No linkage of P187S polymorphism in NAD(P)H: quinone oxidoreductase (NQO1/DIA4) and type 1 diabetes in the Danish population. DIEGG and DSGD. Danish IDDM Epidemiology and Genetics Group and The Danish Study Group of Diabetes in Childhood

Roles of NAD(P)H:quinone Oxidoreductase 1 in Diverse Diseases

NAD(P)H:quinone oxidoreductase (NQO) is an antioxidant flavoprotein that catalyzes the reduction of highly reactive quinone metabolites by employing NAD(P)H as an electron donor. There are two NQO enzymes—NQO1 and NQO2—in mammalian systems. In particular, NQO1 exerts many biological activities, including antioxidant activities, anti-inflammatory effects, and interactions with tumor suppressors. Moreover, several recent studies have revealed the promising roles of NQO1 in protecting against cardiovascular damage and related diseases, such as dyslipidemia, atherosclerosis, insulin resistance, and metabolic syndrome. In this review, we discuss recent developments in the molecular regulation and biochemical properties of NQO1, and describe the potential beneficial roles of NQO1 in diseases associated with oxidative stress.

Interactive effect of smoking and NQO1 haplotypes on lung cancer risk

The role of genetic polymorphisms of

NAD(P)H

quinone oxidoreductase 1 (NQO1), which is known to be related to carcinogen metabolism and oxidative status, was evaluated for lung cancer development. The genotypes of two NQO1 polymorphisms, namely, IVS1-27C>G and Ex6+40C>T, were determined in 616 lung cancer cases and 616 lung cancer-free controls and haplotypes composed of the two polymorphisms were estimated. In the evaluation of the effect of the NQO1 genotypes or diplotypes, we did not find any significant association with lung cancer risk after adjusting for body mass index and smoking status. However, when we evaluated the effect of the NQO1 diplotypes for lung cancer risk in combination with smoking, smokers without the C-T/C-T diplotype showed a significantly increased risk of lung cancer compared with nonsmokers without the C-T/C-T diplotype (adjusted OR, 2.2; 95% CI, 1.67-3.02), and smokers with the C-T/C-T diplotype showed the highest OR of lung cancer (adjusted OR, 2.7; 95% CI, 1.78-4.21). Moreover, a trend test showed an additive interaction between smoking and the NQO1 C-T/C-T diplotype (P trend < 0.01). The additive effect of smoking and the NQO1 C-T/C-T diplotype was more apparent in squamous cell carcinoma, although this effect was statistically significant in all lung cancer cell types (all cell types, P trend < 0.05). This result suggests that haplotypes of the NQO1 gene play an important role in the development of lung cancer by interaction with smoking.

Statistical methods for gene set co-expression analysis

Motivation: The power of a microarray experiment derives from the identification of genes differentially regulated across biological conditions. To date, differential regulation is most often taken to mean differential expression, and a number of useful methods for identifying differentially expressed (DE) genes or gene sets are available. However, such methods are not able to identify many relevant classes of differentially regulated genes. One important example concerns differentially co-expressed (DC) genes.

Results: We propose an approach, gene set co-expression analysis (GSCA), to identify DC gene sets. The GSCA approach provides a false discovery rate controlled list of interesting gene sets, does not require that genes be highly correlated in at least one biological condition and is readily applied to data from individual or multiple experiments, as we demonstrate using data from studies of lung cancer and diabetes.

Availability: The GSCA approach is implemented in R and available at www.biostat.wisc.edu/∼kendzior/GSCA/.

Contact:kendzior@biostat.wisc.edu

Supplementary information:Supplementary data are available at Bioinformatics online.

The C609T variant of NQO1 is associated with carotid artery plaques in patients with type 2 diabetes

OBJECTIVE

Atherosclerosis in patients with type 2 diabetes has been linked to oxidative stress. NADP[1]:quinone oxidoreductase 1 (NQO1) plays a key role in cellular antioxidant defense. Recent reports suggest that highly expressed and inducible endogenous NQO1 from cardiovascular cells may act as a potential superoxide scavenger. We examined the relationship between the risk of NQO1 C609T polymorphism and carotid artery atherosclerosis in patients with type 2 diabetes.

METHODS

We recruited 601 (Seoul set) and 233 (Koyang set) unrelated patients with type 2 diabetes from independent groups. The C609T variant of NQO1 was genotyped by Taqman RT-PCR. Mean and maximum carotid intima-media thickness (IMT) and carotid artery plaques were measured by high-resolution ultrasonography.

RESULTS

Patients with the T allele exhibited a higher prevalence of atherosclerotic plaques than non-T allele carriers in both sets (Seoul set vs. Koyang set, p=0.021, p=0.023, respectively). After adjusting for age, sex, duration of diabetes, systolic blood pressure, body mass index, current smoking, HDL-cholesterol, LDL-cholesterol and HbA1c, subjects with the T allele had a significantly higher risk of carotid artery plaques (Seoul set vs. Koyang set, OR=1.65, p=0.015; OR=2.00, p=0.037, respectively) than subjects with the CC genotype.

CONCLUSION

These results suggest that the C609T polymorphism of NQO1 is associated with carotid artery plaques in type 2 diabetic patients.

Oxidative stress, human genetic variation, and disease

Oxidative stress has been implicated in numerous pathophysiological conditions and also aging. The tools for studying oxidative stress are now expanding as a result of the human genome effort and, in particular, expanding knowledge on human genetic variation. A few genetic variants, mostly in the form of single nucleotide polymorphisms of relevance to oxidative stress are already studied by a molecular epidemiologic approach. A review of the current knowledge on variant human genes that are directly implicated in human protection against oxidative stress is presented.