Black mulberry extract inhibits hepatic adipogenesis through AMPK/mTOR signaling pathway in T2DM mice

Black mulberry (Morus nigra L.) is an ancient dual-use plant resource for medicine and food. It is widely used in Uyghur folklore for hypoglycemic treatment and is a folkloric plant medicine with regional characteristics. However, the mechanism of Morus nigra L. treatment in diabetes mellitus has not been fully understood, especially from the perspective of hepatic lipid accumulation is less reported. This study was to explore the potential of Morus nigra L. fruit ethyl acetate extract (MNF-EA) to reduce blood sugar levels by preventing the production of hepatic lipogenesis and to provide more evidence for the use of MNF-EA as an adjuvant therapy for type 2 diabetes mellitus (T2DM). In this study, the chemical composition of MNF-EA was first analyzed and characterized using UPLC-Q-TOF-MS technique. A series of in vitro studies were performed with HepG2-IR cells and oleic acid (OA)-induced HepG2 cells, including MTT assay, glucose uptake assay, oil red O staining and Western blot analysis. The STZ-HFD co-induced T2DM mice were employed for in vivo research, including physical indices, biochemical analysis, histopathological examination, and Western blot analysis. The 19 compounds in MNF-EA were identified by UPLC-Q-TOF-MS technique. Insulin resistance (IR) and lipid droplet accumulation in HepG2 cells were greatly improved by MNF-EA treatment, which had no appreciable side effects at the dosage used. In T2DM mice, MNF-EA decreased fasting blood glucose (FBG), saved body weight, and significantly improved oral glucose tolerance (OGTT) and IR status. In addition, MNF-EA treatment also improved lipid metabolism disorders and liver function in T2DM mice. Histopathological sections showed that MNF-EA treatment reduced hepatic steatosis. Mechanistic studies suggest that MNF-EA acted through the AMPK/mTOR pathway. These results suggest that MNF-EA has great potential to reverse the metabolic abnormalities associated with T2DM by regulating the AMPK/mTOR signaling pathway. Therefore, we believe that MNF is a promising medicinal and food-homologous agent to improve T2DM.