Standardized Hydrangea serrata (Thunb.) Ser. Extract Ameliorates Obesity in db/db Mice

We previously reported the potential anti-obesity effects of the water extract of Hydrangea serrata (Thunb.) Ser. leaves (WHS) in high-fat diet-induced obese mice. As an extension of our previous study, we investigated the anti-adipogenic and anti-obesity effects of WHS and its underlying molecular mechanisms in 3T3-L1 preadipocytes and genetically obese db/db mice. WHS attenuated the gene expression of adipogenic transcription factors, CCAAT/enhancer binding protein (C/EBP)α, peroxisome proliferator-activated receptor (PPAR)γ, and sterol regulatory element binding protein (SREBP)-1. Moreover, WHS inhibited the mitotic clonal expansion of preadipocytes by inducing G₁ cell cycle arrest. Oral administration of WHS alleviated body weight gain and body fat accumulation in vivo. In addition, adipocyte hypertrophy and liver steatosis were ameliorated by WHS treatment. WHS reduced C/EBPα, PPARγ, and SREBP-1 expression and activated AMPKα phosphorylation in both white adipose tissue (WAT) and liver tissue. WHS also mildly upregulated the expression of thermogenic proteins, including uncoupling protein-1, PPARs, PPARγ coactivator-1α, and sirtuin-1, in brown adipose tissue (BAT). Furthermore, WHS altered the gut microbiota composition to resemble that of wild-type mice. Taken together, our findings suggest that WHS could alleviate adiposity by inhibiting adipogenesis in WAT and the liver and modulating the gut microbiota.