• Mitochondrial myopathy patients have NAD⁺ deficiency in muscle and blood
• Niacin (or Vitamin B3) is an efficient NAD⁺ booster in humans
• Niacin (or Vitamin B3) improves muscle strength and fatty liver in mitochondrial myopathy
• Niacin (or Vitamin B3) boosts muscle mitochondrial biogenesis and respiratory chain activity in humans

Here, we report systemic NAD⁺ deficiency in adult-onset mitochondrial myopathy patients. We administered an increasing dose of NAD⁺-booster niacin, a vitamin B3 form (to 750–1,000 mg/day; for patients and their matched controls for 10 or 4 months, respectively. Blood NAD⁺ increased in all subjects, up to 8-fold, and muscle NAD⁺ of patients reached the level of their controls. Some patients showed anemia tendency, while muscle strength and mitochondrial biogenesis increased in all subjects. In patients, muscle metabolome shifted toward controls and liver fat decreased even 50%. Our evidence indicates that blood analysis is useful in identifying NAD⁺ deficiency and points to niacin to be an efficient NAD⁺ booster for treating mitochondrial myopathy.

Niacin Cures Systemic NAD⁺ Deficiency and Improves Muscle Performance in Adult-Onset Mitochondrial Myopathy