Suppression of adipogenesis by Au nanostructures-conjugated Sargassum seaweed extracts in 3 T3-L1 adipocytes

Recently, with the development of metal nanostructure synthesis technology, Au nanostructures (AuNPs) are synthesized using seaweed extract without using an organic solvent and applied to the pharmaceutical field. In this regard, in this study, AuNPs biosynthesis was mediated through extracts of two brown algae (Sargassum siliquastrum SS] and Sargassum horneri SH]) without the use of stabilizers or surfactants. In addition, we investigated the effects of SS-AuNPs (SS-functionalized AuNPs) and SH-AuNPs (SH-functionalized AuNPs) on adipogenesis in adipocytes and their underlying molecular mechanisms. A rapid and simplified synthesis of SS-AuNP and SH-AuP was achieved using aqueous extracts of SS and SH. The morphology, structure and composition of SS-AuNPs and SH-AuNPs were characterized by DLS, FTIR, UV–Vis spectroscopy, HR-TEM and EDS analysis. The stable monodisperse SS-AuNPs and SH-AuPs were synthesized with mean sizes of 17.47 ± 0.13 nm and 21.0 ± 2.74 and zeta potentials of ?31.9 ± 0.75 and ?34.57 ± 4.43, the biosynthetic AuNPs with the face-centered structure of SS-AuNPs and SH-AuPs had crystalline characteristics, and many functional groups that play an important role in the biological reduction present in the SS and SH extracts were adsorbed on the surfaces of the SS-AuNPs and SH-AuPs. This study was conducted to investigate the effect of SS-AuNPs and SH-AuPs on adipogenesis in adipocytes. SS-AuNPs and SH-AuPs reduced morphological changes and increased lipid accumulation by approximately 80% compared with that in mature adipocytes (MDI-induced). This result was accompanied by a reduction in the triglyceride content. SS-AuNPs and SH-AuPs suppressed lipid accumulation by downregulating C/EBPα, PPARγ, SREBP 1, FAS, and aP2 mRNA and protein expression. Furthermore, SS-AuNPs and SH-AuPs induced the mRNA and protein expression of UCP1, PRDM16, and PGC1α to increase mitochondrial biogenesis in mature adipocytes and effectively induced brown adipogenesis. SS-AuNPs and SH-AuPs have potent anti-adipogenic effects and can be used as potential therapeutic agents for obesity.