Parkinson’s disease (PD) is a neurodegenerative disorder affecting the motor system and occurring in the central nervous system. One of the symptoms of PD is accumulation of Lewy bodies and Lewy neurites. The alpha-synuclein (SNCA) gene is part of the protein complex called Lewy body. The SNCA gene encoding a presynaptic protein product is thought to play a role in PD-related important pathways. It is suggested that there is a relationship between the risk of PD development and SNCA levels, and it is suggested that SNCA level is an important marker in PD diagnosis. Various polymorphisms have been identified in the 5′ and/or 3′ UTR regions of the SNCA gene, and as a result of these polymorphisms, changes occur in the binding of transcription factors. The identification of the roles of SNCA gene polymorphisms in PD development may enable the development of new methods for the treatment of PD.

The aim of this study was to investigate the relationship between MTHFR, IRS and CALCA gene polymorphisms and development of diabetic nephropathy (DN) in patients with type 2 diabetes mellitus (DM). Our study included 93 patients with type 2 DM diagnosed as having nephropathy and 95 controls diagnosed with type 2 DM without development of DN. Polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) were used to determine the genotype distributions of MTHFR, IRS and CALCA gene polymorphisms. The results showed no statistically significant difference between DN patients and type 2 DM controls in terms of genotype distributions of MTHFR (C677T, A1298C), IRS (IRS-1 Gly972Arg, IRS-2 Gly1057Asp) and CALCA T692C gene polymorphisms (p > 0.05). However, in terms of allele frequencies for the MTHFR A1298C gene, the frequency of the C allele was significantly higher in the DN patients compared to the controls (p < 0.05). In the IRS-2 Gly1057Asp gene polymorphism, the G allele frequency was significantly higher in the DN patients than in the type 2 DM controls (p < 0.05). In the DN group, the individuals with one or less mutant alleles were significantly more than in the control group in terms of the IRS-2 Gly1057Asp gene polymorphism (p < 0.05). The C allele frequency for the MTHFR A1298C gene polymorphism and the G allele frequency for the IRS-2 Gly1057Asp gene polymorphism were indicated to be potential a genetic risk factor for the development of DN in patients with type 2 DM who developed DN.