Morus alba leaves ethanol extract protects pancreatic islet cells against dysfunction and death by inducing autophagy in type 2 diabetes.

BACKGROUND: Protection of pancreatic islet cells against dysfunction or death by regulating autophagy is considered to be an effective method for treatment of type 2 diabetes mellitus (T2DM). Morus alba leaves (mulberry leaves), a popular herbal medicine, have been used for prevention of T2DM since ancient times. PURPOSE: This study aimed to clarify whether Morus alba leaves ethanol extract (MLE) could protect islet cells in vivo and in vitro by regulating autophagy in T2DM, and explore the possible mechanism of action. METHODS: The main chemical constituents in MLE were analyzed by HPLC. The T2DM rat model was induced via high-fat diet combined with peritoneal injection of low-dose streptozotocin, and MLE was administered by oral gavage. Fasting blood glucose (FBG) and plasma insulin were measured, and homeostatic model assessment of ß cell function (HOMA-ß) and insulin resistance (HOMA-IR) were determined. The histomorphology of pancreas islets was evaluated by haematoxylin and eosin staining. In palmitic acid (PA)-stressed INS-1 rat insulinoma cells, cell viability was assayed by an MTT method. Expression of the autophagy-related proteins LC3 I/II, p62, p-AMPK and p-mTOR in islet tissues and INS-1 cells was evaluated by western blotting or immunohistochemistry analysis. RESULTS: The four main chemical constituents in MLE were identified as chlorogenic acid, rutin, isoquercitrin and quercitrin. MLE ameliorated hyperglycemia, insulin resistance and dyslipidemia of T2DM rats with prominent therapeutic effect. Further study indicated that MLE observably improved islet function, alleviated islet injury of T2DM rats, and inhibited PA-induced INS-1 cell death. On the other hand, MLE significantly induced autophagy in islet cells both in vivo and in vitro, and autophagy inhibitors abolished its therapeutic effect on T2DM rats and protective effect on islet cells. Apart from this, MLE markedly activated the AMPK/mTOR pathway in INS-1 cells, and the AMPK inhibitor prevented the autophagy induction ability of MLE. CONCLUSION: Together, MLE could protect islet cells against dysfunction and death by inducing AMPK/mTOR-mediated autophagy in T2DM, and these findings provide a new perspective for understanding the treatment mechanism of Morus alba leaves against T2DM.

P450 enzymes-based metabolic interactions between monarch drugs and the other constituent herbs: A strategy to explore compatibility mechanism of Sangju-Yin.

BACKGROUND: Herbal compatibility of compound formulas can enhance therapeutic effects or reduce side effects of the monarch drugs, but majority of compatibility mechanisms are still unknown. Sangju-Yin, a well-known Chinese compound formula, is currently used to treat common cold in clinical. PURPOSE: In this study, we proposed a strategy to explore the compatibility mechanism of Sangju-Yin by investigating P450 enzymes-based metabolic interactions between monarch drugs and the other constituent herbs. METHODS: Under the guidance of traditional Chinese medicine theory, the constituent herbs of Sangju-Yin were divided into four groups, including monarch drugs, monarch drugs with addition of minister drugs, monarch drugs with addition of minister and adjuvant drugs, as well as the whole recipe, namely monarch drugs with addition of minister, adjuvant and conductant drugs. Their effects on rats in vivo P450 (CYP1A2, CYP2A3, CYP2C6, CYP2C11 and CYP3A1) activities after oral administration were evaluated using probe drug assay based on LC-MS/MS. Moreover, effects of the four groups of herbs on mRNA expression of P450 enzymes after oral administration, as well as in vitro P450 activities after co-incubation, were investigated to explore the underlying mechanisms. RESULTS: Comparing with monarch drugs, addition of different constituent herbs significantly enhanced CYP1A2 and CYP2C6 activities, and inhibited CYP2A3 and CYP3A1 activities, indicating their possible influences on plasma concentrations of active constituents in the monarch drugs. Mechanism study suggested that these herbs affected P450 activities by transcriptional regulation and/or direct interaction with the enzymes. CONCLUSION: This study clarified the compatibility mechanism of Sangju-Yin from the aspect of P450 enzymes-based metabolic interactions, which would benefit better understanding of the therapeutic basis of Sangju-Yin.