Biologically active human islet amyloid polypeptide/amylin in transgenic mice

OBJECTIVEAggregation of human amylin/islet amyloid polypeptide (hA/hIAPP) into small soluble β-sheet–containing oligomers is linked to islet β-cell degeneration and the pathogenesis of type 2 diabetes. Here, we used tetracycline, which modifies hA/hIAPP oligomerization, to probe mechanisms whereby hA/hIAPP causes diabetes in hemizygous hA/hIAPP-transgenic mice.RESEARCH DESIGN AND METHODSWe chronically treated hemizygous hA/hIAPP transgenic mice with oral tetracycline to determine its effects on rates of diabetes initiation, progression, and survival.RESULTSHomozygous mice developed severe spontaneous diabetes due to islet β-cell loss. Hemizygous transgenic animals also developed spontaneous diabetes, although severity was less and progression rates slower. Pathogenesis was characterized by initial islet β-cell dysfunction followed by progressive β-cell loss. Islet amyloid was absent from hemizygous animals with early-onset diabetes and correlated positively with longevity. Some long-lived nondiabetic hemizygous animals also had large islet-amyloid areas, showing that amyloid itself was not intrinsically cytotoxic. Administration of tetracycline dose-dependently ameliorated hyperglycemia and polydipsia, delayed rates of diabetes initiation and progression, and increased longevity compared with water-treated controls.CONCLUSIONSThis is the first report to show that treating hA/hIAPP transgenic mice with a modifier of hA/hIAPP misfolding can ameliorate their diabetic phenotype. Fibrillar amyloid was neither necessary nor sufficient to cause diabetes and indeed was positively correlated with longevity therein, whereas early- to mid-stage diabetes was associated with islet β-cell dysfunction followed by β-cell loss. Interventions capable of suppressing misfolding in soluble hA/hIAPP oligomers rather than mature fibrils may have potential for treating or preventing type 2 diabetes.

show abstract

“…Pancreata were excised and snap frozen (liquid nitrogen) and peptides extracted (homogenization, acid/ethanol) (27). …”

Section: Methodsmentioning

confidence: 99%

Tetracycline Treatment Retards the Onset and Slows the Progression of Diabetes in Human Amylin/Islet Amyloid Polypeptide Transgenic Mice

et al. 2009

View full text Add to dashboard Cite

show abstract

“…A useful experimental model to study the amyloidogenic effects of human amylin and variants is the transgenic mouse that expresses human amylin. Eight research groups have reported the results of studies using this model [35,36,37,38,39,40,41,42]. One general theme, i.e., that the amount of secretion of human amylin determines the level of amyloidosis, was reiterated in a recent paper in which amounts of dietary fat [43] induced islet amyloidosis and impaired insulin secretion.…”

Section: Transgenic Mouse Models That Express Human Amylinmentioning

confidence: 99%

Amylin in the Periphery

Wookey

xuereb

Tikellis

et al. 2003

The Scientific World JOURNAL

View full text Add to dashboard Cite

Amylin (islet amyloid polypeptide) is a peptide synthesized principally in the b-cells of the pancreatic islets together with insulin and has actions as a hormone, growth factor, and modifier of behavior. As a hormone, amylin acts to modify gastric motility, renal resorption, and has metabolic actions. It is postulated that the principal function of amylin as a hormone is the activation of physiological processes associated with feeding. As a growth factor, amylin acts on bone cells, renal proximal tubular cells, and islet b-cells. Amylin has important targets in the brain that mediate its actions in the modification of behavior, including thirst and satiety. In man, amylin can form islet amyloid deposits, an event linked to the reduction of b-cell mass and loss of signal-secretion coupling. Recent evidence has defined a new role for monomeric amylin as a growth factor and regulator of b-cell mass that is postulated to be a key factor in pathophysiological processes that result in overt diabetes.

show abstract

“…The latter were extracted overnight in acidified ethanol, lyophilized and prepared for radioimmunoassay (RIA) (18). The DNA content in tissue pellets was measured (19) as a reference for peptide quantification in the tissue extracts.…”

Section: Tissue and Plasma Extractionmentioning

confidence: 99%

“…Tissue extracts were subjected to reversed-phase HPLC on a Nucleosil 100-7C18 column (Machery-Nagel, Dü ren, Germany) as described previously (18). Mean recoveries of synthetic human IAPP and C-pIAPP were 87.5 Ϯ 9.1% (n = 4) and 91.2 Ϯ 2.9% (n = 2) respectively.…”

Section: Reversed-phase High-performance Liquid Chromatographymentioning

confidence: 99%

Islet amyloid polypeptide/amylin messenger RNA and protein expression in human insulinomas in relation to amyloid formation

Hulst¹,

Oosterwijk²,

Born

et al. 1999

European Journal of Endocrinology

View full text Add to dashboard Cite

Objective: Islet amyloid polypeptide (IAPP), also named amylin, is the predominant protein component of amyloid deposits in human islet b cell tumours of the pancreas (insulinomas). IAPP is co-produced with insulin by islet b cells. We investigated IAPP expression in relation to insulin expression and to amyloid formation in eleven insulinomas. Design and methods: RNA and protein extracts were prepared from the same pieces of tumour tissue, and from specimens of two normal human pancreata. IAPP and insulin mRNA and peptide content were quantified using Northern blot analysis and radioimmunoassay (RIA) respectively. Molecular forms of IAPP immunoreactivity were analysed by reversed-phase high-performance liquid chromatography (HPLC). The presence of islet hormones and of amyloid was assessed by (immuno)histochemical staining of paraffin sections. Plasma levels of IAPP and insulin prior to tumour resection were determined by RIA. Results: IAPP and insulin mRNA and peptide content varied widely between the tumour specimens, and there was considerable intratumour heterogeneity of peptide content. HPLC analysis indicated correct proteolytic processing of the IAPP precursor protein. Amyloid deposits were detected only in the three tumours with the highest IAPP content. In contrast to insulin, plasma levels of IAPP were not elevated in the insulinoma patients. Conclusions: The spectrum of hormone production by insulinomas cannot be inferred from only a few tissue sections due to intratumour heterogeneity. Expression of the IAPP and insulin genes is not coupled in insulinomas, which produce properly processed mature IAPP. In addition to IAPP overproduction, additional factors such as intracellular accumulation of IAPP are involved in amyloidogenesis in insulinomas.

show abstract

Biologically active human islet amyloid polypeptide/amylin in transgenic mice

Abstract: This study has shown that correctly processed hIAPP produced in transgenic mouse pancreatic beta cells exhibits full biological activity. The results validate these transgenic mice for the study of (patho)physiological roles of hIAPP in vivo.

Cited by 9 publications

References 27 publications

Tetracycline Treatment Retards the Onset and Slows the Progression of Diabetes in Human Amylin/Islet Amyloid Polypeptide Transgenic Mice

Tetracycline Treatment Retards the Onset and Slows the Progression of Diabetes in Human Amylin/Islet Amyloid Polypeptide Transgenic Mice

Amylin in the Periphery

Islet amyloid polypeptide/amylin messenger RNA and protein expression in human insulinomas in relation to amyloid formation

Contact Info

Product

Resources

About