An imbalanced gut microbiome can affect the brain and brain cancer through hormones and metabolites in the blood or lymph and/or through the central nervous system; it is almost certainly crucial in the prevention and/or treatment of brain cancer.
The Blood brain barrier (BBB) plays a significant role in a healthy brain. Within the brain, immune function is modulated by Microglial cells. There are two types – M1 microglial cells that are concerned with destruction and M2 that are concerned with tissue regeneration.
When pathogens are present, the microglia activate T-cells to secrete a pro-inflammatory response. Next the T-cells release cytokines to transform the microglia from M1 to M2 and so begin the healing process. In brain tumours, this latter step has gone wrong largely because the microglial cytokines are over expressed and microglial numbers are reduced.
However, it would seem some of this can be reversed by bacteria from the gut microbiome but, in the main, the BBB becomes damaged and T-cells, B-cells and macrophages cross into the brain.
Go to: Gut microbiome controls your immune response
The two way communication between glioma cells and the microbiome then creates an immune-suppressed environment that promotes tumour growth and survival. M2 cells rush to the glioma, but instead of healing, they promote glioma growth in GBM. Regulatory T cells then rush to the area and again, merely serve suppress the natural brain immune system. NK cells are also weakened probably due to an imbalanced microbiome and poor immune function in the body. People with allergic reactions and/or autoimmune problems have a heightened immune system, active NK cells and lowered levels of Glioma (GBM).
Go to: How a parasite damages the microbiome
In a meta-analysis on the subject (1), researchers from Israel, the NCI and Australia, felt that a balanced microbiome may well be essential to preventing and treating a brain tumour. For example, a healthy gut microbiome produces short-chain esters, some of which are known to reduce the secretion of pro-inflammatory cytokines affecting neurotransmitters and neuromodulators.
The gut microbiome is known to affect the brain, through immune cells, hormones and metabolites in the blood and lymph and through the Central Nervous System. There is also research that links the general lymphatic system to lymphatic vessels in the brain. Thus an imbalanced microbiome and its pathogens can have a multitude of ways of influencing a brain and a brain cancer.
Go to: Everything you need to know about brain cancer
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Reference
- The Gut-Brain Axis – paving the way to brain cancer; Ruty Mehrian-Shal, Juergen Reichardt, Curtis Harris, Amos Toren, 2019.