Ivan Tkáč

KCNJ11 gene E23K variant and therapeutic response to sulfonylureas

AIMSnPotassium inwardly rectifier 6.2 subunit (Kir6.2) of the ATP-sensitive potassium (K(ATP)) channel encoded by KCNJ11 gene is a therapeutical target for sulfonylureas. KCNJ11 E23K polymorphism was associated with type 2 diabetes in genetic association studies. The aim of the present pharmacogenetic study was to examine the effect of sulfonylurea treatment on glycemic control in relationship to KCNJ11 E23K variant.nnnPATIENTS AND METHODSnOne hundred and one patients with type 2 diabetes who failed to achieve HbA1c<7% on previous metformin monotherapy were included to the study. Sulfonylurea drug was given in addition to metformin. The main outcome of the study was reduction in HbA1c level (ΔHbA1c) after 6-month sulfonylurea therapy. KCNJ11 genotypes were determined by real-time PCR with melting curve analysis.nnnRESULTSnAfter 6-month treatment, KCNJ11 K-allele carriers had higher decrease in HbA1c compared with EE homozygotes in the dominant genetic model (1.04±0.10 vs. 0.79±0.12%, p=0.036). In the log-additive model, greater mean reduction in HbA1c by 0.16% (95% CI 0.01-0.32, p=0.038) per each K-allele was observed. The relationship of treatment response with KCNJ11 genotype was also significant in the biggest subgroup of patients treated with gliclazide (n=55).nnnCONCLUSIONSnCarriers of the KCNJ11 K-allele have better therapeutic response to gliclazide. This observation might help to identify patients who will have the highest benefit from sulfonylurea treatment.

Variation in the glucose transporter gene SLC2A2 is associated with glycemic response to metformin

Metformin is the first-line antidiabetic drug with over 100 million users worldwide, yet its mechanism of action remains unclear. Here the Metformin Genetics (MetGen) Consortium reports a three-stage genome-wide association study (GWAS), consisting of 13,123 participants of different ancestries. The C allele of rs8192675 in the intron of SLC2A2, which encodes the facilitated glucose transporter GLUT2, was associated with a 0.17% (P = 6.6 × 10−14) greater metformin-induced reduction in hemoglobin A1c (HbA1c) in 10,577 participants of European ancestry. rs8192675 was the top cis expression quantitative trait locus (cis-eQTL) for SLC2A2 in 1,226 human liver samples, suggesting a key role for hepatic GLUT2 in regulation of metformin action. Among obese individuals, C-allele homozygotes at rs8192675 had a 0.33% (3.6 mmol/mol) greater absolute HbA1c reduction than T-allele homozygotes. This was about half the effect seen with the addition of a DPP-4 inhibitor, and equated to a dose difference of 550 mg of metformin, suggesting rs8192675 as a potential biomarker for stratified medicine.

Variants in Pharmacokinetic Transporters and Glycemic Response to Metformin: A Metgen Meta‐Analysis

Therapeutic response to metformin, a first‐line drug for type 2 diabetes (T2D), is highly variable, in part likely due to genetic factors. To date, metformin pharmacogenetic studies have mainly focused on the impact of variants in metformin transporter genes, with inconsistent results. To clarify the significance of these variants in glycemic response to metformin in T2D, we performed a large‐scale meta‐analysis across the cohorts of the Metformin Genetics Consortium (MetGen). Nine candidate polymorphisms in five transporter genes (organic cation transporter [OCT]1, OCT2, multidrug and toxin extrusion transporter [MATE]1, MATE2‐K, and OCTN1) were analyzed in up to 7,968 individuals. None of the variants showed a significant effect on metformin response in the primary analysis, or in the exploratory secondary analyses, when patients were stratified according to possible confounding genotypes or prescribed a daily dose of metformin. Our results suggest that candidate transporter gene variants have little contribution to variability in glycemic response to metformin in T2D.

Variation in KCNQ1 is associated with therapeutic response to sulphonylureas

Summary Background We aimed to analyse quantitative effects of treatment with sulphonylurea in addition to metformin on parameters of glycemic control in relation to KCNQ1 genotypes, and to identify factors predictive for the response to sulphonylurea treatment. Material/Methods Effect of 6-month sulphonylurea therapy in addition to metformin on glycemic control according to KCNQ1 genotypes was evaluated in 87 patients with type 2 diabetes who failed to achieve glycemic control on metformin monotherapy. KCNQ1 rs163184 (T>G) polymorphism was determined by real-time PCR with melting analysis of unlabeled probe. Results The reduction in fasting plasma glucose (ΔFPG) after 6-month sulphonylurea therapy significantly differed among 3 KCNQ1 genotype groups (ANOVA, p=0.017). In a recessive genetic model, carriers of the T-allele (TT+TG) achieved significantly lower FPG levels in comparison with patients with the GG genotype (6.95±0.13 vs. 7.50±0.21 mmol/L, p=0.033). Consequently, ΔFPG was significantly higher in the TT+TG group compared to the GG group (1.58±0.13 vs. 1.04±0.18 mmol/L, p=0.016). In multiple linear regression analysis KCNQ1 genotype (p=0.016) and baseline FPG (p<0.001) were the only significant independent predictors of ΔFPG (R2=0.48). Conclusions Our results suggest that the magnitude of FPG reduction after 6-month sulphonylurea treatment in addition to metformin in patients with type 2 diabetes is related to the variation in KCNQ1. The FPG response to sulphonylureas was significantly lower in carriers of the risk GG genotype.

Glutathione S-transferase M1 gene polymorphism is related to COPD in patients with non-small-cell lung cancer.

SummaryObjectiveOxidative stress contributes to the development of both lung cancer and chronic obstructive pulmonary disease (COPD). Antioxidative enzymes may protect against such damage. We hypothesized that genetic variations in glutathione S-transferase M1 and/or T1 genes (GSTM1 and GSTT1, respectively) may influence susceptibility to COPD in patients with non-small-cell lung cancer.Patients and methodsThe polymorphisms in GSTM1 and GSTT1 genes were examined in 110 patients (age: 63±1 years) with newly diagnosed non-small-cell lung cancer using the polymerase chain reaction. Respiratory function was assessed by bodyplethysmography.ResultsIn the GSTM1 null (−/−) genotype, both FEV1 and FEV1/FVC were significantly lower than in the GSTM1 plus genotype (GSTM1 −/+ or +/+) (75.8±2.5 versus 86.6±3.6%, p<0.02; 69.1±1.6 versus 77.0±2.4, p<0.01, respectively). Among the patients with GSTM1 null genotype, 49% suffered from COPD as opposed to 21% of patients with GSTM1 plus genotype. In contrast, no differences were seen in FEV1 or FEV1/FVC when comparing patients with GSTT1 null genotype and GSTT1 plus genotype (81.4±4.9 versus 79.3±2.3, p=NS; 71.1±2.9 versus 72.2±1.6, p=NS). Multiple stepwise regression analysis identified the GSTM1 genotype (p<0.02) as a significant independent predictor of FEV1 in this group of patients.ConclusionThe present study suggests that in patients with non-small-cell lung cancer the presence of at least one active allele in GSTM1 has a protective effect against the development of COPD.

Association between TCF7L2 Genotype and Glycemic Control in Diabetic Patients Treated with Gliclazide.

Previous studies showed associations between variants in TCF7L2 gene and the therapeutic response to sulfonylureas. All sulfonylureas stimulate insulin secretion by the closure of ATP-sensitive potassium (KATP) channel. The aim of the present study was to compare TCF7L2 genotype specific effect of gliclazide binding to KATP channel A-site (Group 1) with sulfonylureas binding to AB-site (Group 2). A total of 101 patients were treated with sulfonylureas for 6 months as an add-on therapy to the previous metformin treatment. TCF7L2 rs7903146 C/T genotype was identified by real-time PCR with subsequent melting curve analysis. Analyses using the dominant genetic model showed significantly higher effect of gliclazide in the CC genotype group in comparison with combined CT + TT genotype group (1.32 ± 0.15% versus 0.73 ± 0.11%, P adj = 0.005). No significant difference in ΔHbA1c between the patients with CC genotype and the T-allele carriers was observed in Group 2. In the multivariate analysis, only the TCF7L2 genotype (P = 0.006) and the baseline HbA1c (P < 0.001) were significant predictors of ΔHbA1c. After introducing an interaction term between the TCF7L2 genotype and the sulfonylurea type into multivariate model, the interaction became a significant predictor (P = 0.023) of ΔHbA1c. The results indicate significantly higher difference in ΔHbA1c among the TCF7L2 genotypes in patients treated with gliclazide than in patients treated with glimepiride, glibenclamide, or glipizide.

A pharmacogenetic association between a variation in calpain 10 ( CAPN10 ) gene and the response to metformin treatment in patients with type 2 diabetes

PurposeThe aim of the present study was to investigate possible associations of the single-nucleotide variants in six genes encoding the key molecules mediating the metformin pharmacodynamic effect with the response to treatment with metformin in patients with type 2 diabetes.MethodsOne hundred forty-eight drug-naïve patients with type 2 diabetes were included in the study. PRKAA1 rs249429, STK11 rs741765, PCK1 rs4810083, PPARGC1A rs10213440, HNF1A rs11086926, and CAPN10 rs3792269 variants were genotyped. The outcomes of the study were treatment success defined by achieving HbA1c <7xa0% and absolute reduction in HbAlc after 6-month metformin therapy. The relationships between genotypes and outcomes were evaluated in multivariate logistic and linear models. The level of statistical significance after Bonferroni correction was predefined as pu2009<u20090.0083.ResultsThe minor G-allele of CAPN10 rs3792269 Au2009>u2009G polymorphism was significantly associated with less treatment success with an odds ratio of 0.27 (95xa0% CI 0.12–0.62, pu2009=u20090.002) per variant allele. When the reduction in HbA1c was analyzed as a quantitative trait, G-allele was nominally associated with a smaller reduction in HbA1c (per allele βu2009=u2009−0.26, 95xa0% CI −0.50 to −0.02, pu2009=u20090.032). The reduction in HbA1c in minor allele carriers (24xa0% of study population) was smaller by 0.3xa0% in comparison with the major allele homozygotes.ConclusionsThe present study provides the first observation of an association between a variant in CAPN10 gene and the response to metformin therapy in patients with type 2 diabetes. This observation needs to be replicated in further studies in different populations.

Rapid and cost effective genotyping method for polymorphisms in PPARG, PPARGC1 and TCF7L2 genes.

Polymorphisms (rs1801282, rs8192678, rs7903146) of peroxisome proliferator-activated receptor gamma (PPARG), peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PPARGC1A) and transcription factor 7-like 2 (TCF7L2) have recently been associated with different diseases, mainly type 2 diabetes. An assay using unlabeled probes and the LightCycler or Rotor-Gene instruments was developed for genotyping of these three polymorphisms. Asymmetric polymerase chain reaction was used, followed by melting analysis of the unlabeled probe/ssDNA amplicon duplex. Samples with the target genotypes were accurately detected and easily distinguishable. Thus, genotyping using unlabeled probes is a rapid, accurate and cost effective closed-tube method. These assays demonstrated 100% specificity and sensitivity for the identification of selected polymorphisms in PPARG, PPARGC1A and TCF7L2 genes.

Interaction between angiotensin-converting enzyme genotype and glycaemic control influences lipoprotein levels in Type 2 diabetes mellitus

SummaryAimsTo evaluate the influence of the angiotensin-converting enzyme (ACE) insertion/deletion (I/D) polymorphism on lipid levels in patients with Type 2 diabetes.Patients and methods109 patients with Type 2 diabetes were included. The patients were not on any lipid-lowering treatment. The groups with different ACE genotypes had similar ages, sex distributions, body mass indices, systolic blood pressures and indices of glycaemic control. ACE gene I/D polymorphism was determined using polymerase chain reaction.ResultsThe mean apolipoprotein B (apoB) level was significantly higher in the group of DD homozygotes compared with the subjects with at least one insertion allele (DD: 1.21±0.25 g/l vs. ID+II: 1.04±0.27 g/l;P=0.007). Significant correlations between glycated haemoglobin (HbA10) and both apoB and cholesterol levels were found (r=0.27;P<0.01). For the apoB, this correlation was highly significant in the DD-genotype subgroup (r=0.54;P<0.01), and was not significant in the subgroup of patients with genotypes ID or II. In the multivariate analysis, HbA10 and the interaction of genotype DD with HbA10 were significant independent predictors of apoB (r2=0.17) and cholesterol levels.ConclusionThe present study showed that the interaction between the DD genotype of angiotensin-converting enzyme and chronic hyperglycaemia (expressed by HbA10 level) is related to higher plasma levels of atherogenic lipoproteins, such as apoB and cholesterol, in patients with Type 2 diabetes.

Effects of apolipoprotein E genotype on serum lipids in obstructive sleep apnoea

There is increasing evidence that intermittent hypoxia resulting from obstructive sleep apnoea (OSA) is independently associated with dyslipidaemia. Currently, no data exist on potential links between OSA-related dyslipidaemia and susceptibility genes for dyslipidaemia in such patients. Our aim was to study the effects of the apolipoprotein E (APOE) genotype and sleep apnoea severity on atherogenic dyslipidaemia in patients with OSA. 519 clinically stable subjects prospectively recruited at a tertiary referral teaching hospital underwent full polysomnography. APOE gene polymorphisms were assessed using real-time PCR. In all APOE genotype groups, serum triglycerides increased while high-density lipoprotein (HDL) cholesterol was reduced with increasing severity of OSA in each APOE genotype group, whereas the deleterious effects of OSA on serum apolipoprotein (Apo)B levels were observed in ε2 carriers and the ε3/ε3 genotype only. Nevertheless, the ε4 allele carriers had ApoB levels within the risk range, irrespective of nocturnal hypoxia. In addition, among patients with the high-risk ε4 genotype, those with the most severe nocturnal hypoxia had significantly higher triglyceride and lower HDL cholesterol levels compared with nonhypoxic ε4 subjects. APOE genotype and the oxygen desaturation index were both independent predictors of serum triglyceride levels (p=0.009 and p<0.001, respectively; R2=0.148) and ApoB levels (p=0.001 and p=0.003, respectively; R2=0.104). Our findings suggest that OSA has adverse effects on several lipid parameters over and above the effects carried by APOE genotype. Further st1udies are needed to analyse the effects of high-risk genotypes on metabolic and cardiovascular outcomes in patients with OSA. OSA has adverse effects on several lipid parameters in addition to the effects carried by the APOE genotype http://ow.ly/sKOUW