Insulin receptor substrate 1 (IRS1) variants confer risk of diabetes in the Boston Puerto Rican Health Study

The Role of Global and Local Ancestry on Clopidogrel Response in African Americans

Pharmacogenomics has long lacked dedicated studies in African Americans, resulting in a lack of indepth data in this populations. The ACCOuNT consortium has collected a cohort of 167 African American patients on steady state clopidogrel with the goal of discovering population specific variation that may contribute to the response of this anti-platelet agent. Here we analyze the role of both global and local ancestry on the clinical phenotypes of P2Y12 reaction units (PRU) and high on-treatment platelet reactivity (HTPR) in this cohort. We found that local ancestry at the TSS of three genes, IRS-1, ABCB1 and KDR were nominally associated with PRU, and local ancestry-adjusted SNP association identified variants in ITGA2 associated to increased PRU. These finding help to explain the variability in drug response seen in African Americans, especially as few studies on genes outside of CYP2C19 has been conducted in this population.

Gene polymorphisms of insulin secretion signaling pathway associated with clopidogrel resistance in Han Chinese population

BACKGROUND

Due to the loss of responsiveness to insulin, diabetes mellitus (DM) patients develop increased platelet reactivity and reduced response to antiplatelet agents. Nevertheless, the relationship between the single-nucleotide polymorphisms (SNP) of the signal pathway gene of insulin secretion and the effect of clopidogrel is elusive.

METHODS

Blood samples were collected from patients administered with dual-antiplatelet therapy (clopidogrel, 75 mg, once daily and aspirin, 100 mg, once daily) after 5 days and completed test within 4 h. The VerifyNow P2Y12 assay was used to measure the platelet functions, and the results were expressed as a P2Y12 reaction unit (PRU). Notably, the selected SNPs were analyzed to demonstrate the functionality of genetic variants.

RESULTS

Analysis of the study population showed that old age, lower plasma albumin (ALB) level, higher creatinine (CREA) level, higher uric acid (UA) level, lower platelet (PLT) count, and lower plateletcrit (PCT) potentially increased the risk of clopidogrel resistance. In a single-nucleotide polymorphism rs6056209 of the PCLB1 gene, the AG genotype was a risk factor for clopidogrel resistance (p < 0.05, OR = 1.574). Similarly, the CC and AG genotype in GNAS rs7121 and CCKAR rs1800857 were protective factors (p < 0.05, OR = 0.094; p <0.05, OR = 0.491). TT was a protective factor in rs10814274 of the CREB3 gene (p < 0.05, OR = 0.444). In the RAPGEF4 gene polymorphism rs17746510, TG was the protective genotype, and the TT genotype was a risk factor for clopidogrel resistance. GCG rs5645 was confirmed; there was a relationship between genotypes containing A or G and clopidogrel resistance.

CONCLUSION

Single-nucleotide polymorphisms of insulin secretion signaling pathway genes trigger clopidogrel resistance.

Pyrosequencing analysis of IRS1 methylation levels in schizophrenia with tardive dyskinesia

Tardive dyskinesia (TD) is a serious side effect of certain antipsychotic medications that are used to treat schizophrenia (SCZ) and other mental illnesses. The methylation status of the insulin receptor substrate 1 (IRS1) gene is reportedly associated with SCZ; however, no study, to the best of the authors' knowledge, has focused on the quantitative DNA methylation levels of the IRS1 gene using pyrosequencing in SCZ with or without TD. The present study aimed to quantify DNA methylation levels of 4 CpG sites in the IRS1 gene using a Chinese sample including SCZ patients with TD and without TD (NTD) and healthy controls (HCs). The general linear model (GLM) was used to detect DNA methylation levels among the 3 proposed groups (TD vs. NTD vs. HC). Mean DNA methylation levels of 4 CpG sites demonstrated normal distribution. Pearson's correlation analysis did not reveal any significant correlations between the DNA methylation levels of the 4 CpG sites and the severity of SCZ. GLM revealed significant differences between the 3 groups for CpG site 1 and the average of the 4 CpG sites (P=0.0001 and P=0.0126, respectively). Furthermore, the TD, NTD and TD + NTD groups demonstrated lower methylation levels in CpG site 1 (P=0.0003, P<0.0001 and P<0.0001, respectively) and the average of 4 CpG sites (P=0.0176, P=0.0063 and P=0.003, respectively) compared with the HC group. The results revealed that both NTD and TD patients had significantly decreased DNA methylation levels compared with healthy controls, which indicated a significant association between the DNA methylation levels of the IRS1 gene with SCZ and TD.

Three Novel Mutations I65S, R66S, and G86R Divulge Significant Conformational Variations in the PTB Domain of the IRS1 Gene

Insulin receptor substrate 1 (IRS1) is one of the major substrates for the IR, and their interaction mediates several downstream insulin signaling pathways. In this study, we have identified three novel mutations in the IRS1 gene of type 2 diabetic (T2D) patients, which reflected in the amino acid changes as I65S, R66S, and G86R in the phosphotyrosine binding domain of the IRS1 protein. The impact of these mutations on the structure and function of the IRS1 protein was evaluated through molecular modeling studies, and distinct conformational fluctuations were recorded. The variable binding affinities and positional displacement of these mutant models were observed in the ligand-binding cleft of IR. The mutant IRS1 models triggered conformational changes in the L1 domain of IR upon their binding. Such structural variations in IRS1 and IR structures due to mutations resulted in variable molecular interactions that could lead to altered insulin transduction, followed by insulin resistance and T2D.

Platelets, diabetes and myocardial ischemia/reperfusion injury

Mechanisms underlying the pathogenesis of ischemia/reperfusion injury are particularly complex, multifactorial and highly interconnected. A complex and entangled interaction is also emerging between platelet function, antiplatelet drugs, coronary diseases and ischemia/reperfusion injury, especially in diabetic conditions. Here we briefly summarize features of antiplatelet therapy in type 2 diabetes (T2DM). We also treat the influence of T2DM on ischemia/reperfusion injury and how anti-platelet therapies affect post-ischemic myocardial damage through pleiotropic properties not related to their anti-aggregating effects. miRNA-based signature associated with T2DM and its cardiovascular disease complications are also briefly considered. Influence of anti-platelet therapies and different effects of healthy and diabetic platelets on ischemia/reperfusion injury need to be further clarified in order to enhance patient benefits from antiplatelet therapy and revascularization. Here we provide insight on the difficulty to reduce the cardiovascular risk in diabetic patients and report novel information on the cardioprotective role of widely used anti-aggregant drugs.

Association between IRS1 Gene Polymorphism and Autism Spectrum Disorder: A Pilot Case-Control Study in Korean Males

The insulin-like growth factor (IGF) pathway is thought to play an important role in brain development. Altered levels of IGFs and their signaling regulators have been shown in autism spectrum disorder (ASD) patients. In this study, we investigated whether coding region single-nucleotide polymorphisms (cSNPs) of the insulin receptor substrates (IRS1 and IRS2), key mediators of the IGF pathway, were associated with ASD in Korean males. Two cSNPs (rs1801123 of IRS1, and rs4773092 of IRS2) were genotyped using direct sequencing in 180 male ASD patients and 147 male control subjects. A significant association between rs1801123 of IRS1 and ASD was shown in additive (p = 0.022, odds ratio (OR) = 0.66, 95% confidence interval (CI) = 0.46–0.95) and dominant models (p = 0.013, OR = 0.57, 95% CI = 0.37–0.89). Allele frequency analysis also showed an association between rs1801123 and ASD (p = 0.022, OR = 0.66, 95% CI = 0.46–0.94). These results suggest that IRS1 may contribute to the susceptibility of ASD in Korean males.

Association between insulin receptor substrate-1 polymorphisms and high platelet reactivity with clopidogrel therapy in coronary artery disease patients with type 2 diabetes mellitus

BACKGROUND

The mechanisms leading to the high on-treatment platelet reactivity in diabetes patients are not fully elucidated. The genetic factors may be associated with the diminished antiplatelet efficacy of dual antiplatelet therapy. We investigated the possible association between insulin receptor substrate-1 (IRS-1) polymorphisms and high platelet reactivity in coronary artery disease (CAD) patients with type 2 diabetes mellitus (T2DM).

METHODS

A total of 674 CAD patients with T2DM were enrolled in this study. Platelet aggregation and platelet activation were assessed with light transmission aggregometry and flow cytometry analysis, respectively. Participants were divided into high platelet reactivity (HPR) group and non-HPR group according to their maximal platelet aggregation. Genotypes were identified by polymerase chain reaction and direct sequencing of genomic DNA. The association between IRS-1 genetic variants and platelet function was assessed.

RESULTS

There were 233 participants in the HPR group and 441 participants in the non-HPR group. G allele frequencies of rs13431554 were 27.7 % for the HPR group and 18.6 % for the non-HPR group (p < 0.001). Adenosine diphosphate and arachidonic acid induced platelet aggregation were significantly higher in G allele carriers compared with non-carriers (56.8 ± 16.2 vs 52.0 ± 17.9 %, p < 0.01, 28.9 ± 18.6 vs 25.2 ± 17.8 %, p < 0.01, respectively). We observed that P-selectin expression and PAC-1 binding were higher in G allele carriers compared with non-carriers (40.8 ± 12.4 vs 36.2 ± 13.8, p = 0.01; 43.7 ± 15.9 vs 38.7 ± 19.9, p = 0.03, respectively).

CONCLUSION

The G allele of rs13431554 in the IRS-1 gene was associated with a hyperreactive platelet phenotype in the CAD patients with T2DM.

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.

Circulating 25-hydroxyvitamin D, IRS1 variant rs2943641, and insulin resistance: replication of a gene-nutrient interaction in 4 populations of different ancestries

BACKGROUND

Associations of either insulin receptor substrate 1 (IRS1) variants or circulating 25-hydroxyvitamin D [25(OH)D] with type 2 diabetes (T2D) and insulin resistance (IR) are inconsistent. This study sought to determine whether circulating 25(OH)D modulates the association of a potentially functional variant at IRS1 (rs2943641) with insulin resistance.

METHOD

Interaction between IRS1 rs2943641 and circulating 25(OH)D on homeostasis model assessment for IR (HOMA-IR) was examined in the Boston Puerto Rican Health Study (BPRHS) (n = 1144). Replication was performed in the African-American (n = 1126), non-Hispanic white (n = 1967), and Hispanic (n = 1241) populations of the Multi-Ethnic Study of Atherosclerosis (MESA) with genotypes of 3 IRS1 variants, rs2972144, rs1515104, and rs2673142, which are tag single nucleotide polymorphisms (SNPs) and in strong linkage disequilibrium with rs2943641.

RESULTS

Higher circulating 25(OH)D was associated with lower risk of T2D and IR in BPRHS women homozygous for minor allele rs2943641T. Consistently, in each of 3 MESA populations, HOMA-IR and insulin decreased more evidently with higher circulating 25(OH)D in women of the rs2943641TT genotype than in carriers of the major allele (rs2943641C). Metaanalysis indicated significant and consistent interactions between circulating 25(OH)D and IRS1 variants on HOMA-IR (log transformed) [pooled β = -0.008, 95% CI: -0.016 to -0.001, P interaction = 0.004] and insulin (log transformed) (pooled β = -0.006, 95% CI: -0.011 to -0.002, P interaction = 0.023) in 3065 women of the 4 populations.

CONCLUSIONS

Participants with different genotypes of IRS1 rs2943641 exhibit differential benefit from high circulating 25(OH)D for the reduction of insulin resistance and T2D risk. This gene-nutrient interaction, which appears to be limited to women, warrants further examination in randomized controlled trials of vitamin D supplementation.