In vivo brown adipogenic reprogramming induced by a small molecule cocktail

Abstract

Research on the browning of adipocytes has been increasing in recent years owing to the prevalence of lifestyle diseases such as obesity and diabetes. Accumulation of brown fat enhances energy expenditure and could be a strategy to fight obesity. While approaches to induce browning in animals for therapeutic purposes have been tested, clinically applicable options are limited. Here, we propose chemically induced in vivo brown adipogenic reprogramming for the therapeutic application of brown adipocytes. By phenotypic screening, we identified a novel combination of two small molecules, SB431542 (SB) and NKH477 (NK), a TGFβ inhibitor and a cAMP activator, respectively, that could reprogram mouse embryonic fibroblasts (MEFs) to adipocyte-like cells with brown/beige adipocyte properties. We demonstrated that the expression of both Pparγ and Cebpβ via TGFβ inhibition and cAMP activation is essential for the increased activation of UCP1 due to the synergistic effects of SB and NK combination (SBNK) on adipogenesis. We further demonstrated the potential clinical application of this in vivo brown adipogenic reprogramming by showing that high-fat diet (HFD)--fed mice treated intraperitoneally with the SBNK exhibited enhanced browning capacity and were protected from HFD-induced impairment of glucose metabolism. Finally, microneedle patches embedded with SBNK-loaded nanoparticles were applied to the mice's skin around subcutaneous white adipose tissue to test the efficacy of local delivery, which also showed a browning effect. Taken together, a novel combination of small molecules that synergistically induced browning with far-reaching translatable therapeutic potentials was developed in this study.

Keywords: Adipocyte browning; Brown adipocytes; Cebpβ adipogenesis; Chemical-based in vivo reprogramming; Microneedle; Pparγ adipogenesis; Small molecules.