2023-11-20 14:35:09
Having higher amounts of visceral fat in the abdomen — hidden fat that surrounds internal organs — in midlife appears to be linked to the development of Alzheimer’s disease. This is suggested by a study, among the main works of the next annual meeting of the Radiological Society of North America (RSNA), scheduled for November 26th in Chicago. The authors found that this hidden abdominal fat correlates with changes in the brain up to 15 years before the first symptoms of memory loss appear.
It is estimated, experts explain, that one in 5 women and one in 10 men will develop the disease during their lifetime. To try to identify risks early, the researchers evaluated the association between brain MRI volumes, as well as the uptake of amyloid and tau – proteins thought to interfere with communication between brain cells – in PET scans , and body mass index (BMI), obesity, insulin resistance, and abdominal fat in a cognitively normal middle-aged population.
“There have been other studies linking BMI with brain atrophy or even a higher risk of dementia, but no previous studies have linked a specific type of fat to the Alzheimer’s protein in cognitively normal people,” explains the author of the new research, Mahsa Dolatshahi, postdoctoral researcher at the Mallinckrodt Institute of Radiology (Mir) at Washington University School of Medicine in St. Louis. “Similar studies have not investigated the differential role of visceral and subcutaneous fat, especially in terms of Alzheimer’s amyloid pathology, already in middle age.”
For this study, researchers analyzed data from 54 cognitively healthy participants, aged between 40 and 60, with an average BMI of 32. Participants underwent glucose and insulin measurements, as well as tolerance tests to glucose. The volume of subcutaneous fat and visceral fat was with abdominal MRI. Brain MRI measured the cortical thickness of brain regions that are affected by Alzheimer’s. PET was used to examine possible pathological elements in a subgroup of 32 participants, focusing on the amyloid plaques and tau tangles that accumulate in Alzheimer’s disease.
The researchers thus found that a higher ratio of visceral to subcutaneous fat was associated with greater uptake of the amyloid PET tracer in the precuneus cortex, a region known to be affected early by amyloid pathology in Alzheimer’s disease. This relationship was worse in men than in women. The researchers also found that higher measurements of visceral fat correlated with an increased burden of inflammation in the brain. “It is suggested that different pathways play a role,” explains Dolatshahi. “The inflammatory secretions of visceral fat, as opposed to the potentially protective effects of subcutaneous fat, can lead to inflammation in the brain, a major mechanism contributing to Alzheimer’s disease.”
The study findings have several key implications for diagnosis and early intervention, notes senior author Cyrus A. Raji, associate professor of radiology and neurology and director of neuromagnetic resonance imaging at Mir. It highlights “a key mechanism through which hidden fat may increase the risk of Alzheimer’s disease,” he says. And it is shown that “such brain changes occur as early as age 50, on average, up to 15 years before the first symptoms of Alzheimer’s memory loss appear.” Raji also adds that the findings could point to visceral fat as a target for treatment to modify the risk of future brain inflammation and dementia. “By going beyond body mass index and better characterizing the anatomical distribution of body fat on MRI, we now have a better understanding of why this factor may increase the risk of Alzheimer’s disease,” he concludes.
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