Type 2 diabetes risk allele near CENTD2 is associated with decreased glucose-stimulated insulin release

A critical review on therapeutic approaches of CRISPR-Cas9 in diabetes mellitus

Diabetes mellitus (D.M.) is a common metabolic disorder caused mainly by combining two primary factors, which are (1) defects in insulin production by the pancreatic β-cells and (2) responsiveness of insulin-sensitive tissues towards insulin. Despite the rapid advancement in medicine to suppress elevated blood glucose levels (hyperglycemia) and insulin resistance associated with this hazard, a demand has undoubtedly emerged to find more effective and curative dimensions in therapeutic approaches against D.M. The administration of diabetes treatment that emphasizes insulin production and sensitivity may result in unfavorable side effects, reduced adherence, and potential treatment ineffectiveness. Recent progressions in genome editing technologies, for instance, in zinc-finger nucleases, transcription activator-like effector nucleases, and clustered regularly interspaced short palindromic repeat (CRISPR-Cas)-associated nucleases, have greatly influenced the gene editing technology from concepts to clinical practices. Improvements in genome editing technologies have also opened up the possibility to target and modify specific genome sequences in a cell directly. CRISPR/Cas9 has proven effective in utilizing ex vivo gene editing in embryonic stem cells and stem cells derived from patients. This application has facilitated the exploration of pancreatic beta-cell development and function. Furthermore, CRISPR/Cas9 enables the creation of innovative animal models for diabetes and assesses the effectiveness of different therapeutic strategies in treating the condition. We, therefore, present a critical review of the therapeutic approaches of the genome editing tool CRISPR-Cas9 in treating D.M., discussing the challenges and limitations of implementing this technology.

Biochemical association of regulatory variant of KLF14 genotype in the pathogenesis of cardiodiabetic patients

Background and purpose

The study focuses on examining the relationship between a single nucleotide polymorphism (SNP) in KLF14 rs4731702 and risk of type 2 diabetes mellitus (T2DM) and dyslipidemia in different ethnic populations. The purpose of this study was to evaluate the association between KLF14 rs4731702 and serum lipid profile and to determine the frequency distribution of KLF14 rs4731702 among T2DM and cardiometabolic patients.

Methods

A total of 300 volunteers were recruited, consisting of three groups: 100 healthy individuals, 100 individuals diagnosed with T2DM, and 100 individuals diagnosed with cardiometabolic disorders. Biochemical analysis of blood samples was conducted to assess various biomarkers related to glycemic control and lipid profile. This involved measuring levels of glucose, triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and ApoA1. Genotyping analysis was performed to investigate KLF14 rs4731702 polymorphism. The Tetra ARMS-PCR method was employed for genotyping analysis.

Results

The results of biochemical profiling revealed a significant association between altered glycemic biomarkers and lipid profile in diseased patients compared to healthy participants. The frequencies of KLF14 rs4731702 alleles and genotypes were compared between the control group and T2DM group. A statistically significant difference was observed, indicating a potential association between KLF14 rs4731702 and T2DM. In the dominant inheritance model of KLF14 rs4731702 SNP, a statistically significant difference [odds ratio (95% confidence interval)] of 0.56 (0.34 -0.96) was found between the control and T2DM subjects. This suggests that the presence of certain genotypes influences the risk of T2DM. In T2DM patients, individuals carrying the C allele exhibited compromised insulin sensitivity, decreased HDL-C and ApoA1 levels, and increased serum glucose, TG, and LDL-C concentrations. Conversely, TT genotype carriers demonstrated increased levels of HDL-C and ApoA1, lower insulin resistance, serum glucose, LDL-C, and TG levels.

Conclusion

The study's findings indicate that dyslipidemia in T2DM patients is associated with reduced KLF14 functionality due to CC and CT genotypes, leading to insulin resistance and an increased risk of cardiovascular diseases. Additionally, risk of KLF14 rs4731702 polymorphism was found to increase with age and was more prevalent in female than in male individuals. These insights contribute to understanding genetic factors influencing the development and progression of T2DM and dyslipidemia in different ethnic populations.

The Role of Krüppel-like Factors in Pancreatic Physiology and Pathophysiology

Krüppel-like factors (KLFs) belong to the family of transcription factors with three highly conserved zinc finger domains in the C-terminus. They regulate homeostasis, development, and disease progression in many tissues. It has been shown that KLFs play an essential role in the endocrine and exocrine compartments of the pancreas. They are necessary to maintain glucose homeostasis and have been implicated in the development of diabetes. Furthermore, they can be a vital tool in enabling pancreas regeneration and disease modeling. Finally, the KLF family contains proteins that act as tumor suppressors and oncogenes. A subset of members has a biphasic function, being upregulated in the early stages of oncogenesis and stimulating its progression and downregulated in the late stages to allow for tumor dissemination. Here, we describe KLFs' function in pancreatic physiology and pathophysiology.

Type 2 Diabetes-Related Variants Influence the Risk of Developing Prostate Cancer: A Population-Based Case-Control Study and Meta-Analysis

In this study, we have evaluated whether 57 genome-wide association studies (GWAS)-identified common variants for type 2 diabetes (T2D) influence the risk of developing prostate cancer (PCa) in a population of 304 Caucasian PCa patients and 686 controls. The association of selected single nucleotide polymorphisms (SNPs) with the risk of PCa was validated through meta-analysis of our data with those from the UKBiobank and FinnGen cohorts, but also previously published genetic studies. We also evaluated whether T2D SNPs associated with PCa risk could influence host immune responses by analysing their correlation with absolute numbers of 91 blood-derived cell populations and circulating levels of 103 immunological proteins and 7 steroid hormones. We also investigated the correlation of the most interesting SNPs with cytokine levels after in vitro stimulation of whole blood, peripheral mononuclear cells (PBMCs), and monocyte-derived macrophages with LPS, PHA, Pam3Cys, and Staphylococcus Aureus. The meta-analysis of our data with those from six large cohorts confirmed that each copy of the FTO_rs9939609A, HNF1B_rs7501939T, HNF1B_rs757210T, HNF1B_rs4430796G, and JAZF1_rs10486567A alleles significantly decreased risk of developing PCa (p = 3.70 × 10^-5, p = 9.39 × 10^-54, p = 5.04 × 10^-54, p = 1.19 × 10^-71, and p = 1.66 × 10^-18, respectively). Although it was not statistically significant after correction for multiple testing, we also found that the NOTCH2_rs10923931T and RBMS1_rs7593730 SNPs associated with the risk of developing PCa (p = 8.49 × 10^-4 and 0.004). Interestingly, we found that the protective effect attributed to the HFN1B locus could be mediated by the SULT1A1 protein (p = 0.00030), an arylsulfotransferase that catalyzes the sulfate conjugation of many hormones, neurotransmitters, drugs, and xenobiotic compounds. In addition to these results, eQTL analysis revealed that the HNF1B_rs7501939, HNF1B_rs757210, HNF1B_rs4430796, NOTCH2_rs10923931, and RBMS1_rs7593730 SNPs influence the risk of PCa through the modulation of mRNA levels of their respective genes in whole blood and/or liver. These results confirm that functional TD2-related variants influence the risk of developing PCa, but also highlight the need of additional experiments to validate our functional results in a tumoral tissue context.

Different prevalence of T2DM risk alleles in Roma population in comparison with the majority Czech population

Background

The Czech governmental study suggests up to a 25% higher prevalence of type 2 diabetes mellitus (T2DM) in the Roma population than within the majority population. It is not known whether and to what extent these differences have a genetic background.

Methods

To analyze whether the frequencies of the alleles/genotypes of the FTO, TCF7L2, CDKN2A/2B, MAEA, TLE4, IGF2BP2, ARAP1, and KCNJ11 genes differ between the two major ethnic groups in the Czech Republic, we examined them in DNA samples from 302 Roma individuals and 298 Czech individuals.

Results

Compared to the majority population, Roma are more likely to carry risk alleles in the FTO (26% vs. 16% GG homozygotes, p < .01), IGF2BP2 (22% vs. 10% TT homozygotes, p < .0001), ARAP1 (98% vs. 95% of A allele carriers, p < .005), and CDKN2A/2B (81% vs. 66% of TT homozygotes, p < .001) genes; however, less frequently they are carriers of the TCF7L2 risk allele (34% vs. 48% of the T allele p < .0005). Finally, we found significant accumulation of T2DM‐associated alleles between the Roma population in comparison with the majority population (25.4% vs. 15.2% of the carriers of at least 12 risk alleles; p < .0001).

Conclusion

The increased prevalence of T2DM in the Roma population may have a background in different frequencies of the risk alleles of genes associated with T2DM development.

The type 2 diabetes gene product STARD10 is a phosphoinositide-binding protein that controls insulin secretory granule biogenesis

OBJECTIVE

Risk alleles for type 2 diabetes at the STARD10 locus are associated with lowered STARD10 expression in the β-cell, impaired glucose-induced insulin secretion, and decreased circulating proinsulin:insulin ratios. Although likely to serve as a mediator of intracellular lipid transfer, the identity of the transported lipids and thus the pathways through which STARD10 regulates β-cell function are not understood. The aim of this study was to identify the lipids transported and affected by STARD10 in the β-cell and the role of the protein in controlling proinsulin processing and insulin granule biogenesis and maturation.

METHODS

We used isolated islets from mice deleted selectively in the β-cell for Stard10 (βStard10KO) and performed electron microscopy, pulse-chase, RNA sequencing, and lipidomic analyses. Proteomic analysis of STARD10 binding partners was executed in the INS1 (832/13) cell line. X-ray crystallography followed by molecular docking and lipid overlay assay was performed on purified STARD10 protein.

RESULTS

βStard10KO islets had a sharply altered dense core granule appearance, with a dramatic increase in the number of "rod-like" dense cores. Correspondingly, basal secretion of proinsulin was increased versus wild-type islets. The solution of the crystal structure of STARD10 to 2.3 Å resolution revealed a binding pocket capable of accommodating polyphosphoinositides, and STARD10 was shown to bind to inositides phosphorylated at the 3' position. Lipidomic analysis of βStard10KO islets demonstrated changes in phosphatidylinositol levels, and the inositol lipid kinase PIP4K2C was identified as a STARD10 binding partner. Also consistent with roles for STARD10 in phosphoinositide signalling, the phosphoinositide-binding proteins Pirt and Synaptotagmin 1 were amongst the differentially expressed genes in βStard10KO islets.

CONCLUSION

Our data indicate that STARD10 binds to, and may transport, phosphatidylinositides, influencing membrane lipid composition, insulin granule biosynthesis, and insulin processing.

A Replication Study Identified Seven SNPs Associated with Quantitative Traits of Type 2 Diabetes among Chinese Population in A Cross-Sectional Study

Genome-wide association studies (GWAS) have identified common variants for quantitative traits (insulin resistance and impaired insulin release) of type 2 diabetes (T2D) across different ethnics including China, but results were inconsistent. The study included 1654 subjects who were selected from the 2010–2012 China National Nutrition and Health Surveillance (CNNHS). Insulin resistance and impaired insulin release were assessed by homeostasis model assessment (HOMA). The study included 64 diabetes-related single nucleotide polymorphisms (SNPs), which were done using Mass ARRAY. A logistic regression model was employed to explore the associations of SNPs with insulin resistance and impaired insulin release by correcting for the confounders. The 5q11.2-rs4432842, RASGRP1-rs7403531, and SEC16B-rs574367 increased the risk of insulin resistance with OR = 1.23 (95% CI: 1.04–1.45, OR = 1.35 (95% CI: 1.13–1.62), OR = 1.34 (95% CI: 1.07–1.67), respectively, while MAEA-rs6815464 decreased the risk of insulin resistance (OR = 0.84, 95% CI: 0.71–1.00). CENTD2-rs1552224, TSPAN8-rs7961581 and ANK1-rs516946 was associated with increased risk of impaired insulin release with OR = 1.47 (95% CI: 1.09–1.99), OR = 1.25 (95% CI: 1.03–1.51), OR = 1.39 (95% CI: 1.07–1.81), respectively. Our findings would provide insight into the pathogenesis of individual SNPs and T2D.

Early-onset type 2 diabetes is associated with genetic variants of β-cell function in the Chinese Han population

AIMS

To investigate the genetic factors contributing to early-onset type 2 diabetes (EOD) in the Chinese Hans populations.

MATERIALS AND METHODS

For 2734 newly diagnosed type 2 diabetes patients and 4041 normal glycemic controls, 25 single nucleotide polymorphisms from 24 genomic loci linked to diabetes were successfully genotyped. Three genetic risk scores (GRSs) were constructed, including the weighted type 2 diabetes-related GRS (wT-GRS), the weighted β-cell function-related GRS (wB-GRS), and the weighted GRS constructed by risk alleles not related to β-cell function (wNB-GRS). For patients with diabetes, EOD, middle-age-onset type 2 diabetes (MOD), and late-onset type 2 diabetes (LOD) were defined by onset ages ≤40, 40 to 60, and ≥60 years, respectively.

RESULTS

From single marker analysis, different gene profiles were identified between EOD and LOD patients. EOD patients had greater wT-GRS and wB-GRS values than LOD patients. After adjustment for sex, elevated wT-GRS and wB-GRS values were significantly associated with an increased risk for EOD by 1.11- and 1.21-fold per allele (P = 1.69 × 10^-7 ; 6.07 × 10^-8 ). The wT-GRS and wNB-GRS were nominally related to an increased risk of LOD by 1.03-fold per allele (P = 1.03 × 10^-2 , 1.78 × 10^-2 ). In patients with diabetes, higher wT-GRS and wB-GRS were associated with younger onset age [wT-GRS: β (SE) = -0.0033(0.0016), P = 3.74 × 10^-2 ; wB-GRS: -0.0076(0.0028), 7.45 × 10^-3 ] and decreased insulinogenic index [wT-GRS: -0.0384(0.0098), 9.39 × 10^-5 ; wB-GRS: -0.0722(0.0176), 4.21 × 10^-5 ].

CONCLUSION

Our findings indicate a strong genetic predisposition for EOD, which can be mainly attributed to genetic variants linked to β-cell function, suggesting the β-cell dysfunction plays a key role in the pathogenesis of EOD in Chinese Han individuals.

The effect of lncRNA-ARAP1-AS2/ARAP1 on high glucose-induced cytoskeleton rearrangement and epithelial-mesenchymal transition in human renal tubular epithelial cells

The epithelial-mesenchymal transition (EMT) plays an important role in diabetic renal fibrosis. The ARAP1 gene is located near risk alleles for Type 2 diabetes, and its function has been linked to cytoskeleton rearrangement, Golgi apparatus remodeling, and endocytic trafficking of membrane receptors. The role of ARAP1 and its antisense RNA, ARAP1-AS2, in the pathogenesis of diabetes is unclear. To clarify the roles of ARAP1 and its antisense RNA in diabetes and related complications, we examined if the expression of these transcripts changed under high glucose (HG) conditions. To do this, we examined transcript levels in HK-2 cells, and explored the roles of ARAP1 and ARAP1-AS2 in the EMT process in HK-2 cells. We found increased expression of ARAP1-AS2 and ARAP1 in HK-2 cells under HG condition, and observed that the overexpression of ARAP1-AS2 significantly increased the EMT process. In addition, HG upregulated Cdc42-GTP levels in HK-2 cells, and increased cytoskeleton rearrangement, cell viability, and migration. After knockdown of ARAP1, the level of Cdc42-GTP was decreased; cytoskeleton reorganization, cell viability, and migration processes were decreased; and EMT and expression of fibrosis marker protein. Overall, our results indicated that ARAP1-AS2/ARAP1 may participate in cytoskeleton rearrangement and EMT processes in HK-2 cells through increased Cdc42-GTP levels.

Identifying the association between single nucleotide polymorphisms in KCNQ1, ARAP1, and KCNJ11 and type 2 diabetes mellitus in a Chinese population

Background: Type 2 diabetes mellitus (T2DM) has a high global prevalence, and insufficient insulin secretion is one of the major reasons for its development. Therefore, investigating the association between T2DM and the single nucleotide polymorphisms (SNPs) in genes associated with insulin secretion is necessary. Methods: T2DM (1,194) and nondiabetic (NDM) (1,292) subjects were enrolled and the ten single nucleotide polymorphisms (SNPs) in KCNQ1, ARAP1, and KCNJ11 associated with insulin secretion were genotyped in a Chinese population. Results: Our data revealed that the rs2237897T allele in KCNQ1 is the protective allele for T2DM (P<0.001, OR=0.793; 95%CI: 0.705-0.893). However, the A allele of rs1552224 in ARAP1 may be a risk factor for T2DM (P=0.002, OR=12.070; 95% CI: 1.578-92.337). The haplotype analysis revealed that rs151290-rs2237892CC and rs2237895-rs2237897CC in KCNQ1 constitute the risk haplotype in T2DM development (P=0.010, OR=1.160; 95% CI: 1.037-1.299 and P=0.004, OR=1.192; 95% CI: 1.057-1.344). Moreover, rs2237895-rs2237897AT in KCNQ1 constitutes the protective haplotype in T2DM (P=0.001, OR=0.819; 95% CI: 0.727-0.923). In the inheritance models analysis, the rs2283228 (C/A-C/C) genotype is the protective factor compared to the A/A genotype (P=0.005, OR=0.79; 95% CI: 0.68-0.93). For rs2237897, the C/T-T/T genotype is the protective factor compared to the C/C genotype (P<0.001, OR=0.74; 95% CI: 0.63-0.87). Furthermore, when compared with the rs2237897 (C/T-T/T) genotype, rs2237897C/C genotype showed higher HbA1C levels (8.731±2.697 vs 9.282±2.921, P=0.001). Conclusion: Our results revealed that genetic variations in KCNQ1 and ARAP1 were associated with T2DM susceptibility in a Chinese population.

The Krüppel-Like Factors and Control of Energy Homeostasis

Nutrient handling by higher organisms is a complex process that is regulated at the transcriptional level. Studies over the past 15 years have highlighted the critical importance of a family of transcriptional regulators termed the Krüppel-like factors (KLFs) in metabolism. Within an organ, distinct KLFs direct networks of metabolic gene targets to achieve specialized functions. This regulation is often orchestrated in concert with recruitment of tissue-specific transcriptional regulators, particularly members of the nuclear receptor family. Upon nutrient entry into the intestine, gut, and liver, KLFs control a range of functions from bile synthesis to intestinal stem cell maintenance to effect nutrient acquisition. Subsequently, coordinated KLF activity across multiple organs distributes nutrients to sites of storage or liberates them for use in response to changes in nutrient status. Finally, in energy-consuming organs like cardiac and skeletal muscle, KLFs tune local metabolic programs to precisely match substrate uptake, flux, and use, particularly via mitochondrial function, with energetic demand; this is achieved in part via circulating mediators, including glucocorticoids and insulin. Here, we summarize current understanding of KLFs in regulation of nutrient absorption, interorgan circulation, and tissue-specific use.

LncRNA DGCR5 represses the development of hepatocellular carcinoma by targeting the miR-346/KLF14 axis

Long non-coding RNAs (lncRNAs) are a class of regulatory noncoding RNAs. Emerging evidence highlights the critical roles of lncRNAs in the progression of hepatocellular carcinoma (HCC). Although many lncRNAs have been identified in the development of HCC, the association between DiGeorge syndrome critical region gene 5 (DGCR5) and HCC remains unclear. In the current study, we focused on the biological role of DGCR5 in HCC. We observed that DGCR5 was decreased in HCC cells, including SMCC7721, Hep3B, HepG2, MHCC-97L, MHCC-97H, and SNU449 hepatocellular carcinoma cells, compared with the normal human liver cell line THLE-3 normal human liver cells. In addition, DGCR5 overexpression could repress HCC cell growth, migration, and invasion considerably. Increasing studies have indicated the interactions between lncRNAs and microRNAs. MicroRNAs are endogenous small noncoding RNAs and they can play important roles in tumorigenesis. MicroRNA 346 (miR-346) has been demonstrated in various human cancer types, including HCC. MiR-346 was found to be increased in HCC cells and DGCR5 can act as a sponge of miR-346 to modulate the progression of HCC. The binding correlation between DGCR5 and miR-346 was validated in our research. Subsequently, Krüppel-like factor 14 (KLF14) was predicted as a downstream target of miR-346 and miR-346 can induce the development of HCC by inhibiting KLF14. Finally, we proved that DGCR5 can rescue the inhibited levels of KLF14 repressed by miR-346 mimics in MHCC-97H and Hep3B cells. Taken together, it was indicated in our study that DGCR5 can restrain the progression of HCC through sponging miR-346 and modulating KLF14 in vitro.

A common variant within the HNF1B gene is associated with overall survival of multiple myeloma patients: results from the IMMEnSE consortium and meta-analysis

Diabetogenic single nucleotide polymorphisms (SNPs) have recently been associated with multiple myeloma (MM) risk but their impact on overall survival (OS) of MM patients has not been analysed yet. In order to investigate the impact of 58 GWAS-identified variants for type 2 diabetes (T2D) on OS of patients with MM, we analysed genotyping data of 936 MM patients collected by the International Multiple Myeloma rESEarch (IMMENSE) consortium and an independent set of 700 MM patients recruited by the University Clinic of Heidelberg. A meta-analysis of the cox regression results of the two sets showed that rs7501939 located in the HNF1B gene negatively impacted OS (HRRec= 1.44, 95% CI = 1.18-1.76, P = 0.0001). The meta-analysis also showed a noteworthy gender-specific association of the SLC30A8rs13266634 SNP with OS. The presence of each additional copy of the minor allele at rs13266634 was associated with poor OS in men whereas no association was seen in women (HRMen-Add = 1.32, 95% CI 1.13-1.54, P = 0.0003). In conclusion, these data suggest that the HNF1Brs7501939 SNP confers poor OS in patients with MM and that a SNP in SLC30A8 affect OS in men.

The KLF14 transcription factor regulates hepatic gluconeogenesis in mice

Krüppel-like factor 14 (KLF14) is a member of the Cys₂/His₂ zinc-finger DNA-binding proteins. Despite strong evidence showing that a polymorphism in the Klf14 gene is closely linked to the development of type 2 diabetes, the physiological and metabolic functions of KLF14 still remain unclear. In the present study, we investigated the role of KLF14 in the regulation of hepatic gluconeogenesis. Adenoviruses expressing KLF14 (Ad-Klf14) or KLF14-specific shRNAs (Ad-shKlf14) were injected into normal C57BL/6J, db/db diabetic, or high-fat diet-induced obese (DIO) mice. Gene expression, hepatic glucose production, glucose tolerance, and insulin resistance were tested in C57BL/6J, db/db, and DIO mice and primary hepatocytes. Our results demonstrate that KLF14 expression is induced in the livers of normal C57BL/6J mice upon fasting and significantly up-regulated in the livers of db/db mice, suggesting a physiological link between KLF14 and gluconeogenesis. Adenovirus-mediated overexpression of KLF14 in primary hepatocytes increased both the mRNA and protein levels of peroxisome proliferator-activated receptor-γ coactivator 1α (Pgc-1α, also known as Ppargc1a), thereby stimulating cellular glucose production. Conversely, knockdown of KLF14 expression led to a reduction in PGC-1α, subsequently inhibiting glucose output in primary hepatocytes. Finally, forced expression of KLF14 in the livers of normal mice increased the plasma glucose levels and impaired glucose tolerance; in contrast, KLF14 knockdown in diabetic mouse livers improved glucose tolerance. Taken together, our data strongly indicate that KLF14 modulates hepatic gluconeogenesis.

Prioritising Causal Genes at Type 2 Diabetes Risk Loci

PURPOSE OF REVIEW

Genome-wide association studies (GWAS) for type 2 diabetes (T2D) risk have identified a large number of genetic loci associated with disease susceptibility. However, progress moving from association signals through causal genes to functional understanding has so far been slow, hindering clinical translation. This review discusses the benefits and limitations of emerging, unbiased approaches for prioritising causal genes at T2D risk loci.

RECENT FINDINGS

Candidate causal genes can be identified by a number of different strategies that rely on genetic data, genomic annotations, and functional screening of selected genes. To overcome the limitations of each particular method, integration of multiple data sets is proving essential for establishing confidence in the prioritised genes. Previous studies have also highlighted the need to support these efforts through identification of causal variants and disease-relevant tissues. Prioritisation of causal genes at T2D risk loci by integrating complementary lines of evidence promises to accelerate our understanding of disease pathology and promote translation into new therapeutics.

Genetic variants and clinical relevance associated with gestational diabetes mellitus in Chinese women: a case-control study

PURPOSE

Gestational diabetes mellitus (GDM) may share similar mechanisms with type 2 diabetes and obesity. In the current study, we aimed to verify twenty genes reported to be associated with type 2 diabetes and obesity in the Chinese GDM population.

METHODS

Pregnant women aged 20-49 years at 24-28 gestational weeks were recruited and 556 cases and 445 controls were enrolled in the study. The genotyping of single nucleotide polymorphisms (SNPs) was performed on peripheral blood samples.

RESULTS

We discovered that GDM was associated with rs945508 (OR = 1.368, 95% CI = 1.080-1.732, p = .009), rs10804591 (OR = 1.446, 95% CI = 1.192-1.754, p < .001), rs10245353 (OR = 1.204, 95% CI = 1.006-1.441, p = .043) and rs1552224 (OR = 1.451, 95% CI = 1.071-1.964, p = .016).

CONCLUSIONS

We found that four SNPs associated with type 2 diabetes and obesity may also increase the risk of developing GDM in the Chinese population. Among these SNPs, we report for the first time that rs945508 in ARHGEF11, rs10804591 in PLXND1 and rs10245353 in NFE2L3 were associated with GDM.

Decreased STARD10 Expression Is Associated with Defective Insulin Secretion in Humans and Mice

Genetic variants near ARAP1 (CENTD2) and STARD10 influence type 2 diabetes (T2D) risk. The risk alleles impair glucose-induced insulin secretion and, paradoxically but characteristically, are associated with decreased proinsulin:insulin ratios, indicating improved proinsulin conversion. Neither the identity of the causal variants nor the gene(s) through which risk is conferred have been firmly established. Whereas ARAP1 encodes a GTPase activating protein, STARD10 is a member of the steroidogenic acute regulatory protein (StAR)-related lipid transfer protein family. By integrating genetic fine-mapping and epigenomic annotation data and performing promoter-reporter and chromatin conformational capture (3C) studies in β cell lines, we localize the causal variant(s) at this locus to a 5 kb region that overlaps a stretch-enhancer active in islets. This region contains several highly correlated T2D-risk variants, including the rs140130268 indel. Expression QTL analysis of islet transcriptomes from three independent subject groups demonstrated that T2D-risk allele carriers displayed reduced levels of STARD10 mRNA, with no concomitant change in ARAP1 mRNA levels. Correspondingly, β-cell-selective deletion of StarD10 in mice led to impaired glucose-stimulated Ca²⁺ dynamics and insulin secretion and recapitulated the pattern of improved proinsulin processing observed at the human GWAS signal. Conversely, overexpression of StarD10 in the adult β cell improved glucose tolerance in high fat-fed animals. In contrast, manipulation of Arap1 in β cells had no impact on insulin secretion or proinsulin conversion in mice. This convergence of human and murine data provides compelling evidence that the T2D risk associated with variation at this locus is mediated through reduction in STARD10 expression in the β cell.

Type 2 Diabetes Risk Allele UBE2E2 Is Associated With Decreased Glucose-Stimulated Insulin Release in Elderly Chinese Han Individuals

Recently, rs163182 in KCNQ1, rs7612463 in UBE2E2, rs7119 in HMG20A, and rs6815464 in MAEA were discovered as type 2 diabetes (T2D) loci unique to Asians, and rs13342692 in SLC16A11 were newly reported as T2D loci in multiethnicities by genome-wide association (GWA) studies. The aim of the present study is to ascertain the potential associations between these variants and T2D risk in the Chinese population, and characterize diabetic-related quantitative traits underlying these variants.A total of 4268 Chinese Han individuals (1754 patients with T2D and 2514 glucose-tolerant health subjects, age ≥40 years) were genotyped for these 5 variants. All the health individuals underwent an oral glucose tolerance test (OGTT), and measures of insulin release and sensitivity were estimated from insulinogenic, BIGTT, Matsuda, and disposition indices. The associations were determined by using logistic regression analysis.After adjustment for age, sex, and BMI, rs163182 in KCNQ1 (P = 0.002) and rs7612463 in UBE2E2 (P = 0.024) were found to be associated with T2D risk in Chinese Han population. The risk C allele of rs7612463 in UBE2E2 is associated with decreased IGI (P = 0.001), BIGTT-AIR (P = 0.002), CIR (P = 0.002), and DI (P = 0.006). The other 4 variants did not associate with insulin release or sensitivity.UBE2E2 rs7612463 may mediate its diabetogenic impact on insulin response, which highly depends on the impairment of β-cell function.

Allosteric properties of PH domains in Arf regulatory proteins

Pleckstrin Homology (PH) domains bind phospholipids and proteins. They are critical regulatory elements of a number enzymes including guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs) for Ras-superfamily guanine nucleotide binding proteins such as ADP-ribosylation factors (Arfs). Recent studies have indicated that many PH domains may bind more than one ligand cooperatively. Here we discuss the molecular basis of PH domain-dependent allosteric behavior of 2 ADP-ribosylation factor exchange factors, Grp1 and Brag2, cooperative binding of ligands to the PH domains of Grp1 and the Arf GTPase-activating protein, ASAP1, and the consequences for activity of the associated catalytic domains.

Type 2 diabetes-related variants influence the risk of developing multiple myeloma: results from the IMMEnSE consortium

Type 2 diabetes (T2D) has been suggested to be a risk factor for multiple myeloma (MM), but the relationship between the two traits is still not well understood. The aims of this study were to evaluate whether 58 genome-wide-association-studies (GWAS)-identified common variants for T2D influence the risk of developing MM and to determine whether predictive models built with these variants might help to predict the disease risk. We conducted a case-control study including 1420 MM patients and 1858 controls ascertained through the International Multiple Myeloma (IMMEnSE) consortium. Subjects carrying the KCNQ1rs2237892T allele or the CDKN2A-2Brs2383208G/G, IGF1rs35767T/T and MADDrs7944584T/T genotypes had a significantly increased risk of MM (odds ratio (OR)=1.32-2.13) whereas those carrying the KCNJ11rs5215C, KCNJ11rs5219T and THADArs7578597C alleles or the FTOrs8050136A/A and LTArs1041981C/C genotypes showed a significantly decreased risk of developing the disease (OR=0.76-0.85). Interestingly, a prediction model including those T2D-related variants associated with the risk of MM showed a significantly improved discriminatory ability to predict the disease when compared to a model without genetic information (area under the curve (AUC)=0.645 vs AUC=0.629; P=4.05×10(-) (06)). A gender-stratified analysis also revealed a significant gender effect modification for ADAM30rs2641348 and NOTCH2rs10923931 variants (Pinteraction=0.001 and 0.0004, respectively). Men carrying the ADAM30rs2641348C and NOTCH2rs10923931T alleles had a significantly decreased risk of MM whereas an opposite but not significant effect was observed in women (ORM=0.71 and ORM=0.66 vs ORW=1.22 and ORW=1.15, respectively). These results suggest that TD2-related variants may influence the risk of developing MM and their genotyping might help to improve MM risk prediction models.

The stress protein TP53INP1 plays a tumor suppressive role by regulating metabolic homeostasis

In the recent years, we have provided evidence that Tumor Protein 53-Induced Nuclear Protein 1 (TP53INP1) is a key stress protein with antioxidant-associated tumor suppressive function. The TP53INP1 gene, which is highly conserved in mammals, is over-expressed during stress responses including inflammation. This gene encodes two protein isoforms with nuclear or cytoplasmic subcellular localization depending on the context. TP53INP1 contributes to stress responses, thus preventing stress-induced dysfunctions leading to pathologies such as cancer. Two major mechanisms by which TP53INP1 functions have been unveiled. First, in the nucleus, TP53INP1 was shown to regulate the transcriptional activity of p53 and p73 by direct interaction, and to mediate the antioxidant activity of p53. Second, independently of p53, TP53INP1 contributes to autophagy and more particularly mitophagy through direct interaction with molecular actors of autophagy. TP53INP1 is thus required for the homeostasis of the mitochondrial compartment, and is therefore involved in the regulation of energetic metabolism. Finally, the antioxidant function of TP53INP1 stems from the control of mitochondrial reactive oxygen species production. In conclusion, TP53INP1 is a multifaceted protein endowed with multiple functions, including metabolic regulation, as is its main functional partner p53.

Joint effect of CENTD2 and KCNQ1 polymorphisms on the risk of type 2 diabetes mellitus among Chinese Han population

Genome-wide association studies (GWAS) in populations of European ancestry have identified nine single nuclear polymorphisms (SNP) on chromosome 11 related to type 2 diabetes (T2D) susceptibility. Herein, we further evaluate the association of these SNPs and T2D in a Chinese Han population. We performed a case-control study of 2925 T2D cases and 3281 controls to evaluate the association of five SNPs of KCNJ11, MTNR1B, CENTD2 and LOC387761 and T2D in addition to the previously reported four SNPs of KCNQ1. Multiple logistic regression was used to evaluate SNP's effect by adjustment for confounding factor age, sex and BMI. In the first stage, SNPs rs1552224 at CENTD2 were significantly associated with T2D and the association was statistically significant in the whole study population (P = 0.001) although it was not replicated in the second stage. rs1552224 and rs2237897 of KCNQ1 showed significant joint effect on T2D and there was a significant decreased risk of T2D with the number increase of risk alleles (P for trend = 3.81 × 10(-17)). Compared to those without carrying any risk allele, individuals carrying one, two, and three or four risk alleles had a 30.7%, 44.8% and 62.0% decreased risk for developing T2D, respectively. Our finding suggests that genetic variant rs1552224 of CENTD2 on chromosome 11 contributes to an independent effect as well as joint cumulative effect with rs2237897 of KCNQ1 on the risk of T2D in Chinese Han population, and further functional research would be warranted.

Genetic determinants for gestational diabetes mellitus and related metabolic traits in Mexican women

Epidemiological and physiological similarities among Gestational Diabetes Mellitus (GDM) and Type 2 Diabetes (T2D) suggest that both diseases, share a common genetic background. T2D risk variants have been associated to GDM susceptibility. However, the genetic architecture of GDM is not yet completely understood. We analyzed 176 SNPs for 115 loci previously associated to T2D, GDM and body mass index (BMI), as well as a set of 118 Ancestry Informative Markers (AIMs), in 750 pregnant Mexican women. Association with GDM was found for two of the most frequently replicated T2D loci: a TCF7L2 haplotype (CTTC: rs7901695, rs4506565, rs7903146, rs12243326; P=2.16x10^-06; OR=2.95) and a KCNQ1 haplotype (TTT: rs2237892, rs163184, rs2237897; P=1.98x10^-05; OR=0.55). In addition, we found two loci associated to glycemic traits: CENTD2 (60’ OGTT glycemia: rs1552224, P=0.03727) and MTNR1B (HOMA B: rs1387153, P=0.05358). Remarkably, a major susceptibility SLC16A11 locus for T2D in Mexicans was not shown to play a role in GDM risk. The fact that two of the main T2D associated loci also contribute to the risk of developing GDM in Mexicans, confirm that both diseases share a common genetic background. However, lack of association with a Native American contribution T2D risk haplotype, SLC16A11, suggests that other genetic mechanisms may be in play for GDM.

Cumulative effect and predictive value of genetic variants associated with type 2 diabetes in Han Chinese: a case-control study

Background

Genome-wide association studies (GWAS) have identified dozens of single nucleotide polymorphisms (SNPs) associated with type 2 diabetes risk. We have previously confirmed the associations of genetic variants in HHEX, CDKAL1, VEGFA and FTO with type 2 diabetes in Han Chinese. However, the cumulative effect and predictive value of these GWAS identified SNPs on the risk of type 2 diabetes in Han Chinese are largely unknown.

Methodology/Principal Findings

We conducted a two-stage case-control study consisting of 2,925 cases and 3,281controls to examine the association of 30 SNPs identified by GWAS with type 2 diabetes in Han Chinese. Significant associations were found for proxy SNPs at KCNQ1 [odds ratio (OR) = 1.41, P = 9.91 × 10–16 for rs2237897], CDKN2A/CDKN2B (OR = 1.30, P = 1.34 × 10–10 for rs10811661), CENTD2 (OR = 1.28, P = 9.88 × 10-4 for rs1552224) and SLC30A8 (OR = 1.19, P = 1.43 × 10-5 for rs13266634). We further evaluated the cumulative effect on type 2 diabetes of these 4 SNPs, in combination with 5 SNPs at HHEX, CDKAL1, VEGFA and FTO reported previously. Individuals carrying 12 or more risk alleles had a nearly 4-fold increased risk for developing type 2 diabetes compared with those carrying less than 6 risk alleles [adjusted OR = 3.68, 95% confidence interval (CI): 2.76–4.91]. Adding the genetic factors to clinical factors slightly improved the prediction of type 2 diabetes, with the area under the receiver operating characteristic curve increasing from 0.76 to 0.78. However, the difference was statistically significant (P < 0.0001).

Conclusions/Significance

We confirmed associations of SNPs in KCNQ1, CDKN2A/CDKN2B, CENTD2 and SLC30A8 with type 2 diabetes in Han Chinese. The utilization of genetic information may improve the accuracy of risk prediction in combination with clinical characteristics for type 2 diabetes.

Impact of type 2 diabetes susceptibility variants on quantitative glycemic traits reveals mechanistic heterogeneity

Patients with established type 2 diabetes display both β-cell dysfunction and insulin resistance. To define fundamental processes leading to the diabetic state, we examined the relationship between type 2 diabetes risk variants at 37 established susceptibility loci, and indices of proinsulin processing, insulin secretion, and insulin sensitivity. We included data from up to 58,614 nondiabetic subjects with basal measures and 17,327 with dynamic measures. We used additive genetic models with adjustment for sex, age, and BMI, followed by fixed-effects, inverse-variance meta-analyses. Cluster analyses grouped risk loci into five major categories based on their relationship to these continuous glycemic phenotypes. The first cluster (PPARG, KLF14, IRS1, GCKR) was characterized by primary effects on insulin sensitivity. The second cluster (MTNR1B, GCK) featured risk alleles associated with reduced insulin secretion and fasting hyperglycemia. ARAP1 constituted a third cluster characterized by defects in insulin processing. A fourth cluster (TCF7L2, SLC30A8, HHEX/IDE, CDKAL1, CDKN2A/2B) was defined by loci influencing insulin processing and secretion without a detectable change in fasting glucose levels. The final group contained 20 risk loci with no clear-cut associations to continuous glycemic traits. By assembling extensive data on continuous glycemic traits, we have exposed the diverse mechanisms whereby type 2 diabetes risk variants impact disease predisposition.

Genetics of type 2 diabetes: insights into the pathogenesis and its clinical application

With rapidly increasing prevalence, diabetes has become one of the major causes of mortality worldwide. According to the latest studies, genetic information makes substantial contributions towards the prediction of diabetes risk and individualized antidiabetic treatment. To date, approximately 70 susceptibility genes have been identified as being associated with type 2 diabetes (T2D) at a genome-wide significant level (P < 5 × 10⁻⁸). However, all the genetic loci identified so far account for only about 10% of the overall heritability of T2D. In addition, how these novel susceptibility loci correlate with the pathophysiology of the disease remains largely unknown. This review covers the major genetic studies on the risk of T2D based on ethnicity and briefly discusses the potential mechanisms and clinical utility of the genetic information underlying T2D.

A common functional regulatory variant at a type 2 diabetes locus upregulates ARAP1 expression in the pancreatic beta cell

Genome-wide association studies (GWASs) have identified more than 70 loci associated with type 2 diabetes (T2D), but for most, the underlying causal variants, associated genes, and functional mechanisms remain unknown. At a T2D- and fasting-proinsulin-associated locus on 11q13.4, we have identified a functional regulatory DNA variant, a candidate target gene, and a plausible underlying molecular mechanism. Fine mapping, conditional analyses, and exome array genotyping in 8,635 individuals from the Metabolic Syndrome in Men study confirmed a single major association signal between fasting proinsulin and noncoding variants (p = 7.4 × 10(-50)). Measurement of allele-specific mRNA levels in human pancreatic islet samples heterozygous for rs11603334 showed that the T2D-risk and proinsulin-decreasing allele (C) is associated with increased ARAP1 expression (p < 0.02). We evaluated four candidate functional SNPs for allelic effects on transcriptional activity by performing reporter assays in rodent pancreatic beta cell lines. The C allele of rs11603334, located near one of the ARAP1 promoters, exhibited 2-fold higher transcriptional activity than did the T allele (p < 0.0001); three other candidate SNPs showed no allelic differences. Electrophoretic mobility shift assays demonstrated decreased binding of pancreatic beta cell transcriptional regulators PAX6 and PAX4 to the rs11603334 C allele. Collectively, these data suggest that the T2D-risk allele of rs11603334 could abrogate binding of a complex containing PAX6 and PAX4 and thus lead to increased promoter activity and ARAP1 expression in human pancreatic islets. This work suggests that increased ARAP1 expression might contribute to T2D susceptibility at this GWAS locus.

Exome sequencing and genetic testing for MODY

CONTEXT

Genetic testing for monogenic diabetes is important for patient care. Given the extensive genetic and clinical heterogeneity of diabetes, exome sequencing might provide additional diagnostic potential when standard Sanger sequencing-based diagnostics is inconclusive.

OBJECTIVE

The aim of the study was to examine the performance of exome sequencing for a molecular diagnosis of MODY in patients who have undergone conventional diagnostic sequencing of candidate genes with negative results.

RESEARCH DESIGN AND METHODS

We performed exome enrichment followed by high-throughput sequencing in nine patients with suspected MODY. They were Sanger sequencing-negative for mutations in the HNF1A, HNF4A, GCK, HNF1B and INS genes. We excluded common, non-coding and synonymous gene variants, and performed in-depth analysis on filtered sequence variants in a pre-defined set of 111 genes implicated in glucose metabolism.

RESULTS

On average, we obtained 45 X median coverage of the entire targeted exome and found 199 rare coding variants per individual. We identified 0-4 rare non-synonymous and nonsense variants per individual in our a priori list of 111 candidate genes. Three of the variants were considered pathogenic (in ABCC8, HNF4A and PPARG, respectively), thus exome sequencing led to a genetic diagnosis in at least three of the nine patients. Approximately 91% of known heterozygous SNPs in the target exomes were detected, but we also found low coverage in some key diabetes genes using our current exome sequencing approach. Novel variants in the genes ARAP1, GLIS3, MADD, NOTCH2 and WFS1 need further investigation to reveal their possible role in diabetes.

CONCLUSION

Our results demonstrate that exome sequencing can improve molecular diagnostics of MODY when used as a complement to Sanger sequencing. However, improvements will be needed, especially concerning coverage, before the full potential of exome sequencing can be realized.

Genetic determinants of glucose homeostasis

Type 2 diabetes is a complex metabolic disorder characterised by varying degrees of impairment in insulin secretion and resistance to the action of insulin. Considerable progress has been made recently in understanding the genetic determinants of diabetes. A logical next step is to describe how these variants relate to the underlying pathophysiological processes that lead to diabetes as this may provide insights into pathways to disease. These quantitative traits are, of course, of direct interest in themselves and a growing literature is now emerging on the genetic determinants of insulin secretion and insulin resistance. This review article focuses on describing the complex associations between type 2 diabetes risk variants and quantitative glycaemic traits and the relationship between variants initially discovered in association studies of these traits and risk of type 2 diabetes.