Thioredoxin Interacting Protein (TXNIP) Rs7212 Polymorphism Is Associated with Arterial Stiffness in the Brazilian General Population

RESEARCH LETTER Thioredoxin interacting protein (TXNIP) rs7212 polymorphism is associated with arterial stiffness in the Brazilian general population

Journal of Human Hypertension (2012) 26, 340 --342; been previously described.8 TXNIP rs7212 was chosen based on doi:10.1038/jhh.2011.102; published online 24 November 2011 the previous association of this marker with diabetes in the Brazilian population (Ferreira, NE, unpublished results). In the Thioredoxin interacting protein plays a pivotal role in several present study it was detected by polymerase chain reaction- important processes of cardiovascular homeostasis by func- restriction fragment length polymorphism assay. A 30--cycle PCR tioning as a biological sensor for biomechanical and oxidative was carried out using a 10 ml reactive solution containing (10 mM stress. However, the effects of genetic variants in the Tris-HCl, pH 9.0; 50 mM KCl; 2.5 mM MgCl2; 100 mM of each dNTP; 0.3 modulation of arterial stiffness are unknown. In this scenario, U Taq DNA Polymerase; 5 pmol of each primer; 50 ng of genomic the present study evaluated the relationship between the DNA template). PCR products were digested with 1 U of the HaeIII TXNIP rs7212 polymorphism and arterial stiffness. In the restriction enzyme and visualized by 3% agarose gel electrophor- overall sample and in the diabetic group, individuals carrying esis. Quality control was assessed by re-genotyping of 40 samples CG þ GG genotypes had higher PWV values compared with CC randomly selected and gave identical results in all tests. Statistical genotype group (10.0 vs 9.8 m sÀ1, P ¼ 0.03; 12.3 vs 11.2 m sÀ1, analyses were carried out using the SPSS 16.0 software (Chicago, P ¼ 0.01; respectively). Our findings indicated that the G allele IL, USA), with the level of significance set at Po0.05. Continuous may contribute to increased arterial stiffness in the Brazilian general population and suggest a possible interaction with diabetes. Table 1. Demographic and biochemical data according to TXNIP Increased central artery stiffness is an important determinant of rs7212 genotypes in the general population cardiovascular risk and epidemiological studies reported that increased arterial stiffness predicts mortality and morbidity, Parameters Genotypes P-value independently of other cardiovascular risk factors.1 The decrease in arterial elasticity may also be a consequence of various CC CG+GG 2 2 pathological processes, inappropriate lifestyle and genetic (n ¼ 1043) (n ¼ 475) factors.3 Thioredoxin interacting protein (TXNIP) is an endogenous a inhibitor of the thioredoxin system (TXN), and plays a pivotal role Ethnicity , % in several important processes of cardiovascular homeostasis by Caucasian descent 42.5 19.8 functioning as a biological sensor for biomechanical and oxidative Mulatto 45.7 61.3 o0.001 4 African descent 5.4 12.8 stress. The TXNIP gene, located on the long arm of chromosome Others 6.4 6.1 1q21, is modulated by mechanical stimuli from the cardiovascular system, as occurs during pressure-overload cardiac hypertrophy or Gender, % even physiologic fluid shear stress.5 Minn et al., in b-cell culture of Male 44.2 46.1 0.27 diabetic mice, demonstrated that the expression of TXNIP is Diabetesb, % 6.1 11.5 o0.001 increased and the over-expression of this protein is associated Age (in years) 45.2±10.7 44.1±10.9 0.07 6 BMIc,kgmÀ2 26.1±4.8 26.5±4.9 0.15 with increased apoptosis of b-cells. Yamawaki et al., using aorta c tissue, reported that the expression of TXNIP is reduced in regions SBP , mm Hg 127.0±21.1 128.9±22.0 0.10 c ± ± with more shear stress, thus leading to an increased activity of the DBP , mm Hg 83.8 13.9 84.8 13.9 0.26 PWVd,msÀ1 9.8±1.9 10.0±2.2 0.03 TXN system, and that this may be a possible mechanism involved c ± ± 5 MBP , mm Hg 98.2 15.6 99.4 15.7 0.14 in vascular dysfunction. In this scenario, the main aim of the PPc, mm Hg 43.3±13.3 44.3±13.7 0.20 present work was to evaluate the relationship between the TXNIP Glucosec,mgdlÀ1 103.6±28.3 107.8±38.4 0.02 rs7212 polymorphism and arterial stiffness phenotype in the Total cholesterolc,mgdlÀ1 215.3±47.9 214.0±47.7 0.62 Brazilian general population. LDL cholesterolc,mgdlÀ1 142.9±38.5 142.4±41.2 0.81 Our study sample was based on a cross-sectional design in the HDL cholesterolc,mgdlÀ1 45.4±12.5 45.6±12.2 0.88 c À1 urban population of Vitoria City, Brazil.7 A sample of 2044 Triglycerides ,mgdl 140.5±143.4 129.9±87.5 0.14 participants of either gender, 25--64 years of age, was chosen Abbreviations: BMI, body mass index; CI, confidence interval; DBP, diastolic according to the nearest birthday after a random selection of blood pressure; HDL, high-density lipoproteıń; LDL, low-density domiciles. Of the 2044 participants invited, 1518 individuals lipoprotein; MBP, mean blood pressure; PP, pulse pressure; PWV, pulse wave attended the clinic visit and were further evaluated for: anthro- velocity; SBP, systolic blood pressure. pologic indices, ethnicity, blood pressure (BP), arterial stiffness and P-values shown as bold are significatives. aEthnicity was categorized in lipid profile. This study was approved by the Committee for Caucasian descent, African descent, Mulatto (person with a known family history of admixture between Caucasian and African descent) and other research on Human Subjects of the Heart Institute and informed b consents were obtained from all participants. Arterial stiffness was (American Indians and Oriental descent). Diabetes was defined as fasting glucose X126 mg dlÀ1 or previous diagnosis. cDenotes adjusting for age, measured by carotid-femoral pulse wave velocity (PWV). The gender and ethnicity. dDenotes adjusting for ethnicity, mean BP and age. validation of this automatic method and its reproducibility has Research Letter 341 Diabetes No Ye s 15.0 15.0 * 14.0 14.0 13.0 13.0 p=0.01 12.0 p=0.53 12.0 11.0 11.0 10.0 10.0

PWV (m/s) 9.0 PWV (m/s) 9.0 8.0 8.0 7.0 7.0 CC CG+GG CC CG+GG TXNIP Genotype TXNIP Genotype Figure 1. Association of rs7212 TXNIP polymorphism with pulse wave velocity (PWV) values according to the absence or presence of diabetes. In the diabetic group, individuals carrying CG þ GG genotypes had higher PWV values compared with CC genotype group (12.3 vs 11.2 m sÀ1, respectively; P ¼ 0.01). However, no difference in PWV values was found in non-diabetic group (P ¼ 0.53).

variables were expressed as the mean±s.d. (standard deviation). PWV values compared with individuals carrying the CC genotype, Univariate and multivariate logistic regression analyses were even after adjustment for covariates. Interestingly, this association employed to assess the relationship between TXNIP rs72712 seems to be restricted to diabetic individuals, a pathological polymorphism and arterial stiffness status with adjustment for the condition know to have a dysfunctional TXN system. effects of confounding phenotypes. Genotypic frequencies were It is well established that TXNIP protein has a pivotal role in 69% for CC; 28% for CG and 3% for GG; and frequency of allele G redox regulation, since its interaction with the TXN system can was of 17.5%. Distribution of the genotypes in the overall sample activate various cellular signaling molecules, as in vascular and in the diabetic and non-diabetic groups were in accordance function and glucose metabolism.4,10 Based on this, we suggest with the Hardy--Weinberg equilibrium (P ¼ 0.09, X2 ¼ 2.9; P ¼ 0.14, that TXNIP rs7212 polymorphism may be associated with X2 ¼ 2.2; P ¼ 0.52, X2 ¼ 0.4; respectively). Based on our sample size significant changes in the vascular bed due to an increased (1518 individuals), allele and genotype frequencies (69% for CC; reactive oxygen species production, which are widely associated 28% for CG and 3% for GG; and allele G frequency of 17.5%), and with diabetes and known to lead to increased arterial stiffness.11 observed PWV sample mean and standard deviation, our study had 80% power to detect an effect of 0.3 or higher in PWV mean value associated with the presence of at least one G allele. What is known about this topic Differences in age, gender, body mass index, systolic BP, TXNIP has a pivotal role in several important processes of diastolic BP, mean BP, pulse pressure, total cholesterol, LDL- cardiovascular homeostasis by functioning as a biological sensor for cholesterol, HDL-cholesterol and triglycerides levels according to biomechanical and oxidative stress. TXNIP gene polymorphisms have been associated with dysfunction genotype groups were not observed (CC vs CG þ GG). However, in glucose metabolism. individuals carrying CG or GG genotypes had higher PWV values À1 compared with individuals carrying CC (10.0 vs 9.8 m s ; P ¼ 0.03, What this study adds respectively), adjusting for age, MBP and ethnicity (Table 1). TXNIP rs7212 polymorphism is associated with arterial stiffness in the The ethnicity distribution according to genotypes was signifi- general population. cantly different. However, our analysis remains significant even There is a significant interaction between TXNIP genotype and after adjustment for ethnicity plus potential confounders. In diabetes leading to increased arterial stiffness. addition, in a stratified analysis for ethnicity, African and Caucasian descents carrying CG þ GG genotypes had higher PWV values compared with CC genotype (10.4 vs 9.3 m sÀ1, Po0.01; 9.9 vs CONFLICT OF INTEREST À1 9.6 m s , P ¼ 0.04; respectively), adjusting for age and MBP. The authors declare no conflict of interest. Nonetheless, it should be highlighted that it is difficult to completely exclude the participation of these variables in the RO Alvim1, PCJL Santos1, NE Ferreira1, JG Mill2, JE Krieger1 observed results. and AC Pereira1 In the diabetic group, individuals carrying CG þ GG genotypes 1Laboratory of Genetics and Molecular Cardiology, Heart Institute had higher PWV values compared with CC genotype group (12.3 (InCor), University of Sao Paulo Medical School, Sao Paulo, Brazil and À1 vs 11.2 m s , respectively; P ¼ 0.01), adjusting for age, MBP and 2Department of Physiology, Espirito Santo Federal University, ethnicity. However, no difference in PWV values was found in non- Espirito Santo, Brazil. diabetic individuals (P ¼ 0.53) (Figure 1). Interestingly, after the E-mail: [email protected] addition of diabetes in the multivariate model, not only TXNIP genotype was significantly associated with PWV (Po0.001) (adjusted for mean arterial blood pressure), but also a statistically significant interaction term (P ¼ 0.02) between TXNIP and diabetes REFERENCES was also observed. 1 Meaume S, Benetos A, Henry OF, Rudnichi A, Safar ME. Aortic pulse wave velocity Studies focusing on TXNIP genetic variants and vascular predicts cardiovascular mortality in subjects 470 years of age. Arterioscler Thromb phenotypes are absent in the literature. Nonetheless, there are Vasc Biol 2001; 21(12): 2046 --2050. 2 Sakuragi S, Abhayaratna WP. Arterial stiffness: methods of measurement, few studies involving TXNIP gene polymorphisms and glucose 6,9 physiologic determinants and prediction of cardiovascular outcomes. Int J Cardiol metabolism. To our knowledge, this is the first study linking a 2010; 138(2): 112 --118. 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