Impaired Liver-Muscle Lactate Metabolism Causes Sarcopenia via Muscle Acidosis

Sarcopenia—the loss of muscle mass and strength with aging—affects up to 15% of older adults and contributes to falls, frailty, and loss of independence. New research in Science Advances reveals a surprising metabolic culprit: impaired lactate metabolism between the liver and muscles. The study in mice shows that when the normal lactate shuttle between these organs breaks down, lactic acid accumulates in skeletal muscle tissue, directly causing sarcopenia. This challenges the traditional view of sarcopenia as primarily a problem of muscle protein synthesis and breakdown. Lactate, often dismissed as a waste product, actually serves as a crucial metabolic fuel and signaling molecule. The liver normally clears lactate from circulation and converts it to glucose, while muscles both produce and consume lactate depending on metabolic state. When this coordinated system fails, the resulting acidosis appears toxic to muscle tissue. This finding is promising because metabolic interventions—potentially including dietary modifications, exercise protocols, or drugs targeting lactate transporters—might prevent or reverse sarcopenia more effectively than current protein-focused approaches. The next critical step is confirming whether this mechanism operates similarly in aging humans.