Hereditary Transthyretin Amyloidosis (hATTR) with Polyneuropathy Clusters Are Located in Ancient Mining Districts: A Possible Geochemical Origin of the Disease.

Hereditary transthyretin amyloidosis (hATTR) with polyneuropathy (formerly known as Familial Amyloid Polyneuropathy (FAP)) is an endemic amyloidosis involving the harmful aggregation of proteins, most commonly transthyretin (TTR) but sometimes also apolipoprotein A-1 or gelsolin. hATTR appears to be transmitted as an autosomal dominant trait. Over 100 point mutations have been identified, with the Val30Met substitution being the most common. Yet, the mechanism of pathogenesis and the overall origin of hATTR remain unclear. Here, we argue that hATTR could be related to harmful metal exposure. hATTR incidence is unevenly distributed globally, and the three largest defined clusters exist in Japan, Portugal, and Sweden. All three disease regions are also ancient mining districts with associated metal contamination of the local environment. There are two main mechanisms for how harmful metals, after uptake into tissues and body fluids, could induce hATTR. First, the metals could directly influence the expression, function, and/or aggregation of the proteins involved in hATTR pathology. Such metal-protein interactions might constitute molecular targets for anti-hATTR drug design. Second, metal exposure could induce hATTR -associated genetic mutations, which may have happened several generations ago. These two mechanisms can occur in parallel. In conclusion, the possibility that hATTR could be related to metal exposure in geochemically defined regions deserves further attention.

Targeting transthyretin - Mechanism-based treatment approaches and future perspectives in hereditary amyloidosis.

The liver-derived, circulating transport protein transthyretin (TTR) is the cause of systemic hereditary (ATTRv) and wild-type (ATTRwt) amyloidosis. TTR stabilization and knockdown are approved therapies to mitigate the otherwise lethal disease course. To date, the variety in phenotypic penetrance is not fully understood. This systematic review summarizes the current literature on TTR pathophysiology with its therapeutic implications. Tetramer dissociation is the rate-limiting step of amyloidogenesis. Besides destabilizing TTR mutations, other genetic (RBP4, APCS, AR, ATX2, C1q, C3) and external (extracellular matrix, Schwann cell interaction) factors influence the type of onset and organ tropism. The approved small molecule tafamidis stabilizes the tetramer and significantly decelerates the clinical course. By sequence-specific mRNA knockdown, the approved small interfering RNA (siRNA) patisiran and antisense oligonucleotide (ASO) inotersen both significantly reduce plasma TTR levels and improve neuropathy and quality of life compared to placebo. With enhanced hepatic targeting capabilities, GalNac-conjugated siRNA and ASOs have recently entered phase III clinical trials. Bivalent TTR stabilizers occupy both binding groves in vitro, but have not been tested in trials so far. Tolcapone is another stabilizer with the potential to cross the blood-brain barrier, but its half-life is short and liver failure a potential side effect. Amyloid-directed antibodies and substances like doxycycline aim at reducing the amyloid load, however, none of the yet developed antibodies has successfully passed clinical trials. ATTR-amyloidosis has become a model disease for pathophysiology-based treatment. Further understanding of disease mechanisms will help to overcome the remaining limitations, including application burden, side effects, and blood-brain barrier permeability.

A Trans-acting Factor May Modify Age at Onset in Familial Amyloid Polyneuropathy ATTRV30M in Portugal.

Although all familial amyloid polyneuropathy (FAP) ATTRV30M patients carry the same causative mutation, early (<40) and late-onset forms (≥50 years) of FAP may coexist in the same family. However, this variability in age at onset is still unexplained. To identify modifiers closely linked to the TTR locus that may in part be associated with age at onset of FAP ATTRV30M, in particular in a group of very early-onset patients (≤30 years) when compared with late-onset individuals. A clinical genetic study at a referral center comprising a sample of 910 Portuguese individuals includes 589 Val30Met carriers, 102 spouses, and 189 controls from the general population. Haplotype analysis was performed, using eight intragenic single nucleotide polymorphisms (SNPs) at the TTR locus. We compared haplotypes frequency in FAP samples and controls and in parent-offspring pairs using appropriated statistical analysis. Haplotype A was the most common in the general population. Noteworthy, haplotype C was more frequent in early-onset (<40) than in late-onset patients (≥50 years) (p = 0.012). When comparing allelic frequencies of each SNP within haplotype C between "very early" (≤30 years) and late-onset (≥50 years) cases, the A allele of rs72922947 was associated with an earlier onset (p = 0.009); this remained significant after a permutation-based correction. Also, the heterozygous genotype (GA) for this SNP was associated with a decrease in mean age at onset of 8.6 years (p = 0.014). We found a more common haplotype (A) linked to the Val30Met variant and a possible modulatory trans effect on age at onset. These findings may lead to potential therapeutical targets.

Motivation to perform presymptomatic testing in portuguese subjects at-risk for late-onset genetic diseases

El papel del psicólogo clínico en el contexto del consejo genético incluye brindar apoyo a los sujetos en riesgo en el proceso de toma de decisiones, independientemente de la decisión adoptada por el sujeto (conociendo o no el resultado de las pruebas genéticas). El estudio que se informa aborda la motivación para realizar las pruebas pre-sintomáticas (PPS) de sujetos en situación de riesgo para tres enfermedades: polineuropatía amiloide familiar (PAF), la enfermedad de Huntington (EH) y la enfermedad de Machado-Joseph (EMJ) y comparar con la motivación para realizar las PPS para hemocromatosis (HH). La muestra consistió en 213 sujetos portugueses que tenían riesgo genético para contraer las tres enfermedades y 31 sujetos en situación de riesgo genético para contraer hemocromatosis. Ellos fueron evaluados con una entrevista para obtener datos sociodemográficos y debían responder a una pregunta sobre la motivación para llevar a cabo las pruebas pre-sintomáticas. Se obtuvieron siete categorías principales y las siguientes son las más significativas para PAF, EH y EMJ: razones relacionadas con el futuro, razones relacionadas con los demás y razones relacionadas con la curiosidad y la necesidad de conocer. Para hemocromatosis, las más importantes resultaron ser razones relacionadas con los demás y las relacionadas con las características de la enfermedad. La motivación para realizar el test pre-sintomático (PST) de la PAF, EH y EMJ es externa y sin relación con la enfermedad, mientras que la motivación de los sujetos en situación de riesgo para la HH está relacionada con la enfermedad. Las razones relacionadas con los demás es una motivación común en ambos grupos. A los sujetos también les preocupa la posibilidad de transmitir la enfermedad a sus hijos.

The role of the clinical psychologist in the context of genetic counseling includes support for the process of decision-making for subjects at-risk, regardless of the decision that was made. For this, it is important to know the motivations behind these decisions. What may be considered advant-ageous and justifiable reasons to perform the PST for genetic diseases from the medical and public point of view, i.e., planning for the future, helping in the choice of a profession, family planning, improving quality of life and contributing to health, may not be recognized as such by the individual seeking the PST. This study addresses the motivation to perform the presymptomatic testing (PST) of subjects at-risk for three diseases, Familial Amyloid Polyneuro pathy (FAP), Huntington's disease (HD), and Machado-Joseph disease (MJD), compared with the motivation to perform the PST for Hemochromatosis (HH). FAP, HD and MJD are three genetic (monogenic) autosomal dominant late-onset diseases (LON-Ds) with no cure. FAP is a progressive sensorimotor and autonomic neuropathy of adult hood. HD is characterized by a triad of clinical symptoms of chorea (motor, cognitive and psychiatric symptoms), emotional distress and cognitive decline. MJD is characterized by slowly progressive clumsiness in the arms and legs, a staggering lurching gait, sometimes mistaken for drunkenness, difficulty with speech and swallowing, involuntary eye movements, and may be accompanied by double vision or bulging eyes, and lower limb spasticity. HH is a disease in which too much iron accumulates in parenchymal organs, leading to iron overload and subsequent organ toxicity and failure. The study participants consisted in 213 subjects at genetic risk for FAP, HD, and MJD and 31 subjects at genetic risk for HH, that were assessed through an interview to obtain sociodemographic data and the answer to one question about motivation to perform PST: "Which were the reasons that led you to perform the predictive test? "This study was carried out in Center for Predictive and Preventive Genetics (CGPP), Institute for Molecular and Cell Biology (IBMC), Porto (Portugal). This research used a mixed-method, since qualitative and quantitative techniques of data analysis were used. Before deciding to seek genetic counseling and to know their genetic status, subjects at-risk have naturally considered their motives and it was probably the pro-counseling reasons the ones dictating the motivation to perform the PST. This may suggest that in fact there is a prior self-selection to the test, i.e. only those considering to have emotional skills to go through the process, performing the test. Seven major categories were obtained. The most significant ones for FAP, HD and MJD were reasons related to the future, reasons related to others and reasons related to curiosity and to the need to know. For HH, the most important ones were reasons related to others and reasons related to the characteristics of the disease. The motivation of subjects at-risk to perform the PST for FAP, HD and MJD is external and unrelated to the disease, while the motivation of subjects at-risk to perform the PST for HH is related to the disease. Reasons related to others area common motivation: as subjects at-risk for FAP, HD and MJD, subjects at-risk for HH also chose reasons related to others as one of the most important motivations to carry out the PST. These subjects also care about the fact that they can transmit the disease to their children and care about other family members which are already ill. The category reasons related to others includes sub-categories that identify the person and the situation that led to the decision to perform a PST. Subjects at-risk are also concerned about the fact that they have to decide whether or not to have children and its economic implications.

Subjects At-Risk for Genetic Diseases in Portugal: Illness Representations.

This study investigates illness representations of subjects at-risk for 3 autosomal dominant late-onset disorders: Familial Amyloid Polyneuropathy (FAP) TTR V30M, Huntington's disease (HD) and Machado-Joseph disease (MJD), comparing them with the illness representations of subjects at-risk for Hemochromatosis (HH). The present study included a clinical group that consisted of 213 subjects at genetic risk (FAP, HD and MJD), comprising 174 subjects at-risk for FAP, 34 subjects at-risk for HD and only 5 subjects at-risk for MJD; and the control group consisting of 31 subjects at genetic risk for HH. All subjects at-risk were undergoing the process of genetic counseling to learn their genetic status (carrier or non-carrier). Subjects were assessed through a semi-structured single interview, in order to obtain sociodemographic data and the answer to an open-ended question relating to the illness representation issue: "What does this illness mean to you?/ What is this disease to you?" It was in the subjects' metaphors that subjects best expressed what they felt regarding the disease and the situation of being at-risk for this disease. Family is their mirror and their source of learning and, therefore, it is inevitable that family is related to the meaning of the disease itself.

Structural stabilization of transthyretin by a new compound, 6-benzoyl-2-hydroxy-1H-benzo[de]isoquinoline-1,3(2H)-dione.

Familial amyloid polyneuropathy (FAP) is a genetic, adult-onset, neurodegenerative disorder caused by amyloid formation of transthyretin (TTR), a thyroxine-binding protein. Mutation in TTR causes a propensity of TTR tetramer to dissociate to monomer, which is the first step to amyloidosis. Thus, a drug that can stabilize the tetramer structure will have therapeutic benefit. Here, by virtual screening and biochemical assays, we identified small molecule 6-benzoyl-2-hydroxy-1H-benzo[de]isoquinoline-1,3(2H)-dione (L6) that can prevent the dissociation of TTR to monomer. X-ray crystallography reveals that L6 binds to the T4 binding pocket of TTR. These findings show that L6 is a candidate TTR stabilizer.

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

OBJECTIVE: To evaluate the long-term efficacy and safety of diflunisal in late-onset familial amyloid polyneuropathy (FAP) in a Japanese endemic area. METHODS: Consecutive six FAP patients (mean age: 65.8 ± 7.3 years) with a transthyretin (TTR) Val30Met mutation from an endemic area of late-onset FAP were prospectively recruited to an open label study with oral diflunisal (250 mg twice a day). We evaluated clinical symptoms, Kumamoto FAP score, modified body mass index (mBMI), Medical Research Council sum score, nerve conduction studies (NCS), electrocardiogram (ECG), ECG Holter monitor test, echocardiography, and (123)iodine-metaiodobenzylguanidine ((123)I-MIBG) myocardial scintigraphy. RESULTS: One patient ceased to take diflunisal because of hematuria which was reversible. The other five patients were treated with diflunisal for 3-5 (4.4 ± 0.9 years) years. Autonomic symptoms (orthostatic hypotension and gastrointestinal symptoms) disappeared after treatment in two of the four patients with the symptoms. Delayed heart to mediastinum ratio on (123)I-MIBG imaging, a marker of cardiac postganglionic sympathetic nerve function, increased during the three-year treatment. mBMI was maintained through observation period. While, motor and sensory symptoms, Kumamoto FAP scores, and data on NCS gradually deteriorated. CONCLUSION: Diflunisal might be effective especially for autonomic dysfunction in late-onset FAP with a TTR Val30Met mutation.