Midlife’s Hidden Adiposity: An Unexpected Connection to Alzheimer’s


Research that will be presented at the Radiological Society of North America (RSNA) annual conference next week suggests that higher levels of visceral belly fat in midlife are linked to the development of Alzheimer’s disease. Visceral fat is the fat that surrounds the internal organs, which are found deep within the belly. Researchers have discovered a connection between this concealed belly fat and brain changes that may manifest up to 15 years before the earliest symptoms of Alzheimer’s disease, such memory loss.

The Alzheimer’s Association estimates that over 6 million Americans have Alzheimer’s disease. By 2050, this number is predicted to rise to over 13 million. One in five women and one in ten men will at some point in their lives experience Alzheimer’s disease.

In an attempt to predict Alzheimer’s disease risk in advance, scientists examined the relationship between brain MRI volumes, body mass index (BMI), obesity, insulin resistance, and abdominal adipose (fatty) tissue in a group of midlife cognitively normal individuals, as well as amyloid and tau uptake on positron emission tomography (PET) scans. Proteins called tau and amyloid are considered to obstruct brain cell communication.

No previous study has connected a particular type of fat to the Alzheimer’s disease protein in cognitively normal individuals, despite other studies connecting BMI with brain atrophy or even a higher risk of dementia, according to study author Mahsa Dolatshahi, M.D., M.P.H., a post-doctoral research fellow with the Mallinckrodt Institute of Radiology (MIR) at Washington University School of Medicine in St. Louis. “The distinct roles of visceral and subcutaneous fat, particularly in terms of Alzheimer’s amyloid pathology, as early as midlife, have not been examined in similar studies.”

Researchers examined data from 54 cognitively healthy individuals with an average BMI of 32 who were between the ages of 40 and 60 for this cross-sectional study.

In addition to glucose tolerance testing, the participants had their insulin and glucose levels measured. Abdominal magnetic resonance imaging was used to quantify the amount of visceral and subcutaneous fat, or fat under the skin. The cortical thickness of the Alzheimer’s disease-affected brain areas was assessed using brain MRI. A group of 32 individuals underwent PET examination to look at the disease pathology, with particular attention to tau tangles and amyloid plaques that build up in Alzheimer’s patients.

The precuneus cortex, which is known to be impacted early by amyloid pathology in Alzheimer’s disease, showed increased amyloid PET tracer absorption in correlation with a larger visceral to subcutaneous fat ratio, the researchers discovered. For men, this association was worse than for women.

The researchers also discovered a link between elevated brain inflammatory burden and greater visceral fat measurements.

Dr. Dolatshahi stated, “Several pathways are suggested to play a role.” “Inflammatory secretions of visceral fat may cause inflammation in the brain, one of the main mechanisms contributing to Alzheimer’s disease, as opposed to potentially protective effects of subcutaneous fat.”

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