Mechanical and energetic consequences of HCM-causing mutations

Area of Science:

• Cardiovascular Genetics
• Molecular Cardiology
• Inherited Cardiac Diseases

Background:

• Hypertrophic cardiomyopathy (HCM) is the first inherited heart disease linked to cardiac sarcomere gene mutations.
• Early research suggested HCM mutations impair sarcomere mechanical function, leading to compensatory hypertrophy.
• Recent studies propose HCM mutations enhance contractility and myofilament calcium sensitivity, while impairing cardiac myocyte energetics.

Purpose of the Study:

• To explore the conflicting conclusions regarding the functional effects of HCM mutations.
• To investigate the hypothesis that HCM mutations lead to cardiac myocyte energy depletion and altered calcium handling.
• To discuss challenges in studying HCM at the human sarcomere level and identify therapeutic targets.

Main Methods:

• Review of in vitro and mouse model studies on HCM mutations.
• Analysis of functional characteristics of human cardiac sarcomeres in HCM.
• Mechanically isolated skinned myocytes and myofibrils from human hearts.

Main Results:

• Conflicting evidence exists regarding HCM mutation effects on sarcomere function.
• Recent human myocyte studies support the energy depletion hypothesis.
• HCM mutations may enhance contractility and calcium sensitivity while impairing energetics.

Conclusions:

• The energy depletion hypothesis offers a unified explanation for HCM pathogenesis.
• This hypothesis identifies potential therapeutic targets for disease-modifying therapies in HCM.
• HCM may be particularly amenable to targeted interventions based on energy metabolism.