The Number of GT(n) Repeats in the Hemeoxygenase-1 Gene Promoter is Increased in Pediatric Heart Failure but is Unrelated to Renal, Antioxidant and Anti-inflammatory Markers

Subjects with coronary artery disease and reduced ejection fraction have longer (GT)n repeats in the heme-oxygenase 1 gene promoter

Heme oxygenase (HO)-1 is a rate-limiting enzyme for degrading heme into carbon monoxide. Longer (GT)_n repeat of the HO-1 gene (HMOX1) promoter has a lower transcription rate. Subjects with longer GT repeats in the HMOX1 promoter are more likely to have coronary artery disease (CAD) and cardiovascular events. We retrospectively enrolled CAD subjects with an abnormal ejection fraction (EF) < 50% from our catheterization data (N = 670). Polymerase chain reactions were performed for amplifying the HMOX1 promoter GT repeating segment to determine the number of repeats. Two subgroups, reduced EF < 40% (N = 256), and mid-range EF 40-49% (N = 414), were compared. The distribution of genotypes of SS, SL and LL were significantly different in reduced EF (29%, 48%, 23%) vs. mid-range EF CAD (64%, 30%, 5%) (S allele: ≤ 30 repeats, L allele: > 30 repeats) (p < 0.001). The patients with reduced EF had a significantly longer average (GT)_n (median 27.5 vs. 26.5, p = 0.004) than those with the mid-range EF. In multivariate analysis, the carrier of L allele (odds ratio 4.437, p < 0.001) was a significant predictor for the diagnosis of reduced vs. mid-range EF CAD. In conclusion, CAD patients with reduced EF had longer HMOX1 promoter (GT)_n repeats than those with mid-range EF.

Genetics of inherited cardiomyopathies in Africa

In sub-Saharan Africa (SSA), the burden of noncommunicable diseases (NCDs) is rising disproportionately in comparison to the rest of the world, affecting urban, semi-urban and rural dwellers alike. NCDs are predicted to surpass infections like human immunodeficiency virus, tuberculosis and malaria as the leading cause of mortality in SSA over the next decade. Heart failure (HF) is the dominant form of cardiovascular disease (CVD), and a leading cause of NCD in SSA. The main causes of HF in SSA are hypertension, cardiomyopathies, rheumatic heart disease, pericardial disease, and to a lesser extent, coronary heart disease. Of these, the cardiomyopathies deserve greater attention because of the relatively poor understanding of mechanisms of disease, poor outcomes and the disproportionate impact they have on young, economically active individuals. Morphofunctionally, cardiomyopathies are classified as dilated, hypertrophic, restrictive and arrhythmogenic; regardless of classification, at least half of these are inherited forms of CVD. In this review, we summarise all studies that have investigated the incidence of cardiomyopathy across Africa, with a focus on the inherited cardiomyopathies. We also review data on the molecular genetic underpinnings of cardiomyopathy in Africa, where there is a striking lack of studies reporting on the genetics of cardiomyopathy. We highlight the impact that genetic testing, through candidate gene screening, association studies and next generation sequencing technologies such as whole exome sequencing and targeted resequencing has had on the understanding of cardiomyopathy in Africa. Finally, we emphasise the need for future studies to fill large gaps in our knowledge in relation to the genetics of inherited cardiomyopathies in Africa.