Background and purposeThe traditional Chinese medicine – the flower of Edgeworthia gardneri – is reported as an effective therapeutic for type 2 diabetes mellitus (T2DM). Nevertheless, most constituents of the flowers of E. gardneri have not yet been studied. This study was conducted to investigate the effect of quercetin extracted from the flowers of E. gardneri on islet protection and amelioration in T2DM and explore its mechanism.MethodQuercetin was extracted from the flowers of E. gardneri and verified by high-performance liquid chromatography. Quercetin or crude extract’s effect on insulin secretion was investigated. ERK1/2 and phospho-ERK1/2 were detected by Western blot analysis, and fluo-3 AM was used to detect intracellular Ca2+. The anti-apoptosis effect of quercetin or crude extract on MIN-6 cells was investigated by thiazolyl blue tetrazolium bromide (MTT) assay and flow cytometry analysis. Activation of caspases and expression of Bcl-2 and BAX were tested by Western blot analysis. In addition, the mitochondrial membrane potential was determined by JC-1 probe. Moreover, in vivo activity was also tested in db/db mice.ResultsA quercetin level of >10 μmol/L could induce insulin secretion. Intracellular Ca2+ and ERK1/2 were involved in the signaling pathway of quercetin-induced insulin secretion. We also observed that quercetin could inhibit palmitic acid-induced cell apoptosis via suppressing the activation of caspase-3, -9, -12; increasing the ratio of Bcl-2/BAX and reversing the impaired mitochondrial membrane potential. Crude extract’s effect on insulin secretion was similar to that of pure extracted quercetin, while it possessed higher anti-apoptosis activity. Additionally, intraperitoneal glucose tolerance, plasma insulin level, hepatic triglyceride, hepatic glycogen and the pathological histology of both pancreatic islet and liver in db/db mice were significantly improved by the administration of the extracted quercetin.ConclusionOur study indicated that quercetin extracted from the flowers of E. gardneri exerted excellent properties in islet protection and amelioration.

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ABSTRACT. To investigate the relationship of polymorphisms in the cholesteryl ester transport protein (CETP) gene with coronary heart disease (CHD) and diabetes in subjects of Uyghur and Han Chinese origin, 266 subjects with CHD including 154 subjects with type 2 diabetes mellitus and 136 healthy subjects (as a control group) were enrolled in this study. Polymerase chain reaction and an enzymatic assay based on the ligase detection reaction were used to detect R451Q polymorphisms in the CETP gene. The data were used for genotyping to determine the allele frequency distribution of the CETP gene R451Q polymorphism to investigate its effects on lipid and apolipoprotein levels. Genotype and allele frequencies of CETP R451QA did not show any significant differences among the CHD and healthy control groups. Moreover, no significant difference in the CETP R451QA genotype and allele frequency was detected among the subjects of Uyghur and Han origin. Blood levels of lipids and apolipoproteins likewise lacked an association with CETP R451QA 955©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 13 (1): 954-962 (2014) R451Q polymorphism and coronary heart disease with diabetes genotype frequencies in the CHD/diabetes group. We conclude that the R451Q polymorphisms in the CETP gene had no effects on blood lipid levels and are not a risk factor for CHD in Han and Uyghur Chinese.