The 9p21 coronary artery disease locus and kidney dysfunction in patients with Type 2 diabetes mellitus

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.

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.

Serum Adiponectin and Glomerular Filtration Rate in Patients with Type 2 Diabetes

High serum adiponectin has been increased in several conditions of kidney disease. Only sparse and conflicting results have been reported in patients with type 2 diabetes (T2D), a subgroup of individuals who are at high risk for renal dysfunction. The aim of this study was to fill up this gap of knowledge by investigating such association in a large sample of Italian diabetic patients. The association between serum adiponectin levels and estimated glomerular filtration rate (eGFR by Chronic Kidney Disease-Epidemiology Collaboration CKD-EPI equation) was investigated in 1,243 patients with T2D from two cross-sectional Italian studies: 878 from San Giovanni Rotondo (SGR) and 365 from Foggia (FG). Serum adiponectin was inversely associated with eGFR in SGR [β (standard error, SE) for 1 standard deviation (SD) of adiponectin = -3.26 (0.64)] and in FG [β(SE)=-5.70(1.28)] sample, as well as in the two studies combined [β(SE)=-3.99(0.59)];(p<0.0001 for all). In this combined analysis, the association was still significant after adjusting for sex, smoking habits, body mass index (BMI), waist circumference, diabetes duration, glycated hemoglobin (HbA1c), albumin creatinine ratio (ACR) and anti-hyperglycemic, anti-hypertensive and anti-dyslipidemic treatments [β (SE)= -2.19 (0.59), p = 0.0001]. A stronger association between each SD adiponectin increment and low eGFR was observed among patients with micro-/macro-albuminuria, as compared to those with normo-albuminuria [adjusted β(SE)=-4.42(1.16) ml/min/1.73m² vs. -1.50 (0.67) ml/min/1.73m², respectively; p for adiponectin-by-albuminuric status = 0.022]. For each adiponectin SD increment, the odds of having eGFR < 60 ml/min/1.73m² increased by 41% (odds ratio, OR = 1.41; 95% confidence interval, CI 1.21–1.64) in SGR sample, 53% (OR = 1.53; 95% CI 1.21–1.94) in FG sample, and 44% (OR = 1.44; 95%CI 1.27–1.64) in the two studies considered together (p<0.0001 for all). In the combined sample, further adjustment for the above mentioned covariates did not change the observed association (OR = 1.36; 95%CI 1.16–1.60; p<0.0001). Our study, so far the largest addressing the relationship between serum adiponectin and GFR in T2D, strongly suggests that the paradoxical inverse association, previously reported in different clinical sets, is also observed in diabetic patients. Further studies are needed to unravel the biology underlying this counterintuitive relationship.

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

This study tried to replicate in a large sample of white patients with type 2 diabetes (T2D) from Italy a previously reported association of the IRS1 G972R polymorphism with failure to oral antidiabetes drugs (OAD). A total of 2,409 patients from four independent studies were investigated. Case subjects (n = 1,193) were patients in whom, because of uncontrolled diabetes (i.e., HbA1c >8%), insulin therapy had been added either on, or instead of, maximal or near-maximal doses of OAD, mostly metformin and sulfonylureas; control subjects (n = 1,216) were patients with HbA1c <8% in the absence of insulin therapy. The IRS1 G972R polymorphism was typed by TaqMan allele discrimination. In all samples, individuals carrying the IRS1 R972 risk variant tended to be more frequent among case than control subjects, though reaching statistical significance only in one case. As no IRS1 G972R-by-study sample interaction was observed, data from the four samples were analyzed together; a significant association was observed (allelic odds ratio [OR] 1.30, 95% CI 1.03-1.63). When our present data were meta-analyzed with those obtained in a previous study, an overall R972 allelic OR of 1.37 (1.12-1.69) was observed. This study confirms in a large and ethnically homogeneous sample that IRS1 G972R polymorphism is associated with failure to OAD among patients with T2D.

The IRS1 G972R polymorphism and glomerular filtration rate in patients with type 2 diabetes of European ancestry

BACKGROUND

In Mexican Americans, the IRS1 G972R polymorphism (rs1801278) has been associated to such a marked reduction in glomerular filtration rate (GFR) (i.e. β = -8.3 mL/min/1.73 m(2)) to be considered a major determinant of kidney function.

METHODS

This was a cross-sectional study to investigate whether a similarly strong effect can also be observed among individuals of European ancestry. We investigated a total of 3973 White patients with type 2 diabetes. Standardized serum creatinine was measured by the modified kinetic Jaffè reaction and estimated GFR (eGFR) calculated by the modification diet renal disease (MDRD) formula; rs1801278 was genotyped by TaqMan assay.

RESULTS

No significant association was observed, with R972 carriers showing only a modestly, not significant, lower eGFR level as compared with other subjects (β = -1.82 mL/min/1.73 m(2), P = 0.086).

CONCLUSIONS

Our data indicate that IRS1 G972R is not a strong determinant of GFR in diabetic patients of European ancestry as in Mexican Americans. Since we had 100% power to detect the previously reported association, the risk our finding is a false negative one is minimal.