Inhibition of histone acetyltransferase by naringenin and hesperetin suppresses Txnip expression and protects pancreatic ß cells in diabetic mice.

BACKGROUND: The damage of pancreatic ß cells is a major pathogenesis of the development and progression of type 2 diabetes and there is still no effective therapy to protect pancreatic ß cells clinically. In our previous study, we found that Quzhou Fructus Aurantii (QFA), which is rich in flavanones, had the protective effect of pancreatic ß cells in diabetic mice. However, the underlying mechanism is still unclear. PURPOSE: In the current study, we administered naringenin and hesperetin, two major active components of QFA, to protect pancreatic ß cells and to investigate the underlying molecular mechanism focusing on the epigenetic modifications. METHODS: We used diabetic db/db mouse and INS-1 pancreatic ß cell line as in vivo and in vitro models to investigate the protective effect of naringenin and hesperetin on pancreatic ß cells under high glucose environment and the related mechanism. The phenotypic changes were evaluatedby immunostaining and the measurement of biochemical indexes. The molecular mechanism was explored by biological techniques such as western blotting, qPCR, ChIP-seq and ChIP-qPCR, flow cytometry and lentivirus infection. RESULTS: We found that naringenin and hesperetin had an inhibitory effect on histone acetylation. We showed that naringenin and hesperetin protected pancreatic ß cells in vivo and in vitro, and this effect was independent of their direct antioxidant capacity. The further study found that the inhibition of thioredoxin-interacting protein (Txnip) expression regulated by histone acetylation was critical for the protective role of naringenin and hesperetin. Mechanistically, the histone acetylation inhibition by naringenin and hesperetin was achieved through regulating AMPK-mediated p300 inactivation. CONCLUSION: These findings highlight flavanones and the phytomedicine rich in flavanones as important dietary supplements in protecting pancreatic ß cells in advanced diabetes. In addition, targeting histone acetylation by phytomedicine is a potential strategy to delay the development and progression of diabetes.

Variations in arsenic methylation capacity and oxidative DNA lesions over a 2-year period in a high arsenic-exposed population.

OBJECTIVE: To assess long-term variations in arsenic methylation and oxidative DNA lesions of chronic high arsenic-exposed populations. METHODS: A follow-up study was conducted in 64 chronic high arsenic-exposed subjects from 2004 to 2006. Urinary arsenic species and 8-hydroxydeoxyguanine were measured. RESULTS: Percentages of urinary inorganic arsenic, monomethylarsonate and urinary 8-hydroxydeoxyguanine (8-OHdG) level were significantly higher, but the percentage of dimethylarsinate, the primary methylation index (PMI) and secondary methylation index (SMI) was lower in the ninth year of arsenic exposure compared with the seventh year. Substantial differences in relative arsenic methylation capacity were observed between the seventh and ninth year. Percentages of arsenic species, PMI and SMI were significantly correlated between siblings, and between parents and children. CONCLUSIONS: Arsenic methylation may decrease, but oxidative DNA lesions may increase with the increase of cumulative arsenic exposure level. Both genetic and environmental factors may contribute to variability in arsenic methylation.