Human Amyloidosis Research Articles

Systemic AL kappa chain amyloidosis in a captive Bornean orangutan (Pongo pygmaeus)

Systemic amyloid light-chain (AL) amyloidosis is an infrequent disease in which amyloid fibrils derived from the immunoglobulin light chain are deposited in systemic organs, resulting in functional impairment. This disease has been notably uncommon in animals, and nonhuman primates have not been reported to develop it. In this study, we identified the systemic AL kappa chain amyloidosis in a captive Bornean orangutan (Pongo pygmaeus) and analyzed its pathogenesis. Amyloid deposits were found severely in the submucosa of the large intestine, lung, mandibular lymph nodes, and mediastinal lymph nodes, with milder lesions in the liver and kidney. Mass spectrometry-based proteomic analysis revealed an abundant constant domain of the immunoglobulin kappa chain in the amyloid deposits. Immunohistochemistry further confirmed that the amyloid deposits were positive for immunoglobulin kappa chains. In this animal, AL amyloidosis resulted in severe involvement of the gastrointestinal submucosa and lymph nodes, which is consistent with the characteristics of AL amyloidosis in humans, suggesting that AL amyloid may have a similar deposition mechanism across species. This report enhances the pathological understanding of systemic AL amyloidosis in animals by providing a detailed characterization of this disease based on proteomic analysis.

Apolipoprotein C-III amyloidosis in white lions (Panthera leo).

Apolipoprotein C-III (ApoC-III) amyloidosis in humans is a hereditary amyloidosis caused by a D25V mutation in the APOC3 gene. This condition has only been reported in a French family and not in animals. We analyzed a 19-year-old white lion (Panthera leo) that died in a Japanese safari park and found renal amyloidosis characterized by severe deposition confined to the renal corticomedullary border zone. Mass spectrometry-based proteomic analysis identified ApoC-III as a major component of renal amyloid deposits. Amyloid deposits were also positive for ApoC-III by immunohistochemistry. Based on these results, this case was diagnosed as ApoC-III amyloidosis for the first time in nonhuman animals. Five additional white lions were also tested for amyloid deposition retrospectively. ApoC-III amyloid deposition was detected in 3 white lions aged 19 to 21 years but not in 2 cases aged 0.5 and 10 years. Genetic analysis of white and regular-colored lions revealed that the APOC3 sequences of the lions were identical, regardless of amyloid deposition. These results suggest that ApoC-III amyloidosis in lions, unlike in humans, may not be a hereditary condition but an age-related condition. Interestingly, lion ApoC-III has a Val30 substitution compared with other species of Panthera that have Met30. Structural predictions suggest that the conformation of ApoC-III with Met30 and ApoC-III with Val30 are almost identical, but this substitution may alter the ability to bind to lipids. As with the D25V mutation in human ApoC-III, the Val30 substitution in lions may increase the proportion of free ApoC-III, leading to amyloid formation.

AmyloComp: A Bioinformatic Tool for Prediction of Amyloid Co-aggregation

Typically, amyloid fibrils consist of multiple copies of the same protein. In these fibrils, each polypeptide chain adopts the same β-arc-containing conformation and these chains are stacked in a parallel and in-register manner. In the last few years, however, a considerable body of data has been accumulated about co-aggregation of different amyloid-forming proteins. Among known examples of the co-aggregation are heteroaggregates of different yeast prions and human proteins Rip1 and Rip3. Since the co-aggregation is linked to such important phenomena as infectivity of amyloids and molecular mechanisms of functional amyloids, we analyzed its structural aspects in more details. An axial stacking of different proteins within the same amyloid fibril is one of the most common type of co-aggregation. By using an approach based on structural similarity of the growing tips of amyloids, we developed a computational method to predict amyloidogenic β-arch structures that are able to interact with each other by the axial stacking. Furthermore, we compiled a dataset consisting of 26 experimentally known pairs of proteins capable or incapable to co-aggregate. We utilized this dataset to test and refine our algorithm. The developed method opens a way for a number of applications, including the identification of microbial proteins capable triggering amyloidosis in humans. AmyloComp is available on the website: https://bioinfo.crbm.cnrs.fr/index.php?route=tools&tool=30.

Single Nucleotide Polymorphisms Associated with AA-Amyloidosis in Siamese and Oriental Shorthair Cats.

AA-amyloidosis in Siamese and Oriental shorthair cats is a lethal condition in which amyloid deposits accumulate systemically, especially in the liver and the thyroid gland. The age at death of affected cats varies between one and seven years. A previous study indicated a complex mode of inheritance involving a major locus. In the present study, we performed a multi-locus genome-wide association study (GWAS) using five methods (mrMLM, FASTmrMLM, FASTmrEMMA, pLARmEB and ISIS EM-BLASSO) to identify variants associated with AA-amyloidosis in Siamese/Oriental cats. We genotyped 20 affected mixed Siamese/Oriental cats from a cattery and 48 healthy controls from the same breeds using the Illumina Infinium Feline 63 K iSelect DNA array. The multi-locus GWAS revealed eight significantly associated single nucleotide polymorphisms (SNPs) on FCA A1, D1, D2 and D3. The genomic regions harboring these SNPs contain 55 genes, of which 3 are associated with amyloidosis in humans or mice. One of these genes is SAA1, which encodes for a member of the Serum Amyloid A family, the precursor protein of Amyloid A, and a mutation in the promotor of this gene causes hereditary AA-amyloidosis in humans. These results provide novel knowledge regarding the complex genetic background of hereditary AA-amyloidosis in Siamese/Oriental cats and, therefore, contribute to future genomic studies of this disease in cats.

Proteomics-Based Analysis and Diagnosis of Formalin-Fixed Paraffin-Embedded Amyloidosis Samples.

Amyloidosis is a group of rare pathologies characterized by abnormal folding and deposition of susceptible proteins in tissues and organs. Diagnosis of amyloidosis often relies on immunohistochemistry of formalin-fixed paraffin-embedded (FFPE) patient samples; however, dependency on antibodies for protein staining is one of the major pitfalls of this approach, especially for the detection of rare amyloidosis types. In recent years, mass spectrometry-based proteomics has emerged as a promising alternative for adequate detection and amyloid typing, despite the fact that preparing FFPE samples for proteomics remains a challenging task. Major hurdles are removal of formalin-induced protein cross-links and water-insoluble paraffin prior to mass spectrometry analysis. With the recent development of the suspension trapping protocol, enabling the use of high concentrations of SDS, these obstacles can be overcome. In this chapter, we describe the implementation of suspension trapping for FFPE sample processing and its application to analyze human amyloidosis samples, comparing a standard procedure with probe sonication with a more advanced workflow based on ultrasonication.

Genetically modified yeasts in studies of human amyloidosis

Amyloid protein aggregation is a key factor in the development of a variety of serious diseases in humans, commonly named as amyloidoses (Alzheimers and Parkinsons diseases, type II diabetes, etc.), and a determinant of protein-based inheritance in lower eukaryotes. In yeast, translation termination factor Sup35 is one of the most extensively studied amyloidogenic proteins. Aggregation of Sup35 (induction of [PSI+] prion) decreases its functional activity and leads to the suppression of nonsense-mutation as stop-codons become recognized as meaningful more frequently. This phenomenon is the basis of phenotypic detection of Sup35 aggregation in yeast strains possessing nonsense mutation ade1-14 in ADE1 gene.
 Yeast is convenient model for genetic, biochemical and molecular biology studies. Yeast genome can be easily edited and plasmids can be used for induction of gene expression. Yeast is suitable for analysis of mammalian genes and proteins and thus can be applied for the analysis of amyloidogenic properties of proteins associated with human diseases. Phenotyping detection of [PSI+] prion can be modified for the analysis of amyloid aggregation of mammalian proteins in yeast.
 We use genetically modified yeasts Saccharomyces cerevisiae adopted for amyloid biology research. The mutations leading to auxotrophy toward certain amino acids (leucine, lysine, tryptophane, histidine) and nucleobases (adenine, uracil) were implemented into yeast genome allowing phenotyping detection of [PSI+] and the usage of plasmids for the investigation of mammalian protein in yeast.
 Application of yeast-based experimental system for studies of different aspects of human amyloidoses is discussed.
 This study was supported by Saint Petersburg State University (project 93025998).

Altering Brain Amyloidosis by Intra-Lingual and Extra-Nasal Exposure of Aβ Aggregates.

Extensive experimental and human-derived evidence suggest that misfolded Aβ particles spread similarly to infectious prions. Moreover, peripheral administration of Aβ seeds accelerates brain amyloidosis in both susceptible experimental animals and humans. The mechanisms and elements governing the transport of misfolded Aβ from the periphery to the brain are not fully understood, although circulation and retrograde axonal transport have been proposed. Here, we demonstrate that injection of Aβ seeds in the tongue, a highly innervated organ, substantially accelerates the appearance of plaques in Tg2576 mice. In addition, the extra-nasal exposure of Aβ aggregates increased amyloid pathology in the olfactory bulb. Our results show that exposing highly innervated tissues to Aβ seeds accelerates AD-like pathological features, and suggest that Aβ seeds can be transported from peripheral compartments to the brain by retrograde axonal transport. Research in this direction may be relevant on different fronts, including disease mechanisms, diagnosis, and risk-evaluation of potential iatrogenic transmission of Aβ misfolding.

The Role of Circulating Aβ Seeds in the Progression of Cerebral Amyloidosis.

While understudied, it is suspected that peripheral Aβ peptides affect Alzheimer’s disease (AD)-associated pathological changes in the brain. The peripheral sink hypothesis postulates that the central and peripheral pools of Aβ co-exist in equilibrium. As such, cerebral amyloid levels may be modulated by intervening circulating Aβ. In this commentary, we discuss relevant literature supporting the potential role of peripheral Aβ in exacerbating brain amyloidosis in both humans and mouse models of AD. Moreover, we highlight the need to further understand the mechanisms by which circulating Aβ peptides may reach the brain and contribute to neuropathology. Finally, we discuss the implications of targeting peripheral Aβ as a therapeutic approach in treating AD.

Dopamine-Conjugated Carbon Dots Inhibit Human Calcitonin Fibrillation.

The development of biocompatible nanomaterials has become a new trend in the treatment and prevention of human amyloidosis. Human calcitonin (hCT), a hormone peptide secreted from parafollicular cells, plays a major role in calcium–phosphorus metabolism. Moreover, it can be used in the treatment of osteoporosis and Paget’s disease. Unfortunately, it tends to form amyloid fibrils irreversibly in an aqueous solution, resulting in a reduction of its bioavailability and therapeutic activity. Salmon calcitonin is the replacement of hCT as a widely therapeutic agent due to its lower propensity in aggregation and better bioactivity. Herein, we used citric acid to synthesize carbon dots (CDs) and modified their surface properties by a variety of chemical conjugations to provide different functionalized CDs. It was found that dopamine-conjugated CDs can effectively inhibit hCT aggregation especially in the fibril growth phase and dissociate preformed hCT amyloids. Although the decomposition mechanism of dopamine-conjugated CDs is not clear, it seems to be specific to hCT amyloids. In addition, we also tested dopamine-conjugated mesoporous silica nanoparticles in preventing hCT fibrillization. They also can work as inhibitors but are much less effective than CDs. Our studies emphasized the importance of the size and surface functionalization of core materials in the development of nanomaterials as emerging treatments for amyloidosis. On the other hand, proper functionalized CDs would be useful in hCT formulation.

SYSTEMIC AMYLOIDOSIS IN YOUNG MICE INDUCED BY HUMAN SALIVA ADMINISTRATION

The urgency of the study lies in the fact that for the first time it was proved in the experiment that intraperitoneal administration of human saliva to young mice causes the development of systemic amyloidosis, comparable to hereditary systemic amyloidosis in humans, induced by mutagenic changes in saliva lysozyme. The aim of the research: to test human saliva as an amyloidogen in a model experiment on young mice in comparison with the albumin model of amyloidosis that we developed earlier. White male mice weighing 20.0–25.0 g were divided into six groups: Intact mice (5); 30 days 1 time every other day were intraperitoneally administered to groups: 1 (5) soy cream substitute TU 9199-004-58706213-10 15 10 g/100 ml water 0.1 ml/10 g; 2 (3) saliva of a healthy person (SHP) 0.5 ml; 3 (3) SHP and Ciprofloxacin (C) 0.05 mg/10 g of weight; 4 (3) saliva of a person with chronic tonsillitis (remission, SCT); 5 (3) SCT+C. Kidney weight changed from 176.0±21 mg in intact mice (IM) to 197±43,0, 195,0±18,0, 195,0±18,0, 183,0±44,0, 153,0±25,0 mg, respectively. The number of cells per visual field of the tubular epithelium decreased by 1.3, 1.2, 1.6, 1.4, 1.4 times from the number of cells per visual field in IM 380.0±84.0 (p = 0.00), glomerular cells – by 1.4, 1.1, 1.3, 1.2, 1.2 times from the number of glomerular cells in IM 34.0±11.0 (p = 0.02), in groups 1-5, respectively. The glomerular area decreased by 2.4, 2.7, 2.3, 2.4, 3.0 times from the average glomerular area in IM (3163.7±832.7 mm2, p = 0.0000). The relative area of amyloid lesion when stained with Congo red: 18.4±8.2% (group 1), 26,7±10,6, 35,0±11,9, 45,7±13,2, 63,6±14,0% (groups 1-5). The spleen mass and length increased from 133.0±16.0 mg (IM) by 1.7, 1.7, 1.8, 2.1, 1.7 times and from 17.0±2.0 mm (IM) by 1.2, 1.2, 1.3, 1.4, 1.2 times, the number of cells per visual field decreased from 1318±205 (IM) by 1.7, 2.0, 3.3, 2.1, 2.0 times, groups 1-5, respectively (p < 0.01). The relative area of amyloid lesion in Congo red staining: 11,4±9,4%, 28,2±16,0, 27,9±20,8, 20,9±12,2, 16,5±8,3% (groups 1-5). The liver mass changed from 1.4±0.15 g (IM) to 1,57±0,26, 1,45±0,18, 1,53±0,1, 1,71±0,3, 1,36±0,4 g, the number of cells per visual field decreased from 67.0±15.0 (IM) by 1.9, 1.4, 1.8, 2.5, 1.9 times, the area of hepatocyte nuclei – from 54.0±12.3 µm (IM) by 3.1, 3.6, 4.2, 3.1, 3.3 times (groups 1-5, respectively, p < 0.01). The relative area of amyloid lesion in Congo red staining: 6,8±4,6%, 15,3±11,0, 24,5±12,8, 9,8±8,5, 12,6±2,3% (groups 1-5). Conclusions: 1) human saliva when administered intraperitoneally causes severe systemic amyloidosis in young mice with damage to the liver, kidneys and the spleen, which manifests more by cytotoxic effect than the volume of amyloid deposition; 2) human saliva contains a more active amyloidogen than albumin in combination with fillers of the soy cream substitute formulation; 2) human saliva of a person with chronic tonsillitis in remission is more amyloidogenic than the saliva of a healthy person; 3) Ciprofloxacin, administered in a therapeutic dose during the amyloid model formation, moderately increases the severity of amyloid organ damage; 4) human saliva can be used to simulate amyloidosis in an experiment on young mice; 5) the liver may contain enzymatic systems that perform the function of amyloidoclasia.

Repurposing Benzbromarone for Familial Amyloid Polyneuropathy: A New Transthyretin Tetramer Stabilizer.

Transthyretin (TTR) is a homotetrameric protein involved in human amyloidosis, including familial amyloid polyneuropathy (FAP). Discovering small-molecule stabilizers of the TTR tetramer is a therapeutic strategy for these diseases. Tafamidis, the only approved drug for FAP treatment, is not effective for all patients. Herein, we discovered that benzbromarone (BBM), a uricosuric drug, is an effective TTR stabilizer and inhibitor against TTR amyloid fibril formation. BBM rendered TTR more resistant to urea denaturation, similarly to iododiflunisal (IDIF), a very potent TTR stabilizer. BBM competes with thyroxine for binding in the TTR central channel, with an IC50 similar to IDIF and tafamidis. Results obtained by isothermal titration calorimetry (ITC) demonstrated that BBM binds TTR with an affinity similar to IDIF, tolcapone and tafamidis, confirming BBM as a potent binder of TTR. The crystal structure of the BBM-TTR complex shows two molecules binding deeply in the thyroxine binding channel, forming strong intermonomer hydrogen bonds and increasing the stability of the TTR tetramer. Finally, kinetic analysis of the ability of BBM to inhibit TTR fibrillogenesis at acidic pH and comparison with other stabilizers revealed that benzbromarone is a potent inhibitor of TTR amyloidogenesis, adding a new interesting scaffold for drug design of TTR stabilizers.

Amyloidogenesis of feline amylin and plasma levels in cats with diabetes mellitus or pancreatitis

Amylin is a pancreatic hormone cosecreted along with insulin and involved in pancreatic amyloidosis and β-cell apoptosis in diabetic cats and humans. Amylin is usually elevated in early stages of type 2 diabetes but recently was found to be increased in acute and chronic pancreatitis in humans. Currently, there are little data about feline amylin propensity to fibrillate and no information on circulating levels of this hormone during feline pancreatitis. We compared 4 amylin analogues and found cat amylin to be more prone to amyloid fibrillation than human amylin, the triple-proline analogue pramlintide and rat amylin. We also measured plasma amylin levels in healthy lean cats, diabetic cats, and cats with pancreatitis. Plasma amylin was higher in diabetic cats compared with healthy lean cats (P < 0.001). Interestingly, amylin levels during pancreatitis were higher than those of both lean cats (P < 0.0001) and diabetic cats without pancreatitis (P < 0.005). These data support evidence of feline amylin being more prone to aggregation than human amylin in vitro, which may influence diabetes mellitus progression and β-cell failure in vivo. Furthermore, our data show an increase in amylin levels during feline pancreatitis and the need for future research on the role of this hormone in the pathogenesis of pancreatic inflammation associated to feline diabetes mellitus.

Amyloid Signature Proteins in Feline Amyloidosis

In human amyloidoses, amyloid signature proteins (ASPs), such as serum amyloid P component (SAP) and apolipoprotein E (ApoE), are deposited in tissues together with amyloid fibrils and are implicated in the pathogenesis of amyloidosis. Few reports describe ASPs in animals. In this study, we examined feline amyloidosis and performed immunohistochemical and proteomic analyses of SAP, ApoE, apolipoprotein A-I (ApoAI) and apolipoprotein A-IV (ApoAIV). Ten cases of systemic amyloidosis, three cases of amyloid-producing odontogenic tumour and three cases of islet amyloidosis were used for immunohistochemistry (IHC) and/or proteomic analyses. IHC showed that ApoE was present in amyloid deposits in all samples. ApoAI and ApoAIV differed in the degree of co-deposition with amyloid depending on the type of amyloid and the affected organ. SAP was negative in all amyloid deposits. Proteomic analysis showed that ApoE was present in all samples, but ApoAI and ApoAIV were detected only in some samples and SAP was not detected in any samples. The observation that ApoE was detected in all types of amyloid suggests the involvement of ApoE in the development of feline amyloidosis. ASPs in feline amyloidosis are significantly different from those in human amyloidosis, suggesting that the involvement of ASPs in the pathological condition differs between animal species.

Diversity in A\u03b2 deposit morphology and secondary proteome insolubility across models of Alzheimer-type\xa0amyloidosis

A hallmark pathology of Alzheimer’s disease (AD) is the formation of amyloid β (Aβ) deposits that exhibit diverse localization and morphologies, ranging from diffuse to cored-neuritic deposits in brain parenchyma, with cerebral vascular deposition in leptomeningeal and parenchymal compartments. Most AD brains exhibit the full spectrum of pathologic Aβ morphologies. In the course of studies to model AD amyloidosis, we have generated multiple transgenic mouse models that vary in the nature of the transgene constructs that are expressed; including the species origin of Aβ peptides, the levels and length of Aβ that is deposited, and whether mutant presenilin 1 (PS1) is co-expressed. These models recapitulate features of human AD amyloidosis, but interestingly some models can produce pathology in which one type of Aβ morphology dominates. In prior studies of mice that primarily develop cored-neuritic deposits, we determined that Aβ deposition is associated with changes in cytosolic protein solubility in which a subset of proteins become detergent-insoluble, indicative of secondary proteome instability. Here, we survey changes in cytosolic protein solubility across seven different transgenic mouse models that exhibit a range of Aβ deposit morphologies. We find a surprisingly diverse range of changes in proteome solubility across these models. Mice that deposit human Aβ40 and Aβ42 in cored-neuritic plaques had the most robust changes in proteome solubility. Insoluble cytosolic proteins were also detected in the brains of mice that develop diffuse Aβ42 deposits but to a lesser extent. Notably, mice with cored deposits containing only Aβ42 had relatively few proteins that became detergent-insoluble. Our data provide new insight into the diversity of biological effects that can be attributed to different types of Aβ pathology and support the view that fibrillar cored-neuritic plaque pathology is the more disruptive Aβ pathology in the Alzheimer’s cascade.

Amyloidogenic Peptides in Human Neuro-Degenerative Diseases and in Microorganisms: A Sorrow Shared Is a Sorrow Halved?

The term “amyloid” refers to proteinaceous deposits of peptides that might be generated from larger precursor proteins e.g., by proteolysis. Common to these peptides is a stable cross-β dominated secondary structure which allows self-assembly, leading to insoluble oligomers and lastly to fibrils. These highly ordered protein aggregates have been, for a long time, mainly associated with human neurodegenerative diseases such as Alzheimer’s disease (Amyloid-β peptides). However, they also exert physiological functions such as in release of deposited hormones in human beings. In the light of the rediscovery of our microbial commensals as important companions in health and disease, the fact that microbes also possess amyloidogenic peptides is intriguing. Transmission of amyloids by iatrogenic means or by consumption of contaminated meat from diseased animals is a well-known fact. What if also our microbial commensals might drive human amyloidosis or suffer from our aggregated amyloids? Moreover, as the microbial amyloids are evolutionarily older, we might learn from these organisms how to cope with the sword of Damocles forged of endogenous, potentially toxic peptides. This review summarizes knowledge about the interplay between human amyloids involved in neurodegenerative diseases and microbial amyloids.

Human amyloidosis, still intractable but becoming curable: The essential role of pathological diagnosis in the selection of type-specific therapeutics.

The molecular pathogenesis of human amyloidosis has been elucidated greatly during the last 20 years. Based on the understanding of the molecular mechanisms of amyloid fibril formation and deposition, various kinds of new drugs and therapeutics have been emerging to improve the prognosis of amyloidosis and even cure this disease. In this review article, we first summarize the pathogenesis and state-of-the-art therapeutics of representative types of systemic human amyloidosis, that is, immunoglobulin light chain-related, transthyretin-related, amyloid A-associated and β2 -microglobulin-related amyloidosis. Next, we describe the essential roles of pathological diagnosis, especially the typing diagnosis of amyloidosis to appropriately guide type-specific therapies of amyloidosis patients. Finally, we introduce the activities of the government-funded group for surveys and research of amyloidosis in Japan, especially the nation-wide pathology consultation system of amyloidosis, which started in April 2018. The nation-wide improvement of the typing diagnosis of amyloidosis is essential for the appropriate treatment and care of amyloidosis patients in Japan.

Fibrillar conformation of an apolipoprotein A-I variant involved in amyloidosis and atherosclerosis

BackgroundDifferent protein conformations may be involved in the development of clinical manifestations associated with human amyloidosis. Although a fibrillar conformation is usually the signature of damage in the tissues of patients, it is not clear whether this species is per se the cause or the consequence of the disease. Hereditary amyloidosis due to variants of apolipoprotein A-I (apoA-I) with a substitution of a single amino acid is characterized by the presence of fibrillar protein within the lesions. Thus mutations result in increased protein aggregation. Here we set up to characterize the folding of a natural variant with a mutation leading to a deletion at position 107 (apoA-I Lys107–0). Patients carrying this variant show amyloidosis and severe atherosclerosis. MethodsWe oxidized this variant under controlled concentrations of hydrogen peroxide and analyzed the structure obtained after 30-day incubation by fluorescence, circular dichroism and microscopy approaches. Neutrophils activation was characterized by confocal microscopy. ResultsWe obtained a high yield of well-defined stable fibrillar structures of apoA-I Lys107–0.In an in vitro neutrophils system, we were able to detect the induction of Neutrophils Extracellular Traps (NETs) when we incubated with oxidized apoA-I variants. This effect was exacerbated by the fibrillar structure of oxidized Lys 107–0. ConclusionsWe conclude that a pro-inflammatory microenvironment could result in the formation of aggregation-prone species, which, in addition may induce a positive feed-back in the activation of an inflammatory response. General significanceThese events may explain a close association between amyloidosis due to apoA-I Lys107–0 and atherosclerosis.

2125-P: Increased StAR (Steroidogenic Acute Regulatory Protein) Is Detrimental to ß Cells and Promotes Mitochondrial Dysfunction

StAR is a cholesterol transport protein that transports cholesterol from the cytoplasm into the mitochondrial matrix for further metabolism by CYP enzymes. Depending on the CYP expressed, this results in production of corticosteroids, gonadal steroids, neurosteroids or oxysterols. These products generally exert positive effects on cellular health and function but can also be harmful. We previously showed that StAR is produced in β cells and is increased under conditions of amyloid formation in human islet amyloid polypeptide (hIAPP) transgenic mouse islets, a model of human islet amyloidosis in type 2 diabetes (T2D). Further, CYP11A1, CYP11B1, CYP7A1 and CYP17A1 are not expressed in mouse islets, and CYP27A1 is expressed but decreases with amyloid deposition. Therefore, we hypothesized that increased StAR in islets is deleterious to β-cell health as the downstream CYP enzymes are not present to metabolize mitochondrial cholesterol. We first demonstrated (by immunoblot) that StAR is expressed in human islets, a requirement if it is to play a role in T2D. Also in human islets, only CYP27A1 is detectable, while CYP11A1 and CYP7A1 are not (n=4). We next used a lentivirus to increase StAR expression (or a control lentivirus) in INS-1 cells, which resulted in reduced mitochondrial membrane potential (100±2.0% vs. 78.1±1.2%, n=2, p&amp;lt;0.05) and cell viability (100±4.1% vs. 89.7±7.7%, n=3, p&amp;lt;0.05). Finally, we determined whether reducing StAR expression with an siRNA oligonucleotide in hIAPP transgenic islets had beneficial effects. A 40% knockdown in StAR expression did not alter amyloid deposition, but tended to increase islet viability (100±3.1% vs. 134.7±12.2%, n=2, p=0.1). In summary, StAR is expressed in human islets and increasing its expression is deleterious due to changes in mitochondrial function and β-cell survival. Thus, reducing StAR expression and/or increasing expression of downstream CYP enzymes may be a novel strategy to protect β cells in T2D. Disclosure M.F. Hogan: None. N. Esser: None. A.T. Templin: None. S. Zraika: Research Support; Self; Novartis Pharmaceuticals Corporation. R.L. Hull: Research Support; Self; Boehringer Ingelheim Pharmaceuticals, Inc. S. El-Osta: None. S.E. Kahn: Advisory Panel; Self; Boehringer Ingelheim Pharmaceuticals, Inc., Eli Lilly and Company, Intarcia Therapeutics, Inc., Janssen Pharmaceuticals, Inc., Merck &amp; Co., Inc., Novo Nordisk A/S. Consultant; Self; Neurimmune. Other Relationship; Self; Boehringer Ingelheim Pharmaceuticals, Inc., Merck &amp; Co., Inc., Novo Nordisk A/S. Funding American Diabetes Association (1-18-PDF-174 to M.F.H.); National Institutes of Health (T32HL007028, F32DK109584); U.S. Department of Veterans Affairs (BX001060); University of Washington

A possible connection between plant longevity and the absence of protein fibrillation: basis for identifying aggregation inhibitors in plants

The ability of proteins to aggregate to form well‐organized b‐sheet rich amyloid fibrils is increasingly viewed as a general if regrettable property of the polypeptide chain. Aggregation leads to diseases such as amyloidosis and neurodegeneration in humans and various mammalian species but is also found in a functional variety in both animals and microbes. However, there are to our knowledge no reports of amyloid formation in plants. Plants are also the source of a large number of aggregation‐inhibiting compounds. We reasoned that the two phenomena are connected and that the longer‐lived the plant, the more efficiently it can suppress unwanted protein aggregation. In support of this, we show that while protein extracts from the sugar maple tree A. saccharum fibrillate readily on their own, this process is efficiently abolished by addition of small molecule extracts from the same plant. Further analysis of 44 plants showed a correlation between plant longevity and ability to inhibit protein aggregation. Extracts from the best performing plant, the sugar maple, were subjected to chromatographic fractionation, leading to the identification of a large number of compounds, many of which were shown to inhibit aggregation in vitro. We suggest that plants have been under evolutionary pressure to maintain an efficient collection of aggregation‐inhibiting metabolites; consequently, long‐lived plants may be particularly appropriate sources of new anti‐aggregation compounds with therapeutic potential.Support or Funding InformationD.E.O. was supported by a grant to D.E.O. from The Danish Council for Independent Research | Technology and Production Sciences (grant number: 12–126186), and Parkinson Foreningen (the Danish Parkinson Society). Rothamsted Research receives grant‐aided support from the Biotechnology and Biological Sciences Research Council (BBSRC) of the United Kingdom.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

A Possible Connection Between Plant Longevity and the Absence of Protein Fibrillation: Basis for Identifying Aggregation Inhibitors in Plants.

The ability of proteins to aggregate to form well-organized β-sheet rich amyloid fibrils is increasingly viewed as a general if regrettable property of the polypeptide chain. Aggregation leads to diseases such as amyloidosis and neurodegeneration in humans and various mammalian species but is also found in a functional variety in both animals and microbes. However, there are to our knowledge no reports of amyloid formation in plants. Plants are also the source of a large number of aggregation-inhibiting compounds. We reasoned that the two phenomena could be connected and that one of (many) preconditions for plant longevity is the ability to suppress unwanted protein aggregation. In support of this, we show that while protein extracts from the sugar maple tree Acer saccharum fibrillate readily on their own, this process is efficiently abolished by addition of small molecule extracts from the same plant. Further analysis of 44 plants showed a correlation between plant longevity and ability to inhibit protein aggregation. Extracts from the best performing plant, the sugar maple, were subjected to chromatographic fractionation, leading to the identification of a large number of compounds, many of which were shown to inhibit aggregation in vitro. One cautious interpretation is that it may have been advantageous for plants to maintain an efficient collection of aggregation-inhibiting metabolites as long as they do not impair metabolite function. From a practical perspective, our results indicate that long-lived plants may be particularly appropriate sources of new anti-aggregation compounds with therapeutic potential.