miR-196b-5p controls adipocyte differentiation and lipogenesis through regulating mTORC1 and TGF-β signaling

Area of Science:

• Molecular Biology
• Cell Biology
• Metabolic Research

Background:

• MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression.
• Dysregulation of miRNAs is implicated in various diseases, including obesity.
• Adipogenesis, the process of fat cell formation, is a complex pathway influenced by genetic and epigenetic factors.

Purpose of the Study:

• To investigate the role of miR-196b-5p in adipogenesis and lipogenesis.
• To elucidate the molecular mechanisms underlying miR-196b-5p-mediated regulation of fat cell differentiation.
• To identify the direct target genes and signaling pathways influenced by miR-196b-5p.

Main Methods:

• Quantitative real-time PCR to measure miR-196b-5p expression.
• In vitro adipogenic differentiation assays using primary and established marrow stromal progenitor cells.
• Western blotting to assess protein levels of target genes and signaling pathway components.
• Luciferase reporter assays to confirm direct targeting of genes by miR-196b-5p.
• Gene silencing and overexpression techniques to manipulate miR-196b-5p, Tsc1, Tgfbr1, and mTORC1 signaling.

Main Results:

• miR-196b-5p expression was upregulated during adipogenic differentiation of progenitor cells.
• Overexpression of miR-196b-5p enhanced adipogenesis and lipogenesis, while inhibition suppressed these processes.
• Tuberous sclerosis 1 (Tsc1) and transforming growth factor-β receptor 1 (TGFBR1) were identified as direct targets of miR-196b-5p.
• miR-196b-5p reduced TSC1 protein levels, leading to activation of mammalian target of rapamycin complex 1 (mTORC1) signaling.
• Perturbation of Tsc1 or activation of mTORC1 signaling mimicked or modulated the effects of miR-196b-5p on adipogenesis.
• Overexpression of Tgfbr1 partially blocked the pro-adipogenic effects of miR-196b-5p.
• Zinc finger E-box-binding homeobox 1 (ZEB1) was found to transcriptionally upregulate miR-196b-5p expression.

Conclusions:

• miR-196b-5p acts as a positive regulator of adipogenesis and lipogenesis in progenitor cells.
• The pro-adipogenic effects of miR-196b-5p are mediated through the downregulation of Tsc1 and Tgfbr1, impacting mTORC1 and TGF-β signaling pathways.
• ZEB1-mediated upregulation of miR-196b-5p represents a novel regulatory axis in adipogenesis.
• miR-196b-5p is a potential therapeutic target for obesity and related metabolic disorders.