High levels of visceral abdominal fat are associated with growth in midlife. Alzheimer’s disease, according to research presented next week at the annual meeting of the Radiological Society of North America (RSNA). Visceral fat is the fat around the internal organs deep in the abdomen. Researchers have found that Alzheimer’s disease is linked to changes in the brain that occur up to 15 years before the first symptoms of memory loss.
Increase in Alzheimer’s disease
According to the Alzheimer’s Association, more than 6 million Americans are living with Alzheimer’s disease. In the year By 2050, this number is expected to reach 13 million. One in five women and one in 10 men will develop Alzheimer’s disease in their lifetime.
Identifying early Alzheimer’s risk factors
In the past, to try and identify Alzheimer’s risks, researchers looked at the relationship between brain MRI volumes and amyloid and tau levels on positron emission tomography (PET) scans, body mass index (BMI), obesity, Insulin Cognitive resistance and fatty tissue in normal middle life. Amyloid and tau are proteins thought to disrupt communication between brain cells.
A special study on fat types and Alzheimer’s risk
“There have been other studies linking BMI to brain atrophy and even higher risk of dementia, although previous research has not linked a specific type of fat to the actual Alzheimer’s disease protein in cognitively normal people,” said study author Mahsa Dolatshahi, MD MPH. Postdoctoral Research Associate with the Mallinckrodt Institute of Radiology (MIR) at Washington University School of Medicine in St. Louis. “Similar studies have not yet examined the role of differences in visceral and subcutaneous fat in relation to Alzheimer’s amyloid pathology in midlife.”
Research methodology and findings
For this cross-sectional study, researchers used data from 54 cognitively healthy participants aged 40 to 60 years, with an average BMI of 32. The participants underwent glucose and insulin measurements as well as glucose tolerance tests. Subcutaneous fat (fat under the skin) and visceral fat are measured using abdominal MRI. Brain MRI measured the cortical thickness of brain regions affected by Alzheimer’s disease. PET was used to examine disease pathology in 32 participants, focusing on the amyloid plaques and tau tangles that accumulate in Alzheimer’s disease.
The researchers found that a high amyloid PET tracer was associated with a high amyloid PET tracer in a region known to be affected by amyloid pathology early in Alzheimer’s disease. This relationship was stronger in men than in women. The researchers found that higher levels of visceral fat were associated with increased inflammation in the brain.
“Several pathways are suggested to play a role,” said Dr. Dolatashahi. “In contrast to the potential protective effects of subcutaneous fat, inflammation in visceral fat may cause inflammation in the brain, one of the main mechanisms contributing to Alzheimer’s disease.
Implications for early diagnosis and intervention
Senior author Cyrus A. Raji, MD, Ph.D., associate professor of radiology and neurology and director of neuromagnetic resonance imaging at MIR, said the findings have several key implications for early diagnosis and intervention.
“This study highlights a key mechanism by which saturated fat increases the risk of Alzheimer’s disease,” he said. Such brain changes occur on average at age 50, about 15 years before the onset of Alzheimer’s memory loss symptoms.
Dr. Raji added that the results point to visceral fat as a therapeutic target to reverse brain inflammation and dementia in the future.
By better defining body fat composition on MRI, we have gone beyond body mass index and now have a significantly better understanding of why this factor increases Alzheimer’s risk, he said.
Additional co-authors include Paul K. Komman, BIE, Joseph E. Ippolito, MD, PhD, Tammy LS Benzinger, MD, PhD, and John C. Morris, MD.