Hispidin rescues palmitate­induced insulin resistance in C2C12 myotubes.

Skeletal muscle serves an important role in the utilization of glucose during insulin­stimulated conditions. Excessive saturated fatty acids are considered to be a major contributing factor to insulin resistance in skeletal muscle cells. The present study investigated the effects of hispidin on palmitate­induced insulin resistance in C2C12 skeletal muscle myotubes via an MTT assay, glucose uptake assay, Oil­Red­O staining and western blot analysis. Hispidin reversed the palmitate­induced inhibition of glucose uptake, and inhibited palmitate­induced intracellular lipid accumulation. Hispidin suppressed insulin receptor substrate­1 Ser307 phosphorylation, and significantly promoted the activation of phosphatidylinositol­3­kinase and Akt, via inhibition of protein kinase C theta. Furthermore, hispidin treatment of C2C12 muscle cells increased glucose uptake via activation of adenosine monophosphate­activated protein kinase. These findings indicated that hispidin may improve palmitate­induced insulin resistance in skeletal muscle myotubes, and therefore hispidin treatment may be beneficial for patients with diabetes.

Cytoprotective effect of hispidin against palmitate-induced lipotoxicity in C2C12 myotubes.

It is well known that Phellinus linteus, which produces hispidin and its derivatives, possesses antioxidant activities. In this study, we investigated whether hispidin has protective effects on palmitate-induced oxidative stress in C2C12 skeletal muscle cells. Our results showed that palmitate treatment in C2C12 myotubes increased ROS generation and cell death as compared with the control. However, pretreatment of hispidin for 8 h improved the survival of C2C12 myotubes against palmitate-induced oxidative stress via inhibition of intracellular ROS production. Hispidin also inhibited palmitate-induced apoptotic nuclear condensation in C2C12 myotubes. In addition, we found that hispidin can suppress cleavage of caspase-3, expression of Bax, and NF-κB translocation. Therefore, these results suggest that hispidin is capable of protecting C2C12 myotubes against palmitate-induced oxidative stress.

Mechanism of macrophage activation induced by polysaccharide from Cordyceps militaris culture broth.

Mushroom-derived polysaccharides have been shown to stimulate immune responses. Our previous report showed that the novel polysaccharide PLCM isolated from the culture broth of Cordyceps militaris could induce nitric oxide production in the murine macrophage-like cell line RAW264.7. In this study, we show that PLCM enhances immunostimulatory activities such as the release of toxic molecules (nitric oxide and reactive oxygen species), secretion of the cytokine tumor necrosis factor (TNF)-α, and phagocytic uptake in RAW264.7 macrophages. In addition, all the specific inhibitors against the mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-κB) (SN50, BAY11-7082, PD98059, SP600125 and SB203580) markedly suppressed the nitric oxide production and phagocytic uptake induced by PLCM. Moreover, antibodies specific to the extracellular domain of Toll-like receptor-2, Toll-like receptor-4 or the macrophage receptor Dectin-1 significantly attenuated PLCM-induced secretion of TNF-α. Our results indicate that the C. militaris polysaccharide activates macrophages through the MAPKs and NF-κB signaling pathways via Toll-like receptor 2, Toll-like receptor 4, and Dectin-1.

Cyanidin-3-glucoside isolated from mulberry fruits protects pancreatic ß-cells against glucotoxicity-induced apoptosis.

The present study investigated the cytoprotective effects of cyanidin­3­glucoside (C3G), isolated from mulberry fruits, on the glucotoxicity­induced apoptosis of pancreatic ß­cells to evaluate the antidiabetic effects of this compound. MIN6N pancreatic ß­cells were used to investigate the cytoprotective effects of C3G. In addition, the effects of C3G on the glucotoxicity­induced apoptosis of pancreatic ß­cells was evaluated using MTT assay, immunofluorescent staining, flow cytometric and western blot analyses. The pancreatic ß­cells cultured under high glucose conditions exhibited distinct apoptotic features. C3G decreased the generation of intracellular reactive oxygen species, DNA fragmentation and the rate of apoptosis. C3G also prevented pancreatic ß­cell apoptosis induced by high glucose conditions by interfering with the intrinsic apoptotic pathways. In addition, C3G treatment resulted in increased insulin secretion compared with treatment with high glucose only. In conclusion, the results of the present study suggested that C3G obtained from mulberry fruits may be a potential phytotherapeutic agent for the prevention of diabetes.

Cordyceps militaris extract protects human dermal fibroblasts against oxidative stress-induced apoptosis and premature senescence.

Oxidative stress induced by reactive oxygen species (ROS) is the major cause of degenerative disorders including aging and disease. In this study, we investigated whether Cordyceps militaris extract (CME) has in vitro protective effects on hydrogen peroxide-induced oxidative stress in human dermal fibroblasts (HDFs). Our results showed that the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of CME was increased in a dose-dependent manner. We found that hydrogen peroxide treatment in HDFs increased ROS generation and cell death as compared with the control. However, CME improved the survival of HDFs against hydrogen peroxide-induced oxidative stress via inhibition of intracellular ROS production. CME treatment inhibited hydrogen peroxide-induced apoptotic cell death and apoptotic nuclear condensation in HDFs. In addition, CME prevented hydrogen peroxide-induced SA-ß-gal-positive cells suggesting CME could inhibit oxidative stress-induced premature senescence. Therefore, these results suggest that CME might have protective effects against oxidative stress-induced premature senescence via scavenging ROS.

Mulberry fruit extract protects pancreatic ß-cells against hydrogen peroxide-induced apoptosis via antioxidative activity.

Among the many environmental stresses, excessive production of reactive oxygen species (ROS) and the ensuring oxidative stress are known to cause significant cellular damage. This has clinical implications in the onset of type 1 diabetes, which is triggered by the destruction of pancreatic ß-cells and is associated with oxidative stress. In this study, we investigated the protective and antioxidative effects of mulberry extract (ME) in insulin-producing pancreatic ß-cells. We found that ME protects pancreatic ß-cells against hydrogen peroxide (H2O2)-induced oxidative stress and the associated apoptotic cell death. ME treatment significantly reduced the levels of H2O2-induced 2-diphenyl-1-picrylhydrazyl (DPPH) radicals, and lipid peroxidation and intracellular ROS accumulation. In addition, ME inhibited DNA condensation and/or fragmentation induced by H2O2. These results suggest that ME protects pancreatic ß-cells against hydrogen peroxide-induced oxidative stress.