Association of liver fibrosis with cognitive test performance and brain imaging parameters in the UK Biobank study

Systemic determinants of brain health in ageing

Preservation of brain health is a worldwide priority. The traditional view is that the major threats to the ageing brain lie within the brain itself. Consequently, therapeutic approaches have focused on protecting the brain from these presumably intrinsic pathogenic processes. However, an increasing body of evidence has unveiled a previously under-recognized contribution of peripheral organs to brain dysfunction and damage. Thus, in addition to the well-known impact of diseases of the heart and endocrine glands on the brain, accumulating data suggest that dysfunction of other organs, such as gut, liver, kidney and lung, substantially affects the development and clinical manifestation of age-related brain pathologies. In this Review, a framework is provided to indicate how organ dysfunction can alter brain homeostasis and promote neurodegeneration, with a focus on dementia. We delineate the associations of subclinical dysfunction in specific organs with dementia risk and provide suggestions for public health promotion and clinical management.

The association between liver fibrosis score and incident dementia: A nationwide retrospective cohort study

BACKGROUND

We assessed the relationship of liver fibrosis score with incident dementia in a large, national sample.

METHODS

For this retrospective cohort study, data of dementia-free individuals aged 40-69 years were derived from electronic records of the largest healthcare provider in Israel. The association between liver fibrosis score (FIB-4), assessed from routine laboratory measurements, and incident dementia was explored through multivariate cox regression models.

RESULTS

Of the total sample (N = 826,578, mean age 55 ± 8 years at baseline), 636,967 (77%) had no fibrosis, 180,114 (21.8%) had inconclusive fibrosis status and 9497 (1.2%) had high risk for advanced fibrosis. Over a median follow-up of 17 years, 41,089 dementia cases were recorded. Inconclusive liver fibrosis and advanced fibrosis were associated with increased dementia risk (HR = 1.09, 95%CI: 1.07-1.11 and HR = 1.18, 95%CI: 1.10-1.27, respectively). This association remained robust through seven sensitivity analyses.

CONCLUSIONS

Liver fibrosis assessed through a serum-based algorithm may serve as a risk factor for dementia in the general population.

HIGHLIGHTS

Liver fibrosis may predict dementia diagnosis in the general population. Inconclusive liver fibrosis was associated with 9% increased dementia risk. Advanced liver fibrosis was associated with 18% increased dementia risk. Findings remained robust in sensitivity analyses and after adjustments.

Nonalcoholic Fatty Liver Disease and Longitudinal Change in Imaging and Plasma Biomarkers of Alzheimer Disease and Vascular Pathology

BACKGROUND AND OBJECTIVES

Prospective measures of plasma and cerebral MRI biomarkers of Alzheimer disease (AD) and vascular neuropathology provide an opportunity to investigate possible mechanisms linking liver disease and dementia. We aimed to quantify the association of midlife nonalcoholic fatty liver disease (NAFLD) with change in plasma and brain MRI biomarkers of AD and vascular neuropathology.

METHODS

We included participants from the Atherosclerosis Risk in Communities Study with brain MRI measurements of white matter hyperintensity (WMH) volume and temporal-parietal lobe cortical thickness meta region of interest (ROI) at up to 2 different visits, in 2011-13 and 2016-19, and plasma biomarkers of β-amyloid (Aβ)42:40, phosphorylated tau at threonine 181, and neurofilament light (NfL) were measured up to 3 times in 1993-95, 2011-13, and 2016-19. NAFLD was categorized using the fatty liver index in 1990-92. Multivariate linear regression was performed for associations between midlife NAFLD and change in plasma and brain MRI biomarkers of AD and vascular neuropathology. The primary models adjusted for demographics, Apolipoprotein E, alcohol use, and kidney function.

RESULTS

Among 1,706 participants (mean age 56 years, 62% female, 28% Black), midlife NAFLD vs no NAFLD was associated with greater late-life WMH volume (difference per SD 0.19, 95% CI 0.06-0.31) and faster late-life WMH increase over 6 years (difference in annual change, SD 0.28, 95% CI 0.05-0.51), suggesting accumulating vascular pathology. Midlife NAFLD vs no NAFLD was also associated with AD biomarkers in midlife (lower Aβ42:40 [SD -0.21, 95% CI -0.39 to -0.04] measured in 1993-95) and late life (lower Aβ42:40 [SD -0.13, 95% CI -0.23 to -0.03] and lower temporal-parietal lobe cortical thickness meta ROI [SD -0.16, 95% CI -0.28 to -0.05] measured in 2011-13). Although midlife NfL was lower in individuals with vs without midlife NAFLD, those with NAFLD exhibited a faster rate of NfL increase that accelerated over time.

DISCUSSION

Midlife NAFLD shows associations with AD and accumulating vascular pathology, revealing potential pathways linking liver function to dementia. Plasma biomarkers of neuropathology and neuronal injury may serve as easily measurable and dynamic indicators for monitoring the impacts of impaired liver function on brain health.

Cognitive impairment and liver fibrosis in non-alcoholic fatty liver disease

Background

Data regarding the prevalence and phenotype of cognitive impairment in non-alcoholic fatty liver disease (NAFLD) are limited.

Objective

We assessed the prevalence and nature of cognitive deficits in people with NAFLD and assessed whether liver fibrosis, an important determinant of outcomes in NAFLD, is associated with worse cognitive performance.

Methods

We performed a prospective cross-sectional study. Patients with NAFLD underwent liver fibrosis assessment with transient elastography and the following assessments: Cognitive Change Index, Eight-Item Informant Interview to Differentiate Aging and Dementia Questionnaire (AD8), Montreal Cognitive Assessment (MoCA), EncephalApp minimal hepatic encephalopathy test and a limited National Institutes of Health Toolbox battery (Flanker Inhibitory Control and Attention Test, Pattern Comparison Test and Auditory Verbal Learning Test). We used multiple linear regression models to examine the association between liver fibrosis and cognitive measures while adjusting for relevant covariates.

Results

We included 69 participants with mean age 50.4 years (SD 14.4); 62% were women. The median liver stiffness was 5.0 kilopascals (IQR 4.0-6.9), and 25% had liver fibrosis (≥7.0 kilopascals). Cognitive deficits were common in people with NAFLD; 41% had subjective cognitive impairment, 13% had an AD8 >2, 32% had MoCA <26 and 12% had encephalopathy detected on the EncephalApp test. In adjusted models, people with liver fibrosis had modestly worse performance only on the Flanker Inhibitory Control and Attention Task (β=-0.3; 95% CI -0.6 to -0.1).

Conclusion

Cognitive deficits are common in people with NAFLD, among whom liver fibrosis was modestly associated with worse inhibitory control and attention.

Associations of liver dysfunction with incident dementia, cognition, and brain structure: A prospective cohort study of 431 699 adults

The relationship between liver dysfunction and dementia has been researched extensively but remains poorly understood. In this study, we investigate the longitudinal and cross-sectional associations between liver function and liver diseases and risk of incident dementia, impaired cognition, and brain structure abnormalities using Cox proportion hazard model and linear regression model. 431 699 participants with a mean of 8.65 (standard deviation [SD] 2.61) years of follow-up were included from the UK Biobank; 5542 all-cause dementia (ACD), 2427 Alzheimer's disease (AD), and 1282 vascular dementia (VaD) cases were documented. We observed that per SD decreases in alanine transaminase (ALT; hazard ratio [HR], 0.917; PFDR  <0.001) and per SD increases in aspartate aminotransferase (AST; HR, 1.048; PFDR  = 0.010), AST to ALT ratio (HR, 1.195; PFDR  <0.001), gamma-glutamyl transpeptidase (GGT; HR, 1.066; PFDR  <0.001), alcoholic liver disease (ALD; HR, 2.872; PFDR  <0.001), and fibrosis and cirrhosis of liver (HR, 2.285; PFDR  = 0.002), being significantly associated with a higher risk of incident ACD. Restricted cubic spline models identified a strong U-shaped association between Alb and AST and incident ACD (Pnonlinear  <0.05). Worse cognition was positively correlated with AST, AST to ALT ratio, direct bilirubin (DBil), and GGT; negatively correlated with ALT, Alb, and total bilirubin (TBil); and ALD and fibrosis and cirrhosis of liver (PFDR  <0.05). Moreover, changes in ALT, GGT, AST to ALT ratio, and ALD were significantly associated with altered cortical and subcortical regions, including hippocampus, amygdala, thalamus, pallidum, and fusiform (PFDR  <0.05). In sensitivity analysis, metabolic dysfunction-associated steatotic liver disease (MASLD) was associated with the risk of ACD and brain subcortical changes. Our findings provide substantial evidence that liver dysfunction may be an important factor for incident dementia. Early intervention in the unhealthy liver may help prevent cognitive impairment and dementia incidence.

Nonalcoholic fatty liver disease, liver fibrosis, and structural brain imaging: The Cross-Cohort Collaboration

BACKGROUND AND PURPOSE

Prior studies reported conflicting findings regarding the association of nonalcoholic fatty liver disease (NAFLD) and liver fibrosis with measures of brain health. We examined whether NAFLD and liver fibrosis are associated with structural brain imaging measures in middle- and old-age adults.

METHODS

In this cross-sectional study among dementia- and stroke-free individuals, data were pooled from the Offspring and Third Generation cohorts of the Framingham Heart Study (FHS), the Rotterdam Study (RS), and the Study of Health in Pomerania. NAFLD was assessed through abdominal imaging. Transient hepatic elastography (FibroScan) was used to assess liver fibrosis in FHS and RS. Linear regression models were used to explore the relation of NAFLD and liver fibrosis with brain volumes, including total brain, gray matter, hippocampus, and white matter hyperintensities, adjusting for potential confounders. Results were combined using fixed effects meta-analysis.

RESULTS

In total, 5660 and 3022 individuals were included for NAFLD and liver fibrosis analyses, respectively. NAFLD was associated with smaller volumes of total brain (β = -3.5, 95% confidence interval [CI] = -5.4 to -1.7), total gray matter (β = -1.9, 95% CI = -3.4 to -0.3), and total cortical gray matter (β = -1.9, 95% CI = -3.7 to -0.01). In addition, liver fibrosis (defined as liver stiffness measure ≥8.2 kPa) was related to smaller total brain volumes (β = -7.3, 95% CI = -11.1 to -3.5). Heterogeneity between studies was low.

CONCLUSIONS

NAFLD and liver fibrosis may be directly related to brain aging. Larger and prospective studies are warranted to validate these findings and identify liver-related preventive strategies for neurodegeneration.

Associations between liver function and cerebrospinal fluid biomarkers of Alzheimer's disease pathology in non-demented adults: The CABLE study

Liver function has been suggested as a possible factor in the progression of Alzheimer's disease (AD) development. However, the association between liver function and cerebrospinal fluid (CSF) levels of AD biomarkers remains unclear. In this study, we analyzed the data from 1687 adults without dementia from the Chinese Alzheimer's Biomarker and LifestylE study to investigate differences in liver function between pathological and clinical AD groups, as defined by the 2018 National Institute on Aging-Alzheimer's Association Research Framework. We also examined the linear relationship between liver function, CSF AD biomarkers, and cognition using linear regression models. Furthermore, mediation analyses were applied to explore the potential mediation effects of AD pathological biomarkers on cognition. Our findings indicated that, with AD pathological and clinical progression, the concentrations of total protein (TP), globulin (GLO), and aspartate aminotransferase/alanine transaminase (ALT) increased, while albumin/globulin (A/G), adenosine deaminase, alpha-L-fucosidase, albumin, prealbumin, ALT, and glutamate dehydrogenase (GLDH) concentrations decreased. Furthermore, we also identified significant relationships between TP (β = -0.115, pFDR  < 0.001), GLO (β = -0.184, pFDR  < 0.001), and A/G (β = 0.182, pFDR  < 0.001) and CSF β-amyloid1-42 (Aβ1-42 ) (and its related CSF AD biomarkers). Moreover, after 10 000 bootstrapped iterations, we identified a potential mechanism by which TP and GLDH may affect cognition by mediating CSF AD biomarkers, with mediation effect sizes ranging from 3.91% to 16.44%. Overall, our results suggested that abnormal liver function might be involved in the clinical and pathological progression of AD. Amyloid and tau pathologies also might partially mediate the relationship between liver function and cognition. Future research is needed to fully understand the underlying mechanisms and causality to develop an approach to AD prevention and treatment approach.

Association of Serum Liver Enzymes with Brain Amyloidopathy and Cognitive Performance

Background

Alzheimer's disease (AD) is characterized by amyloid-β (Aβ) plaque accumulation and neurofibrillary tangles in the brain. Emerging evidence has suggested potential interactions between the brain and periphery, particularly the liver, in regulating Aβ homeostasis.

Objective

This study aimed to investigate the association of serum liver enzymes with brain amyloidopathy and cognitive performance in patients with complaints of cognitive decline.

Methods

A total of 1,036 patients (mean age 74 years, 66.2% female) with subjective cognitive decline, mild cognitive impairment, AD dementia, and other neurodegenerative diseases were included using the Smart Clinical Data Warehouse. Amyloid positron emission tomography (PET) imaging, comprehensive neuropsychological evaluations, and measurements of liver enzymes, including aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase, total bilirubin, and albumin, were assessed. After propensity score matching, logistic and linear regression analyses were used to investigate the associations between liver enzymes, amyloid status, and cognitive performance. Additionally, a machine learning approach was used to assess the classification performance of liver enzymes in predicting amyloid PET positivity.

Results

Lower ALT levels and higher AST-to-ALT ratios were significantly associated with amyloid PET positivity and AD diagnosis. The AST-to-ALT ratio was also significantly associated with poor memory function. Machine learning analysis revealed that the classification performance of amyloid status (AUC = 0.642) for age, sex, and apolipoprotein E ɛ4 carrier status significantly improved by 6.2% by integrating the AST-to-ALT ratio.

Conclusions

These findings highlight the potential association of liver function on AD and its potential as a diagnostic and therapeutic implications.

Elevated C-reactive protein mediates the liver-brain axis: a preliminary study

BACKGROUND

Chronic liver diseases of all etiologies exist along a spectrum with varying degrees of hepatic fibrosis. Despite accumulating evidence implying associations between liver fibrosis and cognitive functioning, there is limited research exploring the underlying neurobiological factors and the possible mediating role of inflammation on the liver-brain axis.

METHODS

Using data from the UK Biobank, we examined the cross-sectional association of liver fibrosis (as measured by Fibrosis-4 score) with cognitive functioning and regional grey matter volumes (GMVs) while adjusting for numerous covariates and multiple comparisons. We further performed post-hoc preliminary analysis to investigate the mediating effect of C-reactive protein (CRP) on the association between liver fibrosis and both cognitive functioning and GMVs.

FINDINGS

We analysed behaviour from up to 447,626 participants (N ranged from 45,055 to 447,533 per specific cognitive metric) 37 years and older. 38,244 participants (age range 44-82 years) had GMV data collected at a median 9-year follow-up. Liver fibrosis showed significant associations with cognitive performance in reasoning, working memory, visual memory, prospective memory, executive function, and processing speed. Subgroup analysis indicated larger effects sizes for symbol digital substitution but smaller effect sizes for trail making in middle-aged people than their old counterparts. Neuroimaging analyses revealed significant associations between liver fibrosis and reduced regional GMVs, primarily in the hippocampus, thalamus, ventral striatum, parahippocampal gyrus, brain stem, and cerebellum. CRP levels were significantly higher in adults with advanced liver fibrosis than those without, indicating an elevated systemic inflammation. Moreover, the serum CRP significantly mediated the effect of liver fibrosis on most cognitive measures and regional GMVs in the hippocampus and brain stem.

INTERPRETATION

This study provides a well-powered characterization of associations between liver fibrosis, cognitive impairment, and grey matter atrophy. It also highlights the possibly mediating role of systemic inflammation on the liver-brain axis. Early surveillance and prevention of liver diseases may reduce cognitive decline and brain GMV loss.

FUNDING

National Science Foundation, and National Institutes of Health.