353 research outputs found
Importance of Aggregated Islet Amyloid Polypeptide for the Progressive Beta-Cell Failure in Type 2 Diabetes and in Transplanted Human Islets
No full textOriginal Publication: Gunilla Westermark and Per Westermark, Importance of Aggregated Islet Amyloid Polypeptide for the Progressive Beta-Cell Failure in Type 2 Diabetes and in Transplanted Human Islets, 2008, EXPERIMENTAL DIABETES RESEARCH, (2008), 528354. http://dx.doi.org/10.1155/2008/528354 Copyright: Authors</p
Transthyretin and Amyloid in the Islets of Langerhans in Type-2 Diabetes
No full textTransthyretin (TTR) is a major amyloid fibril protein in certain systemic forms of amyloidosis. It is a plasma protein, mainly synthesized by the liver but expression occurs also at certain minor locations, including the endocrine cells in the islets of Langerhans. With the use of immunohistochemistry and in situ hybridization, we have studied the distribution of transthyretincontaining cells in islets of Langerhans in type-2 diabetic and nondiabetic individuals. TTR expression was particularly seen in alpha (glucagon) cells. Islets from type-2 diabetic patients had proportionally more transthyretin-reactive islet cells, including beta cells. A weak transthyretin immunoreaction in IAPP-derived amyloid occurred in some specimens. In seeding experiments in vitro, we found that TTR fibrils did not seed IAPP while IAPP fibrils seeded TTR. It is suggested that islet expression of transthyretin may be altered in type-2 diabetes.Original Publication: Gunilla Westermark and Per Westermark, Transthyretin and Amyloid in the Islets of Langerhans in Type-2 Diabetes, 2008, EXPERIMENTAL DIABETES RESEARCH, (2008), 429274. http://dx.doi.org/10.1155/2008/429274 Copyright: Authors</p
Fibrils from designed non-amyloid-related synthetic peptides induce AA-amyloidosis during inflammation in an animal model
No full textBackground: Mouse AA-amyloidosis is a transmissible disease by a prion-like mechanism where amyloid fibrils act by seeding. Synthetic peptides with no amyloid relationship can assemble into amyloid-like fibrils and these may have seeding capacity for amyloid proteins. Principal Findings: Several synthetic peptides, designed for nanotechnology, have been examined for their ability to produce fibrils with Congo red affinity and concomitant green birefringence, affinity for thioflavin S and to accelerate AA-amyloidosis in mice. It is shown that some amphiphilic fibril-forming peptides not only produced Congo red birefringence and showed affinity for thioflavin S, but they also shortened the lag phase for systemic AA-amyloidosis in mice when they were given intravenously at the time of inflammatory induction with silver nitride. Peptides, not forming amyloid-like fibrils, did not have such properties. Conclusions: These observations should caution researchers and those who work with synthetic peptides and their derivatives to be aware of the potential health concerns. © 2009 Westermark et al.Original Publication:P. Westermark, Katarzyna Lundmark and Gunilla Westermark, Fibrils from designed non-amyloid-related synthetic peptides induce AA-amyloidosis during inflammation in an animal model, 2009, PLoS ONE, (4), 6, e6041.http://dx.doi.org/10.1371/journal.pone.000604
Amyloid Deposition in Transplanted Human Pancreatic Islets : A Conceivable Cause of Their Long-Term Failure
No full textFollowing the encouraging report of the Edmonton group, there was a rejuvenation of the islet transplantation field. After that, more pessimistic views spread when long-term results of the clinical outcome were published. A progressive loss of the beta-cell function meant that almost all patients were back on insulin therapy after 5 years. More than 10 years ago, we demonstrated that amyloid deposits rapidly formed in human islets and in mouse islets transgenic for human IAPP when grafted into nude mice. It is, therefore, conceivable to consider amyloid formation as one potential candidate for the long-term failure. The present paper reviews attempts in our laboratories to elucidate the dynamics of and mechanisms behind the formation of amyloid in transplanted islets with special emphasis on the impact of long-term hyperglycemia.Original Publication:Arne Andersson, Sara Bohman, L A Hakan Borg, Johan Paulsson, Sebastian Schultz, Gunilla Westermark and Per Westermark, Amyloid Deposition in Transplanted Human Pancreatic Islets: A Conceivable Cause of Their Long-Term Failure, 2008, EXPERIMENTAL DIABETES RESEARCH, (2008), 562985.http://dx.doi.org/10.1155/2008/562985Copyright: Author
Real-Time Monitoring of Apoptosis by Caspase-3-Like Protease Induced FRET Reduction Triggered by Amyloid Aggregation
No full textAmyloid formation is cytotoxic and can activate the caspase cascade. Here, we monitor caspase-3-like activity as reduction of fluorescence resonance energy transfer (FRET) using the contstruct pFRET2-DEVD containing enhanced cyan fluorescent protin (EYFP) linked by the caspase-3 specific cleavage site residues DEVD. Beta-TC-6 cells were transfected, and the fluoorescence was measured at 440 nm excitation and 535 nm (EYFP) and 480 nm (ECFP) emission wavelength. Cells were incubated with recombinant pro lset Amyloid Polypeptide (rec prolAPP) or the processing metabolites of prolAPP; the N-terminal flanking peptide withIAPP (recN+IAPP); IAPP with the C-terminal flanking peptied (recIAPP+C) and lslet Amyloid Polypeptide (recIAPP). Peptides were added in solubilized from (50 mu M) or as performed amyloid-like fibrils, or as a combination of these. FRET was measured and incubation with a mixture of solubilized peptide and performed fibrils resulted in loss of FRET and apoptosis was determined to occurein cells incubated with recproIAPP (49%), recN+IAPP (46%), recIAPP (72%) and recIAPP+C (59%). These results show that proIAPP and the processing intermediates reside the same cell toxic capacity as IAPP, and they can all have a central role in the reduction of beta-cell number in type 2 diabetes.Original Publication:Johan F Paulsson, Sebastian Schultz, Martin Kohler, Ingo Leibiger, Per-Olof Berggren and Gunilla Westermark, Real-Time Monitoring of Apoptosis by Caspase-3-Like Protease Induced FRET Reduction Triggered by Amyloid Aggregation, 2008, EXPERIMENTAL DIABETES RESEARCH, (2008), 865850.http://dx.doi.org/10.1155/2008/865850Copyright: Author
AA-amyloidosis can be transferred by peripheral blood monocytes
No full textSpongiform encephalopathies have been reported to be transmitted by blood transfusion even prior to the clinical onset. Experimental AA-amyloidosis shows similarities with prion disease and amyloid-containing organ-extracts can prime a recipient for the disease. In this systemic form of amyloidosis N-terminal fragments of the acute-phase reactant apolipoprotein serum amyloid A are the main amyloid protein. Initial amyloid deposits appear in the perifollicular region of the spleen, followed by deposits in the liver. We used the established murine model and induced AA-amyloidosis in NMRI mice by intravenous injections of purified amyloid fibrils ('amyloid enhancing factor') combined with inflammatory challenge (silver nitrate subcutaneously). Blood plasma and peripheral blood monocytes were isolated, sonicated and re-injected into new recipients followed by an inflammatory challenge during a three week period. When the animals were sacrificed presence of amyloid was analyzed in spleen sections after Congo red staining. Our result shows that some of the peripheral blood monocytes, isolated from animals with detectable amyloid, contained amyloid-seed that primed for AA-amyloid. The seeding material seems to have been phagocytosed by the cells since the AA-precursor (SAA1) was found not be expressed by the monocytes. Plasma recovered from mice with AA amyloidosis lacked seeding capacity. Amyloid enhancing activity can reside in monocytes recovered from mice with AA-amyloidosis and in a prion-like way trigger amyloid formation in conjunction with an inflammatory disorder. Human AA-amyloidosis resembles the murine form and every individual is expected to be exposed to conditions that initiate production of the acute-phase reactant. The monocyte-transfer mechanism should be eligible for the human disease and we point out blood transfusion as a putative route for transfer of amyloidosis.Original Publication:Jana Sponarová, Sofia Nyström and Gunilla T Westermark, AA-amyloidosis can be transferred by peripheral blood monocytes, 2008, PloS one, (3), 10, e3308.http://dx.doi.org/10.1371/journal.pone.0003308Licensee: PLo
Efficient amyloid a clearance in the absence of immunoglobulins and complement factors
No full textAmyloid A amyloidosis is a protein misfolding disease characterized by deposition of extracellular aggregates derived from the acute-phase reactant serum amyloid A protein. If untreated, amyloid A amyloidosis leads to irreversible damage of various organs, including the kidneys, liver, and heart. Amyloid A deposits regress upon reduction of serum amyloid A concentration, indicating that the amyloid can be efficiently cleared by natural mechanisms. Clearance was proposed to be mediated by humoral immune responses to amyloid. Here, we report that amyloid clearance in mice lacking complement factors 3 and 4 (C3C4(-/-)) was equally efficient as in wild-type mice (C57BL/6), and was only slightly delayed in agammaglobulinemic mice (J(H-/-)). Hence, antibodies or complement factors are not necessary for natural amyloid clearance, implying the existence of alternative physiological pathways for amyloid removal
Further Evidence for Amyloid Deposition in Clinical Pancreatic Islet Grafts
No full textBackground. The reasons for the long-term complete or partial loss of islet graft function are unknown, but there areobviously other reasons than just pure allogeneic graft rejection. Earlier studies have shown that deposition of isletamyloid polypeptide amyloid in transplanted islets may indicate a mechanism for loss of cells.Materials and Methods. Sections from liver material from four deceased islet-bearing recipients have been scrutinizedfor the presence of amyloid. Clinical data and certain aspects of the islet graft pathology of these patients have beenpublished previously.Result. With this extended histological analysis, we demonstrate the occurrence of amyloid deposits in islets transplantedinto the liver in three of four patients with type 1 diabetes.Conclusion. The finding adds evidence to the assumption that aggregation of islet amyloid polypeptide might be animportant cause of progressing -cell dysfunction in clinically transplanted islets
Drosophila Melanogaster as a Model System for Studies of Islet Amyloid Polypeptide Aggregation
No full textBackground: Recent research supports that aggregation of islet amyloid polypeptide (IAPP) leads to cell death and this makes islet amyloid a plausible cause for the reduction of beta cell mass, demonstrated in patients with type 2 diabetes. IAPP is produced by the beta cells as a prohormone, and proIAPP is processed into IAPP by the prohormone convertases PC1/3 and PC2 in the secretory granules. Little is known about the pathogenesis for islet amyloid and which intracellular mechanisms are involved in amyloidogenesis and induction of cell death. Methodology/Principal Findings: We have established expression of human proIAPP (hproIAPP), human IAPP (hIAPP) and the non-amyloidogenic mouse IAPP (mIAPP) in Drosophila melanogaster, and compared survival of flies with the expression driven to different cell populations. Only flies expressing hproIAPP in neurons driven by the Gal4 driver elavC(155,Gal4) showed a reduction in lifespan whereas neither expression of hIAPP or mIAPP influenced survival. Both hIAPP and hproIAPP expression caused formation of aggregates in CNS and fat body region, and these aggregates were both stained by the dyes Congo red and pFTAA, both known to detect amyloid. Also, the morphology of the highly organized protein granules that developed in the fat body of the head in hIAPP and hproIAPP expressing flies was characterized, and determined to consist of 15.8 nm thick pentagonal rod-like structures. Conclusions/Significance: These findings point to a potential for Drosophila melanogaster to serve as a model system for studies of hproIAPP and hIAPP expression with subsequent aggregation and developed pathology.Original Publication: Sebastian Schultz, Peter Nilsson and Gunilla Torstensdotter Westermark, Drosophila Melanogaster as a Model System for Studies of Islet Amyloid Polypeptide Aggregation, 2011, PLoS ONE, (6), 6. http://dx.doi.org/10.1371/journal.pone.0020221 Copyright: Public Library of Science (PLoS) http://www.plos.org/</p
Reflections on amyloidosis in Papua New Guinea
No full textThe amyloidoses comprise a heterogeneous group of diseases in which 1 out of more than 25 human proteins aggregates into characteristic beta-sheet fibrils with some unique properties. Aggregation is nucleation dependent. Among the known amyloid-forming constituents is the prion protein, well known for its ability to transmit misfolding and disease from one individual to another. There is increasing evidence that other amyloid forms also may be transmissible but only if certain prerequisites are fulfilled. One of these forms is systemic AA-amyloidosis in which an acute-phase reactant, serum AA, is over-expressed and, possibly after cleavage, aggregates into amyloid fibrils, causing disease. In a mouse model, this disorder can easily be transmitted from one animal to another both by intravenous and oral routes. Also, synthetic amyloid-like fibrils made from defined small peptides have this property, indicating a prion-like transmission mechanism. Even some fibrils occurring in the environment can transmit AA-amyloidosis in the murine model. AA-amyloidosis is particularly common in certain areas of Papua New Guinea, probably due to the endemicity of malaria and perhaps genetic predisposition. Now, when kuru is disappearing, more interest should be focused on the potentially lethal systemic AA-amyloidosis.</p
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