Obesity is a medical condition that abnormal or excessive fat is accumulated. It is a complex phenotype determined by lifestyle, environmental factors, and genetic factors. Obesity presents a risk to health and is a major risk factor for various diseases, including cardiovascular diseases, type 2 diabetes, obstructive sleep apnea, osteoarthritis, and certain types of cancer. Body mass index (BMI) is the most widely used crude measurement of obesity that obtained by dividing a person’s weight (in kilograms) by the square of his or her height (in metres). Excess of 30 is generally considered obese.
In the past few years, >30 single nucleotide polymorphisms (SNPs) are identified association with BMI, but little is known about DNA methylation related to BMI. DNA methylation often occurs at the 5´ carbon of cytosine in CpG dinucleotides. It plays a critical role in transcriptional regulation of genes and miRNAs, control of alternative promoter usage, and alternative splicing. DNA methylation is affected by both genetic and environmental factors, just like obesity. Is there any correlation between DNA methylation and obesity?
Several scientists undertook a genome-wide analysis of methylation in relation to BMI. They typed European origin 479 individuals’ whole-blood DNA, excluded 20 individuals from analyses after quality control, and then tested methylation levels for association with BMI. They found methylation at three probes in intron 1 of HIF3A (cg22891070, cg27146050, and cg16672562) are in association with BMI. Then, they examined the results in MARTHA cohort and KORA cohort. For the MuTHER cohort, methylation at cg22891070 was related with BMI in adipose tissue.
Meta-analyses of the datasets used in this study provided new insights into epigenetic changes associated with diseases. Increased methylation at the HIF3A locus suggested that perturbation of hypoxia inducible transcription factor pathways could have an important role in mediation of some downstream adverse responses to increased BMI.