Synthesis Of Transthyretin Research Articles

8290 Hypervitaminosis A Induced Severe Hypercalcemia In A Patient With Cirrhosis

Abstract Disclosure: N. Vennelaganti: None. S. Vennelaganti: None. R.L. Fitzgerald: None. K.C. McCowen: None. Introduction The liver stores vitamin A in hepatic stellate cells and regulates its absorption through bile production and distribution via retinol-binding protein 4 and transthyretin synthesis. Cirrhosis compromises these functions, resulting in vitamin A deficiency, which is inversely linked to the severity of nonalcoholic steatohepatitis. Addressing this deficiency in chronic liver diseases, particularly cirrhosis, is challenging due to the risk of vitamin A toxicity. This case describes a cirrhotic patient who developed hypervitaminosis A, leading to severe hypercalcemia. Clinical Case A 54-year-old male with alcoholic cirrhosis was diagnosed with hypovitaminosis A. He was prescribed 10,000 IU of vitamin A due to a low serum retinol level of less than 0.06 mg/L (reference range: 0.3-1.2 mg/L ). Two months later, he presented to the hospital with an erythematous patchy, scaling facial rash. His serum calcium corrected for albumin was high at 15.6 mg/dL. The rash and hypercalcemia, alongside vitamin A supplementation, raised suspicion of vitamin A toxicity. The patient, however, exhibited no hypercalcemia symptoms. He also had an acute kidney injury. His lab results revealed a PTH level of 10 pg/mL (normal range 15-65 pg/ml) and a normal myeloma screen, as well as normal vitamin D and TSH levels. An elevated PTHrP level of 5.2 pmol/l (normal range 0-2.3) was noted, which was attributed to the kidney injury(Cr 2.55 mg/l, eGFR 23 ml/min). Malignancy was excluded after a pan scan. Hypervitaminosis A is a clinical diagnosis, as serum vitamin A levels correlate poorly with toxicity. His serum retinol was normal at 0.83 mg/l, but his retinyl palmitate was high at 0.38 mg/L(reference range 0-0.10 mg/l), which supported our diagnosis. He received continuous IV 0.9% saline and subcutaneous calcitonin at 4 units/kg twice, and had a reduction in corrected calcium to 11 mg/dL over a week. The vitamin A-induced contact dermatitis improved with topical steroids. He was discharged; two months later, he remained asymptomatic with a corrected calcium of 11.1 mg/dL. He was not interested in further management as he was asymptomatic and serum calcium levels were improving. Labs were, however, notable for worsening renal function of unclear etiology. We will be trending his labs for improvement in serum calcium as the Vitamin A clears from his system. Clinical Lesson Vitamin A supplementation in cirrhotic patients is necessary in those with deficiency but carries a risk of toxicity. There are no definitive hepatology guidelines on the replacement of Vitamin A in patients with cirrhosis. This case emphasizes the importance of awareness of hypervitaminosis A-induced hypercalcemia in this population. Clinicians must carefully monitor and manage Vitamin A levels to avoid toxicity. Further research is essential for the management of this condition in cirrhotic patients. Presentation: 6/2/2024

Evolution of Disease-modifying Therapy for Transthyretin Cardiac Amyloidosis.

Transthyretin cardiac amyloidosis (ATTR-CA) represents an inexorably progressive and fatal cardiomyopathy. Increased understanding of the underlying pathogenesis responsible for the misfolding of transthyretin and the subsequent accumulation of amyloid fibrils within the myocardium has led to the development of several disease-modifying therapies that act on different stages of the disease pathway. Tafamidis is the first, and to date remains the only, therapy approved for the treatment of ATTR-CA, which, alongside acoramidis, stabilizes the transthyretin tetramer, preventing disaggregation, misfolding and formation of amyloid fibrils. Gene-silencing agents, such as patisiran, vutrisian and eplontersen, and novel gene-editing therapies, such as NTLA-2001, act to reduce the hepatic synthesis of transthyretin. Anti-amyloid therapies represent another strategy in the treatment of ATTR-CA and are designed to bind amyloid fibril epitopes and stimulate macrophage-mediated removal of amyloid fibrils from the myocardium. Many of these treatments are at an early investigational stage but represent an important area of unmet clinical need and could potentially reverse disease and restore cardiac functions even in patients with advanced disease.

Silencing of ocular transthyretin, a gene responsible for hereditary transthyretin amyloidosis, by intravitreal injection of an siRNA conjugate into rabbit eyes

The first small interfering RNA (siRNA) therapeutic received approval for hereditary transthyretin (ATTRv) amyloidosis, and the patients' lifespan extension by specific inhibition of hepatic synthesis of transthyretin (TTR) is expected. However, ocular amyloidosis in these patients has been a crucial issue. This study aims to evaluate the efficacy and safety of intravitreal TTR siRNA conjugate injection into rabbit eyes. Rabbit (r) TTR siRNA is a screened TTR siRNA conjugate from 53 candidates. The intraocular pressure (IOP) immediately after injection was high despite the 65.9 % decrease of aqueous humor TTR protein levels in the rTTR siRNA group compared with those in the Control siRNA group 2 weeks after the 50 μL siRNA injection. The IOP spike was milder after the 30 μL siRNA injection, and aqueous humor TTR levels decreased by ∼50 % in the rTTR siRNA group, which is consistent with the mRNA levels in the retina. The parameters of dark-adapted, light-adapted, and light-adapted 30 Hz electroretinogram and the thickness of each retinal layer in histological analysis demonstrated no significant differences between the groups. In conclusion, we developed TTR siRNA conjugates for rabbit eyes, and the results indicate that intravitreal TTR siRNA conjugate injection could be a therapeutic option for ocular amyloidosis caused by ATTRv amyloidosis.

Transthyretin knockdown recapitulates the insulin-sensitizing effects of exercise and promotes skeletal muscle adaptation to exercise endurance.

Liver transthyretin (TTR) synthesis and release are exacerbated in insulin-resistant states but are decreased by exercise training, in relation to the insulin-sensitizing effects of exercise. We hypothesized that TTR knockdown (TTR-KD) may mimic this exercise-induced metabolic improvement and skeletal muscle remodeling. Adeno-associated virus-mediated TTR-KD and control mice were trained for 8 weeks on treadmills. Their metabolism status and exercise capacity were investigated and then compared with sedentary controls. After treadmill training, the mice showed improved glucose and insulin tolerance, hepatic steatosis, and exercise endurance. Sedentary TTR-KD mice displayed metabolic improvements comparable to the improvements in trained mice. Both exercise training and TTR-KD promoted the oxidative myofiber compositions of MyHC I and MyHC IIa in the quadriceps and gastrocnemius skeletal muscles. Furthermore, training and TTR-KD had an additive effect on running performance, accompanied by substantial increases in oxidative myofiber composition, Ca2+-dependent Ca2+/calmodulin-dependent protein kinase II (CaMKII) activity, and the downstream expression of PGC1α as well as the unfolded protein response (UPR) segment of PERK-p-eIF2a pathway activity. Consistent with these findings, electrical pulse stimulation of an in vitro model of chronic exercise (with differentiated C2C12 myoblasts) showed that exogenous TTR protein was internalized and localized in the endoplasmic reticulum, where it disrupted Ca2+ dynamics; this led to decreases in intracellular Ca2+ concentration and downstream pathway activity. TTR-KD may function as an exercise/Ca2+-dependent CaMKII-PGC1α-UPR regulator that upregulates the oxidative myofiber composition of fast-type muscles; it appears to mimic the effect of exercise training on insulin sensitivity-related metabolic improvement and endurance capacity.

Effect of patisiran on stroke volume in hereditary transthyretin-mediated amyloidosis: insights from pressure-volume analysis of the APOLLO study.

Transthyretin-mediated (ATTR) amyloidosis is caused by deposition of transthyretin protein fibrils in the heart, nerves, and other organs. Patisiran, an RNA interference therapeutic that inhibits hepatic synthesis of transthyretin, was approved for the treatment of hereditary ATTR amyloidosis with polyneuropathy based on the phase 3 APOLLO study. We use left ventricular (LV) stroke volume (SV) to quantify LV function overtime and non-invasive pressure-volume techniques to delineate the effects of patisiran on LV mechanics in the pre-specified cardiac subpopulation of the APOLLO study. Left ventricular SV was assessed by transthoracic echocardiography at baseline, and after 9 and 18 months of therapy. To determine the mechanisms underlying changes in LV SV, non-invasive pressure-volume parameters, including the end-systolic and end-diastolic pressure-volume relationship, were derived using single beat techniques. At baseline, the mean SV was 51 ± 14ml. At 9months, the least-squares mean change in SV was -0.3 ± 1.2ml for patisiran and -5.4 ± 1.9ml for placebo (p= 0.021). At 18 months, the least-squares mean change in SV was -1.7 ± 1.3ml for patisiran and - 8.1 ± 2.3ml for placebo (p= 0.016). Decline in LV SV was driven by diminished LV capacitance in placebo relative to patisiran. Patisiran may delay progression of LV chamber dysfunction starting at 9months of therapy. These data elucidate the mechanisms by which transthyretin-reducing therapies modulate progression of cardiac disease and need to be confirmed in ongoing phase 3 trials.

Nicotine binds to the transthyretin-thyroxine complex and reduces its uptake by placental trophoblasts

BackgroundA supply of maternal thyroid hormone (thyroxine, T4) is essential for normal human fetal development. Human placental trophoblasts synthesize, secrete and take up the T4 binding protein transthyretin, providing a route for maternal T4 to enter the placenta. Transthyretin is also involved in T4 transport in other tissues such as the brain choroid plexus. Nicotine alters transthyretin synthesis and function in rat choroid plexus. If nicotine influences trophoblast turnover of transthyretin, then it may directly affect placental transfer of T4 to the developing fetus and contribute to the negative impacts of smoking on fetal growth, development and placental function. MethodsThe effect of nicotine on trophoblast uptake of Alexa-labelled transthyretin was measured using live cell imaging. The effect of nicotine on protein expression was measured by western blotting. Interactions between transthyretin, T4 and nicotine were investigated using chemical cross-linking techniques and molecular dynamic simulations. ResultsNicotine blocks uptake of transthyretin-T4 by human placental trophoblast cells. Nicotine reduces the expression of the trophoblast scavenger receptor class B type 1 (SR-B1) that plays a role in transthyretin-T4 uptake. Molecular dynamic modelling suggests that when T4 is bound to transthyretin, nicotine binding increases tetramer stability, reducing the ability of the transthyretin-T4 complex to enter trophoblast cells. ConclusionOur data suggest that nicotine exposure during pregnancy reduces transplacental transport of transthyretin and T4 to the placenta and developing fetus. This may contribute to the negative effects of smoking on fetal growth, development and pregnancy viability.

Cerebellar and Cerebral Amyloid Visualized by [18F]flutemetamol PET in Long-Term Hereditary V30M (p.V50M) Transthyretin Amyloidosis Survivors.

IntroductionHereditary transthyretin (ATTRv) amyloidosis caused by the V30M (p. V50M) mutation is a fatal, neuropathic systemic amyloidosis. Liver transplantation has prolonged the survival of patients and central nervous system (CNS) complications, attributed to amyloid angiopathy caused by CNS synthesis of variant transthyretin, have emerged. The study aimed to ascertain amyloid deposition within the brain in long-term ATTRv amyloidosis survivors with neurological symptoms from the CNS.MethodsA total of 20 patients with ATTR V30M having symptoms from the CNS and a median disease duration of 16 years (8–25 years) were included in this study. The cognitive and peripheral nervous functions were determined for 18 patients cross-sectionally at the time of the investigation. Amyloid brain deposits were examined by [18F]flutemetamol PET/CT. Five patients with Alzheimer's disease (AD) served as positive controls.Result60% of the patients with ATTRv had a pathological Z-score in the cerebellum, compared to only 20% in the patients with AD. 75% of the patients with transient focal neurological episodes (TFNEs) displayed a pathological uptake only in the cerebellum. Increased cerebellar uptake was related to an early age of onset of the ATTRv disease. 55% of the patients with ATTRv had a pathological Z-score in the global cerebral region compared to 100% of the patients with AD.ConclusionAmyloid deposition within the brain after long-standing ATTRv amyloidosis is common, especially in the cerebellum. A cerebellar amyloid uptake profile seems to be related to TFNE symptoms.

Targeted Therapeutics for Transthyretin Amyloid Cardiomyopathy.

Deposition of wild-type or mutant transthyretin (TTR) amyloid fibrils in the myocardium causes TTR amyloid cardiomyopathy (ATTR-CM). Targeted therapeutics for ATTR-CM include TTR stabilizers (tafamidis and diflunisal) and oligonucleotide drugs (revusiran, patisiran, and inotersen). TTR stabilizers prevent dissociation of transthyretin tetramers. Transthyretin monomers can misfold and form amyloid fibrils. TTR stabilizers thereby limit amyloid fibrils development and deposition. Oligonucleotide drugs inhibit hepatic synthesis of transthyretin, which decreases transthyretin protein levels and thus the amyloid fibril substrate. To study the safety and efficacy of targeted therapeutics in patients with ATTR-CM, we performed a pooled analysis. A random-effects model with the Mantel-Haenszel method was used to pool the data. A literature search was performed using PubMed, Cochrane CENTRAL, and Embase databases using the search terms "cardiac amyloidosis" AND "tafamidis" OR "patisiran" OR "inotersen" OR "revusiran" OR "diflunisal." We identified 6 studies that compared targeted therapeutics with placebo. One study was stopped prematurely because of increased mortality in the targeted therapeutics arm. Pooled analysis included 1238 patients, of which 738 patients received targeted therapeutics and 500 patients received placebo. When compared with placebo, targeted therapeutics significantly reduced all-cause mortality [OR 0.39, 95% confidence interval (CI): 0.16-0.97, P = 0.04]. Only 2 studies reported the effect on cardiovascular-related hospitalizations. There was a trend toward an improvement in global longitudinal strain (mean difference -0.69, 95% CI: -1.44 to 0.05, P = 0.07). When compared with placebo, there was no increase in serious adverse events with targeted therapeutics (OR 1.06, 95% CI: 0.78-1.44, P = 0.72). Evidence from the pooled analysis revealed targeted therapeutics improve survival and are well-tolerated. These findings suggest a potential role for targeted therapeutics in the treatment of patients with ATTR-CM.

Targeted Therapeutics for Transthyretin amyloid cardiomyopathy: Time to Move Forward

Introduction Deposition of wild type or mutant transthyretin (TTR) amyloid fibrils causes TTR cardiac amyloidosis (ATTR-CA). Targeted therapeutics (TT) for ATTR-CA include TTR stabilizers (tafamidis, dilfunisal) and oligonucleotide drugs (Revusiran, Patisiran and Inotersen).TTR stabilizers prevent dissociation of amyloid tetramers and thereby limit the deposition of amyloid fibrils. Oligonucleotide drugs inhibit hepatic synthesis of transthyretin. Recent studies have demonstrated improved outcomes with TT in patients with ATTR-CA. Hypothesis We performed a pooled analysis to study the safety and efficacy of TT in patients with ATTR-CA. Methods We searched PubMed for all studies comparing the safety and efficacy of targeted therapeutics (TT) with placebo in patients with ATTR-CA. Primary outcomes were 1) all-cause mortality, 2) cardiac hospitalizations, 3) serious adverse events and 4) change in global longitudinal strain. Random effects model with Mantel-Haenszel method was used to analyze the data. Results We identified six studies which reported at least one of the outcomes comparing TT and placebo. One study was stopped prematurely due to increased mortality in the TT arm. Pooled analysis included 1164 patients, of which 691 patients received TT and 473 patients received placebo. When compared to placebo, TT significantly reduced all-cause mortality [OR 0.39 (95% CI: 0.16 - 0.97, P =0.04)]. Pooled analysis after exclusion of aforementioned prematurely terminated study also showed decrease in all-cause mortality with TT[OR 0.27 (95% CI: 0.10 - 0.71, P =0.008)]. There was no difference in serious adverse events with TT [OR 1.06 (95% CI: 0.78 - 1.44, P =0.72)]. A trend towards improvement in global longitudinal strain with TT (mean difference -0.69 (95% CI: -1.44 - 0.05, P =0.07) was noted. Only two studies reported the effect on cardiac hospitalizations. Conclusions In patients with ATTR-CA, TT reduced all-cause mortality and were well-tolerated as compared to placebo.

Accurate, strong, and stable reporting of choroid plexus epithelial cells in transgenic mice using a human transthyretin BAC

BackgroundChoroid plexus epithelial cells express high levels of transthyretin, produce cerebrospinal fluid and many of its proteins, and make up the blood-cerebrospinal fluid barrier. Choroid plexus epithelial cells are vital to brain health and may be involved in neurological diseases. Transgenic mice containing fluorescent and luminescent reporters of these cells would facilitate their study in health and disease, but prior transgenic reporters lost expression over the early postnatal period.MethodsHuman bacterial artificial chromosomes in which the transthyretin coding sequence was replaced with DNA for tdTomato or luciferase 2 were used in pronuclear injections to produce transgenic mice. These mice were characterized by visualizing red fluorescence, immunostaining, real-time reverse transcription polymerase chain reaction, and luciferase enzyme assay.ResultsReporters were faithfully expressed in cells that express transthyretin constitutively, including choroid plexus epithelial cells, retinal pigment epithelium, pancreatic islets, and liver. Expression of tdTomato in choroid plexus began at the appropriate embryonic age, being detectable by E11.5. Relative levels of tdTomato transcript in the liver and choroid plexus paralleled relative levels of transcripts for transthyretin. Expression remained robust over the first postnatal year, although choroid plexus transcripts of tdTomato declined slightly with age whereas transthyretin remained constant. TdTomato expression patterns were consistent across three founder lines, displayed no sex differences, and were stable across several generations. Two of the tdTomato lines were bred to homozygosity, and homozygous mice are healthy and fertile. The usefulness of tdTomato reporters in visualizing and analyzing live Transwell cultures was demonstrated. Luciferase activity was very high in homogenates of choroid plexus and continued to be expressed through adulthood. Luciferase also was detectable in eye and pancreas.ConclusionsTransgenic mice bearing fluorescent and luminescent reporters of transthyretin should prove useful for tracking transplanted choroid plexus epithelial cells, for purifying the cells, and for reporting their derivation from stem cells. They also should prove useful for studying transthyretin synthesis by other cell types, as transthyretin has been implicated in many functions and conditions, including clearance of β-amyloid peptides associated with Alzheimer’s disease, heat shock in neurons, processing of neuropeptides, nerve regeneration, astrocyte metabolism, and transthyretin amyloidosis.

Non-coding RNAs in cardiovascular diseases: diagnostic and therapeutic perspectives.

Recent research has demonstrated that the non-coding genome plays a key role in genetic programming and gene regulation during development as well as in health and cardiovascular disease. About 99% of the human genome do not encode proteins, but are transcriptionally active representing a broad spectrum of non-coding RNAs (ncRNAs) with important regulatory and structural functions. Non-coding RNAs have been identified as critical novel regulators of cardiovascular risk factors and cell functions and are thus important candidates to improve diagnostics and prognosis assessment. Beyond this, ncRNAs are rapidly emgerging as fundamentally novel therapeutics. On a first level, ncRNAs provide novel therapeutic targets some of which are entering assessment in clinical trials. On a second level, new therapeutic tools were developed from endogenous ncRNAs serving as blueprints. Particularly advanced is the development of RNA interference (RNAi) drugs which use recently discovered pathways of endogenous short interfering RNAs and are becoming versatile tools for efficient silencing of protein expression. Pioneering clinical studies include RNAi drugs targeting liver synthesis of PCSK9 resulting in highly significant lowering of LDL cholesterol or targeting liver transthyretin (TTR) synthesis for treatment of cardiac TTR amyloidosis. Further novel drugs mimicking actions of endogenous ncRNAs may arise from exploitation of molecular interactions not accessible to conventional pharmacology. We provide an update on recent developments and perspectives for diagnostic and therapeutic use of ncRNAs in cardiovascular diseases, including atherosclerosis/coronary disease, post-myocardial infarction remodelling, and heart failure.

Transport of thyroid hormones via the choroid plexus into the brain: the roles of transthyretin and thyroid hormone transmembrane transporters.

Thyroid hormones are key players in regulating brain development. Thus, transfer of appropriate quantities of thyroid hormones from the blood into the brain at specific stages of development is critical. The choroid plexus forms the blood-cerebrospinal fluid barrier. In reptiles, birds and mammals, the main protein synthesized and secreted by the choroid plexus is a thyroid hormone distributor protein: transthyretin. This transthyretin is secreted into the cerebrospinal fluid and moves thyroid hormones from the blood into the cerebrospinal fluid. Maximal transthyretin synthesis in the choroid plexus occurs just prior to the period of rapid brain growth, suggesting that choroid plexus-derived transthyretin moves thyroid hormones from blood into cerebrospinal fluid just prior to when thyroid hormones are required for rapid brain growth. The structure of transthyretin has been highly conserved, implying strong selection pressure and an important function. In mammals, transthyretin binds T4 (precursor form of thyroid hormone) with higher affinity than T3 (active form of thyroid hormone). In all other vertebrates, transthyretin binds T3 with higher affinity than T4. As mammals are the exception, we should not base our thinking about the role of transthyretin in the choroid plexus solely on mammalian data. Thyroid hormone transmembrane transporters are involved in moving thyroid hormones into and out of cells and have been identified in many tissues, including the choroid plexus. Thyroid hormones enter the choroid plexus via thyroid hormone transmembrane transporters and leave the choroid plexus to enter the cerebrospinal fluid via either thyroid hormone transmembrane transporters or via choroid plexus-derived transthyretin secreted into the cerebrospinal fluid. The quantitative contribution of each route during development remains to be elucidated. This is part of a review series on ontogeny and phylogeny of brain barrier mechanisms.

The systemic amyloid precursor transthyretin (TTR) behaves as a neuronal stress protein regulated by HSF1 in SH-SY5Y human neuroblastoma cells and APP23 Alzheimer's disease model mice.

Increased neuronal synthesis of transthyretin (TTR) may favorably impact on Alzheimer's disease (AD) because TTR has been shown to inhibit Aβ aggregation and detoxify cell-damaging conformers. The mechanism whereby hippocampal and cortical neurons from AD patients and APP23 AD model mice produce more TTR is unknown. We now show that TTR expression in SH-SY5Y human neuroblastoma cells, primary hippocampal neurons and the hippocampus of APP23 mice, is significantly enhanced by heat shock factor 1 (HSF1). Chromatin immunoprecipitation (ChIP) assays demonstrated occupation of TTR promoter heat shock elements by HSF1 in APP23 hippocampi, primary murine hippocampal neurons, and SH-SY5Y cells, but not in mouse liver, cultured human hepatoma (HepG2) cells, or AC16 cultured human cardiomyocytes. Treating SH-SY5Y human neuroblastoma cells with heat shock or the HSF1 stimulator celastrol increased TTR transcription in parallel with that of HSP40, HSP70, and HSP90. With both treatments, ChIP showed increased occupancy of heat shock elements in the TTR promoter by HSF1. In vivo celastrol increased the HSF1 ChIP signal in hippocampus but not in liver. Transfection of a human HSF1 construct into SH-SY5Y cells increased TTR transcription and protein production, which could be blocked by shHSF1 antisense. The effect is neuron specific. In cultured HepG2 cells, HSF1 was either suppressive or had no effect on TTR expression confirming the differential effects of HSF1 on TTR transcription in different cell types.

Sustained choroid plexus function in human elderly and Alzheimer’s disease patients

We and other investigators have postulated deterioration of essential choroid plexus (CP) functions in some elderly and especially Alzheimer’s disease patients based on apparent anatomical, histological and pathological changes in CP. We have termed this putative phenomenon CP failure. By focusing on four essential energy-requiring CP functions, specifically ascorbic acid (AA) and folate transport from blood into CSF, transthyretin synthesis and secretion into CSF, and electrolyte/acid–base balance in CSF, we were able to evaluate the hypothesis of CP failure by reviewing definitive human data. In both healthy elderly and Alzheimer’s disease patients, the CP functions normally to transport AA and folates actively from blood into CSF, synthesize and secrete transthyretin into CSF, and maintain CSF acid–base balance and ion concentrations. These human CSF compositional data provide no support for the notion of CP failure in elderly humans and Alzheimer’s disease patients.

Novel Therapy for Transthyretin–related Ocular Amyloidosis: A Pilot Study of Retinal Laser Photocoagulation

The occurrence of ocular complications associated with transthyretin-related familial amyloidotic polyneuropathy increases with time, even after liver transplantation, which leads to a halt in the progression of systemic neurologic complications. This study investigated a new strategy to prevent ocular involvements.Two interventional case reports.Two patients with familial amyloidotic polyneuropathy who had progressive ocular manifestations.We used panretinal laser photocoagulation, which damages the retinal pigment epithelium, the main location for synthesis of amyloidogenic transthyretin in ocular tissues, to treat 1 eye of each patient. After laser photocoagulation, we performed general ophthalmic examinations every 3 months for 3 years.Fundus photography, visual acuity, and intraocular pressure.Panretinal laser photocoagulation clearly prevented progression of amyloid deposition in the vitreous and on the retinal surface in both cases during 3 years of follow-up. No serious complications occurred.Panretinal laser photocoagulation is a safe and well-known procedure that offers a new treatment option to mitigate ocular manifestations in patients with transthyretin-related familial amyloidotic polyneuropathy.

Evolutionary changes to transthyretin

Thyroid hormones (THs) are key regulators of growth, differentiation and metabolism of vertebrates. They are soluble in lipid membranes, and binding to specific proteins in plasma could thereby prevent their loss from the circulation. Albumin, transthyretin and thyroxine-binding globulin (TBG) are the major distributors of THs in the plasma of larger mammals. Of these TH-binding proteins, transthyretin is one of the most interesting. In this minireview series, Prapunpoj and Leelawatwattana review the work carried out to elucidate the 3D structures and functions of transthyretins from several vertebrates. During evolution, the amino acid residues involved in TH binding have not been altered. However, pronounced changes have occurred in the Nand, to a lesser extent, in the C-terminal regions. The question arose as to whether these alterations influence the function of transthyretin and this point is discussed in the review. Transthyretin has versatile functions and these are suggested to depend on its binding affinities mainly to THs and to retinol-binding protein (RBP). Transthyretin works in a ‘network system’ with albumin and TBG in distributing THs from the thyroid gland to target tissues. In this network, a deficiency in one component can be compensated for by the other compounds, which has meant that any specific function of transthyretin could not be revealed directly by means of gene knockout. Analysis of the specific sites of synthesis of transthyretin and the onset of transthyretin gene expression in tissues during vertebrate evolution is one effective way of elucidating the putative functions of transthyretin. This, and hypotheses regarding tissue-specific synthesis of transthyretin in each vertebrate class, are summarized and discussed by Richardson. The evolutionary expression of a gene in specific tissues can indicate the importance and functions of the gene product. The developmentally regulated geneexpression profile of the transthyretin and other TH carriers in vertebrates, reviewed by Yamauchi and Ishihara, indicates how the TH distributor network in the extracellular space developed during evolution and how this bloodstream network evolved with functional redundancy. A correlation of the appearance of the network with the increased requirement of THs for TH-dependent tissue remodeling and ⁄or increased metabolism in TH-target tissues with the acquisition of homeothermy, has been proposed. The primary structures of transthyretins from fish and amphibians are similar to those from humans, suggesting that there has been little change since the divergence of the vertebrates. Multiple genomes have been identified and characterized via nucleotide sequencing coupled with sophisticated pairwise sequence-alignment search tools. These have also enabled a search for a transthyretin homologue, transthyretin-like protein (TLP), among nonvertebrate organisms, as summarized by Hennebry. The distribution of the TLP genes in nature, and the structure, function and evolution of the TLP proteins from various organisms, are discussed. This minireview series illustrates what we know about the evolution of transthyretin. The knowledge obtained not only provides insight into the importance and functional aspects of transthyretin, but also points the way to future research directions relating to this versatile molecule.

Evolutionary changes to transthyretin: evolution of transthyretin biosynthesis

Thyroid hormones are involved in growth and development, particularly of the brain. Thus, it is imperative that these hormones get from their site of synthesis to their sites of action throughout the body and the brain. This role is fulfilled by thyroid hormone distributor proteins. Of particular interest is transthyretin, which in mammals is synthesized in the liver, choroid plexus, meninges, retinal and ciliary pigment epithelia, visceral yolk sac, placenta, pancreas and intestines, whereas the other thyroid hormone distributor proteins are synthesized only in the liver. Transthyretin is synthesized by all classes of vertebrates; however, the tissue specificity of transthyretin gene expression varies widely between classes. This review summarizes what is currently known about the evolution of transthyretin synthesis in vertebrates and presents hypotheses regarding tissue-specific synthesis of transthyretin in each vertebrate class.

Positive association between ALDH1A2 and schizophrenia in the Chinese population

Vitamin A (retinol), in the biologically active form of retinoic acid (RA), has been proposed as involved in the pathogenesis of schizophrenia. We hypothesized that genetic basis of genes encoding RA metabolism enzymes, which control the cellular RA level, might be associated with this disease. This cascade genetic association model, using markers in genes of synthesis and degradation enzymes within the retinoid cascade, would better fit the biological character of the retinoid hypothesis than the single gene strategy. In the present study we chose to investigate 7 genes involved in the synthesis, degradation and transportation of RA, ALDH1A1, ALDH1A2, ALDH1A3, CYP26A1, CYP26B1, CYP26C1 and Transthyretin (TTR), for their roles in the development of schizophrenia. We genotyped 18 single nucleotide polymorphisms (SNPs) in the regulatory and coding regions of these 7 genes using LDR technology in the 617 Chinese Han subjects. Case–control analyses were performed to detect association of these 7 genes with schizophrenia. Association analyses using both allelic and genotypic single-locus tests revealed no significant association between the risk for each of investigated gene and schizophrenia. However, analyses of multiple-locus haplotypes indicated that the overall frequency of rs4646642–rs4646580 of ALDH1A2 gene showed significant difference between patients and control subjects ( p = 0.0055). We also employed multifactor dimensionality reduction method to detect multilocus effects. In summary, in this work we show multiple candidate genes involved in retinoid cascade in schizophrenics. In addition, our results suggest a positive association between ALDH1A2 and schizophrenics in the Chinese population and support the retinoid hypothesis of schizophrenia.

Analyses of transthyretin concentration in the cerebrospinal fluid of patients with Guillain-Barré syndrome and other neurological disorders

Background Guillain-Barré syndrome (GBS) is an autoimmune inflammatory polyradiculoneuropathy that causes acute areflexic paralysis with a high risk of respiratory failure. Previously, using two-dimensional gel electrophoresis and mass spectrometry, we found that the transthyretin level was altered in the cerebrospinal fluid (CSF) of GBS patients when compared to that in CSF of control patients. Methods We used enzyme-linked immunosorbent assay (ELISA) to measure the transthyretin levels in the CSF and serum from 22 GBS, 4 Miller-Fisher syndrome (MFS), 9 chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), 22 multiple sclerosis (MS), 10 Alzheimer's disease (AD), and 6 viral meningitis (VM) patients, and 18 controls. Results The results show that CSF transthyretin concentration of the GBS patients is significantly higher than that of the control, MS, AD and VM patients ( p < 0.05), although not significantly different from that of MFS and CIDP patients. Conclusion The increased CSF transthyretin level may be explained by barrier dysfunction or decreased CSF flow in the GBS patients along with increased intrathecal synthesis of transthyretin that might be a protective response to nerve damage.

Accelerating restrictive cardiomyopathy after liver transplantation in a patient with familial amyloidotic polyneuropathy: a case report.

IntroductionHereditary amyloidodis is a rare disease process with a propensity to cause polyneuropathies, autonomic dysfunction, and restrictive cardiomyopathy. It is transmitted in an autosomal dominant manner, with disease onset usually in the 20s-40s. The most common hereditary amyloidogenic protein, transthyretin, is synthesized in the liver and lies on Chromosome 18. Over 80 amyloidogenic transthyretin mutations have been described, the majority of which are neuropathic and hence the common name, Familial Amyloidotic Polyneuropathy. Until 1990, the disease was intractable with a 5–15 year survival after diagnosis. The prognosis changed after the implementation of orthotropic liver transplantation as a treatment strategy which halts the synthesis of amyloidogenic transthyretin. This has now has been performed over 1300 times in 67 centers.Case presentationWe describe the case of a man of Irish ancestry with Familial Amyloidotic Polyneuropathy and no clinical history of cardiac involvement. Shortly after orthotropic liver transplantation, he developed congestive heart failure. He was subsequently diagnosed with an accelerating post-transplant restrictive cardiomyopathy due to amyloid infiltration.ConclusionA liver transplant induced cardiomyopathy in Familial Amyloidotic Polyneuropathy can be observed in patients without any history of cardiac symptoms. All patients with Familial Amyloidotic Polyneuropathy should be followed after transplantation to assess for a deterioration in cardiac function.