A Novel mechanism for depot-specific leptin gene expression regulation and its persistence after weight loss.

Leptin gene (Lep) expression correlates with fat mass but differs between epididymal and inguinal fat depots in obesity. We investigated whether DNA methylation of a Lep enhancer (RS1) and the long non-coding RNA lncOb epigenetically regulate this depot-specific expression. We analyzed DNA methylation, Lep and lncOb expression in fat depots across metabolic states in male C57BL/6 mice using CRISPR-dCas9-KRAB-mediated repression, methylation-sensitive luciferase assays, and mass spectrometry. Under obesogenic conditions, RS1 methylation increased specifically in hypertrophic adipocytes of epididymal fat, repressing Lep transcription. This methylation persisted after long-term weight loss. LncOb expression correlated with Lep levels but was reduced in epididymal fat during obesity and remained suppressed post-weight loss. Together, our findings demonstrate that adipocyte Lep expression is dynamically regulated by depot-specific epigenetic mechanisms that become dysregulated in obesity and resist reversal by weight loss, providing a unifying molecular mechanism for depot-specific Lep expression differences in a state of obesity.