Alterations of Fat and Ketone Body Metabolism in ALS and SMA-A Prospective Observational Study.

Amyotrophic lateral sclerdosis (ALS) and spinal muscular atrophy (SMA) are motor neuron diseases associated with distinct metabolic alterations. ALS patients feature an increased resting energy expenditure (REE) causing weight loss and cachexia. In SMA, a disturbed utilization of free fatty acids has been described. These metabolic alterations negatively affect prognosis in both diseases. The objective of this study was to further characterize these changes to identify potential therapeutic targets.Between 11/2020 and 08/2022, 112 ALS patients, 77 SMA patients, and 50 controls were recruited in the Department of Neurology of Ulm University. Standardized blood and urinary samples were collected to analyze fat and ketone metabolism.Ketone body levels were higher in ALS and SMA compared to controls. In both diseases, patients with higher BMI featured higher ketone bodies and free fatty acids compared to those with lower BMI, while in controls we found the opposite phenomenon. In SMA, more severe disease types were associated with higher ketone body levels. Compared to ALS, SMA patients featured higher ketone body and free fatty acid levels.Our data suggest that already during early disease stages, ALS patients produce ketone bodies to compensate for the energy deficit. In SMA, on the other hand, the persistence of ketogenesis may indicate an upregulation of all available metabolic pathways for energy production due to the disturbance of fatty acid utilization. Therefore, the application of additional sources of energy, such as ketone bodies, might constitute a promising therapeutic option in both diseases.