Insulin resistance marks Alzheimer's disease risk at the earliest stage
An important paper recently published in the Archives of Neurology offers evidence that insulin resistance is a causal factor for Alzheimer's disease at its earliest stages. The authors observe:
"Insulin resistance is a causal factor in prediabetes (PD) and type 2 diabetes (T2D) and increases the risk of developing Alzheimer disease (AD). Reductions in cerebral glucose metabolic rate (CMRglu) as measured by fludeoxyglucose F 18–positron emission tomography (FDG-PET) in parietotemporal, frontal, and cingulate cortices are associated with increased AD risk and can be observed years before dementia onset."
With this in mind they set out to...
"...examine whether greater homeostasis model assessment insulin resistance (HOMA-IR) is associated with reduced resting CMRglu in areas vulnerable in AD in cognitively normal adults with newly diagnosed PD or T2D (PD/T2D), and to determine whether adults with PD/T2D have abnormal patterns of CMRglu during a memory encoding task."
In other words, the authors correlated glucose and insulin measurements, brain scans of glucose metabolism and a radioactive emission brain scan (fludeoxyglucose F 18–positron emission tomography) during a memory encoding task. What did the data show?
"Greater insulin resistance was associated with an AD-like pattern of reduced CMRglu in frontal, parietotemporal, and cingulate regions in adults with PD/T2D...During the memory encoding task, healthy adults showed activation in right anterior and inferior prefrontal cortices, right inferior temporal cortex, and medial and posterior cingulate regions. Adults with PD/T2D showed a qualitatively different pattern during the memory encoding task, characterized by more diffuse and extensive activation, and recalled fewer items on the delayed memory test."
The authors' conclusion adds to the weight of evidence indicating that blood sugar dysregulation and insulin resistance are fundamental causal factors and early risk indicators for Alzheimer's disease:
"Insulin resistance may be a marker of AD risk that is associated with reduced CMRglu and subtle cognitive impairments at the earliest stage of disease, even before the onset of mild cognitive impairment."