Why do axons go downhill? Gravity has nothing to do with it…
The linked study, though not specifically aimed at ALS, does seem to tie together a few “hot topics” in the pathology: axonopathy, oxidative damage, and mitochondrial dysfunction. With many plausible theories of damage, trying to link some together may provide more clues as to cause and/or (more importantly) ways to effectively treat the disease. Part of the tie to ALS in this study is the fact that mice bred to lack the SOD1 gene exhibit a similar disease process as mice bred with a copy of the malformed SOD1 gene which is a known cause of familial ALS. Reinserting the gene in the “knockout” mice, but only in the mitochondria, rescued the mice from disease.
Mitochondria are the power plants of the cells and as a consequence also produce molecules which can cause cellular damage (ROS, the “industrial waste” of cellular energy production). Anything which disrupts the ability to clear out this waste can cause damage to the cell. Damage to mitochondria impacts their ability to provide energy to the cell. Motor neurons have high energy requirements and due to their extremely long axons have mitochondria operating at large distance from the cell body. There are currently a few clinical trials going into Phase III aimed at mitochondrial support.
While the study doesn’t provide an answer (except that this problem is “way beyond eating blueberries”), it does provide some important clues for further investigation.