Genetic and biochemical investigation of the gamma-glutamylcyclotransferase role in predisposition to type 2 diabetes mellitus

Abstract

Background. Imbalance in the system of redox homeostasis is an important link in the pathogenesis of type 2 diabetes (T2D). Gamma-glutamyl cyclotransferase is an antioxidant defense enzyme directly involved in the metabolism of glutathione, an endogenous antioxidant.
 The aim of the study was to examine the association of single nucleotide polymorphisms (SNP) rs38420 (G A), rs4270 (T C), rs6462210 (C T) and rs28679 (G A) in GGCT gene with the risk of developing T2D.
 Materials and Methods. The study included 1022 T2D patients and 1064 healthy volunteers. Genotyping of GGCT gene loci was performed using iPLEX technology on a MassARRAY Analyzer 4 genome time-of-flight mass spectrometer (Agena Bioscience).
 Results. As a result, we identified for the first time the association of SNP rs4270 in the GGCT gene with the risk of T2D in the Russian population. We have also established genetic and environmental interactions associated with predisposition to the disease: protective effect of gamma-glutamyl cyclotransferase gene was observed only in non-smokers under condition of daily consumption of fresh vegetables and fruits, whereas in persons with insufficient consumption of plant foods, as well as in all smoking patients protective effect of GGCT was not observed. In patients with T2D, the level of hydrogen peroxide and glutathione monomer was sharply increased compared to the controls. SNP rs4270 was also found to be associated with elevated levels of reduced glutathione in the plasma of type 2 diabetics.
 Conclusion. Thus, for the first time it was established that polymorphic locus rs4270 in the GGCT gene is associated with a predisposition to T2D, but its relationship with the disease is modulated by smoking and fresh plant foods consumption.