Efficacy of diflunisal on autonomic dysfunction of late-onset familial amyloid polyneuropathy (TTR Val30Met) in a Japanese endemic area

Characterising diflunisal as a transthyretin kinetic stabilizer at relevant concentrations in human plasma using subunit exchange

Transthyretin (TTR) dissociation is the rate limiting step for both aggregation and subunit exchange. Kinetic stabilisers, small molecules that bind to the native tetrameric structure of TTR, slow TTR dissociation and inhibit aggregation. One such stabiliser is the non-steroidal anti-inflammatory drug (NSAID), diflunisal, which has been repurposed to treat TTR polyneuropathy. Previously, we compared the efficacy of diflunisal, tafamidis, tolcapone, and AG10 as kinetic stabilisers for transthyretin. However, we could not meaningfully compare diflunisal because we were unsure of its plasma concentration after long-term oral dosing. Herein, we report the diflunisal plasma concentrations measured by extraction, reversed phase HPLC separation, and fluorescence detection after long-term 250 mg BID oral dosing in two groups: a placebo-controlled diflunisal clinical trial group and an open-label Japanese polyneuropathy treatment cohort. The measured mean diflunisal plasma concentration from both groups was 282.2 μ M ±   143.7 μ M (mean ± standard deviation). Thus, quantification of TTR kinetic stabilisation using subunit exchange was carried out at 100, 200, 300, and 400 μM diflunisal concentrations, all observed in patients after 250 mg BID oral dosing. A 250 μ M diflunisal plasma concentration reduced the wild-type TTR dissociation rate in plasma by 95%, which is sufficient to stop transthyretin aggregation, consistent with the clinical efficacy of diflunisal for ameliorating transthyretin polyneuropathy.

Amyloid Disassembly: What Can We Learn from Chaperones?

Protein aggregation and subsequent accumulation of insoluble amyloid fibrils with cross-β structure is an intrinsic characteristic of amyloid diseases, i.e., amyloidoses. Amyloid formation involves a series of on-pathway and off-pathway protein aggregation events, leading to mature insoluble fibrils that eventually accumulate in multiple tissues. In this cascade of events, soluble oligomeric species are formed, which are among the most cytotoxic molecular entities along the amyloid cascade. The direct or indirect action of these amyloid soluble oligomers and amyloid protofibrils and fibrils in several tissues and organs lead to cell death in some cases and organ disfunction in general. There are dozens of different proteins and peptides causing multiple amyloid pathologies, chief among them Alzheimer's, Parkinson's, Huntington's, and several other neurodegenerative diseases. Amyloid fibril disassembly is among the disease-modifying therapeutic strategies being pursued to overcome amyloid pathologies. The clearance of preformed amyloids and consequently the arresting of the progression of organ deterioration may increase patient survival and quality of life. In this review, we compiled from the literature many examples of chemical and biochemical agents able to disaggregate preformed amyloids, which have been classified as molecular chaperones, chemical chaperones, and pharmacological chaperones. We focused on their mode of action, chemical structure, interactions with the fibrillar structures, morphology and toxicity of the disaggregation products, and the potential use of disaggregation agents as a treatment option in amyloidosis.

Hereditary transthyretin amyloidosis overview

Hereditary amyloidogenic transthyretin (ATTRv) amyloidosis is a rare autosomal dominantly inherited disorder caused by mutations in the transthyretin (TTR) gene. The pathogenetic model of ATTRv amyloidosis indicates that amyloidogenic, usually missense, mutations destabilize the native TTR favouring the dissociation of the tetramer into partially unfolded species that self-assemble into amyloid fibrils. Amyloid deposits and monomer-oligomer toxicity are the basis of multisystemic ATTRv clinical involvement. Peripheral nervous system (autonomic and somatic) and heart are the most affected sites. In the last decades, a better knowledge of pathomechanisms underlying the disease led to develop novel and promising drugs that are rapidly changing the natural history of ATTRv amyloidosis. Thus, clinicians face the challenge of timely diagnosis for addressing patients to appropriate treatment. As well, the progressive nature of ATTRv raises the issue of presymptomatic testing and risk management of carriers. The main aim of this review was to focus on what we know about ATTRv so far, from pathogenesis to clinical manifestations, diagnosis and hence patient's monitoring and treatment, and from presymptomatic testing to management of carriers.

The discovery and development of transthyretin amyloidogenesis inhibitors: what are the lessons?

Transthyretin (TTR) is associated with several human amyloid diseases. Various kinetic stabilizers have been developed to inhibit the dissociation of TTR tetramer and the formation of amyloid fibrils. Most of them are bisaryl derivatives, natural flavonoids, crown ethers and carborans. In this review article, we focus on TTR tetramer stabilizers, genetic therapeutic approaches and fibril remodelers. The binding modes of typical bisaryl derivatives, natural flavonoids, crown ethers and carborans are discussed. Based on knowledge of the binding of thyroxine to TTR tetramer, many stabilizers have been screened to dock into the thyroxine binding sites, leading to TTR tetramer stabilization. Particularly, those stabilizers with unique binding profiles have shown great potential in developing the therapeutic management of TTR amyloidogenesis.

Current and Emerging Therapies for Hereditary Transthyretin Amyloidosis: Strides Towards a Brighter Future

The past few years have witnessed an unprecedented acceleration in the clinical development of novel therapeutic options for hereditary transthyretin amyloidosis. Recently approved agents and drugs currently under investigation not only represent a major breakthrough in this field but also provide validation of the therapeutic potential of innovative approaches, like RNA interference and CRISPR-Cas9-mediated gene editing, in rare inherited disorders. In this review, we describe the evolving therapeutic landscape for hereditary transthyretin amyloidosis and discuss how this highly disabling and fatal condition is turning into a treatable disease. We also provide an overview of the molecular mechanisms involved in transthyretin (TTR) amyloid formation and regression, to highlight how a deeper understanding of these processes has contributed to the identification of novel treatment targets. Finally, we focus on major areas of uncertainty and unmet needs that deserve further efforts to improve long-term patients' outcomes and allow for a brighter future.

Modulation of the Mechanisms Driving Transthyretin Amyloidosis

Transthyretin (TTR) amyloidoses are systemic diseases associated with TTR aggregation and extracellular deposition in tissues as amyloid. The most frequent and severe forms of the disease are hereditary and associated with amino acid substitutions in the protein due to single point mutations in the TTR gene (ATTRv amyloidosis). However, the wild type TTR (TTR wt) has an intrinsic amyloidogenic potential that, in particular altered physiologic conditions and aging, leads to TTR aggregation in people over 80 years old being responsible for the non-hereditary ATTRwt amyloidosis. In normal physiologic conditions TTR wt occurs as a tetramer of identical subunits forming a central hydrophobic channel where small molecules can bind as is the case of the natural ligand thyroxine (T₄). However, the TTR amyloidogenic variants present decreased stability, and in particular conditions, dissociate into partially misfolded monomers that aggregate and polymerize as amyloid fibrils. Therefore, therapeutic strategies for these amyloidoses may target different steps in the disease process such as decrease of variant TTR (TTRv) in plasma, stabilization of TTR, inhibition of TTR aggregation and polymerization or disruption of the preformed fibrils. While strategies aiming decrease of the mutated TTR involve mainly genetic approaches, either by liver transplant or the more recent technologies using specific oligonucleotides or silencing RNA, the other steps of the amyloidogenic cascade might be impaired by pharmacologic compounds, namely, TTR stabilizers, inhibitors of aggregation and amyloid disruptors. Modulation of different steps involved in the mechanism of ATTR amyloidosis and compounds proposed as pharmacologic agents to treat TTR amyloidosis will be reviewed and discussed.

Advances in Treatment of ATTRv Amyloidosis: State of the Art and Future Prospects

Hereditary amyloid transthyretin (ATTRv) amyloidosis with polyneuropathy is a progressive disease that is transmitted as an autosomal dominant trait and characterized by multiple organ failure, including axonal sensory-motor neuropathy, cardiac involvement, and autonomic dysfunction. Liver transplantation (LT) and combined heart-liver transplantation, introduced in the 1990s, have been the only therapies for almost two decades. In 2011, tafamidis meglumine became the first specific drug approved by regulatory agencies, since then the attention toward this disease has progressively increased and several drugs with different mechanisms of action are now available. This review describes the drugs already on the market, those that have shown interesting results although not yet approved, and those currently being tested.

Orthostatic hypotension in hereditary transthyretin amyloidosis: epidemiology, diagnosis and management

Purpose

Neurogenic orthostatic hypotension is a prominent and disabling manifestation of autonomic dysfunction in patients with hereditary transthyretin (TTR) amyloidosis affecting an estimated 40–60% of patients, and reducing their quality of life. We reviewed the epidemiology and pathophysiology of neurogenic orthostatic hypotension in patients with hereditary TTR amyloidosis, summarize non-pharmacologic and pharmacological treatment strategies and discuss the impact of novel disease-modifying treatments such as transthyretin stabilizers (diflunisal, tafamidis) and RNA interference agents (patisiran, inotersen).

Methods

Literature review.

Results

Orthostatic hypotension in patients with hereditary transthyretin amyloidosis can be a consequence of heart failure due to amyloid cardiomyopathy or volume depletion due to diarrhea or drug effects. When none of these circumstances are apparent, orthostatic hypotension is usually neurogenic, i.e., caused by impaired norepinephrine release from sympathetic postganglionic neurons, because of neuronal amyloid fibril deposition.

Conclusions

When recognized, neurogenic orthostatic hypotension can be treated. Discontinuation of potentially aggravating medications, patient education and non-pharmacologic approaches should be applied first. Droxidopa (Northera^®), a synthetic norepinephrine precursor, has shown efficacy in controlled trials of neurogenic orthostatic hypotension in patients with hereditary TTR amyloidosis and is now approved in the US and Asia. Although they may be useful to ameliorate autonomic dysfunction in hereditary TTR amyloidosis, the impact of disease-modifying treatments on neurogenic orthostatic hypotension is still uninvestigated.

TTR (Transthyretin) Stabilizers Are Associated With Improved Survival in Patients With TTR Cardiac Amyloidosis

BACKGROUND

TTR (transthyretin) cardiac amyloidosis is caused by dissociation of TTR into monomers, which misassemble into amyloid fibrils. TTR stabilizers act at the dimer-dimer interface to prevent dissociation. We investigated differences in survival among patients with TTR cardiac amyloidosis on stabilizer medications compared with those not on stabilizers.

METHODS AND RESULTS

A retrospective study of patients with TTR cardiac amyloidosis presenting to a single center was conducted. Baseline characteristics were compared between those treated with stabilizers and those not treated with stabilizers. Cox proportional hazards modeling assessed for univariate predictors of the composite outcome of death or orthotopic heart transplant (OHT). Multivariable Cox proportional hazards assessed whether stabilizer treatment was independently associated with improved death or OHT after controlling for significant univariate predictors. One hundred twenty patients (mean age, 75±8, 88% male) were included: 29 patients who received stabilizers and 91 patients who did not. Stabilizer use was associated with a lower risk of the combined end point of death or OHT (hazard ratio, 0.32; 95% confidence interval, 0.18-0.58; P<0.0001). Subjects treated with stabilizers were more likely to be of White race (93% versus 55%; P<0.001), classified as New York Heart Association classes I and II (79% versus 38%; P=0.002), less likely to have a mutation (10% versus 36%; P=0.010), have lower troponin I (median 0.06 versus 0.12 ng/mL; P=0.002), and higher left ventricular ejection fraction (49% versus 40%; P=0.011), suggesting earlier stage of disease. In multivariable Cox analysis, the association between stabilizer and death or OHT persisted when adjusted for all noncollinear univariate predictors with P<0.05 (hazard ratio, 0.37; 95% confidence interval, 0.19-0.75; P=0.003).

CONCLUSIONS

TTR stabilizers are associated with decreased death and OHT in TTR cardiac amyloidosis. These results need to be confirmed by ongoing randomized clinical trials.

Imaging cardiac innervation in amyloidosis

Cardiac amyloidosis is a form of restrictive cardiomyopathy resulting in heart failure and potential risk on arrhythmia, due to amyloid infiltration of the nerve conduction system and the myocardial tissue. The prognosis in this progressive disease is poor, probably due the development of cardiac arrhythmias. Early detection of cardiac sympathetic innervation disturbances has become of major clinical interest, because its occurrence and severity limits the choice of treatment. The use of iodine-123 labelled metaiodobenzylguanidine ([I-123]MIBG), a chemical modified analogue of norepinephrine, is well established in patients with heart failure and plays an important role in evaluation of sympathetic innervation in cardiac amyloidosis. [I-123]MIBG is stored in vesicles in the sympathetic nerve terminals and is not catabolized like norepinephrine. Decreased heart-to-mediastinum ratios on late planar images and increased wash-out rates indicate cardiac sympathetic denervation and are associated with poor prognosis. Single photon emission computed tomography provides additional information and has advantages for evaluating abnormalities in regional distribution in the myocardium. [I-123]MIBG is mainly useful in patients with hereditary and wild-type ATTR cardiac amyloidosis, not in AA and AL amyloidosis. The potential role of positron emission tomography for cardiac sympathetic innervation in amyloidosis has not yet been identified.

The Extracellular Protein, Transthyretin Is an Oxidative Stress Biomarker

The extracellular protein, transthyretin is responsible for the transport of thyroxin and retinol binding protein complex to the various parts of the body. In addition to this transport function, transthyretin has also been involved in cardiovascular malfunctions, polyneuropathy, psychological disorders, obesity and diabetes, etc. Recent developments have evidenced that transthyretin has been associated with many other biological functions that are directly or indirectly associated with the oxidative stress, the common hallmark for many human diseases. In this review, we have attempted to address that transthyretin is associated with oxidative stress and could be an important biomarker. Potential future perspectives have also been discussed.

Tafamidis, a Noninvasive Therapy for Delaying Transthyretin Familial Amyloid Polyneuropathy: Systematic Review and Meta-Analysis

Background and Purpose

Tafamidis functions to delay the loss of function in transthyretin familial amyloid polyneuropathy (TTR-FAP), which is a rare inherited amyloidosis with progressive sensorimotor and autonomic polyneuropathy. This systematic literature review and meta-analysis evaluated the efficacy and safety of tafamidis in TTR-FAP patients, with the aim of improving the evidence-based medical evidence of this treatment option for TTP-FAP.

Methods

A systematic search of the English-language literature in five databases was performed through to May 31, 2018 by two reviewers who independently extracted data and assessed the risk of bias. We extracted efficacy and safety outcomes and performed a meta-analysis. Statistical tests were performed to check for heterogeneity and publication bias.

Results

The meta-analysis identified six relevant studies. The tafamidis group showed smaller changes from baseline in the Neuropathy Impairment Score–Lower Limbs [mean difference (MD)=−3.01, 95% confidence interval (CI)=−3.26 to −2.75, p<0.001] and the Norfolk Quality of Life-Diabetic Neuropathy total quality of life score (MD=−6.67, 95% CI=−9.70 to −3.64, p<0.001), and a higher modified body mass index (MD=72.45, 95% CI=69.41 to 75.49, p<0.001), with no significant difference in total adverse events [odds ratio (OR)=0.69, 95% CI=0.35 to 1.35, p=0.27]. The incidence of adverse events did not differ between tafamidis and placebo treatment except for fatigue (OR=0.13, 95% CI=0.02 to 0.72, p=0.02) and hypesthesia (OR=0.16, 95% CI=0.03 to 0.92, p=0.04).

Conclusions

This systematic review and meta-analysis has demonstrated that tafamidis delays neurologic progression and preserves a better nutritional status and the quality of life. The rates of adverse events did not differ between the patients in the tafamidis and placebo groups. Tafamidis might be a safer noninvasive option for patients with TTR-FAP.

Autonomic involvement in hereditary transthyretin amyloidosis (hATTR amyloidosis)

PURPOSE

Hereditary transthyretin amyloidosis (hATTR amyloidosis) is a progressive disease primarily characterized by adult-onset sensory, motor, and autonomic neuropathy. In this article, we discuss the pathophysiology and principal findings of autonomic neuropathy in hATTR amyloidosis, the most common methods of assessment and progression, and its relation as a predictive risk factor or a measure of progression in the natural history of the disease.

METHODS

A literature search was performed using the terms "autonomic neuropathy," "dysautonomia," and "autonomic symptoms" in patients with hereditary transthyretin amyloidosis and familial amyloid polyneuropathy.

RESULTS

Various scales to measure autonomic function have been employed, particularly within the major clinical trials, to assess novel therapies for the disease. Most of the evaluations were taken from diabetic clinical trials. Questionnaires include the COMPASS-31 and Norfolk QOL autonomic nerve function domain, whereas clinical evaluations comprise HRDB and the orthostatic tolerance test. Several treatment options are being employed although only diflunisal and tafamidis have reported improvement in the autonomic abnormalities.

CONCLUSIONS

Autonomic nerves are often affected before motor nerve impairment, and dysautonomia may support the diagnosis of hATTR amyloidosis when differentiating from other adult-onset progressive neuropathies and from other types of amyloidosis. Most of the progression of autonomic dysfunction is seen in early stages of the disease, commonly before motor impairment or affection of the overall quality of life. Unfortunately, there is no current single standardized approach to evaluate dysautonomia in hATTR amyloidosis.

Cardiac denervation evidenced by MIBG occurs earlier than amyloid deposits detection by diphosphonate scintigraphy in TTR mutation carriers

PURPOSE

Cardiac involvement in familial transthyretin (TTR) amyloidosis is of major prognostic value, and the development of early-diagnostic tools that could trigger the use of new disease-modifying treatments is crucial. The aim of our study was to compare the respective contributions of ^99mTc-diphosphonate scintigraphy (DPD, detecting amyloid deposits) and ¹²³I-MIBG (MIBG, assessing cardiac sympathetic denervation) in patients with genetically proven TTR mutation referred for the assessment of cardiac involvement.

METHODS

We prospectively studied 75 consecutive patients (classified as symptomatic or asymptomatic carriers), using clinical evaluation, biomarkers (troponin and BNP), echocardiography, and nuclear imaging. Patients were classified as having normal heart-to-mediastinum (HMR) MIBG uptake ratio 4 h after injection (defined by HM4 ≥ 1.85) or abnormal HM4 < 1.85, and positive DPD uptake (grade ≥ 1 of Perugini classification) or negative DPD uptake.

RESULTS

Among 75 patients, 49 (65%) presented with scintigraphic sympathetic cardiac denervation and 29 (39%) with myocardial diphosphonate uptake. When MIBG was normal, DPD was negative except for two patients. Age was an independent predictor of abnormal scintigraphic result of both MIBG and DPD (HR 1.08 and 1.15 respectively), whereas echocardiographic-derived indicators of increased left ventricular filling pressure (E/e' ratio) was an independent predictor of abnormal MIBG (HR 1.33) and global longitudinal strain of positive DPD (HR 1.45). In asymptomatic patients (n = 31), MIBG was abnormal in 48% (n = 15) among whom 50% had a normal DPD; all those with a normal MIBG (n = 16) had a normal DPD.

CONCLUSIONS

In TTR mutation carriers, cardiac sympathetic denervation evidenced by decreased MIBG uptake is detected earlier than amyloid burden evidenced by DPD. These results raise the possibility of a diagnostic role for MIBG scintigraphy at an early stage of cardiac involvement in TTR-mutated carriers, in addition to its well-established prognostic value.

Recent advances in the noninvasive strategies of cardiac amyloidosis

The heart, like any organ in the body, is susceptible to amyloid deposition. Although more than 30 types of protein can cause amyloidosis, only two types commonly deposit in the ventricular myocardium: amyloid light chain and amyloid transthyretin. Amyloid cardiomyopathy is usually a major determinant of patient outcomes, and the diagnosis of heart involvement can be often relatively under-diagnosed, owing to nonspecific presenting symptoms and signs at a subclinical stage. The diagnosis of cardiac amyloidosis is usually performed by endomyocardial biopsy; however, the invasive nature and related high-risk complications restrict its wide use in clinical settings. Recently, with the advent of innovative techniques used for evaluating cardiac amyloidosis, noninvasive methods become increasingly important, especially in earlier diagnosis, distinguishing typing, risk prediction and response to treatment. Here, we will review recent developments in the noninvasive methods used in the assessment of cardiac amyloidosis, focused on the laboratory biomarkers and imaging modalities.

Diflunisal inhibits prestin by chloride-dependent mechanism

The motor protein prestin is a member of the SLC26 family of anion antiporters and is essential to the electromotility of cochlear outer hair cells and for hearing. The only direct inhibitor of electromotility and the associated charge transfer is salicylate, possibly through direct interaction with an anion-binding site on prestin. In a screen to identify other inhibitors of prestin activity, we explored the effect of the non-steroid anti-inflammatory drug diflunisal, which is a derivative of salicylate. We recorded prestin activity by whole-cell patch clamping HEK cells transiently expressing prestin and mouse outer hair cells. We monitored the impact of diflunisal on the prestin-dependent non-linear capacitance and electromotility. We found that diflunisal triggers two prestin-associated effects: a chloride independent increase in the surface area and the specific capacitance of the membrane, and a chloride dependent inhibition of the charge transfer and the electromotility in outer hair cells. We conclude that diflunisal affects the cell membrane organization and inhibits prestin-associated charge transfer and electromotility at physiological chloride concentrations. The inhibitory effects on hair cell function are noteworthy given the proposed use of diflunisal to treat neurodegenerative diseases.

Transthyretin amyloidosis: an under-recognized neuropathy and cardiomyopathy

Transthyretin (TTR) amyloidosis (ATTR amyloidosis) is an underdiagnosed and important type of cardiomyopathy and/or polyneuropathy that requires increased awareness within the medical community. Raising awareness among clinicians about this type of neuropathy and lethal form of heart disease is critical for improving earlier diagnosis and the identification of patients for treatment. The following review summarizes current criteria used to diagnose both hereditary and wild-type ATTR (ATTRwt) amyloidosis, tools available to clinicians to improve diagnostic accuracy, available and newly developing therapeutics, as well as a brief biochemical and biophysical background of TTR amyloidogenesis.

One mutation, two distinct disease variants: unravelling the impact of transthyretin amyloid fibril composition

Although hereditary transthyretin (h-ATTR) amyloidosis is a monogenetic disease, a large variation in its phenotype has been observed. The common hypothesis of amyloid fibril formation involves dissociation of the transthyretin (TTR) tetramer into monomers that after misfolding reassemble into amyloid fibrils. This notion is partly challenged by the finding of two distinct types of amyloid fibrils. One of these, type A, consists of C-terminal ATTR fragments and full-length TTR, whereas the other, type B, consists only of full-length TTR. All organs of an individual patient contain ATTR deposits of either type A or type B fibrils, and the composition in each individual remains unchanged over time. The finding of two distinct types of ATTR fibrils suggests that there are at least two different pathways in operation for ATTR fibril formation. For the most common European mutation, TTR Val30Met, ATTR fibril composition is related to the outcome of liver transplantation, which is the first successful treatment for the disease, and the penetrance of the trait. In addition, the presence of C-terminal ATTR fragments has an impact on the affinity for various tracers used for noninvasive imaging of amyloid depositions such as 99 m-technetium-diphosphono-propanodicarboxylic acid scintigraphy and positron emission tomography utilizing Pittsburgh component B, and even for the gold standard diagnostic procedure, tissue biopsy stained by Congo red and examined under polarized light. The importance of amyloid fibril composition needs to be taken into consideration when designing clinical trials of treatment modalities, and also in the evaluation of diagnostic methods such as imaging techniques.

Current and Future Treatment Approaches in Transthyretin Familial Amyloid Polyneuropathy

OPINION STATEMENT

Treatment of transthyretin familial amyloid polyneuropathy (TTR FAP) must be tailored to disease stage. Patients with early stage disease (i.e., without major impairment in walking ability), especially younger patients, should be referred as soon as possible for liver transplantation (LT) in the absence of major comorbid conditions. LT remains the most effective treatment option to date and should be offered to these patients as early as possible. Bridging therapy with an oral TTR stabilizer (tafamidis or diflunisal, according to local access to these treatments) should be started as soon as the diagnosis of TTR FAP is established. Early stage patients who do not wish to or have contraindications to LT should be treated with an oral TTR stabilizer or get access to the newly developed therapeutic options (IONIS TTR-Rx, patisiran, doxycycline/TUDCA). Late stage patients (presenting with significant walking impairment) are usually older and notoriously difficult to treat. They should be offered an oral TTR stabilizer but are not candidates for LT due to a significant rate of perioperative complications and increased risk of progressive neurological and especially cardiac disease despite LT. Access to the different therapies in development should also be considered depending on respective inclusion and exclusion criteria. The abovementioned treatment options were mostly validated in Val30Met mutation patients, but should also be offered to non-Val30Met patients, although mortality rates after LT are higher in these patients. Treatment decisions should be made on an individual basis. Screening for heart, eye, and renal involvement is mandatory for every patient at disease diagnosis and regularly thereafter, even in transplanted patients. Symptomatic treatment should be offered as needed, as well as genetic counseling to at-risk family members. Asymptomatic mutation carriers should benefit from regular screening for early symptoms of disease. Current therapeutic management of TTR FAP will hopefully be changed in the near future with data from the ongoing phase 2/3 studies testing the TTR gene silencing agents. In the longer term, it is likely that combined therapeutic approaches will be necessary to reverse the disease process.

Cardiac Dysautonomia Predicts Long-Term Survival in Hereditary Transthyretin Amyloidosis After Liver Transplantation

OBJECTIVES

This study sought to compare techniques evaluating cardiac dysautonomia and predicting the risk of death of patients with hereditary transthyretin amyloidosis (mATTR) after liver transplantation (LT).

BACKGROUND

mATTR is a multisystemic disease involving mainly the heart and the peripheral nervous system. LT is the reference treatment, and pre-operative detection of high-risk patients is critical. Cardiovascular dysautonomia is commonly encountered in ATTR and may affect patient outcome, although it is not known yet which technique should be used in the field to evaluate it.

METHODS

In a series of 215 consecutive mATTR patients who underwent LT, cardiac dysautonomia was assessed by a dedicated clinical score, time-domain heart rate variability, ¹²³-meta-iodobenzylguanidine heart/mediastinum (¹²³-MIBG H/M) ratio on scintigraphy, and heart rate response to atropine (HRRA).

RESULTS

Patient median age was 43 years, 62% were male and 69% carried the Val30Met mutation. Cardiac dysautonomia was documented by at least 1 technique for all patients but 6 (97%). In univariate analysis, clinical score, ¹²³-MIBG H/M ratio and HRRA were associated with mortality but not heart rate variability. The ¹²³-MIBG H/M ratio and HRRA had greater area under the curve (AUC) of receiver-operating characteristic curves than clinical score and heart rate variability (AUC: 0.787, 0.748, 0.656, and 0.523, respectively). Multivariate score models were then built using the following variables: New York Heart Association functional class, interventricular septum thickness, and either ^123-MIBG H/M ratio (S_MIBG) or HRRA (S_atropine). AUC of S_MIBG and S_atropine were greater than AUC of univariate models, although nonsignificantly (AUC: 0.798 and 0.799, respectively). Predictive powers of S_MIBG, S_atropine, and a reference clinical model (AUC: 0.785) were similar.

CONCLUSIONS

Evaluation of cardiac dysautonomia is a valuable addition for predicting survival of mATTR patients following LT. Among the different techniques that evaluate cardiac dysautonomia, ¹²³-MIBG scintigraphy and heart rate response to atropine had better prognostic accuracy. Multivariate models did not improve significantly prediction of outcome.

Tissue remodeling after interference RNA mediated knockdown of transthyretin in a familial amyloidotic polyneuropathy mouse model

Transthyretin (TTR) deposition in the peripheral nervous system is the hallmark of familial amyloidotic polyneuropathy (FAP). Currently, liver transplantation is the only available treatment to halt the progression of clinical symptoms; however, due to the limitations of this procedure, development of alternative therapeutic strategies is of utmost importance. In this regard, interference RNA (RNAi) targeting TTR is currently in phase III clinical development. To dissect molecular changes occurring in dorsal root ganglia (DRG) upon RNAi-mediated knockdown of TTR, we treated both chronically and acutely an FAP mouse model, in different stages of disease. Our data show that inhibition of TTR expression by the liver with RNAi reverse TTR deposition in DRG, decrease matrix metalloproteinase-2 (MMP-2) protein levels in plasma, inhibit Mmp-2 gene expression and downregulate MMP-9 activity in DRG, indicating extracellular matrix remodeling. Furthermore, protein levels of MMP-2 were found upregulated in plasma samples from FAP patients indicating that MMP-2 might be a novel potential biomarker for FAP diagnosis. Collectively, our data show that silencing TTR liver synthesis in vivo can modulate TTR-induced pathology in the peripheral nervous system and highlight the potential of MMP-2 as a novel disease biomarker.

Recipient aging accelerates acquired transthyretin amyloidosis after domino liver transplantation

Domino liver transplantation (DLT) with liver grafts from patients with hereditary transthyretin (TTR) amyloidosis has been performed throughout the world because of a severe liver graft shortage. Reports of acquired systemic TTR amyloidosis in domino liver recipients have been increasing; however, the precise pathogenesis and clinical course of acquired TTR amyloidosis remains unclear. We analyzed the relationship between the occurrence of acquired amyloidosis and clinical features in 22 consecutive domino liver donors with hereditary TTR amyloidosis (10 males and 12 females; mean age at DLT: 37.2 years; TTR mutations: V30M [n = 19], Y114C [n = 1], L55P [n = 1], and S50I [n = 1]) and 22 liver recipients (16 males and 6 females; mean age at DLT, 46.2 years). The mean times from DLT to amyloid first appearance and transplant recipient symptom onset were 8.2 years and 9.9 years, respectively. Kaplan-Meier analysis and quantification of the amyloid deposition revealed aging of recipients correlated with early de novo amyloid deposition. The sex of donors and recipients and the age, disease duration, and disease severity of donors had no significant effect on the latency of de novo amyloid deposition. In conclusion, our results demonstrate that recipient aging is associated with the early onset de novo amyloidosis. Because acquired amyloidosis will likely increase, careful follow-up for early amyloidosis detection and new treatments, including TTR stabilizers and gene-silencing therapies, are required. Liver Transplantation 22 656-664 2016 AASLD.

Parenteral nutrition improves nutritional status, autonomic symptoms and quality of life in transthyretin amyloid polyneuropathy

Transthyretin familial amyloid polyneuropathy (TTR-FAP) is an inherited amyloidosis, leading to death in about ten years in most cases due to cardiac failure or wasting syndrome. Previous studies showed that modified body mass index was related to time before death, duration of gastrointestinal disturbances, malabsorption and functional capacity. We report two patients in whom nutritional status worsened despite diet modification, hypercaloric supplement and two relevant therapeutic approaches such as liver transplant and tafamidis meglumine, respectively. The first patient, a 52-year-old lady carrying Thr49Ala mutation, had a disease duration of twelve years and had lost weight up to 35 kg because of daily diarrhea. The second patient, a 63-year-old man with Glu89Gln mutation and a disease duration of fifteen years, was in the New York Heart Association (NYHA) Functional Classification class III and his weight was 39 kg. In both cases, a peripherally inserted central catheter was placed for parenteral nutrition. It allowed to improve their nutritional status and clinical conditions, with body weight gains of 11 and 8 kg in a one year follow-up, respectively. Moreover, reduction of autonomic symptoms including postural hypotension, nausea and diarrhoea was recorded with ameliorated quality of life. Our experience suggests that parenteral nutrition may be useful in reducing complications and disabilities in TTR-FAP patients, even when all dietary adjustments have been ineffective. Reasonably, the improvement in nutritional status may prolong survival in TTR-FAP patients.

Diagnosis, Prognosis, and Therapy of Transthyretin Amyloidosis

Transthyretin amyloidosis is a fatal disorder that is characterized primarily by progressive neuropathy and cardiomyopathy. It occurs in both a mutant form (with autosomal dominant inheritance) and a wild-type form (with predominant cardiac involvement). This article guides clinicians as to when the disease should be suspected, describes the appropriate diagnostic evaluation for those with known or suspected amyloidosis, and reviews the interventions currently available for affected patients.

Most recent common ancestor of TTR Val30Met mutation in Italian population and its potential role in genotype-phenotype correlation

INTRODUCTION

Transthyretin (TTR)-related amyloidosis is characterized by autosomal transmission of amyloidogenic mutated TTR. Val30Met is one of the most common amyloidogenic TTR mutations, showing a worldwide distribution with phenotypic heterogeneity among human populations. Multiple founder mutations for Val30Met foci have been hypothesized and the different origins may explain the phenotypic variability. The aim of our study is to determine the origin of Italian Val30Met and to analyze the genetic relationship of other Val30Met foci.

METHODS

We analyzed the origin of Italian Val30Met through 11 microsatellite markers around the TTR gene in 29 patients and 34 healthy controls.

RESULTS

Our genetic analysis showed an estimated age of origin of 34-36 generations ago for the Italian Val30Met. Comparing Italian Val30Met haplotypes with those from Sweden and Portugal highlights relevant differences that seem to be consistent with an independent origin of Italian Val30Met mutation. This genetic evidence agrees with the disease phenotypic variation in these populations.

DISCUSSION AND CONCLUSIONS

Italian Val30Met mutation should have originated before the Portuguese and Swedish Val30Met ones (which arose through independent mutational events). This indicates a genetic diversity in the surrounding regions of three different Val30Met mutations, supporting the hypothesis that TTR non-coding regions may contribute to phenotypic heterogeneity.