Glucosamine plays important roles in brain function.
Glucosamine is a type of sugar found in the muscles, cartilage, and other soft tissues of the body. It is commonly marketed as a dietary supplement used for joint pain and stiffness. Evidence from a 2021 study suggests that glucosamine is prevalent in brain glycogen, where it plays important roles in glycosylation.
Glycogen is a multi-branched polysaccharide that serves as the stored form of glucose in the human body. Most of the body’s glycogen stores are found in the muscles and liver, but some glycogen is found in the brain, primarily in the astrocytes, a type of cell involved in neurogenesis and blood-brain barrier maintenance. In diseases in which glycogen storage is impaired, glycogen-like cellular aggregates called polyglucosan bodies can form in the brain, altering brain function and driving dementia.
Glycosylation is a biochemical process in which glucose is added to an amino acid. It plays important roles in determining the structure, function, and stability of proteins. Glycosylation influences neurological function, and disturbed glycosylation is implicated in the pathogenesis of many neurological disorders, including cognitive decline.
The investigators conducted a multi-part study. First, they determined the overall composition of the sugars in the glycogen of liver, muscle, and brain tissue of mice using gas chromatography and mass spectrometry. They found that liver glycogen contained just 0.1 percent glucosamine, and muscle glycogen contained approximately 1 percent of the sugar. However, brain glycogen contained 25 percent glucosamine.
Then, using a special form of mass spectrometry (called “MALDI TW IMS”), they quantified and tracked the movement of the glucosamine in the brains of healthy mice and mice that had glycogen storage diseases. They found that the mice with the glycogen storage diseases had impaired glucosamine movement, abundant polyglucosan bodies, and evidence of impaired cell metabolism and glycosylation.
These findings suggest that glucosamine in brain glycogen is essential for brain health. They also may help identify strategies for treating glycosylation disorders, which cause severe neurological symptoms, including dementia.
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