Plasma ferritin levels, genetic variations in HFE gene, and coronary heart disease in Chinese: a case-control study

Sex-Specific Association Between Iron Status and the Predicted 10-Year Risk for Atherosclerotic Cardiovascular Disease in Hypertensive Patients

Serum ferritin (SF) and haemoglobin (Hb) are widely used in clinical practice to assess iron status. Studies exploring the relationship of SF and Hb with atherosclerotic cardiovascular disease (ASCVD) risk have yielded conflicting results, and some indicated sex specificity. Hypertensive patients have abnormal iron status. However, research on patients with hypertension is limited. We aim to investigate the sex-specific links of SF and Hb with the predicted 10-year ASCVD risk in hypertensive patients. This cross-sectional study included 718 hypertensive men and 708 hypertensive women. The predicted 10-year ASCVD risk was calculated based on the China-PAR equation. The dose-response curves were illustrated by fitting linear and quadratic models. In hypertensive men, the iron status fits for a quadratic model for ASCVD risk, showing a U-shape. After adjusting for potential confounding factors, the regression coefficients and 95% confidence intervals (95% CI) across tertile of SF were 0.0 (reference), - 0.99 (- 1.65, - 0.33) and - 0.22 (- 0.88, 0.44), and of Hb were 0.0 (reference), - 0.74 (- 1.41, - 0.08) and - 0.77 (- 1.46, - 0.08). In hypertensive women, iron status was linearly and positively associated with ASCVD risk. Per one unit increment of log-transformed SF as well as Hb was associated with a 1.22 (95% CI: 0.97, 1.48) and 0.04 (95% CI: 0.02, 0.07) increased in ASCVD risk score, respectively. A significant interaction between iron status and inflammation on ASCVD risk was observed in hypertensive women. SF and Hb showed a U-shape with ASCVD risk in hypertensive men; however, a positive linear relationship was observed in hypertensive women.

Association between interleukin-35 polymorphisms and coronary heart disease in the Chinese Zhuang population: a case-control study

OBJECTIVES

Inflammatory cytokines play an important role in the pathogenesis of cardiovascular disease. Few studies have investigated the association between interleukin-35 (IL-35) genetic variants and the risk of coronary heart disease (CHD). We examined the association between IL-35 polymorphisms and CHD in the Chinese Zhuang population.

PATIENTS AND METHODS

A total of 707 CHD patients and 707 age-matched and sex-matched controls were enrolled in this case-control study. Genotypes of the single nucleotide polymorphisms (SNPs) of IL-35, including rs428253, rs6613, rs9807813, rs2243115, rs568408, rs582054, rs583911, rs4740, and rs393581, were examined by MassArray. Plasma IL-35 level was measured using an enzyme-linked immunosorbent assay. The multivariate logistic regression model was used to evaluate the association between the SNPs and the risk of CHD.

RESULTS

In the Chinese Zhuang population, compared with the GG genotype of EBI3 rs428253, individuals with the CC genotype had a 2.02-fold (95% confidence interval: 1.07-3.84, P=0.031) higher risk of CHD. Further adjustment for potential risk factors did not alter the positive association (CC vs. GG, odds ratio=2.30, 95% confidence interval: 1.16-4.54, P=0.042). SNPs rs4740, rs2243115, rs568408, and rs582054 were not statistically related to the risk of CHD. The plasma IL-35 levels showed a marginally significant difference between rs428253 genotypes [GG: 13.39 (7.89-19.25) vs. CC+GC: 17.53 (8.98-22.56) pg/ml, P=0.057].

CONCLUSION

The EBI3 rs428253 CC genotype was associated with an increased risk of CHD in the Chinese Zhuang population, although no significant difference in IL-35 levels was observed between genotypes in healthy controls.

NPR-C gene polymorphism is associated with increased susceptibility to coronary artery disease in Chinese Han population: a multicenter study

To find a new locus that confers significant susceptibility to CAD in Chinese Han population, a genome-wide association study in 200 “extreme individuals” from a Shandong cohort and a pathway-based candidate gene study from a Shanghai cohort (293 CAD/293 controls) were simultaneously performed. Amongst them, 13 SNPs associated with CAD were selected to conduct validation and replication studies in additional 3363 CAD patients and 3148 controls. A novel locus rs700926 in natriuretic peptide receptor C (NPR-C) was identified in Shandong and Hubei cohorts. Then rs700926 and other nine tag SNPs were genotyped in four geographically different populations (Shandong, Shaanxi, Hubei and Sichuan cohorts), and 6 SNPs (rs700926, rs1833529, rs2270915, rs17541471, rs3792758 and rs696831) showed stronger association with CAD, regardless of single or combined analysis. We further genotyped rs2270915 and 10 additional tag SNPs in a central China cohort and identified rs12697273 and rs10066436 as the loci associated with CAD. All these positive associations remained significant after adjustment for traditional risk factors of CAD. NPR-C gene SNPs significantly contribute to CAD susceptibility in the Chinese Han population.

A functional variant in ST2 gene is associated with risk of hypertension via interfering MiR-202-3p

Recent studies have suggested that interleukin 1 receptor-like 1 (ST2) plays a critical role in pathogenesis of several cardiovascular disease conditions. In this study, we examined association of 13 single nucleotide polymorphisms (SNPs) of ST2 gene with essential hypertension (EH) risk in 1151 patients with EH and 1135 controls. Our study showed that variants rs11685424, rs12999364 and rs3821204 are highly associated with an increase in risk of EH, while rs6543116 is associated with a decrease risk of EH. Notably, in silico analyses suggested the G>C change of rs3821204, which located within the 3'UTR of soluble ST2 mRNA, disrupted a putative binding site for miR202-3p. Functional analyses suggested that miR-202-3p significantly decreased soluble ST2-G mRNA stability and inhibited its endogenous expression. Furthermore, we found increased plasma-soluble ST2 (sST2) level was highly associated with CC genotype of rs3821204 in vivo. Taken together, our findings provide the first evidence that genetic variants in ST2 gene are associated with EH risk and variant rs3821204 may influence the development of EH by controlling sST2 expression.

Birth Characteristics and Childhood Leukemia Risk: Correlations With Genetic Markers

Birth characteristics such as birth order, birth weight, birth defects, and Down syndrome showed some of the first risk associations with childhood leukemia. Examinations of correlations between birth characteristics and leukemia risk markers have been limited to birth weight-related genetic polymorphisms. We integrated information on nongenetic and genetic markers by evaluating the relationship of birth characteristics, genetic markers for childhood acute lymphoblastic leukemia (ALL) susceptibility, and ALL risk together. The multiethnic study consisted of cases with childhood ALL (n=161) and healthy controls (n=261). Birth characteristic data were collected through questionnaires, and genotyping was achieved by TaqMan SNP Genotyping Assays. We observed risk associations for birth weight over 4000 g (odds ratios [OR]=1.93; 95% confidence interval [CI], 1.16-3.19), birth length (OR=1.18 per inch; 95% CI, 1.01-1.38), and with gestational age (OR=1.10 per week; 95% CI, 1.00-1.21). Only the HFE tag single-nucleotide polymorphism (SNP) rs9366637 showed an inverse correlation with a birth characteristic, gestational age, with a gene-dosage effect (P=0.005), and in interaction with a transferrin receptor rs3817672 genotype (Pinteraction=0.05). This correlation translated into a strong association for rs9366637 with preterm birth (OR=5.0; 95% CI, 1.19-20.9). Our study provides evidence for the involvement of prenatal events in the development of childhood ALL. The inverse correlation of rs9366637 with gestational age has implications on the design of HFE association studies in birth weight and childhood conditions using full-term newborns as controls.

Associations between variants in IL-33/ST2 signaling pathway genes and coronary heart disease risk

The IL-33/ST2 signaling pathway plays an important role in coronary artery disease (CHD); however, few studies have explored how variants in IL-33/ST2 genes influence CHD risk. Here, we examined the association between genetic variants in IL-33, ST2, and IL-1RAcP of the IL-33/ST2 axis and the risk of CHD. We conducted a case-controlled study with 1146 CHD cases and 1146 age- and sex-frequency-matched controls. Twenty-eight single nucleotide polymorphisms (SNPs) in IL-33, ST2, and IL-1RAcP were genotyped by Sequenom MassArray and TaqMan assay. Logistic regression was used to analyze these associations. The SNP rs4624606 in IL-1RAcP was nominally associated with CHD risk. The AA genotype was associated with a 1.85-fold increased risk of CHD (95% confidence interval (CI) = 1.01-3.36; p = 0.045) compared to the TT genotype. Further analysis showed that AA carriers also had a higher risk of CHD than TT + TA carriers (odds ratio (OR) = 1.85; 95% CI = 1.85-3.35; p = 0.043). However, no significant association was observed between variants in IL-33/ST2 genes and CHD risk. Further studies are needed to replicate our results in other ethnic groups with larger sample size.

Iron, oxidative stress, and redox signaling in the cardiovascular system

The redox state of the cell is predominantly dependent on an iron redox couple and is maintained within strict physiological limits. Iron is an essential metal for hemoglobin synthesis in erythrocytes, for oxidation-reduction reactions, and for cellular proliferation. The maintenance of stable iron concentrations requires the coordinated regulation of iron transport into plasma from dietary sources in the duodenum, from recycled senescent red cells in macrophages, and from storage in hepatocytes. The absorption of dietary iron, which is present in heme or nonheme form, is carried out by mature villus enterocytes of the duodenum and proximal jejunum. Multiple physiological processes are involved in maintaining iron homeostasis. These include its storage at the intracellular and extracellular level. Control of iron balance in the whole organism requires communication between sites of uptake, utilization, and storage. Key protein transporters and the molecules that regulate their activities have been identified. In this field, ferritins and hepcidin are the major regulator proteins. A variety of transcription factors may be activated depending on the level of oxidative stress, leading to the expression of different genes. Major preclinical and clinical trials have shown advances in iron-chelation therapy for the treatment of iron-overload disease as well as cardiovascular and chronic inflammatory diseases.

Erythrocyte membrane fatty acid composition is related to overloaded plasma ferritin in Chinese males with angiographic coronary artery disease

Not only is iron deficiency an abnormal iron status, but iron overload is also harmful for human health. It has been reported that overloaded iron stores are positively associated with increased coronary artery disease (CAD) risk, which is called the "iron-heart hypothesis". Previous studies evaluating the relationships between fatty acids (FAs) and body iron status only focused on participants with iron deficiency. However, whether FA composition is related to overloaded iron remains unclear. Therefore, this study was designed to investigate the relationships between erythrocyte membrane FA (Ery-FA) composition and overloaded body iron status as measured by plasma ferritin levels in Chinese CAD patients. A total of 446 subjects with angiographically identified CAD (mean age 63.1 years, 76.9% males) were recruited in a hospital between 2009 and 2010. Ery-FAs were measured by gas chromatography and the activities of FA desaturases, which are involved in the de novo synthesis of unsaturated FAs, were evaluated by using FA product-to-precursor ratios. Results showed that the average iron status was a bit overloaded in the population (median ferritin levels of 234.1 ng mL(-1) and 40.4% males of overload). Moreover, in males, saturated FAs (SFAs) were positively correlated (22 : 0, r = 0.182, p = 0.001; 24 : 0, r = 0.214, p < 0.001), whereas monounsaturated FAs (MUFAs) and n-6 polyunsaturated FAs (PUFAs) were negatively correlated (18 : 1n-9, r = -0.120, p = 0.028; 18 : 2n-6, r = -0.216, p < 0.001) with plasma ferritin levels. A negative correlation (r < 0, p < 0.05) between stearoyl-CoA desaturase (SCD) activity and ferritin levels was also found in males. However, all the significant associations above were not observed in females. In conclusion, the Ery-FA composition was related to overloaded plasma ferritin levels only in Chinese males with angiographic CAD, which might be linked to the change of SCD activity. The results may contribute to the understanding of the mechanism of the iron-heart hypothesis.

Iron: protector or risk factor for cardiovascular disease? Still controversial

Iron is the second most abundant metal in the Earth’s crust. Despite being present in trace amounts, it is an essential trace element for the human body, although it can also be toxic due to oxidative stress generation by the Fenton reaction, causing organic biomolecule oxidation. This process is the basis of numerous pathologies, including cardiovascular diseases (CVD). The relationship between iron and cardiovascular disease was proposed in 1981 by Jerome Sullivan. Since then, numerous epidemiological studies have been conducted to test this hypothesis. The aim of this review is to present the main findings of the chief epidemiological studies published during the last 32 years, since Sullivan formulated his iron hypothesis, suggesting that this element might act as a risk factor for cardiovascular disease. We have analyzed 55 studies, of which 27 supported the iron hypothesis, 20 found no evidence to support it and eight were contrary to the iron hypothesis. Our results suggest that there is not a high level of evidence which supports the hypothesis that the iron may be associated with CVD. Despite the large number of studies published to date, the role of iron in cardiovascular disease still generates a fair amount of debate, due to a marked disparity in results.

Meta-analyses of HFE variants in coronary heart disease

AIM

HFE gene variants can cause hereditary hemochromatosis (HH) that often comes along with an increased risk of coronary heart disease (CHD). The goal of our study is to assess the contribution of four HFE gene variants to the risk of CHD.

METHODS AND RESULTS

We conducted four meta-analyses of the studies examining the association between four HFE gene variants and the risk of CHD. A systematic search was conducted using MEDLINE, EMBASE, Web of Science and China National Knowledge Infrastructure (CNKI), Wanfang Chinese Periodical.

RESULTS

Meta-analyses showed that HFE rs1799945-G allele was associated with a 6% increased risk of CHD (P=0.02, odds ratio (OR)=1.06, 95% confidence interval (CI)=1.01-1.11). However, no association between the other three HFE gene variants (rs1800562, rs1800730, and rs9366637) and CHD risk was observed by the meta-analyses (all P values>0.05). In addition, the results of our case-control study indicated that rs1800562 and rs1800730 were monomorphic, and that rs1799945 and rs9366637 were not associated with CHD in Han Chinese.

CONCLUSIONS

Our meta-analysis suggested that a significant association existed between rs1799945 mutation and CHD, although this mutation was rare in Han Chinese.

Correlation of hemochromatosis gene mutations and cardiovascular disease in hemodialysis patients

BACKGROUND AND OBJECTIVES

Cardiovascular disease (CVD) is a major cause of death in hemodialysis (HD) patients. Hemochromatosis (HFE) gene mutations are reported to be associated with CVD. The present study aims to investigate the association of HFE gene polymorphism with CVD in HD patients.

DESIGN AND SETTINGS

Cross-sectional case-control.

METHODS

C282Y/H63D mutations of HFE gene were evaluated in 560 HD patients and 480 healthy controls from 4 HD centers in North China. The results obtained from this evaluation process were correlated with biochemical parameters including iron status (serum iron, ferritin, and transferrin concentration), cardiovascular disease, and inflammation marker CRP, IL-6, TNF-a.

RESULTS

No C282Y mutations were detected in HD patients or healthy controls in this study. The genotype of H63D heterozygous mutation was similar in HD patients with CVD, HD patients without CVD, and controls. H63D homozygous mutation was 7.4% (19/257), 3.1% (9/303), and 1.0% (5/480) for the 3 groups, respectively. Compound heterozygosity was not found in this study. The relative risk for CVD in HD patients with H63D homozygous mutation was 2.59 (95% CI: 1.15-5.84). H63D homozygous mutation had significantly higher serum ferritin concentrations compared with wild-type individuals. Moreover, HD patients had significantly higher levels of inflammatory biomarkers such as CRP, IL-6, and TNF-a. The multivariate logistic regression analysis revealed that H63D mutation instead of ferritin level was an independent risk factor of CVD for HD patients.

CONCLUSIONS

Our study demonstrates for the first time that there was an association between H63D homozygous mutations and CVD in HD patients. Elevated serum CRP, IL-6, and TNF-a levels were also related to CVD in HD patients.

Short (GT) ( n ) repeats in heme oxygenase-1 gene promoter are associated with lower risk of coronary heart disease in subjects with high levels of oxidative stress

Although (GT) ( n ) repeats in heme oxygenase-1 (HO-1) promoter may modulate gene transcriptional activity, the association between (GT) ( n ) repeats polymorphism and risk of coronary heart disease (CHD) from different levels of oxidative stress (OS) is unknown. We determined the allelic frequencies of (GT) ( n ) repeats in the HO-1 gene promoter and plasma malonaldehyde (MDA) as biomarkers of OS in 2,298 pairs of CHD patients and controls in the Chinese population. Furthermore, we measured MDA in culture mediums and HO-1 expressions levels in cell lysates of endothelial cells carrying various (GT) ( n ) genotypes under different concentrations of H(2)O(2). Compared with L/L genotype (>25 repeats) carriers, the adjusted odd ratios for S/S genotype (≤25 repeats) in subjects with different levels of OS (MDA < 1.83, 1.83-2.91, >2.91 μmol/L) were 1.06 (95%CI, 0.75 to 1.49), 0.79 (95%CI, 0.55 to 1.12), and 0.60 (95%CI, 0.44 to 0.81), respectively (P (interaction) = 0.002). In biological experiments, compared with endothelial cells carrying L/L genotype, cells with S/S genotype did not have a significantly higher HO-1 expression under 0 μmol/L H(2)O(2), but displayed a significantly higher HO-1 expression under 50 μmol/L H(2)O(2) (P (interaction) = 0.003). S/S genotype in HO-1 gene promoter is associated with a lower risk of CHD in subjects with higher levels of OS, because under conditions of high OS, the S/S genotype has higher levels of HO-1, an antioxidant.