Potential link between vitamin D deficiency and loss of brain plasticity

Research from the University of Queensland could explain why vitamin D is vital for brain health and how deficiency causes disorders such as depression and schizophrenia.

Associate Professor Thomas Burne of the Queensland Brain Institute of UQ led the studies that lay the groundwork for research on improving prevention and treatments.

"More than a billion people in the world suffer from vitamin D deficiency and there is a well-established link between vitamin D deficiency and cognitive impairment," said Dr. Burne.

"Unfortunately, it's unclear how vitamin D influences the structure and function of the brain, so we do not know why deficiency causes problems."

Dr. Burne's team discovered that vitamin D levels affect a type of "scaffolding" in the brain, called the perineuronal network.

"These networks constitute a strong and favorable mesh around certain neurons and, in doing so, they stabilize the contacts that these cells establish with other neurons," he said.

The researchers removed vitamin D from the diet of a group of healthy adult mice and, after 20 weeks, found a significant decrease in their ability to memorize and learn compared to a control group.

Dr. Burne explained that the vitamin D deficient group exhibited a pronounced reduction in perineuron networks in the hippocampus, the crucial brain region for memory formation.

"There was also a clear reduction in the number and strength of connections between neurons in this region."

Dr. Burne's team believes that vitamin D plays an important role in the stability of perineuronal networks and that when vitamin D levels decrease, this "scaffold" is more easily degraded by enzymes.

"While hippocampal neurons lose their perineuronal networks, they have trouble maintaining their connections, which results in a loss of cognitive function."

Associate Professor Burne said that the hippocampus could be the most strongly affected by vitamin D deficiency because it is much more active than other brain regions.

"It's a bit like the canary in the coal mine: it's possible that it fails first because its high energy requirement makes it more sensitive to the depletion of essential nutrients like vitamin D.

"Curiously, the right side of the hippocampus was more affected by vitamin D deficiency than the left side."

Associate Professor Burne said that loss of function in this area could be an important factor in schizophrenia, including severe memory deficits and a distorted perception of reality.

"The next step is to test this new hypothesis on the link between vitamin D deficiency, perineuronal nets and cognition," he said.

"We are also particularly pleased to have discovered that these nets can change in adult mice.

"I hope that because they are dynamic, there is a chance that we can rebuild them, which could pave the way for new treatments."

The research is published in Structure and function of the brain and Trends in neuroscience.

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University of Queensland