IRS1 G972R missense polymorphism is associated with failure to oral antidiabetes drugs in white patients with type 2 diabetes from Italy

Diabetes and Genetics: A Relationship Between Genetic Risk Alleles, Clinical Phenotypes and Therapeutic Approaches

Unveiling human genome through successful completion of Human Genome Project and International HapMap Projects with the advent of state of art technologies has shed light on diseases associated genetic determinants. Identification of mutational landscapes such as copy number variation, single nucleotide polymorphisms or variants in different genes and loci have revealed not only genetic risk factors responsible for diseases but also region(s) playing protective roles. Diabetes is a global health concern with two major types - type 1 diabetes (T1D) and type 2 diabetes (T2D). Great progress in understanding the underlying genetic predisposition to T1D and T2D have been made by candidate gene studies, genetic linkage studies, genome wide association studies with substantial number of samples. Genetic information has importance in predicting clinical outcomes. In this review, we focus on recent advancement regarding candidate gene(s) associated with these two traits along with their clinical parameters as well as therapeutic approaches perceived. Understanding genetic architecture of these disease traits relating clinical phenotypes would certainly facilitate population stratification in diagnosing and treating T1D/T2D considering the doses and toxicity of specific drugs.

Pharmacogenomic Studies of Current Antidiabetic Agents and Potential New Drug Targets for Precision Medicine of Diabetes

Diabetes is a major threat to people's health and has become a burden worldwide. Current drugs for diabetes have limitations, such as different drug responses among individuals, failure to achieve glycemic control, and adverse effects. Exploring more effective therapeutic strategies for patients with diabetes is crucial. Currently pharmacogenomics has provided potential for individualized drug therapy based on genetic and genomic information of patients, and has made precision medicine possible. Responses and adverse effects to antidiabetic drugs are significantly associated with gene polymorphisms in patients. Many new targets for diabetes also have been discovered and developed, and even entered clinical trial phases. This review summarizes pharmacogenomic evidence of some current antidiabetic agents applied in clinical settings, and highlights potential drugs with new targets for diabetes, which represent a more effective treatment in the future.

Pharmacogenetics of Type 2 Diabetes-Progress and Prospects

Type 2 diabetes mellitus (T2D) is a chronic metabolic disease resulting from insulin resistance and progressively reduced insulin secretion, which leads to impaired glucose utilization, dyslipidemia and hyperinsulinemia and progressive pancreatic beta cell dysfunction. The incidence of type 2 diabetes mellitus is increasing worldwide and nowadays T2D already became a global epidemic. The well-known interindividual variability of T2D drug actions such as biguanides, sulfonylureas/meglitinides, DPP-4 inhibitors/GLP1R agonists and SGLT-2 inhibitors may be caused, among other things, by genetic factors. Pharmacogenetic findings may aid in identifying new drug targets and obtaining in-depth knowledge of the causes of disease and its physiological processes, thereby, providing an opportunity to elaborate an algorithm for tailor or precision treatment. The aim of this article is to summarize recent progress and discoveries for T2D pharmacogenetics and to discuss the factors which limit the furthering accumulation of genetic variability knowledge in patient response to therapy that will allow improvement the personalized treatment of T2D.

Obesity, clinical, and genetic predictors for glycemic progression in Chinese patients with type 2 diabetes: A cohort study using the Hong Kong Diabetes Register and Hong Kong Diabetes Biobank

BACKGROUND

Type 2 diabetes (T2D) is a progressive disease whereby there is often deterioration in glucose control despite escalation in treatment. There is significant heterogeneity to this progression of glycemia after onset of diabetes, yet the factors that influence glycemic progression are not well understood. Given the tremendous burden of diabetes in the Chinese population, and limited knowledge on factors that influence glycemia, we aim to identify the clinical and genetic predictors for glycemic progression in Chinese patients with T2D.

METHODS AND FINDINGS

In 1995-2007, 7,091 insulin-naïve Chinese patients (mean age 56.8 ± 13.3 [SD] years; mean age of T2D onset 51.1 ± 12.7 years; 47% men; 28.4% current or ex-smokers; median duration of diabetes 4 [IQR: 1-9] years; mean HbA1c 7.4% ± 1.7%; mean body mass index [BMI] 25.3 ± 4.0 kg/m2) were followed prospectively in the Hong Kong Diabetes Register. We examined associations of BMI and other clinical and genetic factors with glycemic progression defined as requirement of continuous insulin treatment, or 2 consecutive HbA1c ≥8.5% while on ≥2 oral glucose-lowering drugs (OGLDs), with validation in another multicenter cohort of Hong Kong Diabetes Biobank. During a median follow-up period of 8.8 (IQR: 4.8-13.3) years, incidence of glycemic progression was 48.0 (95% confidence interval [CI] 46.3-49.8) per 1,000 person-years with 2,519 patients started on insulin. Among the latter, 33.2% had a lag period of 1.3 years before insulin was initiated. Risk of progression was associated with extremes of BMI and high HbA1c. On multivariate Cox analysis, early age at diagnosis, microvascular complications, high triglyceride levels, and tobacco use were additional independent predictors for glycemic progression. A polygenic risk score (PRS) including 123 known risk variants for T2D also predicted rapid progression to insulin therapy (hazard ratio [HR]: 1.07 [95% CI 1.03-1.12] per SD; P = 0.001), with validation in the replication cohort (HR: 1.24 [95% CI 1.06-1.46] per SD; P = 0.008). A PRS using 63 BMI-related variants predicted BMI (beta [SE] = 0.312 [0.057] per SD; P = 5.84 × 10-8) but not glycemic progression (HR: 1.01 [95% CI 0.96-1.05] per SD; P = 0.747). Limitations of this study include potential misdiagnosis of T2D and lack of detailed data of drug use during follow-up in the replication cohort.

CONCLUSIONS

Our results show that approximately 5% of patients with T2D failed OGLDs annually in this clinic-based cohort. The independent associations of modifiable and genetic risk factors allow more precise identification of high-risk patients for early intensive control of multiple risk factors to prevent glycemic progression.

A Missense Mutation in IRS1 is Associated with the Development of Early-Onset Type 2 Diabetes

There could be an overlap of monogenic diabetes and early-onset type 2 diabetes mellitus. Precise diagnosis of early-onset diabetes has proven valuable for understanding the mechanism of diabetes and selecting optimal therapy. The majority of maturity onset diabetes of the young (MODY) pathogenic genes in China is still unknown. In this study, a family with suspected MODY was enrolled. Whole-exome sequencing (WES) was used to analyze the variants of the proband. Variants were filtered according to their frequency, location, functional consequences, and bioinformatics software. Candidate pathogenic variants were validated by Sanger sequencing and tested for cosegregation in other members of the family and nonrelated healthy controls. KEGG (Kyoto Encyclopedia of Genes and Genomes) and PPI (protein-protein interaction) analysis were conducted using the DAVID (Database for Annotation, Visualization, and Integrated Discovery) and the STRING online analysis tools for the candidate pathogenic gene. A total of 123291 variants including 105344 SNPs and 17947 InDels were found in WES. A likely pathogenic rare missense heterozygous mutation in diabetes genes (c.2137C > T, p.His713Tyr in IRS1) was identified, which was a cosegregate in this family and not in nonrelated healthy controls. The position of the mutation in the aminoacid sequence of the gene is highly conserved among the species. 2 significantly enriched KEGG pathways were identified including bta04930, type II diabetes mellitus (GCK, INS, PDX1, ABCC8, and IRS1), and bta04910, insulin signaling pathway (GCK, INS, and IRS1). PPI analysis displayed that IRS1 interacts with 3 known pathogenic proteins including INS, KCNJ11, and GCK. We conclude that WES could be an initial option for genetic testing in patients with early-onset diabetes. IRS1 p.His713Tyr is implicated as a possible pathogenic mutation in monogenic diabetes, which might require further validation, and the precise molecular mechanism underlying the influence of IRS1 p.His713Tyr on the development of diabetes remains to be determined in the further prospective studies.

Pharmacogenetics of type 2 diabetes mellitus, the route toward tailored medicine

Type 2 diabetes mellitus (T2DM) is a chronic disease that has reached the levels of a global epidemic. In order to achieve optimal glucose control, it is often necessary to rely on combination therapy of multiple drugs or insulin because uncontrolled glucose levels result in T2DM progression and enhanced risk of complications and mortality. Several antihyperglycemic agents have been developed over time, and T2DM pharmacotherapy should be prescribed based on suitability for the individual patient's characteristics. Pharmacogenetics is the branch of genetics that investigates how our genome influences individual responses to drugs, therapeutic outcomes, and incidence of adverse effects. In this review, we evaluated the pharmacogenetic evidences currently available in the literature, and we identified the top informative genetic variants associated with response to the most common anti-diabetic drugs: metformin, DPP-4 inhibitors/GLP1R agonists, thiazolidinediones, and sulfonylureas/meglitinides. Overall, we found 40 polymorphisms for each drug class in a total of 71 loci, and we examined the possibility of encouraging genetic screening of these variants/loci in order to critically implement decision-making about the therapeutic approach through precision medicine strategies. It is possible then to anticipate that when the clinical practice will take advantage of the genetic information of the diabetic patients, this will provide a useful resource for the prevention of T2DM progression, enabling the identification of the precise drug that is most likely to be effective and safe for each patient and the reduction of the economic impact on a global scale.

The rs12917707 polymorphism at the UMOD locus and glomerular filtration rate in individuals with type 2 diabetes: evidence of heterogeneity across two different European populations

Background

UMOD variability has been associated at a genome-wide level of statistical significance with glomerular filtration rate (GFR) in Swedish individuals with type 2 diabetes (T2D; n = 4888). Whether this finding is extensible also to diabetic patients from other populations deserves further study. Our aim was to investigate the relationship between UMOD variability and GFR in patients with T2D from Italy.

Methods

Genotyping of the single nucleotide polymorphism (SNP) rs12917707 at the UMOD locus has been carried out in 3087 individuals from four independent Italian cohorts of patients with T2D by TaqMan allele discrimination.

Results

In none of the four study cohorts was rs12917707 significantly associated with GFR (P > 0.05 for all). Similar results were obtained when the four samples were pooled and analyzed together (β = 0.83, P = 0.19). Such effect was strikingly smaller than that previously reported in Swedish patients (P for heterogeneity = 1.21 × 10-7).

Conclusions

The previously reported strong association between rs12917707 and GFR in diabetic patients from Sweden is not observed in Italian diabetic patients, thus clearly pointing to a heterogeneous effect across the two different samples. This suggests that UMOD is a strong genetic determinant of kidney function in patients with T2D in some, but not all, populations.

Using Personalized Medicine in the Management of Diabetes Mellitus

Diabetes mellitus is a worldwide problem with an immense pharmacoeconomic burden. The multifactorial and complex nature of the disease lends itself to personalized pharmacotherapeutic approaches to treatment. Variability in individual risk and subsequent development of diabetes has been reported in addition to differences in response to the many oral glucose lowering therapies currently available for diabetes pharmacotherapy. Pharmacogenomic studies have attempted to uncover the heritable components of individual variability in risk susceptibility and response to pharmacotherapy. We review the current pharmacogenomics evidence as it relates to common oral glucose lowering therapies and how they can be utilized in the management of polygenic and monogenic forms of diabetes. Evidence supports the use of genetic testing and personalized approaches to the treatment of monogenic diabetes of the young. The data are not as robust for the current application of pharmacogenetic approaches to the treatment of polygenic type 2 diabetes mellitus, but there are suggestions as to future applications in this regard. We reviewed pertinent primary literature sources as well as current evidence-based guidelines on diabetes management.

Pharmacogenetics of oral antidiabetes drugs: evidence for diverse signals at the IRS1 locus

To investigate the role of IRS1 locus on failure to oral antidiabetes drugs (OADs) we genotyped single-nucleotide polymorphisms (SNPs), rs2943641, rs7578326 (tagging all SNPs genome-wide associated with type 2 diabetes (T2D) and related traits at this locus) and rs1801278 (that is, the loss-of-function IRS1 G972R amino acid substitution) in 2662 patients with T2D. Although no association with OAD failure was observed for rs2943641 and rs7578326 SNPs (odds ratio (OR): 1.04, 95% confidence interval (CI): 0.93-1.16 and OR: 0.97, 95% CI: 0.87-1.09 respectively), a significant association was observed for rs1801278 (OR: 1.34, 95% CI: 1.08-1.66). When meta-analyzed with previous published data, an allelic OR of 1.41 (1.15-1.72; P=0.001) was obtained, so that homozygous R972R individuals have >80% higher risk of failing to OADs as compared with their G972G counterparts. In all, though further studies are needed for confirming this finding, our present data point to IRS1 rs1801278 as a potential biomarker for pursuing the goal of stratified medicine in the field of antihyperglycemic treatment in T2D.

On the non-linear association between serum uric acid levels and all-cause mortality rate in patients with type 2 diabetes mellitus

BACKGROUND AND AIMS

High levels of serum uric acid (SUA) are associated with increased mortality risk in the general population. Contrasting results are available in people with diabetes. The aim of our study was to investigate the association and its functional form between SUA and all cause-mortality in patients with type 2 diabetes mellitus (T2DM).

METHODS

We studied three cohorts of patients with T2DM: Gargano Mortality Study, Foggia Mortality Study, Pisa Mortality Study. All-cause mortality rate was the end point of this study.

RESULTS

The most reliable relationship between SUA levels and all-cause mortality rate was quadratic, with such model being well approximated by SUA tertiles. Both tertiles 1 and 3 were at higher risk of mortality as compared to tertile 2: Hazard Ratio (HR) [95% Confidence Interval (CI)] = 1.34 (1.07-1.68) and 1.61 (1.29-1.99), respectively. In the pseudo-sample, created from the real pooled sample, the best relationship between SUA and all-cause mortality rate was quadratic. In a tree-based Recursive Partitioning and Regression Tree analysis two subgroups at increased risk of mortality were identified, namely those with SUA levels ≥7.28 mg/dl and with SUA levels <4.16 mg/dl as compared to patients with intermediate SUA levels (i.e. 4.16-7.28), thus providing further evidence on the J-shaped relationship between SUA levels and mortality rate.

CONCLUSIONS

SUA was not linearly associated with all-cause mortality rate in patients with T2DM. For clinical and public health purposes such association is J-shaped.

Genetic variation near IRS1 is associated with adiposity and a favorable metabolic profile in U.S. Hispanics/Latinos

OBJECTIVE

Associations of IRS1 genetic variation with adiposity and metabolic profile in U.S. Hispanic/Latino individuals of diverse backgrounds were examined.

METHODS

Previously genome-wide association study-identified IRS1 variants (rs2943650, rs2972146, rs2943641, and rs2943634) as related to body fat percentage (BF%) and multiple metabolic traits were tested among up to 12,730 adults (5,232 men; 7,515 women) from the Hispanic Community Health Study/Study of Latinos.

RESULTS

The C-allele (frequency = 26%) of rs2943650 was significantly associated with higher BF% overall (β = 0.34 ± 0.11% per allele; P = 0.002) and in women (β = 0.41 ± 0.14% per C-allele; P = 0.003), but not in men (β = 0.28 ± 0.18% per C-allele; P = 0.11), though there was no significant sex difference. Using the inverse normal-transformed data to compare effect sizes, it was found that the association with BF% was stronger in Hispanic/Latino women than that previously reported in European women (β = 0.054 ± 0.018SD vs. β = 0.008 ± 0.011SD per C-allele; P = 0.03). The BF%-increasing allele of rs2943650 was significantly associated with lower levels of fasting insulin, homeostatic model assessment of insulin resistance, hemoglobin A1c, and triglycerides and higher high-density lipoprotein cholesterol (P < 0.05).

CONCLUSIONS

This study confirmed and extended previous findings of IRS1 variation associated with increased adiposity but a favorable metabolic profile in U.S. Hispanics/Latinos, with a relatively stronger genetic effect on BF% in Hispanic/Latino women compared with European women.

Lack of association between the insulin receptor substrates-1 Gly972Arg polymorphism and type-2 diabetes mellitus among Saudis from Eastern Saudi Arabia

Objectives:

To investigate the association between the insulin receptor substrate-1 (IRS1) Gly972Arg polymorphism and type-2 diabetes mellitus (T2DM) among Saudis from Eastern Saudi Arabia.

Methods:

This study was conducted between May and December 2014 at King Fahad Hospital of the University, Al-Khobar, Kingdom of Saudi Arabia. In a case-control study design, a total of 143 subjects (age range: 35-73 years) comprising 74 healthy controls and 69 patients with T2DM were examined. Blood samples were collected from subjects and subjected to genomic DNA extraction and chemical analysis. The IRS1 Gly972Arg polymorphism was then genotyped using the standard polymerase chain reaction-restriction fragment length polymorphism technique.

Results:

Eight out of 74 (10.8%) of the control group carried at least one copy of the mutated allele. The frequency (8.7%) of the IRS1 variant was also found in the diabetic group. Logistic regression analysis showed an adjusted odds ratio of 1.04, 95% confidence interval 0.28 - 3.95, and a p-value of 0.94.

Conclusion:

We failed to find any association between the IRS1 Gly972Arg polymorphism and T2DM.