Hypertrophic cardiomyopathy (HCM), the most common cause of sudden death in the young, is an autosomal dominant disease characterized by ventricular hypertrophy accompanied by myofibrillar disarrays. Linkage studies and candidate-gene approaches have demonstrated that about half of the patients have mutations in one of six disease genes: cardiac beta-myosin heavy chain (c beta MHC), cardiac troponin T (cTnT), alpha-tropomyosin (alpha TM), cardiac myosin binding protein C (cMBPC), ventricular myosin essential light chain (vMLC1) and ventricular myosin regulatory light chain (vMLC2) genes. Other disease genes remain unknown. Because all the known disease genes encode major contractile elements in cardiac muscle, we have systematically characterized the cardiac sarcomere genes, including cardiac troponin I (cTnI), cardiac actin (cACT) and cardiac troponin C (cTnC) in 184 unrelated patients with HCM and found mutations in the cTnI gene in several patients. Family studies showed that an Arg145Gly mutation was linked to HCM and a Lys206Gln mutation had occurred de novo, thus strongly suggesting that cTnI is the seventh HCM gene.

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Hypertrophic cardiomyopathy and dilated cardiomyopathy are two major clinical phenotypes of "idiopathic" cardiomyopathy. Recent molecular genetic analyses have now revealed that "idiopathic" cardiomyopathy is caused by mutations in genes for sarcomere components. We have recently reported several mutations in titin/connectin gene found in patients with hypertrophic cardiomyopathy or dilated cardiomyopathy. A hypertrophic cardiomyopathy-associated titin/connectin mutation (Arg740Leu) was found to increase the binding to actinin, while other dilated cardiomyopathy-associated titin/connectin mutations (Ala743Val and Val54Met) decreased the binding to actinin and Tcap/telethonin, respectively. We also reported several other mutations in the N2-B region of titin/connectin found in hypertrophic cardiomyopathy and dilated cardiomyopathy. Since the N2-B region expresses only in the heart, it was speculated that functional alterations due to the mutations cause cardiomyopathies. In this study, we investigated the functional changes caused by the N2-B region mutations by using yeast-two-hybrid assays. It was revealed that a hypertrophic cardiomyopathy-associated mutation (Ser3799Tyr) increased the binding to FHL2 protein, whereas a dilated cardiomyopathy-associated mutation (Gln4053ter) decreased the binding. In addition, another TTN mutation (Arg25618Gln) at the is2 region was found in familial DCM. Because FHL2 protein is known to tether metabolic enzymes to N2-B and is2 regions of titin/connectin, these observations suggest that altered recruitment of metabolic enzymes to the sarcomere may play a role in the pathogenesis of cardiomyopathies.

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Idiopathic dilated cardiomyopathy (IDC) is characterized by a thin-walled heart with systolic dysfunction of unknown etiology. Because abnormalities in genes for cytoskeletal proteins related to Z-disc function have recently been reported to cause IDC, genomic organization of the gene for nebulette, a novel actin-binding Z-disc protein, was determined and its sequence variations were searched for in Japanese patients with IDC and healthy controls. The nebulette gene consists of 28 exons, and four sequence variations leading to amino acid replacement (Gln187His, Met351Val, Asn654Lys, and Thr728Ala) were identified in the patients. These variations were also found in the healthy controls and hence they were polymorphisms and not disease-specific mutations. Frequencies of Gln187His, Met351Val, and Thr728Ala variants were similar in the patients and controls. However, the frequency of homozygotes for Lys at codon 654, a variant at a relatively conserved residue in an actinbinding motif, was significantly increased in nonfamilial IDC patients (n=106) as compared with healthy control subjects (n=331) (7.54% vs 1.21%, OR=6.25, P=0.002, 95% CI=1.92-20.29), while this association was not found in familial IDC patients (n=24). These observations suggest that the nebulette polymorphism in the actin-binding motif was a novel genetic marker of susceptibility to nonfamilial IDC.

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IMPORTANCE Sodium glucose cotransporter 2 inhibitors reduce morbidity and mortality in patients with heart failure and reduced ejection fraction (HFrEF). Clinicians may find estimates of the projected long-term benefits of sodium glucose cotransporter 2 inhibitors a helpful addition to clinical trial results when communicating the benefits of this class of drug to patients. OBJECTIVE To estimate the projected long-term treatment effects of dapagliflozin in patients with HFrEF over the duration of a patient's lifetime.DESIGN, SETTING, AND PARTICIPANTS Exploratory analysis was performed of Dapagliflozin and Prevention of Adverse Outcomes in Heart Failure (DAPA-HF), a phase 3 randomized, placebo-controlled clinical trial conducted at 410 sites in 20 countries. Patients with an ejection fraction less than or equal to 40% in New York Heart Association functional classification II to IV and elevated plasma levels of N-terminal pro B-type natriuretic peptide were enrolled between February 15, 2017, and August 17, 2018, with final follow-up on June 6, 2019. Mean (SD) duration of follow-up was 17.6 (5.2) months.INTERVENTIONS Dapagliflozin, 10 mg, once daily vs placebo in addition to standard therapy. MAIN OUTCOMES AND MEASURESThe primary composite outcome was time to first hospitalization for heart failure, urgent heart failure visit requiring intravenous therapy, or cardiovascular death. The trial results were extrapolated to estimate the projected long-term treatment effects of dapagliflozin over the duration of a patient's lifetime for the primary outcome and the secondary outcome of death from any cause.RESULTS A total of 4744 patients (1109 women [23.4%]; 3635 men [76.6%]) were randomized in DAPA-HF, with a mean (SD) age of 66.3 (10.9) years. The extrapolated mean event-free survival for an individual aged 65 years from a primary composite end point event was 6.2 years for placebo and 8.3 years for dapagliflozin, representing an event-free survival time gain of 2.1 years (95% CI, 0.8-3.3 years; P = .002). When considering death from any cause, mean extrapolated life expectancy for an individual aged 65 years was 9.1 years for placebo and 10.8 years for dapagliflozin, with a gain in survival of 1.7 years (95% CI, 0.1-3.3; P = .03) with dapagliflozin. Similar results were seen when extrapolated across the age range studied. In analyses of subgroups of patients in DAPA-HF, consistent benefits were seen with dapagliflozin on both event-free and overall survival. CONCLUSIONS AND RELEVANCEThese findings indicate that dapagliflozin provides clinically meaningful gains in extrapolated event-free and overall survival. These findings may be helpful in communicating the benefits of this treatment to patients with HFrEF.TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT03036124

Objective: To determine whether the benefits of dapagliflozin in patients with heart failure and reduced ejection fraction (HFrEF) and type 2 diabetes in DAPA-HF varied by background glucose-lowering therapy (GLT). Research design and methods: We examined the effect of study treatment by the use or not of GLT, and by GLT classes and combinations. The primary outcome was a composite of worsening HF (hospitalization or urgent visit requiring intravenous therapy) or cardiovascular death. Results: In the 2139 type 2 diabetes patients, the effect of dapagliflozin on the primary outcome was consistent by GLT use/no use (hazard ratio 0.72 [95%CI 0.58-0.88] versus 0.86 [0.60-1.23]; P-interaction=0.39) and across GLT classes. Conclusions: In DAPA-HF, dapagliflozin improved outcomes irrespective of use/no use of GLT or by GLT type used in patients with type 2 diabetes and HFrEF.