Reduced gray matter volume in the default-mode network associated with insulin resistance

Insulin resistance may lead to structural and functional abnormalities of
the human brain. However, the mechanism by which insulin resistance
impairs the brain remains elusive. In this study, we used two large
neuroimaging databases to investigate the brain regions where insulin
resistance was associated with the gray matter volume and to examine the
resting-state functional connectivity between these brain regions and each
hypothalamic nucleus. Insulin resistance was associated with reduced gray
matter volume in the regions of the default-mode and limbic networks in
the cerebral cortex in older adults. Resting-state functional connectivity
was prominent between these networks and the paraventricular nucleus of
the hypothalamus, a hypothalamic interface connecting functionally with
the cerebral cortex. Furthermore, we found a significant correlation in
these networks between insulin resistance-related gray matter volume
reduction and network paraventricular nucleus of the hypothalamus
resting-state functional connectivity. These results suggest that insulin
resistance-related gray matter volume reduction in the default-mode and
limbic networks emerged through metabolic homeostasis mechanisms in the
hypothalamus.