The influence of smoking and homocysteine on subclinical atherosclerosis is modified by the connexin37 C1019T polymorphism - The Cardiovascular Risk in Young Finns Study

Circulating cell-free DNA in health and disease - the relationship to health behaviours, ageing phenotypes and metabolomics

Circulating cell-free DNA (cf-DNA) has emerged as a promising biomarker of ageing, tissue damage and cellular stress. However, less is known about health behaviours, ageing phenotypes and metabolic processes that lead to elevated cf-DNA levels. We sought to analyse the relationship of circulating cf-DNA level to age, sex, smoking, physical activity, vegetable consumption, ageing phenotypes (physical functioning, the number of diseases, frailty) and an extensive panel of biomarkers including blood and urine metabolites and inflammatory markers in three human cohorts (N = 5385; 17-82 years). The relationships were assessed using correlation statistics, and linear and penalised regressions (the Lasso), also stratified by sex.cf-DNA levels were significantly higher in men than in women, and especially in middle-aged men and women who smoke, and in older more frail individuals. Correlation statistics of biomarker data showed that cf-DNA level was higher with elevated inflammation (C-reactive protein, interleukin-6), and higher levels of homocysteine, and proportion of red blood cells and lower levels of ascorbic acid. Inflammation (C-reactive protein, glycoprotein acetylation), amino acids (isoleucine, leucine, tyrosine), and ketogenesis (3-hydroxybutyrate) were included in the cf-DNA level-related biomarker profiles in at least two of the cohorts.In conclusion, circulating cf-DNA level is different by sex, and related to health behaviour, health decline and metabolic processes common in health and disease. These results can inform future studies where epidemiological and biological pathways of cf-DNA are to be analysed in details, and for studies evaluating cf-DNA as a potential clinical marker.

Genetic deletion of connexin 37 causes polyuria and polydipsia

The connexin 37 (Cx37) channel is clustered at gap junctions between cells in the renal vasculature or the renal tubule where it is abundant in basolateral cell interdigitations and infoldings of epithelial cells in the proximal tubule, thick ascending limb, distal convoluted tubule and collecting duct; however, physiological data regarding its role are limited. In this study, we investigated the role of Cx37 in fluid homeostasis using mice with a global deletion of Cx37 (Cx37-/- mice). Under baseline conditions, Cx37-/- had ~40% higher fluid intake associated with ~40% lower urine osmolality compared to wild-type (WT) mice. No differences were observed between genotypes in urinary adenosine triphosphate or prostaglandin E2, paracrine factors that alter renal water handling. After 18-hours of water deprivation, plasma aldosterone and urine osmolality increased significantly in Cx37-/- and WT mice; however, the latter remained ~375 mmol/kg lower in Cx37-/- mice, an effect associated with a more pronounced body weight loss despite higher urinary AVP/creatinine ratios compared to WT mice. Consistent with this, fluid intake in the first 3 hours after water deprivation was 37% greater in Cx37-/- vs WT mice. Cx37-/- mice showed significantly lower renal AQP2 abundance and AQP2 phosphorylation at serine 256 than WT mice in response to vehicle or dDAVP, suggesting a partial contribution of the kidney to the lower urine osmolality. The abundance and responses of the vasopressin V2 receptor, AQP3, NHE3, NKCC2, NCC, H+-ATPase, αENaC, γENaC or Na+/K+-ATPase were not significantly different between genotypes. In summary, these results demonstrate that Cx37 is important for body water handling.

Polymorphism of CONNEXIN37 gene is a risk factor for ischemic stroke in Han Chinese population

BACKGROUND

Stroke has a high fatality and disability rate, and is one of the main burdens to human health. It is thus very important to identify biomarkers for the development of effective approaches for the prevention and treatment of stroke. Connexin37 is an anti-inflammatory cytokine and is involved in chronic inflammation and atherosclerosis. Recent studies have found that CONNEXIN37 gene variations are associated with atherosclerosis diseases, such as coronary heart disease and stroke, but its association with stroke in distinct human populations remains to be determined. We report here the analysis of the association of the single nucleotide polymorphisms (SNPs) of CONNEXIN37 with ischemic stroke in Han Chinese population.

METHODS

Two SNPs of CONNEXIN37 gene were analyzed in 385 ischemic stroke patients and 362 hypertension control patients using ligase detection reaction (LDR) method.

RESULTS

Logistic regression analysis demonstrated that, AG and GG genotypes of SNP rs1764390 and CC genotype of rs1764391 of CONNEXIN37 were associated with an increased risk of ischemic stroke, and that G allele of rs1764390 is a risk factor for ischemic stroke. Further, we found that SNP rs1764390 and SNP rs1764391 in CONNEXIN37 were associated with ischemic stroke under additive/dominant model, and recessive/dominant model, respectively.

CONCLUSION

Our results indicate that CONNEXIN37 gene polymorphism is an ischemic stroke risk factor in Northern Han Chinese.

Smoking impairs and circulating stem cells favour the protective effect of the T allele of the connexin37 gene in ischemic heart disease--A multinational study

BACKGROUND

The connexin 37 (Cx37) gene is considered to be a candidate gene for ischemic heart disease (IHD). We analyzed the association between the C1019 > T (Pro319 > Ser) variant of the Cx37 gene and IHD in patients in the Czech Republic, Croatia, Hungary and Romania with regard to the presence/absence of selected cardiovascular risk factors (RF). In a complementary study, we analyzed the association between the Cx37 gene and circulating stem and endothelial progenitor cells in healthy women.

METHODS

The study population comprised 2396 patients (663 women) with IHD. The control population comprised 2476 subjects (1, 337 women). Additionally, in 662 healthy women, the association between the Cx37 gene and circulating stem and endothelial progenitor cells was analyzed.

RESULTS

The strongest protective effect of the Cx37 T allele was detected in non-smoking patients without diabetes mellitus and hypertension (OR 0.610, 95% CI 0.377-0.990); a similar effect was found in non-smoking men (OR 0.781, 95% CI 0.628-0.971); weaker effect was found in non-smoking women (OR 0.768, 95% CI 0.560-1.050). In non-smoking healthy women, stem cells were significantly higher in TT than in CT and CC carriers (p for trend 0.011). Additionally, non-smoking TT carriers had significantly higher number of stem cells than past and current smoking TT carriers (p for trend = 0.006); no such trend was found in CT and CC carriers.

CONCLUSIONS

The protective effect of the T allele of the Cx37 gene might be strongly modified by smoking; in women, this effect could be mediated through stem cells.

Association between C1019T polymorphism of the connexin37 gene and coronary heart disease in patients with in-stent restenosis

Studies have shown that a C1019T polymorphism of the gene encoding the gap junction protein connexin37 is associated with coronary artery disease (CAD). The aim of the present study was to explore the association between the C1019T polymorphism in the connexin37 gene and CAD patients with in-stent restenosis (ISR). A total of 532 patients who had undergone coronary stenting and coronary angiography at least three months after the procedure were divided according to a clinical diagnosis standard into two groups which were ISR (n=67) and no in-stent restenosis (NISR; n=465) groups. A further 501 healthy individuals were controls. The subjects were genotyped by DNA sequencing. The results demonstrated the following: i) connexin37 gene 1019 sites in the population were distributed by polymorphism into three genetic types (CC, TC and TT types). The distribution frequency of the healthy control, ISR and NISR groups conformed to the Hardy-Weinberg genetic balance rule; ii) in comparison with the healthy controls, the frequency of the connexin37 C allele was higher in the CAD patients (57.05% vs. 41.32%; OR, 1.89; 95% CI, 1.58–2.25; P<0.01). The frequency of the C carriers (CC+TC) was 65.47% in the healthy controls, vs. 79.32% in CAD patients (P<0.01). The CAD risk was significantly increased in the carriers of the C allele (CC+TC) compared with TT homozygotes (OR, 2.03; 95% CI, 1.53–2.80; P<0.01). Stratified analysis demonstrated that a significant difference existed in the frequency of C carriers between the male CAD patients and healthy controls (79.63% vs. 72.45%; OR, 1.48; 95% CI, 1.06–2.09, P=0.02), as well as in the female CAD patients (78.00% vs. 51.50%; OR, 3.34; 95% CI, 1.90–5.86; P<0.01). In the female and male CAD patients, the frequency of the connexin37 C allele was higher than in the healthy controls (male: χ²=12.67, P<0.01; female: χ²=50.20, P<0.01); iii) compared with the NISR group, the frequencies of the connexin37 C allele and C carriers (CC+TC) were significantly higher in the ISR group (frequency of C allele: 72.39% vs. 54.84%; P<0.01; frequency of C carriers: 89.55% vs. 77.85%; P=0.03). Compared with TT homozygotes, the restenosis risk was significantly increased in the carriers of the C allele (CC+TC; OR, 2.44; 95% CI, 1.08–5.50). Subsequent stratified analysis revealed that the frequency of the C allele was significantly higher in the male ISR group than in the male NISR group (78.57% vs. 52.66%; OR, 3.30; 95% CI, 2.05–5.29; P<0.01). The restenosis risk was ∼four-fold higher in the C carriers (CC+TC) than in the TT homozygotes (OR, 3.74; 95% CI, 1.32–10.64). However in the female population, there was no difference in the ISR risk between the carriers of the C allele (CC+TC) and the TT homozygotes (P=0.70). In summary, the C allele of the connexin37 gene is not only is associated with the susceptibility to CAD, but also associated with restenosis following coronary stenting in the population studied herein, particularly the male population.