Search

The fibrillation and aggregation of α-synuclein ( AS), along with the conformational transition from random coil to β-sheet, are the critical steps in the development of Parkinson's disease ( PD). It is acknowledged that iron accumulation in the brain may lead to the fibrillation of AS. However, (-)-epigallocatechin gallate ( EGCG) can penetrate the blood-brain barrier, chelate metal ions, and inhibit the fibrillation of amyloid proteins. Therefore, EGCG is warranted to be investigated for its potential to cure amyloid-related diseases. In the present work, we sought to study the effects of EGCG on Fe( III)-induced fibrillation of AS on both molecular and cellular levels. We demonstrate that Fe( III) interacts with the amino residue of Tyr and Ala of AS, then accelerates the fibrillation of AS, and increases intracellular reactive oxygen species ( ROS) in the AS transduced- PC12 cells ( AS- PC12 cells). However, EGCG significantly inhibits this process by chelating Fe( III) and protects AS- PC12 cells against the toxicity induced by ROS and β-sheet-enriched AS fibrils. These findings yield useful information that EGCG might be a promising drug to prevent and treat the neurodegenerative diseases. [ABSTRACT FROM AUTHOR]

ABSTRACT The abnormal aggregation of amyloid proteins is reported to play a critical role in the etiology of neurodegenerative disorders. Studies have shown that excessive ferric irons are associated with the misfolding of amyloid proteins, and that (-)-epigallocatechin gallate (EGCG) is a good metallic ion chelator with inhibitory effect on the aggregation of amyloid proteins. EGCG has been thus considered as a potential drug candidate for the treatment of neurodegenerative diseases. However, the mechanism of action for EGCG in inhibition of aggregation of amyloid proteins is still remaining unclear. Silk fibroin (SF) shares similarities with amyloid proteins in some amino acid sequences and fibrillation kinetics. In this work, therefore, we used SF as a model of protein to investigate the effects of Fe(III) and EGCG on conformational transition by using turbidity assay, thioflavin T (ThT) fluorescence spectroscopy, Raman spectroscopy, and atomic force microscope (AFM). We demonstrated that low concentration of Fe(III) ions promoted the formation of β-sheet conformers, while high concentration of Fe(III) ions inhibited further aggregation of SF. EGCG could significantly inhibit the conformational transition of SF when induced by Fe(III), and decrease the amount of β-sheet conformers dose-dependently. The findings provide important information regarding to EGCG as a potential agent for the prevention and treatment of neurodegenerative diseases. Fe(III) can accelerate the conformation transition of silk fibrion (SF) from random coil into β-sheet, while (-)-epigallocatechin gallate (EGCG) inhibits Fe(III)-induced β-sheet aggregation of SF., 2016. © 2015 Wiley Periodicals, Inc. Biopolymers 105: 100-107, 2016 [ABSTRACT FROM AUTHOR]

Previously, we screened a proteoglycan for anti-hyperglycemic, named FYGL, from Ganoderma Lucidum. For further research of the antidiabetic mechanisms of FYGL in vivo, the glucose homeostasis, activities of insulin-sensitive enzymes, glucose transporter expression and pancreatic function were analyzed using db/db mice as diabetic models in the present work. FYGL not only lead to a reduction in glycated hemoglobin level, but also an increase in insulin and C-peptide level, whereas a decrease in glucagons level and showed a potential for the remediation of pancreatic islets. FYGL also increased the glucokinase activities, and simultaneously lowered the phosphoenol pyruvate carboxykinase activities, accompanied by a reduction in the expression of hepatic glucose transporter protein 2, while the expression of adipose and skeletal glucose transporter protein 4 was increased. Moreover, the antioxidant enzyme activities were also increased by FYGL treatment. Thus, FYGL was an effective antidiabetic agent by enhancing insulin secretion and decreasing hepatic glucose output along with increase of adipose and skeletal muscle glucose disposal in the late stage of diabetes. Furthermore, FYGL is beneficial against oxidative stress, thereby being helpful in preventing the diabetic complications. [ABSTRACT FROM AUTHOR]