Association between the Glu298Asp and 4b/4a polymorphisms of endothelial nitric oxide synthase and coronary slow flow in the North Indian population Mohit D. Gupta a , Cherian Akkarappatty a , Meenahalli P. Girish a , Rahul Kumar b , Manjari Rain b , Sanjay Tyagi a and Mohammed A. Qadar Pasha b Rationale Genetic variants in endothelial nitric oxide synthase gene (NOS3) leading to endothelial dysfunction may be predispose to the coronary slow-flow phenomenon (CSFP). Methods and results In this study, we examined the relationship between Glu298Asp (894G/T) and 4b/4a polymorphisms of NOS3 and CSFP. A total of 27 patients with CSFP but otherwise normal coronary arteries (mean age 50.4±8.2 years) and 200 controls with a normal coronary angiogram (mean age 53.1±8.6 years) were screened for Glu298Asp and 4b/4a polymorphisms by restriction fragment length polymorphism and PCR, respectively. Nitric oxide levels were determined using Griess’ enzymatic method for an association with the polymorphisms. The genotype distribution of the Glu298Asp polymorphism differed significantly between the CSFP patients and controls (P = 0.004). The dominant genetic model showed that GT + TT was significantly prevalent in patients in comparison with controls (P = 0.014) and the T allele was significantly prevalent in patients (P = 0.002). The genetic distribution of 4b/4a differed significantly for the heterozygous genotype ba (P = 0.047). The overdominant genetic model re-established that the ba genotype was significantly prevalent in patients (P = 0.044). Nitric oxide level was higher in patients than in controls, the values being 144.51±43.25 and 129.64±29.47 lmol/l, respectively (P > 0.05). The genotypes of Glu298Asp showed a trend of association with nitric oxide levels, which decreased linearly in the order of GG, GT, and TT (P > 0.05). Conclusion The Glu298Asp polymorphism of NOS3 associates with CSFP. Coron Artery Dis 25:192–197  c 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins. Coronary Artery Disease 2014, 25:192–197 Keywords: coronary artery disease, coronary slow flow, nitric oxide, nitric oxide synthase a Department of Cardiology, Gobind Ballabh Pant Hospital and Associated Maulana Azad Medical College and b Institute of Genomics and Integrative Biology, New Delhi, India Correspondence to Mohit D. Gupta, MD, DM, Department of Cardiology, Room 125, Academic Block, First Floor, Gobind Ballabh Pant Hospital and Associated Maulana Azad Medical College, Jawahar Lal Nehru Marg, New Delhi 110002, India Tel: + 91 11 23955600; fax: + 91 11 23235453; e-mail: drmohitgupta@yahoo.com Received 9 August 2013 Revised 25 September 2013 Accepted 13 January 2014 Introduction Circulating nitric oxide (NO) is a potent vasodilator and acts as a major multipotential molecule that maintains vascular integrity and plays a crucial role in the regulation of endothelial function, control of blood pressure, and cardiovascular homeostasis [1]. The endothelial NO synthase gene (NOS3), which encodes the endothelial NO synthase (eNOS/NOS3), seems to be a potential candidate for predisposition to various cardiovascular disorders. NO production can be influenced by poly- morphisms of NOS3. The NOS3 is expressionally and functionally regulated through multiple regulatory steps [2], and implicates several polymorphisms [3]. Some of these polymorphisms exert functional consequences, among these is the Glu298Asp polymorphism, which has been shown to associate with cardiovascular diseases [4–7]. The coronary slow-flow phenomenon (CSFP) is an angiographic finding characterized by delayed distal vessel opacification in the absence of significant epicardial coronary disease [8]. Coronary endothelial dysfunction is believed to play an important role in CSFP [9,10]. Thus, NOS3 polymorphisms associated with the endothelial dysfunction might also be associat- ing with coronary slow flow. One of the alleles of the Glu298Asp (894G/T) polymorphism is believed to reduce the activity of NOS3, thereby resulting in decreased production of NO, which may predispose an individual to endothelial dysfunction, although functional characterization carried out by Golser et al. [11] did not yield any alteration in the enzymatic function of NOS3. Although an earlier study in Turkish population failed to show the association of the Glu298Asp polymorphism with coronary slow flow [12], the same may not be applicable to other populations because associations are known to have significant ethnic variability. In addition to the Glu298Asp polymorphism, the 4b/4a polymorphism, a 27 bp variable nucleotide tandem repeat, in intron 4, has been found to be associated with cardiovascular diseases [4,13–16] and CSFP [17]. 192 Original research 0954-6928  c 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins DOI: 10.1097/MCA.0000000000000093 Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.