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Cortisol Linked to Cognitive Impairments in Diabetic Rodents
> 2/20/2008 12:48:03 PM

The hypothalamic-pituitary-adrenal axis (HPA), a hormone-producing system involving the brain and adrenal glands, is often overactive in patients with poorly controlled diabetes, leading to elevated levels of cortisol. According to research appearing in the February issue of Nature Neurology, elevated cortisol levels may underly the cognitive deficits associated with diabetes. By studying animal models of diabetes, the team of researchers from the National Institute on Aging found that cortisol can impair functioning of the hippocampus, resulting in some cognitive deficits.

The researchers tested cortisol's effect on the cognitive functioning of insulin deficient rats (an animal model for type 1 diabetes) and insulin resistant mice (an animal model for type 2 diabetes). In both groups, elevated cortisol levels had an adverse effect on the hippocampus, impairing its ability to generate new cells and affecting its synaptic plasticity. These changes could negatively affect the brain's ability to compensate and adjust for disease, injury, or other problems, and the researchers observed that rodents with these cognitive changes displayed deficits in learning and memory. By decreasing cortisol production so that cortisol levels returned to normal, the researchers were able to reverse the changes seen in the hippocampus and repair the observed deficits in learning and memory.

These results suggest that some cognitive impairments associated with diabetes may stem from changes in the hippocampus caused by increased levels of cortisol, and further study on the effect of cortisol on cognition may be beneficial. By understanding exactly how this stress hormone alters the hippocampus, affecting learning and memory, we may be able to develop effective treatments designed to counter the effect of cortisol on the brain. It may also be helpful to make those with diabetes aware of these potential issues so that they can better monitor their disorder. Researchers must continue to investigate cortisol's impact on cognition and determine what treatments might be able to reverse or prevent its effects on the cognitive abilities of individuals with diabetes.

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