Genome-wide association study in a Chinese population identifies a susceptibility locus for type 2 diabetes at 7q32 near PAX4

Young-onset type 2 diabetes-Epidemiology, pathophysiology, and management

The prevalence and incidence of young-onset type 2 diabetes is increasing globally, especially in low- and middle-income countries, and predominantly affects non-White ethnic and racial populations. Young-onset type 2 is heterogeneous in terms of the genetic and environmental contributions to its underlying pathophysiology, which poses challenges for glycemic management. Young at-risk individuals remain underrepresented in clinical trials, including diabetes prevention studies, and there is still an insufficient evidence base to inform practice for this age group. Improvements in diabetes care delivery have not reached young people who will progress to have disabling complications at an age when they are most productive. This review summarizes recent studies on the epidemiology of young-onset type 2 diabetes and its complications. We discuss the genetic and environmental risk factors that act in concert to promote glycemic dysregulation and early onset of type 2 diabetes. We provide perspectives on diabetes prevention and management, and propose strategies to address the unique medical and psychosocial issues associated with young-onset type 2 diabetes. The Precision Medicine to Redefine Insulin Secretion and Monogenic Diabetes Randomized Controlled Trial (PRISM-RCT) is the first large-scale clinical trial designed to evaluate the effect of a structured care model that integrates biogenetic markers with communication and information technology on attaining strict metabolic targets and improving clinical outcomes in individuals with young-onset type 2 diabetes. The results of this study will inform the scientific community about the impact of multifactorial intervention and precision care in young patients, for whom the legacy effect is particularly significant.

Exploring the genomic and transcriptomic profiles of glycemic traits and drug repurposing

BACKGROUND

Type 2 diabetes is an increasingly prevalent metabolic disorder with moderate to high heritability. Glycemic indices are crucial for diagnosing and monitoring the disease. Previous genome-wide association study (GWAS) have identified several risk loci associated with type 2 diabetes, but data from the Taiwanese population remain relatively sparse and primarily focus on type 2 diabetes status rather than glycemic trait levels.

METHODS

We conducted a comprehensive genome-wide meta-analysis to explore the genetics of glycemic traits. The study incorporated a community-based cohort of 145,468 individuals and a hospital-based cohort of 35,395 individuals. The study integrated genetics, transcriptomics, biological pathway analyses, polygenic risk score calculation, and drug repurposing for type 2 diabetes.

RESULTS

This study assessed hemoglobin A1c and fasting glucose levels, validating known loci (FN3K, SPC25, MTNR1B, and FOXA2) and discovering new genes, including MAEA and PRC1. Additionally, we found that diabetes, blood lipids, and liver- and kidney-related traits share genetic foundations with glycemic traits. A higher PRS was associated with an increased risk of type 2 diabetes. Finally, eight repurposed drugs were identified with evidence to regulate blood glucose levels, offering new avenues for the management and treatment of type 2 diabetes.

CONCLUSIONS

This research illuminates the unique genetic landscape of glucose regulation in Taiwanese Han population, providing valuable insights to guide future treatment strategies for type 2 diabetes.

A polygenic risk score derived from common variants of monogenic diabetes genes is associated with young-onset type 2 diabetes and cardiovascular-kidney complications

AIMS/HYPOTHESIS

Monogenic diabetes is caused by rare mutations in genes usually implicated in beta cell biology. Common variants of monogenic diabetes genes (MDG) may jointly influence the risk of young-onset type 2 diabetes (YOD, diagnosed before the age of 40 years) and cardiovascular and kidney events.

METHODS

Using whole-exome sequencing data, we constructed a weighted polygenic risk score (wPRS) consisting of 135 common variants (minor allele frequency >0.01) of 34 MDG based on r2>0.2 for linkage disequilibrium in a discovery case-control cohort of 453 adults with YOD (median [IQR] age 39.7 [34.9-46.9] years) and 405 without YOD (median [IQR] age 56.7 [50.3-61.0] years), followed by validation in an independent cross-sectional cohort with array-based genotyping for YOD and a prospective cohort of individuals with type 2 diabetes for cardiovascular and kidney events.

RESULTS

In the discovery cohort, the OR of the 135 common variants for YOD ranged from 1.00 to 2.61. In the validation cohort (920 YOD and 4910 non-YOD), top-10%-wPRS was associated with an OR of 1.42 (95% CI 1.03, 1.95, p=0.033) for YOD compared with bottom-10%-wPRS. In 2313 individuals with type 2 diabetes (median [IQR]: age 53.4 [45.4-61.7] years; disease duration 4.0 [1.0-9.0] years) observed for a median (IQR) of 17.5 (14.4-21.8) years, standardised wPRS was associated with increased HR for incident cardiovascular events (1.16 [95% CI 1.06, 1.27], p=0.001), kidney events (1.09 [95% CI 1.02, 1.16], p=0.013) and cardiovascular-kidney events (1.10 [95% CI 1.03, 1.16], p=0.003). Using the 'bottom-20%-wPRS plus baseline disease duration <5 years' group as referent, the 'top-20%-wPRS plus baseline disease duration 5 to <10 years' group had unadjusted and adjusted HR of 1.60 (95% CI 1.17, 2.19, p=0.003) and 1.62 (95% CI 1.16, 2.26, p=0.005), respectively, for cardiovascular-kidney events compared with 1.38 (95% CI 0.97, 1.98, p=0.075) and 1.06 (95% CI 0.72, 1.57, p=0.752) in the 'bottom-20%-wPRS plus baseline disease duration ≥10 years' group.

CONCLUSIONS/INTERPRETATION

Common variants of MDG increased risk for YOD and cardiovascular-kidney events.

Diabetes in China: epidemiology, pathophysiology and multi-omics

Although diabetes is now a global epidemic, China has the highest number of affected people, presenting profound public health and socioeconomic challenges. In China, rapid ecological and lifestyle shifts have dramatically altered diabetes epidemiology and risk factors. In this Review, we summarize the epidemiological trends and the impact of traditional and emerging risk factors on Chinese diabetes prevalence. We also explore recent genetic, metagenomic and metabolomic studies of diabetes in Chinese, highlighting their role in pathogenesis and clinical management. Although heterogeneity across these multidimensional areas poses major analytic challenges in classifying patterns or features, they have also provided an opportunity to increase the accuracy and specificity of diagnosis for personalized treatment and prevention. National strategies and ongoing research are essential for improving diabetes detection, prevention and control, and for personalizing care to alleviate societal impacts and maintain quality of life.

Lessons and Applications of Omics Research in Diabetes Epidemiology

PURPOSE OF REVIEW

Recent advances in genomic technology and molecular techniques have greatly facilitated the identification of disease biomarkers, advanced understanding of pathogenesis of different common diseases, and heralded the dawn of precision medicine. Much of these advances in the area of diabetes have been made possible through deep phenotyping of epidemiological cohorts, and analysis of the different omics data in relation to detailed clinical information. In this review, we aim to provide an overview on how omics research could be incorporated into the design of current and future epidemiological studies.

RECENT FINDINGS

We provide an up-to-date review of the current understanding in the area of genetic, epigenetic, proteomic and metabolomic markers for diabetes and related outcomes, including polygenic risk scores. We have drawn on key examples from the literature, as well as our own experience of conducting omics research using the Hong Kong Diabetes Register and Hong Kong Diabetes Biobank, as well as other cohorts, to illustrate the potential of omics research in diabetes. Recent studies highlight the opportunity, as well as potential benefit, to incorporate molecular profiling in the design and set-up of diabetes epidemiology studies, which can also advance understanding on the heterogeneity of diabetes. Learnings from these examples should facilitate other researchers to consider incorporating research on omics technologies into their work to advance the field and our understanding of diabetes and its related co-morbidities. Insights from these studies would be important for future development of precision medicine in diabetes.

An Insight into Vital Genes Responsible for β-cell Formation

The regulation of glucose homeostasis and insulin secretion by pancreatic β-cells, when disturbed, will result in diabetes mellitus. Replacement of dysfunctional or lost β-cells with fully functional ones can tackle the problem of β-cell generation in diabetes mellitus. Various pancreatic-specific genes are expressed during different stages of development, which have essential roles in pancreatogenesis and β-cell formation. These factors play a critical role in cellular-based studies like transdifferentiation or de-differentiation of somatic cells to multipotent or pluripotent stem cells and their differentiation into functional β-cells. This work gives an overview of crucial transcription factors expressed during various stages of pancreas development and their role in β-cell specification. In addition, it also provides a perspective on the underlying molecular mechanisms.

Polygenic Risk Score, Lifestyles, and Type 2 Diabetes Risk: A Prospective Chinese Cohort Study

The aim of this study was to generate a polygenic risk score (PRS) for type 2 diabetes (T2D) and test whether it could be used in identifying high-risk individuals for lifestyle intervention in a Chinese cohort. We genotyped 80 genetic variants among 5024 participants without non-communicable diseases at baseline in the Wuxi Non-Communicable Diseases cohort (Wuxi NCDs cohort). During the follow-up period of 14 years, 440 cases of T2D were newly diagnosed. Using Cox regression, we found that the PRS of 46 SNPs identified by the East Asians was relevant to the future T2D. Participants with a high PRS (top quintile) had a two-fold higher risk of T2D than the bottom quintile (hazard ratio: 2.06, 95% confidence interval: 1.42-2.97). Lifestyle factors were considered, including cigarette smoking, alcohol consumption, physical exercise, diet, body mass index (BMI), and waist circumference (WC). Among high-PRS individuals, the 10-year incidence of T2D slumped from 6.77% to 3.28% for participants having ideal lifestyles (4-6 healthy lifestyle factors) compared with poor lifestyles (0-2 healthy lifestyle factors). When integrating the high PRS, the 10-year T2D risk of low-clinical-risk individuals exceeded that of high-clinical-risk individuals with a low PRS (3.34% vs. 2.91%). These findings suggest that the PRS of 46 SNPs could be used in identifying high-risk individuals and improve the risk stratification defined by traditional clinical risk factors for T2D. Healthy lifestyles can reduce the risk of a high PRS, which indicates the potential utility in early screening and precise prevention.

Progress in genetics of type 2 diabetes and diabetic complications

Type 2 diabetes results from a complex interaction between genetic and environmental factors. Precision medicine for type 2 diabetes using genetic data is expected to predict the risk of developing diabetes and complications and to predict the effects of medications and life-style intervention more accurately for individuals. Genome-wide association studies (GWAS) have been conducted in European and Asian populations and new genetic loci have been identified that modulate the risk of developing type 2 diabetes. Novel loci were discovered by GWAS in diabetic complications with increasing sample sizes. Large-scale genome-wide association analysis and polygenic risk scores using biobank information is making it possible to predict the development of type 2 diabetes. In the ADVANCE clinical trial of type 2 diabetes, a multi-polygenic risk score was useful to predict diabetic complications and their response to treatment. Proteomics and metabolomics studies have been conducted and have revealed the associations between type 2 diabetes and inflammatory signals and amino acid synthesis. Using multi-omics analysis, comprehensive molecular mechanisms have been elucidated to guide the development of targeted therapy for type 2 diabetes and diabetic complications.

Genome-wide gene and serum ferritin interaction in the development of type 2 diabetes in adults aged 40 years or older

BACKGROUND AND AIMS

Elevated serum ferritin is associated with incident Type 2 diabetes (T2D), but the interactions between serum ferritin and genetic factors which may improve understanding underlying mechanism in the development of T2D are still unclear. We determined the gene-ferritin interactions on the development of T2D by genome-wide gene-ferritin interaction analyses.

METHODS AND RESULTS

A total of 3405 participants from two prospective cohorts of community living residents were included, and the median follow-time was 3.99 years. Genome-wide gene-ferritin interactions were analyzed using the joint test with two degrees of freedom and the interaction test with one degree of freedom. There were 18 SNPs selected in the joint test. Finally, four independent variants [rs355140 (LINC00312), rs4075576 (nearby PDGFA), rs1332202 (PTPRD), and rs713157 (nearby LINC00900)] with low pairwise linkage disequilibrium (r2<0.2) and located at least 1000 kb from the index SNP showed interactions with serum ferritin level. In the association analyses between serum ferritin levels (tertiles of ferritin and ferritin status) and the incidence of T2D according to genotype, the Incidence Rate Ratios (IRRs) in the highest tertile of ferritin level (vs. the lowest tertile) were greater for participants with heterozygotes of risk alleles of each of the four SNP than IRRs for those with wild type. Compared with the normal group, the elevated ferritin group also had a higher risk of T2D for all genetic variants of risk alleles, particularly its homozygotes.

CONCLUSION

Serum ferritin level interacts with genetic variants (rs355140, rs4075576, rs1332202, and rs713157) in the development of T2D.

Genetic susceptibility, family history of diabetes and healthy lifestyle factors in relation to diabetes: A gene-environment interaction analysis in Chinese adults

AIMS/INTRODUCTION

To analyze the associations and interactions of the genetic susceptibility and family history of diabetes with lifestyle factors in relation to diabetes among Chinese adults.

MATERIALS AND METHODS

We constructed a genetic risk score of 34 single-nucleotide polymorphisms in 11,596 participants from Songnan and Youyi communities, Baoshan District, Shanghai, China. We determined a healthy lifestyle by a normal body mass index (<24 kg/m2 ), adequate fruit and vegetable intake (≥4.5 cups/day), never smoked or quit smoking >1 year prior, sufficient physical activity (≥600 metabolic equivalent minutes per week), and a sleep duration of ≥6 to ≤8 h/day. Logistic regression models were used to examine the associations and interactions between heritability and lifestyle on diabetes.

RESULTS

A healthier lifestyle was associated with a lower prevalence of diabetes within any heritable risk groups categorized by the genetic risk score and family history of diabetes. In the combined communities, the odds ratio (95% confidence interval) for diabetes associated with each additional healthy lifestyle factor was 0.83 (0.77-0.89) among participants with a low genetic risk score and 0.86 (0.81-0.91) among participants with a high genetic risk score (Pinteraction  = 0.66). Similar interaction patterns of family history (Pinteraction  = 0.15) and the combination of family history and the genetic risk score with healthy lifestyle (Pinteraction  = 0.55) on diabetes were observed.

CONCLUSIONS

A healthier lifestyle was associated with a significantly lower prevalence of diabetes regardless of heritable risk groups, highlighting the importance of adhering to a healthy lifestyle for diabetes prevention among the entire population.

Comparative epidemiology of gestational diabetes in ethnic Chinese from Shanghai birth cohort and growing up in Singapore towards healthy outcomes cohort

BACKGROUND

Gestational diabetes mellitus (GDM) has been associated with adverse health outcomes for mothers and offspring. Prevalence of GDM differs by country/region due to ethnicity, lifestyle and diagnostic criteria. We compared GDM rates and risk factors in two Asian cohorts using the 1999 WHO and the International Association of Diabetes and Pregnancy Study Groups (IADPSG) criteria.

METHODS

The Shanghai Birth Cohort (SBC) and the Growing Up in Singapore Towards healthy Outcomes (GUSTO) cohort are prospective birth cohorts. Information on sociodemographic characteristics and medical history were collected from interviewer-administered questionnaires. Participants underwent a 2-h 75-g oral glucose tolerance test at 24-28 weeks gestation. Logistic regressions were performed.

RESULTS

Using the 1999 WHO criteria, the prevalence of GDM was higher in GUSTO (20.8%) compared to SBC (16.6%) (p = 0.046). Family history of hypertension and alcohol consumption were associated with higher odds of GDM in SBC than in GUSTO cohort while obesity was associated with higher odds of GDM in GUSTO. Using the IADPSG criteria, the prevalence of GDM was 14.3% in SBC versus 12.0% in GUSTO. A history of GDM was associated with higher odds of GDM in GUSTO than in SBC, while being overweight, alcohol consumption and family history of diabetes were associated with higher odds of GDM in SBC.

CONCLUSIONS

We observed several differential risk factors of GDM among ethnic Chinese women living in Shanghai and Singapore. These findings might be due to heterogeneity of GDM reflected in diagnostic criteria as well as in unmeasured genetic, lifestyle and environmental factors.

Epidemiology and risk factors for diabetes in the suburbs of Beijing: a retrospective cohort study

OBJECTIVE

We aimed to detect the incidence and risk factors of type 2 diabetes mellitus (T2DM) development in the suburbs of Beijing.

DESIGN

Cohort study with record linkage to incidence data.

SETTING

We performed a 5-year follow-up study in a randomly selected suburban population including 1114 subjects aged ≥18 years living in the suburbs of Beijing.

PARTICIPANTS

118 subjects with T2DM at baseline according to the 1999 WHO criteria were excluded, and 895 subjects attended the follow-up assessment in 2012. The non-diabetic subjects at baseline were classified into two groups: normal glucose tolerance (NGT) group (n=673) and impaired glucose regulation (IGR) group(n=222).The incidence and risk factors of diabetes development in each group were investigated.

OUTCOME MEASURES

A structured questionnaire about sociodemographic characteristics, height, weight, waist circumference, hip circumference, blood pressure, oral glucose tolerance test and serum lipid levels.

RESULTS

Out of the 895 non-diabetic subjects, 67 developed diabetes with 29 in the NGT group and 38 in the IGR group, respectively, after a 5-year follow-up, producing an overall 5-year cumulative incidence of diabetes of 13%. The incidence of diabetes was 15.5 cases per 1000 person-years, 8.9 cases per 1000 person-years in the NGT group and 35.7 cases per 1000 person-years in the IGR group (p<0.01; RR 4.03; 95% CI 2.58 to 9.29). Binary logistic regression analysis showed that the risk factors for diabetes development included fasting plasma glucose (FPG) in the NGT group, and sex, the waist-to-hip ratio, FPG and diastolic blood pressure (DBP) in the IGR group.

CONCLUSIONS

During a mean follow-up of 5.0 years, the incidence of T2DM in the suburbs of Beijing was 15.5 per 1000 person-years. Early prevention of diabetes should focus on IGR subjects. Elevated FPG predicted diabetes development for both NGT and IGR subjects. Female sex, overweight/obesity and DBP are risk factors for diabetes development in IGR subjects.

Exome Chip Analysis of 14,026 Koreans Reveals Known and Newly Discovered Genetic Loci Associated with Type 2 Diabetes Mellitus

BACKGROUND

Most loci associated with type 2 diabetes mellitus (T2DM) discovered to date are within noncoding regions of unknown functional significance. By contrast, exonic regions have advantages for biological interpretation.

METHODS

We analyzed the association of exome array data from 14,026 Koreans to identify susceptible exonic loci for T2DM. We used genotype information of 50,543 variants using the Illumina exome array platform.

RESULTS

In total, 7 loci were significant with a Bonferroni adjusted P=1.03×10-6. rs2233580 in paired box gene 4 (PAX4) showed the highest odds ratio of 1.48 (P=1.60×10-10). rs11960799 in membrane associated ring-CH-type finger 3 (MARCH3) and rs75680863 in transcobalamin 2 (TCN2) were newly identified loci. When we built a model to predict the incidence of diabetes with the 7 loci and clinical variables, area under the curve (AUC) of the model improved significantly (AUC=0.72, P<0.05), but marginally in its magnitude, compared with the model using clinical variables (AUC=0.71, P<0.05). When we divided the entire population into three groups-normal body mass index (BMI; <25 kg/m2), overweight (25≤ BMI <30 kg/m2), and obese (BMI ≥30 kg/m2) individuals-the predictive performance of the 7 loci was greatest in the group of obese individuals, where the net reclassification improvement was highly significant (0.51; P=8.00×10-5).

CONCLUSION

We found exonic loci having a susceptibility for T2DM. We found that such genetic information is advantageous for predicting T2DM in a subgroup of obese individuals.

Molecular insights into therapeutic promise of targeting of Wnt/β-catenin signaling pathway in obesity

Obesity is a curable disorder which is a global health concern, linked to an excess amount of fat. It is caused by inherited and environmental factors and can be grim to maintain through dieting only. The importance of peculiar Wnt/β-catenin signaling has directed considerable efforts in the future production of therapeutic approaches in metabolic complications, including obesity. The article aims to examine the prospects of Wnt/β-catenin signaling cascade in obesity via directing effects of Wnt/β-catenin cascade in regulating appetite. A deep research on the literature available to date, for Wnt/β-catenin cascade in obesity is conducted using various medical databases like PubMed, MEDLINE from the internet. The articles published in English language were mainly preferred. Obesity has developed endemic worldwide, which initiates various obesity-related comorbidities. Obesity is implied by excessive deposition of fat primarily in the adipose tissue. Numerous studies have shown the vital impact of the Wnt/β-catenin signaling pathway in the growth of body part and biological homeostasis, while latent data illustrate the inherited variations in the Wnt/β-catenin cascade, correlating to several complications. The current article enlightens the stimulation of the Wnt/β-catenin cascade in obesity, mainly depot-explicit impact among adipose tissue during high caloric intake regulation and WAT browning event. Taken all together these data illustrate Wnt/β-catenin signaling cascade subsidizes to obesity promoted insulin resistance independent proliferation of adipose tissue.

CpG-SNP site methylation regulates allele-specific expression of MTHFD1 gene in type 2 diabetes

The interaction of genetic and epigenetic mechanisms is one of the underlying causes of phenotypic variability in complex diseases such as type 2 diabetes (T2D). To explore the influence of genetic and epigenetic changes in T2D, we examined the effect of methylation of CpG-SNP sites on allele-specific expression (ASE) in one-carbon metabolism pathway genes in T2D. Case-control study was conducted on 860 individuals (430 T2D and 430 controls). CpG-SNPs shortlisted through in silico analysis were genotyped using tetra ARMS PCR and validated using Sanger DNA sequencing. Global DNA methylation was carried out using RP-HPLC. Promoter DNA methylation and CpG site-specific methylation were carried out using bisulfite sequencing. mRNA expression and ASE were examined by SYBR green and TaqMan assay, respectively. Four exonic CpG-SNPs of MTHFD1, MTRR, and GGH genes were identified in folate pathway genes. Among these, MTHFD1 rs2236225 showed significant association with T2D independent of obesity, displayed ASE, and correlated with CpG-SNP site-specific methylation when compared with controls. Our results demonstrate that SNP rs2236225 in the CpG site of MTHFD1, which regulates allele-specific gene expression in PBMCs is methylation dependent and may perturb one-carbon metabolism pathway in T2D subjects.

Cohort profile: the Singapore diabetic cohort study

PURPOSE

The diabetic cohort (DC) was set up to study the determinants of complications in individuals with type 2 diabetes and examine the role of genetic, physiological and lifestyle factors in the development of complications in these individuals.

PARTICIPANTS

A total of 14 033 adult participants with type 2 diabetes were recruited from multiple public sector polyclinics and hospital outpatient clinics in Singapore between November 2004 and November 2010. The first round of follow-up was conducted for 4131 participants between 2012 and 2016; the second round of follow-up started in 2016 and is expected to end in 2021. A questionnaire survey, physical assessments, blood and urine sample collection were conducted at recruitment and each follow-up visit. The data set also includes genetic data and linkage to medical and administrative records for recruited participants.

FINDINGS TO DATE

Data from the cohort have been used to identify determinants of diabetes and related complications. The longitudinal data of medical records have been used to analyse diabetes control over time and its related outcomes. The cohort has also contributed to the identification of genetic loci associated with type 2 diabetes and diabetic kidney disease in collaboration with other large cohort studies. About 25 scientific papers based on the DC data have been published up to May 2019.

FUTURE PLANS

The rich data in DC can be used for various types of research to study disease-related complications in patients with type 2 diabetes. We plan to further investigate disease progression and new biomarkers for common diabetic complications, including diabetic kidney disease and diabetic neuropathy.

Genetic predisposition to type 2 diabetes is associated with severity of coronary artery disease in patients with acute coronary syndromes

Background

Accumulating evidence has shown that type 2 diabetes (T2D) and coronary artery disease (CAD) may stem from a ‘common soil’. The aim of our study was to examine the association between genetic predisposition to T2D and the risk of severe CAD among patients with acute coronary syndromes (ACS) undergoing angiography.

Methods

The current case–control study included 1414 ACS patients with at least one major epicardial vessel stenosis > 50% enrolled in the ACS Genetic Study. The severity of CAD was quantified by the number of coronary arteries involved. Genetic risk score (GRS) was calculated using 41 common variants that robustly associated with increased risk of T2D in East Asians. Logistic regression models were used to estimate the association between GRS and the severity of CAD.

Results

In the age-, sex- and BMI-adjusted model, each additional risk allele was associated with a 6% increased risk of multi-vessel disease (OR = 1.06, 95% CI 1.02–1.09). The OR was 1.43 (95% CI 1.08–1.89) for the risk of severe CAD when comparing the extreme tertiles of T2D-GRS. The association was not reduced after further adjustment for conventional cardiovascular risk factors. Additional adjustment for T2D status in our regression model attenuated the association by approximately one quarter. In subgroup analysis, the strengths of the associations between GRS and the severity of CAD were broadly similar in terms of baseline demographic information and disease characteristics.

Conclusions

Our data indicated that genetic predisposition to T2D is associated with elevated risk of severe CAD. This association revealed a possible causal relationship and is partially mediated through diabetic status.

PAX proteins and their role in pancreas

Gene regulatory factors that govern the expression of heritable information come in an array of flavors, chiefly with transcription factors, the proteins which bind to regions of specific genes and modulate gene transcription, subsequently altering cellular function. PAX transcription factors are sequence-specific DNA-binding proteins exerting its regulatory activity in many tissues. Notably, three members of the PAX family namely PAX2, PAX4 and PAX6 have emerged as crucial players at multiple steps of pancreatic development and differentiation and also play a pivotal role in the regulation of pancreatic islet hormones synthesis and secretion. Providing a comprehensive outline of these transcription factors and their primordial and divergent roles in the pancreas is far-reaching in contemporary diabetes research. Accordingly, this review furnishes an outline of the role of pancreatic specific PAX regulators in the development of the pancreas and its associated disorders.

Standards of medical care for type 2 diabetes in China 2019

The prevalence of diabetes in China has increased rapidly from 0.67% in 1980 to 10.4% in 2013, with the aging of the population and westernization of lifestyle. Since its foundation in 1991, the Chinese Diabetes Society (CDS) has been dedicated to improving academic exchange and the academic level of diabetes research in China. From 2003 to 2014, four versions of Chinese diabetes care guidelines have been published. The guidelines have played an important role in standardizing clinical practice and improving the status quo of diabetes prevention and control in China. Since September 2016, the CDS has invited experts in cardiovascular diseases, psychiatric diseases, nutrition, and traditional Chinese medicine to work with endocrinologists from the CDS to review the new clinical research evidence related to diabetes over the previous 4 years. Over a year of careful revision, this has resulted in the present, new version of guidelines for prevention and care of type 2 diabetes in China. The main contents include epidemiology of type 2 diabetes in China; diagnosis and classification of diabetes; primary, secondary, and tertiary diabetes prevention; diabetes education and management support; blood glucose monitoring; integrated control targets for type 2 diabetes and treatments for hyperglycaemia; medical nutrition therapy; exercise therapy for type 2 diabetes; smoking cessation; pharmacologic therapy for hyperglycaemia; metabolic surgery for type 2 diabetes; prevention and treatment of cardiovascular and cerebrovascular diseases in patients with type 2 diabetes; hypoglycaemia; chronic diabetic complications; special types of diabetes; metabolic syndrome; and diabetes and traditional Chinese medicine.

Ion Channels of the Islets in Type 2 Diabetes

Ca²⁺ is an essential signal for pancreatic β-cell function. Ca²⁺ plays critical roles in numerous β-cell pathways such as insulin secretion, transcription, metabolism, endoplasmic reticulum function, and the stress response. Therefore, β-cell Ca²⁺ handling is tightly controlled. At the plasma membrane, Ca²⁺ entry primarily occurs through voltage-dependent Ca²⁺ channels. Voltage-dependent Ca²⁺ channel activity is dependent on orchestrated fluctuations in the plasma membrane potential or voltage, which are mediated via the activity of many ion channels. During the pathogenesis of type 2 diabetes the β-cell is exposed to stressful conditions, which result in alterations of Ca²⁺ handling. Some of the changes in β-cell Ca²⁺ handling that occur under stress result from perturbations in ion channel activity, expression or localization. Defective Ca²⁺ signaling in the diabetic β-cell alters function, limits insulin secretion and exacerbates hyperglycemia. In this review, we focus on the β-cell ion channels that control Ca²⁺ handling and how they impact β-cell dysfunction in type 2 diabetes.

Cross-population analysis for functional characterization of type II diabetes variants

BACKGROUND

As Genome-Wide Association Studies (GWAS) have been increasingly used with data from various populations, it has been observed that data from different populations reveal different sets of Single Nucleotide Polymorphisms (SNPs) that are associated with the same disease. Using Type II Diabetes (T2D) as a test case, we develop measures and methods to characterize the functional overlap of SNPs associated with the same disease across populations.

RESULTS

We introduce the notion of an Overlap Matrix as a general means of characterizing the functional overlap between different SNP sets at different genomic and functional granularities. Using SNP-to-gene mapping, functional annotation databases, and functional association networks, we assess the degree of functional overlap across nine populations from Asian and European ethnic origins. We further assess the generalizability of the method by applying it to a dataset for another complex disease - Prostate Cancer. Our results show that more overlap is captured as more functional data is incorporated as we go through the pipeline, starting from SNPs and ending at network overlap analyses. We hypothesize that these observed differences in the functional mechanisms of T2D across populations can also explain the common use of different prescription drugs in different populations. We show that this hypothesis is concordant with the literature on the functional mechanisms of prescription drugs.

CONCLUSION

Our results show that although the etiology of a complex disease can be associated with distinct processes that are affected in different populations, network-based annotations can capture more functional overlap across populations. These results support the notion that it can be useful to take ethnicity into account in making personalized treatment decisions for complex diseases.

Diabetes and cancer risk: A Mendelian randomization study

Earlier cohort studies using conventional regression models have consistently shown an increased cancer risk among individuals with type 2 diabetes. However, reverse causality and residual confounding due to common risk factors could exist, and it remains unclear whether diabetes per se contributes to cancer development. Mendelian randomization analyses might clarify the true association between diabetes and cancer risk. We conducted a case-cohort study with 10,536 subcohort subjects and 3,541 newly diagnosed cancer cases derived from 32,949 eligible participants aged 40-69 years within the Japan Public Health Center-based Prospective Study. With 29 known type 2 diabetes susceptibility variants, we used an inverse variance-weighted method to estimate hazard ratios for the associations of diabetes with risks of total and site-specific cancers. The hazard ratios of cancer per doubling of the probability of diabetes were 1.03 (95% confidence interval [CI], 0.92-1.15) overall, 1.08 (95% CI: 0.73-1.59) for the pancreas, 0.80 (95% CI: 0.57-1.14) for the liver and 0.90 (95% CI: 0.74-1.10) for the colorectum. Additional analyses, using publicly available large-scale genome-wide association study data on colorectal cancer in Japan, resulted in a narrower CI (hazard ratio: 1.00; 95% CI: 0.93-1.07). In this prospective Mendelian randomization study with a large number of incident cancer cases, we found no strong evidence to support associations between diabetes and overall and site-specific cancer risks. Our findings suggest that there is little evidence to support the genetic role of type 2 diabetes in cancer development in the Japanese population.

The Role of Glucagon-Like Peptide-1 Receptor Agonists in Type 2 Diabetes in Asia

The improvement of glycemic control in patients with type 2 diabetes (T2D) is an urgent need in Asia. East Asian T2D patients have distinct characteristics, including relatively low body weight, early impairment of islet beta cell function with reduced insulin secretion and a marked increase in postprandial blood glucose levels. Control of postprandial hyperglycemia and beta cell preservation are key elements of the therapeutic strategy for these patients. Glucagon-like peptide-1 receptor agonists (GLP-1RAs) reduce HbA1c, fasting plasma glucose, and (in particular) postprandial glucose levels, and slow gastric emptying, while minimizing the risk of hypoglycemia and weight gain. Compared with long-acting GLP-1RAs, short-acting GLP-1RAs produce greater slowing of gastric emptying (which is a key factor driving the reduction of postprandial glycemia) and induce beta cell rest rather than promoting postprandial insulin secretion when used under physiological conditions. GLP-1RAs have greater efficacy in Asian than Caucasian patients. GLP-1RA add-on therapy provides clinically meaningful reductions in HbA1c and postprandial glucose in Asians with T2D inadequately controlled by oral antidiabetic drugs (OADs) or basal insulin ± OADs. Premixed insulin is often prescribed for T2D patients in China. A short-acting GLP-1RA plus basal insulin is an alternative to premixed insulin, resulting in better efficacy and a lower risk of hypoglycemia and weight gain. In conclusion, GLP-1RAs, especially short-acting GLP-1RAs, are a practical treatment option for East Asian patients with T2D inadequately controlled by OADs or basal insulin.Funding: Sanofi.

PAX4 R192H is associated with younger onset of Type 2 diabetes in East Asians in Singapore

AIMS

Young-onset T2D (YT2D) is associated with a more fulminant course and greater propensity for diabetic complications. The association of PAX4 R192H (rs2233580) variation with YT2D was inconsistent partly because of its Asian-specificity and under-representation of Asians in international consortiums. Interestingly, in our preliminary YT2D (mean = 25 years old) cohort, the prevalence of PAX4 R192H variant was remarkably higher (21.4%) than the general population. Therefore, we sought to determine whether PAX4 R192H is associated with younger onset of T2D in our East Asian (Chinese) population.

METHODS

Genotyping of PAX4 R192H was carried out using Illumina OmniExpress BeadChips as part of a genome-wide association study. Data analysis was performed using SPSS Ver. 22.

RESULTS

PAX4 R192H genotype was associated with younger onset age (CC: 47.1, CT: 46.0, TT: 42.6) after adjusting for gender, F = 5.402, p = 0.005. Independently, onset of diabetes was younger among males by 2.52 years, 95% CI [-3.45, -1.59], p < 0.0001. HOMA-IR and HOMA-%B were not significantly different across genotypes for a subset (n = 1045) of the cohort.

CONCLUSIONS

Minor allele (T) of PAX4 R192H is associated with younger onset diabetes among Chinese in Singapore. Determining this genotype is important for identifying at-risk individuals for earlier onset diabetes and diabetic complications.

Micro-ribonucleic acid-binding site variants of type 2 diabetes candidate loci predispose to gestational diabetes mellitus in Chinese Han women

AIMS/INTRODUCTION

Emerging evidence has suggested that the genetic background of gestational diabetes mellitus (GDM) was analogous to type 2 diabetes mellitus. In contrast to type 2 diabetes mellitus, the genetic studies for GDM were limited. Accordingly, the aim of the present study was to extensively explore the influence of micro-ribonucleic acid-binding single-nucleotide polymorphisms (SNPs) in type 2 diabetes mellitus candidate loci on GDM susceptibility in Chinese.

MATERIALS AND METHODS

A total of 839 GDM patients and 900 controls were enrolled. Six micro-ribonucleic acid-binding SNPs were selected from 30 type 2 diabetes mellitus susceptibility loci and genotyped using TaqMan allelic discrimination assays.

RESULTS

The minor allele of three SNPs, PAX4 rs712699 (OR 1.366, 95% confidence interval 1.021-1.828, P = 0.036), KCNB1 rs1051295 (OR 1.579, 95% confidence interval 1.172-2.128, P = 0.003) and MFN2 rs1042842 (OR 1.398, 95% confidence interval 1.050-1.862, P = 0.022) were identified to significantly confer higher a risk of GDM in the additive model. The association between rs1051295 and increased fasting plasma glucose (b = 0.006, P = 0.008), 3-h oral glucose tolerance test plasma glucose (b = 0.058, P = 0.025) and homeostatic model assessment of insulin resistance (b = 0.065, P = 0.017) was also shown. Rs1042842 was correlated with higher 3-h oral glucose tolerance test plasma glucose (b = 0.056, P = 0.028). However, no significant correlation between the other included SNPs (LPIN1 rs1050800, VPS26A rs1802295 and NLRP3 rs10802502) and GDM susceptibility were observed.

CONCLUSIONS

The present findings showed that micro-ribonucleic acid-binding SNPs in type 2 diabetes mellitus candidate loci were also associated with GDM susceptibility, which further highlighted the similar genetic basis underlying GDM and type 2 diabetes mellitus.

Wnt/β-Catenin Signaling and Obesity

Obesity has become epidemic worldwide, which triggers several obesity-associated complications. Obesity is characterized by excess fat storage mainly in the visceral white adipose tissue (vWAT), subcutaneous WAT (sWAT), and other tissues. Myriad studies have demonstrated the crucial role of canonical Wnt/β-catenin cascade in the development of organs and physiological homeostasis, whereas recent studies show that genetic variations/mutations in the Wnt/β-catenin pathway are associated with human metabolic diseases. In this review, we highlight the regulation of updated Wnt/β-catenin signaling in obesity, especially the distinctly depot-specific roles between subcutaneous and visceral adipose tissue under high-fed diet stimulation and WAT browning process.

Impact of KCNQ1, CDKN2A/2B, CDKAL1, HHEX, MTNR1B, SLC30A8, TCF7L2, and UBE2E2 on risk of developing type 2 diabetes in Thai population

BACKGROUND

Several type 2 diabetes (T2D) susceptibility loci identified via genome-wide association studies were found to be replicated among various populations. However, the influence of these loci on T2D in Thai population is unknown. The aim of this study was to investigate the influence of eight single nucleotide polymorphisms (SNPs) reported in GWA studies on T2D and related quantitative traits in Thai population.

METHODS

Eight SNPs in or near the KCNQ1, CDKN2A/2B, SLC30A8, HHEX, CDKAL1, TCF7L2, MTNR1B, and UBE2E2 genes were genotyped. A case-control association study comprising 500 Thai patients with T2D and 500 ethnically-matched control subjects was conducted. Associations between SNPs and T2D were examined by logistic regression analysis. The impact of these SNPs on quantitative traits was examined by linear regression among case and control subjects.

RESULTS

Five SNPs in KCNQ1 (rs2237892), CDK2A/2B (rs108116610, SLC30A8 (rs13266634), TCF7L2 (rs7903146) and MTNR1B (rs1387153) were found to be marginally associated with risk of developing T2D, with odds ratios ranging from 1.43 to 2.02 (p = 0.047 to 3.0 × 10-4) with adjustments for age, sex, and body mass index. Interestingly, SNP rs13266634 of SLC30A8 gene reached statistical significance after correcting for multiple testing (p = 0.0003) (p < 0.006 after Bonferroni correction). However, no significant association was detected between HHEX (rs1111875), CDKAL1 (rs7756992), or UBE2E2 (rs7612463) and T2D. We also observed association between rs10811661 and both waist circumference and waist-hip ratio (p = 0.007 and p = 0.023, respectively). In addition, rs13266634 in SLC30A8 was associated with glycated hemoglobin (p = 0.018), and rs7903146 in TCF7L2 was associated with high-density lipoprotein cholesterol level (p = 0.023).

CONCLUSION

Of the eight genes included in our analysis, significant association was observed between KCNQ1, CDKN2A/2B, SLC30A8, TCF7L2, and MTNR1B loci and T2D in our Thai study population. Of these, CDKN2A/2B, SLC30A8, and TCF7L2 genes were also significantly associated with anthropometric, glycemic and lipid characteristics. Larger cohort studies and meta-analyses are needed to further confirm the effect of these variants in Thai population.

TCF7L2 Genetic Variation Augments Incretin Resistance and Influences Response to a Sulfonylurea and Metformin: The Study to Understand the Genetics of the Acute Response to Metformin and Glipizide in Humans (SUGAR-MGH)

OBJECTIVE

The rs7903146 T allele in transcription factor 7 like 2 (TCF7L2) is strongly associated with type 2 diabetes (T2D), but the mechanisms for increased risk remain unclear. We evaluated the physiologic and hormonal effects of TCF7L2 genotype before and after interventions that influence glucose physiology.

RESEARCH DESIGN AND METHODS

We genotyped rs7903146 in 608 individuals without diabetes and recorded biochemical data before and after 1) one dose of glipizide (5 mg) on visit 1 and 2) a 75-g oral glucose tolerance test (OGTT) performed after administration of metformin 500 mg twice daily over 2 days. Incretin levels were measured in 150 of the 608 participants.

RESULTS

TT risk-allele homozygotes had 1.6 mg/dL higher baseline fasting glucose levels and 2.5 pg/mL lower glucagon levels per T allele than carriers of other genotypes at baseline. In a subset of participants, the T allele was associated with higher basal glucagon-like peptide 1 (GLP-1) levels at visit 1 (β = 1.52, P = 0.02 and β = 0.96, P = 0.002 for total and active GLP-1, respectively), and across all points of the OGTT after metformin administration. Regarding drug response, the T allele was associated with a shorter time (β = -7.00, P = 0.03) and a steeper slope (β = 0.23, P = 0.04) to trough glucose levels after glipizide administration, and lower visit 2 fasting glucose level adjusted for visit 1 fasting glucose level (β = -1.02, P = 0.04) and a greater decline in glucose level between visits (β = -1.61, P = 0.047) after metformin administration.

CONCLUSIONS

Our findings demonstrate that common variation at TCF7L2 influences acute responses to both glipizide and metformin in people without diabetes and highlight altered incretin signaling as a potential mechanism by which TCF7L2 variation increases T2D risk.

AQR is a novel type 2 diabetes-associated gene that regulates signaling pathways critical for glucose metabolism

Type 2 diabetes mellitus (T2DM) is a common metabolic disease influenced by both genetic and environmental factors. In this study, we performed an in-house genotyping and meta-analysis study using three independent GWAS datasets of T2DM and found that rs3743121, located 1 kb downstream of AQR, was a novel susceptibility SNP associated with T2DM. The risk allele C of rs3743121 was correlated with the increased expression of AQR in white blood cells, similar to that observed in T2DM models. The knockdown of AQR in HepG2 facilitated the glucose uptake, decreased the expression level of PCK2, increased the phosphorylation of GSK-3β, and restored the insulin sensitivity. Furthermore, the suppression of AQR inhibited the mTOR pathway and the protein ubiquitination process. Our study suggests that AQR is a novel type 2 diabetes-associated gene that regulates signaling pathways critical for glucose metabolism.

Association of polymorphisms in LEPR with type 2 diabetes and related metabolic traits in a Chinese population

Background

Leptin acts as a mediator of inflammation and energy homeostasis by activating leptin receptor (LEPR). We conducted this study to explore the association of polymorphisms in LEPR with type 2 diabetes mellitus (T2DM) and its related metabolic traits.

Methods

We performed a case–control study to investigate the association of polymorphisms in LEPR with T2DM and related metabolic traits in a Chinese population, with a total of 922 T2DM patients and 1031 nondiabetic subjects. Polymorphisms were genotyped using MassARRAY assay.

Results

The G allele of rs1327118 was associated with a decreased risk of T2DM in men (P = 0.044, odds ratio = 0.707, 95% confidence interval = 0.504–0.991) and the G allele of rs3806318 was associated with increased systolic blood pressure (SBP) in men with T2DM. Besides, the women patients carrying the G allele of rs1327118 showed increased SBP and diastolic blood pressure (DBP) levels, but decreased high density lipoprotein cholesterol (HDL-C) level.

Conclusion

Our results suggest that rs1327118 may be associated with SBP, DBP and HDL-C levels in women with T2DM, and rs3806318 may be associated with T2DM and SBP level in men with T2DM. Further studies with larger sample size or functional experiments focused on exact mechanism are required to verify our observations.

Diabetes in China: Epidemiology and Genetic Risk Factors and Their Clinical Utility in Personalized Medication

The incidence of type 2 diabetes (T2D) has rapidly increased over recent decades, and T2D has become a leading public health challenge in China. Compared with European descents, Chinese patients with T2D are diagnosed at a relatively young age and low BMI. A better understanding of the factors contributing to the diabetes epidemic is crucial for determining future prevention and intervention programs. In addition to environmental factors, genetic factors contribute substantially to the development of T2D. To date, more than 100 susceptibility loci for T2D have been identified. Individually, most T2D genetic variants have a small effect size (10-20% increased risk for T2D per risk allele); however, a genetic risk score that combines multiple T2D loci could be used to predict the risk of T2D and to identify individuals who are at a high risk. Furthermore, individualized antidiabetes treatment should be a top priority to prevent complications and mortality. In this article, we review the epidemiological trends and recent progress in the understanding of T2D genetic etiology and further discuss personalized medicine involved in the treatment of T2D.

High risk of conversion to diabetes in first-degree relatives of individuals with young-onset type 2 diabetes: a 12-year follow-up analysis

AIM

Family history of diabetes is an established risk factor for Type 2 diabetes, but the impact of a family history of young-onset diabetes (onset < 40 years) on future risk of diabetes among first-degree relatives is unclear. In this prospective study, we examined the influence of family history of late- versus young-onset diabetes on the development of diabetes in a young to middle-aged Chinese population.

METHODS

Some 365 siblings identified through probands with Type 2 diabetes and 452 participants from a community-based health awareness project (aged 18-55 years) who underwent metabolic assessment during the period 1998-2002 were followed to 2012-2013 to determine their glycaemic status. Multivariate logistic regression was performed to investigate the association of family history of diabetes presented at different age categories with development of diabetes.

RESULTS

In this cohort, 53.4% (n = 167) of participants with a family history of young-onset diabetes, 30.1% (n = 68) of those with a family history of late-onset diabetes and 14.4% (n = 40) of those without a family history developed diabetes. Using logistic regression, family history of diabetes presented at ages ≥ 50, 40-49, 30-39 and < 30 years, increased conversion to diabetes with respective odds ratios of 2.4, 5.8, 9.4 and 7.0 (P < 0.001 for all), after adjustment for socio-economic status, smoking, obesity, hypertension and dyslipidaemia. Among participants without diabetes at baseline, risk association of family history of late-onset diabetes with incident diabetes was not sustained, whereas that of family history of young-onset diabetes remained robust on further adjustment for baseline glycaemic measurements.

CONCLUSIONS

First-degree relatives of people with Type 2 diabetes, especially relatives of those with young-onset diabetes, are at high risk for diabetes.

A Decade of Genetic and Metabolomic Contributions to Type 2 Diabetes Risk Prediction

PURPOSE OF REVIEW

The purpose of this review was to summarize and reflect on advances over the past decade in human genetic and metabolomic discovery with particular focus on their contributions to type 2 diabetes (T2D) risk prediction.

RECENT FINDINGS

In the past 10 years, a combination of advances in genotyping efficiency, metabolomic profiling, bioinformatics approaches, and international collaboration have moved T2D genetics and metabolomics from a state of frustration to an abundance of new knowledge. Efforts to control and prevent T2D have failed to stop this global epidemic. New approaches are needed, and although neither genetic nor metabolomic profiling yet have a clear clinical role, the rapid pace of accumulating knowledge offers the possibility for "multi-omic" prediction to improve health.

The rs10229583 polymorphism near paired box gene 4 is associated with gestational diabetes mellitus in Chinese women

Objective

The rs10229583 polymorphism near paired box gene 4 (PAX4) is associated with insulin resistance and type 2 diabetes. Mutations in the PAX4 gene may be associated with impaired differentiation/development of pancreatic islet beta cells during fetal development and, consequently, a compromised insulin response to high blood glucose. To ascertain whether this polymorphism plays a role in gestational diabetes mellitus (GDM), we investigated the genotypic and allele frequency differences between GDM and normal pregnancies.

Methods

A total of 310 GDM and 440 normal pregnancies were evaluated. Allele and genotype frequencies of rs10229583 were determined for all participants with Sanger sequencing and SNaPshot. Association of the allele and genotypes of the single nucleotide polymorphism with the disease was analyzed using Pearson’s χ² test and OR (odds ratio).

Results

The G allele was more frequent in patients with GDM compared with controls (OR = 1.47, 95% confidence interval (CI): 1.12–1.939). The GG genotype frequency of rs10229583 was significantly different between subjects with GDM and normal controls (OR = 1.411, 95% CI: 1.032–1.928). The OR of the GA + GG genotype was 3.182 (95% CI: 1.294–7.826) for patients with GDM compared with controls.

Conclusion

The present study suggests that rs10229583 is associated with GDM.

Utilization of genetic data can improve the prediction of type 2 diabetes incidence in a Swedish cohort

The aim of this study was to measure the impact of genetic data in improving the prediction of type 2 diabetes (T2D) in the Malmö Diet and Cancer Study cohort. The current study was performed in 3,426 Swedish individuals and utilizes of a set of genetic and environmental risk data. We first validated our environmental risk model by comparing it to both the Finnish Diabetes Risk Score and the T2D risk model derived from the Framingham Offspring Study. The area under the curve (AUC) for our environmental model was 0.72 [95% CI, 0.69–0.74], which was significantly better than both the Finnish (0.64 [95% CI, 0.61–0.66], p-value < 1 x 10⁻⁴) and Framingham (0.69 [95% CI, 0.66–0.71], p-value = 0.0017) risk scores. We then verified that the genetic data has a statistically significant positive correlation with incidence of T2D in the studied population. We also verified that adding genetic data slightly but statistically increased the AUC of a model based only on environmental risk factors (RFs, AUC shift +1.0% from 0.72 to 0.73, p-value = 0.042). To study the dependence of the results on the environmental RFs, we divided the population into two equally sized risk groups based only on their environmental risk and repeated the same analysis within each subpopulation. While there is a statistically significant positive correlation between the genetic data and incidence of T2D in both environmental risk categories, the positive shift in the AUC remains statistically significant only in the category with the lower environmental risk. These results demonstrate that genetic data can be used to increase the accuracy of T2D prediction. Also, the data suggests that genetic data is more valuable in improving T2D prediction in populations with lower environmental risk. This suggests that the impact of genetic data depends on the environmental risk of the studied population and thus genetic association studies should be performed in light of the underlying environmental risk of the population.

Genetic regulation of differentially methylated genes in visceral adipose tissue of severely obese men discordant for the metabolic syndrome

A genetic influence on methylation levels has been reported and methylation quantitative trait loci (meQTL) have been identified in various tissues. The contribution of genetic and epigenetic factors in the development of the metabolic syndrome (MetS) has also been noted. To pinpoint candidate genes for testing the association of SNPs with MetS and its components, we aimed to evaluate the contribution of genetic variations to differentially methylated CpG sites in severely obese men discordant for MetS. A genome-wide differential methylation analysis was conducted in visceral adipose tissue (VAT) of 31 severely obese men discordant for MetS (16 with and 15 without MetS) and identified ∼17,800 variable CpG sites. The genome-wide association study conducted to identify the SNPs (meQTL) associated with methylation levels at variable CpG sites revealed 2292 significant associations (P < 2.22 × 10^-11) involving 2182 unique meQTLs regulating the methylation levels of 174 variable CpG sites. Two meQTLs disrupting CpG sites located within the collagen-encoding COL11A2 gene were tested for associations with MetS and its components in a cohort of 3021 obese individuals. Rare alleles of these meQTLs showed association with plasma fasting glucose levels. Further analysis conducted on these meQTL suggested a biological impact mediated through the disruption of transcription factor (TF)-binding sites based on the prediction of TF-binding affinities. The current study identified meQTL in the VAT of severely obese men and revealed associations of two COL11A2 meQTL with fasting glucose levels.

The Diabetes-Linked Transcription Factor PAX4: From Gene to Functional Consequences

Paired box 4 (PAX4) is a key factor in the generation of insulin producing β-cells during embryonic development. In adult islets, PAX4 expression is sequestered to a subset of β-cells that are prone to proliferation and more resistant to stress-induced apoptosis. The importance of this transcription factor for adequate pancreatic islets functionality has been manifested by the association of mutations in PAX4 with the development of diabetes, independently of its etiology. Overexpression of this factor in adult islets stimulates β-cell proliferation and increases their resistance to apoptosis. Additionally, in an experimental model of autoimmune diabetes, a novel immunomodulatory function for this factor has been suggested. Altogether these data pinpoint at PAX4 as an important target for novel regenerative therapies for diabetes treatment, aiming at the preservation of the remaining β-cells in parallel to the stimulation of their proliferation to replenish the β-cell mass lost during the progression of the disease. However, the adequate development of such therapies requires the knowledge of the molecular mechanisms controlling the expression of PAX4 as well as the downstream effectors that could account for PAX4 action.

Exome-chip association analysis reveals an Asian-specific missense variant in PAX4 associated with type 2 diabetes in Chinese individuals

AIMS/HYPOTHESIS

Genome-wide association studies (GWASs) have identified many common type 2 diabetes-associated variants, mostly at the intronic or intergenic regions. Recent advancements of exome-array genotyping platforms have opened up a novel means for detecting the associations of low-frequency or rare coding variants with type 2 diabetes. We conducted an exomechip association analysis to identify additional type 2 diabetes susceptibility variants in the Chinese population.

METHODS

An exome-chip association study was conducted by genotyping 5640 Chinese individuals from Hong Kong, using a custom designed exome array, the Asian Exomechip. Single variant association analysis was conducted on 77,468 single nucleotide polymorphisms (SNPs). Fifteen SNPs were subsequently genotyped for replication analysis in an independent Chinese cohort comprising 12,362 individuals from Guangzhou. A combined analysis involving 7189 cases and 10,813 controls was performed.

RESULTS

In the discovery stage, an Asian-specific coding variant rs2233580 (p.Arg192His) in PAX4, and two variants at the known loci, CDKN2B-AS1 and KCNQ1, were significantly associated with type 2 diabetes with exome-wide significance (p _discovery < 6.45 × 10^-7). The risk allele (T) of PAX4 rs2233580 was associated with a younger age at diabetes diagnosis. This variant was replicated in an independent cohort and demonstrated a stronger association that reached genome-wide significance (p _{meta-analysis} [p _meta] = 3.74 × 10^-15) in the combined analysis.

CONCLUSIONS/INTERPRETATION

We identified the association of a PAX4 Asian-specific missense variant rs2233580 with type 2 diabetes in an exome-chip association analysis, supporting the involvement of PAX4 in the pathogenesis of type 2 diabetes. Our findings suggest PAX4 is a possible effector gene of the 7q32 locus, previously identified from GWAS in Asians.

Type 2 Diabetes Genetic Variants and Risk of Diabetic Retinopathy

PURPOSE

Genetic association studies to date have not identified any robust risk loci for diabetic retinopathy (DR). We hypothesized that individuals with more diabetes genetic risk alleles have a higher risk of developing DR.

DESIGN

Case-control genetic association study.

PARTICIPANTS

We evaluated the aggregate effects of multiple type 2 diabetes-associated genetic variants on the risk of DR among 1528 participants with diabetes from the Singapore Epidemiology of Eye Diseases Study, of whom 547 (35.8%) had DR.

METHODS

Participants underwent a comprehensive ocular examination, including dilated fundus photography. Retinal photographs were graded using the modified Airlie House classification system to assess the presence and severity of DR following a standardized protocol. We identified 76 previously discovered type 2 diabetes-associated single nucleotide polymorphisms (SNPs) and constructed multilocus genetic risk scores (GRSs) for each individual by summing the number of risk alleles for each SNP weighted by the respective effect estimates on DR. Two GRSs were generated: an overall GRS that included all 76 discovered type 2 diabetes-associated SNPs, and an Asian-specific GRS that included a subset of 55 SNPs previously found to be associated with type 2 diabetes in East and/or South Asian ancestry populations. Associations between the GRSs with DR were determined using logistic regression analyses. Discriminating ability of the GRSs was determined by the area under the receiver operating characteristic curve (AUC).

MAIN OUTCOME MEASURES

Odds ratios on DR.

RESULTS

Participants in the top tertile of the overall GRS were 2.56-fold more likely to have DR compared with participants in the lowest tertile. Participants in the top tertile of the Asian-specific GRS were 2.00-fold more likely to have DR compared with participants in the bottom tertile. Both GRSs were associated with higher DR severity levels. However, addition of the GRSs to traditional risk factors improved the AUC only modestly by 3% to 4%.

CONCLUSIONS

Type 2 diabetes-associated genetic loci were significantly associated with higher risks of DR, independent of traditional risk factors. Our findings may provide new insights to further our understanding of the genetic pathogenesis of DR.

Targeting pancreatic expressed PAX genes for the treatment of diabetes mellitus and pancreatic neuroendocrine tumors

INTRODUCTION

Four members of the PAX family, PAX2, PAX4, PAX6 and PAX8 are known to be expressed in the pancreas. Accumulated evidences indicate that several pancreatic expressed PAX genes play a significant role in pancreatic development/functionality and alterations in these genes are involved in the pathogenesis of pancreatic diseases. Areas covered: In this review, we summarize the ongoing research related to pancreatic PAX genes in diabetes mellitus and pancreatic neuroendocrine tumors. We dissect the current knowledge at different levels; from mechanistic studies in cell lines performed to understand the molecular processes controlled by pancreatic PAX genes, to in vivo studies using rodent models that over-express or lack specific PAX genes. Finally, we describe human studies associating variants on pancreatic-expressed PAX genes with pancreatic diseases. Expert opinion: Based on the current literature, we propose that future interventions to treat pancreatic neuroendocrine tumors and diabetes mellitus could be developed via the modulation of PAX4 and/or PAX6 regulated pathways.

THE DIABETES EPIDEMIC IN CHINA: AN INTEGRATED REVIEW OF NATIONAL SURVEYS

OBJECTIVE

To review trends in the prevalence and incidence of diabetes mellitus (DM) and related risk factors in China.

METHODS

We searched the literature using PubMed, China Knowledge Resource Integrated Database, and China Wanfang Digital Database for large epidemiologic studies and national surveys.

RESULTS

During the past 30 years (1980-2010), 7 national diabetes mellitus surveys were conducted in China mainland, indicating that the prevalence of DM has increased 17-fold, from 0.67 to 11.6% of the population. The prevalence of impaired glucose regulation (IGR, including impaired fasting glucose and impaired glucose tolerance) also increased, from 2.09 in 1994 to 27.2% in 2010. There was no national representative study of the incidence of diabetes to date; the reported incidence of type 2 diabetes during past 25 years in several cohort studies varied (2.7 to 15.8 per 1,000 person-years). Potential risk factors which could have contributed to the increasing prevalence and incidence of DM and IGR in the Chinese population include social and economic development, urbanization, dietary pattern, and Westernized lifestyle. Further, genetic studies have suggested that unique inheritable risk factors in the Chinese population may increase the risk for DM when compared to Caucasians.

CONCLUSION

DM and IGR have become epidemic in China. Public health strategies should focus on modifying lifestyle and dietary factors, particularly among those with a susceptible genetic background.

ABBREVIATIONS

BMI = body mass index DM = diabetes mellitus FBG = fasting blood glucose GWAS = genome-wide association study IGR = impaired glucose regulation IGT = impaired glucose tolerance OGTT = oral glucose tolerance test T2D = type 2 diabetes WC = waist circumference WHR = waist-hip ratio.

Genetic Variants of Retinoic Acid Receptor-Related Orphan Receptor Alpha Determine Susceptibility to Type 2 Diabetes Mellitus in Han Chinese

Retinoic acid receptor-related orphan receptor alpha (RORA) plays a key role in the regulation of lipid and glucose metabolism and insulin expression that are implicated in the development of type 2 diabetes mellitus (T2DM). However, the effects of genetic variants in the RORA gene on the susceptibility to T2DM remain unknown. Nine tagging single-nucleotide polymorphisms (SNPs) were screened by using the SNaPshot method in 427 patients with T2DM and 408 normal controls. Association between genotypes and haplotypes derived from these SNPs with T2DM was analyzed using different genetic models. Allele and genotype frequencies at rs10851685 were significantly different between T2DM patients and control subjects (allele: p = 0.009, Odds ratios (OR) = 1.36 [95% Confidence intervals (CI) = 1.08-1.72]; genotype: p = 0.029). The minor allele T, at rs10851685, was potentially associated with an increased risk of T2DM in the dominant model, displaying OR of 1.38 (95% CI: 1.04-1.82, p = 0.025) in subjects with genotypes TA+TT vs. AA. In haplotype analysis, we observed that haplotypes GGTGTAACT, GGTGTAACC, and GATATAACT were significantly associated with increased risk of T2DM, while haplotypes GATGAAGTT, AGTGAAGTT, and AATGAAATT were protective against T2DM. These data suggest that the genetic variation in RORA might determine a Chinese Han individual's susceptibility to T2DM.

The genetic architecture of type 2 diabetes

The genetic architecture of common traits, including the number, frequency, and effect sizes of inherited variants that contribute to individual risk, has been long debated. Genome-wide association studies have identified scores of common variants associated with type 2 diabetes, but in aggregate, these explain only a fraction of the heritability of this disease. Here, to test the hypothesis that lower-frequency variants explain much of the remainder, the GoT2D and T2D-GENES consortia performed whole-genome sequencing in 2,657 European individuals with and without diabetes, and exome sequencing in 12,940 individuals from five ancestry groups. To increase statistical power, we expanded the sample size via genotyping and imputation in a further 111,548 subjects. Variants associated with type 2 diabetes after sequencing were overwhelmingly common and most fell within regions previously identified by genome-wide association studies. Comprehensive enumeration of sequence variation is necessary to identify functional alleles that provide important clues to disease pathophysiology, but large-scale sequencing does not support the idea that lower-frequency variants have a major role in predisposition to type 2 diabetes.

Evaluation of type 2 diabetes genetic risk variants in Chinese adults: findings from 93,000 individuals from the China Kadoorie Biobank

AIMS/HYPOTHESIS

Genome-wide association studies (GWAS) have discovered many risk variants for type 2 diabetes. However, estimates of the contributions of risk variants to type 2 diabetes predisposition are often based on highly selected case-control samples, and reliable estimates of population-level effect sizes are missing, especially in non-European populations.

METHODS

The individual and cumulative effects of 59 established type 2 diabetes risk loci were measured in a population-based China Kadoorie Biobank (CKB) study of 93,000 Chinese adults, including >7,100 diabetes cases.

RESULTS

Association signals were directionally consistent between CKB and the original discovery GWAS: of 56 variants passing quality control, 48 showed the same direction of effect (binomial test, p = 2.3 × 10(-8)). We observed a consistent overall trend towards lower risk variant effect sizes in CKB than in case-control samples of GWAS meta-analyses (mean 19-22% decrease in log odds, p ≤ 0.0048), likely to reflect correction of both 'winner's curse' and spectrum bias effects. The association with risk of diabetes of a genetic risk score, based on lead variants at 25 loci considered to act through beta cell function, demonstrated significant interactions with several measures of adiposity (BMI, waist circumference [WC], WHR and percentage body fat [PBF]; all p interaction < 1 × 10(-4)), with a greater effect being observed in leaner adults.

CONCLUSIONS/INTERPRETATION

Our study provides further evidence of shared genetic architecture for type 2 diabetes between Europeans and East Asians. It also indicates that even very large GWAS meta-analyses may be vulnerable to substantial inflation of effect size estimates, compared with those observed in large-scale population-based cohort studies.

ACCESS TO RESEARCH MATERIALS

Details of how to access China Kadoorie Biobank data and details of the data release schedule are available from www.ckbiobank.org/site/Data+Access .