A surprising link to Alzheimer’s disease

Higher amounts of abdominal visceral fat in middle age are associated with the development of… Alzheimer’s disease The disease, according to research that will be presented next week at the annual meeting of the Radiological Society of North America (RSNA). Visceral fat is the fat that surrounds the internal organs deep in the abdomen. The researchers found that this hidden belly fat was linked to changes in the brain up to 15 years before the early memory loss symptoms of Alzheimer’s disease appeared.

High prevalence of Alzheimer’s disease

According to the Alzheimer’s Association, there are more than 6 million Americans living with Alzheimer’s disease. By 2050, this number is expected to rise to nearly 13 million. One in five women and one in 10 men will develop Alzheimer’s disease in their lifetime.

Identifying early risks of Alzheimer’s disease

To try to determine Alzheimer’s risk earlier, researchers evaluated the relationship between brain MRI volumes, as well as amyloid and tau uptake on positron emission tomography (PET), with body mass index (BMI), obesity, and Alzheimer’s disease. Insulin Resistance and abdominal adipose (adipose) tissue in a cognitively normal middle-aged population. Amyloid and tau are two proteins that are thought to interfere with communication between brain cells.

This figure shows increased neuroinflammation (yellow colors) associated with higher hidden fat (visceral fat) in a group of 54 participants with an average age of 50 years in the brain’s white matter. The green colors are the normal white material. Image credit: RSNA/Mahsa Dolatshahi, MD, MPH

A unique study on types of fats and the risk of Alzheimer’s disease

“Although there are other studies linking BMI to brain atrophy or even a higher risk of dementia, no previous study has linked a specific type of fat to the actual Alzheimer’s disease protein in cognitively normal people,” said study author Masa Dolatshahi, MD. . MPH, a postdoctoral research fellow at the Mallinckrodt Institute of Radiology (MIR) at Washington University School of Medicine in St. Louis. “Similar studies have not looked at the differential role of visceral fat and subcutaneous fat, particularly in relation to Alzheimer’s amyloid disease, in early midlife.”

Study methodology and results

In this cross-sectional study, researchers analyzed data from 54 cognitively healthy participants, aged 40 to 60 years, with an average BMI of 32. Participants underwent glucose and insulin measurements, as well as glucose tolerance tests. The volume of subcutaneous fat (subcutaneous fat) and visceral fat was measured using abdominal MRI. Brain MRI measured the cortical thickness of brain areas affected by Alzheimer’s disease. PET was used to examine disease pathology in a subset of 32 participants, focusing on amyloid plaques and tau tangles that accumulate in Alzheimer’s disease.

The researchers found that a higher ratio of visceral fat to subcutaneous fat was associated with higher amyloid PET uptake in the precuneus, an area known to be affected early in amyloid pathology in Alzheimer’s disease. This relationship was worse for men than for women. The researchers also found that higher visceral fat measurements are associated with an increased burden of inflammation in the brain.

“Several pathways have been suggested to play a role,” Dr. Dolatshahi said. “Inflammatory secretions of visceral fat—in contrast to the potentially protective effects of subcutaneous fat—may lead to inflammation in the brain, one of the major mechanisms contributing to Alzheimer’s disease.”

Implications for early diagnosis and intervention

Lead author Cyrus A. Raji, MD, associate professor of radiology and neuroscience, and director of neuromagnetic resonance imaging at MIR, noted that the findings have several key implications for early diagnosis and intervention.

“This study highlights the key mechanism by which hidden fat may increase the risk of developing Alzheimer’s disease,” he said. “It shows that such brain changes occur as early as age 50, on average, up to 15 years before the early memory loss symptoms of Alzheimer’s disease appear.”

Dr Raji added that the findings may point to visceral fat as a therapeutic target to modify the risk of encephalitis and dementia in the future.

“By going beyond BMI in better characterizing the anatomical distribution of body fat on MRI, we now have a uniquely better understanding of why this factor increases the risk of developing Alzheimer’s disease,” he said.

Additional co-authors are Paul K. Comyn, P. E., Joseph E. Ippolito, MD, PhD, Tami L. S. Benzinger, MD, PhD, and John C. Morris, MD