The presence of a specific type of fat, known as visceral fat, in midlife can predict risk for Alzheimer’s disease in later years, according to research led by Washington University School of Medicine.
Obesity between the age of 40 and 60 years is known to be linked to increased risk for Alzheimer’s disease, but the way obesity increases this risk is not totally clear.
To investigate this further, Mahsa Dolatshahi, post-doctoral research associate at Mallinckrodt Institute of Radiology at the Washington University School of Medicine, and colleagues aimed to assess the impact of different types and locations of fat around the body, as well as other metabolic factors on amyloid brain levels.
Although people in midlife do not typically show signs of Alzheimer’s disease, amyloid levels in the brain can be a good indicator of who is at highest risk of going on to develop the neurodegenerative condition.
The study, which was presented at the annual meeting of the Radiological Society of North America, included 80 midlife individuals who were cognitively normal on enrollment. The average age was 49 years, 63% were female, and 58% were obese (BMI over 30 kg/m2). Magnetic resonance imaging (MRI) was used to measure body fat distribution and positron emission tomography (PET) scanning to measure whole-brain amyloid burden.
Using the centiloid scale to measure amyloid burden, participants with obesity had a higher score than participants without obesity. Centiloid scale score was also significantly associated with the presence of visceral adipose tissue, a hormonally active component of body fat, found mostly in the abdomen, which is able to influence other physiological processes around the body through biochemical signaling.
To a smaller degree, insulin resistance, BMI, and subcutaneous fat were also linked to higher amyloid levels, but liver and thigh fat were not.
The researchers estimated that the link with visceral fat accounted for about 77% of the effect of high BMI or obesity on amyloid accumulation.
“This crucial result was discovered because we investigated Alzheimer’s disease pathology as early as midlife—in the 40s and 50s—when the disease pathology is at its earliest stages, and potential modifications like weight loss and reducing visceral fat are more effective as a means of preventing or delaying the onset of the disease,” said study author Dolatshahi in a press statement.
“A key implication of our work is that managing Alzheimer’s risk in obesity will need to involve targeting the related metabolic and lipid issues that often arise with higher body fat,” added study co-author Cyrus Raji, MD, PhD, associate professor of radiology at Mallinckrodt Institute of Radiology.
The same team of researchers have also looked at how visceral fat can impact the brain in another recent study. They found that higher visceral fat reduces cerebral blood flow in the brain, which could help explain the higher levels of amyloid found in these individuals.
