Victoria Frankel

The Neurodegenerative Disease: Alzheimer’s and the Gut Microbiome

Sep 01, 2019

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When we take steps to optimize our health, we are often struck by visions of our youth – what it felt like to be young and energetic, carefree and bold – but sometimes we are driven by concern for our future. There are many reasons to look forward to our lives as we age: the prospect of our growing families, the accrual of memories, and the wisdom that comes with all of our experiences. However, there are many reasons why people look to their future with concern and anxiety, especially when it comes to age-related neurodegenerative diseases like Alzheimer’s that claimed half a million lives in 2010 alone1.

The heartbreak of having a loved one struggle with Alzheimer’s disease comes not only from losing them after a difficult battle, but from watching with devastation as they slowly lose themselves. Alzheimer’s continues to be one of the most under-diagnosed and undertreated diseases in America, costing over 170 billion dollars per year in healthcare costs1. The rate of developing Alzheimer’s doubles every 10 years after the age of 60, with higher incidences marked in women. 

 

Alzheimer’s Disease Is More Complex Than Simply Memory Loss

Like many neurodegenerative diseases, Alzheimer’s manifests as microscopic lesions within the brain - called plaques. The main component of these plaques is a protein called beta amyloid p-peptide (Aß) that accrues in various sites within the brain, creating “grey matter.” At first, they affect brain areas associated with cognition but can spread through the whole brain. These plaques ultimately injure our neurons and cause the brain cells to degrade. This can cause minor to severe changes in behavior, beginning as slight and selective short-term memory loss. Over time, long-term memory becomes compromised and issues with motor-control and language can happen. Although the outcome remains the same for most diagnosed with Alzheimer’s disease, the rate of this loss can vary greatly. On average, Alzheimer’s disease patients live for 8-10 years after diagnosis, while others persist for 20 years - making caring for loved ones often unpredictable2.

Studies have recognized a few genetic factors that contribute to Alzheimer’s risk, including a mutation in certain genes, however this only accounts for fewer than 1% of cases3. Other than these, age has been the only other well-established risk factor for the disease. This is changing, however, as scientists are exploring interactions of the gut-brain axis in neurodegenerative diseases including dementia, Parkinson’s, and Alzheimer’s.

 

From Brain Health to Gut Health

The gut-brain axis is the back-and-forth line of communication between our central nervous system and our digestive tract. The two systems are connected by the vagus nerve which transmits signals that are responsible for many sensations (like cravings for certain foods) and emotions (like anxiety). Recently, scientists have uncovered a direct interaction between the microbes in our gut with this system4. Furthermore, studies have shown the microorganisms in our gut may be affecting our risk for neurodegenerative diseases by sending messages to our brain when gut dysbiosis – the imbalance of our gut microbiome - occurs5. Gut dysbiosis can cause severe damage in our gut, leading to disorders like leaky gut syndrome that can allow toxins and bacteria to pass through our intestinal lining and wreak havoc on our body.

When this happens, our immune system triggers an inflammatory response and if not corrected, can lead to chronic and systemic gut inflammation. Then the cycle keeps going and we end up with harmful bacteria byproducts travelling through our bloodstream and passing into our blood-brain barrier - that protective bubble around our brain that normally prevents harmful molecules and bacterial byproducts from settling in our brain. When these molecules penetrate into the brain, the result can cause neuroinflammation and injure brain cells. Viome’s own researchers believe that harmful microbial activity may result in damaging the blood brain barrier, allowing microbes and viruses easier access and perpetuating the injury to the brain.

Additionally, disturbances along the gut-brain axis from leaky gut syndrome can interrupt production of important neurotransmitters like serotonin, dopamine and metabolites like short chain fatty acids (SCFAs) – metabolites of many beneficial bacteria in our gut6. Butyrate, a SCFA, contributes to the health of our intestinal lining and can act as an anti-inflammatory molecule. Now, some scientists have found that patients with Alzheimer’s contain low activity from these microbes. Low butyrate production activity from such bacteria could make your gut lining more vulnerable and influence how much inflammation is occurring in the gut. These studies show that most patients with Alzheimer’s disease share a similar microbiome pattern in their gut7.

 

The Problem with Treatments

The few drugs approved to treat Alzheimer’s disease work to increase communications between neurons and improve memory and learning, but none actually regenerate the cells. Instead, the disease progression is slightly hindered with an incredible amount of side effects that range from headaches and dizziness to vomiting and cardiac strain8. Unfortunately, current treatments fail to stop Alzheimer’s in its tracks.

But there is hope. Studies are showing that diet might not only significantly influence the health of our gut, but impact how dysbiosis and chronic inflammation affect our body. Some studies have suggested that improving diet can enact beneficial changes on our health long term and reduce neurological decay9

With emerging research expanding our understanding of how interlinked the health of our gut is with the health of our entire body and mind, there is so much promise in innovative ways to improve our quality of life as we age. Who knows, we might be right on the edge of a brand new precipice when it comes to neurological disease treatments. If you’re like us at Viome, then you might be on the “edge” of your seat waiting to learn more.

We can’t necessarily predict the future, but trust us when we say we are almost there. It certainly feels like disease research is on the brink of a new horizon.


*The information on the Viome website is provided for informational purposes only and with the understanding that Viome is not engaged in rendering medical advice or recommendations. Viome is providing this educational information to share the exciting developments being reported in the scientific literature about the human microbiome and your health. Viome products are not intended to diagnose, treat, or prevent any disease.



Resources: 

1.     Kumar A, Tsao JW. Alzheimer Disease. StatPearls. Treasure Island (FL)2019.

2.     Small GW, Rabins PV, Barry PP, et al. Diagnosis and treatment of Alzheimer disease and related disorders. Consensus statement of the American Association for Geriatric Psychiatry, the Alzheimer's Association, and the American Geriatrics Society. JAMA. 1997;278:1363-1371.

3.     Tang YP, Gershon ES. Genetic studies in Alzheimer's disease. Dialogues Clin Neurosci. 2003;5:17-26.

4. Martin CR, Osadchiy V, Kalani A, Mayer EA. The Brain-Gut-Microbiome Axis. Cell Mol Gastroenterol Hepatol. 2018;6:133-148. 

5.     Kohler CA, Maes M, Slyepchenko A, et al. The Gut-Brain Axis, Including the Microbiome, Leaky Gut and Bacterial Translocation: Mechanisms and Pathophysiological Role in Alzheimer's Disease. Curr Pharm Des. 2016;22:6152-6166.

6.     Bhattacharjee S, Lukiw WJ. Alzheimer's disease and the microbiome. Front Cell Neurosci. 2013;7:153.

7.     Haran JP, Bhattarai SK, Foley SE, et al. Alzheimer's Disease Microbiome Is Associated with Dysregulation of the Anti-Inflammatory P-Glycoprotein Pathway. MBio. 2019;10.

8.     Schachter AS, Davis KL. Alzheimer's disease. Dialogues Clin Neurosci. 2000;2:91-100.

9.Abate G, Marziano M, Rungratanawanich W, Memo M, Uberti D. Nutrition and AGE-ing: Focusing on Alzheimer's Disease. Oxid Med Cell Longev. 2017;2017:7039816. 



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The Neurodegenerative Disease: Alzheimer’s and the Gut Microbiome

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