Abstract

Free radical-induced damage plays a significant role in the development of type 2 diabetes and its complications. Extracellular superoxide dismutase (EC-SOD) or SOD3 is one of the important scavenger enzymes that protects against oxidative damage and the formation of free radicals. EC-SOD is a copper- and zinc-containing secretory enzyme located in tissues and primarily in the extracellular matrix. EC-SOD has been proposed to protect against pancreatic beta-cell damage, insulin resistance and vascular function in diabetic patients. The association between EC-SOD gene polymorphism and Type 2 diabetes mellitus is not completely understood. The aim of the study is to investigate the EC-SOD gene polymorphism in the exon 3 region and the susceptibility to type 2 diabetes mellitus and its complications among Lebanese patients. For this purpose, a genotype analysis involving 60 Type 2 Diabetes patients and 46 control subjects was carried out using PCR-based direct DNA sequencing. Results showed that the frequency of the Ala40Thr polymorphism of EC-SOD gene was significantly higher in type 2 diabetic patients compared to control group.  Evaluation of clinical parameters of diabetic patients with their relative genotypes showed that patients with the Thr allele have higher HbA1c levels and fasting blood glucose compared to their Ala genotypes indicating a poor diabetes control in these patients. When diabetic complications including retinopathy, nephropathy and cardiovascular complications were correlated with Ala40Val polymorphism, a significant association was detected for complications and particularly for cardiovascular diseases in diabetic patients.

Key words: Type 2 diabetes mellitus, oxidative stress, extracellular superoxide dismutase, genetic biomarker.