Sugars May Affect Brain's Ability to Learn, Remember

Sugars may have an impact on the brain plasticity that helps to learn, remember, and recover, a study in mice suggests. The findings could give new insights into neurodevelopmental disorders, such as autism.

The sugars found in fruits or sweets are just a few simple varieties of the many existing types of sugar. When strung together, they can make a wide array of complex sugars.

According to new research presented at the fall meeting of the American Chemical Society (ACS), sulfate groups on complex sugar molecules called glycosaminoglycans (GAGs) affect "plasticity" in the brains of mice. These sugars regulate numerous proteins, and their structures change during development and with disease.

GAGs are formed by attaching other chemical structures, including sulfate groups. The most common GAG form in the brain is chondroitin sulfate, found outside many of the brain cells.

Chondroitin sulfate can also form structures known as "perineuronal nets," which wrap around individual neurons and are thought to stabilize synaptic connections, which are places where neurons connect and communicate with each other.

One way to change a GAG's function is through patterns of sulfate groups tacked onto the sugar chains, called sulfation motifs.

In the study, deleting the Chst11 gene responsible for forming two major sulfation patterns on chondroitin sulfate in mice resulted in defects in their perineuronal nets. In the absence of sulfation motifs, the number of nets increased, changing the types of synaptic connections between neurons.

Moreover, the mice could not recognize mice they had previously been introduced to, suggesting that these patterns affect social memory, which refers to the ability to recognize familiar faces or learn new skills. The same effects were observed in both young and adult mice.

"That result suggests that it may be possible to manipulate these nets during adolescence or adulthood to potentially rewire or strengthen certain synaptic connections," says Linda Hsieh-Wilson, Ph.D., the project's principal investigator presenting the research at the meeting.

The researchers hope that the findings not yet published in a peer-reviewed journal pave the way to potential treatment for neuronal damage.

Hsieh-Wilson says: "Understanding how these molecules affect social memory could give us insights into neurodevelopmental and neuropsychiatric disorders, such autism, schizophrenia, and bipolar disorder, which are often characterized by deficits in social memory and the types of changes in the synapses, the connections that we observe this molecule produces."