Bile acid profile associated with CSF and PET biomarkers in Alzheimer's disease

BACKGROUND

Recent studies have shown that gut microbiota can affect the development of Alzheimer's disease (AD) through various mechanisms. Bile acids (BAs), which are the final byproducts of cholesterol metabolism created through both the human body and gut microbiome, appear to be influenced by gut microbiota and may impact AD pathological characteristics such as the accumulation of tau and amyloid-β. We aimed to investigate the associations between various serum BAs and CSF biomarkers (including Aβ, total tau, and p-tau). Additionally, we sought to examine the longitudinal changes in brain Aβ and tau through PET imaging in relation to BAs profile.

METHODS

The data of 828 subjects including 491 diagnosed with mild cognitive impairment (MCI), 119 patients diagnosed with AD, and 267 cognitively normal (CN) participants were obtained from ADNI. The baseline and longitudinal [18F] florbetapir and [18F] flortaucipir PET standard uptake value ratios (SUVR) measures were obtained to assess the accumulation of tau and Aβ. Moreover, baseline levels of serum BAs and CSF Aβ1-42, tau, and p-tau were used.

RESULTS

After FDR correction we observed that five BAs level and relevant calculated ratios were associated with CSF p-tau and tau, three with CSF Aβ1-42. Furthermore, three BAs level and relevant calculated ratios were associated with the tau-PET rate of change, and two with the Aβ rate of change.

CONCLUSION

The findings from our study suggest a correlation between altered profiles of BAs and CSF and imaging biomarkers associated with AD. These results provide supporting evidence for the link between the gut microbiome and the pathological features of AD.

Progranulin and neuropathological features of Alzheimer's disease: longitudinal study

BACKGROUND

Progranulin is an anti-inflammatory protein that plays an essential role in the synapse function and the maintenance of neurons in the central nervous system (CNS). It has been shown that the CSF level of progranulin increases in Alzheimer's disease (AD) patients and is associated with the deposition of amyloid-beta (Aβ) and tau in the brain tissue. In this study, we aimed to assess the longitudinal changes in cerebrospinal fluid (CSF) progranulin levels during different pathophysiological stages of AD and investigate associated AD pathologic features.

METHODS

We obtained the CSF and neuroimaging data of 1001 subjects from the ADNI database. The participants were classified into four groups based on the A/T/N framework: A + /TN + , A + /TN-, A-/TN + , and A-/TN-.

RESULTS

Based on our analysis there was a significant difference in CSF progranulin (P = 0.001) between ATN groups. Further ANOVA analysis revealed that there was no significant difference in the rate of change of CSF-progranulin ATN groups. We found that the rate of change of CSF progranulin was associated with baseline Aβ-PET only in the A-/TN + group. A significant association was found between the rate of change of CSF progranulin and the Aβ-PET rate of change only in A-/TN +  CONCLUSION: Our findings revealed that an increase in CSF progranulin over time is associated with faster formation of Aβ plaques in patients with only tau pathology based on the A/T/N classification (suspected non-Alzheimer's pathology). Together, our findings showed that the role of progranulin-related microglial activity on AD pathology can be stage-dependent, complicated, and more prominent in non-AD pathologic changes. Thus, there is a need for further studies to consider progranulin-based therapies for AD treatment.