Association of the Endothelial Nitric Oxide Synthase (eNOS) G894T Gene Polymorphism With Type 2 Diabetes Mellitus in a Tunisian Population

Abstract

Background: Type 2 Diabetes Mellitus (T2D) is a multifactorial metabolic disorder with a significant genetic component. Endothelial dysfunction, characterised by reduced nitric oxide (NO) bioavailability, is a key pathological feature. The endothelial nitric oxide synthase (eNOS) gene (NOS3) contains several polymorphisms, with the G894T (Glu298Asp) variant being a prominent candidate for influencing disease susceptibility. Objective: This study aimed to investigate the association between the eNOS G894T polymorphism and the risk of T2D in a sample of the Tunisian population. Methods: We conducted a case–control study including 100 T2D patients and 100 non-diabetic controls recruited from the Military Hospital of Tunis. Anthropometric, clinical and biochemical parameters, including lipid profiles and high-sensitivity C-reactive protein (CRPus), were measured. Genotyping of the eNOS G894T polymorphism was performed using the Polymerase Chain Reaction–Restriction Fragment Length Polymorphism (PCR-RFLP) method with the BanII restriction enzyme. Results: T2D patients exhibited significantly higher levels of triglycerides (1.99 ± 1.27 vs. 1.45 ± 0.65 mmol/L, p = 0.002) and CRPus (2.73 ± 2.47 vs. 1.63 ± 1.42 mg/L, p = 0.003) compared to controls. The frequency of the mutated T allele was significantly higher in the T2D group than in the control group (27.53% vs. 11.27%, p < 10−3). Consequently, the heterozygous GT genotype was more prevalent among patients (55.07% vs. 19.72%, p < 10−3). The presence of the T allele was associated with a significantly increased risk of T2D (Odds Ratio [OR] = 4.495, 95% Confidence Interval [CI] = 2.14–9.44). Conclusion: The eNOS G894T polymorphism is a significant genetic risk factor for type 2 diabetes in the studied Tunisian population. The T allele appears to confer susceptibility, likely through mechanisms involving impaired eNOS function, reduced NO production and subsequent endothelial dysfunction.