Cocoa procyanidins attenuate 4-hydroxynonenal-induced apoptosis of PC12 cells by directly inhibiting mitogen-activated protein kinase kinase 4 activity.

Neurodegenerative disorders such as Alzheimer's disease (AD) are associated with oxidative stress, and it has been suggested that apoptosis is a crucial pathway in neuronal cell death in AD patients. 4-Hydroxynonenal (HNE), one of the aldehydic products of membrane lipid peroxidation, is reported to be elevated in the brains of AD patients and mediates the induction of neuronal apoptosis in the presence of oxidative stress. In this study, we investigated the HNE-induced apoptosis mechanism and the protective effects of the cocoa procyanidin fraction (CPF) and its major antioxidant procyanidin B2 against the apoptosis induced by HNE in rat pheochromocytoma (PC12) cells. HNE-induced nuclear condensation and increased sub-G1 fraction, both of which are markers of apoptotic cell death, were inhibited by CPF and procyanidin B2. Intracellular reactive oxygen species (ROS) accumulation was attenuated by pretreatment with CPF and procyanidin B2. CPF and procyanidin B2 also prevented HNE-induced poly(ADP-ribose) polymerase cleavage, antiapoptotic protein (Bcl-2 and Bcl-X(L)) down-regulation, and caspase-3 activation. Activation of c-Jun N-terminal protein kinase (JNK) and mitogen-activated protein kinase kinase 4 (MKK4) was attenuated by CPF and procyanidin B2. Moreover, CPF and procyanidin B2 bound directly to MKK4 and inhibited its activity. Data obtained with SP600125, a selective inhibitor of JNK, revealed that JNK is involved in HNE-induced apoptosis through the inhibition of PARP cleavage and caspase-3 activation in PC12 cells. Collectively, these results indicate that CPF and procyanidin B2 protect PC12 cells against HNE-induced apoptosis by blocking MKK4 activity as well as ROS accumulation.

Antihyperglycemic effect of stem bark powder from paper mulberry (Broussonetia kazinoki Sieb.) in type 2 diabetic Otsuka Long-Evans Tokushima fatty rats.

The effect of stem bark powder from paper mulberry (PMSB) on serum glucose, insulin, fructosamine, and lipid concentrations, as well as enzyme activities that serve as liver injury markers, was investigated in genetically diabetic Otsuka Long-Evans Tokushima fatty (OLETF) rats. Both nondiabetic Long-Evans Tokushima Otsuka (LETO) rats and diabetic OLETF rats (30 weeks old) were fed a semisynthetic diet with or without 50 g/kg PMSB for 8 weeks and then compared. The OLETF control rats showed a high amount of daily water intake in comparison to those in the LETO group. The concentrations of glucose, fructosamine, total lipid, triglyceride, total cholesterol, and high-density lipoprotein-cholesterol and the activities of aspartate aminotransferase and alanine aminotransferase (ALT) in serum were higher in the OLETF control rats than those in the LETO control rats. However, PMSB ingestion decreased the serum levels of glucose, fructosamine, triglyceride, and total cholesterol and the activity of ALT in the OLETF rats, but not in the LETO rats. The concentration of serum insulin was also significantly increased by PMSB consumption in the OLETF rats compared to the OLETF control rats. These results suggest that PMSB might have an antihyperglycemic effect in the OLETF rat and that the increased blood insulin level would be an important regulatory factor for improving hyperglycemia in the current animal model.