Presence of Mouth Bacteria Linked to Risk of Alzheimer’s, Study Shows

Presence of Mouth Bacteria Linked to Risk of Alzheimer’s, Study Shows
A connection discovered between Alzheimer's and the bacteria that cause gum disease suggests that improved oral hygiene may decrease the risk of developing the disorder, a study reports. The study, "Porphyromonas gingivalis in Alzheimer’s disease brains: Evidence for disease causation and treatment with small-molecule inhibitors," was published in the journal Science Advances. Figuring out exactly what causes Alzheimer's has long been a goal of researchers, and some have suggested that the disease may be at least partially attributed to infections. This association is based largely on the fact that Alzheimer's brains tend to have inflammation comparable to what might be expected in an infected brain. The new study implicates the bacterium Porphyromonas gingivalis in Alzheimer's. This bacterium is one of the main causes of periodontitis — a disease characterized by inflamed gums. The research suggests that it can migrate from the mouth to the brain and, once in the brain, secrete toxins that cause damage to brain cells. Previous research had actually demonstrated this migratory capacity in mice — this new study shows that P. gingivalis is also detectable in the brains of humans with Alzheimer's. P. gingivalis produces major virulence factors known as gingipains, which consist of lysine-gingipain (Kgp), arginine-gingipain A (RgpA), and arginine-gingipain B (RgpB). Gingipains are secreted by the bacteria and released to the outside cellular environment inside small vesicles. Researchers tested 53 brain samples for the presence of bacterial proteins. Depending on which of two proteins they looked for, Kgp or RgpB, 91% or 96% of Alzheimer's brains were positive, respectively. In contrast, among control non-demented brains, only 52% or 39% were positi
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