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BIOPHYSICAL CHARACTERIZATION OF FAMILIAL HYPERTROPHIC CARDIOMYOPATHY-RELATED TROPONIN T MUTATIONS
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Canadian Journal of Cardiology Volume 30 2014
and more likely to be in the highest 30-year risk category (OR ¼ 1.5, 95% CI [1.2, 1.7]) for CVD compared to people not reporting psychoactive medication use. Negligible confounding was found between the effects of psychoactive medication use and having a MHD on heart health. CONCLUSION: Canadians with MHDs are more likely to suffer from cardiovascular disease than Canadians without MHDs. Further investigation into the etiology behind these associations are needed. Healthcare providers can improve the cardiovascular health of their patients by being vigilant in conducting routine cardiovascular risk assessments, before and after initiating psychopharmacological treatment, in addition to offering health promotion interventions to target known cardiovascular risk factors. CIHR 129 UTILIZING THE CANADIAN COMMUNITY HEALTH SURVEY TO INVESTIGATE CARDIOVASCULAR RISK AND DISEASE AMONG PEOPLE WITH MENTAL HEALTH DISORDERS CL Goldie, JL Johnson, PA Ratner, V Smye
Canadian Cardiovascular Society (CCS) Oral CARDIOMYOPATHIES Saturday, October 25, 2014
Toronto, Ontario BACKGROUND:
Previous research has demonstrated that cardiovascular morbidity is elevated among persons with mental health disorders (MHDs) compared to people without MHDs; however, there is no reliable estimate of the burden of disease across Canada. A thorough examination of cardiovascular disease (CVD) among Canadians with MHDs is needed, not only to contribute findings to the international dialogue, but also to estimate the magnitude of this heath disparity and inform approaches to prevention and treatment. METHODS: Cross-sectional data obtained via the Canadian Community Health Survey Cycle 1.2 was used to examine the associations between MHDs, psychoactive medication use, the presence of heart disease and stroke, and projections of cardiovascular risk. Demographic characteristics of respondents with single and comorbid MHDs were characterized with proportions and bivariate odds ratios (ORs). Descriptive statistics were used to measure the prevalence of heart disease and stroke among respondents with MHDs or taking psychoactive medications before unadjusted and demographically-adjusted associations described. Cardiovascular risk estimates were then dichotomized at the median to estimate the strength of their relationship with MHDs and psychoactive medication use. Confidence intervals were calculated using weighted bootstrapped estimates. RESULTS: Respondents with any lifetime MHD were twice as likely to have had heart disease (OR ¼ 2.0, 95% CI [1.8, 2.2]) or stroke (OR ¼ 2.3, 95% CI [1.7, 3.0]) compared with people without any MHDs. Those without heart disease or stroke were more likely to be at high risk of developing CVD within 30-years compared to people without a MHD (OR ¼ 1.2, 95% CI [1.1, 1.4]). Similarly, people reporting psychoactive medication use were twice as likely to have heart disease (OR ¼ 2.4, 95% CI [2.1, 2.8]), three times as likely to report having had a stroke (OR¼ 2.8, (95% CI [2.3, 3.4]),
130 BIOPHYSICAL CHARACTERIZATION OF FAMILIAL HYPERTROPHIC CARDIOMYOPATHY-RELATED TROPONIN T MUTATIONS AY Li, B Liang, G Tibbits Burnaby, British Columbia BACKGROUND:
Cardiac troponin (cTn) is a three-subunit complex that plays an essential role in cardiac contractility. Each cTn complex is comprised of a highly conserved Ca2+ binding subunit (cTnC), an inhibitory subunit (cTnI), and a tropomyosin binding subunit (cTnT). Mutations within each subunit cause changes in both contraction and relaxation of the heart, potentially leading to devastating consequences[1]. Familial hypertrophic cardiomyopathy (FHC) is one of the most common inherited cardiac muscle disorders. FHC results in an symmetrical enlargement of the left ventricular wall and cardiac dysfunction [2]. Sixty-nine of the FHC mutations discovered thus far involve the cTn complex [2]. The proposed study will focus on three cTnT mutations (R278C, F110I, and I79N) that have been shown to induce a different degree of cardiomyopathy, producing a mild, moderate or severe FHC phenotype, respectively[3]. Elucidation of the molecular and functional properties of these mutants will allow us to have a clearer understanding of the mechanism of the pathogenesis of FHC and provide an important basis for rational drug design for patients suffering with FHC. METHOD AND RESULTS: The biophysical properties of the human cTnT mutants were investigated in the reconstituted thin filaments (RTF) containing purified human cTn, actin, and tropomyosin. Fluorometry was used to measure the Ca2+ affinity of cTnC of each sample. A fluorescent probe that causes minimal structural modifications to the highly conserved TnC and emits with high quantum efficiency was introduced in cTnC at residue 27. Each RTF containing the mutant cTnT demonstrated a measurable change in the
Abstracts
S121
Ca2+ binding affinity of TnC. Functional characterization was performed on a whole cell level, in which the native cTn were exchanged with the recombinant cTn containing cTnT mutants in an isolated skinned cardiomyocyte. Changes in the Ca2+ sensitivity of cardiomyocytes due to the presence of the cTnT mutations was also observed in our preliminary data. CONCLUSION: Our preliminary results demonstrate observable changes in Ca2+ binding affinity in the reconstituted thin filament as well as the Ca2+ sensitivity in cardiomyocytes in the presence of the cTnT mutants. This suggests that the changes in Ca2+ binding kinetics of cTnC due to these mutations may be the underlying mechanism of the pathological remodeling of the myocardium in those FHC patients. CIHR
been over-expressed in multiple striated muscle cell lines to determine localization and stability of mutant proteins. Immunocytochemistry demonstrated that NEXN p.E562del displayed actin co-localization indistinguishable from that observed in wild type, whereas NEXN p.C667Y formed aggregates throughout the cell cytoplasm, indicating protein disruption and loss of filament integrity. Ongoing in vivo experiments in zebrafish will further determine pathological effects of mutant NEXN proteins on heart development and physiology. CONCLUSION: Here we discovered and validated a novel NEXN variant p.C667Y causing a new LVNC phenotype not previously described. Despite co-segregation the variant p.E562del remains a VUS, but appears to be likely non-pathogenic.
131 NOVEL NEXILIN VARIANTS MAY CAUSE DIFFERENT INHERITED CARDIOMYOPATHIES
132 ANTI-INFLAMMATORY TREATMENT WITH CETIRIZINE IMPROVES REFRACTORY HEART FAILURE IN PATIENTS WITH HEPATITIS C VIRUS- INDUCED MYOCARDITIS
T Yuen, K Borle, V French, A Brodehl, J Lauzon, P Sharma, R Ferrier, D Exner, B Gerull
MA Haykal
Calgary, Alberta
Cairo, Egypt
INTRODUCTION:
BACKGROUND:
Inherited cardiomyopathies are mainly autosomal dominant conditions characterized by variable disease expression and genetic heterogeneity. Mutations in genes coding for cardiac contractile proteins have been implicated as causative for multiple cardiomyopathies, including dilated cardiomyopathy (DCM) and left ventricular noncompaction (LVNC). DCM is characterized by enlarged heart chambers and decreased cardiac efficiency. LVNC, a developmental condition, results in spongy heart tissue with deep recesses in the muscle wall. Advances in molecular diagnostics using Next-Generation Sequencing (NGS) have uncovered an increasing number of genetic variants of uncertain significance (VUS). We report 2 novel VUS in nexilin (NEXN), identified through NGS. Nexilin, a Z-disc protein that binds F-actin, is crucial for maintaining cardiomyocyte integrity and function. Both NEXN variants affect highly conserved amino acids and are predicted to disrupt the protein. Here we report validation experiments to determine the pathogenicity of these NEXN VUS. METHODS & RESULTS: NEXN variant p.E562del was found in a family with 4 living and 2 deceased members with DCM and complete heart block. All required pacemakers in their 30s. The proband has survived a ventricular fibrillation arrest. NGS further identified RBM20 variant p.S268DfsX3 in the proband. However, the RBM20 variant did not segregate, whereas the NEXN variant co-segregated in all clinically affected members. The proband in our second family was diagnosed with LVNC in utero after presenting with poor LV contractility and an EF of 31%. Family screening also identified signs of LVNC in his 30-year old father and his 4-year-old sister. NGS identified NEXN variant p.C667Y in all three affected individuals. Both novel variants and NEXN wild type have
Hepatitis C virus (HCV) causes cardiomyopathy as a complication of HCV myocarditis. This may be due to an inflammatory response, which induces growth or death of cardiac cells. HCV may directly induce cardiomyopathy, via viral products that lead to cardiomyopathy through perturbation of the cardiac cells. Cetirizine is an antihistamine shown to block expression of inflammatory cytokines and metalloproteinases that play important roles in cardiac remodeling in viral myocarditis. OBJECTIVE: To assess the effect of cetirizine on myocardial function in patients with HCV cardiomyopathy. METHODS: Twenty patients with HCV and systolic dysfunction on optimal anti-heart failure therapy were randomly selected to participate in this single-center, single-arm study. Eleven patients with coronary artery disease on angiography were excluded; nine patients with refractory heart failure and normal coronary angiography were treated with cetirizine 10 mg once daily. Patients underwent evaluation with ECG, echocardiography, speckle tracking echocardiography, and NT-Pro BNP at baseline and at 3 months. RESULTS: Myocardial function was substantially improved in all study patients. Specifically, there was a significant decrease in left ventricular (LV) average global strain (P¼0.009), in QTc interval (P¼0.005), left atrial diameter (P<0.001), and LV end systolic diameter (LVESd) (P<0.005), and a significant increase in LV ejection fraction (LVEF) (P<0.01). LV wall thickness and LV mass were improved. CONCLUSION: Cetirizine is a new treatment for refractory heart failure in patients with HCV cardiomyopathy that can be considered as bridge therapy to improve myocardial function so that interferon-ribavirin eradication therapy for HCV can be undertaken.
Canadian Journal of Cardiology Volume 30 2014
and more likely to be in the highest 30-year risk category (OR ¼ 1.5, 95% CI [1.2, 1.7]) for CVD compared to people not reporting psychoactive medication use. Negligible confounding was found between the effects of psychoactive medication use and having a MHD on heart health. CONCLUSION: Canadians with MHDs are more likely to suffer from cardiovascular disease than Canadians without MHDs. Further investigation into the etiology behind these associations are needed. Healthcare providers can improve the cardiovascular health of their patients by being vigilant in conducting routine cardiovascular risk assessments, before and after initiating psychopharmacological treatment, in addition to offering health promotion interventions to target known cardiovascular risk factors. CIHR 129 UTILIZING THE CANADIAN COMMUNITY HEALTH SURVEY TO INVESTIGATE CARDIOVASCULAR RISK AND DISEASE AMONG PEOPLE WITH MENTAL HEALTH DISORDERS CL Goldie, JL Johnson, PA Ratner, V Smye
Canadian Cardiovascular Society (CCS) Oral CARDIOMYOPATHIES Saturday, October 25, 2014
Toronto, Ontario BACKGROUND:
Previous research has demonstrated that cardiovascular morbidity is elevated among persons with mental health disorders (MHDs) compared to people without MHDs; however, there is no reliable estimate of the burden of disease across Canada. A thorough examination of cardiovascular disease (CVD) among Canadians with MHDs is needed, not only to contribute findings to the international dialogue, but also to estimate the magnitude of this heath disparity and inform approaches to prevention and treatment. METHODS: Cross-sectional data obtained via the Canadian Community Health Survey Cycle 1.2 was used to examine the associations between MHDs, psychoactive medication use, the presence of heart disease and stroke, and projections of cardiovascular risk. Demographic characteristics of respondents with single and comorbid MHDs were characterized with proportions and bivariate odds ratios (ORs). Descriptive statistics were used to measure the prevalence of heart disease and stroke among respondents with MHDs or taking psychoactive medications before unadjusted and demographically-adjusted associations described. Cardiovascular risk estimates were then dichotomized at the median to estimate the strength of their relationship with MHDs and psychoactive medication use. Confidence intervals were calculated using weighted bootstrapped estimates. RESULTS: Respondents with any lifetime MHD were twice as likely to have had heart disease (OR ¼ 2.0, 95% CI [1.8, 2.2]) or stroke (OR ¼ 2.3, 95% CI [1.7, 3.0]) compared with people without any MHDs. Those without heart disease or stroke were more likely to be at high risk of developing CVD within 30-years compared to people without a MHD (OR ¼ 1.2, 95% CI [1.1, 1.4]). Similarly, people reporting psychoactive medication use were twice as likely to have heart disease (OR ¼ 2.4, 95% CI [2.1, 2.8]), three times as likely to report having had a stroke (OR¼ 2.8, (95% CI [2.3, 3.4]),
130 BIOPHYSICAL CHARACTERIZATION OF FAMILIAL HYPERTROPHIC CARDIOMYOPATHY-RELATED TROPONIN T MUTATIONS AY Li, B Liang, G Tibbits Burnaby, British Columbia BACKGROUND:
Cardiac troponin (cTn) is a three-subunit complex that plays an essential role in cardiac contractility. Each cTn complex is comprised of a highly conserved Ca2+ binding subunit (cTnC), an inhibitory subunit (cTnI), and a tropomyosin binding subunit (cTnT). Mutations within each subunit cause changes in both contraction and relaxation of the heart, potentially leading to devastating consequences[1]. Familial hypertrophic cardiomyopathy (FHC) is one of the most common inherited cardiac muscle disorders. FHC results in an symmetrical enlargement of the left ventricular wall and cardiac dysfunction [2]. Sixty-nine of the FHC mutations discovered thus far involve the cTn complex [2]. The proposed study will focus on three cTnT mutations (R278C, F110I, and I79N) that have been shown to induce a different degree of cardiomyopathy, producing a mild, moderate or severe FHC phenotype, respectively[3]. Elucidation of the molecular and functional properties of these mutants will allow us to have a clearer understanding of the mechanism of the pathogenesis of FHC and provide an important basis for rational drug design for patients suffering with FHC. METHOD AND RESULTS: The biophysical properties of the human cTnT mutants were investigated in the reconstituted thin filaments (RTF) containing purified human cTn, actin, and tropomyosin. Fluorometry was used to measure the Ca2+ affinity of cTnC of each sample. A fluorescent probe that causes minimal structural modifications to the highly conserved TnC and emits with high quantum efficiency was introduced in cTnC at residue 27. Each RTF containing the mutant cTnT demonstrated a measurable change in the
Abstracts
S121
Ca2+ binding affinity of TnC. Functional characterization was performed on a whole cell level, in which the native cTn were exchanged with the recombinant cTn containing cTnT mutants in an isolated skinned cardiomyocyte. Changes in the Ca2+ sensitivity of cardiomyocytes due to the presence of the cTnT mutations was also observed in our preliminary data. CONCLUSION: Our preliminary results demonstrate observable changes in Ca2+ binding affinity in the reconstituted thin filament as well as the Ca2+ sensitivity in cardiomyocytes in the presence of the cTnT mutants. This suggests that the changes in Ca2+ binding kinetics of cTnC due to these mutations may be the underlying mechanism of the pathological remodeling of the myocardium in those FHC patients. CIHR
been over-expressed in multiple striated muscle cell lines to determine localization and stability of mutant proteins. Immunocytochemistry demonstrated that NEXN p.E562del displayed actin co-localization indistinguishable from that observed in wild type, whereas NEXN p.C667Y formed aggregates throughout the cell cytoplasm, indicating protein disruption and loss of filament integrity. Ongoing in vivo experiments in zebrafish will further determine pathological effects of mutant NEXN proteins on heart development and physiology. CONCLUSION: Here we discovered and validated a novel NEXN variant p.C667Y causing a new LVNC phenotype not previously described. Despite co-segregation the variant p.E562del remains a VUS, but appears to be likely non-pathogenic.
131 NOVEL NEXILIN VARIANTS MAY CAUSE DIFFERENT INHERITED CARDIOMYOPATHIES
132 ANTI-INFLAMMATORY TREATMENT WITH CETIRIZINE IMPROVES REFRACTORY HEART FAILURE IN PATIENTS WITH HEPATITIS C VIRUS- INDUCED MYOCARDITIS
T Yuen, K Borle, V French, A Brodehl, J Lauzon, P Sharma, R Ferrier, D Exner, B Gerull
MA Haykal
Calgary, Alberta
Cairo, Egypt
INTRODUCTION:
BACKGROUND:
Inherited cardiomyopathies are mainly autosomal dominant conditions characterized by variable disease expression and genetic heterogeneity. Mutations in genes coding for cardiac contractile proteins have been implicated as causative for multiple cardiomyopathies, including dilated cardiomyopathy (DCM) and left ventricular noncompaction (LVNC). DCM is characterized by enlarged heart chambers and decreased cardiac efficiency. LVNC, a developmental condition, results in spongy heart tissue with deep recesses in the muscle wall. Advances in molecular diagnostics using Next-Generation Sequencing (NGS) have uncovered an increasing number of genetic variants of uncertain significance (VUS). We report 2 novel VUS in nexilin (NEXN), identified through NGS. Nexilin, a Z-disc protein that binds F-actin, is crucial for maintaining cardiomyocyte integrity and function. Both NEXN variants affect highly conserved amino acids and are predicted to disrupt the protein. Here we report validation experiments to determine the pathogenicity of these NEXN VUS. METHODS & RESULTS: NEXN variant p.E562del was found in a family with 4 living and 2 deceased members with DCM and complete heart block. All required pacemakers in their 30s. The proband has survived a ventricular fibrillation arrest. NGS further identified RBM20 variant p.S268DfsX3 in the proband. However, the RBM20 variant did not segregate, whereas the NEXN variant co-segregated in all clinically affected members. The proband in our second family was diagnosed with LVNC in utero after presenting with poor LV contractility and an EF of 31%. Family screening also identified signs of LVNC in his 30-year old father and his 4-year-old sister. NGS identified NEXN variant p.C667Y in all three affected individuals. Both novel variants and NEXN wild type have
Hepatitis C virus (HCV) causes cardiomyopathy as a complication of HCV myocarditis. This may be due to an inflammatory response, which induces growth or death of cardiac cells. HCV may directly induce cardiomyopathy, via viral products that lead to cardiomyopathy through perturbation of the cardiac cells. Cetirizine is an antihistamine shown to block expression of inflammatory cytokines and metalloproteinases that play important roles in cardiac remodeling in viral myocarditis. OBJECTIVE: To assess the effect of cetirizine on myocardial function in patients with HCV cardiomyopathy. METHODS: Twenty patients with HCV and systolic dysfunction on optimal anti-heart failure therapy were randomly selected to participate in this single-center, single-arm study. Eleven patients with coronary artery disease on angiography were excluded; nine patients with refractory heart failure and normal coronary angiography were treated with cetirizine 10 mg once daily. Patients underwent evaluation with ECG, echocardiography, speckle tracking echocardiography, and NT-Pro BNP at baseline and at 3 months. RESULTS: Myocardial function was substantially improved in all study patients. Specifically, there was a significant decrease in left ventricular (LV) average global strain (P¼0.009), in QTc interval (P¼0.005), left atrial diameter (P<0.001), and LV end systolic diameter (LVESd) (P<0.005), and a significant increase in LV ejection fraction (LVEF) (P<0.01). LV wall thickness and LV mass were improved. CONCLUSION: Cetirizine is a new treatment for refractory heart failure in patients with HCV cardiomyopathy that can be considered as bridge therapy to improve myocardial function so that interferon-ribavirin eradication therapy for HCV can be undertaken.