencing. Correlation analysis using Spearman test was performed with signifcance value was set at p<0.05. No methylation in TLR4 promoter was detected in all subjects. The methylation level of IL6 was transformed to categorical variable. Four (8%) subjects with insulin resistance and 2 (4%) without insulin resistancehad methylation on a CpG site. Methylation of IL6 was not statisticaly different between insulin resistance and non-resistance adolescent (p=0.635). The signifcant correlationwas not found between methylation level in IL6 promoter with insulin resistance (HOMAIR) (r=0.051). Cell specifc of methylation mechanism, characteristic of subjects and types of samples were suspected causing those results. In conclusion, no correlation between methylation levels of TLR4 promoter and IL6 with insulin resistance in obese adolescent was observed in this study.
Keywords: obesity – methylation - TLR4 - IL6 - direct sequencing
Author: Ratih Feraritra Danu Atmaja, Dian Caturini Sulistyonigrum, Emy Huriyati, Ahmad Hamim Sadewa, Rina Susilowati
Journal Code: jpkedokterangg160179