Importance of Microbiomes in mouth: (Introduction)

by David Turell , Thursday, December 28, 2023, 23:06 (341 days ago) @ David Turell

From Neanderthals to us:

https://www.newscientist.com/article/mg26034711-800-why-tending-your-oral-microbiome-is...

"looking after our oral microbiome: the viruses, fungi and 700 or so species of bacterium that reside in our mouths. Let our oral hygiene slip, and bad bacteria from there can travel all over the body, causing or exacerbating problems, from cardiovascular disease and cancer to Alzheimer’s disease and arthritis. Keeping everything in balance, on the other hand, staves off decline.

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"DNA sequencing technology has improved apace...We know, for instance, that people with gum disease are as much as 20 per cent more likely to get cancer in their lifetimes compared with otherwise healthy people.

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"...in 2019, scientists discovered species of bacteria known to cause gum disease – including one called Porphyromonas gingivalis – living inside the brains of people who died of Alzheimer’s disease. There were also gingipains, protein-degrading enzymes produced by P. gingivalis, in their hippocampi, a region of the brain responsible for memory...If the mouth bacteria were getting into the brain, that lent weight to the idea that they could be a cause of Alzheimer’s.

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" Where the teeth meet the gums is a tiny gap called a sulcus. In a person with healthy teeth and gums, this gap is small, but if you don’t brush properly, bacteria can build up, causing inflammation. As the gums become more inflamed, they start to pull away from the teeth, and a deeper pocket forms. Harmful bacteria can hide and multiply in this airless environment, and then, if you have bleeding gums, they can get into your bloodstream.

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"Microglia act as first responders, destroying invading pathogens and sending out chemical signals that summon other immune cells to join the fight. They are also responsible for destroying beta-amyloid plaques. So, in the brains of such people, microglia are already working double time. Kantarci thinks that, when the oral bacteria arrive, they tip the already overextended microglia over the edge and kick off a snowball effect of inflammation. Scientists already suspect that inflammation might be the underlying cause of Alzheimer’s disease. In that view, the oral bacteria might be another contributing factor, perhaps the straw that breaks the camel’s back.

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"...people with inflammatory bowel disease (IBD), a group of conditions in which the immune system attacks parts of the digestive system. One hypothesised explanation for IBD is that the gut lining is more oxygenated than usual, so the intestine is more accommodating to oral bacteria...In people with IBD, the gut lining could be leaky, enabling oral bacteria to get into the blood. This would then make the immune system ... result in the gut attacking itself. There is already evidence from studies in mice that indicates this might be the case.

["A] study tracked more than 10,000 healthy volunteers over 15 years and showed that participants with gum disease were more than twice as likely to go on to have a stroke as people without the condition. Meanwhile, a separate analysis showed that gum disease and tooth loss increased the risk of coronary artery disease by 24 and 34 per cent, respectively.

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"...studying plaque on the teeth of human remains from as far back as about 20,000 years ago through to the modern day. In general, the oral health of Neanderthals and ancient humans was excellent, she says. There are only a few known examples of cavities in Neanderthal teeth, and these come from places where they ate acorns, a relatively sugar-rich food. But they did still get a gunky build-up of plaque on their teeth, and Weyrich’s goal was to analyse the DNA in this to reconstruct a history of the human oral microbiome.

"So far, she has found that the oral microbiome of our ancestors became markedly unhealthier after we switched from being hunter-gatherers to farmers about 8000 years ago. At that time, “people drastically shifted their diet and started eating more carbohydrates, and that selected for the types of microbes that we associate with things like dental cavities”, says Weyrich. In unpublished work, she has since found that similar step changes in the oral microbiome occurred after the industrial revolution and the second world war.

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"Her team has conducted successful transplants in rats, but more work is needed before the technology can be applied to humans. One concern, for example, is that different populations of people have distinct oral biomes, so giving an Indigenous Australian person, for instance, a bacterium from a European might be ineffective or even harmful. There is also the question of how to grow the microbes that our ancestors had, many of which are no longer easy to come by.

"Weyrich says we simply don’t know what will happen if we take microbes that lived in the mouths of our ancestors and plonk them into a modern mouth – so we must proceed with caution. “It will be quite a puzzle to put it all together,” she says. “But it’s a puzzle we are really excited about tackling.'”

Comment: it seems the more civilized we are the worse our teeth become. From a theodicy view, bacteria are good for us until they sneak into a bad place.