Flavonoids extracted from mulberry (Morus alba L.) leaf improve skeletal muscle mitochondrial function by activating AMPK in type 2 diabetes.

ETHNOPHARMACOLOGICAL RELEVANCE: Mulberry (Morus alba L.) leaves have been widely applied to controlling blood glucose as a efficacious traditional Chinese medicine or salutary medical supplement. The extracts of mulberry leaf suppress inflammatory mediators and oxidative stress, protect the pancreatic ß-cells and modulate glucose metabolism in diabetic rats. Our previous studies and others have shown that mulberry leaf extract has excellent therapeutic effects on type 2 diabetes mellitus (T2DM), however, the underlying mechanism remains to be studied. AIM OF THE STUDY: Skeletal muscle insulin resistance (IR) plays an important role in the pathogenesis of T2DM. The aim of this study was to investigate the effects and mechanisms of Mulberry leaf flavonoids (MLF) in L6 skeletal muscle cells and db/db mice. MATERIALS AND METHODS: L6 skeletal muscle cells were cultured and treated with/without MLF for in vitro studies. For in vivo studies, the db/db mice with/without MLF therapy were used. Coomassie brilliant blue staining and α-SMA immunofluorescence staining were used to identify the differentiated L6 cells. Glucose level and ATP level of L6 myotubes were performed by optical density detection and cell viability was performed by MTT method. Mitochondrial membrane potential of L6 myotubes was detected by JC-1 fluorescent staining. ROS level of L6 myotubes was detected by DCFH-DA fluorescent staining. The body weight, food intake, and blood glucose of the mice were measured in different treatment days. Oral glucose tolerance test (OGTT), starch glucose tolerance test (STT) and insulin tolerance test (ITT) were performed in mice. Glycated hemoglobin, glycated serum protein, insulin, liver and muscle glycogen, total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-c) and low-density lipoprotein cholesterol (LDL-c) of the mice were detected by corresponding kit. The pathologic change of pancreas and skeletal muscle of mice were performed by H & E staining. Immunohistochemistry staining was used to detect the GLUT4 and p-AMPK expressions in skeletal muscle in mice. GLUT4, CPT-1, NRF1, COXIV, PGC-1α, and p-AMPK expression levels in L6 cells and mice were detected by western bolt assay. RESULTS: MLF and metformin significantly ameliorated muscle glucose uptake and mitochondrial function in L6 muscle cells. MLF also increased the phosphorylation of AMPK and the expression of PGC-1α, and up-regulated the protein levels of m-GLUT4 and T-GLUT4. These effects were reversed by the AMPK inhibitor compound C. In db/db mice, MLF improve diabetes symptoms and insulin resistance. Moreover, MLF elevated the levels of p-AMPK and PGC-1α, raised m-GLUT4 and T-GLUT4 protein expression, and ameliorated mitochondrial function in skeletal muscle of db/db mice. CONCLUSIONS: MLF significantly improved skeletal muscle insulin resistance and mitochondrial function in db/db mice and L6 myocytes through AMPK-PGC-1α signaling pathway, and our findings support the therapeutic effects of MLF on type 2 diabetes.

Polysaccharides of Fructus corni Improve Ovarian Function in Mice with Aging-Associated Perimenopause Symptoms.

OBJECTIVE: Perimenopause symptoms have an extremely high incidence in aging women. Development of new strategies to improve perimenopause symptoms is important topic in clinical context. Increasing studies have shown that the polysaccharides of Fructus corni (PFC) have many pharmacological activities including antiaging effects. Here, we evaluated the effects of PFC on the ovarian function in natural aging-associated perimenopause symptoms in mice. METHODS: Natural aging mice (16-month old) were orally administrated with PFC at 1.11 g/kg daily for 24 days with none-treated young mice (3-month old) as control. Blood samples were collected for measurements of serum levels of estradiol, progesterone, luteinizing hormone (LH), and follicle stimulating hormone (FSH). Ovaries were isolated for histopathological and molecular exanimations. RESULTS: We found that the aging mice had decreased number of growing follicles and corpus luteum in ovary, but treatment with PFC restored their amounts. Measurement of hormones showed that there were low serum levels of estradiol and progesterone but high levels of LH and FSH in aging mice; however PFC restored estradiol and progesterone levels but reduced LH and FSH levels. Immunohistochemical analysis with ovarian tissues also revealed that the expression of inhibin and insulin-like growth factor 1 was reduced in the ovary of aging mice but was restored by PFC. These data indicated that PFC regulated ovarian function-associated hormone levels in aging mice. Furthermore, there was reduced expression of antiapoptotic protein Bcl-2 and increased expression of proapoptotic molecules Bax and cleaved-caspase-3 in the ovary of aging mice. However, treatment with PFC upregulated Bcl-2 and downregulated Bax and cleaved-caspase-3, suggesting that PFC inhibited apoptosis of granulosa cells in the ovary of aging mice. CONCLUSION: PFC improved the ovarian function in mice, which had high potential to be developed as a safe and effective therapeutic remedy for aging-associated perimenopause symptoms.