Conclusions
HFD-induced obesity downregulates miR-30 by DNA methylation thereby inducing Notch1 signaling in ATMs and their polarization to M1 macrophages. These findings identify miR-30 as a regulator of pro-inflammatory ATM polarization and suggest that miR-30 manipulation could be a therapeutic target for obesity-induced inflammation.
Methods
Male C57BL/6J mice were fed normal chow diet (NCD) or high-fat diet (HFD) for 16 weeks to develop lean and diet-induced obese mice, respectively. Transcriptome microarrays, microRNA microarrays, and MeDIP-Seq were performed on ATMs isolated from visceral fat. Pathway analysis and bone marrow-derived macrophage (BMDM) transfections further allowed computational and functional analysis of miRNA-mediated ATM polarization.
Results
ATMs from HFD-fed mice were skewed toward M1 inflammatory phenotype. Concurrently, the expression of miRs 30a-5p, 30c-5p, and 30e-5p was downregulated in ATMs from HFD mice when compared to mice fed NCD. The miR-30 family was shown to target Delta-like-4, a Notch1 ligand, whose expression was increased in HFD ATMs. Inhibition of miR-30 in conditioned BMDM triggered Notch1 signaling, pro-inflammatory cytokine production, and M1 macrophage polarization. In addition, DNA hypermethylation was observed in mir30-associated CpG islands, suggesting that HFD downregulates miR-30 through epigenetic modifications. Conclusions: HFD-induced obesity downregulates miR-30 by DNA methylation thereby inducing Notch1 signaling in ATMs and their polarization to M1 macrophages. These findings identify miR-30 as a regulator of pro-inflammatory ATM polarization and suggest that miR-30 manipulation could be a therapeutic target for obesity-induced inflammation.