Visceral abdominal fat in midlife linked to Alzheimer’s disease

Key takeaways:

• Researchers found lower white matter volumes in patients with obesity and insulin resistance vs. those who were metabolically healthy.
• The study was limited by its sample size of 34 participants.

Having a higher amount of visceral abdominal fat in middle age was associated with an increased risk for developing Alzheimer’s disease, according to research presented at the annual meeting of the Radiological Society of North America.

“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,” Mahsa Dolatshahi, MD, MPH, a, post-doctoral research fellow at the Mallinckrodt Institute of Radiology (MIR) at Washington University School of Medicine in St. Louis, said in a press release.

According to Dolatshahi, “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.”

Dolatshahi and colleagues analyzed data on 34 cognitively healthy adults aged 40 to 61 years, who had a mean BMI of 32.28 kg/m². The researchers tested participants for glucose tolerance and insulin resistance, and used an abdominal MRI to assess volumes of visceral fat (VAT) and subcutaneous fat (SAT).

Dolatshahi and colleagues reported finding lower right entorhinal white matter volume, which is “involved in relaying information to the hippocampus,” in participants with obesity and insulin resistance vs. those without obesity (P = .004).

They also reported that higher amyloid positron emission tomography tracer uptake in the precuneus brain region was linked to a greater VAT/SAT ratio, “a marker of visceral obesity.” The association was stronger in men, the released noted. In addition, Dolatshahi and colleagues found that higher visceral fat measurements were associated with an increased burden of inflammation in the brain.

“Several pathways are suggested to play a role,” Dolatshahi said. “Inflammatory secretions of [VAT] — as opposed to potentially protective effects of [SAT] — may lead to inflammation in the brain, one of the main mechanisms contributing to Alzheimer's disease.”

Cyrus A. Raji, MD, PhD, an associate professor of radiology and neurology at MIR and senior author of the study, said in the release that the findings have multiple implications for physicians, such as earlier diagnoses.

“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 average — up to 15 years before the earliest memory loss symptoms of Alzheimer’s occur.”

The findings also indicate that visceral fat could be used as a future treatment target, Raji added.

“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 risk for Alzheimer's disease,” he said.

References:

• Hidden belly fat in midlife linked to Alzheimer’s disease. https://press.rsna.org/timssnet/media/pressreleases/14_pr_target.cfm?id=2467. Published Nov. 20, 2023. Accessed Nov. 20, 2023.
• Dolatshahi M, et al. Visceral abdominal adipose tissue and insulin resistance respectively influence Alzheimer’s disease amyloid pathology and neurodegeneration in midlife. Presented at: Radiology Conference & Annual Meeting; Nov. 26-30, 2023; Chicago.