Insulin resistance, brain atrophy, and cognitive performance in late middle-aged adults.
OBJECTIVE
Insulin resistance dysregulates glucose uptake and other functions in brain areas affected by Alzheimer disease. Insulin resistance may play a role in Alzheimer disease etiopathogenesis. This longitudinal study examined whether insulin resistance among late middle-aged, cognitively healthy individuals was associated with 1) less gray matter in Alzheimer disease-sensitive brain regions and 2) worse cognitive performance.


METHODS
Homeostasis model assessment of insulin resistance, gray matter volume, and the Rey Auditory Verbal Learning Test (RAVLT) were acquired in 372 participants at baseline and a consecutive subset of 121 individuals ~4 years later. Voxel-based morphometry and tensor-based morphometry were used, respectively, to test the association of insulin resistance with baseline brain volume and progressive gray matter atrophy.


RESULTS
Higher insulin resistance predicted less gray matter at baseline and 4 years later in medial temporal lobe, prefrontal cortices, precuneus, and other parietal gyri. A region-of-interest analysis, independent of the voxel-wise analyses, confirmed that higher insulin resistance was related to medial temporal lobe atrophy. Atrophy itself corresponded to cognitive deficits in the RAVLT. Temporal lobe atrophy that was predicted by higher insulin resistance significantly mediated worse RAVLT encoding performance.


CONCLUSIONS
These results suggest that insulin resistance in an asymptomatic, late middle-aged cohort is associated with progressive atrophy in regions affected by early Alzheimer disease. Insulin resistance may also affect the ability to encode episodic information by negatively influencing gray matter volume in medial temporal lobe.
Geriatric Research Education and Clinical Center, William S. Middleton Memorial Veterans Hospital, Madison, WI, USA.
Auriel A
AA
Willette
Guofan
G
Xu
Sterling C
SC
Johnson
Alex C
AC
Birdsill
Erin M
EM
Jonaitis
Mark A
MA
Sager
Bruce P
BP
Hermann
Asenath
A
La Rue
Sanjay
S
Asthana
Barbara B
BB
Bendlin
D000368:Aged; D001284:Atrophy / Q000378:metabolism / Q000503:physiopathology*; D001927:Brain Diseases / Q000378:metabolism / Q000503:physiopathology*; D001931:Brain Mapping; D003071:Cognition / Q000502:physiology*; D005260:Female; D005838:Genotype; D006801:Humans; D007333:Insulin Resistance / Q000502:physiology*; D008297:Male; D008875:Middle Aged