Human heart rate: heritability of resting and stress values in twin pairs, and influence of genetic variation in the adrenergic pathway at a microribonucleic acid (microrna) motif in the 3'-UTR of cytochrome b561 [corrected]

Congenital absence of norepinephrine due to CYB561 mutations

OBJECTIVE

Cytochrome b561 (CYB561) generates ascorbic acid, a cofactor in the enzymatic conversion of dopamine to norepinephrine by dopamine β-hydroxylase. We propose that the clinical relevance of this pathway can be revealed by characterizing the autonomic and biochemical characteristics of patients with CYB561 mutations.

METHODS

We performed autonomic evaluations in 4 patients with lifelong orthostatic hypotension in whom CYB561 mutations were determined by genomic sequencing.

RESULTS

Patients had disabling lifelong orthostatic hypotension (OH) and impaired blood pressure response to the Valsalva maneuver (VM), with exaggerated hypotension during phase 2 and lack of overshoot during phase 4. Heart rate ratios for sinus arrhythmia and the VM were normal. Plasma norepinephrine and metabolites were undetectable, and plasma dopamine and metabolites were normal. Droxidopa restored norepinephrine levels and improved OH. Patients 1 and 2 were sisters and homozygous for a nonsense mutation in exon 2, c.131G>A, p.Trp44 (Circ Res 2018). Their brother (patient 3) died at age 16 and his DNA was not available. Patient 4 was compound heterozygous; one allele had a missense mutation in exon 2, c157C>T, p.His.53Tyr, and the other had an exon 2 deletion.

CONCLUSION

CYB561 deficiency is characterized by selective sympathetic noradrenergic failure with lifelong, disabling OH but with normal sympathetic cholinergic (sweating) and parasympathetic (heart rate regulation) functions. We report a novel case of CYB561 deficiency due to an exon 2 deletion in one allele and a missense mutation in the other. These patients highlight the critical role CYB561 plays in sympathetic function and cardiovascular regulation.

Heritability and genetic correlations of heart rate variability at rest and during stress in the Oman Family Study

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Introduction:

Individual differences in heart rate variability (HRV) can be partly attributed to genetic factors that may be more pronounced during stress. Using data from the Oman Family Study (OFS), we aimed to estimate and quantify the relative contribution of genes and environment to the variance of HRV at rest and during stress; calculate the overlap in genetic and environmental influences on HRV at rest and under stress using bivariate analyses of HRV parameters and heart rate (HR).

Methods:

Time and frequency domain HRV variables and average HR were measured from beat-to-beat HR obtained from electrocardiogram recordings at rest and during two stress tests [mental: Word Conflict Test (WCT) and physical: Cold Pressor Test (CPT)] in the OFS – a multigenerational pedigree consisting of five large Arab families with a total of 1326 participants. SOLAR software was used to perform quantitative genetic modelling.

Results:

Heritability estimates for HRV and HR ranged from 0.11 to 0.31 for rest, 0.09–0.43 for WCT, and 0.07–0.36 for CPT. A large part of the genetic influences during rest and stress conditions were shared with genetic correlations ranging between 0.52 and 0.86 for rest-WCT and 0.60–0.92 for rest-CPT. Nonetheless, genetic rest–stress correlations for most traits were significantly smaller than 1 indicating some stress-specific genetic effects.

Conclusion:

Genetic factors significantly influence HRV and HR at rest and under stress. Most of the genetic factors that influence HRV at rest also influence HRV during stress tests, although some unique genetic variance emerges during these challenging conditions.

Genomics of Cardiovascular Measures of Autonomic Tone

The autonomic nervous system exerts broad control over the involuntary functions of the human body through complex equilibrium between sympathetic and parasympathetic tone. Imbalance in this equilibrium is associated with a multitude of cardiovascular outcomes, including mortality. The cardiovascular static state of this equilibrium can be quantified using physiological parameters such as heart rate (HR), blood pressure, and by spectral analysis of HR variability. Here, we review the current state of knowledge of the genetic background of cardiovascular measurements of autonomic tone. For most parameters of autonomic tone, a large portion of variability is explained by genetic heritability. Many of the static parameters of autonomic tone have also been studied through candidate-gene approach, yielding some insight into how genotypes of adrenergic receptors affect variables such as HR. Genome-wide approaches in large cohorts similarly exist for static variables such as HR and blood pressure but less is known about the genetic background of the dynamic and more specific measurements, such as HR variability. Furthermore, because most autonomic measures are likely polygenic, pathway analyses and modeling of polygenic effects are critical. Future work will hopefully explain the control of autonomic tone and guide individualized therapeutic interventions.

MiR-1294 confers cisplatin resistance in ovarian Cancer cells by targeting IGF1R

BACKGROUND

Dysregulation of miRNAs is critical for chemosensitivity to platinum-based agents in ovarian cancer (OC) which is the most aggressive gynecological cancer. However, the underlying mechanisms of miRNA-regulated platinum resistance in ovarian cancer remain unclear. In this study, we intended to investigate the effect of miR-1294 on platinum-resistant OC.

METHODS

The expression of miR-1294 in OC tissues (n = 30) and cell lines was measured by qRT-PCR. Cell transfection was carried out to establish miR-1294 overexpression or knockdown. MTT and clone formation assays were performed to examine proliferation in OC cells. Additionally, wound healing and tumor invasion assays were used to investigate cell migration and invasion, respectively. Finally, the expression of epithelial-to-mesenchymal transition (EMT)-associated proteins was measured in OC cells by western blot.

RESULTS

Our results showed that miR-1294 dysregulation manipulated OC cisplatin resistance through regulating IGF1R. Knockdown of IGF1R decreased SKOVP/DDP cell proliferation, migration, invasion and EMT. Moreover, overexpression of miR-1294 prevented OC cisplatin resistance.

CONCLUSION

Our results indicated that epigenetic regulation of IGF1R via miR-1294 was essential for cisplatin resistance in OC and provide a new avenue for OC treatment.

Interpreting the various associations of MiRNA polymorphisms with susceptibilities of cardiovascular diseases: Current evidence based on a systematic review and meta-analysis

BACKGROUND

To interpret the various associations between miRNA polymorphisms and cardiovascular diseases (CVD).

METHODS

Literature search has identified relevant studies up to June 2016. A meta-analysis was performed followed the guidelines from the Cochrane review group and the PRISMA statement. Studies were identified by searching the Cochrane Library, EMBASE, PUBMED and WHO clinical trials registry center. A meta-analysis has been done with a fixed/random-effect model using STATA 14.0, which also has been used to estimate the publication bias and meta-regression.

RESULTS

The results from 11 case-control studies were included. The miR-146a G/C makes a contribution to the causing of CVD as recessive genetic model. And the miR-499 G/A raised the risks of cardiomyopathy, however it could still accelerate the procedure of CVD combined with myocardial infraction. At this point, we consider that it could deepen the adverse of outcomes from coronary artery disease (CAD), but it's hard to draw an association between miR-499 G/A and CAD. At last the miR-196a2 T/C demonstrated a contrary role between development problem and metabolic issues, which protects the development procedure and impairs the metabolism to cause different disease phenotypes.

CONCLUSION

Despite inter-study variability, the polymorphisms from miR-146a, miR-499 and miR-196a2 have impacts on cardiovascular disease. Each type of miRNA has individual role in either cardiac development or the origins of CVD.

Mutations in CYB561 Causing a Novel Orthostatic Hypotension Syndrome

RATIONALE

Orthostatic hypotension is a common clinical problem, but the underlying mechanisms have not been fully delineated.

OBJECTIVE

We describe 2 families, with 4 patients in total, experiencing severe life-threatening orthostatic hypotension because of a novel cause.

METHODS AND RESULTS

As in dopamine β-hydroxylase deficiency, concentrations of norepinephrine and epinephrine in the patients were low. Plasma dopamine β-hydroxylase activity, however, was normal, and the DBH gene had no mutations. Molecular genetic analysis was performed to determine the underlying genetic cause. Homozygosity mapping and exome and Sanger sequencing revealed pathogenic homozygous mutations in the gene encoding cytochrome b561 (CYB561); a missense variant c.262G>A, p.Gly88Arg in exon 3 in the Dutch family and a nonsense mutation (c.131G>A, p.Trp44*) in exon 2 in the American family. Expression of CYB561 was investigated using RNA from different human adult and fetal tissues, transcription of RNA into cDNA, and real-time quantitative polymerase chain reaction. The CYB561 gene was found to be expressed in many human tissues, in particular the brain. The CYB561 protein defect leads to a shortage of ascorbate inside the catecholamine secretory vesicles leading to a functional dopamine β-hydroxylase deficiency. The concentration of the catecholamines and downstream metabolites was measured in brain and adrenal tissue of 6 CYB561 knockout mice (reporter-tagged deletion allele [post-Cre], genetic background C57BL/6NTac). The concentration of norepinephrine and normetanephrine was decreased in whole-brain homogenates of the CYB561^(-/-) mice compared with wild-type mice (P<0.01), and the concentration of normetanephrine and metanephrine was decreased in adrenal glands (P<0.01), recapitulating the clinical phenotype. The patients responded favorably to treatment with l-dihydroxyphenylserine, which can be converted directly to norepinephrine.

CONCLUSIONS

This study is the first to implicate cytochrome b561 in disease by showing that pathogenic mutations in CYB561 cause an as yet unknown disease in neurotransmitter metabolism causing orthostatic hypotension.

Heritability of heart rate recovery and vagal rebound after exercise

Purpose

The prognostic power of heart rate recovery (HRR) after exercise has been well established but the exact origin of individual differences in HRR remains unclear. This study aims to estimate the heritability of HRR and vagal rebound after maximal exercise in adolescents. Furthermore, the role of voluntary regular exercise behavior (EB) in HRR and vagal rebound is tested.

Methods

491 healthy adolescent twins and their siblings were recruited for maximal exercise testing, followed by a standardized cooldown with measurement of the electrocardiogram and respiratory frequency. Immediate and long-term HRR (HRR60 and HRR180) and vagal rebound (heart rate variability in the respiratory frequency range) were assessed 1 and 3 min after exercise. Multivariate twin modeling was used to estimate heritability of all measured variables and to compute the genetic contribution to their covariance.

Results

Heritability of HRR60, HRR180 and immediate and long-term vagal rebound is 60 % (95 % CI: 48–67), 65 % (95 % CI: 54–73), 23 % (95 % CI: 11–35) and 3 % (95 % CI: 0–11), respectively. We find evidence for two separate genetic factors with one factor influencing overall cardiac vagal control, including resting heart rate and respiratory sinus arrhythmia, and a specific factor for cardiac vagal exercise recovery. EB was only modestly associated with resting heart rate (r = −0.27) and HRR (rHRR60 = 0.10; rHRR180 = 0.19) with very high genetic contribution to these associations (88–91 %).

Conclusions

Individual differences in HRR and immediate vagal rebound can to a large extent be explained by genetic factors. These innate cardiac vagal exercise recovery factors partly reflect the effects of heritable differences in EB.

miRNA-216 and miRNA-499 target cyb561d2 in zebrafish in response to fipronil exposure

MicroRNA (miRNA) can regulate the expression of its target gene by mediating mRNA cleavage or by translational repression at a post-transcriptional level. Usually, one miRNA may regulate many genes as its targets, while one gene may also be targeted by many miRNAs. We previously demonstrated that cyb561d2, whose protein product is involved in cell defense, and chemical stress, is targeted by miR-155 in adult zebrafish (Danio rerio) when exposed to fipronil (5-amino-1-[2,6-dichloro-4-(trifluoromethyl) phenyl]-4-[(trifluoromethyl) sulphinyl]-1H-pyrazole-3-carbonitrile). Microcosm Targets prediction showed that the cyb561d2 gene is also highly possibly targeted by miR-194a, miR-216b, miR-429, and miR-499. These interactions need to be further validated experimentally. In this study, we evaluated the effects of fipronil on miR-194a, miR-216b, miR-429, miR-499 and cyb561d2 in zebrafish and investigated whether these four miRNAs could regulate the expression of cyb561d2 in both mRNA and protein levels. The expression of cyb561d2 was upregulated in both mRNA and protein level in a dose-dependent manner upon stimulation of fipronil, and miR-216b and miR-499 were downregulated concurrently, whereas there was no significant changes were observed in the expression level of miR-194a and miR-429. The dual luciferase report assay demonstrated that miR-216b and miR-499 interacted with cyb561d2 3'-untranslated regions (3'-UTR), miR-194a and miR-429 did not stimulate degradation of cyb561d2 mRNA. The expression of cyb561d2 was reduced in both mRNA and protein level when ZF4 cells were transfected with miR-499 mimic, whereas expression level of both mRNA and protein was increased when endogenous miR-499 was inhibited by transfection with miR-499 inhibitor. Likewise, the mRNA and protein level of cyb561d2 was affected by treatment with the mimics and the inhibitor of miR-216b. In contrast, when ZF4 cells were transfected with a mimic of miR-194a or miR-429, the expression of cyb561d2 mRNA was not significantly changed. As a result, cyb561d2 is targeted by miR-155, miR-216b and miR-499 upon fipronil exposure, and miR-194a and miR-429 can not target cyb561d2. The expression pattern of these 3 miRNAs presents novel fipronil responses that could be used as a toxicological biomarker.