Background: Despite the known associations between zinc levels and Alzheimer’s disease (AD) dementia and related cognitive impairment, the underlying neuropathological links remain poorly understood. We tested the hypothesis that serum zinc level is associated with cerebral beta-amyloid protein (Aβ) deposition. Additionally, we explored associations between serum zinc levels and other AD pathologies [i.e., tau deposition and AD-signature cerebral glucose metabolism (AD-CM)] and white matter hyperintensities (WMHs), which are measures of cerebrovascular injury. Methods: A total of 241 cognitively normal older adults between 55 and 90 years of age were enrolled. All the participants underwent comprehensive clinical assessments, serum zinc level measurement, and multimodal brain imaging, including Pittsburgh compound B-positron emission tomography (PET), AV-1451 PET, fluorodeoxyglucose (FDG)-PET, and magnetic resonance imaging. Zinc levels were stratified into three categories: < 80 μg/dL (low), 80 to 90 μg/dL (medium), and > 90 μg/dL (high). Results: A low serum zinc level was significantly associated with increased Aβ retention. In addition, apolipoprotein E ε4 allele (APOE4) status moderated the association: the relationship between low zinc level and Aβ retention was significant only in APOE4 carriers. Although a low zinc level appeared to reduce AD-CM, the relationship became insignificant on sensitivity analysis including only individuals with no nutritional deficiency. The serum zinc level was associated with neither tau deposition nor the WMH volume. Conclusions: Our findings suggest that decreased serum zinc levels are associated with elevation of brain amyloid deposition. In terms of AD prevention, more attention needs to be paid to the role of zinc.

Background: Hypertension has been associated with Alzheimer’s disease (AD) dementia as well as vascular dementia. However, the underlying neuropathological changes that link hypertension to AD remain poorly understood. In our study, we examined the relationships of a history of hypertension and high current blood pressure (BP) with in vivo AD pathologies including β-amyloid (Aβ) and tau and also investigated whether a history of hypertension and current BP respectively affect the association between Aβ and tau deposition. Methods: This cross-sectional study was conducted as part of the Korean Brain Aging Study for Early Diagnosis and Prediction of Alzheimer’s Disease, a prospective cohort study. Cognitively normal older adults who underwent both Aβ and tau positron emission tomography (PET) (i.e., [¹¹C]-Pittsburgh compound B and [¹⁸F] AV-1451 PET) were selected. History of hypertension and current BP were evaluated and cerebral Aβ and tau deposition measured by PET were used as main outcomes. Generalized linear regression models were used to estimate associations. Results: A total of 68 cognitively normal older adults (mean [SD] age, 71.5 [7.4] years; 40 women [59%]) were included in the study. Neither a history of hypertension nor the current BP exhibited a direct association with Aβ or tau deposition. However, the synergistic interaction effects of high current systolic (β, 0.359; SE, 0.141; p = 0.014) and diastolic (β, 0.696; SE, 0.158; p < 0.001) BP state with Aβ deposition on tau deposition were significant, whereas there was no such effect for a history of hypertension (β, 0.186; SE, 0.152; p = 0.224). Conclusions: The findings suggest that high current BP, but not a history of hypertension, synergistically modulate the relationship between cerebral Aβ and tau deposition in late-life. In terms of AD prevention, the results support the importance of strict BP control in cognitively normal older adults with hypertension.

The neuropathological links underlying the association between changes in liver function and AD have not yet been clearly elucidated. We aimed to examine the relationship between liver function markers and longitudinal changes in Alzheimer's disease (AD) core pathologies. Data from the Korean Brain Aging Study for the Early Diagnosis and Prediction of Alzheimer's Disease, a longitudinal cohort study initiated in 2014, were utilized. Community and memory clinic setting. Three hundred forty-seven older adults. Participants underwent baseline and 2-year follow-up evaluations, including liver function assessments and various brain imaging techniques, such as amyloid and tau PET, FDG-PET, and MRI). Liver function indicators [alanine aminotransferase (ALT), aspartate aminotransferase (AST), and total bilirubin] were examined as exposure variables. Higher baseline ALT levels were associated with a greater increase in beta-amyloid deposition over 2 years [β = 0.166, Bonferroni-corrected P (P_B) = 0.012], while lower total bilirubin levels were associated with a greater increase in tau deposition over the same period (β = -0.570, P_B < 0.001). In contrast, AST alone showed no significant association with changes of AD pathologies. The findings suggest a possible link between lower liver function and the accumulation of core AD pathologies in the brain. These results also support the possibility that the liver-brain axis could be a potential target for therapeutic or preventive strategies against AD.

Background: Low body mass index (BMI) or underweight status in late life is associated with an increased risk of dementia or Alzheimer’s disease (AD). However, the relationship between late-life BMI and prospective longitudinal changes of in-vivo AD pathology has not been investigated. Methods: This prospective longitudinal study was conducted as part of the Korean Brain Aging Study for Early Diagnosis and Prediction of Alzheimer’s Disease (KBASE). A total of 194 cognitive normal older adults were included in the analysis. BMI at baseline was measured, and two-year changes in brain Aβ and tau deposition on PET imaging were used as the main outcomes. Linear mixed-effects (LME) models were used to examine the relationships between late-life BMI and longitudinal change in AD neuropathological biomarkers. Results: A lower BMI at baseline was significantly associated with a greater increase in tau deposition in AD-signature region over 2 years (β, -0.018; 95% CI, -0.028 to -0.004; p = .008), In contrast, BMI was not related to two-year changes in global Aβ deposition (β, 0.0002; 95% CI, -0.003 to 0.002, p = .671). An additional exploratory analysis for each sex showed lower baseline BMI was associated with greater increases in tau deposition in males (β, -0.027; 95% CI, -0.046 to -0.009; p = 0.007), but not in females. Discussion: The findings suggest that lower BMI in late-life may predict or contribute to the progression of tau pathology over the subsequent years in cognitively unimpaired older adults.

Brain-derived neurotrophic factor (BDNF) is the most abundant neurotrophin in the mammalian brain. Preclinical studies suggest that BDNF influences the pathophysiology of Alzheimer's disease. In humans, higher blood BDNF levels have been associated with a lower risk of dementia. However, the relationship between serum BDNF levels and the progression to mild cognitive impairment (MCI) in cognitively normal (CN) individuals remains uncertain. To examine whether higher serum BDNF levels in CN older adults are associated with a reduced incidence of MCI over a 4-year follow-up period and to identify potential moderators of this relationship. Longitudinal analyses were conducted using follow-up data from the Korean Brain Aging Study for Early Diagnosis and Prediction of Alzheimer's Disease, an ongoing prospective cohort study. Data were collected from January 1, 2014, to May 31, 2021, and analyzed from May 1, 2023, to September 30, 2023. Community and memory clinic setting. A total of 274 CN older adults aged 55-90 years were included at baseline. Progression to MCI over the 4-year follow-up period. Among the 274 participants, 26 developed MCI during follow-up. The high BDNF group had a significantly lower incidence of MCI compared to the low BDNF group (hazard ratio [HR], 0.27; 95 % confidence interval [CI], 0.11-0.69; P = 0.006). This association persisted even after adjusting for BDNF Val66Met polymorphism, amyloid PET positivity, vascular risk factors, cholesterol levels, triglycerides, homocysteine, BMI, smoking, alcohol, TBI history, CES-D, and MMSE scores (HR, 0.14; 95 % CI, 0.05-0.40; P < 0.001). Subgroup analyses further revealed that the association was significant only in women (HR, 0.12; 95 % CI, 0.03-0.48; P = 0.002), individuals aged <75 years (HR, 0.16; 95 % CI, 0.03-0.77; P = 0.022), those with less than a college degree (HR, 0.23; 95 % CI, 0.07-0.74; P = 0.013), and amyloid PET-negative (HR, 0.29; 95 % CI, 0.11-0.72; P = 0.014) individuals. These findings suggest a protective role of BDNF against clinical progression to MCI in cognitively healthy older individuals. This effect appears to be more prominent in women, as well as in relatively younger, less educated, and amyloid PET-negative individuals.

Junha Park, Min Soo Byun, Dahyun Yi, Hyejin Ahn, Joon Hyung Jung, Nayeong Kong, Yoon Young Chang, Gijung Jung, Jun-Young Lee, Yu Kyeong Kim, Yun-Sang Lee, Koung Mi Kang, Chul-Ho Sohn, Dong Young Lee; for the KBASE Research Group. Clin Psychopharmacol Neurosci 2024;22:646-54. https://doi.org/10.9758/cpn.24.1189