According to the Alzheimer’s Association, about 6.7 million Americans have Alzheimer’s disease. This figure is expected to climb to approximately 13.8 million by 2060 (2). Alzheimer’s disease affects one out of every five women and one out of every ten males in their lifetime (3).
Researchers investigated the relationship between brain MRI volumes, as well as amyloid and tau uptake on positron emission tomography (PET) scans, and body mass index (BMI), obesity, insulin resistance, and abdominal adipose (fatty) tissue in a cognitively normal midlife population. Amyloid and tau proteins are thought to disrupt communication between brain cells.
“Even though there have been other studies linking BMI with brain atrophy or even a higher dementia risk, no prior study has linked a specific type of fat to the actual Alzheimer’s disease protein in cognitively normal people,” said study author Mahsa Dolatshahi, M.D., M.P.H., a post-doctoral research fellow with 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, as early as midlife.”
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Researchers analyzed data from 54 cognitively healthy people ranging in age from 40 to 60 years old, with an average BMI of 32, for this cross-sectional study. Glucose and insulin levels were measured, as well as glucose tolerance tests, on the subjects. Abdominal MRI was used to determine the volume of subcutaneous fat (fat beneath the skin) and visceral fat. The cortical thickness of brain regions affected by Alzheimer’s disease was assessed using brain MRI. PET imaging was utilized to investigate disease pathology in a subset of 32 people, with a focus on amyloid plaques and tau tangles that build in Alzheimer’s disease.
Higher Visceral Fat Levels Increase Brain Inflammation
The researchers discovered that a larger visceral to subcutaneous fat ratio was related to higher amyloid PET tracer absorption in the precuneus cortex, which is known to be damaged early in Alzheimer’s disease by amyloid pathology. Men had a worse connection than women. The researchers also discovered that larger levels of visceral fat are associated with an increased load of inflammation in the brain.
“Several pathways are suggested to play a role,” Dr. Dolatshahi said. “Inflammatory secretions of visceral fatas opposed to potentially protective effects of subcutaneous fatmay lead to inflammation in the brain, one of the main mechanisms contributing to Alzheimer’s disease.”
Visceral Fat: Possible Therapy Target for Reducing Risk of Dementia
The findings have several important implications for earlier diagnosis and intervention, according to senior author Cyrus A. Raji, M.D., Ph.D., associate professor of radiology and neurology, and director of neuromagnetic resonance imaging at MIR.
“This study highlights a key mechanism by which hidden fat can increase the risk of Alzheimer’s disease,” he said. “It shows that such brain changes occur as early as age 50, on averageup to 15 years before the earliest memory loss symptoms of Alzheimer’s occur.”
Dr. Raji went on to say that the findings could lead to visceral fat as a therapy target for reducing the risk of future brain inflammation and dementia. “By moving beyond body mass index in better characterizing the anatomical distribution of body fat on MRI, we now have a uniquely better understanding of why this factor may increase the risk for Alzheimer’s disease,” he said.
References:
- Hidden belly fat in midlife linked to Alzheimer’s disease
https:www.eurekalert.org/news-releases/1007871 - 2023 Alzheimer’s disease facts and figures
2023 Alzheimer’s disease facts and figures. Alzheimers Dement. 2023 Apr;19(4):1598-1695. doi: 10.1002/alz.13016. Epub 2023 Mar 14. PMID: 36918389. - Sex differences in Alzheimer’s disease
Schmidt R, Kienbacher E, Benke T, Dal-Bianco P, Delazer M, Ladurner G, Jellinger K, Marksteiner J, Ransmayr G, Schmidt H, Stögmann E, Friedrich J, Wehringer C. Geschlechtsspezifische Unterschiede der Alzheimer Demenz [Sex differences in Alzheimer’s disease]. Neuropsychiatr. 2008;22(1):1-15. German. PMID: 18381051.
Source: Medindia
