Growing prevalence of diabetes (type 2 as well as type 1) and its related morbidity due to vascular complications creates a large burden on medical care worldwide. Understanding the molecular pathogenesis of chronic micro-, macro- and avascular complications mediated by hyperglycemia is of crucial importance since novel therapeutic targets can be identified and tested. Thiamine (vitamin B1) is an essential cofactor of several enzymes involved in carbohydrate metabolism and published data suggest that thiamine metabolism in diabetes is deficient. This review aims to point out the physiological role of thiamine in metabolism of glucose and amino acids, to present overview of thiamine metabolism and to describe the consequences of thiamine deficiency (either clinically manifest or latent). Furthermore, we want to explain why thiamine demands are increased in diabetes and to summarise data indicating thiamine mishandling in diabetics (by review of the studies mapping the prevalence and the degree of thiamine deficiency in diabetics). Finally, we would like to summarise the evidence for the beneficial effect of thiamine supplementation in progression of hyperglycemia-related pathology and, therefore, to justify its importance in determining the harmful impact of hyperglycemia in diabetes. Based on the data presented it could be concluded that although experimental studies mostly resulted in beneficial effects, clinical studies of appropriate size and duration focusing on the effect of thiamine supplementation/therapy on hard endpoints are missing at present. Moreover, it is not currently clear which mechanisms contribute to the deficient action of thiamine in diabetes most. Experimental studies on the molecular mechanisms of thiamine deficiency in diabetes are critically needed before clear answer to diabetes community could be given.

Objectives: (i) to determine the extent of oxidative stress and DNA damage and repair using a panel of selected markers in patients with type 1 and type 2 diabetes mellitus (T1DM, T2DM), (ii) to find their possible relationships with diabetes compensation and duration, and finally (iii) to test for the effect of functional polymorphisms in the 8-oxoguanin DNA glycosylase (rs1052133), catalase (rs1001179) and superoxide dismutase (rs4880) genes on respective intermediate phenotypes. Methods: A total of 207 subjects (23 children and 44 adults with T1DM, 52 adult patients with T2DM and 88 healthy adult control subjects) were enrolled in the study. The following markers of redox state were determined in participants: erythrocyte superoxide dismutase (Ery-SOD), whole blood glutathione peroxidase (WB-GPx), erythrocyte glutathione (Ery-GSH), plasma total antioxidant capacity (P-tAOC) and plasma malondialdehyde (P-MDA). Furthermore, the extent of DNA damage and repair was ascertained using the following parameters: DNA single strand breaks (DNAssb), DNA repair capacity (DNArc) and DNA repair index (DNRI). Results: Comparison of T1DM vs. T2DM patients revealed significantly higher Ery-GSH content (P < 0.0001) and significantly lower Ery-SOD activity (P = 0.0006) and P-tAOC level (P < 0.0001) in T1DM subjects. T2DM diabetics exhibited a significant increase in DNAssb (P < 0.0001) and significant decrease in both DNArc (P < 0.0001) and DNRI (P < 0.0001) compared with T1DM patients. Patient’s age (irrespective of DM type) significantly correlated with DNAssb (r = 0.48, P < 0.0001), DNArc (r = −0.67, P < 0.0001) and DNRI (r = −0.7, P < 0.0001). Allele frequencies of all studied polymorphisms did not exhibit any significant association with the investigated parameters. Conclusion: We demonstrated significant age- and DM type-related changes of oxidative DNA modification and capacity for its repair in subjects with T1DM and T2DM.

Background. Pentose phosphate pathway (PPP) represents a potentially ‘protective’ mechanism in hyperglycaemia due to shunting of glycolytic intermediates into PPP reactions. We hypothesized that thiamine status (plasma and erythrocyte levels of thiamine and its esters) together with genetic variability in key PPP enzymes—transketolase (TKT), transaldolase and TKT-like—might contribute to the progression of diabetic nephropathy (DN) and mortality of diabetics.

Uric acid (UA) levels are associated with many diseases including those related to lifestyle. The aim of this study was to evaluate the influence of clinical and anthropometric parameters on UA and xanthine (X) levels during pregnancy and postpartum in women with physiological pregnancy and pregnancy complicated by gestational diabetes mellitus (GDM), and to evaluate their impact on adverse perinatal outcomes. A total of 143 participants were included. Analyte levels were determined by HPLC with ultraviolet detection (HPLC-UV). Several single-nucleotide polymorphisms (SNPs) in UA transporters were genotyped using commercial assays. UA levels were higher within GDM women with pre-gestational obesity, those in high-risk groups, and those who required insulin during pregnancy. X levels were higher in the GDM group during pregnancy and also postpartum. Positive correlations between UA and X levels with body mass index (BMI) and glycemia levels were found. Gestational age at delivery was negatively correlated with UA and X levels postpartum. Postpartum X levels were significantly higher in women who underwent caesarean sections. Our data support a possible link between increased UA levels and a high-risk GDM subtype. UA levels were higher among women whose glucose tolerance was severely disturbed. Mid-gestational UA and X levels were not linked to adverse perinatal outcomes.