Dementia with Lewy bodies (DLB) is a common form of dementia that has no cure.
Recent studies suggested that gut bacteria could be involved in Parkinson’s disease, but the bacteria that are linked to Lewy bodies dementia were not known.
However, a research team led by Nagoya University in Japan identified three bacteria that are related to DLB, which are Collinsella, Ruminococcus, and Bifidobacterium.
These findings provide new possibilities for the diagnosis and treatment of Lewy bodies dementia.
Lewy bodies dementia occurs due to abnormal deposits of alpha-synuclein, a protein in the brain that affects chemicals in the brain, leading to declines in thinking, reasoning and memory.
Symptoms include confusion, memory loss, impaired movement, and visual hallucinations.
Parkinson’s disease starts with movement problems, but some patients develop cognitive decline within one year, and these patients are diagnosed with Lewy bodies dementia.
It is hard for physicians to predict who will develop cognitive decline within a year and become patients with Lewy bodies dementia.
In the study, the researchers analyzed microorganisms in the gut and fecal bile acids of patients with Lewy bodies dementia, Parkinson’s disease, and rapid eye movement behavior disorder.
They found that three intestinal bacteria, Collinsella, Ruminococcus, and Bifidobacterium, were associated with patients with Lewy bodies dementia.
The researchers also found similarities between the gut bacteria involved in Parkinson’s disease and Lewy bodies dementia.
SCFA-producing bacteria were decreased in both diseases. In Lewy bodies dementia, there was an increase in Ruminococcus torques, an increase in Collinsella, and a decrease in Bifidobacterium.
Reduced levels of Bifidobacterium may suggest possible ways to treat Lewy bodies dementia.
Bifidobacterium increases brain-derived neurotrophic factor, a key protein that supports the growth, development and maintenance of neurons in the central and peripheral nervous systems.
Therefore, its decrease in Lewy bodies dementia is likely to be associated with cognitive decline.
Similarly, both Ruminococcus torques and Collinsella carry an enzyme, the product of which regulates inflammation in a region of the brain called the substantia nigra.
Compared to Parkinson’s disease, the levels of these bacteria were higher in people with Lewy bodies dementia.
This may explain why the effect on movement is delayed, a key feature that distinguishes Lewy bodies dementia from Parkinson’s disease.
The researchers suggest that their findings can be used for both diagnosis and treatment. The gut microbiome may help to identify patients with Lewy bodies dementia.
Administering Ruminococcus torques and Collinsella in patients with Parkinson’s disease is expected to delay neuroinflammation in the substantia nigra.
Therapeutic intervention to increase Bifidobacterium may delay the onset and progression of Lewy bodies dementia and reduce cognitive dysfunction.
If you care about brain health, please read studies about how the Mediterranean diet could protect your brain health, and strawberries could help prevent Alzheimer’s disease.
For more information about brain health, please see recent studies that cranberries could help boost memory, and many older people have this non-Alzheimer’s dementia.
The study was conducted by Hiroshi Nishiwaki et al and published in npj Parkinson’s Disease.
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