The transthyretin-retinol-binding protein complex

Fenretinide in Young Women at Genetic or Familial Risk of Breast Cancer: A Placebo-Controlled Biomarker Trial

Fenretinide, a retinoid with a low-toxicity profile that accumulates in the breast, has been shown to prevent second breast cancer in young women. Fenretinide exhibits apoptotic and antiinvasive properties and it improves insulin sensitivity in overweight premenopausal women with insulin resistance. This study aimed to further characterize its role in cancer prevention by measuring circulating biomarkers related to insulin sensitivity and breast cancer risk.Sixty-two women, ages 20 to 46 years, healthy or who had already undergone breast cancer surgery, with a known BRCA1/2 mutation or a likelihood of mutation ≥20% according to the BRCAPRO model, were randomly assigned to receive fenretinide (200 mg/day) or placebo for 5 years (trial registration: EudraCT No. 2009-010260-41). Fasting blood samples were drawn at baseline, 12 and 36 months, and the following biomarkers were analyzed: retinol, leptin, adiponectin, retinol-binding protein 4 (RBP-4), total cholesterol, high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol, triglycerides, glucose, insulin, insulin-like growth factor (IGF-1), IGF-binding protein 3, sex hormone binding globulin (SHBG), testosterone, and vascular endothelial growth factor (VEGF).After 12 months of treatment, we observed a favorable effect of fenretinide on glucose (decrease; P = 0.005), insulin (decrease; P = 0.03), homeostatic model assessment index (decrease; P = 0.004), HDL cholesterol (increase; P = 0.002), even though these effects were less prominent after 36 months. Retinol and retinol-binding protein 4 markedly decreased (P < 0.0001) throughout the study. None of the other measured biomarkers changed.

PREVENTION RELEVANCE

Fenretinide exhibits beneficial effects on the metabolic profile, supporting its clinical use in breast cancer prevention especially in premenopausal women with a positive family history and pathogenic variants in BRCA1/2 genes. This finding requires further investigations in larger trials to confirm its role in breast cancer prevention.

Joint Hypermobility Syndrome and Membrane Proteins: A Comprehensive Review

Ehlers-Danlos syndromes (EDSs) constitute a heterogeneous group of connective tissue disorders characterized by joint hypermobility, skin hyperextensibility, and tissue fragility. Asymptomatic EDSs, joint hypermobility without associated syndromes, EDSs, and hypermobility spectrum disorders are the commonest phenotypes associated with joint hypermobility. Joint hypermobility syndrome (JHS) is a connective tissue disorder characterized by extreme flexibility of the joints, along with pain and other symptoms. JHS can be a sign of a more serious underlying genetic condition, such as EDS, which affects the cartilage, bone, fat, and blood. The exact cause of JHS could be related to genetic changes in the proteins that add flexibility and strength to the joints, ligaments, and tendons, such as collagen. Membrane proteins are a class of proteins embedded in the cell membrane and play a crucial role in cell signaling, transport, and adhesion. Dysregulated membrane proteins have been implicated in a variety of diseases, including cancer, cardiovascular disease, and neurological disorders; recent studies have suggested that membrane proteins may also play a role in the pathogenesis of JHS. This article presents an exploration of the causative factors contributing to musculoskeletal pain in individuals with hypermobility, based on research findings. It aims to provide an understanding of JHS and its association with membrane proteins, addressing the clinical manifestations, pathogenesis, diagnosis, and management of JHS.

An in vitro model for vitamin A transport across the human blood-brain barrier

Vitamin A, supplied by the diet, is critical for brain health, but little is known about its delivery across the blood-brain barrier (BBB). Brain microvascular endothelial-like cells (BMECs) differentiated from human-derived induced pluripotent stem cells (iPSCs) form a tight barrier that recapitulates many of the properties of the human BBB. We paired iPSC-derived BMECs with recombinant vitamin A serum transport proteins, retinol-binding protein (RBP), and transthyretin (TTR), to create an in vitro model for the study of vitamin A (retinol) delivery across the human BBB. iPSC-derived BMECs display a strong barrier phenotype, express key vitamin A metabolism markers, and can be used for quantitative modeling of retinol accumulation and permeation. Manipulation of retinol, RBP, and TTR concentrations, and the use of mutant RBP and TTR, yielded novel insights into the patterns of retinol accumulation in, and permeation across, the BBB. The results described herein provide a platform for deeper exploration of the regulatory mechanisms of retinol trafficking to the human brain.

Chelation Therapy Associated with Antioxidant Supplementation Can Decrease Oxidative Stress and Inflammation in Multiple Sclerosis: Preliminary Results

An imbalance of oxy-inflammation status has been involved in axonal damage and demyelination in multiple sclerosis (MS). The aim of this study was to investigate the efficacy of an antioxidant treatment (calcium disodium ethylenediaminetetracetic acid-EDTA) chelation therapy associated with a micronutrient complex in MS patients. A total of 20 MS patients and 20 healthy subjects, enrolled as a control group (CTR), were recruited. We measured the plasma ROS production and total antioxidant capacity (TAC) by a direct assessment using Electron Paramagnetic Resonance; activities of the antioxidant system (thiols' redox status and enzymes); and the urinary presence of biomarkers of oxidative stress by immunoenzymatic assays. We also evaluated the levels of inflammation by plasmatic cytokines (TNFα, IL-1β, and IL-6) and assessed the sICAM levels, as well as the nitric oxide (NO) catabolism and transthyretin (TTR) concentration. Comparing CTR and MS, in the latter ROS production, oxidative damage, inflammatory biomarkers, and NO metabolite concentrations results were significantly higher, while TAC was significantly lower. Treatment in MS induced significant (p < 0.05) down-regulating of pro-inflammatory sICAM1, TNF-α, IL6, as well as biomarkers of lipid peroxidation and DNA damage production. The protective effect exhibited may occur by decreasing ROS production and increasing antioxidant capacity, turning into a more reduced thiols' status.

An in vitro model for vitamin A transport across the human blood-brain barrier

Vitamin A, supplied by the diet, is critical for brain health, but little is known about its delivery across the blood-brain barrier (BBB). Brain microvascular endothelial-like cells (BMECs) differentiated from human-derived induced pluripotent stem cells (iPSC) form a tight barrier that recapitulates many of the properties of the human BBB. We paired iPSC-derived BMECs with recombinant vitamin A serum transport proteins, retinol binding protein (RBP) and transthyretin (TTR), to create an in vitro model for the study of vitamin A (retinol) delivery across the human BBB. iPSC-derived BMECs display a strong barrier phenotype, express key vitamin A metabolism markers and can be used for quantitative modeling of retinol accumulation and permeation. Manipulation of retinol, RBP and TTR concentrations, and the use of mutant RBP and TTR, yielded novel insights into the patterns of retinol accumulation in, and permeation across, the BBB. The results described herein provide a platform for deeper exploration of the regulatory mechanisms of retinol trafficking to the human brain.

Tafamidis polyneuropathy amelioration requires modest increases in transthyretin stability even though increases in plasma native TTR and decreases in non-native TTR do not predict response

BACKGROUND

TTR aggregation causes hereditary transthyretin (TTR) polyneuropathy (ATTRv-PN) in individuals with destabilised TTR variants. ATTRv-PN can be treated with ligands that bind TTR and prevent aggregation. One such ligand, tafamidis, is widely approved to treat ATTRv-PN. We explore how TTR stabilisation markers relate to clinical efficacy in 210 ATTRv-PN patients taking tafamidis.

METHODS

TTR concentration in patient plasma was measured before and after tafamidis treatment using assays for native or combined native + non-native TTR. TTR tetramer dissociation kinetics, which are slowed by tafamidis binding, were also measured.

RESULTS

Native TTR levels increased by 56.8% while combined native + non-native TTR levels increased by 3.1% after 24 months of tafamidis treatment, implying that non-native TTR decreased. Accordingly, the fraction of native TTR increased from 0.54 to 0.71 with tafamidis administration. Changes in native and non-native TTR levels were uncorrelated with clinical response to tafamidis. TTR tetramer dissociation generally slowed to an extent consistent with ∼40% of TTR being tafamidis-bound. Male non-responders had a lower extent of binding.

CONCLUSIONS

Native and non-native TTR concentration changes cannot be used as surrogate measures for therapeutic efficacy. Also, successful tafamidis therapy requires only moderate TTR stabilisation. Male patients may benefit from higher tafamidis doses.

Altered peripheral factors affecting the absorption, distribution, metabolism, and excretion of oral medicines in Alzheimer's disease

Alzheimer's disease (AD) has traditionally been considered solely a neurological condition. Therefore, numerous studies have been conducted to identify the existence of pathophysiological changes affecting the brain and the blood-brain barrier in individuals with AD. Such studies have provided invaluable insight into possible changes to the central nervous system exposure of drugs prescribed to individuals with AD. However, there is now increasing recognition that extra-neurological systems may also be affected in AD, such as the small intestine, liver, and kidneys. Examination of these peripheral pathophysiological changes is now a burgeoning area of scientific research, owing to the potential impact of these changes on the absorption, distribution, metabolism, and excretion (ADME) of drugs used for both AD and other concomitant conditions in this population. The purpose of this review is to identify and summarise available literature reporting alterations to key organs influencing the pharmacokinetics of drugs, with any changes to the small intestine, liver, kidney, and circulatory system on the ADME of drugs described. By assessing studies in both rodent models of AD and samples from humans with AD, this review highlights possible dosage adjustment requirements for both AD and non-AD drugs so as to ensure the achievement of optimum pharmacotherapy in individuals with AD.

Retinol binding protein 4 antagonists and protein synthesis inhibitors: Potential for therapeutic development

Retinol-binding protein 4 (RBP4) is a serum protein that transports Vitamin A. RBP4 is correlated with numerous diseases and metabolic syndromes, including insulin resistance in type 2 diabetes, cardiovascular diseases, obesity, and macular degeneration. Recently, RBP4 antagonists and protein synthesis inhibitors are under development to regulate the effect of RBP4. Several RBP4 antagonists, especially BPN-14136, have demonstrated promising safety profiles and potential therapeutic benefits in animal studies. Two RBP4 antagonists, specifically tinlarebant (Belite Bio) and STG-001 (Stargazer) are currently undergoing clinical trials. Some antidiabetic drugs and nutraceuticals have been reported to reduce RBP4 expression, but more clinical data is needed to evaluate their therapeutical benefits. As regulating RBP4 levels or its activities would benefit a wide range of patients, further research is highly recommended to develop clinically useful RBP4 antagonists or protein synthesis inhibitors.

Drug Discovery and Development in Rare Diseases: Taking a Closer Look at the Tafamidis Story

Rare diseases are increasingly recognized as a global public health priority. Governments worldwide currently provide important incentives to stimulate the discovery and development of orphan drugs for the treatment of these conditions, but substantial scientific, clinical, and regulatory challenges remain. Tafamidis is a first-in-class, disease-modifying transthyretin (TTR) kinetic stabilizer that represents a major breakthrough in the treatment of transthyretin amyloidosis (ATTR amyloidosis). ATTR amyloidosis is a rare, progressive, and fatal systemic disorder caused by aggregation of misfolded TTR and extracellular deposition of amyloid fibrils in various tissues and organs, including the heart and nervous systems. In this review, we present the successful development of tafamidis spanning 3 decades, marked by meticulous laboratory research into disease mechanisms and natural history, and innovative clinical study design and implementation. These efforts established the safety and efficacy profile of tafamidis, leading to its regulatory approval, and enabled post-approval initiatives that further support patients with ATTR amyloidosis.

The interaction of zinc with the multi-functional plasma thyroid hormone distributor protein, transthyretin: evolutionary and cross-species comparative aspects

A considerable body of evidence has been accumulated showing the interrelationship between zinc and the plasma thyroid hormone (TH) distributor protein, transthyretin (TTR). TTR is a multi-functional protein, which emerged from 5-hydroxyisourate hydrolase (HIUHase) by neo-functionalization after gene duplication during early chordate evolution. HIUHase is also a zinc-binding protein. Most biochemical and molecular biological findings have been obtained from mammalian studies. However, in the past two decades, it has become clear that fish TTR displays zinc-dependent TH binding. After a brief introduction on plasma zinc, THs and their binding proteins, this review will focus on the role of zinc in TTR functions of various vertebrates. In particular primitive fish TTR has an extremely high zinc content, with an increased number of histidine residues which are involved in TH binding. However, zinc-dependent TH binding may have been gradually lost from TTRs during higher vertebrate evolution. Although human TTR has a low zinc content, zinc plays an essential role in TTR functions other than TH binding: the stability of TTR-holo retinol binding protein 4 (holoRBP4) complex, TTR amyloidogenesis, the sequestration of amyloid β (Aβ) fibrils and cryptic proteolytic activity. The interaction of TTR with metallothioneins may be a critical step in the exertion of some of these functions. Evolutionary and physiological insights on zinc-dependent functions of TTRs are also discussed.

Long term outcomes of infants born by mothers with thyroid dysfunction during pregnancy

According to Barker’s hypothesis, sub-optimal conditions during gestation might affect the predisposition for diseases in adulthood. Alteration in endocrine functions during pregnancy, such us thyroid function or glucose metabolism, are not exempt. It is well known that subclinical hypothyroidism and thyroperoxidase antibodies-positive euthyroidism during early pregnancy are associated with increased risk of gestational diabetes mellitus and both conditions influence pregnancy outcome and newborn development and metabolism at short and long terms. Fetal production of thyroid hormones starts from the 12th week of gestational age. The transplacental passage of maternal thyroxine (T4) is therefore essential for the fetal neurological development, especially during the first half of pregnancy. If this passage is interrupted, such as in premature birth, neonates are more susceptible to develop impaired thyroid function, because of physiological immaturity of their hypothalamic-pituitary-thyroid axis, acute illnesses and stressful events (sepsis, invasive procedures, drugs). The aim of this review is to investigate the short and long term effects of maternal dysthyroidisms on term and preterm newborns, with particular attention to the metabolic and thyroid consequences. Metabolic syndrome, higher body mass index and greater waist circumference, seem to be more prevalent in children of TPO-Ab-positive mothers. Maternal hypothyroidism may be associated with higher risk of gestational diabetes and adverse birth outcomes, such as preeclampsia, preterm delivery, fetal death and low birth weight offspring. In adulthood, preterm (< 37 weeks of gestational age) or low birth weight (<2.500 g) newborns seem to be more susceptible to develop gestational diabetes, preeclampsia, type 2 diabetes mellitus and behavioral alterations. (www.actabiomedica.it)

Retinoic Acid and the Gut Microbiota in Alzheimer's Disease: Fighting Back-to-Back?

BACKGROUND

There is growing evidence that the gut microbiota may play an important role in neurodegenerative diseases such as Alzheimer's disease. However, how these commensals influence disease risk and progression still has to be deciphered.

OBJECTIVE

The objective of this review was to summarize current knowledge on the interplay between gut microbiota and retinoic acid. The latter one represents one of the important micronutrients, which have been correlated to Alzheimer's disease and are used in initial therapeutic intervention studies.

METHODS

A selective overview of the literature is given with the focus on the function of retinoic acid in the healthy and diseased brain, its metabolism in the gut, and the potential influence that the bioactive ligand may have on microbiota, gut physiology and, Alzheimer's disease.

RESULTS

Retinoic acid can influence neuronal functionality by means of plasticity but also by neurogenesis and modulating proteostasis. Impaired retinoid-signaling, therefore, might contribute to the development of diseases in the brain. Despite its rather direct impact, retinoic acid also influences other organ systems such as gut by regulating the residing immune cells but also factors such as permeability or commensal microbiota. These in turn can also interfere with retinoid-metabolism and via the gutbrain- axis furthermore with Alzheimer's disease pathology within the brain.

CONCLUSION

Potentially, it is yet too early to conclude from the few reports on changed microbiota in Alzheimer's disease to a dysfunctional role in retinoid-signaling. However, there are several routes how microbial commensals might affect and might be affected by vitamin A and its derivatives.

A conformation-specific ON-switch for controlling CAR T cells with an orally available drug

Molecular ON-switches in which a chemical compound induces protein-protein interactions can allow cellular function to be controlled with small molecules. ON-switches based on clinically applicable compounds and human proteins would greatly facilitate their therapeutic use. Here, we developed an ON-switch system in which the human retinol binding protein 4 (hRBP4) of the lipocalin family interacts with engineered hRBP4 binders in a small molecule-dependent manner. Two different protein scaffolds were engineered to bind to hRBP4 when loaded with the orally available small molecule A1120. The crystal structure of an assembled ON-switch shows that the engineered binder specifically recognizes the conformational changes induced by A1120 in two loop regions of hRBP4. We demonstrate that this conformation-specific ON-switch is highly dependent on the presence of A1120, as demonstrated by an ∼500-fold increase in affinity upon addition of the small molecule drug. Furthermore, the ON-switch successfully regulated the activity of primary human CAR T cells in vitro. We anticipate that lipocalin-based ON-switches have the potential to be broadly applied for the safe pharmacological control of cellular therapeutics.

Comparative pharmacokinetics and pharmacodynamics of the advanced Retinol-Binding Protein 4 antagonist in dog and cynomolgus monkey

Accumulation of lipofuscin bisretinoids in the retina contributes to pathogenesis of macular degeneration. Retinol-Binding Protein 4 (RBP4) antagonists reduce serum retinol concentrations thus partially reducing retinol delivery to the retina which decreases bisretinoid synthesis. BPN-14136 is a novel RBP4 antagonist with good in vitro potency and selectivity and optimal rodent pharmacokinetic (PK) and pharmacodynamic (PD) characteristics. To select a non-rodent species for regulatory toxicology studies, we conducted PK and PD evaluation of BPN-14136 in dogs and non-human primates (NHP). PK properties were determined following oral and intravenous administration of BPN-14136 in beagle dogs and cynomolgus monkeys. Dynamics of plasma RBP4 reduction in response to compound administration was used as a PD marker. BPN-14136 exhibited favorable PK profile in both species. Dose-normalized exposure was significantly higher in NHP than in dog. Baseline concentrations of RBP4 were considerably lower in dog than in NHP, reflecting the atypical reliance of canids on non-RBP4 mechanisms of retinoid trafficking. Oral administration of BPN-14136 to NHP induced a strong 99% serum RBP4 reduction. Dynamics of RBP4 lowering in both species correlated with compound exposure. Despite adequate PK and PD characteristics of BPN-14136 in dog, reliance of canids on non-RBP4 mechanisms of retinoid trafficking precludes evaluation of on-target toxicities for RBP4 antagonists in this species. Strong RBP4 lowering combined with good PK attributes and high BPN-14136 exposure achieved in NHP, along with the biology of retinoid trafficking that is similar to that of humans, support the choice of NHP as a non-rodent safety species.

Retinol binding protein IV purified from Escherichia coli using intein-mediated cleavage as a suitable replacement for serum sources

Retinol binding protein IV (RBP) functions as the principal carrier of retinol (Vitamin A) in the blood, where RBP circulates bound to another serum protein, transthyretin. Isolation of pure RBP from the transthyretin complex in human serum can be difficult, but expression of RBP in recombinant systems can circumvent these purification issues. Human recombinant RBP has previously been successfully expressed and purified from E. coli, but recovery of active protein typically requires extensive processing steps, such as denaturing and refolding, and complex purification steps, such as multi-modal chromatography. Furthermore, these methods produce recombinant proteins, often tagged, that display different functional and structural characteristics across systems. In this work, we optimized downstream processing by use of an intein-based expression system in E. coli to produce tag-free, human recombinant RBP (rRBP) with intact native amino termini at yields of up to ~15 mg/L off column. The novel method requires solubilization of inclusion bodies and subsequent oxidative refolding in the presence of retinol, but importantly allows for one-step chromatographic purification that yields high purity rRBP with no N-terminal Met or other tag. Previously reported purification methods typically require two or more chromatographic separation steps to recover tag-free rRBP. Given the interest in mechanistic understanding of RBP transport of retinol in health and disease, we characterized our purified product extensively to confirm rRBP is both structurally and functionally a suitable replacement for serum-derived RBP.

New insights into the metal-induced oxidative degradation pathways of transthyretin

The amyloidogenic mechanism of transthyretin is still debated but understanding it fully could lend insight into disease progression and potential therapeutics. Transthyretin was investigated revealing a metal-induced (Cr/Cu) oxidation pathway leading to N-terminal backbone fragmentation and oligomer formation; previously hidden details were revealed only by FT-IM-Orbitrap MS and surface-induced dissociation.

The hydrophobic C-terminal sequence of transthyretin affects its catalytic kinetics towards amidated neuropeptide Y

Transthyretin (TTR) is a transporter for thyroid hormone and retinol binding protein that has recently been reported to have proteolytic activity against certain substrates, including amidated neuropeptide Y (NPY). However, the proteolytic activity of TTR towards NPY is not fully understood. Here, we used fluorescence-based assays to determine the catalytic kinetics of human TTR towards human amidated NPY. The Michaelis constant (KM) and catalytic efficiency (kcat/KM) of TTR proteolysis were 15.88 ± 0.44 μm and 687 081 ± 35 692 m -1·s-1, respectively. In addition, we demonstrated an effect of the C-terminal sequence of TTR. When the C-terminal sequence of TTR was made more hydrophobic, the KM and kcat/KM changed to 12.87 ± 0.22 μm and 983 755 ± 18 704 m -1·s-1, respectively. Our results may be useful for the development of TTR as a therapeutic agent with low risk of the undesirable symptoms that develop from amidated NPY, and for further improvement of the kcat/KM of TTR.

Biomarkers mapping of neuropathic pain in a nerve chronic constriction injury mice model

Neuropathic pain is caused by a lesion or disease of the somatosensory nervous system and has a considerable impact on the quality of life. Neuropathic pain has a dynamic and complex aetiology and gives heterogeneous symptoms across patients; therefore, it represents an important clinical challenge. Current pharmacological treatment includes tricyclic antidepressant serotonin-noradrenaline uptake inhibitors such as duloxetine, pregabalin, and gabapentin. However, these drugs do not show efficacy in all patients suffering from neuropathic pain. In this work we used a nerve chronic constriction injury mice model based on the ligation of sciatic nerve to analyse, by two-dimensional electrophoresis and mass spectrometry, blood proteins significantly altered by neuropathic pain one-week after surgery. A sham-ligated group of mice acting as control and a group of ligated mice treated with gabapentin were also analysed. The results indicated that four haptoglobin isoforms were significantly more expressed, while transthyretin and alpha-2-macroglobulin expression decreased in the serum of the murine neuropathic pain model with respect to the control mice. Interestingly, the treatment with the gabapentin reversed these conditions. The outcomes of this study can provide a further understanding of the pathophysiological meaning of the biomarkers involved in neuropathic pain.

Increasing the length and hydrophobicity of the C-terminal sequence of transthyretin strengthens its binding affinity to retinol binding protein

Transthyretin (TTR) is a transporter for thyroid hormone (TH) and retinol, the latter via binding with retinol binding protein (RBP). Both the N‐terminal and C‐terminal regions of the TTR subunit are located in close proximity to the central binding channel for ligands. During the evolution of vertebrates, these regions changed in length and hydropathy. The changes in the N‐terminal sequence were demonstrated to affect the binding affinities for THs and RBP. Here, the effects of changes in the C‐terminal sequence were determined. Three chimeric TTRs, namely pigC/huTTR (human TTR with the C‐terminal sequence changed to that of Sus scrofa TTR), xenoN/pigC/huTTR (human TTR with the N‐terminal and C‐terminal sequences changed to those of Xenopus laevis and S. scrofa, respectively), and pigC/crocTTR (Crocodylus porosus TTR with the C‐terminal sequence changed to that of S. scrofa TTR), were constructed and their binding affinities for human RBP were determined at low TTR/RBP molar ratio using chemiluminescence immunoblotting. The binding dissociation constant (K_d) values of pigC/huTTR, xenoN/pigC/huTTR and pigC/crocTTR were 3.20 ± 0.35, 1.53 ± 0.38 and 0.31 ± 0.04 μm, respectively, and the K_d values of human and C. porosus TTR were 4.92 ± 0.68 and 1.42 ± 0.45 μm, respectively. These results demonstrate chimeric TTRs bound RBP with a higher strength than wild‐type TTRs, and the changes in the C‐terminal sequence of TTR had a positive effect on its binding affinity for RBP. In addition, changes to the N‐terminal and C‐terminal sequences showed comparable effects on the binding affinity.

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.

Transthyretin: A Transporter Protein Essential for Proliferation of Myoblast in the Myogenic Program

Irregularities in the cellular uptake of thyroid hormones significantly affect muscle development and regeneration. Herein, we report indispensable role of transthyretin (TTR) in maintaining cellular thyroxine level. TTR was found to enhance recruitment of muscle satellite cells to the site of injury, thereby regulating muscle regeneration. Fluorescence-activated cell sorting (FACS) and immunofluorescence analysis of TTR_wt (TTR wild type) and TTR_kd (TTR knock-down) cells revealed that TTR controlled cell cycle progression by affecting the expression of Cyclin A2. Deiodinase 2 (D2) mediated increases in triiodothyronine levels were found to regulate the expression of myogenic marker, myogenin (MYOG). Moreover, use of a coumarin derivative (CD) revealed a significant reduction in cellular thyroxine, thereby indicating that TTR play a role in the transport of thyroxine. Taken together, these findings suggest that TTR mediated transport of thyroxine represents a survival mechanism necessary for the myogenic program. The results of this study will be highly useful to the strategic development of novel therapeutics to combat muscular dystrophies.

Conserved chemosensory proteins in the proboscis and eyes of Lepidoptera

Odorant-binding proteins (OBPs) and chemosensory proteins (CSPs) are endowed with several different functions besides being carriers for pheromones and odorants. Based on a previous report of a CSP acting as surfactant in the proboscis of the moth Helicoverpa armigera, we revealed the presence of orthologue proteins in two other moths Plutella xylostella and Chilo suppressalis, as well as two butterflies Papilio machaon and Pieris rapae, using immunodetection and proteomic analysis. The unusual conservation of these proteins across large phylogenetic distances indicated a common specific function for these CSPs. This fact prompted us to search for other functions of these proteins and discovered that CSPs are abundantly expressed in the eyes of H. armigera and possibly involved as carriers for carotenoids and visual pigments. This hypothesis is supported by ligand-binding experiments and docking simulations with retinol and β-carotene. This last orange pigment, occurring in many fruits and vegetables, is an antioxidant and the precursor of visual pigments. We propose that structurally related CSPs solubilise nutritionally important carotenoids in the proboscis, while they act as carriers of both β-carotene and its derived products 3-hydroxyretinol and 3-hydroxyretinal in the eye. The use of soluble olfactory proteins, such as CSPs, as carriers for visual pigments in insects, here reported for the first time, parallels the function of retinol-binding protein in vertebrates, a lipocalin structurally related to vertebrate odorant-binding proteins.

Plasma concentrations of transthyretin in older Sardinians including centenarians

BACKGROUND AND AIMS

Plasma concentrations of transthyretin (TTR), a negative acute-phase protein, can be influenced by many factors including aging. Under physiological circumstances, TTR concentrations are very low in the fetus, increase slowly after birth up to the fifth decade and, then, decrease slowly. Some studies have shown sex-related differences up to about 70 years, when the differences disappear. The aim of this study was to evaluate the change in TTR concentrations in healthy males and females aged more than sixty, including numerous centenarians living in Sardinia, a large Italian island located in the Mediterranean Sea.

METHODS

The study sample consisted of 211 healthy subjects grouped by age and sex (male/female ratio: 1:1). Plasma TTR was assessed using a non-competitive enzyme immunoassay (ELISA Assaypro LLC, prealbumin AssayMAX Human ELISA Kit).

RESULTS

In subjects aged between 60 and 99 years, plasma TTR concentrations were higher compared to the reference ranges reported by CRM 470. Moreover, unlike other studies, sex-related differences in TTR concentrations were only observed in nonagenarians and centenarians.

CONCLUSIONS

We hypothesize that there are TTR-related genetic differences between the Sardinian population and other Caucasian ethnic groups. Further studies and a larger sample are needed to confirm our hypothesis.

Models for the binding channel of wild type and mutant transthyretin with glabridin

Our results indicate that additional high-occupancy hydrogen bonds were observed at the binding interface between the two dimers in V30A TTR, while stabilisation hydrophobic interactions between residues in the mutant AB loop decreased.

Proteomic analysis for early neurodegenerative biomarker detection in an animal model

The exposure to xenobiotics in the early stages of life represents the most important component in the etiology of many neurodegenerative disorders. Proteomic analysis of plasma and brain samples from early life treated animal model was performed in order to identify early biomarkers of neurodegeneration. Two-dimensional gel electrophoresis followed by liquid chromatography-tandem mass spectrometry identified four proteins in the plasma of adolescent rats that deviated from the control group. Low expression levels of transthyretin and plasma transferrin, and the absence of long-chain fatty acid transport 1 were measured. On the other hand, the same proteomic approach was done on striatum of an adult rat model of neurodegeneration. Mitochondrial aspartate aminotransferase and voltage-dependent anion channel were under expressed, while mitochondrial malate dehydrogenase, myelin basic protein and ubiquitin-60S ribosomal protein L40 were absent in striatum of animal model compared to control group. Data show that early biomarkers for the diagnosis of neurodegeneration can be obtained by proteomic analysis, starting from adolescent age and the results highlight the time frame for the onset of neurodegeneration due to early exposure to xenobiotics.

Bicyclic [3.3.0]-Octahydrocyclopenta[c]pyrrolo Antagonists of Retinol Binding Protein 4: Potential Treatment of Atrophic Age-Related Macular Degeneration and Stargardt Disease

Antagonists of retinol-binding protein 4 (RBP4) impede ocular uptake of serum all-trans retinol (1) and have been shown to reduce cytotoxic bisretinoid formation in the retinal pigment epithelium (RPE), which is associated with the pathogenesis of both dry age-related macular degeneration (AMD) and Stargardt disease. Thus, these agents show promise as a potential pharmacotherapy by which to stem further neurodegeneration and concomitant vision loss associated with geographic atrophy of the macula. We previously disclosed the discovery of a novel series of nonretinoid RBP4 antagonists, represented by bicyclic [3.3.0]-octahydrocyclopenta[c]pyrrolo analogue 4. We describe herein the utilization of a pyrimidine-4-carboxylic acid fragment as a suitable isostere for the anthranilic acid appendage of 4, which led to the discovery of standout antagonist 33. Analogue 33 possesses exquisite in vitro RBP4 binding affinity and favorable drug-like characteristics and was found to reduce circulating plasma RBP4 levels in vivo in a robust manner (>90%).

Network-Based Analysis on Orthogonal Separation of Human Plasma Uncovers Distinct High Density Lipoprotein Complexes

High density lipoprotein (HDL) particles are blood-borne complexes whose plasma levels have been associated with protection from cardiovascular disease (CVD). Recent studies have demonstrated the existence of distinct HDL subspecies; however, these have been difficult to isolate and characterize biochemically. Here, we present the first report that employs a network-based approach to systematically infer HDL subspecies. Healthy human plasma was separated into 58 fractions using our previously published three orthogonal chromatography techniques. Similar local migration patterns among HDL proteins were captured with a novel similarity score, and individual comigration networks were constructed for each fraction. By employing a graph mining algorithm, we identified 183 overlapped cliques, among which 38 were further selected as candidate HDL subparticles. Each of these 38 subparticles had at least two literature supports. In addition, GO function enrichment analysis showed that they were enriched with fundamental biological and CVD protective functions. Furthermore, gene knockout experiments in mouse model supported the validity of these subparticles related to three apolipoproteins. Finally, analysis of an apoA-I deficient human patient's plasma provided additional support for apoA-I related complexes. Further biochemical characterization of these putative subspecies may facilitate the mechanistic research of CVD and guide targeted therapeutics aimed at its mitigation.

Transthyretin microheterogeneity and molecular interactions: implications for amyloid formation

Aggregation of transthyretin (TTR), a plasma-binding protein for thyroxine and retinol-binding protein, is the cause of several amyloid diseases. Disease-associated mutations are well known, but wild-type TTR is, to a lesser extent, also amyloidogenic. Monomerization, not oligomer formation as in several other depository diseases, is the rate-limiting step in TTR aggregation, and stabilization of the natively tetrameric form can inhibit amyloid formation. Modifications on Cys10, as well as interactions with native ligands in plasma, were early found to influence the equilibrium between tetrameric and monomeric TTR by dissociating or stabilizing the tetramer. Following these discoveries, synthetic ligands for pharmacological prevention of TTR aggregation could be developed. In this article, we outline how the different types of TTR interactions and its microheterogeneity in plasma are related to its propensity to form amyloid fibrils. We conclude that plasma constituents and dietary components may act as natural TTR stabilizers whose mechanisms of action provide cues for the amelioration of TTR amyloid disease.

Design, synthesis, and evaluation of nonretinoid retinol binding protein 4 antagonists for the potential treatment of atrophic age-related macular degeneration and Stargardt disease

Accumulation of lipofuscin in the retina is associated with pathogenesis of atrophic age-related macular degeneration and Stargardt disease. Lipofuscin bisretinoids (exemplified by N-retinylidene-N-retinylethanolamine) seem to mediate lipofuscin toxicity. Synthesis of lipofuscin bisretinoids depends on the influx of retinol from serum to the retina. Compounds antagonizing the retinol-dependent interaction of retinol-binding protein 4 (RBP4) with transthyretin in the serum would reduce serum RBP4 and retinol and inhibit bisretinoid formation. We recently showed that A1120 (3), a potent carboxylic acid based RBP4 antagonist, can significantly reduce lipofuscin bisretinoid formation in the retinas of Abca4^–/– mice. As part of the NIH Blueprint Neurotherapeutics Network project we undertook the in vitro exploration to identify novel conformationally flexible and constrained RBP4 antagonists with improved potency and metabolic stability. We also demonstrate that upon acute and chronic dosing in rats, 43, a potent cyclopentyl fused pyrrolidine antagonist, reduced circulating plasma RBP4 protein levels by approximately 60%.

Temporal transcriptome analysis of the chicken embryo yolk sac

Background

The yolk sac (YS) is an extra-embryonic tissue that surrounds the yolk and absorbs, digests and transports nutrients during incubation of the avian embryo as well as during early term mammalian embryonic development. Understanding YS functions and development may enhance the efficient transfer of nutrients and optimize embryo development. To identify temporal large-scale patterns of gene expression and gain insights into processes and mechanisms in the YS, we performed a transcriptome study of the YS of chick embryos on embryonic days (E) E13, E15, E17, E19, and E21 (hatch).

Results

3547 genes exhibited a significantly changed expression across days. Clustering and functional annotation of these genes as well as histological sectioning of the YS revealed that we monitored two cell types: the epithelial cells and the erythropoietic cells of the YS. We observed a significant up-regulation of epithelial genes involved in lipid transport and metabolism between E13 and E19. YS epithelial cells expressed a vast array of lipoprotein receptors and fatty acid transporters. Several lysosomal genes (CTSA, PSAP, NPC2) and apolipoproteins genes (apoA1, A2, B, C3) were among the highest expressed, reflecting the intensive digestion and re-synthesis of lipoproteins in YS epithelial cells. Genes associated with cytoskeletal structure were down-regulated between E17 and E21 supporting histological evidence of a degradation of YS epithelial cells towards hatch.

Expression patterns of hemoglobin synthesis genes indicated a high erythropoietic capacity of the YS between E13 and E15, which decreased towards hatch. YS histological sections confirmed these results. We also observed that YS epithelial cells expressed high levels of genes coding for plasma carrier proteins (ALB, AFP, LTF, TTR), normally produced by the liver.

Conclusions

Here we expand current knowledge on developmental, nutritional and molecular processes in the YS. We demonstrate that in the final week of chick embryonic development, the YS plays different roles to support or replace the functions of several organs that have not yet reached their full functional capacity. The YS has a similar functional role as the intestine in digestion and transport of nutrients, the liver in producing plasma carrier proteins and coagulation factors, and the bone marrow in synthesis of blood cells.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-690) contains supplementary material, which is available to authorized users.

Expression of Transthyretin during bovine myogenic satellite cell differentiation

Adult myogenesis responsible for the maintenance and repair of muscle tissue is mainly under the control of myogenic regulatory factors (MRFs) and a few other genes. Transthyretin gene (TTR), codes for a carrier protein for thyroxin (T4) and retinol binding protein bound with retinol in blood plasma, plays a critical role during the early stages of myogenesis. Herein, we investigated the relationship of TTR with other muscle-specific genes and report their expression in muscle satellite cells (MSCs), and increased messenger RNA (mRNA) and protein expression of TTR during MSCs differentiation. Silencing of TTR resulted in decreased myotube formation and decreased expression of myosin light chain (MYL2), myosin heavy chain 3 (MYH3), matrix gla protein (MGP), and voltage-dependent L type calcium channel (Cav1.1) genes. Increased mRNA expression observed in TTR and other myogenic genes with the addition of T4 decreased significantly following TTR knockdown, indicating the critical role of TTR in T4 transportation. Similarly, decreased expression of MGP and Cav1.1 following TTR knockdown signifies the dual role of TTR in controlling muscle myogenesis via regulation of T4 and calcium channel. Our computational and experimental evidences indicate that TTR has a relationship with MRFs and may act on calcium channel and related genes.

Biomarkers for amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is the most common form of motor neuron disease. ALS is a fatal neurodegenerative disease and clinical diagnosis typically takes many months to complete. Early disease diagnosis through the use of biomarkers may aid in correct clinical management of patients and possibly delay time to ventilator and morbidity. This review explores the progress of biomarker discovery efforts for ALS and the many challenges that remain. Included are different technologies utilized in biomarker discovery efforts (proteomic, genomic and metabolomic) and putative biomarkers uncovered using these techniques. These studies have discovered genetic mutations leading to familial forms of ALS, and specific protein alterations that occur in biological fluids (cerebrospinal fluid and blood) and/or tissues of ALS subjects. More recent high-throughput technologies have revealed panels of proteomic or metabolic biomarkers that can discriminate between ALS and control groups. The identification of disease-specific biomarkers will provide opportunities to develop early diagnostic measures as well as surrogate markers to monitor disease progression and test drug efficacy in clinical trials.

Ophthalmic manifestations in a Chinese family with familial amyloid polyneuropathy due to a TTR Gly83Arg mutation

PURPOSE

To describe the characteristic ophthalmic phenotypes of a large Chinese family with familial amyloid polyneuropathy due to a missense mutation in transthyretin (TTR) (c.307 C>G).

METHODS

Twenty-seven individuals (12 affected, 15 unaffected) from a five-generation Chinese family underwent general medical examination and comprehensive ophthalmic examination, including best correct visual acuity, intraocular pressure measurements, Schirmer test, slitlamp examination, fundoscopy, and ocular ultrasonography. Histological examination of vitreous biopsies using Congo red staining and immunohistochemistry was performed. Cardiovascular magnetic resonance (CMR), electrocardiogram, and echocardiogram were used to evaluate cardiac amyloidosis. Electromyography was used to evaluate nerve function. All four exons of TTR were amplified by PCR, sequenced using a Bigdye terminator v3.1 cycle sequencing kit and analyzed on an ABI 3700XL Genetic Analyzer.

RESULTS

All 12 affected individuals in the family had ocular manifestations, including severe vitreous opacities, secondary glaucoma, xerophthalmia, dyscoria, and attenuated retinal arteries. Congo red staining demonstrated amyloid deposits in the vitreous, and immunohistochemical staining confirmed the deposition of TTR proteins in the vitreous. Twelve individuals had polyneuropathy, and electromyography detected functional damage in peripheral nerves. One individual was diagnosed with cardiac amyloidosis by CMR. Direct sequencing revealed the heterozygous missense mutation in TTR (c.307 C>G p.Gly83Arg) in all 12 affected individuals. The mutation co-segregated with the disease phenotype and was absent in 100 normal controls.

CONCLUSIONS

Vitreous opacity is very common in patients with the TTR Gly83Arg mutation; other clinical characteristics associated with the mutation include polyneuropathy and cardiac amyloidosis.

Pharmacological inhibition of lipofuscin accumulation in the retina as a therapeutic strategy for dry AMD treatment

Age-related macular degeneration (AMD) is the leading cause of blindness in the western world. There is no FDA-approved treatment for the most prevalent dry (atrophic) form of AMD. Photoreceptor degeneration in dry AMD is triggered by abnormalities in the retinal pigment epithelium (RPE). It has been suggested that excessive accumulation of fluorescent lipofuscin pigment in the RPE represents an important pathogenic factor in etiology and progression of dry AMD. Cytotoxic lipofuscin bisretinoids, such as A2E, are formed in the retina in a non-enzymatic way from visual cycle retinoids. Inhibition of toxic bisretinoid production in the retina seems to be a sound treatment strategy for dry AMD. In this review we discuss the following classes of pharmacological treatments inhibiting lipofuscin bisretinoid formation in the retina: direct inhibitors of key visual cycle enzymes, RBP4 antagonists, primary amine-containing aldehyde traps, and deuterated analogs of vitamin A.

Probiotics promote rapid-turnover protein production by restoring gut flora in patients with alcoholic liver cirrhosis

BACKGROUND AND AIMS

Accumulating evidence suggests that deterioration of the gut flora contributes to the pathogenesis of alcoholic liver cirrhosis (ALC). However, the ALC flora profile and its response to probiotic treatment have not been fully examined. This double-blind placebo-controlled study aimed to evaluate whether the probiotic beverage Yakult 400 (Y400), which contains Lactobacillus casei strain Shirota, improves liver function in ALC patients, and to analyze the precise gut flora profile by real-time quantitative PCR (qPCR).

METHODS

A total of 37 hospitalized ALC patients were randomly allocated to Y400 (n = 18) and placebo (n = 19) groups. Y400 or placebo was served twice a day during the first half of the four-week study. Serum concentrations of rapid-turnover proteins (i.e., transthyretin and transferrin), hypersensitive C-reactive protein, and interleukin-6 were measured weekly. qPCR analysis of fecal bacteria was performed biweekly; stocked fecal samples from 46 healthy subjects were used as references.

RESULTS

Serum transthyretin levels significantly increased in the Y400 group in week 3; similar-although statistically insignificant-increases were seen for transferrin and albumin. Levels of hypersensitive C-reactive protein, but not interleukin-6, significantly decreased in week 4. Before treatment, populations of obligate anerobic bacteria were significantly smaller and those of Enterobacteriaceae were larger in patients than in healthy subjects examined in a previous study. Y400 corrected this imbalance.

CONCLUSIONS

This is the first report describing the unique gut flora of ALC patients. Y400 treatment normalized the gut flora and improved liver function. These promising findings warrant further investigation in larger, multicenter studies.

Circulating thyroxine, thyroid-stimulating hormone, and hypothyroid status and the risk of prostate cancer

BACKGROUND

Thyroid hormones may influence risk of cancer through their role in cell differentiation, growth, and metabolism. One study of circulating thyroid hormones supports this hypothesis with respect to prostate cancer. We undertook a prospective analysis of thyroid hormones and prostate cancer risk in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study.

METHODS

Within the ATBC Study, a randomized controlled trial of α-tocopherol and β-carotene supplements and cancer incidence in male smokers, 402 prostate cancer cases were sampled. Controls were matched 2:1 to cases on age and date of blood collection. Odds ratios (OR) and 95% confidence intervals (CI) of prostate cancer were estimated for quintiles of serum total and free thyroxine (T4), thyroid-stimulating hormone (TSH), thyroid-binding globulin (TBG), and by categories of thyroid status.

RESULTS

Men with serum higher TSH had a decreased risk of prostate cancer compared to men with lower TSH (Q5 vs. Q1-4: OR = 0.70, 95% CI: 0.51-0.97, p = 0.03). When the T4 and TSH measurements were combined to define men as hypothyroid, euthyroid or hyperthyroid, hypothyroid men had a lower risk of prostate cancer compared to euthyroid men (OR = 0.48, 95% CI = 0.28-0.81, p = 0.006). We observed no association between hyperthyroid status and risk, although the number of hyperthyroid men with prostate cancer was small (n = 9).

CONCLUSIONS

In this prospective study of smokers, men with elevated TSH and those classified as being in a hypothyroid state were at decreased risk of prostate cancer. Future studies should examine the association in other populations, particularly non-smokers and other racial/ethnic groups.

Vitreous surgery impact in glaucoma development in liver transplanted familial amyloidosis ATTR V30M Portuguese patients

PURPOSE

Familial amyloidosis with polyneuropathy (FAP) sometimes courses with vitreous amyloid. The aim of this study was to evaluate the incidence of glaucoma after vitrectomy in FAP patients.

METHODS

A total of 79 eyes of 42 liver transplanted FAP patients and 16 eyes of 16 non-FAP patients with rhegmatogenous retina detachment were collected. The patients were divided in to three groups: Group I - FAP patients with vitreous opacities submitted to vitrectomy, Group II - FAP patients without vitreous opacities and not submitted to vitrectomy and, Group III - non-FAP patients with rhegmatogenous retinal detachment submitted to vitrectomy. The Group I was subdivided into: Ia - "complete" vitrectomy; Ib - "incomplete" vitrectomy. The onset of glaucoma was considered when the intraocular pressure level was higher than 21 mmHg, with concomitant visual field abnormalities and optic nerve cupping.

RESULTS

Post vitrectomy glaucoma was more frequent in Group I (56.1%) than in Group III (12.5%) and in Group II (10.5%). We observed a higher incidence of glaucoma in the Ia than in the Ib subgroup (86.4 vs. 21.1%) and earlier appearance in subgroup Ia (7.9 ± 3.6 vs. 39.5 ± 6.6 months).

CONCLUSION

Vitrectomy induced the development of glaucoma in FAP patients.

Human placental transthyretin in fetal growth restriction in combination with preeclampsia and the HELLP syndrome

Fetal growth restriction is a serious, still poorly understood pregnancy-related pathology often associated with preeclampsia. Recent studies speculate on the role of human transthyretin, a carrier protein for thyroxin and retinol binding protein, in the etiology of both pregnancy pathologies. Objective was to investigate the localization and abundance of transthyretin (TTR) in placentas of pregnancies suffering from fetal growth restriction with and without preeclampsia and HELLP. This was a retrospective case control study on human paraffin-embedded placentas from pregnancies with a gestational age at delivery between the 24th and 34th week of gestation. 16 placentas were included in this study, 11 cases and 5 from normotensive pregnancies as controls. Cases were divided into three groups: four from early onset idiopathic intrauterine growth restriction (IUGR), four from early-onset severe preeclampsia (PE), and three from early-onset IUGR with preeclampsia plus HELLP syndrome. Distribution and abundance of TTR were investigated by means of immunohistochemistry. Semi quantitative analysis of TTR staining of placental sections revealed that TTR was mostly expressed in the villous trophoblast covering placental villi. Only weak staining of TTR in villous stroma could be detected. The comparison of placentas revealed that in pure IUGR and severe PE there is a much stronger TTR reactivity compared to controls and cases with IUGR + PE + HELLP. Concluding, the study showed that TTR is dysregulated in cases of IUGR and severe early onset preeclampsia. Interestingly, TTR expression is not affected in cases with HELLP syndrome that reveal the same staining intensities as age-matched controls.

Identification of beta-amyloid-binding sites on transthyretin

Transthyretin (TTR) binds to the Alzheimer-related peptide beta-amyloid (Aβ), and may protect against Aβ-induced neurotoxicity. In this work, the specific domains on TTR involved with binding to Aβ were probed. An array was constructed of peptides derived from overlapping sequences from TTR. Strong binding of Aβ to TIAALLSPYSYS (residues 106-117) was detected, corresponding to strand G on the inner β-sheet of TTR. Aβ bound weakly to four contiguous peptides spanning residues 59-83, which includes strand E through the E/F helix and loop. To further pinpoint specific residues on TTR involved with Aβ binding, nine alanine mutants were generated: I68A, I73A, K76A, L82A, I84A, S85A, L17A, T106A and L110A. Aβ binding was significantly inhibited only in L82A and L110A, indicating that Aβ binding to TTR is mediated through these bulky hydrophobic leucines. Aβ binding to L17A and S85A was significantly higher than to wild-type TTR. Enhancement of binding in L17A is postulated to arise from reduced steric restriction to the interior L110 site, since these two residues are adjacent in the native protein. The S85A mutation caused a reduction in TTR tetramer stability; increased Aβ binding is postulated to be a direct consequence of the reduced quaternary stability.

Differential proteomic distribution of TTR (pre-albumin) forms in serum and HDL of patients with high cardiovascular risk

Inflammation is a common condition contributing to cardiovascular disease progression which leads to clinical manifestations such as acute myocardial infarction (AMI). By applying a proteomic expression profiling approach we have investigated changes in transthyretin (TTR) in AMI-patients and its distribution patterns in HDL samples of patients with high cardiovascular risk, such as those with familiar hypercholesterolemia (FH).

METHODS AND RESULTS

The characterization by bidimensional electrophoresis (2-DE), followed by mass-spectrometry (MALDI-TOF) of serum samples revealed changes in the intensity of the TTR spot with a pI of 5.6 and a Mw of 42kDa (tTTR) between AMI-patients in association to diabetic dyslipemia. Serum TTR levels, determined by commercial ELISA, were significantly lower (p<0.0001) in AMI-patients (n=39) and FH-patients (n=100) than in healthy controls (n=60). Western blot and 2-DE analysis showed a differential distribution profile of TTR forms between serum, where 3 TTR forms of 42 (tTTR), 28 (dTTR), and 14kDa (mTTR) were detected, and HDL samples, where only mTTR was present.

CONCLUSIONS

Our results demonstrate alterations in TTR proteomic profile in relation to the clustering of risk factors which seems to highlight the implication of TTR in cardiovascular risk. The significant differences in TTR between serum (tTTR) and HDL (mTTR) underscore the importance of TTR-forms in the circulation and deserve further investigation to understand their function.