High-fat diet leads to a decreased methylation of theMc4r gene in the obese BFMI and the lean B6 mouse lines

Abstract

The melanocortin-4 receptor (Mc4r) plays an important role in body-weight regulation. This study examines the methylation status and expression levels of theMc4r gene in response to a standard and a high-fat diet in the obese Berlin fat mouse inbred (BFMI) line and the lean C57BL/6NCrl (B6) line ofMus musculus. The methylation status of CpG sites located within theMc4r exon was analyzed by bisulfite genomic sequencing of genomic DNA of brain tissues, and gene expression analysis was performed by real-time PCR. In both lines, the methylation of CpGs 1–8 (near the transcription start) was lower than methylation of CpGs 9–16 (located towards the end of the selected amplicon). On the standard diet, the methylation status did not differ between the lines. In response to high-fat diet, methylation of the CpGs near the transcription start was decreased in both lines. TheMc4r gene expression, however, was only marginally increased in BMFI mice, whereas there was no change in B6 mice. The results suggest that a long-term high-fat diet might have an effect on the methylation status of theMc4r gene. However, the effect of methylation onMc4r expression seems to be a variable compensated by other regulating factors in a line-specific manner.