Transthyretin V142I Genetic Variant and Cardiac Remodeling, Injury, and Heart Failure Risk in Black Adults

Hereditary Transthyretin Cardiac Amyloidosis With the p.V142I Variant: Mechanistic Insights and Diagnostic Challenges

The most common form of hereditary transthyretin cardiac amyloidosis (hATTR-CA) in the United States and the United Kingdom is the p.V142I variant. About 3% to 4% of patients with African ancestry carry this genetic predisposition to develop signs and symptoms of hATTR-CA. Nevertheless, clinical manifestations of hATTR-CA appear only late in the fifth and sixth decades of life, despite its clear genetic background. Imbalances in native protein-stabilizing and elementary breakdown cellular mechanisms are postulated as potential causes for affecting transthyretin structural integrity and myocardial fibril deposition. Noncoding variants, epigenetic and environmental factors, as well as gut microbiome derangements may serve as disease-modifying factors that feature detrimental amyloidogenic organ involvement and impact disease severity. Organ amyloid deposition varies widely among different carriers of a genetic transthyretin variant. The genotype-phenotype interdependence causes unpredictable phenotypic penetrance that results in a variety of signs and symptoms and patient outcomes. Cardiovascular biomarkers and multimodality imaging may identify initial amyloidogenic organ involvement. These early clinical clues through the course of hATTR-CA offer a window of opportunity for early treatment onset to cease disease progression and alter prognosis. Identifying at-risk patients requires information on the genetic background of probands and their relatives. Initiatives to reveal asymptomatic gene carriers early in the disease should be encouraged, as it necessitates stringent patient follow-up and immediate treatment onset to reduce the burden of heart failure hospitalization and mortality in hATTR-CA.

Race, Genetics, and Social Determinants of Health in Transthyretin Cardiac Amyloidosis: A Literature Review and Call to Action

PURPOSE OF REVIEW

Recent evidence suggests that transthyretin cardiac amyloidosis (ATTR-CM) is significantly more common than once believed, yet it remains frequently under- and mis-diagnosed. With effective treatments now available, early and accurate diagnosis has become critical for better patient outcomes. Understanding the interplay between genetics, race, and social determinants of health (SDOH) in influencing both ATTR-CM diagnosis and management is essential for bridging the current gaps.

RECENT FINDINGS

Our analysis reveals multiple barriers affecting ATTR-CM care. Specifically, we discuss how clinician awareness, regional differences in clinical practice, and limited access to health care and specialty centers contribute to diagnostic delays. Additionally, we identify several management obstacles, such as inadequate diversity in clinical trials, high cost of available treatments, and limited ancillary resources. We examine these challenges in detail and provide practical solutions to address them. While disparities in heart failure outcomes have been well-documented, those specific to ATTR-CM remain underrepresented in the literature. This review establishes a structured approach to understanding how biological, structural and SDOH-related disparities impact ATTR-CM diagnosis and management while offering concrete strategies to overcome these challenges. We emphasize the need for enhanced SDOH identification and advocate for coordinated, multidisciplinary efforts to improve ATTR-CM patient outcomes.

Biomarkers in Subclinical Transthyretin Cardiac Amyloidosis

PURPOSE OF REVIEW

The most common type of cardiac amyloidosis is transthyretin amyloidosis (ATTR-CM). Early forms of the disease can often go undetected. Effective pharmacological treatments are available for ATTR-CM. However, current treatment options may be more effective when used earlier in the disease, making early detection paramount. Below, we discuss updates with regards to the role that blood-based biomarkers play in detecting subclinical cardiac amyloidosis.

RECENT FINDINGS

Carriers of amyloidogenic mutations in the TTR gene are at a heightened risk of developing heart failure and have higher mortality rates compared with noncarrier counterparts. Conventional biomarkers, such as the cardiac troponins and natriuretic peptides, may be useful to monitor subclinical cardiac amyloidosis. In addition, recent studies have demonstrated links between amyloidogenic TTR carrier status and low levels of circulating transthyretin (TTR) and retinol-binding protein 4 (RBP4). Laboratory advances have also allowed for the development of peptide-based detection methods. Probes targeting transthyretin aggregates and nonnative TTR peptides have shown promise in differentiating ATTR from non-ATTR amyloidosis populations. Finally, recent studies have identified neurofilament light chains as potential biomarkers for detecting polyneuropathy-predominant amyloidosis. Conventional biomarkers, such as cardiac troponin and natriuretic peptides may indicate evolving amyloid deposition in early ATTR-CM. However, they are non-specific and emerging biomarkers such as serum transthyretin levels, retinol-binding protein 4, transthyretin aggregates, nonnative TTR, and neurofilament light chains may hold promise in characterizing subclinical ATTR.

Cardiovascular Risk Factors and Genetic Risk in Transthyretin V142I Carriers

BACKGROUND

Nearly 3% to 4% of Black individuals in the United States carry the transthyretin V142I variant, which increases their risk of heart failure. However, the role of cardiovascular (CV) risk factors (RFs) in influencing the risk of clinical outcomes among V142I variant carriers is unknown.

OBJECTIVES

This study aimed to assess the impact of CV RFs on the risk of heart failure in V142I carriers.

METHODS

This study included self-identified Black individuals without prevalent heart failure from 6 TOPMed (Trans-Omics for Precision Medicine) cohorts, the REGARDS (Reasons for Geographic And Racial Differences in Stroke) study, and the All of Us Research Program. The cohort was stratified based on the V142I genotype and the number of CV RFs (hypertension, diabetes, obesity, and hypercholesterolemia). Adjusted Cox models were used to assess the association of heart failure with the V142I genotype and CV RF profile, taking noncarriers with a favorable CV RF profile as reference.

RESULTS

The cross-sectional analysis, including 1,625 V142I carriers among 48,365 Black individuals, found that the prevalence of CV RFs did not vary by V142I carrier status. In the longitudinal analysis, there were 587 (3.2%) V142I carriers among 18,407 Black individuals (median age: 60 years [Q1-Q3: 52-68 years], 63.0% female). Among carriers, the heart failure risk was attenuated with a favorable (0 or 1 RF) CV RF profile (adjusted HR: 2.26; 95% CI: 1.58-3.23) compared with an unfavorable (3 or 4 RFs) CV RF profile (adjusted HR: 4.14; 95% CI: 2.79-6.14).

CONCLUSIONS

A favorable CV RF profile lowers but does not abrogate V142I variant-associated heart failure risk. This study highlights the importance of having a favorable CV RF profile among V142I carriers for risk reduction of heart failure.

Determinants of transthyretin levels and their association with adverse clinical outcomes among UK Biobank participants

Transthyretin is a transport protein whose misfolding has been implicated in the development of cardiac amyloidosis. Here, we examine the clinical correlates of transthyretin levels, the differences in transthyretin levels according to the pathogenic V142I TTR variant carrier status, and the association of transthyretin levels with outcomes among 35,206 UK Biobank participants who underwent plasma profiling and were free from prevalent cardiovascular disease and chronic renal disease. Transthyretin levels are lower in females, decrease with increasing C-reactive protein levels, and increase with body mass index, systolic blood pressure, diastolic blood pressure, total cholesterol, albumin levels, triglyceride levels, and creatinine levels. V142I non-carriers [n = 35,167, mean: -0.1 (0.3)] have higher adjusted transthyretin levels compared with the carriers [n = 39, mean: -0.5 (0.3)] (p:<0.001). A standard deviation decrease in transthyretin levels increases the risk of heart failure [HRadj: 1.17 (95% Confidence Interval = 1.08-1.26)] and all-cause mortality [HRadj: 1.18 (95% Confidence Interval = 1.14-1.24)]. This study shows that individuals with low transthyretin levels, such as those carrying the V142I variant, are at a higher risk of heart failure and mortality.

Carpal Tunnel Syndrome and Transthyretin Amyloidosis in the All of Us Research Program

OBJECTIVE

To evaluate the association of carpal tunnel syndrome (CTS) with incident heart failure and incident amyloidosis and to assess the risk of CTS in pathogenic TTR genetic variant carriers.

METHODS

This prospective cohort study included multiethnic US adults 18 years of age and older without prevalent heart failure and amyloidosis with available genotypic data from the All of Us Research Program. The primary outcomes were incident heart failure and incident amyloidosis. The association of incident heart failure and incident amyloidosis with CTS was assessed using multivariable adjusted Cox models accounting for age, sex, race and ethnicity, obesity, hypertension, diabetes, statin use, and smoking status.

RESULTS

Of the 166,987 individuals included, the median age was 54 (38 to 66) years; 105,279 (63.0%) were female, and 92,780 (55.6%) were non-Hispanic White individuals; CTS was identified in 12,407 (7.4%) individuals. Compared with individuals without CTS, the adjusted hazard ratio for incident heart failure was 1.13 (95% CI, 1.02 to 1.26) in individuals with CTS. The risk of amyloidosis was ∼3-fold higher (adjusted hazard ratio, 2.86; 95% CI, 1.71 to 4.77) in individuals with CTS compared with those without CTS. Individuals carrying a pathogenic TTR variant had an approximately 40% higher risk (adjusted hazard ratio, 1.38; 95% CI, 1.16 to 1.65) for development of CTS compared with noncarriers.

CONCLUSION

Cardiac amyloidosis screening programs may use CTS as a sentinel event and use genetic testing to identify individuals at a higher risk of TTR amyloidosis.

Cardiovascular Burden of the V142I Transthyretin Variant

Importance

Individual cohort studies concur that the amyloidogenic V142I variant of the transthyretin (TTR) gene, present in 3% to 4% of US Black individuals, increases heart failure (HF) and mortality risk. Precisely defining carrier risk across relevant clinical outcomes and estimating population burden of disease are important given established and emerging targeted treatments.

Objectives

To better define the natural history of disease in carriers across mid to late life, assess variant modifiers, and estimate cardiovascular burden to the US population.

Design, Setting, and Participants

A total of 23 338 self-reported Black participants initially free from HF were included in 4 large observational studies across the US (mean [SD], 15.5 [8.2] years of follow-up). Data analysis was performed between May 2023 and February 2024.

Exposure

V142I carrier status (n = 754, 3.2%).

Main Outcomes and Measures

Hospitalizations for HF (including subtypes of reduced and preserved ejection fraction) and all-cause mortality. Outcomes were analyzed by generating 10-year hazard ratios for each age between 50 and 90 years. Using actuarial methods, mean survival by carrier status was estimated and applied to the 2022 US population using US Census data.

Results

Among the 23 338 participants, the mean (SD) age at baseline was 62 (9) years and 76.7% were women. Ten-year carrier risk increased for HF hospitalization by age 63 years, predominantly driven by HF with reduced ejection fraction, and 10-year all-cause mortality risk increased by age 72 years. Only age (but not sex or other select variables) modified risk with the variant, with estimated reductions in longevity ranging from 1.9 years (95% CI, 0.6-3.1) at age 50 to 2.8 years (95% CI, 2.0-3.6) at age 81. Based on these data, 435 851 estimated US Black carriers between ages 50 and 95 years are projected to cumulatively lose 957 505 years of life (95% CI, 534 475-1 380 535) due to the variant.

Conclusions and Relevance

Among self-reported Black individuals, male and female V142I carriers faced similar and substantial risk for HF hospitalization, predominantly with reduced ejection fraction, and death, with steep age-dependent penetrance. Delineating the individual contributions of, and complex interplay among, the V142I variant, ancestry, the social construct of race, and biological or social determinants of health to cardiovascular disease merits further investigation.

Circulating transthyretin and retinol binding protein 4 levels among middle-age V122I TTR carriers in the general population

BACKGROUND

Hereditary transthyretin cardiac amyloidosis (ATTRv-CA) has a long latency phase before clinical onset, creating a need to identify subclinical disease. We hypothesized circulating transthyretin (TTR) and retinol binding protein 4 (RBP4) levels would be associated with TTR carrier status and correlated with possible evidence of subclinical ATTRv-CA.

METHODS

TTR and RBP4 were measured in blood samples from V122I TTR carriers and age-, sex- and race-matched non-carrier controls (1:2 matching) among Dallas Heart Study participants (phases 1 (DHS-1) and 2 (DHS-2)). Multivariable linear regression models determined factors associated with TTR and RBP4.

RESULTS

There were 40 V122I TTR carriers in DHS-1 and 54 V122I TTR carriers in DHS-2. In DHS-1 and DHS-2, TTR was lower in V122I TTR carriers (p < .001 for both), and RBP4 in DHS-2 was lower in V122I TTR carriers than non-carriers (p = .002). Among V122I TTR carriers, TTR was negatively correlated with markers of kidney function, and limb lead voltage (p < .05 for both) and TTR and RBP4 were correlated with atrial volume in DHS-2 (p < .05).

CONCLUSIONS

V122I TTR carrier status is independently associated with lower TTR and RBP4 in comparison with non-carriers. These findings support the hypothesis that TTR and RBP4 may correlate with evidence of subclinical ATTRv-CA.

Comparison of cardiac involvement, extracardiac manifestations and outcomes between homozygote and heterozygote transthyretin p.Val142Ile (V122I) variant in patients with hereditary transthyretin amyloidosis: a cohort study

BACKGROUND

Hereditary transthyretin (ATTRv) p.Val142Ile (V122I) mutation is the most common inherited cause of cardiac amyloidosis and little is known about the phenotype and outcome of the rare homozygotic genotype. This study aimed to compare phenotypic characteristics and outcomes between heterozygous and homozygous patients with ATTRv V122I amyloidosis.

MATERIAL AND METHODS

This monocentric, observational, retrospective study conducted at the French National Referral Centre for Cardiac Amyloidosis (Henri Mondor Hospital, Créteil), described clinical, electrocardiographic, cardiac imaging features and prognostic data for patients with ATTRv V122I amyloidosis.

RESULTS

Among 185 ATTRv V122I patients identified, 161 were heterozygous and 24 were homozygous. The homozygous frequency was 13%. Onset occured significantly earlier in the homozygotes compared to heterozygotes with earlier median age at diagnosis (67[63-71] years vs 76[70-79] years, p < .001), age at first cardiac symptom (66[61-71] years vs 74[68-78] years, p < .001) and age at first extracardiac symptom (59[52-70] years vs 69[62-75] years, p = .003). Homozygous ATTRv V122I was also associated with greater disease burden with earlier events (death, transplant or hospitalisation for acute heart failure) compared with heterozygotes (71[67-74] vs 78[76-79] years, p = .018).

CONCLUSION

This rare, homozygous V122I cohort confirmed the earlier age of onset, death and cardiac events in this population.

Cardiac amyloidosis and aortic stenosis: a state-of-the-art review

Cardiac amyloidosis is caused by the extracellular deposition of amyloid fibrils in the heart, involving not only the myocardium but also any cardiovascular structure. Indeed, this progressive infiltrative disease also involves the cardiac valves and, specifically, shows a high prevalence with aortic stenosis. Misfolded protein infiltration in the aortic valve leads to tissue damage resulting in the onset or worsening of valve stenosis. Transthyretin cardiac amyloidosis and aortic stenosis coexist in patients > 65 years in about 4-16% of cases, especially in those undergoing transcatheter aortic valve replacement. Diagnostic workup for cardiac amyloidosis in patients with aortic stenosis is based on a multi-parametric approach considering clinical assessment, electrocardiogram, haematologic tests, basic and advanced echocardiography, cardiac magnetic resonance, and technetium labelled cardiac scintigraphy like technetium-99 m (99mTc)-pyrophosphate, 99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid, and 99mTc-hydroxymethylene diphosphonate. However, a biopsy is the traditional gold standard for diagnosis. The prognosis of patients with coexisting cardiac amyloidosis and aortic stenosis is still under evaluation. The combination of these two pathologies worsens the prognosis. Regarding treatment, mortality is reduced in patients with cardiac amyloidosis and severe aortic stenosis after undergoing transcatheter aortic valve replacement. Further studies are needed to confirm these findings and to understand whether the diagnosis of cardiac amyloidosis could affect therapeutic strategies. The aim of this review is to critically expose the current state-of-art regarding the association of cardiac amyloidosis with aortic stenosis, from pathophysiology to treatment.

Uneven burden of cardiac amyloidosis in people of African descent - global imbalance in resources and access

Transthyretin cardiac amyloidosis (TTR-CA) is now increasingly becoming recognized as an important cause of heart failure, and some studies have shown that as much as a third of diastolic heart failure could be attributed to TTR-CA. Black populations are particularly at risk for TTR-CA as the most common form of the disease (hereditary TTR-CA) has a genetic basis and the gene responsible is most prevalent among people with West African ancestry. This perspective piece explores the challenges that individuals of African and Caribbean populations face when confronted with the burden of TTR-CA. Key issues include the absence of rigorous disease registries, deficits in human resources, a lack of infrastructure for testing and treatment, poor awareness and health literacy, financial limitations including an inadequate public health budget, and the absence of social safety nets. To address these challenges, proactive strategies are needed to build infrastructure and local capacity which will provide the framework for an effective response. Interventions should include healthcare financing mechanisms to protect and care for vulnerable and at-risk populations with a long-term strategy of increasing the financial remuneration for health workers in developing countries to prevent the brain drain. Additionally, pharmaceutical companies need to play an active role in promoting inclusive access and global health equity in the access to the new treatments for TTR-CA which predominantly affects Black populations. Collaborative ventures with international centers of excellence can help improve access in these communities, leveraging their expertise and resources.

Predictive Modeling to Assess Pretest Probability of Transthyretin Gene Variants Based on Demographic Information

BACKGROUND

Transthyretin amyloid cardiomyopathy (ATTR-CM) is a morbid condition, though recent advances in diagnosis and therapy stand to change its natural history. Patients' TTR genotype may guide family screening as more treatments and preventive strategies become available. An efficient, intuitive means of determining pretest genetic risk may better inform patients/clinicians when pursuing genetic testing.

METHODS

This is a cohort study of 767 consecutive patients diagnosed with ATTR-CM who underwent genetic testing. Classification and regression trees (CART) analysis created a decision tree assessing likelihood of carrying a pathologic TTR gene variant. Age, sex, and race were used as independent variables. Logistic regression was also performed to model probability of pathologic TTR genotype. The primary outcome was the decision tree's accuracy in 2 separate institutions' ATTR-CM registry.

RESULTS

In our study cohort, 208 patients (27.1%) had ATTRv. Race has served most efficiently as the root node followed by age and sex in a CART algorithm, and showed 88.2% accuracy (75.3% sensitivity, 93.9% specificity) in the validation cohort. The odds of having a TTR gene variant were greater in Black patients compared with non-Black patients (OR, 34.6 [95% CI, 20.5-58.3]; P<0.001). Non-Black patients with ATTR-CM aged 69 years and older had <4% risk of having a predisposing mutation.

CONCLUSIONS

This CART algorithm incorporating age, sex, and race was able to determine which patients with ATTR-CM have pathogenic TTR mutations with high specificity. Non-Black patients diagnosed at age 69 years or older with ATTR-CM have a low likelihood to have ATTRv.

In silico analysis decodes transthyretin (TTR) binding and thyroid disrupting effects of per- and polyfluoroalkyl substances (PFAS)

Transthyretin (TTR) is a homo-tetramer protein involved in the transport of thyroid hormone (thyroxine; T4) in the plasma and cerebrospinal fluid. Many pollutants have been shown to bind to TTR, which could be alarming as disruption in the thyroid hormone system can lead to several physiological problems. It is also indicated that the monomerization of tetramer and destabilization of monomer can lead to amyloidogenesis. Many compounds are identified that can bind to tetramer and stabilize the tetramer leading to the inhibition of amyloid fibril formation. Other compounds are known to bind tetramer and induce amyloid fibril formation. Among the pollutants, per- and polyfluoroalkyl substances (PFAS) are known to disrupt the thyroid hormone system. The molecular mechanisms of thyroid hormone disruption could be diverse, as some are known to bind with thyroid hormone receptors, and others can bind to membrane transporters. Binding to TTR could also be one of the important pathways to alter thyroid signaling. However, the molecular interactions that drive thyroid-disrupting effects of long-chain and short-chain PFASs are not comprehensively understood at the molecular level. In this study, using a computational approach, we show that carbon chain length and functional group in PFASs are structural determinants, in which longer carbon chains of PFASs and sulfur-containing PFASs favor stronger interactions with TTR than their shorter-chained counterparts. Interestingly, short-chain PFAS also showed strong binding capacity, and the interaction energy for some was as close to the longer-chain PFAS. This suggests that short-chain PFASs are not completely safe, and their use and build-up in the environment should be carefully regulated. Of note, TTR homologs analysis suggests that thyroid-disrupting effects of PFASs could be most likely translated to TTR-like proteins and other species.

Addressing the routine failure to clinically identify monogenic cases of common disease

Changes in medical practice are needed to improve the diagnosis of monogenic forms of selected common diseases. This article seeks to focus attention on the need for universal genetic testing in common diseases for which the recommended clinical management of patients with specific monogenic forms of disease diverges from standard management and has evidence for improved outcomes.We review evidence from genomic screening of large patient cohorts, which has confirmed that important monogenic case identification failures are commonplace in routine clinical care. These case identification failures constitute diagnostic misattributions, where the care of individuals with monogenic disease defaults to the treatment plan offered to those with polygenic or non-genetic forms of the disease.The number of identifiable and actionable monogenic forms of common diseases is increasing with time. Here, we provide six examples of common diseases for which universal genetic test implementation would drive improved care. We examine the evidence to support genetic testing for common diseases, and discuss barriers to widespread implementation. Finally, we propose recommendations for changes to genetic testing and care delivery aimed at reducing diagnostic misattributions, to serve as a starting point for further evaluation and development of evidence-based guidelines for implementation.

Opportunities for Earlier Diagnosis and Treatment of Cardiac Amyloidosis

Despite the rapid expansion of noninvasive (nonbiopsy) diagnosis, contemporary patients with cardiac amyloidosis too often present with advanced features of disease, such as diminished quality of life, elevated natriuretic peptides, and advanced heart failure. Therapeutics for transthyretin cardiomyopathy (ATTR-CM) are most effective when administered before significant symptoms of cardiac dysfunction manifest, making early identification of affected individuals of paramount importance. Community engagement and ensuring that a broad range of clinicians have working knowledge of how to screen for ATTR-CM in everyday practice will be an important step in moving disease identification further upstream. However, reliance on the appropriate and timely diagnosis by individual clinicians may continue to underperform. This review highlights how targeted screening of special populations may facilitate earlier diagnosis. Systems of care that operationalize screening of high-risk subpopulations and prospective validation of novel approaches to ATTR-CM identification are needed.