Concurrent cardiac transthyretin and brain β amyloid accumulation among the older adults: The Hisayama study

Intracellular and Extracellular Localization of Transthyretin and Its Association With Amyloid-β in Alzheimer's Disease Brains

Transthyretin (TTR) can bind to Aβ and prevent the formation of Aβ fibrils in vitro; it is thus a highly interesting molecule in the field of Alzheimer's disease (AD) research. However, the distribution of TTR and its affinity to Aβ in both healthy human brains and those of AD patients remain unclear. We therefore examined TTR in human brains using postmortem brain samples. Paraffin sections and extracted protein samples were prepared from AD and control (non-AD) brains. Immunohistochemistry was performed to detect TTR expression patterns, and immunofluorescent staining was used to reveal the relationships between the intracellular and extracellular localizations of TTR and Aβ. We also performed western blotting for TTR using brain extracts. In immunohistochemical staining of the human brain, TTR signal was detected not only in extracellular tissue but also in the cytoplasm of neurons and glia. The TTR-positive area was significantly greater in AD brains than in non-AD brains. However, expression of TTR transcripts did not differ between AD and non-AD brains in our previously obtained RNA-sequencing and microarray data. Immunofluorescent staining with multiple antibodies revealed that TTR was co-localized with Aβ in the cytoplasm of neurons. In extracellular Aβ plaques, TTR presented in the same region but was not co-localized with dense Aβ fibrils. Together, our results indicate that TTR is widely expressed in the human brain rather than being limited to the choroid plexus and that TTR is more abundant in AD brains. Our results also suggest that the affinity between TTR and Aβ changes depending on the structure of Aβ. Our data will be valuable for the future development of TTR-related AD preventative methods and medications.

Alzheimer's Disease With Cardiac Transthyretin Amyloidosis: A Clinicopathological Study of Autopsy Cases

The relationship between Alzheimer's disease and cardiac transthyretin amyloidosis (ATTR) has been reported epidemiologically. However, the details of its clinicopathological characteristics are unclear. To clarify the pathogenesis of Alzheimer's disease combined with cardiac ATTR, 50 autopsy cases of Alzheimer's disease with cardiac hypertrophy were examined. Transthyretin amyloid deposition was studied by immunostaining in cases where amyloid deposition was suspected in various organs by HE staining. ATTR in systemic organs was also examined. The pathological diagnosis of Alzheimer's disease was done based on the National Institute on Aging and Alzheimer's Association (NIA-AA) guidelines. Cerebral amyloid angiopathy (CAA) was rated on a 3-point scale according to the Vonsattel scale. The pathological diagnosis of cardiac ATTR was done using a 3-point scale based on previously published findings on amyloid amounts. Six out of 50 patients were found to have cardiac ATTR by immunostaining and protein mass analysis of myocardial tissue. The sex distribution of the six patients was two males (Cases 3 and 6) and four females (Cases 1, 2, 4, and 5), and their ages were 97, 89, 91, 104, 86, and 77 years in Cases 1-6, respectively. In Cases 1-6, the NIAA score/CAA assessment/ATTR stages were intermediate/severe/G3, intermediate/moderate/G3, high/severe/G3, high/severe/G2, high/severe/G2, and intermediate/moderate/G2, respectively. Cases 1-5 also had cerebral infarction. In all cases, Transthyretin amyloid deposition was seen mainly in the vessel walls of various organs throughout the body. In the heart, transthyretin amyloid deposition was observed in the myocardial vessel walls and between myocardial fibers. On autopsy, cardiogenic cerebral infarction or heart failure was considered to be the main cause of death in Cases 1-5. These results indicate that Alzheimer's disease could be regarded as a systemic disease rather than just a localized disease presenting with dementia.

Clinical and Imaging Markers of Cardiac Function and Brain Health: A Meta-Analysis of Community-Based Studies

BACKGROUND AND OBJECTIVES

Cardiac dysfunction and heart failure are linked to cognitive impairment, but the underlying brain pathology remains undetermined. We investigated associations between cardiac function (measured by echocardiography or cardiac MRI), clinical heart failure, and structural markers on brain MRI, including volumes of gray and white matter (WM), the hippocampus, and white matter hyperintensities (WMHs).

METHODS

We leverage data from 7 prospective, community-based cohorts across Europe and the United States, all part of the Cross-Cohort Collaboration. The included cohorts were the Age, Gene/Environment Susceptibility-Reykjavik Study, Atherosclerosis Risk in Communities study, Austrian Stroke Prevention Study, Cardiovascular Health Study, Framingham Heart Study, Rotterdam Study, and Study of Health in Pomerania (SHIP-START and SHIP-TREND). Each cohort performed cross-sectional multivariable linear regression analyses, after which estimates were pooled through random-effects meta-analysis. Heterogeneity was assessed by the I2 index (%).

RESULTS

Among 10,889 participants (mean age: 66.8 years, range 52.0-76.0; 56.7% women), markers of systolic dysfunction were consistently associated with smaller total brain volume (TBV) (e.g., adjusted standardized mean difference for moderate to severe dysfunction -0.19, 95% CI -0.31 to -0.07, I2 = 20%). Impaired relaxation and restrictive diastolic dysfunction were also associated with smaller TBV (e.g., for impaired relaxation -0.08, 95% CI -0.15 to -0.01, I2 = 32%) and hippocampal volume (-0.18, 95% CI -0.33 to -0.03, I2 = 0%), with similar results for the E/A-ratio. Systolic and diastolic dysfunction was not consistently associated with volume of WMHs. Among 5 cohorts with available data, 302 (3.4%) participants had clinical heart failure, which was associated with smaller brain volumes, particularly in the hippocampus (-0.13, 95% CI -0.23 to -0.02, I2 = 1%).

DISCUSSION

In this large study among community-dwelling adults, subclinical cardiac dysfunction was associated with brain imaging markers of neurodegeneration. These findings encourage longitudinal investigations on the effect of maintaining cardiac function on brain health.

ATTRV30M amyloidosis post-liver transplant: cognition and long-term survival

BACKGROUND

Patients with hereditary amyloidosis related to transthyretin (ATTRv amyloidosis) treated with liver transplant (LTx) often have central nervous system (CNS) manifestations, including cognitive dysfunction. The aim of this study was to explore the long-term outcome associated with neuropsychological test performance.

METHODS

A retrospective longitudinal review was conducted in a cohort of 289 ATTRv amyloidosis patients with the Val30Met mutation (ATTRV30M amyloidosis) who underwent a neuropsychological assessment (T1) 1-23 years (median = 11) post-LTx and 20-189 months (median = 81) prior to the study review. Clinical records were reviewed. The Kaplan-Meier and Cox regression methods were used to estimate survival and adjusted hazard ratios for all-cause mortality.

RESULTS

Impaired performance on Dementia Rating Scale-2, Semantic Fluency, Phonemic Fluency and Trail Making Test Part B were predictive of shorter survival after neuropsychological assessment, even when demographic and clinical variables (i.e. education, age at disease onset ≥ 50, disease duration at LTx, interval between LTx and T1, age at T1, Modified Polyneuropathy Disability score at T1, and history of focal neurological episodes at T1) were taken into account. Measures of verbal learning and memory were not predictive of mortality.

CONCLUSIONS

Study results demonstrate that cognitive impairment in ATTRV30M amyloidosis patients treated with LTx predicts long-term survival.

Tetrameric Transthyretin as a Protective Factor Against Alzheimer's Disease

Transthyretin (TTR) is a tetrameric protein traditionally recognized for its role in transporting thyroxine and retinol. Recent research has highlighted the potential neuroprotective functions of TTR in the setting of Alzheimer's disease (AD), which is the most common form of dementia and is caused by the deposition of amyloid beta (Aβ) and the resulting cytotoxic effects. This paper explores the mechanisms of TTR protective action, including its interaction with Aβ to prevent fibril formation and promote Aβ clearance from the brain. It also synthesizes experimental evidence suggesting that enhanced TTR stability may mitigate neurodegeneration and cognitive decline in AD. Potential therapeutic strategies such as small molecule stabilizers of TTR are discussed, highlighting their role in enhancing TTR binding to Aβ and facilitating its clearance. By consolidating current knowledge and proposing directions for future research, this review aims to underscore the significance of TTR as a neuroprotective factor in AD and the potential implications for future research.

Predictors of cognitive dysfunction in hereditary transthyretin amyloidosis with liver transplant

BACKGROUND

Cognitive dysfunction is part of the broad spectrum of clinical manifestations in older untreated hereditary transthyretin amyloidosis patients with peripheral polyneuropathy.

OBJECTIVE

The objective of this study is to systematically explore cognitive dysfunction in ATTRV30M amyloidosis patients whose disease course was modified by liver transplant (LT).

METHODS

A series of 269 carriers of TTRVal30Met mutation treated with LT underwent a neuropsychological assessment. Clinical charts were reviewed to identify focal neurological episodes (FNEs), cognitive complaints and laboratory results. Chi-square and Mann-Whitney tests explored potential predictors of cognitive dysfunction.

RESULTS

Cognitive dysfunction was identified in 35 patients (13%)-14 (5%) had mild and 21 (8%) had moderate dysfunction. In comparison to normal cognition, both mild and moderate cognitive dysfunction patients had older age, higher mPND score and elevated NT-proBNP and Cystatin C values. Mild cognitive dysfunction was associated with longer disease duration and history of FNEs, whereas moderate dysfunction was related to older age at disease onset and more cognitive complaints and depression symptoms.

CONCLUSIONS

Consistent with the natural history of the disease, older age and higher severity of the disease are significantly associated and potentially predictors of cognitive dysfunction in ATTRV30M patients treated with LT. The level of cognitive dysfunction may depend on some clinical variables.

Comparative Structure of Male Mortality From Cardiac Causes in Five-Year Age Groups

Aim      To study the nosological structure of male mortality in 5-year age groups (15-85+) and the contribution of cardiac causes to all-cause mortality in 2020; to discuss the correctness of statistical recording of causes of cardiac death.Material and methods  Data source: Center for Demographic Research of the Russian School of Economy http://demogr.nes.ru / index.php / ru / demogr_indicat / agreement. The selected indexes were all-cause death, causes of the class of circulatory diseases (CD) according to the International Classification of Diseases, Tenth Revision (ICD-10) (class IX, codes I00-I99), and cardiac causes of death (codes I00-I40, I70, I67.4, Q20-28) in 5-year age groups.Results Proportions of CD and cardiac causes in the male all-cause mortality were almost identical in the age groups younger than 30 years. Then the proportion of cardiac deaths remained almost unchanged (30-34 %) in contrast to the rapid growth of the CD proportion (to 51 % with a maximum at 75-79 years). Until the age of 45 years, more than 50% of cardiac deaths were caused by heart defects and cardiomyopathies and more than 25% by acute forms of ischemic heart disease (IHD); in older groups, their proportions decreased but the mortality increased. In the age groups younger than 50 years, the mortality from "Other forms of acute IHD" (ICD codes I20, I24.1-9 counted as one line) was higher than the mortality from myocardial infarction (MI); after 50 years, the MI mortality became higher. The combined proportion of two groups in the mortality from cardiac causes was maximal at the age of 20-24 years (31 %), then it decreased to a minimum of 9 % at the age of 85+. The mortality from and the proportions of chronic forms of IHD (more than 50% of which have no clear criteria for diagnosis and death), arterial hypertension, "Myocardial degeneration" (ICD code I51.5), and "Pulmonary heart and pulmonary circulation disorders" (ICD codes I26-I28) rapidly grow with increasing age. Existing approaches to recording the causes of death do not allow assessment of the contribution and mortality rates from a number of cardiac diseases.Conclusion      Mortality reduction programs should provide more accurate recording of the causes of death and take into account age-related features of the nosological structure of cardiac mortality.

Cerebral amyloid angiopathy-related cardiac injury: Focus on cardiac cell death

Cerebral amyloid angiopathy (CAA) is a kind of disease in which amyloid β (Aβ) and other amyloid protein deposits in the cerebral cortex and the small blood vessels of the brain, causing cerebrovascular and brain parenchymal damage. CAA patients are often accompanied by cardiac injury, involving Aβ, tau and transthyroxine amyloid (ATTR). Aβ is the main injury factor of CAA, which can accelerate the formation of coronary artery atherosclerosis, aortic valve osteogenesis calcification and cardiomyocytes basophilic degeneration. In the early stage of CAA (pre-stroke), the accompanying locus coeruleus (LC) amyloidosis, vasculitis and circulating Aβ will induce first hit to the heart. When the CAA progresses to an advanced stage and causes a cerebral hemorrhage, the hemorrhage leads to autonomic nervous function disturbance, catecholamine surges, and systemic inflammation reaction, which can deal the second hit to the heart. Based on the brain-heart axis, CAA and its associated cardiac injury can create a vicious cycle that accelerates the progression of each other.