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Amyloid-induced ?-cell dysfunction and islet inflammation are ameliorated by 4-phenylbutyrate (PBA) treatment.

ABSTRACT: Human islet amyloid polypeptide (hIAPP) aggregation is associated with ?-cell dysfunction and death in type 2 diabetes (T2D). we aimed to determine whether in vivo treatment with chemical chaperone 4-phenylbutyrate (PBA) ameliorates hIAPP-induced ?-cell dysfunction and islet amyloid formation. Oral administration of PBA in hIAPP transgenic (hIAPP Tg) mice expressing hIAPP in pancreatic ? cells counteracted impaired glucose homeostasis and restored glucose-stimulated insulin secretion. Moreover, PBA treatment almost completely prevented the transcriptomic alterations observed in hIAPP Tg islets, including the induction of genes related to inflammation. PBA also increased ?-cell viability and improved insulin secretion in hIAPP Tg islets cultured under glucolipotoxic conditions. Strikingly, PBA not only prevented but even reversed islet amyloid deposition, pointing to a direct effect of PBA on hIAPP. This was supported by in silico calculations uncovering potential binding sites of PBA to monomeric, dimeric, and pentameric fibrillar structures, and by in vitro assays showing inhibition of hIAPP fibril formation by PBA. Collectively, these results uncover a novel beneficial effect of PBA on glucose homeostasis by restoring ?-cell function and preventing amyloid formation in mice expressing hIAPP in ? cells, highlighting the therapeutic potential of PBA for the treatment of T2D.-Montane, J., de Pablo, S., Castaño, C., Rodríguez-Comas, J., Cadavez, L., Obach, M., Visa, M., Alcarraz-Vizán, G., Sanchez-Martinez, M., Nonell-Canals, A., Parrizas, M., Servitja, J.-M., Novials, A. Amyloid-induced ?-cell dysfunction and islet inflammation are ameliorated by 4-phenylbutyrate (PBA) treatment.

SUBMITTER: Montane J

PROVIDER: S-EPMC5690378 | biostudies-literature | 2017 Dec

REPOSITORIES: biostudies-literature

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Amyloid-induced β-cell dysfunction and islet inflammation are ameliorated by 4-phenylbutyrate (PBA) treatment.

Montane Joel J de Pablo Sara S Castaño Carlos C Rodríguez-Comas Júlia J Cadavez Lisa L Obach Mercè M Visa Montse M Alcarraz-Vizán Gema G Sanchez-Martinez Melchor M Nonell-Canals Alfons A Parrizas Marcelina M Servitja Joan-Marc JM Novials Anna A

FASEB journal : official publication of the Federation of American Societies for Experimental Biology 20170815 12

Human islet amyloid polypeptide (hIAPP) aggregation is associated with β-cell dysfunction and death in type 2 diabetes (T2D). we aimed to determine whether <i>in vivo</i> treatment with chemical chaperone 4-phenylbutyrate (PBA) ameliorates hIAPP-induced β-cell dysfunction and islet amyloid formation. Oral administration of PBA in hIAPP transgenic (hIAPP Tg) mice expressing hIAPP in pancreatic β cells counteracted impaired glucose homeostasis and restored glucose-stimulated insulin secretion. Mor ...[more]

PMID: 28821639

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Project description:ObjectivePancreatic ?-cell failure is central to the development and progression of type 2 diabetes (T2D). The aggregation of human islet amyloid polypeptide (hIAPP) has been associated with pancreatic islet inflammation and dysfunction in T2D. Alpha1-antitrypsin (AAT) is a circulating protease inhibitor with anti-inflammatory properties. Here, we sought to investigate the potential therapeutic effect of AAT treatment in a mouse model characterized by hIAPP overexpression in pancreatic ?-cells.MethodsMice overexpressing hIAPP (hIAPP-Tg) in pancreatic ?-cells were used as a model of amyloid-induced ?-cell dysfunction. Glucose homeostasis was evaluated by glucose tolerance tests and insulin secretion assays. Apoptosis and amyloid formation was assessed in hIAPP-Tg mouse islets cultured at high glucose levels. Dissociated islet cells were cocultured with macrophages obtained from the peritoneal cavity.ResultsNontreated hIAPP-Tg mice were glucose intolerant and exhibited impaired insulin secretion. Interestingly, AAT treatment improved glucose tolerance and restored the insulin secretory response to glucose in hIAPP-Tg mice. Moreover, AAT administration normalized the expression of the essential ?-cell genes MafA and Pdx1, which were downregulated in pancreatic islets from hIAPP-Tg mice. AAT prevented the formation of amyloid deposits and apoptosis in hIAPP-Tg islets cultured at high glucose concentrations. Since islet macrophages mediate hIAPP-induced ?-cell dysfunction, we investigated the effect of AAT in cocultures of macrophages and islet cells. AAT prevented hIAPP-induced ?-cell apoptosis in these cocultures without reducing the hIAPP-induced secretion of IL-1? by macrophages. Remarkably, AAT protected ?-cells against the cytotoxic effects of conditioned medium from hIAPP-treated macrophages. Similarly, AAT also abrogated the cytotoxic effects of exogenous proinflammatory cytokines on pancreatic ?-cells.ConclusionsThese results demonstrate that treatment with AAT improves glucose homeostasis in mice overexpressing hIAPP and protects pancreatic ?-cells from the cytotoxic actions of hIAPP mediated by macrophages. These results support the use of AAT-based therapies to recover pancreatic ?-cell function for the treatment of T2D.

Project description:The prevention or delay of brain senescence would enhance the quality of life for older persons. We investigated the effects of soybean extracts in senescence-accelerated (SAMP10) mice. This mouse is a model of brain senescence with a short life span, cerebral atrophy and cognitive dysfunction. Mice were fed a diet containing soybean extracts from 1 to 12 months of age. The effects of green and yellow soybean extracts were compared with a control diet without soybean extracts. Cognitive functions were higher in aged mice fed green soybean than age-matched control mice and mice fed yellow soybean. We further investigated transcriptome of the SAMP10 hippocampus indicated that expression levels of 36 genes were significantly higher and 19 genes were lower in mice that ingested green soybean than in mice that ingested yellow soybean. Some of the evidences were reconfirmed by real time PCR analysis; the levels of Cdh1 and Ptgds mRNA were significantly higher and that the level of Aplp1 was significantly lower in aged SAMP10 mice fed green soybean than mice ingested yellow soybean and control mice. Additionally, the amount of amyloid beta 40 and 42 was lower in the insoluble fraction of aged SAMP10 mice fed green soybean than control mice and mice fed yellow soybean, although the levels of amyloid beta 40 and 42 in the soluble fraction were not different. Lipocalin-type prostaglandin D2 synthase (L-PGDS) has been proposed as the endogenous amyloid beta - chaperone, suggesting that amyloid aggregation was lower in mice fed green soybean than control mice and mice fed yellow soybean. These results indicate that the intake of green soybean improved cognitive function in aged mice, and suppressed amyloid beta accumulation. Green soybean might help healthy aging of the brain in older persons. The effect of green and yellow soybean extracts on cognitive function in aged SAMP10 mice. Mice were fed a CE-2 diet containing 3.0% soybean extracts taken from both yellow and green soybean species, from 1 to 12 months of age. Total RNA was extracted from the stored hippocampus for DNA microarray analysis.

Project description:Complement inhibitor C4b-binding protein (C4BP) is synthesized in liver and pancreas and composed of 7 identical alpha chains and one unique beta chain. We showed previously that C4BP binds islet amyloid polypeptide (IAPP) and affects fibril formation in vitro. Now we found that polymeric C4BP inhibited lysis of human erythrocytes incubated with monomeric IAPP while no erythrocyte lysis was observed after incubation with preformed IAPP fibrils. In contrast, monomeric alpha chain of C4BP had significantly reduced activity. Further, addition of monomeric IAPP to a rat insulinoma cell line (INS-1) resulted in decreased cell viability, which was restored in the presence of physiological concentrations of C4BP. Accordingly, addition of C4BP rescued the ability of INS-1 cells and isolated rat islets to respond to glucose stimulation with insulin secretion, which was impaired in the presence of IAPP alone. C4BP was internalized together with IAPP into INS-1 cells and therefore we aimed to study its effect on gene expression. Pathway analyses of mRNA expression microarray data indicated that cells exposed to C4BP and IAPP in comparison to IAPP alone increased expression of genes involved in cholesterol synthesis. Depletion of cholesterol through methyl-Î²-cyclodextrin or cholesterol oxidase abolished the protective effect of C4BP on IAPP cytotoxicity of INS-1 cells. Also, inhibition of phosphoinositide 3-kinase but not NF-ÎºB had a similar effect. Taken together, one of the mechanisms by which C4BP protects beta-cells from IAPP cytotoxicity is by enhancing cholesterol synthesis. The INS-1 cells were grown as 5 separate clones for 10 passages before plating in a 12-well plate (Nunc) at 100.000 cells per well and grown in complete RPMI 1640 medium to 70% confluency for approximately 48 h. The cells were then challenged by adding 77 Î¼M monomeric IAPP alone or together with C4BP (0.6 Î¼M). DMSO (1%) used as solvent for IAPP as well as C4BP (0.6 Î¼M) alone were used as controls. RNA was extracted after 10h incubation and analysis carried out using Rat Gene 2.0 array chip (Affymetrix).

Dataset Information

Amyloid-induced ?-cell dysfunction and islet inflammation are ameliorated by 4-phenylbutyrate (PBA) treatment.

Publications

Amyloid-induced β-cell dysfunction and islet inflammation are ameliorated by 4-phenylbutyrate (PBA) treatment.

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