Does the Stress Hormone Impact Memory and Learning In Diabetics?
Diabetes is known to impair the cognitive health of people, but now scientists have identified one potential mechanism underlying these learning and memory problems. A new study in diabetic rodents finds that increased levels of a stress hormone produced by the adrenal gland disrupt the healthy functioning of the hippocampus, the region of the brain responsible for learning and short-term memory. Moreover, when levels of the adrenal glucocorticoid hormone corticosterone (also known as cortisol in humans) are returned to normal, the hippocampus recovers its ability to build new cells and regains the “plasticity” needed to compensate for injury and disease and adjust to change.
The study appears in the Feb. 17, 2008, issue of Nature Neuroscience and
was conducted bythe National Institute on Aging (NIA), part of the
National Institutes of Health (NIH). NIA’s Mark Mattson, Ph.D., and
colleagues in the Institute’s Intramural Research Program performed the
study with Alexis M. Stranahan, a graduate student at Princeton
University in New Jersey. “This research in animal models is intriguing, suggesting the
possibility of novel approaches in preventing and treating cognitive
impairment by maintaining normal levels of glucocorticoid,” said
Richard J. Hodes, M.D., NIA director. “Further study will provide a
better understanding of the often complex interplay between the nervous
system, hormones and cognitive health.” Cortisol production is controlled by the hypothalamic-pituitary axis
(HPA), a hormone-producing system involving the hypothalamus and
pituitary gland in the brain and the adrenal gland located near the
kidney. People with poorly controlled diabetes often have an overactive
HPA axis and excessive cortisol produced by the adrenal gland. To study
the interaction between elevated stress hormones and the hippocampal
function, researchers tested the cognitive abilities and examined the
brain tissue in animal models of rats with Type 1 diabetes (insulin
deficient) and mice with Type 2 diabetes (insulin resistant). Researchers found that diabetic animals in both models exhibited
learning and memory deficits when cortisol levels were elevated due to
impaired plasticity and declines in new cell growth. Returning the
levels to normal, however, reversed the negative impact on the
hippocampus and restored learning and memory. “This advance in our understanding of the physiological changes
caused by excessive production of cortisol may eventually play a role
in preventing and treating cognitive decline in diabetes,” said
Mattson, who heads the NIA’s Laboratory of Neurosciences. He and
Stranahan explained these findings may also help explain the connection
between stress-related mood disorders and diabetes found in human
population studies.
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Sources: National Insititute of Mental Health, See also blogposts in Psychiatric Disorders: General and Psychiatric Disorders: Aging
Dr. Jeffrey Speller
Dr. Tanya Korkosz
Psychopharmacology Associates of New England
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