Yifeng Mai

Endothelial Nitric Oxide Synthase Dimerization Is Regulated by Heat Shock Protein 90 Rather than by Phosphorylation

Endothelial nitric oxide synthase (eNOS) is a multifunctional enzyme with roles in diverse cellular processes including angiogenesis, tissue remodeling, and the maintenance of vascular tone. Monomeric and dimeric forms of eNOS exist in various tissues. The dimeric form of eNOS is considered the active form and the monomeric form is considered inactive. The activity of eNOS is also regulated by many other mechanisms, including amino acid phosphorylation and interactions with other proteins. However, the precise mechanisms regulating eNOS dimerization, phosphorylation, and activity remain incompletely characterized. We utilized purified eNOS and bovine aorta endothelial cells (BAECs) to investigate the mechanisms regulating eNOS degradation. Both eNOS monomer and dimer existed in purified bovine eNOS. Incubation of purified bovine eNOS with protein phosphatase 2A (PP2A) resulted in dephosphorylation at Serine 1179 (Ser1179) in both dimer and monomer and decrease in eNOS activity. However, the eNOS dimer∶monomer ratio was unchanged. Similarly, protein phosphatase 1 (PP1) induced dephosphorylation of eNOS at Threonine 497 (Thr497), without altering the eNOS dimer∶monomer ratio. Different from purified eNOS, in cultured BAECs eNOS existed predominantly as dimers. However, eNOS monomers accumulated following treatment with the proteasome inhibitor lactacystin. Additionally, treatment of BAECs with vascular endothelial growth factor (VEGF) resulted in phosphorylation of Ser1179 in eNOS dimers without altering the phosphorylation status of Thr497 in either form. Inhibition of heat shock protein 90 (Hsp90) or Hsp90 silencing destabilized eNOS dimers and was accompanied by dephosphorylation both of Ser1179 and Thr497. In conclusion, our study demonstrates that eNOS monomers, but not eNOS dimers, are degraded by ubiquitination. Additionally, the dimeric eNOS structure is the predominant condition for eNOS amino acid modification and activity regulation. Finally, destabilization of eNOS dimers not only results in eNOS degradation, but also causes changes in eNOS amino acid modifications that further affect eNOS activity.

Elevated CpG island methylation of GCK gene predicts the risk of type 2 diabetes in Chinese males.

BACKGROUND The GCK gene encodes hexokinase 4, which catalyzes the first step in most glucose metabolism pathways. The purpose of our study is to assess the contribution of GCK methylation to type 2 diabetes (T2D). METHODS AND RESULTS GCK methylation was evaluated in 48 T2D cases and 48 age- and gender-matched controls using the bisulphite pyrosequencing technology. Among the four CpG sites in the methylation assay, CpG4 and the other three CpGs (CpG1-3) were not in high correlation (r<0.5). Significantly elevated methylation levels of GCK CpG4 methylation were observed in T2D patients than in the healthy controls (P=0.004). A breakdown analysis by gender indicated that the association between CpG4 methylation and T2D was specific to males (P=0.002). It is intriguing that another significant male-specific association was also found between GCK CpG4 methylation and total cholesterol (TC) concentration (r=0.304, P=0.036). CONCLUSION Our results showed that elevated GCK CpG4 methylation might suggest a risk of T2D in Chinese males. Gender disparity in GCK CpG4 methylation might provide a clue to elaborate the pathogenesis of T2D.

Genetic Associations with Diabetes: Meta-Analyses of 10 Candidate Polymorphisms

Aims The goal of our study is to investigate the combined contribution of 10 genetic variants to diabetes susceptibility. Methods Bibliographic databases were searched from 1970 to Dec 2012 for studies that reported on genetic association study of diabetes. After a comprehensive filtering procedure, 10 candidate gene variants with informative genotype information were collected for the current meta-anlayses. Using the REVMAN software, odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to evaluate the combined contribution of the selected genetic variants to diabetes. Results A total of 37 articles among 37,033 cases and 54,716 controls were involved in the present meta-analyses of 10 genetic variants. Three variants were found to be significantly associated with type 1 diabetes (T1D): NLRP1 rs12150220 (OR = 0.71, 95% CI = 0.55–0.92, P = 0.01), IL2RA rs11594656 (OR = 0.86, 95% CI = 0.82–0.91, P<0.00001), and CLEC16A rs725613 (OR = 0.71, 95% CI = 0.55–0.92, P = 0.01). APOA5 −1131T/C polymorphism was shown to be significantly associated with of type 2 diabetes (T2D, OR = 1.27, 95% CI = 1.03–1.57, P = 0.03). No association with diabetes was showed in the meta-analyses of other six genetic variants, including SLC2A10 rs2335491, ATF6 rs2070150, KLF11 rs35927125, CASQ1 rs2275703, GNB3 C825T, and IL12B 1188A/C. Conclusion Our results demonstrated that IL2RA rs11594656 and CLEC16A rs725613 are protective factors of T1D, while NLRP1 rs12150220 and APOA5 −1131T/C are risky factors of T1D and T2D, respectively.

BCL11A gene DNA methylation contributes to the risk of type 2 diabetes in males

BCL11A is a critical modulator involved in hemoglobin switching. Recent studies have established an association between BCL11A gene polymorphisms and a risk of type 2 diabetes (T2D). The aim of the present study was to assess the correlation between BCL11A DNA methylation and T2D. A total of 48 T2D cases and 48 age- and gender-matched controls were recruited to evaluate BCL11A methylation using bisulfite pyrosequencing technology. Although no significant association was observed in BCL11A methylation between T2D patients and healthy controls (P=0.322), breakdown analysis by gender identified a significant association between BCL11A methylation and T2D in males (P=0.018). Notably, there was also a significant female-specific association between the mean BCL11A DNA methylation and triglyceride (TG) concentration (r=−0.34; P=0.019). The results indicated that BCL11A methylation contributed to the risk of T2D in males. In addition, BCL11A methylation may have an effect on the development of T2D by influencing TG metabolism. Thus, gender difference may provide new information to aid the understanding of T2D pathogenesis.

The effect of environmental factors and DNA methylation on type 2: The effect of environmental factors and DNA methylation on type 2

Type 2 diabetes mellitus (T2DM) is a glucose metabolic disorder driven by both genetic and environmental factors. Recent DNA methylation studies have established that T2DM may be contributed by environmental factors through the regulation of DNA methylation. Human and animal model studies have made much progress on the interaction between DNA methylation of T2DM genes and environmental factors in multiple tissues. Current studies on DNA methylation of T2DM genes mainly focus on glucose and energy metabolism, inflammation, and so on. This review comprehensively introduces the DNA methylation studies for the genes involved in T2DM and its related environmental factors.

Landscape of the relationship between type 2 diabetes and coronary heart disease through an integrated gene network analysis.

Type 2 diabetes (T2D) and coronary artery disease (CAD) are closely related chronic diseases with high prevalence and morbidity. However, a comprehensive comparison of the two diseases is lacking. Recent genome-wide association studies (GWAS) have identified a handful of single nucleotide polymorphisms (SNPs) that are significantly associated with the risk of T2D and CAD. These most significant findings may help interpret the pathogenesis of T2D and CAD. However, tremendous results from these GWAS are ignored. Here we revisited the raw datasets of these GWAS and performed an integrated gene network analysis to unveil the relationship between T2D and CAD by combining multiple datasets including protein-protein interaction (PPI) database, publication libraries, and pathway datasets. Our results showed that majority of genes were involved in the first module (1122 genes in T2D and 895 in CAD). Four pathways were found to be common in both T2D and CAD, including regulation of actin cytoskeleton, calcium signaling pathway, MAPK signaling pathway and focal adhesion (all P<0.00001). MAX which was involved in small cell lung cancer pathway was a hub gene unique to T2D (OR=1.2, P=0.006) but not in CAD. In contrast, three hub genes including PLEKHG5 (T2D: OR=1, P=1; CAD: OR=1.12, P=0.006), TIAM1 (T2D: OR=1, P=1; CAD: OR=1.48, P=0.004) and AKAP13 (T2D: OR=1, P=1; CAD: OR=1.38, P=0.001) were hub genes unique to CAD. Moreover, for some hub genes (such as SMAD3) that were susceptible to both T2D and CAD, their associated polymorphisms were unique to each of the two diseases. Our findings might provide a landscape of the relationship between T2D and CAD.

Meta-analyses between 18 candidate genetic markers and overweight/obesity

AimsThe goal of our study is to investigate the associations between 18 candidate genetic markers and overweight/obesity.MethodsA total of 72 eligible articles were retrieved from literature databases including PubMed, Embase, SpingerLink, Web of Science, Chinese National Knowledge Infrastructure (CNKI), and Wanfang. Meta-analyses of 18 genetic markers among 56,738 controls and 48,148 overweight/obese persons were done by Review Manager 5.0.ResultsOur results showed that SH2B1 rs7498665 polymorphism was significantly associated with the risk of overweight/obesity (overall odds ratio (OR) = 1.21, 95% confidence interval (CI) = 1.09-1.34, P = 0.0004). Increased risk of overweight/obesity was also observed in FAIM2 rs7138803 polymorphism (overall OR = 1.11, 95% CI = 1.01-1.22, P = 0.04).ConclusionOur meta-analyses have shown the important role of 2 polymorphisms (SH2B1 rs7498665 and FAIM2 rs7138803) in the development of overweight/obesity. This study highlighted the importance of above two candidate genes (SH2B1 and FAIM2) in the risk of overweight/obesity.Virtual slidesThe virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/2785487401176182.

Prediabetes Is Associated with HNF-4α P2 Promoter Polymorphism rs1884613: A Case-Control Study in Han Chinese Population and an Updated Meta-Analysis

Background. Controversy remains for the association between hepatocyte nuclear factor 4α (HNF-4α) P2 promoter polymorphism rs1884613 and type 2 diabetes (T2D). There was no association test of this polymorphism with prediabetes and T2D in the Chinese population. Moreover, an updated meta-analysis in various ethnic groups is needed to establish the contribution of rs1884613 to T2D risk. Methods. Using the Sequenom MassARRAY platform approach, we genotyped rs1884613 of HNF-4α in the P2 promoter region among 490 T2D patients, 471 individuals with prediabetes, and 575 healthy controls. All the individuals were recruited from 16 community health service centers in Nanshan district in Shenzhen province. Using STATA 11.0 software, meta-analysis was performed to summarize the overall contribution of rs1884613 to T2D risk. Results. Polymorphism rs1884613 was associated with genetic susceptibility to prediabetes in the whole samples (OR = 1.40, 95% CI = 1.16–1.68, P = 0.0001) and the female subgrouped samples (OR = 1.48, 95% CI = 1.14–1.92, P = 0.003) after adjusting for age and body mass index (BMI). In contrast, there was no association of rs1884613 with T2D in the whole samples and male in our case-control study and meta-analysis. Conclusions. Our results suggest that rs1884613 contributes to susceptibility to prediabetes, whereas this polymorphism may not play an important role in the development of T2D.

Elevation of PTPN1 promoter methylation is a significant risk factor of type 2 diabetes in the Chinese population

The present study aimed to investigate the contribution of DNA methylation of the protein tyrosine phosphatase, non-receptor type 1 (PTPN1) gene to the susceptibility to type 2 diabetes (T2D). Peripheral blood mononuclear cells (PBMCs) were collected from 97 patients with T2D and 97 age- and gender-matched controls. DNA methylation of the PTPN1 gene promoter was evaluated by bisulfite pyrosequencing. Independent sample t-tests were used to compare the differences in the PTPN1 promoter and other phenotypes between the patients with T2D and the controls. The results indicated a significant correlation between PTPN1 promoter methylation and the risk of T2D. Additionally, a breakdown analysis by gender revealed that PTPN1 methylation was associated with an increased risk of T2D in females. Furthermore, low-density lipoprotein (r=−0.183, P=0.046) and total cholesterol (r=−0.310, P=0.001) were inversely associated with PTPN1 methylation in females. In conclusion, the results indicate that elevated PTPN1 promoter methylation is a risk factor for T2D in the female Chinese population.