Alpha-protein kinase 3 (ALPK3) truncating variants cause an autosomal dominant form of hypertrophic cardiomyopathy

Background

More than half of hypertrophic cardiomyopathy (HCM) remains genetically unsolved. ALPK3 truncating variants (ALPK3tv) have been described as a cause of autosomal recessive cardiomyopathy in a small number of paediatric cases, but the pathogenicity in heterozygosity as a possible cause of autosomal dominant HCM is unknown.

Aims

To determine the frequency of heterozygous ALPK3tv in patients with HCM and to confirm their pathogenicity by means of burden testing in independent cohorts, family co-segregation studies, and functional analysis of an allelic series of ALPK3tv using human embryonic stem cell-cardiomyocytes (hESC-CM). Phenotype was compared with a cohort of 1679 genotyped HCM patients.

Methods and results

In a discovery cohort of 770 index patients with HCM, 12 (1.56%) were heterozygous for ALPK3tv, odds ratio (OR) 16.01 (95% confidence interval (95% CI): 7.89 to 29.74, p<8.36e-11), compared to the Genome Aggregation Database (gnomAD) population. In a validation cohort of 2047 HCM probands, 32 (1.56%) carried heterozygous ALPK3tv, OR 16.17 (95% CI: 10.31 to 24.87; p<2.2e-16, compared to gnomAD). Combined logarithm of odds score in 7 families with ALPK3tv was 2.99. In comparison with a large cohort of genotyped HCM patients, the phenotype of 51 HCM patients with ALPK3tv (probands and relatives) was characterised by a higher prevalence of apical/concentric patterns of hypertrophy (60%) compared to both sarcomere-positives or negatives (p<0.001 overall), with the age at diagnosis (56±16ys) and maximum wall thickness (18±4mm) similar to sarcomere-negatives and LV systolic impairment at baseline (6%) and non-sustained ventricular tachycardia (31%) similar to sarcomere-positives. Short PR (10%, p=0.009 overall) and extensive fibrosis>15% of LV segments (49%) were distinctive features. During follow-up (5.3±5.7 years), 4 (9%) patients died of heart failure or had cardiac transplantation (p=0.012 vs sarcomere-negatives and p=0.425 vs sarcomere-positives). Analysis of hESC-CM showed that ALPK3 heterozygotes had phenotypic characteristics of HCM, including increased contractile force and delayed membrane repolarization.

Conclusions

Heterozygous ALPK3tv are pathogenic and segregate with a characteristic HCM phenotype.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): MRC UK, UCLH BRC

Left ventricular remodelling in a large cohort of strength competitive athletes: not so common and differs by sex

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This research was supported by FMBA of Russia

Background. There are still very limited data about physiological cardiac adaptation in strength athletes. 

Purpose. To describe structural and functional features of left ventricular (LV) in a large cohort of healthy strength athletes.

Methods. A total of 673 Caucasian athletes (weight-lifting, males/females = 238/157, and Martial Arts, males/females = 200/78) competing in Russian National and International level events were recruited within 2010-2017. Data of standard 2D echocardiography (Echo) and comprehensive medical history were analyzed. Data are presented as median (IQR) and compared by nonparametric tests (table). To assess LV geometry all athletes were divided into 6 groups according to 4-tiered classification based on mass index, concentricity and end-diastolic volume (EDV) index of LV (Figure). 

Results. Both absolute and indexed values of LV structural features were higher in males. Females exhibited higher functional parameters. Only 54 (8%) athletes had elevated LV mass (no sex difference), 23 (3.4%) – LV wall ≥ 12mm (only males) and 78 (11.6%) – changes in LV geometry. There was a prevalence of females in eccentric non-dilated LV hypertrophy (LVH) group (p = 0.088), which was previously accepted as a benign pattern of LV remodelling in non-athlete populations. Males had more often concentric types of LV remodelling (36 of 54 athletes). Among dilated types of LVH, there was a prevalence of males (p = 0.070).

Conclusions. LV remodelling is not common in strength athletes and differs by sex with a more favourable profile in females.

Clinical and Echo parameters Total n = 673 males n = 438 females n = 235 males vs females p-value Age, years 20(4) 20(4) 20(5) 0.06 BSA, m² 1.84(0.39) 1.96(0.39) 1.66(0.25) <0.001 Sports practice, years 10(6) 10(7) 10(6) 0.12 LV EDD, mm 49(6) 50(5) 46(4) <0.001 LV EDD/(BSA)^0.5 35.8(3) 35.9(3) 35.6(3) 0.017 LV EDV, ml 108(38) 118(32) 92(24) <0.001 LV EDV/(BSA)^1.5 42.8(9) 42.9(10) 42.3(9) 0.14 Maximal LV WT, mm 10(1) 10(2) 9(1) <0.001 LV mass/BSA, g/m² 86(24) 91(22) 75(16) <0.001 LV Concentricity, g/(ml)^0.67 6.9(1.6) 7.4(1.6) 6.2(1.4) <0.001 LV EF, % 60(5) 60(4) 62(4) <0.001 Mitral E velocity, cm/sec 87(19) 85(19) 89(19) <0.001 BSA - body surface area; EDD - end-diastolic dimension; WT - wall thickness

Abstract Figure. Types of LV geometry in athletes

The response of the neuronal membrane to acetaldehyde treatment

To assess the effects of acetaldehyde (AA) on the native synaptosomal membranes, we used the atomic force microscopy (AFM) and fluorescent methods. A wide range of concentrations (from 2 to 4000 microM) of AA was studied. The visualization of synaptosomes by AFM showed structural changes in the synaptosomal surface at an AA concentration of 50 microM, which is comparable with the AA concentrations occurring during ethanol intoxication. In our study, we observed that AA at small concentrations (up to 50 microM) considerably decreased the microviscosity of the hydrophobic region of the bulk membrane lipids (the ratio of the monomeric and excimeric probe fluorescence decreased). These findings correlate with the AFM study on the effect of 50 microM AA on the washed synaptosome membranes.