New research from the Multimodal Neuroimaging for AD Diagnosis (MULNIAD) study, implemented at the National Center for Geriatrics and Gerontology (NCGG), showed the association between decreased glucose metabolism in the medial prefrontal areas and Alzheimer's disease-related weight loss, and reduced fat mass might take part in it. The study published in the Journal of Alzheimer's Disease

The underlying mechanism of weight loss in people with Alzheimer's disease (AD) was not clear.  Dr. Takashi Sakurai, head of the Memory Clinic at the NCGG said, "This study is a very important study to help understand the underlying mechanism of weight loss in patients with mild cognitive impairment and Alzheimer's disease."

The present study for the first time used multi-imaging modalities and explained that the nutritional status associated with AD-related brain changes comprehensively. Multi-imaging modalities comprise amyloid-β (Aβ)- positron emission tomography (PET), 18F-fluorodeoxyglucose (FDG)-PET, and structural magnetic resonance imaging.

The study involved Aβ-positive people (n=34) with mild cognitive impairment or early AD (prodromal/early AD), and Aβ-negative people (n=55) cognitively normal (CN).  Multiple regression analysis by using statistical parametric mapping examined the link between nutritional status (body mass index, waist to height ratio, fat mass index, and fat-free mass index) and brain changes.    

Considerably positive correlation between nutritional status and regional cerebral glucose metabolism (rCGM) in the medial prefrontal cortices was seen in the prodromal/early AD group, whereas different topographical associations were seen in the CN group. However, correlation between nutritional status and Aβ deposition, gray matter volume were not found. Sub-analysis revealed that fat mass index was positively associated with rCGM in the medial prefrontal areas in the prodromal/early AD group.   

Dr. Takashi Sakurai said, “These results suggest that hypometabolism in the medial prefrontal areas is specifically associated with AD-related weight loss, and a decrease in fat mass may have a key role.” The cross-sectional study provided preliminary results, hence further research about the fat tissue metabolism including adipokines is required to understand the relationship between AD and weight loss, he added. The significant association between a fat-mass index and rCGM was maintained after modifying cognitive function.

It was concluded that the study results of reduced glucose metabolism in medial prefrontal areas in Aβ-positive people might clarify the underlying mechanism of weight loss in AD.