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  • 1
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 28 January 2014, Vol.111(4), pp.1539-44
    Description: The Ser52Pro variant of transthyretin (TTR) produces aggressive, highly penetrant, autosomal-dominant systemic amyloidosis in persons heterozygous for the causative mutation. Together with a minor quantity of full-length wild-type and variant TTR, the main component of the ex vivo fibrils was the residue 49-127 fragment of the TTR variant, the portion of the TTR sequence that previously has been reported to be the principal constituent of type A, cardiac amyloid fibrils formed from wild-type TTR and other TTR variants [Bergstrom J, et al. (2005) J Pathol 206(2):224-232]. This specific truncation of Ser52Pro TTR was generated readily in vitro by limited proteolysis. In physiological conditions and under agitation the residue 49-127 proteolytic fragment rapidly and completely self-aggregates into typical amyloid fibrils. The remarkable susceptibility to such cleavage is likely caused by localized destabilization of the β-turn linking strands C and D caused by loss of the wild-type hydrogen-bonding network between the side chains of residues Ser52, Glu54, Ser50, and a water molecule, as revealed by the high-resolution crystallographic structure of Ser52Pro TTR. We thus provide a structural basis for the recently hypothesized, crucial pathogenic role of proteolytic cleavage in TTR amyloid fibrillogenesis. Binding of the natural ligands thyroxine or retinol-binding protein (RBP) by Ser52Pro variant TTR stabilizes the native tetrameric assembly, but neither protected the variant from proteolysis. However, binding of RBP, but not thyroxine, inhibited subsequent fibrillogenesis.
    Keywords: Misfolding ; Protein Aggregation ; Amyloid -- Metabolism ; Prealbumin -- Metabolism ; Proline -- Metabolism ; Serine -- Metabolism
    ISSN: 00278424
    E-ISSN: 1091-6490
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  • 2
    Article
    Article
    BMJ Publishing Group Ltd and British Cardiovascular Society
    Language: English
    In: Heart, 11 November 2012, Vol.98(21), p.1546
    Description: Cardiac amyloidosis of transthyretin fibril protein (ATTR) type is an infiltrative cardiomyopathy characterised by ventricular wall thickening and diastolic heart failure. Increased access to cardiovascular magnetic resonance imaging has led to a marked increase in referrals to our centre of Caucasian patients with wild-type ATTR (senile systemic) amyloidosis and Afro-Caribbean patients with the hereditary ATTR V122I type. Both subtypes present predominantly as isolated cardiomyopathy. The differential diagnosis includes cardiac amyloid light-chain (AL) amyloidosis, which has a poorer prognosis and can be amenable to chemotherapy. We review here the clinical features of cardiac ATTR amyloidosis and describe the diagnostic tests to determine ATTR type. Correct diagnosis is ever more crucial given that several novel therapies for ATTR amyloidosis are on the near horizon.
    Keywords: Cardiac Amyloidosis ; Cardiovascular Mri ; Cardiomyopathy ; Valvular Disease ; Cardiac Function ; Cardiac Remodelling ; Interventional Cardiology ; Non-Coronary Intervention ; Percutaneous Valve Therapy ; Heart Failure ; Systolic Heart Failure ; Diastolic Dysfunction ; Myocardial Disease ; Cardiomyopathy Restrictive
    ISSN: 1355-6037
    ISSN: 13556037
    E-ISSN: 1468-201X
    E-ISSN: 1468201X
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  • 3
    In: Kidney International, 2014
    Description: Amyloidosis results from protein misfolding, and ongoing amyloid deposition can ultimately lead to organ failure and death. Historically, this is a group of diseases with limited treatment options and frequently poor prognosis. However, there are now 'targeted' therapeutics emerging in the form of stabilizers of the precursor protein, inhibitors of fibrillogenesis, fibril disruptors, and blockers of protein translation, transcription, and immunotherapy. We review many of these approaches that are currently being assessed in clinical trials.
    Keywords: Molecular Targeted Therapy ; Amyloidosis -- Drug Therapy ; Prealbumin -- Metabolism;
    ISSN: 0085-2538
    E-ISSN: 15231755
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  • 4
    In: The New England Journal of Medicine, 2005, Vol.352(22), pp.2356-2356
    Description: To the Editor: Familial amyloidotic polyneuropathy is a fatal autosomal dominant disease caused by amyloidogenic genetic variants of transthyretin. The liver is the predominant source of circulating transthyretin, and liver transplantation is the only treatment available for the disease. 1 Livers explanted from patients with familial amyloidotic polyneuropathy contain only microscopic amyloid deposits in hilar vessels and nerves and are otherwise uninvolved. Since 1995, more than 300 such livers removed at transplantation have been used sequentially as donor grafts for recipients with liver cancer or end-stage liver disease, in so-called domino liver transplantation. 2 We report here a case of systemic transthyretin . . .
    Keywords: Adult–Etiology ; Amyloid Neuropathies, Familial–Surgery ; Carcinoma, Hepatocellular–Complications ; Hepatitis C–Chemistry ; Humans–Surgery ; Liver–Adverse Effects ; Liver Neoplasms–Analysis ; Liver Transplantation–Analysis ; Male–Analysis ; Middle Aged–Analysis ; Prealbumin–Analysis ; Prealbumin;
    ISSN: 0028-4793
    E-ISSN: 1533-4406
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  • 5
    Language: English
    In: The Journal of biological chemistry, 14 September 2018, Vol.293(37), pp.14192-14199
    Description: Systemic amyloidosis is a usually fatal disease caused by extracellular accumulation of abnormal protein fibers, amyloid fibrils, derived by misfolding and aggregation of soluble globular plasma protein precursors. Both WT and genetic variants of the normal plasma protein transthyretin (TTR) form amyloid, but neither the misfolding leading to fibrillogenesis nor the anatomical localization of TTR amyloid deposition are understood. We have previously shown that, under physiological conditions, trypsin cleaves human TTR in a mechano-enzymatic mechanism that generates abundant amyloid fibrils In sharp contrast, the widely used model of denaturation and aggregation of TTR by prolonged exposure to pH 4.0 yields almost no clearly defined amyloid fibrils. However, the exclusive duodenal location of trypsin means that this enzyme cannot contribute to systemic extracellular TTR amyloid deposition Here, we therefore conducted a bioinformatics search for systemically active tryptic proteases with appropriate tissue distribution, which unexpectedly identified plasmin as the leading candidate. We confirmed that plasmin, just as trypsin, selectively cleaves human TTR between residues 48 and 49 under physiological conditions Truncated and full-length protomers are then released from the native homotetramer and rapidly aggregate into abundant fibrils indistinguishable from TTR amyloid. Our findings suggest that physiological fibrinolysis is likely to play a critical role in TTR amyloid formation Identification of this surprising intersection between two hitherto unrelated pathways opens new avenues for elucidating the mechanisms of TTR amyloidosis, for seeking susceptibility risk factors, and for therapeutic innovation.
    Keywords: Amyloid ; Amyloid Fibrillogenesis ; Amyloidogenesis ; Fibril ; Mechano-Enzymatic Mechanism ; Protease ; Protein Aggregation ; Systemic Amyloidosis ; Tissue Plasminogen Activator (Tpa) ; Transthyretin ; Amyloidosis -- Metabolism ; Plasminogen -- Metabolism ; Prealbumin -- Metabolism
    ISSN: 00219258
    E-ISSN: 1083-351X
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  • 6
    In: The New England Journal of Medicine, 2013, Vol.369(9), pp.819-829
    Description: Background Transthyretin amyloidosis is caused by the deposition of hepatocyte-derived transthyretin amyloid in peripheral nerves and the heart. A therapeutic approach mediated by RNA interference (RNAi) could reduce the production of transthyretin. Methods We identified a potent antitransthyretin small interfering RNA, which was encapsulated in two distinct first- and second-generation formulations of lipid nanoparticles, generating ALN-TTR01 and ALN-TTR02, respectively. Each formulation was studied in a single-dose, placebo-controlled phase 1 trial to assess safety and effect on transthyretin levels. We first evaluated ALN-TTR01 (at doses of 0.01 to 1.0 mg per kilogram of body weight) in 32 patients with transthyretin amyloidosis and then evaluated ALN-TTR02 (at doses of 0.01 to 0.5 mg per kilogram) in 17 healthy volunteers. Results Rapid, dose-dependent, and durable lowering of transthyretin levels was observed in the two trials. At a dose of 1.0 mg per kilogram, ALN-TTR01 suppressed transthyretin, with a mean reduction at day 7 of 38%, as compared with placebo (P=0.01); levels of mutant and nonmutant forms of transthyretin were lowered to a similar extent. For ALN-TTR02, the mean reductions in transthyretin levels at doses of 0.15 to 0.3 mg per kilogram ranged from 82.3 to 86.8%, with reductions of 56.6 to 67.1% at 28 days (P〈0.001 for all comparisons). These reductions were shown to be RNAi-mediated. Mild-to-moderate infusion-related reactions occurred in 20.8% and 7.7% of participants receiving ALN-TTR01 and ALN-TTR02, respectively. Conclusions ALN-TTR01 and ALN-TTR02 suppressed the production of both mutant and nonmutant forms of transthyretin, establishing proof of concept for RNAi therapy targeting messenger RNA transcribed from a disease-causing gene. (Funded by Alnylam Pharmaceuticals; ClinicalTrials.gov numbers, NCT01148953 and NCT01559077 .) Transthyretin amyloidosis is largely caused by synthesis of mutant transthyretin in the liver and deposition of transthyretin in other organs. A therapeutic approach mediated by RNA interference resulted in reduced transthyretin levels in affected patients and in controls. Transthyretin amyloidosis is a life-threatening disorder caused by the deposition of hepatocyte-derived transthyretin amyloid in various tissues and organs.1,2 Circulating transthyretin is derived from the liver3 and can form amyloid deposits in peripheral nerves and in the gastrointestinal tract, heart, and kidneys. Transthyretin is also synthesized by the retina and choroid plexus,4,5 which can lead to vitreal and leptomeningeal deposits. More than 100 genetic variants of the gene encoding transthyretin (TTR) are associated with autosomal dominant forms of the disease, known as familial amyloidotic polyneuropathy6–8 and familial amyloidotic cardiomyopathy.9–11 The most common mutation associated . . .
    Keywords: Medicine;
    ISSN: 0028-4793
    E-ISSN: 1533-4406
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  • 7
    Language: English
    In: American Heart Journal, July 2012, Vol.164(1), pp.72-79
    Description: About 4% of African Americans possess the isoleucine 122 (V122I) variant of transthyretin, associated with cardiac amyloidosis beyond ages of 55 to 60 years. Transthyretin amyloidosis associated with variant V122I (ATTR V122I) is likely to be an important cause of heart failure in Afro-Caribbean populations, but the high prevalence of left ventricular hypertrophy (LVH) and lack of awareness of this genetic disorder pose diagnostic hurdles. We report the electrocardiographic (ECG) features of ATTR V122I in the largest clinical series to date. Patients with ATTR V122I were identified in collaboration with the UK National Amyloidosis Centre. The ECG at presentation was assessed for cardiac rhythm, axis, and voltage complex size. We include 64 patients with ATTR V122I, with a median age of 74 years (range, 57-88 years). Normal or increased ECG voltage was present in 44.3% of patients, and overall 25% met the criteria for LVH. A significant negative correlation between voltage complex size and duration of illness was seen ( 〈 .05). First-degree heart block was evident in 56% of patients in sinus rhythm. During follow-up (n = 17; median, 28 months), 50% of patients with initial first-degree heart block required pacing. Electrocardiographic voltages meet the criteria for LVH in one quarter of patients with ATTR V122I cardiac amyloidosis. The widely held belief that cardiac amyloidosis is associated with low-voltage complexes is likely to contribute to underdiagnosis of ATTR V122I. First-degree heart block is common at diagnosis and identifies patients at high risk for subsequent pacing requirement.
    Keywords: Medicine
    ISSN: 0002-8703
    E-ISSN: 1097-6744
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  • 8
    Language: English
    In: The New England journal of medicine, 30 April 2015, Vol.372(18), pp.1769
    Description: To the Editor: In their long-term analysis of black American carriers of the V122I allele in the transthyretin gene (TTR), Quarta et al. (Jan. 1 issue)1 confirm reported carrier frequencies2 but find a low prevalence of echocardiographic features of cardiomyopathy and no significant effect on mortality...
    Keywords: African Americans -- Genetics ; Amyloidosis -- Genetics ; Cardiomyopathy, Restrictive -- Genetics ; Heart Failure -- Genetics ; Prealbumin -- Genetics
    ISSN: 00284793
    E-ISSN: 1533-4406
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  • 9
    Language: English
    In: Journal of the American College of Cardiology, 26 June 2018, Vol.71(25), pp.2919-2931
    Description: Prognosis in light-chain (AL) and transthyretin (ATTR) amyloidosis is influenced by cardiac involvement. ATTR amyloidosis has better prognosis than AL amyloidosis despite more amyloid infiltration, suggesting additional mechanisms of damage in AL amyloidosis. The aim of the study was to assess the presence and prognostic significance of myocardial edema in patients with amyloidosis. The study recruited 286 patients: 100 with systemic AL amyloidosis, 163 with cardiac ATTR amyloidosis, 12 with suspected cardiac ATTR amyloidosis (grade 1 on Tc-3,3-diphosphono-1,2-propanodicarboxylic acid), 11 asymptomatic individuals with amyloidogenic TTR gene mutations, and 30 healthy volunteers. All subjects underwent cardiovascular magnetic resonance with T1 and T2 mapping and 16 underwent endomyocardial biopsy. Myocardial T2 was increased in amyloidosis with the degree of elevation being highest in untreated AL patients (untreated AL amyloidosis 56.6 ± 5.1 ms; treated AL amyloidosis 53.6 ± 3.9 ms; ATTR amyloidosis 54.2 ± 4.1 ms; each p 〈 0.01 compared with control subjects: 48.9 ± 2.0 ms). Left ventricular (LV) mass and extracellular volume fraction were higher in ATTR amyloidosis compared with AL amyloidosis while LV ejection fraction was lower (p 〈 0.001). Histological evidence of edema was present in 87.5% of biopsy samples ranging from 5% to 40% myocardial involvement. Using Cox regression models, myocardial T2 predicted death in AL amyloidosis (hazard ratio: 1.48; 95% confidence interval: 1.20 to 1.82) and remained significant after adjusting for extracellular volume fraction and N-terminal pro–B-type natriuretic peptide (hazard ratio: 1.32; 95% confidence interval: 1.05 to 1.67). Myocardial edema is present in cardiac amyloidosis by histology and cardiovascular magnetic resonance T2 mapping. T2 is higher in untreated AL amyloidosis compared with treated AL and ATTR amyloidosis, and is a predictor of prognosis in AL amyloidosis. This suggests mechanisms additional to amyloid infiltration contributing to mortality in amyloidosis.
    Keywords: Amyloidosis ; Cmr ; T2 Mapping ; Medicine
    ISSN: 0735-1097
    E-ISSN: 1558-3597
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  • 10
    In: Circulation, 2016, Vol.133(24), pp.2404-2412
    Description: BACKGROUND—: Cardiac transthyretin (ATTR) amyloidosis is a progressive and fatal cardiomyopathy for which several promising therapies are in development. The diagnosis is frequently delayed or missed because of the limited specificity of echocardiography and the traditional requirement for histological confirmation. It has long been recognized that technetium-labeled bone scintigraphy tracers can localize to myocardial amyloid deposits, and use of this imaging modality for the diagnosis of cardiac ATTR amyloidosis has lately been revisited. We conducted a multicenter study to ascertain the diagnostic value of bone scintigraphy in this disease. METHODS AND RESULTS—: Results of bone scintigraphy and biochemical investigations were analyzed from 1217 patients with suspected cardiac amyloidosis referred for evaluation in specialist centers. Of 857 patients with histologically proven amyloid (374 with endomyocardial biopsies) and 360 patients subsequently confirmed to have nonamyloid cardiomyopathies, myocardial radiotracer uptake on bone scintigraphy was 〉99% sensitive and 86% specific for cardiac ATTR amyloid, with false positives almost exclusively from uptake in patients with cardiac AL amyloidosis. Importantly, the combined findings of grade 2 or 3 myocardial radiotracer uptake on bone scintigraphy and the absence of a monoclonal protein in serum or urine had a specificity and positive predictive value for cardiac ATTR amyloidosis of 100% (positive predictive value confidence interval, 98.0–100). CONCLUSIONS—: Bone scintigraphy enables the diagnosis of cardiac ATTR amyloidosis to be made reliably without the need for histology in patients who do not have a monoclonal gammopathy. We propose noninvasive diagnostic criteria for cardiac ATTR amyloidosis that are applicable to the majority of patients with this disease.
    Keywords: Medicine ; Anatomy & Physiology;
    ISSN: 0009-7322
    E-ISSN: 15244539
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