Prolonged high-fat diet induces gradual and fat depot-specific DNA methylation changes in adult mice

Abstract

High-fat diets (HFD) are thought to contribute to the development of metabolism-related diseases. The long-term impact of HFD may be mediated by epigenetic mechanisms, and indeed, HFD has been reported to induce DNA methylation changes in white adipose tissue (WAT) near metabolism related genes. However, previous studies were limited to a single WAT depot, a single time-point and primarily examined the pre-pubertal period. To define dynamic DNA methylation patterns specific for WAT depots, we investigated DNA methylation of Pparg2 and Leptin in gonadal adipose tissue (GAT) and subcutaneous adipose tissue (SAT), at baseline and after 6, 12 and 24 weeks of HFD exposure in adult mice. HFD induced hypermethylation of both the Leptin promoter (max. 19.6% at week 24, P = 2.6·10^-3) and the Pparg2 promoter in GAT (max. 10.5% at week 12, P = 0.001). The differential methylation was independent of immune cell infiltration upon HFD exposure. In contrast, no differential methylation in the Pparg2 and Leptin promoter was observed in SAT. Leptin and Pparg2 DNA methylation were correlated with gene expression in GAT. Our study shows that prolonged exposure to HFD in adulthood is associated with a gradually increasing DNA methylation level at the Leptin and Pparg2 promoters in a depot-specific manner.

Figure 1. Average DNA methylation of the promoter region of Leptin and Pparg2 before HFD exposure.

(a,b) Schematic overview of the measured Leptin (a) and Pparg2 (b) location using reference genome (GRCm38/mm10) and amplicon size; CpGs displayed in red could not be analysed (c,d) Average DNA methylation of the Leptin and Pparg2 promoter (y-axis) in each depot for each CpG site relative to the transcription start site (x-axis). Columns represent the mean ± SEM.

Figure 2. Average DNA methylation after HFD exposure over time.

Leptin (a,c) and Pparg2 (b,d) promoter DNA methylation pattern over time observed in GAT (a,b) and SAT (c,d). Line represent the mean ± SEM.

Figure 3. CLS formation over time and relationship with average DNA methylation.

(a,b) Average DNA methylation correlated with CLS formation per 1000 cells. Individual colours depict different time points.

Figure 4. Comparison between Leptin and Pparγ2 gene expression patterns and DNA methylation.

(a,c) Pearson correlation coefficient between the log expression fold change and individual CpG DNA methylation in GAT and SAT. Columns represent the mean ± SEM (b,d) Correlation analysis of DNA methylation of an individual CpG site of Leptin and Pparg2 against the log fold change gene expression.

Figure 5. Functional changes for Leptin and Pparg2.

(a) Leptin plasma levels over time; columns represent the mean ± SEM (b) Gene expression changes of Pparg2 target genes over time.