Study of Association between RAGE Gene Polymorphism (429 T/C and 374 T/A) and Vascular Complications of Diabetic Patients by Using- PCR-RFLP

Abstract

Diabetes mellitus (DM) is a multifactorial disease associated with hyperglycemia and increased risk ofmicro and macrovascular complications which are the major causes of morbidity and mortality. Theprimary causal factor leading to the pathophysiologic alterations in the diabetic vasculature is chronic exposure tohigh blood glucose level. Under hyperglycemic conditions, glucose and other reducing sugars react nonenzymatically with proteins and lipids,leading to formation of advanced glycation end products (AGEs) atan accelerated rate. There is growing evidence that production and accumulation of AGEs isinvolved in the initiation and development of micro and macrovascular complications observed in diabetes mellitus.The effects of AGEs have been shown to be partially mediated via cellular receptors called the receptor for AGEs (RAGE). Interaction of RAGE with AGEs increases receptor expression and activates pro-inflammatory and pro-coagulant pathways, which are the key factors linking the AGE–RAGE system with the development of diabetic complications.The upregulation and pathogenic effects of RAGE in vascular disease make the RAGE gene an attractive candidate gene for diabetic vascular complications. Therefore, genetic variants affecting RAGE expression may be important disease marker. RAGE is a multiligand of the immunoglobulin superfamily of receptors located on chromosome 6p21.3 in the major histocompatibility complex locus in the class III region. At least 30 polymorphisms have been identified within RAGE gene, the most important two polymorphisms in the promotor region that have been highlighted in many studies are 374T/A and 429T/C SNPs. Many studies on different population have investigated the association of 374T/A and 429 T/C polymorphisms with diabetic vascular complication as they affect transcription activity of RAGE but the results were conflicting. Some studies supported the association of the 2 SNPs with diabetic complications with increased risk towards complications. Further studies found a protective role of 374T/A against macrovascular complications. However, other studies found no association of the two polymorphisms with diabetic complications. Our study aimed at investigating the association of 374T/A and 429T/C RAGE gene polymorphisms with diabetic vascular complication. This study was conducted on (36) adult patients with type 2 diabetes mellitus divided into 18 patients with microvascular and 18 patients with macrovascular complications, recruited from the inpatients' departments and the outpatients' clinic. The control groupincluded fifteen (15) age- and sex-matched diabetic patientswithout vascular complications. Assay of RAGE gene polymorphism was performed by PCR-RFLP analysis. In this study, our results show that the genotypic frequencies of 374 T/A polymorphism were found at higher percentages in patients with diabetic microvascular complications and macrovascular complications than control group, yet it did not show statistically significant association with the presence of diabetic microvascular and macrovascular complications. In addition, there was no significant difference as regard A allele frequency between control and each of patients' group or when we combined the two patient groups. Regarding analysis of 429 T/C polymorphism in our study, our results showed no statistical difference between two patient groups and control group as regard genotypic and allelic frequencies.