Antidiabetic and antihyperlipidemic activities of Phyllanthus emblica L. extract in vitro and the regulation of Akt phosphorylation, gluconeogenesis, and peroxisome proliferator-activated receptor α in streptozotocin-induced diabetic mice.

Background: The fruits of Phyllanthus emblica L. are high in nutrients and have excellent health care function and developmental value. There are many management strategies available for diabetes and hyperlipidemia. Nevertheless, there is a lack of an effective and nontoxic drug. Objective: The present study was designed to first screen four extracts of P. emblica L. on insulin signaling target gene expression levels, including glucose transporter 4 (GLUT4) and p-Akt/t-Akt. The ethyl acetate extract of P. emblica L. (EPE) exhibited the most efficient activity among the four extracts and was thus chosen to explore the antidiabetic and antihyperlipidemic activities in streptozotocin (STZ)-induced type 1 diabetic mice. Design: All mice (in addition to one control (CON) group) were administered STZ injections (intraperitoneal) for 5 consecutive days, and then STZ-induced mice were administered EPE (at 100, 200, or 400 mg/kg body weight), fenofibrate (Feno) (at 250 mg/kg body weight), glibenclamide (Glib) (at 10 mg/kg body weight), or vehicle by oral gavage once daily for 4 weeks. Finally, histological examination, blood biochemical parameters, and target gene mRNA expression levels were measured, and liver tissue was analyzed for the levels of malondialdehyde (MDA), a maker of lipid peroxidation. Results: EPE treatment resulted in decreased levels of blood glucose, HbA1C, triglycerides (TGs), and total cholesterol and increased levels of insulin compared with the vehicle-treated STZ group. EPE treatment decreased blood levels of HbA1C and MDA but increased glutathione levels in liver tissue, implying that EPE exerts antioxidant activity and could prevent oxidative stress and diabetes. The EPE-treated STZ mice displayed an improvement in the sizes and numbers of insulin-expressing ß cells. EPE treatment increased the membrane expression levels of skeletal muscular GLUT4, and also reduced hepatic mRNA levels of glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase thereby inhibiting hepatic gluconeogenesis. This resulted in a net glucose lowering effect in EPE-treated STZ mice. Furthermore, EPE increased the expression levels of p-AMPK/t-AMPK in both the skeletal muscle and liver tissue compared with vehicle-treated STZ mice. EPE-treated STZ mice showed enhanced expression levels of fatty acid oxidation enzymes, including peroxisome proliferator-activated receptor α (PPARα), but reduced expression levels of lipogenic genes including fatty acid synthase, as well as decreased mRNA levels of sterol regulatory element binding protein 1c (SREBP1c), apolipoprotein-CIII (apo-CIII), and diacylglycerol acyltransferase-2 (DGAT2). This resulted in a reduction in plasma TG levels. EPE-treated STZ mice also showed reduced expression levels of PPAR γ. This resulted in decreased adipogenesis, fatty acid synthesis, and lipid accumulation within liver tissue, and consequently, lower TG levels in liver tissue and blood. Furthermore, EPE treatment not only displayed an increase in the Akt activation in liver tissue, but also in C2C12 myotube in the absence of insulin. These results implied that EPE acts as an activator of AMPK and /or as a regulator of the insulin (Akt) pathway. Conclusions: Taken together, EPE treatment exhibited amelioration of the diabetic and hyperlipidemic state in STZ-induced diabetic mice.

Development of an indolicidin-derived peptide by reducing membrane perturbation to decrease cytotoxicity and maintain gene delivery ability.

Indolicidin (IL) is a cationic antimicrobial peptide and our previous study has demonstrated its potential as a cell penetrating peptide (CPP) to promote gene delivery. However, the cytotoxicity of IL arisen from its membrane perturbation capacity may restrict its clinical application. To promote gene delivery safety and efficiency, an almost mirror-symmetric IL derivative, SAP10 (RRWKFFPWRR-CONH2), was designed in this study. All-atom molecular dynamics (MD) simulations were performed to understand the association between SAP10 and model lipid bilayers. By comparison with IL, SAP10 with high positively charged density resisted its deep insertion into lipid bilayers, which thus reduced its perturbation to lipid bilayers and improved biocompatibility. Consequently, we further mixed SAP10, polyethylenimine (PEI) and DNA to form the ternary nanocomplexes for gene delivery investigation. Both IL and SAP10 weakened the interaction between to DNA and PEI, which may be beneficial to promote the dissociation of internalized DNA from the carrier molecules. In vitro experiments demonstrated that the SAP10-associated ternary nanocomplexes highly promoted the transfection efficiency to various cells with low cytotoxicity. The effect of the SAP10 on promoting gene delivery was mainly contributed by the adsorbed peptides on the nanoparticles rather than the free ones. In particular, the dose of SAP10 could be increased to broaden the administration window, which ensured its safety on transfection. Therefore, our results suggested the argument that the designed SAP10 is a safe and an efficient peptide to promote PEI-mediated gene delivery.