miR-148a is Associated with Obesity and Modulates Adipocyte Differentiation of Mesenchymal Stem Cells through Wnt Signaling

Obesity results from numerous, interacting genetic, behavioral, and physiological factors. Adipogenesis is partially regulated by several adipocyte-selective microRNAs (miRNAs) and transcription factors that regulate proliferation and differentiation of human adipose-derived mesenchymal stem cells (hMSCs-Ad). In this study, we examined the roles of adipocyte-selective miRNAs in the differentiation of hMSCs-Ad to adipocytes. Results showed that the levels of miR-148a, miR-26b, miR-30, and miR-199a increased in differentiating hMSCs-Ad. Among these miRNAs, miR-148a exhibited significant effects on increasing PPRE luciferase activity (it represents PPAR-dependent transcription, a major factor in adipogenesis) than others. Furthermore, miR-148a expression levels increased in adipose tissues from obese people and mice fed high-fat diet. miR-148a acted by suppressing its target gene, Wnt1, an endogenous inhibitor of adipogenesis. Ectopic expression of miR-148a accelerated differentiation and partially rescued Wnt1-mediated inhibition of adipogenesis. Knockdown of miR-148a also inhibited adipogenesis. Analysis of the upstream region of miR-148a locus identified a 3 kb region containing a functional cAMP-response element-binding protein (CREB) required for miR-148a expression in hMSCs-Ad. The results suggest that miR-148a is a biomarker of obesity in human subjects and mouse model, which represents a CREB-modulated miRNA that acts to repress Wnt1, thereby promoting adipocyte differentiation.