Endocrine Abstracts

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) not only functions as a central glycolytic enzyme but also is implicated in the process of apoptosis and gene transcription moving between the cytosol and nucleus. Oxidative stress modifies the activity of GAPDH.

The aim of the study was to determine whether oxidative stress (OS) in diabetics is associated with induction of the apoptotic process and higher GAPDH translocation to the nucleus in PBMCs.

GAPDH activity and -SH group content were determined in both the cytoplasmic and nuclear fraction of PBMCs collected from 20 diabetic and 20 control subjects. NF-kB p65 subunit and Bcl-2 levels were estimated in the nuclear and cytoplasmic cell fractions respectively. Chromatin integrity was assessed by diphenylamine (DPA) reaction and DNA laddering assay.

Intracellular OS was significantly higher in PBMCs from diabetic patients compared to controls as it is suggested by the -SH groups depletion in both cytoplasmic (P=0.030) and nuclear (P=0.003) cell fractions. The higher OS in the diabetics was accompanied by a significant increase in the nuclear NF-kB p65 subunit (P=0.015) and a three-fold decrease in cytoplasmic Bcl-2 levels (P=0.001). DNA damage was more evident in diabetics compared to controls as it is suggested by the DPA reaction (P=0.002) and DNA laddering assay. Compared to controls, GAPDH activity in PBMCs was significantly lower in diabetics (P=0.017). In spite of this reduction a significantly higher fraction of GAPDH activity was observed in the nuclear compartment of patients (P=0.001). In conclusion, diabetic OS activates the pro-apoptotic process in PBMCs and simultaneously the NF-kB, which may acts as anti-apoptotic factor. The higher GAPDH fraction that translocates into the nucleus may facilitates the repair of DNA damage, inserting new insights that link metabolic enzymes with energy production and cell survival.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.