Genetic risk factors and the anti-atherosclerotic effect of pioglitazone on carotid atherosclerosis of subjects with type 2 diabetes--a retrospective study

Matrix Gla protein polymorphism rs1800802 is associated with atheroma plaque progression and with cardiovascular events in a chronic kidney disease cohort

Background

Chronic kidney disease (CKD) is associated with increased atherosclerotic burden and higher risk for cardiovascular events (CVE). Atherosclerosis has a significant genetic component and, in CKD, it is influenced by mineral metabolism alterations. Therefore, genetic modifications of mineral metabolism-related proteins could affect atherosclerosis in CKD patients. In the present study we investigated the role of single nucleotide polymorphisms (SNPs) of the matrix gamma-carboxy glutamic acid protein (MGP) on atherosclerosis progression and CVE in a CKD cohort.

Methods

A total of 2187 CKD patients from the Observatorio Nacional de Aterosclerosis en Nefrologia (NEFRONA) study were genotyped for SNPs present in the matrix gamma-carboxy glutamic acid (Gla) protein (MGP) gene. Atheromatosis was detected by vascular ultrasound. Progression of atheromatosis, defined as an increase in territories with plaque, was assessed after 24 months. Patients were followed for 48 months for CVE. Association of SNPs with plaque progression was assessed by logistic regression and their capacity to predict CVE by Cox regression.

Results

Three SNPs of the MGP gene were analyzed. No association of the rs4236 or the rs1800801 SNPs was detected with any of the outcomes. However, patients homozygotes for the minor allele of the rs1800802 SNP showed higher adjusted risk for plaque progression [odds ratio 2.3 (95% confidence interval 1.06-4.9)] and higher risk of suffering a CVE [hazard ratio 2.16 (95% confidence interval 1.13-4.12)] compared with the rest of genotypes. No association of the SNP with total or dp-ucMGP levels was found in a subsample.

Conclusions

The rs1800802 polymorphism of MGP is associated with plaque progression and CVE in CKD patients.

Association of the ACE rs4646994 and rs4341 polymorphisms with the progression of carotid atherosclerosis in slovenian patients with type 2 diabetes mellitus

The current study was designed to reveal possible associations between the angiotensin-converting-enzyme (ACE) gene polymorphisms (rs4646994 and rs4341) with markers of carotid atherosclerosis in patients with type 2 diabetes mellitus (T2DM) in a 4-year-long follow-up study. Five hundred and ninety-five T2DM subjects and 200 control subjects were enrolled. Genotyping of ACE polymorphisms was performed using KASPar assays, and ultrasound examinations were performed twice (at the enrollment and at follow-up). With regard to the progression of atherosclerosis in subjects with T2DM, statistically significant differences were demonstrated in the change of the sum of carotid plaques thickness for the rs4646994 polymorphism. We did not demonstrate an association between the tested polymorphisms (rs4646994 and rs4341) and either carotid intima media thickness (CIMT) or CIMT progression in a 3.8-year period. In our study, we demonstrated that subjects with T2DM with the DD genotype of the rs4646994 [ACE insertion/deletion (I/D)] polymorphism had faster progression of atherosclerosis in comparison to subjects with other genotypes.

Pharmacogenomics and pharmacogenetics of thiazolidinediones: role in diabetes and cardiovascular risk factors

The most important goal in the treatment of patients with diabetes is to prevent the risk of cardiovascular disease (CVD), the first cause of mortality in these subjects. Thiazolidinediones (TZDs), a class of antidiabetic drugs, act as insulin sensitizers increasing insulin-dependent glucose disposal and reducing hepatic glucose output. TZDs including pioglitazone, rosiglitazone and troglitazone, by activating PPAR-γ have shown pleiotropic effects in reducing vascular risk factors and atherosclerosis. However, troglitazone was removed from the market due to its hepatoxicity, and rosiglitazone and pioglitazone both have particular warnings due to being associated with heart diseases. Specific genetic variations in genes involved in the pathways regulated by TDZs have demonstrated to modify the variability in treatment with these drugs, especially in their side effects. Therefore, pharmacogenomics and pharmacogenetics are an important tool in further understand intersubject variability per se but also to assess the therapeutic potential of such variability in drug individualization and therapeutic optimization.

The pharmacogenetics of type 2 diabetes: a systematic review

OBJECTIVE

We performed a systematic review to identify which genetic variants predict response to diabetes medications.

RESEARCH DESIGN AND METHODS

We performed a search of electronic databases (PubMed, EMBASE, and Cochrane Database) and a manual search to identify original, longitudinal studies of the effect of diabetes medications on incident diabetes, HbA1c, fasting glucose, and postprandial glucose in prediabetes or type 2 diabetes by genetic variation. Two investigators reviewed titles, abstracts, and articles independently. Two investigators abstracted data sequentially and evaluated study quality independently. Quality evaluations were based on the Strengthening the Reporting of Genetic Association Studies guidelines and Human Genome Epidemiology Network guidance.

RESULTS

Of 7,279 citations, we included 34 articles (N = 10,407) evaluating metformin (n = 14), sulfonylureas (n = 4), repaglinide (n = 8), pioglitazone (n = 3), rosiglitazone (n = 4), and acarbose (n = 4). Studies were not standalone randomized controlled trials, and most evaluated patients with diabetes. Significant medication-gene interactions for glycemic outcomes included 1) metformin and the SLC22A1, SLC22A2, SLC47A1, PRKAB2, PRKAA2, PRKAA1, and STK11 loci; 2) sulfonylureas and the CYP2C9 and TCF7L2 loci; 3) repaglinide and the KCNJ11, SLC30A8, NEUROD1/BETA2, UCP2, and PAX4 loci; 4) pioglitazone and the PPARG2 and PTPRD loci; 5) rosiglitazone and the KCNQ1 and RBP4 loci; and 5) acarbose and the PPARA, HNF4A, LIPC, and PPARGC1A loci. Data were insufficient for meta-analysis.

CONCLUSIONS

We found evidence of pharmacogenetic interactions for metformin, sulfonylureas, repaglinide, thiazolidinediones, and acarbose consistent with their pharmacokinetics and pharmacodynamics. While high-quality controlled studies with prespecified analyses are still lacking, our results bring the promise of personalized medicine in diabetes one step closer to fruition.

Current clinical evidence on pioglitazone pharmacogenomics

Pioglitazone is the most widely used thiazolidinedione and acts as an insulin-sensitizer through activation of the Peroxisome Proliferator-Activated Receptor-γ (PPARγ). Pioglitazone is approved for use in the management of type 2 diabetes mellitus (T2DM), but its use in other therapeutic areas is increasing due to pleiotropic effects. In this hypothesis article, the current clinical evidence on pioglitazone pharmacogenomics is summarized and related to variability in pioglitazone response. How genetic variation in the human genome affects the pharmacokinetics and pharmacodynamics of pioglitazone was examined. For pharmacodynamic effects, hypoglycemic and anti-atherosclerotic effects, risks of fracture or edema, and the increase in body mass index in response to pioglitazone based on genotype were examined. The genes CYP2C8 and PPARG are the most extensively studied to date and selected polymorphisms contribute to respective variability in pioglitazone pharmacokinetics and pharmacodynamics. We hypothesized that genetic variation in pioglitazone pathway genes contributes meaningfully to the clinically observed variability in drug response. To test the hypothesis that genetic variation in PPARG associates with variability in pioglitazone response, we conducted a meta-analysis to synthesize the currently available data on the PPARG p.Pro12Ala polymorphism. The results showed that PPARG 12Ala carriers had a more favorable change in fasting blood glucose from baseline as compared to patients with the wild-type Pro12Pro genotype (p = 0.018). Unfortunately, findings for many other genes lack replication in independent cohorts to confirm association; further studies are needed. Also, the biological functionality of these polymorphisms is unknown. Based on current evidence, we propose that pharmacogenomics may provide an important tool to individualize pioglitazone therapy and better optimize therapy in patients with T2DM or other conditions for which pioglitazone is being used.

Long-term effects of pioglitazone on carotid atherosclerosis in Japanese patients with type 2 diabetes without a recent history of macrovascular morbidity

AIM

No previous studies have evaluated the long-term anti-atherosclerotic effects of pioglitazone in Asian patients with type 2 diabetes. Therefore, the present study investigated the protective effects of pioglitazone on the progression of carotid intima-media thickness (IMT), an established surrogate marker of cardiovascular events in Japanese type 2 diabetic patients without a recent history of cardiovascular morbidity.

METHODS

This 2.5-4-year, randomized, open-label, blinded endpoint study was conducted in 6 centers across Japan. Patients received pioglitazone with or without other oral glucose-lowering drugs (excluding another thiazolidinedione) (n=89) or oral glucose-lowering drugs, excluding thiazolidinediones (n=97). Treatment was adjusted to achieve HbA(1c) <6.5%. The primary endpoints of the study were the absolute changes from the baseline to final visit in max- and mean-IMT in the average of bilateral common carotid arteries.

RESULTS

Pioglitazone induced carotid IMT regression compared to baseline measurements (from 1.060 ± 0.2368 to 0.992 ± 0.1921 mm; p=0.0042 in max-IMT and from 0.839 ± 0.1873 to 0.780 ± 0.1571 mm; p=0.0019 in mean-IMT). Although the between-group difference did not reach statistical significance, the regression of carotid IMT values was greater in the pioglitazone-treatment group than in the non-pioglitazone group, (max-IMT: -0.069 ± 0.2199 mm vs -0.031 ± 0.2327 mm, respectively; p=NS, mean-IMT: -0.058 ± 0.1718 mm vs -0.043 ± 0.1644 mm, respectively; p=NS).

CONCLUSIONS

Pioglitazone induced and maintained the long-term regression of carotid IMT in Japanese type 2 diabetic patients. This suggests that pioglitazone may inhibit the progression of atherosclerosis in this patient group. Further studies are required to verify these findings.