Vendula Bartáková

Genetic variability in enzymes of metabolic pathways conferring protection against non-enzymatic glycation versus diabetes-related morbidity and mortality

Abstract Background: We hypothesized that genetic variability in genes encoding enzymes metabolizing glycolytic intermediates produced in excess under hyperglycemic conditions [i.e., transketolase (TKT), transaldolase, TKT-like protein 1, fructosamine 3-kinase (FN3K), glyoxalase 1 and glucose-6-phosphate dehydrogenase] could influence progression of diabetic nephropathy (DN) and diabetes-related morbidity and mortality. Methods: A total of 19 single nucleotide polymorphisms (SNPs) in six candidate genes were studied in 314 type 2 diabetic subjects with variable stage of kidney disease (normo- and microalbuminuria, proteinuria, end-stage renal disease). SNP selection criteria were based on known functional effect and gene coverage. SNPs were detected using polymerase chain reaction based methods. Subjects were followed up for median of 38 months. Time-to-event analysis considered three end-points: 1) DN progression by at least one stage; 2) major cardiovascular event; and 3) all-cause mortality. Results: We found combined effect of TKT SNP rs11130362 and FN3K SNP rs1056534 on DN progression (p<0.01). Additionally, TKT rs3736156 alone and also in combination with the previous two SNPs exhibited significant effect on incidence of major cardiovascular events (p<0.01 and p=0.01, respectively). Conclusions: Genetic variability in rate-limiting enzymes of pathways proposed to confer hypothetical protection against hyperglycemia might act as an important determinant of hyperglycemia toxicity in long-standing diabetes.

Hyperuricemia contributes to the faster progression of diabetic kidney disease in type 2 diabetes mellitus

AIMS The aims of the study were (i) to ascertain prognostic value of serum uric acid (SUA) for diabetic kidney disease (DKD) progression and major adverse cardiovascular event (MACE) in a cohort of T2DM patients, (ii) to ascertain eventual protective effect of allopurinol treatment, (iii) to determine the effect of genetic variability in UA transporters on DKD progression, and (iv) to define optimal cut-off values for SUA in patients with DKD. METHODS Study comprised 422 subjects with diabetes duration at least 15years followed-up for a median of 43 [IQR 22-77] months. Participants were categorized into stable or progressors according to their change in albuminuria or chronic kidney disease (CKD) stage. At baseline, 68% patients had hyperuricemia (SUA≥420μmol/l for men and ≥360μmol/l for women and/or allopurinol treatment). Five SNPs in the SLC2A9 and ABCG2 genes were determined by PCR. RESULTS Time-to-event analysis with subgroups defined by the presence/absence of initial hyperuricemia revealed significant differences in all three end-points (P<0.0001 for DKD progression, P=0.0022 for MACE and P=0.0002 for death, log-rank test). Subjects with normal SUA not requiring allopurinol had median time to DKD progression 49months compared with remaining subjects (32months, P=0.0002, log-rank test). Multivariate Cox regression model revealed hyperuricemia (i.e. high SUA and/or allopurinol treatment) significant predictor of DKD progression independent of baseline CKD stage. Optimal cut-off values identified by ROC analysis for T2DM subjects were ≤377.5μmol/l for men and ≤309.0μmol/l for women. We found no differences in allele or genotype frequencies in selected SNPs between patients with and without hyperuricemia (all P>0.05). CONCLUSIONS Our study demonstrated that initial hyperuricemia or need for allopurinol is an independent risk factor for DKD progression and that SUA levels in diabetic subjects conferring protection against DKD progression might be lower than current cut-offs for general population.

Vitamin D Status in Women with Gestational Diabetes Mellitus during Pregnancy and Postpartum.

Of many vitamin D extraskeletal functions, its modulatory role in insulin secretion and action is especially relevant for gestational diabetes mellitus (GDM). The aims of the present study were to determine midgestational and early postpartum vitamin D status in pregnant women with and without GDM and to describe the relationship between midgestational and postpartum vitamin D status and parallel changes of glucose tolerance. A total of 76 pregnant women (47 GDM and 29 healthy controls) were included in the study. Plasma levels of 25(OH)D were measured using an enzyme immunoassay. Vitamin D was not significantly decreased in GDM compared to controls during pregnancy; however, both groups of pregnant women exhibited high prevalence of vitamin D deficiency. Prevalence of postpartum 25(OH)D deficiency in post-GDM women remained significantly higher and their postpartum 25(OH)D levels were significantly lower compared to non-GDM counterparts. Finally, based on the oGTT repeated early postpartum persistent glucose abnormality was ascertained in 15% of post-GDM women; however, neither midgestational nor postpartum 25(OH)D levels significantly differed between subjects with GDM history and persistent postpartum glucose intolerance and those with normal glucose tolerance after delivery.

Possibility to predict early postpartum glucose abnormality following gestational diabetes mellitus based on the results of routine mid-gestational screening.

Introduction Women with previous gestational diabetes mellitus (GDM) have increased risk of developing glucose abnormality, but current diagnostic criteria are evidence-based for adverse pregnancy outcome. The aims of our study were: (i) to ascertain a frequency of early conversion of GDM into permanent glucose abnormality, (ii) to determine predictive potential of current GDM diagnostic criteria for prediction of postpartum glucose abnormality and (iii) to find optimal cut-off values of oral glucose tolerance test (oGTT) to stratify GDM population according to postpartum risk. Materials and methods Electronic medical records of an ethnically homogenous cohort of women diagnosed and treated for GDM in a single medical centre during the period 2005–2011 who completed postpartum oGTT up to 1 year after the index delivery were retrospectively analysed (N = 305). Results Postpartum glucose abnormality was detected in 16.7% subjects. Mid-trimester oGTT values, respective area under the curve and HbA1c were significantly associated with early postpartum glucose abnormality (P < 0.05, Mann-Whitney) and exhibited significant predictive potential for postpartum glucose abnormality risk assessment. Optimal cut-off values for discrimination of at-risk sub-population were identified using ROC analysis and their comparison with WHO and IADPSG criteria exhibited superiority of IADPSG for risk-stratification of GDM population. Conclusion Risk-based stratification at the time of GDM diagnosis could improve efficiency of the post-gestational screening for diabetes. IADPSG criteria seem to optimally capture both perinatal and maternal metabolic risks and are therefore medically and economically justified.

Serum carboxymethyl-lysine, a dominant advanced glycation end product, is increased in women with gestational diabetes mellitus

AIMS The objective of the study was to measure one of the circulating Advanced Glycation End Products (AGEs) - Nε-(carboxymethyl)lysine (CML) - in a case-control study (n = 307) of pregnant women with gestational diabetes mellitus (GDM) and physiological pregnancies and to ascertain the factors contributing to CML levels and the potential relevance of CML for selected perinatal and postpartum outcomes. METHODS All subjects underwent oGTT between 24th and 30th week of gestation and GDM was diagnosed according to WHO criteria. CML was determined by ELISA using commercial kit. RESULTS Unadjusted and plasma protein adjusted CML levels were significantly higher in women with GDM compared to healthy controls (P = 0.00043 and P = 1x10(-5), respectively, Mann-Whitney). CML was significantly inversely correlated with both pre- and mid-gestational BMI, however, differences between GDM and control group remained significant even after adjustment for BMI. CML levels correlated with 1-h and 2-h post-load glycaemia during oGTT. CONCLUSION In conclusion, we found statistically significantly higher protein- and BMI-normalised CML levels measured during 24-30th week of gestation in women with GDM compared to healthy pregnant controls. Further studies are warranted to comprehensively asses the spectrum of AGEs in GDM and their relevance to future metabolic health of mother and offspring.

NOS3 894G>T Polymorphism is Associated With Progression of Kidney Disease and Cardiovascular Morbidity in Type 2 Diabetic Patients: NOS3 as a Modifier Gene for Diabetic Nephropathy?

Background/Aims: We have previously associated SNP 894G>T in the NOS3 gene with diabetic nephropathy (DN) using multi-locus analysis. Variant 894G>T has been widely studied as a DN susceptibility factor with contradictory results. In the present study we genotyped 894G>T in the cohort of prospectively followed type 2 diabetics with the aim to investigate its possible role in the progression of DN and development of morbidity and mortality associated with diabetes. Methods: 311 subjects with defined stage of DN were enrolled in the study and followed up for a median of 38 months. We considered three end-points: progression of DN, major cardiovascular event and all-cause mortality. Results: Considering baseline GFR, age at enrolment and diabetes duration as confounders, Cox regression analysis identified 894GT genotype as a risk factor for DN progression (HR = 1.843 [95% CI 1.088 - 3.119], P = 0.023) and 894TT genotype as a risk factor for major cardiovascular event (HR = 2.515 [95% CI 1.060 - 5.965], P = 0.036). Conclusion: We ascertained the significant effect of the NOS3 894G>T variant on DN progression and occurrence of major cardiovascular event in T2DM subjects. Based on these results NOS3 can be considered a modifier gene for DN.

Resting Heart Rate Does Not Predict Cardiovascular and Renal Outcomes in Type 2 Diabetic Patients

Elevated resting heart rate (RHR) has been associated with increased risk of mortality and cardiovascular events. Limited data are available so far in type 2 diabetic (T2DM) subjects with no study focusing on progressive renal decline specifically. Aims of our study were to verify RHR as a simple and reliable predictor of adverse disease outcomes in T2DM patients. A total of 421 T2DM patients with variable baseline stage of diabetic kidney disease (DKD) were prospectively followed. A history of the cardiovascular disease was present in 81 (19.2%) patients at baseline, and DKD (glomerular filtration rate < 60 mL/min or proteinuria) was present in 328 (77.9%) at baseline. Progressive renal decline was defined as a continuous rate of glomerular filtration rate loss ≥ 3.3% per year. Resting heart rate was not significantly higher in subjects with cardiovascular disease or DKD at baseline compared to those without. Using time-to-event analyses, significant differences in the cumulative incidence of the studied outcomes, that is, progression of DKD (and specifically progressive renal decline), major advanced cardiovascular event, and all-cause mortality, between RHR </≥65 (arbitrary cut-off) and 75 (median) bpm were not found. We did not ascertain predictive value of the RHR for the renal or cardiovascular outcomes in T2DM subjects in Czech Republic.