Probiotics reveal a surprising link between gut microbiota and Alzheimer’s Disease progression
If your doctor told you that eating yogurt every day could reduce your chances of getting Alzheimer’s Disease (AD), how would you react? If you were like me, you’d probably switch to a new doctor. However, a recent 2024 study shows that this statement may contain some truth [1]. In fact, the findings of this study show an unexpected correlation between cognitive function and probiotic supplementation—adding new bacteria to your gut.
AD is the most common form of dementia, where certain parts of the brain responsible for memory, thinking, and communication skills deteriorate and waste away over time [2]. This disease is incredibly challenging and tragic for loved ones, and as the world population’s average age increases, so does the average person’s risk of AD, thus increasing the urgency for finding an effective therapy. Interestingly, recent findings point toward the gut-brain axis as a potential new target for therapies [1]. The gut-brain axis is a bidirectional communication pathway between the gut and the brain. Research suggests that imbalances in gut microbiota could worsen the progression of AD, making the gut-brain axis the target of a 2024 study.
In this study, the researchers investigated the effects of probiotic administration on the progression of neurodegeneration and AD in a certain type of mouse model engineered to develop AD [1]. Two strains of probiotics were used: Lactobacillus plantarum KY1032 and Lactobacillus curvatus HY7601. They have been shown to improve age-dependent memory deficits in rats and reduce inflammation in obese mice in previous studies. The researchers hypothesized that these probiotics would improve memory functions in AD mice. There were three groups of mice: untreated wild-type mice, mouse model mice that were on a normal diet, and the experimental group of mice that ingested probiotics daily starting from the age of seven months. After seven weeks of probiotic supplementation, the mice were then put in a maze and given time to learn how to escape, and researchers recorded each mouse’s escape time. Trials started at week seven of probiotic supplementation and continue for a total of six weeks [1].
As expected, the untreated wild-type mice had the lowest average escape time of around 27.25 seconds, suggesting good spatial memory [1]. The control mice had the longest average escape time of around 86.80 seconds, indicating poor spatial memory in these mice. Finally, the probiotic-treated, experimental group’s average escape time was around half that of the untreated mice at around 52.05 seconds. These mice had significantly faster and less erroneous performance compared to the AD-prone untreated control group, showing a positive correlation between cognitive function and probiotic supplementation. The reason behind this correlation requires more research. However, it is interesting to note that the groups receiving probiotic supplementation produced significantly higher levels of blood adiponectin, a metabolic regulator linked to cognitive performance and neuroinflammation control. Nonetheless, the researchers reasonably concluded that probiotic supplementation could mitigate the neurodegeneration and cognitive decline associated with AD [1].
The findings of this study are a huge step towards discovering an effective AD therapy [1]. Probiotic therapy would be quite inexpensive, accessible, and have little to no detrimental side effects, especially compared to traditional AD treatments. However, it is important to note the limitations of these findings. Mice were used in this study, which is a much less complex organism than humans. More notably, the probiotic treatment did not produce significant changes in the gut microbiota of the mice, except for an increase in the abundance of Bacteroidetes, one of two dominant classifications of bacteria. This is of particular concern and calls for additional studies, as the original hypothesis of this study looked at imbalances in gut microbiota in relation to AD. Lastly, the diversity of gut microbiota populations in humans may require personalized formulations of probiotics to maximize efficacy and limit potential side effects. Additional research also needs to be done to work out the molecular mechanisms linking the gut microbiota and AD progression [1].
Although the intricacies of how these complicated gut microbial processes affect the brain may need more investigation, one takeaway is clear: probiotic supplementation had a significant impact in this study on one mouse model of AD. In this day and age, AD is a global health concern. Dementia is projected to triple worldwide by 2050, yet an effective treatment for AD, the major cause of dementia, is still nonexistent [3]. These findings might not completely sell out Chobani. But they could offer a daily supplement that targets the gut-brain axis and provides an accessible, low-risk addition to Alzheimer’s therapies.
References:
[1] Medeiros, D., McMurry, K., Pfeiffer, M., Newsome, K., Testerman, T., Graf, J., Silver, A. C., & Sacchetti, P. (2024). Slowing Alzheimer's disease progression through probiotic supplementation. Frontiers in neuroscience, 18, 1309075. https://doi.org/10.3389/fnins.2024.1309075
[2] Hoyer S, Baker S and Mohiyeddini C. (2023). What Is Alzheimer’s Disease?. Frontiers for Young Minds. 11:1149635. doi: 10.3389/frym.2023.1149635
[3] Zhang, Y., Zhang, J., Wang, Y., & Yao, J. (2023). Global trends and prospects about synaptic plasticity in Alzheimer's disease: a bibliometric analysis. Frontiers in aging neuroscience, 15, 1234719. https://doi.org/10.3389/fnagi.2023.1234719