Alzheimer’s disease (AD) is a progressive disorder of the brain that ranks as a leading cause of dementia globally. Despite extensive research, a definitive cure remains elusive. Recently, new antibody-based therapies targeting amyloid β (Aβ) have emerged, but their advantages have been somewhat limited. Moreover, these treatments can be quite costly and may lead to immune-related side effects, highlighting a pressing need for safer, more affordable options that could potentially slow the disease’s progression.
A new study published in Neurochemistry International presents an intriguing possibility. Researchers from Kindai University and their collaborators found that arginine, a naturally occurring amino acid, can decrease the aggregation of harmful Aβ proteins in animal models of Alzheimer’s. Additionally, arginine serves as a safe chemical chaperone, assisting proteins in retaining their proper structure.
The research team, which included Graduate Student Kanako Fujii and Professor Yoshitaka Nagai from the Department of Neurology at Kindai University Faculty of Medicine in Osaka, along with Associate Professor Toshihide Takeuchi from the Life Science Research Institute at the same university, noted that while arginine is readily available as an over-the-counter supplement, the doses and techniques used in this study were tailored specifically for research and differ from commercial products.
Lab and Animal Studies Show Strong Effects
In their lab experiments, the scientists demonstrated that arginine can inhibit the formation of Aβ42 aggregates, which are particularly toxic. This effect intensified with higher concentrations of arginine.
The team then evaluated oral arginine in two well-established models for Alzheimer’s:
- A Drosophila model expressing Aβ42 with the Arctic mutation (E22G)
- An AppNL-G-F knock-in mouse model, which bears three familial AD mutations
In both scenarios, treatment with arginine led to a reduction in Aβ accumulation and mitigated its damaging effects.
“Our study indicates that arginine can limit Aβ aggregation both in vitro and in vivo,” says Prof. Nagai. “What makes this discovery exciting is that arginine is already recognized for its clinical safety and affordability, making it a highly promising candidate for reconsideration as a treatment for AD.”
Improved Brain Health and Reduced Inflammation
In the mouse model, the advantages of arginine extended beyond just reducing protein accumulation. It lowered levels of amyloid plaques and decreased the amount of insoluble Aβ42 in the brain. Mice that received the treatment performed better in behavioral tests.
The researchers also observed that arginine reduced the activity of genes associated with pro-inflammatory cytokines, which are linked to neuroinflammation, a key feature of Alzheimer’s disease. This suggests that arginine might not only inhibit harmful protein aggregation but could also provide broader protection for brain cells.
“Our findings open the door to developing arginine-based approaches for neurodegenerative diseases linked to protein misfolding and aggregation,” Professor Nagai reflects. “Given its excellent safety profile and low cost, arginine could quickly move into clinical trials for Alzheimer’s and possibly other related conditions.”
A Low-Cost Path Toward New Alzheimer’s Treatments
The study underscores the growing interest in drug repositioning, which seeks to find new applications for existing, well-established drugs. Since arginine is already clinically utilized in Japan and has demonstrated the ability to safely access the brain, it may sidestep some initial challenges typical of traditional drug development.
Nonetheless, researchers emphasize that further investigation is essential. More preclinical and clinical studies will be necessary to establish whether these results hold true in humans and to determine the best dosing protocols.
Despite this, the findings provide compelling early evidence that straightforward nutritional or pharmacological strategies might aid in reducing amyloid buildup and enhancing brain function.
Expanding Understanding of Alzheimer’s Biology
Aside from its potential therapeutic benefits, this research contributes new insights into how Aβ proteins develop and accumulate in the brain. It also suggests a practical and cost-effective method that could ultimately help millions of individuals living with Alzheimer’s around the globe.
Professor Yoshitaka Nagai, who specializes in neurodegenerative diseases such as Alzheimer’s, Parkinson’s, and amyotrophic lateral sclerosis, focuses on protein misfolding and RNA-related mechanisms. He has received several honors from various organizations, including the Japanese Society of Neurochemistry and the Japanese Dementia Society.
This research was supported by the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) (Grant No. 20H05927), Japan Society for the Promotion of Science (JSPS) (Grant Nos. 24H00630, 21H02840, 22H02792, and 25K02432), Japan Science and Technology Agency (JST) Super-Highway Program (SHW2023-03), and National Center of Neurology and Psychiatry.
