Liver failure to clear lactate drives muscle loss in aging
Age-related muscle loss is usually blamed on inactivity or poor diet. But a new study points to a different culprit: a disrupted exchange between the liver and muscles involving lactate, the byproduct of physical effort. And the liver is more central to the story than expected.
Sarcopenia, the medical term for severe age-related loss of muscle mass and strength, affects large numbers of older adults and is strongly linked to falls, reduced mobility, and higher mortality. Its causes have been debated for years. A new study published in Science Advances adds a mechanism that has received little attention: impaired lactate metabolism in the liver.
The researchers found that in aging mice, the liver loses its capacity to clear lactate produced during physical activity. That lactate accumulates in muscle tissue, causing cellular acidification (lactic acidosis). This acidification disrupts normal muscle cell function, contributing to the weakness and mass loss that define sarcopenia.
The liver as an unexpected key organ
Most sarcopenia research focuses on what goes wrong inside muscle cells themselves. The distinctive claim here is that the liver, by failing to process lactate efficiently as it ages, indirectly damages skeletal muscle. The study also found that a decline in NAD+ levels, a molecule essential for cellular energy production, plays a role in the muscle dysfunction triggered by lactic acidosis.
When the researchers experimentally activated the protein HIF1α specifically in the livers of aging mice, lactate clearance improved and muscle damage was reduced. Whether this translates to humans is unknown. The entire study was conducted in mouse models.
A new angle on prevention and treatment
If the liver is indeed a central link in age-related muscle loss, targeting liver metabolism could become a therapeutic strategy for sarcopenia. That would be a departure from most current approaches, which focus on the muscle directly. These remain preliminary findings in animal models, and the authors are careful to frame them as a new mechanistic hypothesis rather than a clinical conclusion. Still, the pathway identified, from liver lactate clearance to muscle acidification to NAD+ depletion, is specific enough to make this a study worth following up.
Search terms to explore further: lactic acidosis skeletal muscle aging, liver-muscle metabolic axis sarcopenia, HIF1alpha lactate clearance aging