ABSTRACT
BACKGROUND: Incretins have opened a new era in type 2 diabetes mellitus (T2DM) pathogenesis. The present study aimed to assess whether there is an association between GIPR rs2302382, GIPR rs1800437 and GLP-1R rs367543060 polymorphisms with T2DM or not and also to determine the effect of these polymorphisms on gastric inhibitory polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) levels. METHODS: One hundred and fifty T2DM patients and 150 healthy controls were included in the study. Polymorphisms of GIPR rs1800437, GIPR rs2302382 and GLP-1R rs367543060 were genotyped using restriction fragment length polymorphism (RFLP)-polymerase chain reaction (PCR), multiplex allele-specific PCR and RFLP-PCR respectively. GIP and GLP levels were measured by an enzyme-linked immunosorbent assay. RESULTS: We found a significant association of both the homozygous AA and the minor allele A of GIPR rs2302382 with T2DM. The frequency of haplotype C(rs2302382) G(rs1800437) was significantly higher in controls than in diabetics; odds ratio (95% confidence interval): 1.99 (1.44-2.75) (p < 0.001), whereas the haplotype A(rs2302382) C(rs1800437) was significantly higher in patients than controls. We did not find any association of GLP-1R rs367543060 polymorphism with T2DM. We found a significant increase in serum total GIP and a significant decrease of GLP-1 levels in T2DM patients. CONCLUSIONS: We reveal for the first time an association between the GIPR rs2302382 polymorphism and T2DM in Egyptians. Yet, there was no significant association of GIPR rs1800437 or GLP-1R rs367543060 with T2DM risk. The haplotype A (rs2302382) C (rs1800437) was associated with an increased risk of T2DM. Furthermore, there was a significant increase of GIP and a significant decrease of GLP-1 levels when diabetic patients were compared with controls. An important finding was that there was a relationship between both GIPR rs2302382 and rs1800437 variants and their cognate ligand levels.
