MicroRNA-99a mimics inhibit M1 macrophage phenotype and adipose tissue inflammation by targeting TNFα

摘要

In human adipose tissue and obesity,miR-99a expression is negatively correlated with inflammation.Therefore,the present study investigated the role of miR-99a in macrophage phenotype activation and adipose tissue inflammation.M2 BMDMs showed a significant increase in miR-99a expression when compared to the M0 and M1 phenotypes.Phenotype-switching experiments established an association between upregulated miR-99a expression and the M2 phenotype.Overexpression of miR-99a prevented M1 phenotype activation and attenuated bactericidal activity.Likewise,knockdown of miR-99a abolished M2 phenotype activation.By means of in silico target prediction tools and a luciferase reporter assay,TNFαwas identified as a direct target of miR-99a.Knockdown of TNFαrecapitulated the effect of miR-99a overexpression in M1 BMDMs.In a db/db mice model,miR-99a expression was reduced in eWAT and F4/80+ATMs.Systemic overexpression of miR-99a in db/db mice attenuated adipocyte hypertrophy with increased CD301 and reduced CD86 immunostaining.Flow cytometry analysis also showed an increased M2 and a reduced M1 macrophage population.Mimics of miR-99a also improved the diabetic dyslipidemia and insulin signaling in eWAT and liver,with an attenuated expression of gluconeogenesis and cholesterol metabolism genes in the liver.Furthermore,adoptive transfer of miR-99a-overexpressing macrophages in the db/db mice recapitulated in vivo miR-99a mimic effects with increased M2 and reduced M1 macrophage populations and improved systemic glucose,insulin sensitivity,and insulin signaling in the eWAT and liver.The present study demonstrates that miR-99a mimics can regulate macrophage M1 phenotype activation by targeting TNFα.miR-99a therapeutics in diabetic mice reduces the adipose tissue inflammation and improves insulin sensitivity.