Connexin 30.3 is expressed in the kidney but not regulated by dietary salt or high blood pressure

Several isoforms of connexin (Cx) proteins have been identified in a variety of tissues where they play a role in intercellular communication, either as the components of gap junctions or as large, nonselective pores known as hemichannels. This investigation seeks to identify the localization and regulation of Cx30.3 in mouse, rat, and rabbit kidney using a Cx30.3(+/lacZ) transgenic approach and immunofluorescence. Cx30.3 was detected in all three species and predominantly in the renal medulla. Both the nuclear lacZ staining indicative of Cx30.3 expression and indirect immunohistochemistry provided the same results. Cx30.3 immunolabeling was mainly punctate in the mouse, typical for gap junctions. In contrast, it showed continuous apical plasma membrane localization in certain tubule segments in the rat and rabbit kidney, suggesting that it may also function as hemichannels. In the cortex, Cx30.3 was localized in the intercalated cells of the cortical collecting duct, because the immunoreactive cells did not label for AQP2, a marker for principal cells. In the medulla, dense Cx30.3 staining was confined to the ascending thin limbs of the loop of Henle, because the immunoreactive cells did not label for AQP1, a marker of the descending thin limbs. Immunoblotting studies indicated that Cx30.3 expression was unchanged in response to either high or low salt intake or in spontaneously hypertensive rats. Cx30.3 appears to be constitutively expressed in certain renal tubular segments and cells and its role in overall kidney function remains to be investigated.     

Use of methotrexate therapy is not associated with decreased prevalence of metabolic syndrome

With great interest, we read the article by Toms and colleagues [1] in the previous issue of Arthritis Research & Therapy, in which they assessed prevalences of metabolic syndrome (MetS) in rheumatoid arthritis (RA) patients. Moreover, they identified demographic and clinical factors that may be associated with MetS. Toms and colleagues found prevalences of up to 45% of MetS and demonstrated older age and health status (health assessment questionnaire) to be associated with MetS irrespectively of the definition used. Of most interest, an association between methotrexate (MTX) use and decreased presence of MetS was observed in patients more than 60 years of age. The investigators hypothesized that this may be attributed to a drug-specific effect (and not to an anti-inflammatory effect) either by changing levels of adenosine, which is known to interact with glucose and lipid metabolism, or by an indirect effect mediated through concomitant folic acid administration, thereby decreasing homocysteine levels.Recently, we also examined the prevalence of MetS in (a subgroup of) RA patients in the CARRÉ investigation, a prospective cohort study on prevalent and incident cardiovascular disease and its underlying cardiovascular risk factors [2]. The findings of Toms and colleagues stimulated us to perform additional analyses in our total study population (n = 353).The prevalences of MetS were 35% and 25% (Table ​(Table1)1) according to criteria of National Cholesterol Education Program (NCEP) 2004 and NCEP 2001, respectively. In multivariate backward regression analyses, we found significant associations between body mass index, pulse rate, creatinine levels, hypothyroidism and diabetes mellitus and the presence of MetS independently of the criteria used (Table ​(Table2).2). However, an independent association between single use of MTX or use of MTX in combination with other disease-modifying antirheumatic drugs, on the one hand, and a decreased prevalence of MetS, on the other hand, could not be demonstrated (even in the subgroup of patients over the age of 60).

Table 1

Characteristics of the study population

Scrapie infectivity in hamster blood is not associated with platelets

The infectivity of hamster scrapie strain 263K was measured in platelets isolated from blood pooled from six hamsters with clinical scrapie. The total number of infectious doses present in the blood pool was 220, out of which only 3.5 infectious doses were associated with platelets. A larger proportion of the total infectivity was recovered from the mononuclear leukocyte fraction. This result indicates that platelets are not the source of blood-borne infectivity in transmissible spongiform encephalopathy-infected hamsters.     

The physiologic complexity of beat-to-beat blood pressure is associated with age-related alterations in blood pressure regulation

The fluctuations in resting-state beat-to-beat blood pressure (BP) are physiologically complex, and the degree of such BP complexity is believed to reflect the multiscale regulation of this critical physiologic process. Hypertension (HTN), one common age-related condition, is associated with altered BP regulation and diminished system responsiveness to perturbations such as orthostatic change. We thus aimed to characterize the impact of HTN on resting-state BP complexity, as well as the relationship between BP complexity and both adaptive capacity and underlying vascular characteristics. We recruited 392 participants (age: 60–91 years), including 144 that were normotensive and 248 with HTN (140 controlled- and 108 uncontrolled-HTN). Participants completed a 10-min continuous finger BP recording during supine rest, then underwent measures of lying-to-standing BP change, arterial stiffness (i.e., brachial-ankle pulse wave velocity), and endothelial function (i.e., flow-mediated vasodilation). The complexity of supine beat-to-beat systolic (SBP) and diastolic (DBP) BP was quantified using multiscale entropy. Thirty participants with HTN (16 controlled-HTN and 14 uncontrolled-HTN) exhibited orthostatic hypotension. SBP and DBP complexity was greatest in normotensive participants, lower in those with controlled-HTN, and lowest in those in uncontrolled-HTN (p < 0.0005). Lower SBP and DBP complexity correlated with greater lying-to-standing decrease in SBP and DBP level (β = −0.33 to −0.19, p < 0.01), greater arterial stiffness (β = −0.35 to −0.18, p < 0.01), and worse endothelial function (β = 0.17–0.22, p < 0.01), both across all participants and within the control- and uncontrolled-HTN groups. These results suggest that in older adults, BP complexity may capture the integrity of multiple interacting physiologic mechanisms that regulate BP and are important to cardiovascular health.     

Estradiol-induced attenuation of pulmonary hypertension is not associated with altered eNOS expression

Female rats develop less severe pulmonary hypertension (PH) in response to chronic hypoxia compared with males, thus implicating a potential role for ovarian hormones in mediating this gender difference. Considering that estrogen upregulates endothelial nitric oxide (NO) synthase (eNOS) in systemic vascular tissue, we hypothesized that estrogen inhibits hypoxic PH by increasing eNOS expression and activity. To test this hypothesis, we examined responses to the endothelium-derived NO-dependent dilator ionomycin and the NO donors S-nitroso-N-acetylpenicillamine and spermine NONOate in U-46619-constricted, isolated, saline-perfused lungs from the following groups: 1) normoxic rats with intact ovaries, 2) chronic hypoxic (CH) rats with intact ovaries, 3) CH ovariectomized rats given 17 beta-estradiol (E(2)beta), and 4) CH ovariectomized rats given vehicle. Additional experiments assessed pulmonary eNOS levels in each group by Western blotting. Our findings indicate that E(2)beta attenuated chronic hypoxia-induced right ventricular hypertrophy, pulmonary arterial remodeling, and polycythemia. Furthermore, although CH augmented vasodilatory responsiveness to ionomycin and increased pulmonary eNOS expression, these responses were not potentiated by E(2)beta. Finally, responses to S-nitroso-N-acetylpenicillamine and spermine NONOate were similarly attenuated in all CH groups compared with normoxic control groups. We conclude that the inhibitory influence of E(2)beta on chronic hypoxia-induced PH is not associated with increased eNOS expression or activity.     

Menopausal hormone therapy is associated with having high blood pressure in postmenopausal women: observational cohort study

Background

The relationship between menopausal hormone therapy (MHT) and cardiovascular risk remains controversial, with a number of studies advocating the use of MHT in reducing risk of cardiovascular diseases, while others have shown it to increase risk. The aim of this study was to determine the association between menopausal hormone therapy and high blood pressure.

Methods and Findings

A total of 43,405 postmenopausal women were included in the study. Baseline data for these women were sourced from the 45 and Up Study, Australia, a large scale study of healthy ageing. These women reported being postmenopausal, having an intact uterus, and had not been diagnosed with high blood pressure prior to menopause. Odds ratios for the association between MHT use and having high blood pressure were estimated using logistic regression, stratified by age (<56 years, 56–61 years, 62–70 years and over 71 years) and adjusted for demographic and lifestyle factors. MHT use was associated with higher odds of having high blood pressure: past menopausal hormone therapy use: <56 years (adjusted odds ratio 1.59, 99% confidence interval 1.15 to 2.20); 56–61 years (1.58, 1.31 to 1.90); 62–70 years (1.26, 1.10 to 1.44). Increased duration of hormone use was associated with higher odds of having high blood pressure, with the effect of hormone therapy use diminishing with increasing age.

Conclusions

Menopausal hormone therapy use is associated with significantly higher odds of having high blood pressure, and the odds increase with increased duration of use. High blood pressure should be conveyed as a health risk for people considering MHT use.     

Elevated peak exercise systolic blood pressure is not associated with reduced exercise capacity in subjects with Type 2 diabetes.

Subjects with Type 2 diabetes without cardiovascular disease have a reduced exercise capacity compared with nondiabetic subjects. However, the mechanisms responsible for this phenomenon are unknown. The purpose of this study was to evaluate the impact of exercise systolic blood pressure (SBP) response on diverse exercise tolerance parameters in Type 2 diabetic subjects. Twenty-eight sedentary men with Type 2 diabetes were recruited for this study. Subjects were treated with oral hypoglycemic agents and/or diet. Evaluation of glycemic control and peak exercise capacity were performed for each subject. The subjects were divided into two groups according to the median value of peak SBP (210 mmHg) measured in each subject. We observed a 13, 13, and 16% reduction in the relative peak oxygen uptake (V(O2 peak)), absolute V(O2 peak), and peak work rate in the low- compared with the high-peak SBP group [26.95 (SD 5.35) vs. 30.96 (SD 3.61) ml.kg(-1).min(-1), 2.5 (SD 0.4) vs. 2.8 (SD 0.6) l/min, and 169 (SD 34) vs. 202 (SD 32) W; all P < 0.05]. After adjusting for age, relative V(O2 peak) was still significantly different (P < 0.05). There were similar peak respiratory exchange ratio (RER) [1.20 (SD 0.08) vs. 1.16 (SD 0.07); P = 0.24] and peak heart rate [160 (SD 20) vs. 169 (SD 15) beats/min; P = 0.18] between the low- compared with the high-SBP group. No difference in glycemic control was observed between the two groups. The results reported in this study suggest that in subjects with Type 2 diabetes without cardiovascular disease, an elevated exercise SBP is not associated with reduced exercise capacity and its modulation is probably not related to glycemic control.     

Genome-wide association study of blood pressure extremes identifies variant near UMOD associated with hypertension

Hypertension is a heritable and major contributor to the global burden of disease. The sum of rare and common genetic variants robustly identified so far explain only 1%–2% of the population variation in BP and hypertension. This suggests the existence of more undiscovered common variants. We conducted a genome-wide association study in 1,621 hypertensive cases and 1,699 controls and follow-up validation analyses in 19,845 cases and 16,541 controls using an extreme case-control design. We identified a locus on chromosome 16 in the 5′ region of Uromodulin (UMOD; rs13333226, combined P value of 3.6×10⁻¹¹). The minor G allele is associated with a lower risk of hypertension (OR [95%CI]: 0.87 [0.84–0.91]), reduced urinary uromodulin excretion, better renal function; and each copy of the G allele is associated with a 7.7% reduction in risk of CVD events after adjusting for age, sex, BMI, and smoking status (H.R. = 0.923, 95% CI 0.860–0.991; p = 0.027). In a subset of 13,446 individuals with estimated glomerular filtration rate (eGFR) measurements, we show that rs13333226 is independently associated with hypertension (unadjusted for eGFR: 0.89 [0.83–0.96], p = 0.004; after eGFR adjustment: 0.89 [0.83–0.96], p = 0.003). In clinical functional studies, we also consistently show the minor G allele is associated with lower urinary uromodulin excretion. The exclusive expression of uromodulin in the thick portion of the ascending limb of Henle suggests a putative role of this variant in hypertension through an effect on sodium homeostasis. The newly discovered UMOD locus for hypertension has the potential to give new insights into the role of uromodulin in BP regulation and to identify novel drugable targets for reducing cardiovascular risk.     

Predatory aggression, but not maternal or intermale aggression, is associated with high voluntary wheel-running behavior in mice

Predatory (towards crickets), intermale, and maternal aggression were examined in four replicate lines of mice that had been selectively bred for high wheel-running (S) and in four random-bred control lines (C). In generation 18, individual differences in both predatory and intermale aggression were significantly consistent across four trial days, but predatory and intermale aggression were uncorrelated both at the individual level and among the eight line means. Latencies to attack crickets were significantly lower in S lines as a group. Intermale aggression, however, did not differ between S and C lines. S lines were significantly smaller in body mass, but did not differ in either testes mass or plasma testosterone. In generations 28 and 30, respectively, S and C lines did not differ in either maternal or intermale aggression. However, significant differences among the individual lines were found for maternal aggression, and one S line exhibited an extremely high mean time of aggression (>120 sec for a 5-min test). Maternal and intermale aggression were not correlated among the eight line means or at the level of individual variation. Overall, our results suggest: (1) predatory aggression and voluntary wheel-running are positively related at the genetic level; (2) predatory and intermale aggression are unrelated at a genetic level; and (3) maternal and intermale aggression are not tightly related at the genetic level. Possible relationships between predatory aggression, dopamine, and wheel-running behavior are discussed.     

Shift work disorder in nurses--assessment, prevalence and related health problems

Background

This study investigates the prevalence of symptoms of shift work disorder in a sample of nurses, and its association to individual, health and work variables.

Methodology/Principal Findings

We investigated three different shift work disorder assessment procedures all based on current diagnostic criteria and employing symptom based questions. Crude and adjusted logistic regression analyses were performed with symptoms of shift work disorder as the dependent variable. Participants (n = 1968) reported age, gender, work schedule, commuting time, weekly work hours, children in household, number of nights and number of shifts separated by less than 11 hours worked the last year, use of bright light therapy, melatonin and sleep medication, and completed the Bergen Insomnia Scale, Epworth Sleepiness Scale, Global Sleep Assessment Questionnaire, Diurnal Scale, Revised Circadian Type Inventory, Dispositional Resilience (Hardiness) Scale – Revised, Fatigue Questionnaire, questions about alcohol and caffeine consumption, as well as the Hospital Anxiety and Depression Scale.

Conclusions/Significance

Prevalence rates of symptoms of shift work disorder varied from 32.4–37.6% depending on the assessment method and from 4.8–44.3% depending on the work schedule. Associations were found between symptoms of shift work disorder and age, gender, circadian type, night work, number of shifts separated by less than 11 hours and number of nights worked the last year, insomnia and anxiety. The different assessment procedures yielded similar results (prevalence and logistic regression analyses). The prevalence of symptoms indicative of shift work disorder was high. We argue that three symptom-based questions used in the present study adequately assess shift work disorder in epidemiological studies.     

The elevated blood pressure of human GRK4gamma A142V transgenic mice is not associated with increased ROS production

G protein-coupled receptor (GPCR) kinases (GRKs) regulate the sensitivity of GPCRs, including dopamine receptors. The GRK4 locus is linked to, and some of its polymorphisms are associated with, human essential hypertension. Transgenic mice overexpressing human (h) GRK4gamma A142V on a mixed genetic background (C57BL/6J and SJL/J) have impaired renal D(1)-dopamine receptor (D(1)R) function and increased blood pressure. We now report that hGRK4gamma A142V transgenic mice, in C57BL/6J background, are hypertensive and have higher blood pressures than hGRK4gamma wild-type transgenic and nontransgenic mice. The hypertensive phenotype is stable because blood pressures in transgenic founders and F6 offspring are similarly increased. To determine whether the hypertension is associated with increased production of reactive oxygen species (ROS), we measured renal NADPH oxidase (Nox2 and Nox4) and heme oxygenase (HO-1 and HO-2) protein expressions and urinary excretion of 8-isoprostane and compared the effect of Tempol on blood pressure in hGRK4gamma A142V transgenic mice and D(5)R knockout (D(5)(-/-)) mice in which hypertension is mediated by increased ROS. The expressions of Nox isoforms and HO-2 and the urinary excretion of 8-isoprostane were similar in hGRK4gamma A142V transgenic mice and their controls. HO-1 expression was increased in hGRK4gamma A142V relative to hGRK4gamma wild-type transgenic mice. In contrast with the hypotensive effect of Tempol in D(5)(-/-) mice, it had no effect in hGRK4gamma A142V transgenic mice. We conclude that the elevated blood pressure of hGRK4gamma A142V transgenic mice is due mainly to the effect of hGRK4gamma A142V transgene acting via D(1)R and increased ROS production is not a contributor.     

A polymorphism in the promoter region of catalase is associated with blood pressure levels

Catalase is an important antioxidant enzyme that detoxifies H2O2 into oxygen and water and thus limits the deleterious effects of reactive oxygen species (ROS). Because chronic exposure to excess ROS may contribute to vascular damage, we investigated whether genetic variation in catalase was associated with susceptibility to essential hypertension (EHYT) in 324 individuals (at least 50 years old) who were randomly sampled from an isolated population living in Xiangchang, China. They were screened for genetic variation in the promoter of catalase by direct sequencing. In total, four single nucleotide polymorphisms (SNPs) were identified. The association between the SNPs and EHYT was investigated by a linear regression model under phenotypic selection; in our analyses, we used both SBP>150 mmHg and SBP>160 mmHg as thresholds. A SNP 844 bp upstream of the start codon (SNP-844) demonstrated strong evidence of association with EHYT (SBP>150 mmHg: F=5.09, P=0.008; SBP>160 mmHg: F=7.13, P=0.002). This is the first study to implicate genetic variation in catalase in susceptibility to EHYT and suggests that polymorphisms in promoter regions may be particularly relevant to the study of complex diseases.     

Telomere length in white blood cells is not associated with morbidity or mortality in the oldest old: a population-based study

Cross-sectional studies have repeatedly suggested peripheral blood monocyte telomere length as a biomarker of aging. To test this suggestion in a large population-based follow-up study of the oldest old, we measured telomere length at baseline in 598 participants of the Leiden 85-plus Study (mean age at baseline 89.8 years). We also obtained second telomere measurements from 81 participants after an average time span of between 3.9 and 12.9 years. Telomere length at baseline was not predictive for mortality (P > 0.40 for all-cause, cardiovascular causes, cancer or infectious diseases, Cox regression for gender-adjusted tertiles of telomere length) or for the incidence of dementia (P = 0.78). Longitudinally, telomere length was highly unstable in a large fraction of participants. We conclude that blood monocyte telomere length is not a predictive indicator for age-related morbidity and mortality at ages over 85 years, possibly because of a high degree of telomere length instability in this group.     

Intracranial aneurysm risk locus 5q23.2 is associated with elevated systolic blood pressure

Although genome-wide association studies (GWAS) have identified hundreds of complex trait loci, the pathomechanisms of most remain elusive. Studying the genetics of risk factors predisposing to disease is an attractive approach to identify targets for functional studies. Intracranial aneurysms (IA) are rupture-prone pouches at cerebral artery branching sites. IA is a complex disease for which GWAS have identified five loci with strong association and a further 14 loci with suggestive association. To decipher potential underlying disease mechanisms, we tested whether there are IA loci that convey their effect through elevating blood pressure (BP), a strong risk factor of IA. We performed a meta-analysis of four population-based Finnish cohorts (n(FIN) = 11 266) not selected for IA, to assess the association of previously identified IA candidate loci (n = 19) with BP. We defined systolic BP (SBP), diastolic BP, mean arterial pressure, and pulse pressure as quantitative outcome variables. The most significant result was further tested for association in the ICBP-GWAS cohort of 200 000 individuals. We found that the suggestive IA locus at 5q23.2 in PRDM6 was significantly associated with SBP in individuals of European descent (p(FIN) = 3.01E-05, p(ICBP-GWAS) = 0.0007, p(ALL) = 8.13E-07). The risk allele of IA was associated with higher SBP. PRDM6 encodes a protein predominantly expressed in vascular smooth muscle cells. Our study connects a complex disease (IA) locus with a common risk factor for the disease (SBP). We hypothesize that common variants in PRDM6 can contribute to altered vascular wall structure, hence increasing SBP and predisposing to IA. True positive associations often fail to reach genome-wide significance in GWAS. Our findings show that analysis of traditional risk factors as intermediate phenotypes is an effective tool for deciphering hidden heritability. Further, we demonstrate that common disease loci identified in a population isolate may bear wider significance.