Genetic Approaches to the Study of Gene Variants and Their Impact on the Pathophysiology of Type 2 Diabetes

New-Onset Diabetes Mellitus after Kidney Transplantation

New-Onset Diabetes Mellitus after Transplantation (NODAT) emerges as a prevalent complication post-kidney transplantation, with its incidence influenced by variations in NODAT definitions and follow-up periods. The condition's pathophysiology is marked by impaired insulin sensitivity and β-cell dysfunction. Significant risk factors encompass age, gender, obesity, and genetics, among others, with the use of post-transplant immunosuppressants intensifying the condition. NODAT's significant impact on patient survival and graft durability underscores the need for its prevention, early detection, and treatment. This review addresses the complexities of managing NODAT, including the challenges posed by various immunosuppressive regimens crucial for transplant success yet harmful to glucose metabolism. It discusses management strategies involving adjustments in immunosuppressive protocols, lifestyle modifications, and pharmacological interventions to minimize diabetes risk while maintaining transplant longevity. The importance of early detection and proactive, personalized intervention strategies to modify NODAT's trajectory is also emphasized, advocating for a shift towards more anticipatory post-transplant care.

A causal relationship between alcohol intake and type 2 diabetes mellitus: A two-sample Mendelian randomization study

BACKGROUND AND AIMS

We investigated whether alcohol intake has a causal relationship with type 2 diabetes mellitus (T2DM) risk in adults of the Korean Genomic Epidemiology Study using two-sample Mendelian randomization (MR) analysis.

METHODS AND RESULTS

Daily alcohol intake was calculated based on the type, average amount, and frequency of alcohol consumption for six months before the interview. The participants were divided into low- and high-alcohol intake of 20 g/day. After adjusting for the covariates related to T2DM, the independent genetic variants (instrumental variables) related to alcohol intake were explored by GWAS analysis in a city hospital-based cohort (n = 58,701). SNPs with a significant level of p-value <5 × 10^-8 and linkage disequilibrium of r² < 0.001 were retrieved. MR methods were used to analyze the causality between alcohol intake and the T2DM risk, and the heterogeneity and leave-one-out sensitivity analyses were conducted in Ansan/Ansung plus rural cohorts (n = 13,598). High alcohol intake increased T2DM risk when the inverse-variance weighted (P = 0.012) and weighted median (P = 0.034) methods were used, but not when the MR-Egger method was used. No significant heterogeneity and horizontal pleiotropy between alcohol intake and T2DM were detected. A single genetic variant did not affect the causal association in a leave-one-out sensitivity analysis.

CONCLUSION

This study supports that heavy alcohol intake appears to be causally associated with T2DM risk.

Diabetes and Familial Hypercholesterolemia: Interplay between Lipid and Glucose Metabolism

Familial hypercholesterolemia (FH) is a genetic disease characterized by high low-density lipoprotein (LDL) cholesterol (LDL-c) concentrations that increase cardiovascular risk and cause premature death. The most frequent cause of the disease is a mutation in the LDL receptor (LDLR) gene. Diabetes is also associated with an increased risk of cardiovascular disease and mortality. People with FH seem to be protected from developing diabetes, whereas cholesterol-lowering treatments such as statins are associated with an increased risk of the disease. One of the hypotheses to explain this is based on the toxicity of LDL particles on insulin-secreting pancreatic β-cells, and their uptake by the latter, mediated by the LDLR. A healthy lifestyle and a relatively low body mass index in people with FH have also been proposed as explanations. Its association with superimposed diabetes modifies the phenotype of FH, both regarding the lipid profile and cardiovascular risk. However, findings regarding the association and interplay between these two diseases are conflicting. The present review summarizes the existing evidence and discusses knowledge gaps on the matter.

KCNQ1 rs2237895 polymorphism is associated with the therapeutic response to sulfonylureas in Iranian type 2 diabetes mellitus patients

Background and Aims

Sulfonylureas are the most secondary prescribed oral anti-diabetic drug. Understanding its genetic role in pharmacodynamics can elucidate a considerable knowledge about personalized treatment in type 2 diabetes patients. This study aimed to assess the impact of KCNQ1 variants on sulfonylureas response among type 2 diabetes Iranian patients.

Methods and Results

100 patients were recruited who were under sulfonylureas therapy for six months. 50 responder and 50 non-responder patients were selected. KCNQ1 variants were determined by the RFLP method, and their role in treatment response was assessed retrospectively. Patients with rs2237895 CC and AC genotypes demonstrated a significant decrement in FBS and HbA1c after treatment over patients with AA genotypes (All P < 0.001). Compared to the A allele, the odds ratio for treatment success between carriers with rs2237895 C allele was 4.22-fold (P < 0.001). Patients with rs2237892 CT heterozygous genotype exhibit a higher reduction rate in HbA1c and FBS than CC homozygotes (P=0.064 and P=0.079, respectively). The rs2237892 T allele carriers showed an odds ratio equals to 2.83-fold over C allele carriers in the responder group compared to the non-responder group (p=0.081).

Conclusion

Findings suggest that the KCNQ1 rs2237895 polymorphism is associated with the sulfonylureas response on Iranian type 2 diabetes patients.

Association Between CDKAL1, HHEX, CDKN2A/2B and IGF2BP2 Gene Polymorphisms and Susceptibility to Type 2 Diabetes in Uttarakhand, India

INTRODUCTION

Current study aimed to find the association of genes polymorphism of CDKAL1, HHEX, CDKN2A/2B, and IGF2BP2 with type 2 diabetes (T2DM) in the population of Uttarakhand.

RESEARCH DESIGN AND METHODS

Overall 469 persons comprising 369 recently diagnosed T2DM cases and 100 healthy control were enrolled in the present study. The polymorphisms were analyzed through the PCR-RFLP technique.

RESULTS

For the rs10440833 variant (CDKAL1), CC genotype's frequency was significantly high among T2DM subjects than controls and increase the T2DM risk (OR: 4.46, 95% CI: 2.22-8.99, p <0.0001). The c allele was significantly found to increase the T2DM risk (OR: 2.20, 95% CI: 1.54-3.14, p <0.001). In the rs1111875 variant (HHEX), the difference of genotype frequencies among T2DM cases and control was statistically non-significant (p-0.138). We did not observe significant differences in allelic frequencies among T2DM cases and control (p-0.444). In the case of rs10811661 variant (CDKN2A/2B), frequency of both TC (OR: 3.16, 95% CI: 1.84-5.42, p <0.0001) and TT (OR: 5.84, 95% CI: 1.75-19.45, p -0.004) genotype were significantly higher in T2DM cases in comparison with control and significantly associated with higher T2DM risk. Compared to the C allele, a significant increase in T2DM risk was documented with the T allele (OR: 2.47, 95% CI: 1.55-3.92, p <0.001). For rs4402960 variant (IGF2BP2), TT genotype contributed to increased T2DM risk (OR: 4.25, 95% CI: 2.02-8.93, p -0.0001). T allele's frequency was significantly high in T2DM cases in comparison with healthy control. Except WHR, HDL-C, exercise, household chores, standing work more than 3 hours, and family history, significant differences were found between T2DM cases and healthy individuals in all other parameters.

CONCLUSION

Our study concluded a significant association of CDKAL1, CDKN2A/2B, and IGF2BP2 polymorphism with T2DM in the Uttarakhand population. For HHEX, the genotype and allelic frequencies difference between T2DM cases and control were statistically non-significant. However, a significant association of HHEX gene polymorphism with T2DM was observed only under the dominant model.

PPARG (Pro12Ala) genetic variant and risk of T2DM: a systematic review and meta-analysis

Type 2 diabetes mellitus (T2DM) is a complex disease caused by the interaction between genetic and environmental factors. A growing number of evidence suggests that the peroxisome proliferator-activated receptor gamma (PPARG) gene plays a major role in T2DM development. Meta-analysis of genetic association studies is an efficient tool to gain a better understanding of multifactorial diseases and potentially to provide valuable insights into gene-disease interactions. The present study was focused on assessing the association between Pro12Ala variation in the PPARG and T2DM risk through a comprehensive meta-analysis. We searched PubMed, WoS, Embase, Scopus and ProQuest from 1990 to 2017. The fixed-effect or random-effect model was used to evaluate the pooled odds ratios (ORs) and 95% confidence intervals (CIs) depending on the heterogeneity among studies. The sources of heterogeneity and publication bias among the included studies were assessed using I² statistics and Egger's tests. A total of 73 studies, involving 62,250 cases and 69,613 controls were included. The results showed that the minor allele (G) of the rs1801282 variant was associated with the decreased risk of T2DM under different genetic models. Moreover, the protective effect of minor allele was detected to be significantly more in some ethnicities including the European (18%), East Asian (20%), and South East Asian (18%). And the reduction of T2DM risk in Ala12 carriers was stronger in individuals from North Europe rather than Central and South Europe. Our findings indicated that the rs1801282 variant may contribute to decrease of T2DM susceptibility in different ancestries.

A Bayesian analysis for investigating the association between rs13266634 polymorphism in SLC30A8 gene and type 2 diabetes

Purpose

The purpose of this study was to evaluate the association between rs13266634 polymorphism in SLC30A8 gene and type 2 diabetes in Iranian population, and also to provide a way for adjusting the deviation from the Hardy-Weinberg equilibrium.

Methods

This was a case-control study, the patients were selected from the East Azerbaijan province, Iran. In this study, 125 patients with type 2 diabetes (cases) and 125 healthy individuals (controls) were studied. Genotype and allele frequencies were determined in both groups, and the deviations from the Hardy-Weinberg equilibrium were assessed using Bayesian analysis.

Results

A statistically significant association was observed between rs13266634 polymorphism in SLC30A8 gene and type 2 diabetes. In genotype assessing, data analysis showed that, TT genotype play a role in diabetes type 2 risk (P = 0.001). Subjects with TT genotype had a lower risk of diabetes compared to those with CC and CT genotypes. Also, there was no significant relationship between this polymorphism and type 2 diabetes mellitus in the absence of Hardy-Weinberg equilibrium.

Conclusion

Our findings show that, rs13266634 polymorphism was associated with the type 2 diabetes risk in the population of Eastern Azerbaijan province; however, the low number of TT homozygous genotypes affected the precision of the results. Also, the deviation from HWE affected the results. It is recommended to perform further studies to establish Hardy-Weinberg equilibrium. The inconsistency in the results may be due to the ignorance of this equilibrium.

Family history of diabetes in both parents is strongly associated with impaired residual β-cell function in Japanese type 2 diabetes patients

AIMS/INTRODUCTION

The objective of the present study was to clarify the association of the type and number of first-degree family history of diabetes (FHD) with the clinical characteristics, especially with residual β-cell function, in type 2 diabetes patients.

MATERIALS AND METHODS

A total of 1,131 type 2 diabetes patients were recruited and divided into four groups according to FHD information as follows: (i) patients without FHD (FHD-); (ii) those with at least one sibling who had diabetes without parental diabetes (FHD+); (iii) those with one parent (FHD++); or (iv) those with both parents (FHD+++) who had diabetes with or without a sibling with diabetes.

RESULTS

The percentages of the FHD-, FHD+, FHD++ and FHD+++ groups were 49.4%, 13.4%, 34.0% and 3.2%, respectively. Patients in the FHD++ and FHD+++ groups were significantly younger at the time of diabetes diagnosis (P < 0.001) than those in the FHD- and FHD+ groups, even after adjusting for confounding factors. In addition, the levels of insulin secretion were significantly lower in the patients in the FHD+, FHD++ and FHD+++ groups than those in the FHD- group (P < 0.05) after adjusting for confounding factors, and the patients in the FHD+++ group presented with the lowest levels of insulin secretion among the four groups.

CONCLUSIONS

Our results showed that in type 2 diabetes patients, the degree of the associations between FHD and clinical characteristics differs according to the number and the type of FHD. In particular, FHD in both parents is most strongly associated with impaired residual β-cell function.

Lack of association between TCF7L2 gene variants and type 2 diabetes mellitus in a Brazilian sample of patients with the risk for cardiovascular disease

OBJECTIVE

Genetic variants in the transcription factor 7-like 2 (TCF7L2) gene have been described as the most noteworthy ones regarding the type 2 diabetes mellitus (T2DM) liability. This work is aimed to evaluate the association between rs12255372 and rs7903146 polymorphisms and T2DM in patients with cardiovascular disease (CAD) risk.

METHODS

A sample of six hundred and forty-seven patients that underwent the coronary angiography in a Cardiac Catheterization Lab was evaluated. The patients were investigated for the presence of T2DM and coronary stenosis. The TCF7L2 polymorphisms were genotyped by real-time PCR and the haplotype analysis was performed with the MLOCUS software. All genetic tests were carried out by considering the haplotype combinations in patients divided into three groups: 0 - carrying none disease risk allele, 1 - carrying one or two risk alleles and 2 - carrying three or four risk alleles.

RESULTS

No significant associations between TCF7L2 risk haplotypes and the presence of T2DM or CAD were detected.

CONCLUSIONS

Our results indicate that the TCF7L2 rs12255372 and rs7903146 polymorphisms do not influence T2DM in Brazilian patients with the high risk for CAD. Therefore, we assume that these variants may only be relevant for a specific subgroup of T2DM patients or some particular human population.

Impact of Cytomegalovirus Disease on New-Onset Type 2 Diabetes Mellitus: Population-Based Matched Case-Control Cohort Study

BACKGROUND

A latent cytomegalovirus (CMV) cause chronic inflammation through undesirable inflation of cell-mediated immune response. CMV immunoglobulin G has been associated with cardiovascular disease and type 1 diabetes mellitus. We evaluated impact of CMV diseases on new-onset type 2 diabetes mellitus (T2DM).

METHODS

From the Korean Health Insurance Review and Assessment Service claim database of entire population with 50 million, we retrieved 576 adult case group with CMV diseases diagnosed with International Statistical Classification of Diseases and Related-Health Problems 10th Revision (ICD-10) B25 code between 2010 and 2014 after exclusion of patients with T2DM to 2006. The 2,880 control patients without T2DM from 2006 to cohort entry point were selected between 2010 and 2014 by age, sex matching with case group. The subjects without new-onset T2DM were followed until 2015. T2DM, hypertension (HTN), dyslipidemia (DYS), and end-stage renal disease (ESRD) were coded as ICD-10.

RESULTS

The frequency of new-onset T2DM in case group was significantly higher than that in control (5.6% vs. 2.2%, P<0.001). The group with T2DM (n=95) had higher incidence of CMV diseases than the group without T2DM (n=3,361) (33.7% vs. 16.2%, P<0.001). In multivariate regression model adjusted by age, sex, lower income, HTN, and DYS, the incidence rate (IR) of T2DM in case group was significantly higher than that in the control group (IR per 1,000, 19.0 vs. 7.3; odds ratio, 2.1; 95% confidence interval, 1.3 to 3.2). The co-existence of HTN, DYS, and ESRD with CMV diseases did not influence the IR of T2DM.

CONCLUSION

CMV diseases increase the patients' risk of developing T2DM.

Post-transplant diabetes mellitus in patients with solid organ transplants

Solid organ transplantation (SOT) is a life-saving procedure and an established treatment for patients with end-stage organ failure. However, transplantation is also accompanied by associated cardiovascular risk factors, of which post-transplant diabetes mellitus (PTDM) is one of the most important. PTDM develops in 10-20% of patients with kidney transplants and in 20-40% of patients who have undergone other SOT. PTDM increases mortality, which is best documented in patients who have received kidney and heart transplants. PTDM results from predisposing factors (similar to type 2 diabetes mellitus) but also as a result of specific post-transplant risk factors. Although PTDM has many characteristics in common with type 2 diabetes mellitus, the prevention and treatment of the two disorders are often different. Over the past 20 years, the lifespan of patients who have undergone SOT has increased, and PTDM becomes more common over the lifespan of these patients. Accordingly, PTDM becomes an important condition not only to be aware of but also to treat. This Review presents the current knowledge on PTDM in patients receiving kidney, heart, liver and lung transplants. This information is not only for transplant health providers but also for endocrinologists and others who will meet these patients in their clinics.

Genetic associations between Transcription Factor 7 Like 2 rs7903146 polymorphism and type 2 diabetes mellitus: a meta-analysis of 115,809 subjects

BACKGROUND

Some genetic association studies tried to investigate potential associations of Transcription Factor 7 Like 2 (TCF7L2) rs7903146 polymorphism with type 2 diabetes mellitus (T2DM). However, the results of these studies were not consistent. Thus, we performed the present meta-analysis to explore associations between TCF7L2 rs7903146 polymorphism and T2DM in a larger pooled population.

METHODS

Systematic literature research of PubMed, Web of Science and Embase was performed to identify eligible studies for pooled analyses. I² statistics were employed to assess between-study heterogeneities. If I² was greater than 50%, random-effect models (REMs) would be used to pool the data. Otherwise, fixed-effect models (FEMs) would be applied for synthetic analyses.

RESULTS

Totally 68 studies with 115,809 subjects were included for analyses. The pooled analyses showed that TCF7L2 rs7903146 (dominant model: p < 0.0001; recessive model: p < 0.0001; over-dominant model: p < 0.0001; allele model: p < 0.0001) polymorphism was significantly associated with susceptibility to T2DM in overall population. Further subgroup analyses revealed similar significant findings in both Asians and Caucasians.

CONCLUSIONS

In conclusion, our findings supported that TCF7L2 rs7903146 polymorphism could be used to identify individuals at high risk of developing T2DM in Asians and Caucasians.

Genomic screening for monogenic forms of diabetes

Adult-onset, or type II diabetes mellitus (T2DM) has a complex genetic architecture, from hundreds of genes with low penetrance, common susceptibility variants (e.g., TCF7L2), to a set of more than ten genes that, when mutated, can cause a single-gene or Mendelian form of T2DM (e.g., GCK). It is a clinical challenge to identify patients with the uncommon (2-3%) form of T2DM, typically classified as maturity-onset diabetes of the young (MODY). Bansal et al. (BMC Med 15:213, 2017) used a gene panel test approach to test patients with diabetes for single-gene causes of MODY. They found that nearly 2% of younger patients had pathogenic variants in one of seven genes. These data confirm prior studies showing that Mendelian or single-gene MODY can masquerade as garden variety T2DM. The implications of these results for wider general medicine and the future implementation of clinical genome sequencing are discussed.Please see related article: https://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-017-0977-3.