Potential utility of salivary gland amyloid uptake as a surrogate marker for adipose tissue and amyloid-beta dynamics based on its association with BMI and cerebral amyloid burden.

Recent studies have noted an unexpected inverse correlation between body mass index (BMI) and cerebral amyloid-beta (Aβ) deposition, suggesting a potential involvement of adipose tissue in AD pathology. Given the adipose-rich nature of salivary glands, we investigated whether Aβ uptake in the salivary glands is associated with the link between BMI and cerebral Aβ deposition using18F-Florbetaben PET/CT. We analyzed data from 187 participants, classified into Aβ-cognitively normal (Aβ-CN), Aβ+ mild cognitive impairment (Aβ+MCI), and Aβ+ AD dementia (Aβ+D) groups. BMI, standardized uptake value ratio of salivary glands (SUVRSG), and brain (SUVRB) were quantified, and their associations were examined using Pearson correlation and multiple regression analyses. Higher BMI was correlated with increased SUVRSG (r = 0.231, p = 0.0019) and decreased SUVRB (r = -0.247, p = 0.0009). SUVRSG and SUVRB were negatively correlated (r = -0.188, p = 0.0102). Multiple regression analysis identified BMI as an independent predictor of composite brain SUVR (β = -0.0168, p = 0.0046), while SUVRSG was marginally significant (β = -0.0714, p = 0.0701). Regionally, both BMI and SUVRSG were significantly associated with lower SUVRB in the striatum, precuneus, and cingulate cortex. Consistent with previous studies, BMI exhibited an inverse correlation with SUVRB. Notably, SUVRSG was negatively associated with SUVRB while demonstrating a positive correlation with BMI. Interpreting SUVRSG as a fat-related marker, these findings suggest that Aβ sequestration in adipose tissue may contribute to lower cerebral Aβ accumulation. Additional research is necessary to elucidate the underlying mechanism.