Possible Explanations
The authors hypothesized that the lower rate of amyloid pathology observed in their patients with MS may stem from the following possibly overlapping mechanisms:
- MS components, such as persistent perilesional immune activity, may inhibit amyloid beta deposition or facilitate its clearance.
- Exposure to MS drugs may impact Alzheimer’s disease pathology. Most study patients with MS were exposed to beta interferons or glatiramer acetate, the authors noted, and 39 had switched to high-efficacy medications such as B-cell depleting therapies and natalizumab.
- MS’s genetic signature may protect against AD.
“Investigating these ideas would advance our understanding of the relationship between MS and Alzheimer’s, and potentially inform avenues for treatment,” said Dr. Sexton. In this regard, the Alzheimer’s Association has funded an ongoing study examining a drug currently used to promote myelin formation in individuals with MS in genetically engineered Alzheimer’s-like mice. Additional Association-funded studies that examine inflammation also may improve understanding of the mechanisms that may link these diseases, said Dr. Sexton.
The study authors added that unusual cases, such as a study patient who had high amyloid burden by PET but negative APS2 and tau PET, also may shed light on interactions between MS, amyloid pathology, and tau pathology.
Limitations of the present study include the fact that plasma Alzheimer’s disease biomarkers are potentially affected by other conditions as well, according to a study published in Nature Medicine. Additional shortcomings include the MS cohort’s relatively small size and lack of diagnostic confirmation by cerebrospinal fluid. Although MMSE scores among patients with MS were slightly lower, the authors added, this disparity would lead one to expect more, not less, amyloid pathology among these patients if their cognitive impairment resulted from Alzheimer’s disease.
Dr. Sexton reported no relevant financial interests.
The study was supported by the Hope Center for Neurological Disorders at Washington University in St. Louis and by C2N Diagnostics. Washington University in St. Louis holds equity in C2N Diagnostics and may receive royalties resulting from use of PrecivityAD2.