Can body fat at age 40 influence the occurrence of Alzheimer’s disease decades later? This is what scientists from the Washington university school of Medicine from St. Louis, Missouri. More broadly, their work, presented at the annual meeting of the Radiological Society of North America (RSNA), looked at the links between modifiable factors linked to lifestyle – obesity, distribution of body fat, metabolism – and Alzheimer’s disease. Results ? Visceral fat, the deep fat located under the abdominal muscles, around the liver, stomach and intestines, is closely linked to the onset of the first symptoms almost 20 years later.
Subcutaneous fat or visceral fat: a very different brain condition
80 people aged 49 on average and with normal cognitive abilities participated in the study. 57.5% of participants were obese and the average body mass index (BMI) was 32.31. All underwent a body MRI and metabolic assessment (glucose and insulin measurements), as well as a lipid panel (cholesterol).
MRI scans of the abdomen were performed to measure the volume of subcutaneous fat (the fat under the skin) and the volume of visceral fat. Early brain markers of Alzheimer’s disease – the accumulation of TAU protein and amyloid plaques in the brain – were measured via brain positron emission tomography (PET) scan (a test that provides precise images in three dimensions). The more these rates increase, the more the disease progresses.
“Our study showed that higher visceral fat was associated with higher PET levels of the two pathological proteins characteristic of Alzheimer’s disease, amyloid and tau,” analyzes Dr Mahsa Dolatshahi, lead author of the study.
Visceral fat associated with poorer blood circulation
By what mechanism does visceral fat influence the accumulation of TAU protein and amyloid plaques in the brain? It seems that we must look at the side of blood circulation. Researchers performed brain and abdominal MRI on cognitively normal middle-aged individuals with a wide range of BMIs and compared blood flow on brain MRI in individuals with high or low visceral or subcutaneous fat. . The group with high visceral fat showed lower cerebral blood flow. No significant differences in cerebral blood flow were observed in the group with high or low subcutaneous fat.
Other metabolic factors involved, such as good cholesterol
Additionally, higher insulin resistance and HDL cholesterol (the good cholesterol) were associated with higher amyloid levels in the brain. And higher levels of good cholesterol appeared to reduce the effects of visceral fat on the development of Alzheimer’s. “A key implication of our work is that managing Alzheimer’s risk in obesity will need to involve targeting the associated metabolic and lipid problems that often occur with high body fat,” said lead study author Cyrus A. Raji, associate professor of radiology at the Mallinckrodt Institute of Radiology (MIR) at Washington University School of Medicine.
Reducing abdominal fat: a way to prevent Alzheimer’s?
“This crucial result was discovered because we studied the pathology of Alzheimer’s disease as early as the 40s and 50s, when the pathology is in its early stages. Potential changes like weight loss and reduction of visceral fat are more effective in preventing or delaying the onset of the disease,” abonde Mahsa Dolatshahi.
Some 6.9 million Americans aged 65 and older suffer from Alzheimer’s disease. According to The Alzheimer Association, this number could rise to 13 million by 2050 if no advances can be made to prevent or cure the disease. And according to another study published in The Lancetin 2021, in the United States, 208 million people (out of 334 million) were considered overweight or obese.
Source : Radiological Society of north America, Hidden Fat Predicts Alzheimer’s 20 Years Ahead of Symptoms, 2 décembre 2024
