Effect of combined G6PD deficiency and diabetes on protein oxidation and lipid peroxidation

Oxidative Stress, an imbalance in the pro-oxidant/antioxidant homeostasis, occurs in many physiological and non-physiological processes and several human diseases, including diabetes mellitus (DM) and glucose-6-phosphate dehydrogenase (G6PD) deficiency. Since the incidence of G6PD deficiency in Jordan and many parts of the world is high, this study aimed to measure the effect of G6PD deficiency on the oxidative markers and the antioxidant glutathione (GSH) in diabetic and non-diabetic individuals.

Whole blood G6PD deficiency was screened by the fluorescent spot method, and erythrocyte G6PD activity was determined using a quantitative assay. Since protein carbonyl (PC) and malondialdehyde (MDA) are the most widely measured markers for protein and lipid oxidation, respectively, plasma PC and MDA, in addition to blood GSH were determined by spectrophotometric assays, as biomarkers of oxidative stress.

The incidence of G6PD deficiency among the diabetic subjects was 15%. PC level in patients with diabetes and in G6PD-deficient subjects was 5.5 to 6-fold higher than in non-diabetic subjects with sufficient G6PD levels (p<0.001). This fold increase was doubled in diabetic patients with G6PD deficiency (p<0.001). Furthermore, the MDA level was significantly increased by 28-41% in G6PD-deficient, diabetics with sufficient G6PD, and diabetics with G6PD deficiency compared to MDA level in non-diabetic with sufficient G6PD. On the other hand, GSH was significantly reduced to half in G6PD-deficient subjects and in diabetics with G6PD-deficiency.

The results showed that diabetes and G6PD deficiency increased protein oxidation and lipid peroxidation. However, the combination of both disorders has an additive effect only on protein oxidation. On the other hand, GSH level is only reduced in G6PD deficiency. In addition, diabetes and G6PD deficiency appear to be genetically linked since the incidence of G6PD deficiency among people with diabetes is more than the general population.