Thursday 9 December 2021

Are some gut microbes associated with cognitive decline?


Can microbiology help to predict cognitive decline? This is in relation to diseases such as Alzheimer’s? It appears that this might be possible according to some new research which draws upon medical microbiology.


Recent research has discovered that changes in the gut microbiota (these are the trillions of bacteria and other microbes that live in the intestines, along with their genetic components) possess the capacity to alter the brain and behavior.


This was demonstrated by means of an experiment. For this study, mice were used and the researchers discovered that a particular balance (or imbalance) of gut microbes plays a role in exacerbating the effects of cognitive impairment.


This is due to how gut microbes affect the hippocampus (this is the region of the brain that is critical for memory and learning). It was discovered that the concentration of one group of bacteria of the genera Bilophila increased significantly as part of the gut microbiota of mice fed that were fed a ketogenic diet.


A ketogenic diet is one composed of high-fat, adequate-protein, and low-carbohydrates. In addition to being fed this diet, the mice were intermittently deprived of oxygen, creating the condition of hypoxia. It was shown that by depriving the animals of some oxygen created cause cognitive impairment.


The researchers found that a ketogenic diet, hypoxia and treatment with a species of Bilophila named Bilophila wadsworthia impaired the hippocampus. The consequence of this was reduced cognitive ability in mice.


To demonstrate this experimentally, researchers gave several mice a ketogenic diet and others a standard diet. The two groups of mice then received reduced levels of oxygen for five consecutive days. After this the mice were afforded four days to recover.


The scientists then observed the ability of the different groups of mice to navigate a maze. When trying to find their way out of a maze, mice on the ketogenic diet made an average of 30 percent more errors compared with mice fed on the standard diet.


The researchers next evaluated whether the different diets could cause any change in cognitive behavior for the mice that had not been deprived of oxygen. Here there was no appreciable difference in the mice's ability to find their way out of the maze, in relation to both the ketogenic diet or the standard diet.


This infers that the negative impact on cognitive ability only occurred in combination with oxygen deprivation.


Following this, the scientists investigated what would happen if they depleted the mice's microbiota before administering a ketogenic diet and exposing them to hypoxia. Here it was observed that the mice which had their microbiota depleted first made fewer errors in the maze compared with mice that were exposed to hypoxia and then fed a ketogenic diet but which not had changes to their microbiota first.


The overall data suggests that the microbes associated with the ketogenic diet and hypoxia could contribute to the detrimental effects on cognitive impairment.


The research appears in the journal Cell Host & Microbe, under the title “Alterations in the gut microbiota contribute to cognitive impairment induced by the ketogenic diet and hypoxia.”


Posted by Dr. Tim Sandle, Pharmaceutical Microbiology Resources (

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