Influence of sex on cardiovascular outcomes in RBM20 variant carriers

Background

Variants in the RBM20 gene cause dilated cardiomyopathy and may be associated with a poor prognosis.

Objectives

To determine disease penetrance, the risk of adverse events and the influence of sex on outcomes in RBM20 variant carriers.

Methods

Consecutive probands and relatives carrying pathogenic or likely pathogenic RBM20 variants were retrospectively recruited from 12 cardiomyopathy units. The primary endpoint was a composite of malignant ventricular arrhythmia (MVA) and end-stage heart failure (ESHF). MVA and ESHF endpoints were also analysed separately and males and females compared.

Results

Longitudinal follow-up data were available for 163 RBM20 variant carriers (82 male, median age 36.5 years, median follow-up 77.6 months). 10/163 had an MVA event at baseline. 30/153 without baseline MVA (19.6%) reached the primary endpoint with a trend towards worse outcomes in males (p=0.08). 16/153 (10.5%) had new MVA with no difference between males and females (p=0.92). 20/163 (12.2%) developed ESHF (17 males and 3 females; p<0.001).

By the end of follow-up, 114 patients (70%) had either left ventricular systolic dysfunction (LVSD) or had experienced MVA. 22 patients received a first diagnosis of LVSD during follow-up. Disease penetrance in individuals over 40 years of age was 78.5% by last evaluation.

Eleven patients that reached the MVA endpoint had a left ventricular ejection fraction (LVEF) available within 6 months of the event. Median [IQR] contemporary LVEF was 30% [23.75, 40%]. 5/11 patients had a contemporary LVEF >35%. 1/11 had a contemporary LVEF >45% (a female, 1st degree relative presenting with sustained ventricular tachycardia and an LVEF of 65%).

Conclusions

RBM20 variants are highly penetrant. The risk of MVA in male and female RBM20 variant carriers is similar but male sex is strongly associated with ESHF. MVA events occur in patients with LVEF >35%.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): British Heart Foundation Clinical Research Training Fellowship

Genetic regulation of myocardial fibrosis in hypertrophic cardiomyopathy

Background

Myocardial fibrosis is a common feature of hypertrophic cardiomyopathy (HCM) but its pathophysiology has yet to be elucidated.

Purpose

In this study, we used a multiplex approach to examine the genetic regulation of pathways associated with fibrosis in patients undergoing septal myectomy.

Methods

Myocardial tissue was collected at time of surgical intervention. Control biopsy samples were obtained from the left ventricular free wall from structurally normal hearts during autopsy following non-cardiac related death. Tissue was either snap frozen in liquid nitrogen and subsequently stored at −80 degrees or collected in RNA laterTM and frozen 24 hours later at −80 degrees. Total RNA was extracted from HCM tissue samples using the Qiagen RNeasy fibrous tissues mini kit and from control samples using mirVana isolation kit (Ambion), according to the manufacturer's protocol. Quantitative PCR (qPCR) was performed on the extracted RNA using a RT. Profiler™ Human finrosis PCR Array.

Results

The study cohort comprised 22 HCM samples and 5 controls. The relative regulation of genes involved in myocardial fibrosis in patients with HCM compared to controls is shown in figure 1.

In patients with HCM, there was increased expression of genes involved in collagen synthesis. A significant two-fold upregulation in type III procollagen mRNA was observed relative to controls (p=0.013) with a similar trend identified for type I procollagen (1.5 fold up-regulation, p=0.081). The gene expression of MMP3 (−1.5 fold, p=0.029) and MMP8 (−1.8, p=0.002) which are involved in collaged degradation were downregulated in the HCM group.

The gene expression of pro-fibrotic mediators TGF-β2 (4.8 fold, p=0.008) and CCN2 (2.9 fold, p=0.021) was also significantly elevated. Within the HCM group, there was a correlation between the fold regulation of TGF-β1 (r=0.570, p=0.006; r=0.528, p=0.012), TGF-β2 (r=0.569, p=0.006; r=0.514, p=0.014) and TGF-β3 (r=0.738, p<0.001; r=0.496, p=0.019) to gene regulation of type I and III procollagens respectively.

The expression of BMP-7 which has been shown to reduce myocardial fibrosis by antagonising TGF- β mediated endothelial – mesothelial transformation of fibroblasts was also down-regulated in HCM (−3.8, p=0.015).

Conclusions

Genetic expression of procollagen is significantly upregulated in patients with HCM relative to controls. TGF-β and CCN2 mediated signalling appear to be key mediators in promoting collagen expression.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): Heart Hospital Charitable Grant, UK Figure 1. Gene expression in HCM

Penetrance of hypertrophic cardiomyopathy and outcome in sarcomeric mutation carriers

Background

Predictive genetic screening of the first degree relatives of patients with hypertrophic cardiomyopathy (HCM) caused by sarcomere protein (SP) gene mutations is current standard of care, but there are few data on long-term outcomes in mutation carriers without HCM.

Purpose

To establish the role of sex and genotype in HCM penetrance as well as the rate of major adverse clinical events in SP mutation carriers and following the diagnosis of HCM.

Methods

Retrospective analysis of consecutive adult and paediatric SP mutation carriers identified during family screening and who did not fulfill diagnostic criteria for HCM at first evaluation.

Results

321 individuals from 170 families [median age first evaluation 15.2 years (IQR 7.3–32.6); 153 (47.7%) males] were evaluated. Causal SP genes were: MYBPC3 (n=133 (41.4%)), MYH7 (n=77 (24.0%)), TNNI3 (n=51 (15.9%)), TNNT2 (n=40 (12.5%)), TPM1 (n=9 (2.8%)), MYL2 (n=6 (1.9%)), and ACTC1 (n=1 (0.3%)); 4 (1.3%) carried multiple mutations.

After a median follow up of 7.4 years (IQR 2.5–12.7), 89 (27.7%) patients developed HCM. Disease penetrance at the age of 50 years was 47% (95% CI 38%-56%). One hundred and fifty three (47.7%) individuals underwent cardiac magnetic resonance (CMR) imaging; among those diagnosed with HCM, 22/89 (24.7%) fulfilled criteria on CMR but not echocardiography.

In a multivariable model adjusted for genotype, follow up duration and evaluation with CMR, independent predictors of HCM development were male sex (HR 3.11; CI 1.82–5.32) and abnormal ECG (HR 7.87; CI 4.43–13.97). Patients with MYH7 and multiple mutations were more likely to develop HCM than those with MYBPC3 mutations (HR 2.03; CI 1.04–3.96 and HR 10.13; CI 1.40–72.92, respectively). Disease penetrance was lowest in carriers of TNNI3 mutations (HR 0.13; CI 0.03–0.48).

There were no major adverse events in individuals without HCM. Following the diagnosis of HCM, the combined rate of all-cause death, appropriate defibrillator shock or resuscitated cardiac arrest was 1.1%/year [median follow up 4.0 years (IQR 2.1–8.9)].

Conclusions

Approximately 50% of SP mutation carriers develop HCM by the age of 50 and become prone to disease complications during long-term follow-up. Sex, MYH7 mutations and the presence of an abnormal ECG are associated with a higher risk of disease development. CMR should be employed systematically in long-term screening.

HCM penetrance by sex

Funding Acknowledgement

Type of funding source: None

The influence of age on the diagnostic yield of genetic testing in dilated cardiomyopathy

Background

Dilated cardiomyopathy (DCM) has an estimated population prevalence of 1/250 and is the underlying diagnosis in a third of heart failure patients. A substantial proportion of patients have familial disease caused by dominant mutations in one of more than 50 genes, but clinical practice guidelines recommend genetic testing in young patients with idiopathic DCM. There is an absence of robust data on the influence of age on the diagnostic yield of genetic testing.

Methods

The study cohort comprised 825 consecutive and unrelated patients (524 male (63.5%)) with DCM who underwent genetic testing from 2015 to 2019. Genetic variants were classified using American College of Medical Genetics (ACMG) criteria. Analyses were stratified by age and sex.

Results

173 (20.1%) patients had a positive genetic test (“pathogenic” or “likely pathogenic” variant); 292 (34.4%) had a variant of unknown significance. Mean age at genetic testing was 49.9±14.4 years. Mean age of patients with a positive test was 47.6±13.6 years. 99 (18.9%) men and 67 (22.3%) women had a positive test (p=0.246).

Mutations in the TTN gene, encoding for titin, accounted for 46.1% of positive results. 13.8% of mutations were in DSP, 8.4% in RBM20, 6% in FLNC, 4.2% in LMNA, 3.6% in BAG3 and 3.6% in MYH7.

There was a trend to declining yield with age (likelihood ratio chi-square p value = 0.047). The yield was 17.2% in the 56–65 year age group and 11.5% above 66 years of age (figure 1).

Conclusions

Approximately 1 in 5 patients with DCM had a positive genetic test. The yield declined in patients over 66 years but remained above 11%, suggesting that genetic testing should not be confined to younger patients with DCM.

Figure 1. Yield of Genetic Testing by Age

Funding Acknowledgement

Type of funding source: None

1174Characterization of disease hot-phases using 18f-fluorodeoxyglucose positron emission tomography in arrhythmogenic cardiomyopathy caused by desmosomal gene mutations

Introduction

Mutations in the genes encoding for desmosomal proteins are associated with Arrhythmogenic Cardiomyopathy (AC), a condition in which “hot-phases” reminiscent of myocarditis can develop and which represent active disease progression. Detection of hot-phase disease can offer novel treatment opportunities.

Purpose

We used 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) to determine the prevalence of myocardial inflammation during clinical hot phases in AC.

Methods

Nineteen (12 male; age 38±14 years) symptomatic desmosomal gene mutation carriers (PKP-2, n=6; DSG-2, n=3; DSC-2, n=1; DSP, n=9) underwent FDG-PET and cardiac magnetic resonance (CMR). AC was diagnosed according to the 2010 Task Force diagnostic criteria. The indication for FDG-PET was presentation with clinically suspected myocarditis in 10 (53%), increase in arrhythmic burden in 4 (21%), deteriorating left ventricular (LV) systolic function in 3 (16%) and as part of a diagnostic workup in 2. We compared regional distribution of FDG uptake and late gadolinium enhancement (LGE) on CMR using a standard 16-segment model. Concordance between the two tests was defined as >50% of segment overlap and partial concordance as 1- 50%. Cohen's κ was used to evaluate the inter-method agreement between FDG and LGE.

Results

Nine (47%) patients (5 male) had LV heterogeneous FDG uptake. RV uptake was never observed. Eight of these cases had a definite and 1 had a borderline diagnosis of AC. FDG uptake associated with the presence of DSP gene mutations (7/9, 78% vs 2/10, 20%, p=0.02) and older age (44±12 vs 33±15 years, p=0.05). Concurrent CMR study was available in 15 patients, including all nine with a positive FDG-PET. RV LGE was present in 6 (40%) and LV LGE in 14 cases (93%). All nine (100%) patients with FDG uptake had LV LGE. The commonest segments with FDG-uptake were the basal-anterior, mid-inferolateral and mid-anterolateral (5 cases, 56%), whereas LGE was most commonly present in the mid-anteroseptal (8 cases, 89%) followed by the basal- and mid-inferior segments (6 cases, 67%). Concordance of FDG uptake and LGE was present in 2 cases (22%). There was no concordance in 1 case (11%). Partial concordance was present in 6 (67%). There was poor inter-method topographical agreement between FDG-PET and CMR, κ = 0.04, p=0.64.

Conclusion

Up to 50% of desmosomal gene positive AC patients, and especially those with DSP mutations, and clinical “hot phases” have evidence for myocarditis on FDG-PET. The topographical variation between PET and CMR highlight the underlying pathophysiological stage of disease (inflammation versus scar) and suggest that the imaging modalities provide complementary information on tissue characterisation in AC.

Acknowledgement/Funding

Alexandros Protonotarios is funded by a BHF Clinical Research Training Fellowship no. FS/18/82/34024

P3686A novel desmin gene variant as an important cause of biventricular arrhythmogenic cardiomyopathy

Introduction

Arrhythmogenic Cardiomyopathy (AC) is typically caused by mutations in the desmosomal genes, however non-desmosomal genes have been increasingly implicated. Desmin gene (DES) mutations have been previously reported in AC, but in many cases there are insufficient data to support their pathogenicity.

Purpose

We assessed our AC cohort for DES gene mutations and describe the clinical phenotype associated with a recurring variant present in 3 unrelated families.

Methods

Genetic testing was performed using next-generation sequencing for 41 genes in a total of 138 AC probands with a definite diagnosis of AC based on the revised 2010 Task Force diagnostic criteria. All candidate variants were confirmed using Sanger sequencing. Clinical and genetic cascade screening were expanded to the first-degree relatives of the probands. Retained tissue from deceased individuals was used for genetic testing. All living mutation carriers underwent clinical assessment including physical examination, 12-lead ECG, signal-averaged ECG, echocardiography, cardiac magnetic resonance imaging (MRI) and 24h Holter-monitoring.

Results

Two DES gene variants, p.Ser298Leu (n=1) and p.Leu115Ile (n=3), were identified in 4 out of the 138 probands (3%). The former coexisted with a pathogenic DSP gene mutation and has not been further evaluated. The latter is a novel variant, absent in control databases (gnomAD) and was the only variant present in 3 unrelated families (see figure). One carrier required heart transplant (A-II-1), two died suddenly (A-III-1, B-II-1) and one died of non-cardiac causes (B-I-2). Detailed clinical information was present in 8 mutation carriers (2 male, age 45±19 years). Seven (88%) had a definite diagnosis and one had a borderline diagnosis of AC. All cases (100%) had right ventricular (RV) wall motion abnormalities, 6 (75%) had a dilated RV, 6 (75%) a dilated LV and 6 (75%) had LV dysfunction (mild in 5 and severe in 1). LV late gadolinium enhancement (LGE) was present in all 6 carriers that had a cardiac MRI with a circumferential sub-epicardial distribution (see figure, case A-III-2). Non-sustained ventricular tachycardia (VT) was present in 7 (88%) and sustained VT in 2 cases (25%). The ventricular ectopic burden per 24h ranged from 426 to 10583 with a median value of 820.

Figure 1

Conclusion

Variants of the DES gene are rare causes of AC. The novel p.Leu115Ile variant seems to be prevalent in a large UK-based cohort and it causes a biventricular form of AC, with a characteristic scar pattern on MRI and severe outcomes.

Acknowledgement/Funding

Alexandros Protonotarios is supported by a BHF Clinical Research Training Fellowship no. FS/18/82/34024

Loss-of-function desmoplakin I and II mutations underlie dominant arrhythmogenic cardiomyopathy with a hair and skin phenotype

BACKGROUND

Arrhythmogenic cardiomyopathy (AC) is an inherited, frequently underdiagnosed disorder, which can predispose individuals to sudden cardiac death. Rare, recessive forms of AC can be associated with woolly hair and palmoplantar keratoderma, but most autosomal dominant AC forms have been reported to be cardiac specific. Causative mutations frequently occur in desmosomal genes including desmoplakin (DSP).

OBJECTIVES

In this study, we systematically investigated the presence of a skin and hair phenotype in heterozygous DSP mutation carriers with AC.

METHODS

Six AC pedigrees with 38 carriers of a dominant loss-of-function (nonsense or frameshift) mutation in DSP were evaluated by detailed clinical examination (cardiac, hair and skin) and molecular phenotyping.

RESULTS

All carriers with mutations affecting both major DSP isoforms (DSPI and II) were observed to have curly or wavy hair in the pedigrees examined, except for members of Family 6, where the position of the mutation only affected the cardiac-specific isoform DSPI. A mild palmoplantar keratoderma was also present in many carriers. Sanger sequencing of cDNA from nonlesional carrier skin suggested degradation of the mutant allele. Immunohistochemistry of patient skin demonstrated mislocalization of DSP and other junctional proteins (plakoglobin, connexin 43) in the basal epidermis. However, in Family 6, DSP localization was comparable with control skin.

CONCLUSIONS

This study identifies a highly recognizable cutaneous phenotype associated with dominant loss-of-function DSPI/II mutations underlying AC. Increased awareness of this phenotype among healthcare workers could facilitate a timely diagnosis of AC in the absence of overt cardiac features.

Polymorphism in apolipoprotein(a) kringle IV 37(Met/Thr): frequency in a London population and its association with coronary artery disease

BACKGROUND

A raised concentration of lipoprotein(a) [Lp(a)] in human plasma has been considered as a risk factor for coronary artery disease (CAD). Apolipoprotein(a) and plasminogen genes are exceptionally similar to a variable number of plasminogen-like kringle IV repeats in the apo(a) gene. Polymorphisms have been previously identified in the apolipoprotein(a) kringle IV 37.

HYPOTHESIS

In order to determine the frequency of the apolipoprotein(a) kringle IV 37 Met66-->Thr polymorphism in a London-based population and to assess the relationship of this polymorphism with CAD in Caucasian patients, we genotyped two groups of people of different ethnic origin (Caucasian and Afro-Caribbean) for the mutation using standard polymerase chain reaction (PCR) techniques.

METHODS

The first group consisted of 182 unrelated Caucasian patients (107 men and 75 women, mean age 59.7 +/- 10.2 years) recruited at St. George's Hospital. They were defined as patients with 0, 1 or > or = 2 vessel disease patients depending on the degree of stenosis in none, one, or several major epicardial arteries. The second group comprised 64 unrelated patients of Afro-Caribbean origin attending a hypertension clinic at St. George's Hospital.

RESULTS

It was shown that the prevalence of the Met66-->Thr mutation is markedly higher in Caucasians than in Afro-Caribbeans and that this mutation is not associated with either Lp(a) levels or severity of CAD.

Idiopathic restrictive cardiomyopathy in children is caused by mutations in cardiac sarcomere protein genes

BACKGROUND

Restrictive cardiomyopathy (RCM) is rare in childhood, but has a grave prognosis. The cause of disease in most cases is unknown.

OBJECTIVE

To determine the prevalence of sarcomere protein gene mutations in children with idiopathic RCM.

METHODS

Twelve patients (9 female, mean age 5.1 years) with idiopathic RCM referred between 1991 and August 2006 underwent detailed clinical and genetic evaluation. Nine had received cardiac transplants at the time of the study. The entire coding sequences of the genes encoding eight cardiac sarcomere proteins and desmin were screened for mutations. Familial evaluation was performed on first-degree relatives.

RESULTS

Four patients (33%) had a family history of cardiomyopathy: RCM (n = 2); dilated cardiomyopathy (n = 1) and left ventricular non-compaction (n = 1). Sarcomere protein gene mutations were identified in four patients (33%): 2 in the cardiac troponin I gene (TNNI3) and 1 each in the troponin T (TNNT2) and alpha-cardiac actin (ACTC) genes. Two were de novo mutations and 3 were new mutations. All mutations occurred in functionally important and conserved regions of the genes.

CONCLUSIONS

Sarcomere protein gene mutations are an important cause of idiopathic RCM in childhood. We describe the first mutation in ACTC in familial RCM. The identification of RCM in a child should prompt consideration of sarcomere protein disease as a possible cause and warrants clinical evaluation of the family.

Cardiological assessment of first-degree relatives in sudden arrhythmic death syndrome

4.1% of sudden cardiac deaths in the 16-64 age-group are unexplained. In this group, cardiac pathological findings are normal and toxicological tests are negative; termed sudden arrhythmic death syndrome (SADS). We searched for evidence of inherited cardiac disease in cases of SADS. Of 147 first-degree relatives of 32 people who died of SADS, 109 (74%) underwent cardiological assessment. Seven (22%) of the 32 families were diagnosed with inherited cardiac disease: four with long QT syndrome; one with non-structural cardiac electrophysiological disease; one with myotonic dystrophy; and one with hypertrophic cardiomyopathy. Families of people who die of SADS should be offered assessment in centres with experience of inherited cardiac disease.

A connexin 26 mutation causes a syndrome of sensorineural hearing loss and palmoplantar hyperkeratosis (MIM 148350)

We report a missense mutation in the connexin 26 gene (GJB2) in a family with an autosomal dominant syndrome of hearing loss and hyperkeratosis. The affected family members have high frequency, slowly progressive, bilateral, sensorineural hearing loss and palmoplantar hyperkeratosis. The mutation causes an amino acid substitution (G59A), which may disrupt a reverse turn in the first extracellular loop of connexin 26. Connexin 26 mutations have been reported in syndromes of deafness and palmoplantar keratoderma. These data provide additional evidence for the role of connexin 26 in syndromes of this type.

Novel nonsense mutation of the endothelin-B receptor gene in a family with Waardenburg-Hirschsprung disease

Waardenburg syndrome (WS) comprises sensorineural hearing loss, hypopigmentation of skin and hair, and pigmentary disturbances of the irides. Four types of WS have been classified to date; in WS type IV (WS4), patients additionally have colonic aganglionosis (Hirschsprung disease, HSCR). Mutations in the endothelin-3 (EDN3), endothelin-B receptor (EDNRB), and Sox10 genes have been identified as causative for WS type IV. We screened a family with a combined WS-HSCR phenotype for mutations in the EDNRB locus using standard DNA mutation analysis and sequencing techniques. We have identified a novel nonsense mutation at codon 253 (CGA-->TGA, Arg-->STOP). This mutation leads to a premature end of the translation of EDNRB at exon 3, and it is predicted to produce a truncated and nonfunctional endothelin-B receptor. All affected relatives were heterozygous for the Arg(253)-->STOP mutation, whereas it was not observed in over 50 unrelated individuals used as controls. These data confirm the role of EDNRB in the cause of the Waardenburg-Hirschsprung syndrome and demonstrate that in WS-HSCR there is a lack of correlation between phenotype and genotype and a variable expression of disease even within the same family.

Splicing mutations in KCNQ1: a mutation hot spot at codon 344 that produces in frame transcripts

BACKGROUND

Long-QT syndrome is a monogenic disorder that produces cardiac arrhythmias and can lead to sudden death. At least 5 loci and 4 known genes exist in which mutations have been shown to be responsible for the disease. The potassium channel gene KCNQ1, previously named KVLQT1, on chromosome 11p15.5 is one of these.

METHODS AND RESULTS

We initially analyzed one family using microsatellite markers and found linkage to KCNQ1. Mutation detection showed a G to C change in the last base of exon 6 (1032 G-->C) that does not alter the coded alanine. Restriction digest analysis in the family showed that only affected individuals carried the mutation. A previous report suggested that a G to A substitution at the same position may act as a splice mutation in KCNQ1, but no data was given to support this hypothesis nor was the transcription product identified. We have shown by reverse-transcription polymerase chain reaction that 2 smaller bands were produced for the KCNQ1 gene transcripts in addition to the normal-sized transcripts when lymphocytes of affected individuals were analyzed. Sequencing these transcripts showed a loss of exon 7 in one and exons 6 and 7 in the other, but an in-frame transcript was left in each instance. We examined other families in whom long-QT syndrome was diagnosed and found another unreported splice-site mutation, 922-1 G-->C, in the acceptor site of intron 5, and 2 of the previously reported 1032 G-->A mutations. All these showed a loss of exons 6 and 7 in the mutant transcripts, validating the proposal that a consensus sequence is affected in the exonic mutations and that the integrity of the base at position 1032 is essential for correct processing of the transcript.

CONCLUSIONS

The 6 cases already reported in the literature with the 1032 G-->A transition, the novel 1032 G-->C transversion, and a recent G-->T transversion at the same base show that codon 344 is the second most frequently mutated after codon 341, suggesting at least two hotspots for mutations in KCNQ1.

Lack of c-kit mutation in familial urticaria pigmentosa

Somatic mutations within c-kit have been reported in individuals with mastocytoses, including urticaria pigmentosa (UP). We have identified three siblings with UP. We aimed to determine whether the c-kit proto-oncogene was playing a part in the aetiology of UP in these three siblings. Using seven microsatellite repeat markers spanning an 8-cM interval encompassing the c-kit gene we followed the transmission of the c-kit gene in this family. Furthermore, single-strand conformation polymorphism analysis was used to scan exon 17 of the c-kit gene for mutations in genomic DNA of all family members and somatic DNA extracted from skin of the eldest affected sibling, the proband. No mutations were found in exon 17 in either genomic DNA of all family members or somatic DNA of the proband. Patients with UP have been shown to possess somatic mutations of the c-kit gene. However, this locus has been excluded as playing a part in the three siblings examined here in whom a second gene locus must be determining their UP. Therefore, this study emphasizes genetic heterogeneity in UP. Future study to identify primary molecular determinants of UP should include affected sib-pair studies.

Interleukin-1 receptor antagonist gene polymorphism and coronary artery disease

BACKGROUND

Cytokine gene variations are contributory factors in inflammatory pathology. Allele frequencies of interleukin (IL)-1 cluster genes [IL-1A(-889), IL-1B(-511), IL-1B(+3953), IL-1RN Intron 2 VNTR] and tissue necrosis factor (TNF)-alpha gene [TNFA(-308)] were measured in healthy blood donors (healthy control subjects), patients with angiographically normal coronary arteries (patient control subjects), single-vessel coronary disease (SVD), and those with multivessel coronary disease (MVD).

METHODS AND RESULTS

Five hundred fifty-six patients attending for coronary angiography in Sheffield were studied: 130 patient control subjects, 98 SVD, and 328 MVD. Significant associations were tested in an independent population (London) of 350: 57 SVD, 191 MVD, and 102 control subjects. IL-1RN*2 frequency in Sheffield patient control subjects was the same as in 827 healthy control subjects. IL-1RN*2 was significantly overrepresented in Sheffield SVD patients (34% vs 23% in patient control subjects); IL-1RN*2 homozygotes in the SVD population (chi2 carriage=8.490, 1 df, P=0.0036). This effect was present though not quite significant in the London population (P=0. 0603). A summary trend test of the IL-1RN SVD genotype data for Sheffield and London showed a significant association with *2 (P=0. 0024). No significant effect of genotype at IL-1RN was observed in the Sheffield or London MVD populations. Genotype distribution analysis comparing the SVD and MVD populations at IL-1RN showed a highly significant trend (P=0.0007) with the use of pooled data. No significant associations were seen for the other polymorphisms.

CONCLUSIONS

IL-1RN*2 was significantly associated with SVD. A difference in genetic association between SVD and MVD was also apparent.

Transforming growth factor-beta1 gene polymorphisms and coronary artery disease

1. Transforming growth factor-beta1 is a cytokine with a very wide spectrum of biological activities. Previous studies have shown that it is involved in a number of physiological and pathological processes including heart disease. In our study we aimed to scan the transforming growth factor-beta1 locus for polymorphisms and to identify haplotypes significantly associated with a predisposition to coronary atherosclerosis.2. Two patient groups comprising 244 angiographically normal individuals and 655 patients with coronary artery disease were recruited from London and Sheffield. DNA samples from these subjects were screened for mutations in the transforming growth factor-beta1 locus and all subjects were genotyped by a coupled polymerase chain reaction-restriction enzyme digestion method.3. Five polymorphisms have been identified in the transforming growth factor-beta1 gene at positions G-800A, C-509T in the promoter region, Leu10-->Pro, Arg25-->Pro in exon 1 and Thr263-->Ile in exon 5. No significant difference in frequencies for any of the five polymorphisms was found between controls and patients with coronary artery disease. Similarly, there was no correlation between these polymorphisms and hypertension.4. The genotypes of all the individuals participating in the study were assigned to seven main haplotypes of the transforming growth factor-beta1 locus. Based on species comparison data we propose that GCCGC is the ancestral haplotype in humans.5. Our data suggest that these transforming growth factor-beta1 polymorphisms are not associated with coronary artery disease and therefore their presence alone would not be a genetic risk factor for predisposition to coronary artery disease.

Methylenetetrahydrofolate reductase polymorphism (C-677T) and coronary artery disease

1. Many studies have shown that hyperhomocysteinaemia is a risk factor for atherosclerotic vascular disease. A mutation (C-677T) in the gene coding for the methylenetetrahydrofolate reductase (MTHFR) enzyme has been shown to produce a thermolabile form of the enzyme. Homozygosity for this mutation has been correlated with an elevated plasma homocysteine concentration. The present study aimed to determine whether this mutation was a risk factor for coronary artery disease (CAD). This was achieved by comparing the frequency of the C-677T mutation in patients with angiographically proven CAD against angiographically normal patients in two separate U.K. samples. The analysis was repeated with CAD patients split into those with >=99% stenosis of arteries and those without, to establish whether the C-677T mutation could be correlated with severity of CAD.2. Two patient groups were selected from London and Sheffield. The London group comprised 174 cases and 148 controls. The Sheffield group comprised 93 cases and 85 controls. The DNA samples of the patients were genotyped by polymerase chain reaction and restriction enzyme digestion.3. For London the homozygous C-677T frequencies were: 0.07 (controls), 0.09 (CAD without >=99% stenosis) and 0.10 (CAD with >=99% stenosis). For Sheffield the homozygous C-677T frequencies were: 0.08 (controls), 0.10 (CAD without >=99% stenosis) and 0.11 (CAD with >=99% stenosis). No association was found between the C-677T mutation and CAD in our sample geographical groups. Statistical comparison by genotype distribution for 0 VD (no vessel disease, i.e. 0% diameter reduction in all epicardial arteries) versus CAD without >=99% stenosis: London, P=0.19; Sheffield, P=0.53; 0 VD versus CAD with >=99% stenosis: London, P=0. 23; Sheffield, P=0.55.

Non-enzymatic glycosylation of the dipeptide L-carnosine, a potential anti-protein-cross-linking agent

The dipeptide carnosine (beta-alanyl-L-histidine) was readily glycosylated non-enzymatically upon incubation with the sugars glucose, galactose, deoxyribose and the triose dihydroxyacetone. Carnosine inhibited glycation of actyl-Lys-His-amide by dihydroxyacetone and it protected alpha-crystallin, superoxide dismutase and catalise against glycation and cross-linking mediated by ribose, deoxyribose, dihydroxyacetone, dihydroxyacetone phosphate and fructose. Unlike certain glycated amino acids, glycated carnosine was non-mutagenic. The potential biological and therapeutic significance of these observations are discussed.