MicroRNAs as a Novel Mechanism by which Eicosapentaenoic Acid Mediates Inflammation in Diet‐Induced Obesity

Obesity is associated with the expansion of adipose tissue that creates a system in which the body transitions into a prothrombotic and inflammatory state. This is in part due to an imbalance between reduced levels of anti‐inflammatory and increased levels of pro‐inflammatory adipokines secreted from adipose tissue, resulting in a chronic, low‐grade inflammation in adipose tissue. Previous studies from our laboratory have demonstrated that C57BL/6J mice fed high fat diets supplemented with the omega‐3 fatty acid eicosapentaenoic acid (HF‐EPA) exhibited lower adipose and systemic inflammation and macrophage infiltration into white adipose tissue compared to mice fed high fat diets without EPA supplementation (HF). To further dissect mechanisms mediating effects of EPA on adipocyte inflammation, we tested whether EPA regulates specific inflammatory genes (RNA‐Seq with Illumina ® HiSeq TM ) and microRNAs (miRNA profiling with Illumina ® MiSeq TM ) in visceral white adipose tissue (VAT) of mice. We identified 200 genes and 64 miRNAs that were differentially expressed (95% confidence and p<0.05) in VAT from two groups of mice fed either a HF or HF‐EPA diet for 11 weeks. QIAGEN's Ingenuity ® Pathway Analysis (IPA ® ) was used to characterize mRNA‐miRNA pairs that were regulated by EPA. Among these, the proinflammatory miR‐221‐3p, a key miRNA determined by IPA ® to be associated with diabetes mellitus, was found to be down regulated by EPA. Nuclear factor kappa B (NF‐κB), pattern recognition receptors (PRR), and nuclear factor of activated T‐cells (NFAT) pathways were among the major canonical pathways that were reduced by EPA in VAT. Moreover, expression of lipopolysaccharide (LPS), interferon gamma (INFγ), and transforming growth factor alpha (TGF‐α) were also significantly reduced in VAT of HF‐EPA compared to HF diets. We further confirmed by quantitative reverse transcription polymerase chain reaction that EPA significantly reduced miR‐221 expression by 3‐fold in VAT (p<0.05). In future studies, we will conduct mechanistic experiments in cultured adipocytes treated with saturated fatty acids (to mice HF diets) and with or without EPA to confirm miRNAs and target genes regulated by these fatty acids, using miRNA mimics and inhibitors. We conclude that global genomic studies are valuable approaches to identify new pathways regulated by omega‐3 fatty acids that may pave the way for novel targets to prevent/treat metabolic complications associated with obesity and inflammation. Support or Funding Information Funding Support: USDA NIFA Grant # 11672117 and startup funds from Texas Tech University