Monica Ahuja

Common variants of inflammatory cytokine genes are associated with risk of nephropathy in type 2 diabetes among Asian Indians.

Background Inflammatory cytokine genes have been proposed as good candidate genes for conferring susceptibility to diabetic nephropathy. In the present study, we examined the combined effect of multiple alleles of pro inflammatory cytokine genes for determining the risk of nephropathy in type 2 diabetic patients. Methodology/Principal Findings Eight single nucleotide polymorphisms (SNPs) of pro-inflammatory cytokine genes (CCL2, TGFB1, IL8, CCR5, and MMP9) were genotyped in two independently ascertained type 2 diabetic cohorts with (DN) and without nephropathy (DM); consisting of patients from North India (n = 495) and South India (n = 188). Genotyping was carried out using PCR, allele specific oligonucleotide-PCR (ASO-PCR), PCR-RFLP and TaqMan allelic discrimination assays and the gene–gene interaction among genetic variants were determined by multi dimensional reduction (MDR) software. Serum high sensitive CRP (hs-CRP) levels were measured by ELISA. The hs-CRP levels were significantly higher in DN as compared to the DM group (p<0.05). The CCL2, IL8, CCR5 and MMP9 polymorphisms were found to be associated with the risk of diabetic nephropathy. Frequency of CCL2 II, IL8 -251AA, CCR5 59029AA and MMP9 279Gln/Gln genotypes were significantly higher in DN than in DM group (p<0.05) and associated with an increased risk of nephropathy in both North and South Indian cohorts. CCR5 DD and IL8 -251AA genotypes were more prevalent in North Indian DN group only. The co-occurrence of risk associated genotypes (II, -2518GG (CCL2), DD (CCR5) and 279Gln/Gln (MMP9) conferred a tenfold increased risk of nephropathy among type 2 diabetics (p<0.0002). Conclusion The present study highlights that common variants of inflammatory cytokine genes exert a modest effect on risk of DN and a combination of risk alleles confer a substantial increased risk of nephropathy in type 2 diabetes among Asian Indians.

ACE variants interact with the RAS pathway to confer risk and protection against type 2 diabetic nephropathy.

Genetic predisposition has been proposed to be a major determinant in the development of renal complications of diabetes. Among candidate genes examined for susceptibility to diabetic nephropathy, angiotensin-converting enzyme (ACE) gene has been found to be associated with pathogenesis and progression of diabetic nephropathy. However, the role of other renin-angiotensin system (RAS) polymorphisms and their possible interactions with different ACE I/D genotypes are less clearly defined. Recent studies also show that ACE haplotypes may be better predictors to disease susceptibility. Thus, in the present study, we evaluated the association of ACE haplotypes and the interactions of ACE, angiotensinogen (AGT), and angiotensin II receptor type I (AGTR1) gene polymorphisms with DNP in Asian Indians. We genotyped seven variants of the RAS pathway genes (ACE, AGT, and AGTR1) in type 2 diabetic cohorts without nephropathy (DM) and with nephropathy (DNP), using allele-specific oligonucleotide-PCR, and PCR-restriction fragment length polymorphism assays. We studied the interaction of these variants with each other and ACE I/D polymorphism. Frequency of ACE D allele and DD genotype (ACE I/D) was significantly higher in DNP (p < 0.005) and was associated with increased risk of nephropathy. The frequency of T allele, MT/TT genotypes (AGT: M235T), and C allele 1166CC genotype (AGTR1: A1166C) was higher and associated with increased risk of DNP (235T, p < 0.0001; 235TT/MT, p < 0.01; 1166C, p < 0.007; 1166CC, p < 0.0001). The ACE locus revealed a near doubling in the prevalence of T-D-G risk haplotype (odds ratio, 1.76) in DNP (0.13) compared to DM (0.08; p < 0.02). ACE haplotypes carrying the I allele were associated with a lower risk of DNP (C-I-A, p < 0.04; C-I-G, p < 0.008). ACE ID/DD genotypes in combination with ACE rs4311, rs4343, and AGT rs699 mutant genotypes increased the risk of DNP development fourfold (p < 0.01). This study provides the first evidence for a disease haplotype for DNP at the ACE locus in Asian Indians. The study further indicates that ACE D allele individually and in interaction with other RAS single-nucleotide polymorphisms significantly increases the risk of nephropathy in type 2 diabetic patients of Asian Indian origin.

Combined Effect of Smoking and Polymorphisms in Tobacco Carcinogen-Metabolizing Enzymes CYP1A1 and GSTM1 on the Head and Neck Cancer Risk in North Indians

Tobacco consumption contributes to the etiology of majority of cancers, and polymorphisms in tobacco-metabolizing enzymes may modulate susceptibility to head and neck cancer (HNC). The aim of this study was to determine whether genetic polymorphisms in genes CYP1A1 and GSTM1, involved in metabolism of major classes of tobacco-derived carcinogens, may predispose to development of HNC in a North Indian population. In this case-control study, 203 HNC patients and 201 control subjects were genotyped for four variants of CYP1A1 using polymerase chain reaction-restriction fragment length polymorphism, and GSTM1 was analyzed for copy number variations by real-time polymerase chain reaction. Haplotype analysis was performed for the CYP1A1 gene using PHASE version 2.1. CYP1A1 CC (T3801C) (odds ratio [OR], 3.49; 95% confidence interval [CI], 1.34-9.05), GSTM1 single copy (OR, 2.63; 95% CI, 1.54-4.51), and null genotypes (OR, 4.37; 95% CI, 2.61-7.29) were found to be significantly associated with an increased risk of HNC. The gene-environment interactions revealed significant interactions among smokers carrying CYP1A1 AG (A2455G) and GSTM1 copy number variants. CYP1A1 haplotypes carrying variant 3801C allele, C-A-C (OR, 2.45; 95% CI, 1.56-3.83), and C-G-C (OR, 2.39; 95% CI, 1.35-4.25) were found to be associated with a twofold increased risk of HNC. GSTM1 copy number variations and CYP1A1 polymorphisms individually as well in interaction with tobacco consumption may increase the risk of HNC.

Interactions among genetic variants in tobacco metabolizing genes and smoking are associated with head and neck cancer susceptibility in North Indians.

It is becoming clearly evident that single gene or single environmental factor cannot explain susceptibility to diseases with complex etiology such as head and neck cancer. In this study, we applied the multifactor dimensionality reduction method to explore potential gene-environment and gene-gene interactions that may contribute to predisposition to head and neck cancer in the North Indian population. We genotyped 203 patients with head and neck cancer and 201 healthy controls for 13 functional polymorphisms in genes coding for tobacco metabolizing enzymes; CYP1A1, CYP2A13, GSTM1, and UGT1A7 using polymerase chain reaction-restriction fragment length polymorphism method, real-time polymerase chain reaction quantitative assay, and denaturing high-performance liquid chromatography followed by direct sequencing. We found that GSTM1 copy number variations were the most influential factor for head and neck cancer. We also observed significant gene-gene interactions among GSTM1 copy number variants, CYP1A1 T3801C and UGT1A7 T622C variants among smokers. Multifactor dimensionality reduction approach showed that the three-factor model, including smoking status, CYP1A1 T3801C, and GSTM1 copy number variants, conferred more than fourfold increased risk of head and neck cancer (odds ratio 4.89; 95% confidence interval: 3.15-7.32, p < 0.01). These results support the hypothesis that genetic variants in tobacco metabolizing genes may contribute to head and neck cancer risk through gene-gene and gene-environmental interactions.