Association of carnitine insufficiency with sarcopenia and dynapenia in patients with heart failure

AIM: L-carnitine transports fatty acids into mitochondria and contributes to energy metabolism in skeletal muscles. However, the association between carnitine insufficiency and skeletal muscle weakness, namely sarcopenia and dynapenia, in patients with heart failure (HF) remains unclear. METHODS: In total, 124 patients with HF were enrolled in this study. Carnitine insufficiency was indicated by a decrease in serum free carnitine (FC) levels of less than 36 μmol/L or an elevated serum acylcarnitine (AC) to free carnitine (FC) ratio (AC/FC ratio) of 0.27 or higher. Skeletal muscle weakness was defined as reduced handgrip strength and classified into two phenotypes: sarcopenia (low muscle strength with low skeletal muscle mass) and dynapenia (low muscle strength with normal skeletal muscle mass). RESULTS: Patients with carnitine insufficiency had a significantly higher prevalence of muscle weakness and a lower 6-min walk distance than those without carnitine insufficiency (P < 0.05). A machine learning model showed that older age (≥77 years) and, in patients aged 64-76 years, a higher AC/FC ratio (≥0.31) were associated with sarcopenia. However, there was only a week association between carnitine levels and dynapenia. The effect of carnitine insufficiency on skeletal muscle weakness was greater in patients with low skeletal muscle mass than in those with normal skeletal muscle mass (P < 0.05 for interaction). CONCLUSIONS: Carnitine insufficiency is more closely associated with sarcopenia than with dynapenia in patients with HF, suggesting carnitine insufficiency as a potential therapeutic target for sarcopenia in these patients. Geriatr Gerontol Int 2023; 23: 524-530.