(P06-031-23) Investigation of the Anti-Diabetic Effects of Chinese Sweet Tea Leaf Extract and Its Fermented Product In Vitro and In Vivo

Objectives: Type 2 diabetes (T2D) is a chronic metabolic disease featured by hyperglycemia. Current approaches for treating T2D have low response rates or induce severe side effects which largely limit their efficacy. As such, development of alternative cost-effective approaches for combating T2D is imperative. Rubus suavissimus, a Chinese tisane herb known as the sweet tea leaf, has reported therapeutic effects in managing metabolic disorders but its efficacy and mechanism of action in T2D are unclear. This study aimed to investigate the anti-diabetic effects of R. suavissimus leaf extract (RSE) and a novel probiotic-fermented product (fRSE).

Methods: For preparing fRSE, RSE was fermented with two probiotics for releasing bioactive metabolites. For in vitro studies, phytochemicals were analyzed by UHPLC-MS/MS to compare phenolic profiles before and after fermentation. The ability of RSE and fRSE to inhibit carbohydrate-metabolizing enzymes was examined. For in vivo chronic studies, male C57BLKS/J-db/db mice were divided into 5 groups: control, low dose, high dose, fRSE and fermented control (delivered through drinking water for 18 weeks). The effects of RSE and fRSE on body weight, glucose tolerance (by OGTT) and insulin sensitivity (by ITT) were determined. Bioavailability of anti-diabetic agents was also examined. Future biochemical, metabolomics and metagenomics studies will be done to elucidate the mechanisms.

Results: Upon fermentation, major RSE phenolic compounds were converted to bioactive metabolites (e.g., urolithins, hydroxybenzoic acids). In vitro enzymatic assays showed their remarkable inhibition against αλπηα-glucosidase activities, potentially limiting carbohydrates metabolism. In addition, our in vivo study revealed that both RSE and fRSE significantly reduced excessive body weight gain and improved glucose tolerance starting from week 8 despite the differences in circulating metabolites.

Conclusions: This is the first study to evaluate the anti-diabetic efficacy of RSE and its fermented product in mice. The improved bioavailability of RSE upon fermentation may enhance the efficacy, revealing the potential of RSE-derived products to serve as alternative remedies to T2D and provide translational knowledge for future clinical applications.

Funding Sources: PolyU Research Centre for Chinese Medicine Innovation