Alzheimer’s disease continues to be a leading cause of death in the United States. Approximately, 1 in every 3 seniors die with Alzheimer’s or dementia, which exceeds the number who die from prostate and breast cancers.
No cure has been found. However, the link between brain health and gut microbiota is increasingly clear. New research suggests that the bacteria in your intestines may impact brain functioning and promote neurodegeneration.
A team of Italian and Swiss scientists have pursued this link with research that points to the connection between imbalanced gut microbiota and the development of amyloid plaques in the brain. A key characteristic of Alzheimers is the accumulation of beta-amyloid plaques and neurofibrillary tangles in the brain.
Proteins produced by gut bacteria may trigger Alzheimer’s
Their study looked at 89 people between 65 and 85 years of age. Some of them suffered from Alzheimer’s disease or other neurodegenerative diseases. Others presented with no memory problems and were generally healthy.
Using PET imaging, the scientists measured amyloid deposition in their brains. In addition, they measured markers of inflammation and proteins produced by intestinal bacteria, such as short-chain fatty acids and lipopolysaccharides in their blood.
Lipopolysaccharides (LPSs) are the cell walls of dead bacteria. However, your immune system treats them as living bacteria and inappropriately initiates an immune response to attack them. LPSs are pro-inflammatory and have been found in amyloid plaques in the brains of Alzheimer’s patients.
The study revealed that high blood levels of LPSs and the short-chain fatty acids (SCFAs) acetate and valerate were associated with large amyloid deposits in the brain. Other SCFAs, like butyrate, seemed to have a protective effect. The study found that high levels of butyrate were linked to amyloid.
Butyrate is an SCFA that gut bacteria produce when fermenting fiber. It activates the secretion of brain-derived neurotrophic factor (BDNF). Alzheimer’s disease has been linked to decreased levels of BDNF.
“Our results are indisputable: Certain bacterial products of the intestinal microbiota are correlated with the quantity of amyloid plaques in the brain,” said Moira Marizzoni, a study author with the Fatebenefratelli Center in Brescia, Italy.
Probiotics may work as a preventative
This specific study built on the prior research conducted by the team, which suggested that the gut microbiota in people with Alzheimer’s disease differs from those without the condition. In those with Alzheimer’s, microbial diversity is decreased. Some bacteria were overrepresented and others were reduced.
Furthermore,” said neurologist Giovanni Frisoni, study author and director of the University Hospitals of Geneva (HUG) Memory Center in Switzerland, “we have also discovered an association between an inflammatory phenomenon detected in the blood, certain intestinal bacteria and Alzheimer’s disease; hence the hypothesis that we wanted to test here: Could inflammation in the blood be a mediator between the microbiota and the brain?”
With the connection growing stronger, the team is planning further research to reveal which specific bacteria or groups of bacteria may be responsible for the effect, which could ultimately lead to a preventive treatment “cocktail.” “Indeed, we must first identify the strains of the cocktail. Then, a neuroprotective effect could only be effective at a very early stage of the disease, with a view to prevention rather than therapy,” Frisoni said in a news release.8
“However, early diagnosis is still one of the main challenges in the management of neurodegenerative diseases, as protocols must be developed to identify high-risk individuals and treat them well before the appearance of detectable symptoms.”
Probiotics and Alzheimer’s
The effect of beneficial bacteria on brain health is well-established, including in people with Alzheimer’s disease. In 2016, a study of 60 Alzheimer’s patients investigated the impact of probiotic supplements on cognitive function. The scientists found promising results. The group that consumed probiotics experienced an increase in scores on the Mini-Mental State Examination (MMSE). The group that did not consume probiotics experienced a decrease in scores on the MMSE.
In addition, the probiotics group had decreased triglycerides, beneficial metabolic changes, reduced markers for insulin resistance, and very low density lipoprotein and C-reactive protein, which are measures for inflammation.
The researchers suggested the beneficial metabolic changes may be responsible for the cognitive improvements. This is supported by other studies that indicate the GI tract microbiome in Alzheimer’s is significantly altered in composition when compared to age-matched control subjects.
Both the GI tract and blood-brain barriers become significantly more leaky with aging. This may enable the GI tract microbial exudates (lipopolysaccharides, amyloids, endotoxins and small non-coding RNAs) to find their way into various areas of the central nervous system.
Probiotics may inhibit neurodegeneration
Scientists believe that probiotics may influence the central nervous system through the microbiota-gut-brain-axis. And many have pointed to the potential of both preventive and therapeutic effects for Alzheimer’s disease by counteracting oxidative stress and modulating the inflammatory process. In fact, the dysfunction in cognition and behavior may be linked with imbalances with the gut microbiota. Activation of gut inflammation may be one factor in cognitive deterioration and dementia.
Other studies have shown that the gut microbiota of Alzheimer patients have a distinctive decrease in anti-inflammatory bacterial species (e.g. Bifidobacterium brevestrain A1) and increased abundance of pro-inflammatory flora phyla (e.g. Firmicutes and Bacteroidetes).
This means that the gut bacteria was imbalanced towards proinflammatory bacteria.
Restoring a balanced gut microbiota in Alzheimer’s patients may actually slow the progression of the disease, which gives physicians more tools in their arsenal to treat and prevent the devastating disease.
Another study a meta-analysis involving five studies and 297 subjects, which pointed to a significant improvement in cognition and a significant reduction in malondialdehyde and high-sensitivity C-reactive protein, inflammatory, and oxidative biomarkers in study subjects who took probiotics when compared with those who did not take probiotics.
More research is discovering which bacterial may be the most beneficial. At this time, it appears the Bifidobacterium breve strain A1 may be quite helpful for Alzheimer’s patients. In one study, scientists used Alzheimer’s disease model mice and confirmed that daily oral administration of B. breve A1 reduced the cognitive dysfunction typically caused by amyloid beta plaques.
One of the mechanisms behind these protective effects was found to be suppression of amyloid-beta-induced changes in gene expression in the hippocampus. In short, the bacterium had an ameliorating effect on amyloid-beta toxicity.
Still other research suggests gut microbiota may contribute to Alzheimer’s risk via multiple avenues, including by influencing aging, diabetes, sleep and circadian rhythm.
In addition, some scientists hypothesize that decades of factors like aging, genetics, diet, and stress work together to damage gut permeability and increase the leak of detrimental factors through into the system. Detrimental factors include pathogens, inflammatory agents, and other factors that may activate a neuroinflammatory response in the brain.
There is growing evidence that gut microbiota may impact how Alzheimer’s disease develops by disrupting metabolic balance and inflammation in the brain.
Alzheimer’s prevention strategies
Optimizing your gut flora is an easy prevention strategy to adopt. Avoid processed foods, antibacterial products, antibiotics, chlorinated and fluoridated water, and consume a good amount of traditionally cultured and fermented foods. In addition, take a high-quality probiotic supplement.
Fasting can also be another important strategy, as is reducing your intake of polyunsaturated fatty acids, also called PUFAs, found in vegetable oils, edible oils, seed oils, trans fat, and plant oils. A high-fat, moderate-protein, low net-carb ketogenic diet is ideal for preventing degeneration that can lead to Alzheimer’s and help to nourish a healthy gut.
Overall, nourishing your brain health is best done with a comprehensively healthy lifestyle. This included the use of exercise, a healthy diet, optimizing vitamin D and other hormones, increasing sleep, meditation, detoxification and eliminating gluten and processed food.
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