Maternal obesity, interpregnancy weight changes and congenital heart defects in the offspring: a nationwide cohort study.

OBJECTIVE: To evaluate the association between maternal BMI and congenital heart defects (CHDs) in the offspring when including live births, stillbirths, aborted and terminated pregnancies and to investigate if maternal interpregnancy weight changes between the first and second pregnancy influences the risk of foetal CHDs. METHODS: A nationwide cohort study of all singleton pregnancies in Denmark from 2008 to 2018. Data were retrieved from the Danish Foetal Medicine Database, which included both pre- and postnatal diagnoses of CHDs. Children or foetuses with chromosomal aberrations were excluded. Odds ratios were calculated with logistic regression models for CHDs overall, severe CHDs and five of the most prevalent subtypes of CHDs. RESULTS: Of the 547 105 pregnancies included in the cohort, 5 442 had CHDs (1.0%). Risk of CHDs became gradually higher with higher maternal BMI; for BMI 25-29.9 kg/m2, adjusted odds ratio (aOR) 1.17 (95% CI 1.10-1.26), for BMI 30-34.9 kg/m2, aOR 1.21 (95% CI 1.09-1.33), for BMI 35-39.9 kg/m2, aOR 1.29 (95% CI 1.11-1.50) and for BMI ≥ 40 kg/m2, aOR 1.85 (95% CI 1.54-2.21). Data was adjusted for maternal age, smoking status and year of estimated due date. The same pattern was seen for the subgroup of severe CHDs. Among the atrioventricular septal defects (n = 231), an association with maternal BMI ≥ 30 kg/m2 was seen, OR 1.67 (95% CI 1.13-2.44). 109 654 women were identified with their first and second pregnancies in the cohort. Interpregnancy BMI change was associated with the risk of CHDs in the second pregnancy (BMI 2 to < 4 kg/m2: aOR 1.29, 95% CI 1.09-1.53; BMI ≥ 4 kg/m2: aOR 1.36, 95% CI 1.08-1.68). CONCLUSION: The risk of foetal CHDs became gradually higher with higher maternal BMI and interpregnancy weight increases above 2 BMI units were also associated with a higher risk of CHDs.

Trends in congenital clubfoot prevalence and co-occurring anomalies during 1994-2021 in Denmark: a nationwide register-based study.

BACKGROUND: Congenital talipes equinovarus (clubfoot) is a common musculoskeletal anomaly, with a suspected multifactorial etiopathogenesis. Herein, we used publicly available data to ascertain liveborn infants with clubfoot delivered in Denmark during 1994-2021, and to classify co-occurring congenital anomalies, estimate annual prevalence, and compare clubfoot occurrence with maternal smoking rates, a commonly reported risk factor. Characterizing this nationwide, liveborn cohort provides a population-based resource for etiopathogenic investigations and life course surveillance. METHODS: This case-cohort study used data from the Danish National Patient Register and Danish Civil Registration System, accessed through the publicly available Danish Biobank Register, to identify 1,315,282 liveborn infants delivered during 1994-2021 in Denmark to Danish parents. Among these, 2,358 infants (65.1% male) were ascertained with clubfoot and classified as syndromic (co-occurring chromosomal, genetic, or teratogenic syndromes) and nonsyndromic (isolated or co-occurring multiple congenital anomalies [MCA]). Annual prevalence estimates and corresponding 95% confidence intervals (CIs) for children with nonsyndromic clubfoot were estimated using Poisson regression and compared with population-based, maternal annual smoking rates obtained from publicly available resources. RESULTS: Infants most often presented with nonsyndromic clubfoot (isolated = 88.6%; MCA = 11.4%); limb and heart anomalies were the most frequently identified MCAs. Prevalence (per 1,000 liveborn infants) was 1.52 (CI 1.45-1.58) for isolated and 0.19 (CI 0.17-0.22) for MCA clubfoot. Prevalence estimates for both isolated and MCA clubfoot remained relatively stable during the study period, despite marked decreases in population-based maternal smoking rates. CONCLUSIONS: From 1994 to 2021, prevalence of nonsyndromic clubfoot in Denmark was relatively stable. Reduction in population-level maternal smoking rates did not seem to impact prevalence estimates, providing some support for the suspected multifactorial etiopathogenesis of this anomaly. This nationwide, liveborn cohort, ascertained and clinically characterized using publicly available data from the Danish Biobank Register, provides a population-based clinical and biological resource for future etiopathogenic investigations and life course surveillance.

A Nationwide Observational Study of Chlamydia trachomatis Infections in Denmark during the COVID-19 Pandemic.

The aim of this study was to determine whether COVID-19 restrictions had an impact on Chlamydia trachomatis infections compared with 2018 and 2019. A retrospective nationwide observational study was performed using monthly incidences of laboratory-confirmed chlamydia cases and number of tests, obtained from Danish national surveillance data. Testing rates and positivity rates were compared using Poisson and logistic regression. The first Danish COVID-19 lockdown (12 March to 14 April 2020) resulted in a reduction in the number of chlamydia tests performed (rate ratio 0.72, 95% confidence interval  0.71-0.73) and a consequent reduction in the number of laboratory-identified cases (66.5 vs 88.3 per 100,000 population during the same period in 2018 to 2019). This period was followed by a return of testing and test positivity close to the level seen in 2018 to 2019. The second Danish COVID-19 lockdown (17 December to 31 March 2021) resulted in crude incidence rates of laboratory-confirmed chlamydia infection that were similar to the crude incidence rates seen during same period in 2018 to 2019. In conclusion, the Danish COVID-19 restrictions have had negligible effects on laboratory-confirmed C. trachomatis transmission.

Preterm birth, stillbirth and early neonatal mortality during the Danish COVID-19 lockdown.

Using provisional or opportunistic data, three nationwide studies (The Netherlands, the USA and Denmark) have identified a reduction in preterm or extremely preterm births during periods of COVID-19 restrictions. However, none of the studies accounted for perinatal deaths. To determine whether the reduction in extremely preterm births, observed in Denmark during the COVID-19 lockdown, could be the result of an increase in perinatal deaths and to assess the impact of extended COVID-19 restrictions, we performed a nationwide Danish register-based prevalence proportion study. We examined all singleton pregnancies delivered in Denmark during the COVID-19 strict lockdown calendar periods (March 12-April 14, 2015-2020, N = 31,164 births) and the extended calendar periods of COVID-19 restrictions (February 27-September 30, 2015-2020, N = 214,862 births). The extremely preterm birth rate was reduced (OR 0.27, 95% CI 0.07 to 0.86) during the strict lockdown period in 2020, while perinatal mortality was not significantly different. During the extended period of restrictions in 2020, the extremely preterm birth rate was marginally reduced, and a significant reduction in the stillbirth rate (OR 0.69, 0.50 to 0.95) was observed. No changes in early neonatal mortality rates were found.Conclusion: Stillbirth and extremely preterm birth rates were reduced in Denmark during the period of COVID-19 restrictions and lockdown, respectively, suggesting that aspects of these containment and control measures confer an element of protection. The present observational study does not allow for causal inference; however, the results support the design of studies to ascertain whether behavioural or social changes for pregnant women may improve pregnancy outcomes. What is Known: • The aetiologies of preterm birth and stillbirth are multifaceted and linked to a wide range of socio-demographic, medical, obstetric, foetal, psychosocial and environmental factors. • The COVID-19 lockdown saw a reduction in extremely preterm births in Denmark and other high-income countries. An urgent question is whether this reduction can be explained by increased perinatal mortality. What is New: • The reduction in extremely preterm births during the Danish COVID-19 lockdown was not a consequence of increased perinatal mortality, which remained unchanged during this period. • The stillbirth rate was reduced throughout the extended period of COVID-19 restrictions.

The Role of Leptin in Fetal Growth during Pre-Eclampsia.

Leptin is secreted by the placenta and has a multi-facetted role in the regulation of functions related to pregnancy. Metabolic disorders and insufficient homeostatic compensatory mechanisms involving leptin during pregnancy play a decisive role in the development of pre-eclampsia (PE) and give rise to compromised intrauterine growth conditions and aberrant birth weight of offspring. This review was compiled to elucidate the metabolic background of PE and its relationship with adverse intrauterine growth conditions through the examination of leptin as well as to describe possible mechanisms linking leptin to fetal growth restriction. This review illustrates that leptin in PE is dysregulated in maternal, fetal, and placental compartments. There is no single set of unifying mechanisms within the spectrum of PE, and regulatory mechanisms involving leptin are specific to each situation. We conclude that dysregulated leptin is involved in fetal growth at many levels through complex interactions with parallel pregnancy systems and probably throughout the entirety of pregnancy.

Leptin, adiponectin, and their ratio as markers of insulin resistance and cardiometabolic risk in childhood obesity.

BACKGROUND: It is imperative to develop markers for risk stratification and detection of cardiometabolic comorbidities in children with obesity. The adipokines leptin and adiponectin are both involved in fat mass regulation and the development of obesity-related disorders; furthermore, their ratio (leptin/adiponectin ratio) is suggested to be associated with insulin resistance and cardiometabolic risk. OBJECTIVE: To evaluate associations between fasting serum concentrations of the adipokines (total leptin and adiponectin as well as the L/A ratio) and cardiometabolic comorbidities in children with overweight/obesity. METHODS: A total of 2258 children with overweight/obesity or normal weight aged 6 to 18 years were studied. Differences in anthropometrics and adipokine concentrations were tested using Wilcoxon rank-sum test. Associations between the adipokines and cardiometabolic risk were tested using Spearman's correlation and logistic regression, adjusted for age and body mass index SD score (BMI-SDS). RESULTS: Compared to normal weight children; children with overweight/obesity exhibited higher leptin concentrations, lower adiponectin concentrations, and higher L/A ratios. After adjusting for age and degree of obesity, girls with overweight/obesity in the upper quartile range for the L/A ratio, when compared with girls in the lower quartile range, were more likely to have insulin resistance (odds ratio [OR]: 7.78 [95% confidence interval [CI], 3.78-16.65]), dysglycemia (OR: 3.08 [95% CI, 1.35-7.31]), and dyslipidemia (OR: 2.53 [95% CI, 1.18-5.59]); while boys were more likely to have insulin resistance (OR: 4.45 [95% CI, 2.03-10.10]). CONCLUSIONS: Independent of the degree of obesity, leptin, adiponectin, and the L/A ratio were associated with insulin resistance and other cardiometabolic comorbidities in children with overweight/obesity, but the L/A ratio exhibited stronger associations than the respective adipokines.

Low-grade inflammation independently associates with cardiometabolic risk in children with overweight/obesity.

BACKGROUND AND AIMS: Pediatric obesity associates with both low-grade inflammation and cardiometabolic risk on the population level. Yet on an individual patient level, overweight/obesity does not always equal increased cardiometabolic risk. In this study, we examine whether low-grade inflammation associates with cardiometabolic risk in Danish children, independent of degree of adiposity. We further assess the value of integrating multiple inflammation markers to identify children with very-high cardiometabolic risk profiles. METHOD AND RESULTS: We studied 2192 children and adolescents aged 6-18 years from an obesity clinic cohort and a population-based cohort, in a cross-sectional study design. Anthropometry, blood pressure, pubertal stage and body composition by dual-energy X-ray absorptiometry were assessed, and biomarkers including fasting serum high sensitivity C-reactive protein (hsCRP), white blood cells (WBC), resistin, lipid profile and glucose metabolism were measured. Adjusted correlation analysis and odds ratios were calculated. We found that, independent of degree of adiposity, having high-normal inflammation marker concentrations associated with increased cardiometabolic risk: for girls, hsCRP >0.57-9.98 mg/L (mid/upper tertile) associated with ~2-fold higher odds of dyslipidemia and hepatic steatosis (vs. lower tertile). For both sexes, WBC >7.0-12.4 109/L (upper tertile) associated with 2.5-fold higher odds of insulin resistance. Lastly, children with multiple inflammation markers in the high-normal range exhibited the most severe cardiometabolic risk profile. CONCLUSION: Low-grade inflammation associates with cardiometabolic risk in children independent of degree of adiposity. The associations vary with sex and inflammation marker measured. Finally, integrating multiple low-grade inflammation markers identifies a very-high-risk subgroup of children with overweight/obesity and may have clinical value.

Glucose metabolism in children and adolescents: Population-based reference values and comparisons to children and adolescents enrolled in obesity treatment.

BACKGROUND: Alterations in glucose metabolism that lead to the development of metabolic and cardiovascular disease may begin already in childhood. OBJECTIVE: This study aims to generate pediatric age and sex-specific reference values for fasting concentrations of glucose, hemoglobin A1c (HbA1c), insulin, C-peptide, and homeostasis model assessment: insulin resistance (HOMA-IR) in Danish/North-European white children and adolescents from a population-based cohort and to compare values from children and adolescents with overweight/obesity with this reference. METHODS: The population- and obesity clinic-based cohorts consisted of 2451 and 1935 children and adolescents between 6 and 18 years of age. Anthropometric measurements and blood samples were obtained and percentile curves were calculated. RESULTS: In the population-based cohort, glucose, insulin, and HOMA-IR values increased before the expected onset of puberty (P < .05). Thereafter, all variables decreased in girls (P < .05) and HbA1c decreased in boys (P < .05). Concentrations of all measured markers of glucose metabolism were higher in the obesity clinic-based cohort than the population-based cohort (both sexes P < .001). Specifically, insulin and HOMA-IR continued to increase to 18 years in the clinic-based cohort, particularly among boys. CONCLUSIONS: Fasting glucose, insulin, and HOMA-IR change during childhood, making pediatric reference values essential for timely identification of derangements in glucose metabolism. Children and adolescents with obesity exhibit increased concentrations of these biomarkers.

Next-generation sequencing using microfluidic PCR enrichment for molecular autopsy.

BACKGROUND: We aimed to determine the mutation yield and clinical applicability of "molecular autopsy" following sudden arrhythmic death syndrome (SADS) by validating and utilizing low-cost high-throughput technologies: Fluidigm Access Array PCR-enrichment with Illumina HiSeq 2000 next generation sequencing (NGS). METHODS: We validated and optimized the NGS platform with a subset of 46 patients by comparison with Sanger sequencing of coding exons of major arrhythmia risk-genes (KCNQ1, KCNH2, SCN5A, KCNE1, KCNE2, RYR2). A combined large multi-ethnic international SADS cohort was sequenced utilizing the NGS platform to determine overall molecular yield; rare variants identified by NGS were subsequently reconfirmed by Sanger sequencing. RESULTS: The NGS platform demonstrated 100% sensitivity for pathogenic variants as well as 87.20% sensitivity and 99.99% specificity for all substitutions (optimization subset, n = 46). The positive predictive value (PPV) for NGS for rare substitutions was 16.0% (27 confirmed rare variants of 169 positive NGS calls in 151 additional cases). The overall molecular yield in 197 multi-ethnic SADS cases (mean age 22.6 ± 14.4 years, 68% male) was 5.1% (95% confidence interval 2.0-8.1%), representing 10 cases carrying pathogenic or likely pathogenic risk-mutations. CONCLUSIONS: Molecular autopsy with Fluidigm Access Array and Illumina HiSeq NGS utilizing a selected panel of LQTS/BrS and CPVT risk-genes offers moderate diagnostic yield, albeit requiring confirmatory Sanger-sequencing of mutational variants.

Placental protein-13 (PP13) in combination with PAPP-A and free leptin index (fLI) in first trimester maternal serum screening for severe and early preeclampsia.

BACKGROUND: Placental protein-13 (PP13) is involved in placental invasion and has been suggested as a maternal serum marker of preeclampsia (PE) development. However, the discriminatory ability of PP13 in first trimester has not been completely clarified. METHODS: PP13 was measured in first trimester (week 10+3-13+6) maternal serum from 120 PE pregnancies and 267 control pregnancies and was correlated with clinical parameters. The population screening performance of PP13 in combination with the PE markers pregnancy associated plasma protein A (PAPPA) and free leptin index (fLI) was assessed by Monte Carlo simulation. RESULTS: In severe PE (including HELLP) cases (n=26) the median PP13 concentration was 35.8 pg/mL (range: 17.8-85.5 pg/mL) and in PE pregnancies (n=10) with birth prior to week 34, the median PP13 concentration was 30.6 pg/mL (13.1-50.1 pg/mL), compared to controls with a median of 54.8 pg/mL (range: 15.4-142.6 pg/mL) (p<0.04). The population screening detection rate (DR) for a false-positive rate of 10% for severe PE and HELLP was 26% for PP13, 28% for PP13+PAPP-A, 33% for PP13+fLI, and 40% for PP13+PAPP-A+fLI. CONCLUSIONS: PP13 is a marker of severe PE and HELLP syndrome. The screening performance of PP13 can be markedly improved by combining it with fLI and PAPP-A.

Obstetrical complications in dichorionic twin pregnancies in women with polycystic ovary syndrome.

INTRODUCTION: Both women with polycystic ovary syndrome (PCOS) and women with twin pregnancies have increased risk of adverse pregnancy outcome. The aim of this study was to investigate the impact of PCOS and maternal androgen levels on the outcome of dichorionic twin pregnancy. MATERIAL AND METHODS: A retrospective study of 360 women with dichorionic twin pregnancies: 72 women with PCOS from a fertility clinic (years 1997-2010) and 288 women without PCOS from a hospital cohort (years 2005-2007). The obstetrical outcome was extracted from Danish National registers and supplemented by patient file data. In all, 65% of the PCOS group had a registered prepregnancy androgen level and these were stratified into normoandrogenic and hyperandrogenic women. The groups were compared by multiple regression analysis adjusting for mode of conception and prepregnancy body mass index. RESULTS: We found no overall impact of PCOS on the pregnancy outcome; the risks of preeclampsia, gestational diabetes and preterm delivery were comparable within the groups. However, five deliveries in the PCOS group compared with two in the control group occurred before gestational week 28. No difference in the obstetrical outcome between hyperandrogenic and normoandrogenic women was found. The body mass index in the PCOS population was lower than in the non-PCOS, possibly reflecting a higher socioeconomic status and a healthier lifestyle, which may underestimate the impact of a PCOS diagnosis. CONCLUSION: Neither PCOS nor maternal androgen levels confer additional risks to the outcome of dichorionic twin pregnancies of normal weight women.

Pregnancy-associated plasma protein-A (PAPP-A) and the proform of the eosinophil major basic protein (ProMBP) are associated with increased risk of death in heart failure patients.

Risk stratification and patient management in heart failure (HF) is difficult due to the unpredictable progression of the disease, necessitating the development of reliable diagnostic biomarkers to facilitate decision-making in clinical practice. Pregnancy-associated plasma protein-A (PAPP-A) is a marker of arteriosclerotic heart disease. PAPP-A is a serum protease, which is involved in the insulin-like growth factor 1 (IGF-1) axis where it is inhibited by the proform of the eosinophil major basic protein (proMBP). In this study, we evaluated serum PAPP-A and proMBP as long-term prognostic biomarkers of all-cause mortality in HF. Serum PAPP-A and proMBP concentrations were determined in 683 patients with NYHA III-IV HF recruited in the EchoCardiography and Heart Study (ECHOS) in Denmark. The mean age of the patients (73% male) was 70 at admission. During 7 years of follow-up, 516 patients died. In univariate analysis, both PAPP-A and proMBP, divided into quartiles, showed significant association with mortality. Using a Cox proportional hazard model, hazard ratios for continuous values of PAPP-A and proMBP were HR = 1.42 (CI = 1.23-1.64, p < 0.0001) and HR = 1.36 (CI = 1.22-1.51, p <0.0001), respectively. However, neither PAPP-A nor proMBP were significant independent predictors when the model included age, gender, brain-type natriuretic peptide, medical history of HF, ischemic heart disease, chronic obstructive pulmonary disease, and diabetes mellitus. In conclusion, high levels of PAPP-A and proMBP are associated with increased risk of death from all causes in HF and are potential prognostic markers of adverse outcomes in HF patients.

Mutations in calmodulin cause ventricular tachycardia and sudden cardiac death.

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a devastating inherited disorder characterized by episodic syncope and/or sudden cardiac arrest during exercise or acute emotion in individuals without structural cardiac abnormalities. Although rare, CPVT is suspected to cause a substantial part of sudden cardiac deaths in young individuals. Mutations in RYR2, encoding the cardiac sarcoplasmic calcium channel, have been identified as causative in approximately half of all dominantly inherited CPVT cases. Applying a genome-wide linkage analysis in a large Swedish family with a severe dominantly inherited form of CPVT-like arrhythmias, we mapped the disease locus to chromosome 14q31-32. Sequencing CALM1 encoding calmodulin revealed a heterozygous missense mutation (c.161A>T [p.Asn53Ile]) segregating with the disease. A second, de novo, missense mutation (c.293A>G [p.Asn97Ser]) was subsequently identified in an individual of Iraqi origin; this individual was diagnosed with CPVT from a screening of 61 arrhythmia samples with no identified RYR2 mutations. Both CALM1 substitutions demonstrated compromised calcium binding, and p.Asn97Ser displayed an aberrant interaction with the RYR2 calmodulin-binding-domain peptide at low calcium concentrations. We conclude that calmodulin mutations can cause severe cardiac arrhythmia and that the calmodulin genes are candidates for genetic screening of individual cases and families with idiopathic ventricular tachycardia and unexplained sudden cardiac death.

Combined gating and trafficking defect in Kv11.1 manifests as a malignant long QT syndrome phenotype in a large Danish p.F29L founder family.

BACKGROUND: Congenital long QT syndrome (LQTS) is a hereditary cardiac channelopathy characterized by delayed ventricular repolarization, syncope, torsades de pointes and sudden cardiac death. Thirty-three members of five apparently 'unrelated' Danish families carry the KCNH2:c.87C> A; p.F29L founder mutation. METHODS AND RESULTS: Linkage disequilibrium mapping with microsatellites around KCNH2 enabled us to estimate the age of the founder mutation to be approximately 22 generations, corresponding to around 550 years. Neighbouring-Joining analysis disclosed one early and three later nodes. The median QTc time of the carriers was 490 ms (range: 415-589 ms) and no difference was seen between the different branches of the family. The mutation is malignant with a penetrance of 73%. Ten F29L carriers received implantable defibrillators (ICDs) (median age at implant 20 years), and of those four individuals experienced eight appropriate shocks. Patch-clamp analysis in HEK 293 cells, performed at 34°C disclosed a loss-of-function phenotype with fast deactivation, reduced steady-state inactivation current density and a positive voltage shift in inactivation. Western blotting of HEK 293 cells transfected with KCNH2:WT and KCNH2:c.87C> A revealed a reduced fraction of fully glycosylated hERG:p.F29L suggesting that this mutation results in defective trafficking. CONCLUSION: The altered channel gating kinetics in combination with defective trafficking of mutated channels is expected to result in reduced repolarizing current density and, thus, a LQTS phenotype.

Mutations in Danish patients with long QT syndrome and the identification of a large founder family with p.F29L in KCNH2.

BACKGROUND: Long QT syndrome (LQTS) is a cardiac ion channelopathy which presents clinically with palpitations, syncope or sudden death. More than 700 LQTS-causing mutations have been identified in 13 genes, all of which encode proteins involved in the execution of the cardiac action potential. The most frequently affected genes, covering > 90% of cases, are KCNQ1, KCNH2 and SCN5A. METHODS: We describe 64 different mutations in 70 unrelated Danish families using a routine five-gene screen, comprising KCNQ1, KCNH2 and SCN5A as well as KCNE1 and KCNE2. RESULTS: Twenty-two mutations were found in KCNQ1, 28 in KCNH2, 9 in SCN5A, 3 in KCNE1 and 2 in KCNE2. Twenty-six of these have only been described in the Danish population and 18 are novel. One double heterozygote (1.4% of families) was found. A founder mutation, p.F29L in KCNH2, was identified in 5 "unrelated" families. Disease association, in 31.2% of cases, was based on the type of mutation identified (nonsense, insertion/deletion, frameshift or splice-site). Functional data was available for 22.7% of the missense mutations. None of the mutations were found in 364 Danish alleles and only three, all functionally characterised, were recorded in the Exome Variation Server, albeit at a frequency of < 1:1000. CONCLUSION: The genetic etiology of LQTS in Denmark is similar to that found in other populations. A large founder family with p.F29L in KCNH2 was identified. In 48.4% of the mutations disease causation was based on mutation type or functional analysis.

Flecainide provocation reveals concealed brugada syndrome in a long QT syndrome family with a novel L1786Q mutation in SCN5A.

BACKGROUND: Mutations in SCN5A can result in both long QT type 3 (LQT3) and Brugada syndrome (BrS), and a few mutations have been found to have an overlapping phenotype. Long QT syndrome is characterized by prolonged QT interval, and a prerequisite for a BrS diagnosis is ST elevation in the right precordial leads of the electrocardiogram. METHODS AND RESULTS: In a Danish family suffering from long QT syndrome, a novel missense mutation in SCN5A, changing a leucine residue into a glutamine residue at position 1786 (L1786Q), was found to be present in heterozygous form co-segregating with prolonged QT interval. The proband presented with an aborted cardiac arrest, and his mother died suddenly and unexpectedly at the age of 65. Flecainide treatment revealed coved ST elevation in all mutation carriers. Electrophysiological investigations of the mutant in HEK293 cells indicated a reduced peak current, a negative shift in inactivation properties and a positive shift in activation properties, compatible with BrS. Furthermore, the sustained (I(Na,late)) tetrodotoxin-sensitive sodium current was found to be drastically increased, explaining the association between the mutation and LQT syndrome. CONCLUSIONS: The L1786Q mutation is associated with a combined LQT3 and concealed BrS phenotype explained by gating characteristics of the mutated ion channel protein. Hence, sodium channel blockade should be considered in clinical evaluation of apparent LQT3 patients.

MicroRNAs in cardiac arrhythmia: DNA sequence variation of MiR-1 and MiR-133A in long QT syndrome.

Long QT syndrome (LQTS) is a genetic cardiac condition associated with prolonged ventricular repolarization, primarily a result of perturbations in cardiac ion channels, which predisposes individuals to life-threatening arrhythmias. Using DNA screening and sequencing methods, over 700 different LQTS-causing mutations have been identified in 13 genes worldwide. Despite this, the genetic cause of 30-50% of LQTS is presently unknown. MicroRNAs (miRNAs) are small (∼ 22 nucleotides) noncoding RNAs which post-transcriptionally regulate gene expression by binding complementary sequences within messenger RNAs (mRNAs). The human genome encodes over 1800 miRNAs, which target about 60% of human genes. Consequently, miRNAs are likely to regulate many complex processes in the body, indeed aberrant expression of various miRNA species has been implicated in numerous disease states, including cardiovascular diseases. MiR-1 and MiR-133A are the most abundant miRNAs in the heart and have both been reported to regulate cardiac ion channels. We hypothesized that, as a consequence of their role in regulating cardiac ion channels, genetic variation in the genes which encode MiR-1 and MiR-133A might explain some cases of LQTS. Four miRNA genes (miR-1-1, miR-1-2, miR-133a-1 and miR-133a-2), which encode MiR-1 and MiR-133A, were sequenced in 125 LQTS probands. No genetic variants were identified in miR-1-1 or miR-133a-1; but in miR-1-2 we identified a single substitution (n.100A> G) and in miR-133a-2 we identified two substitutions (n.-19G> A and n.98C> T). None of the variants affect the mature miRNA products. Our findings indicate that sequence variants of miR-1-1, miR-1-2, miR-133a-1 and miR-133a-2 are not a cause of LQTS in this cohort.