Formation of islet amyloid fibrils in beta-secretory granules of transgenic mice expressing human islet amyloid polypeptide/amylin

Yagui, Kazuo; Yamaguchi, Tetsuro; Kanatsuka, Azuma; Shimada, Fumiyuki; Huang, Choug I; Tokuyama, Yoshiharu; Ohsawa, Haruhiko; Yamamura, Ken‐ichi; Miyazaki, Junichi; Mikata, Atsuo; Yoshida, Sho; Makino, Hideichi

doi:10.1530/eje.0.1320487

Cited by 47 publications

(38 citation statements)

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“…5 A versus B). These were comparable to those described previously in a hemizygous transgenic mouse that did not develop diabetes mellitus (8). These intravesicular IAPP aggregates were not present in controls.…”

Section: Resultssupporting

confidence: 89%

“…However, similar intravesicular deposits are reported elsewhere in hemizygous h-IAPP transgenic mice that did not develop diabetes mellitus (8) and these deposits were not related temporally to cell death in the present study. It is therefore unlikely that these intravesicular aggregates of IAPP were responsible for 13-cell death in male transgenic mice.…”

Section: Discussionsupporting

confidence: 92%

“…Overexpression of human IAPP (h-IAPP), but not rat IAPP, in COS cells resulted in intracellular IAPP amyloidosis that was associated with cell death (5). Thus far, hemizygous transgenic mice for h-IAPP have not been reported to develop islet amyloid or diabetes mellitus spontaneously (6)(7)(8). Induction of marked insulin resistance in hemizygous mice transgenic for h-IAPP provokes intra-and extracellular IAPP amyloid formation, which is associated with 13-cell death and hyperglycemia (9).…”

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confidence: 99%

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Spontaneous diabetes mellitus in transgenic mice expressing human islet amyloid polypeptide.

Janson

Soeller

Roche

et al. 1996

Proc. Natl. Acad. Sci. U.S.A.

318

323

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The islet in non-insulin-dependent diabetes mellitus (NIDDM) is characterized by loss of ,B cells and large local deposits of amyloid derived from the 37-amino acid protein, islet amyloid polypeptide (IAPP Non-insulin-dependent diabetes mellitus (NIDDM) is characterized by (3-cell destruction and islet amyloid derived from islet amyloid polypeptide (IAPP) (1, 2). IAPP is a 37-amino acid protein that possesses amyloidogenic properties in species that spontaneously develop NIDDM (humans, monkeys, cats), but is non-amyloidogenic in mice that do not develop NIDDM (3, 4). Overexpression of human IAPP (h-IAPP), but not rat IAPP, in COS cells resulted in intracellular IAPP amyloidosis that was associated with cell death (5). Thus far, hemizygous transgenic mice for h-IAPP have not been reported to develop islet amyloid or diabetes mellitus spontaneously (6-8). Induction of marked insulin resistance in hemizygous mice transgenic for h-IAPP provokes intra-and extracellular IAPP amyloid formation, which is associated with 13-cell death and hyperglycemia (9).Based on these observations, we hypothesized that sufficiently increased rates of h-IAPP expression and synthesis results in intracellular IAPP amyloidosis and (3-cell death, which results in diabetes mellitus (10). To examine this further, we developed a homozygous line of mice transgenic for h-IAPP, thereby doubling the h-IAPP gene copy number. We report here that these mice spontaneously developed diabetes mellitus due to (3-cell death, which was associated with abnormal intra-and extracellular aggregates of h-IAPP. We conclude that overproduction of IAPP in vulnerable species (humans, monkeys, cats) may cause (3-cell destruction and diabetes mellitus. MATERIALS AND METHODSPreparation of Transgenic Construct. The RIPHAT transgene (2395 bp) is described elsewhere (9). It consists of a PCR-generated cDNA encompassing the h-IAPP coding sequence (270 bp) under the regulation of the rat insulin II promoter/5' untranslated region and followed by intron I (728 bp) from the human albumin gene and the polyadenylylation site/RNA termination region (525 bp) from the human glyceraldehyde-3-phosphate gene (GAPDH). Use of the albumin intron I and GAPDH polyadenylylation site in transgenic constructs has been described (11).Generation of Transgenic Mice. Hemizygotes of the RHF line described in Couce et al. (9) were self-crossed to generate Fl offspring. Transgenic offspring were identified by PCR amplification of RIPHAT from tail DNA. Hemizygotes were distinguished from homozygotes by backcross breeding to nontransgenic FVB/N mice. Homozygotes were defined as those mice that generated more than 20 transgenic and no nontransgenic offspring. Four such homozygotes were used to establish the core RHF breeding colony.Northern Blot Analysis. Total RNA was prepared from whole pancreata of FVB/N, RHF hemizygote, and RHF homozygote males and females. Gels and blots were prepared and hybridized as described (9)

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Section: Resultssupporting

confidence: 89%

Section: Discussionsupporting

confidence: 92%

mentioning

confidence: 99%

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Spontaneous diabetes mellitus in transgenic mice expressing human islet amyloid polypeptide.

Janson

Soeller

Roche

et al. 1996

Proc. Natl. Acad. Sci. U.S.A.

318

323

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“…Immunoreactivity for proIAPP fragments has been detected in some amyloid deposits [29] and it has been suggested that there is an increase in pro-IAPP intermediates in cultured human islets [30]; proIAPP fibrils either inside or outside the cells could act as an initiator for conversion of IAPP to beta conformation and fibril formation. The IAPPimmunoreactive material in beta-cell granules of TM has been described as fibrils [8,31]; if this represents some form of insoluble IAPP or proIAPP accumulation, this could act as a nidus for fibril formation [32] at the surface of the cell when the granule is released.…”

Section: Discussionmentioning

confidence: 99%

Amyloid fibril formation is progressive and correlates with beta-cell secretion in transgenic mouse isolated islets

et al. 1999

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Amyloid deposits are found in the islets of Langerhans of up to 96 % of patients with Type II (non-insulin-dependent) diabetes mellitus [1,2] but the relation of islet amyloid to the syndrome of diabetes is not clear. Amyloid deposition precedes the onset of hyperglycaemia in cats and monkeys [3,4] suggesting a primary aetiological role of amyloid in these species. The severity of islet amyloidosis in diabetic patients at autopsy is, however, greatest in those who have progressed from sulphonylurea to insulin treatment [5] and the degree of amyloid deposition is associated with a decrease of beta-cell function in monkeys [4] implicating islet amyloid in islet dysfunction in the later stages of the disease. An increased incidence of amyloid deposition in vivo in some strains Diabetologia (1999) Abstract Aims/hypothesis. Amyloid fibrils are formed in islets isolated from transgenic mice expressing the gene for human islet amyloid polypeptide (IAPP) by an unknown mechanism. This model of islet amyloidosis in Type II (non-insulin-dependent) diabetes mellitus has been used to investigate the temporal and glucose dependency of fibril formation. Methods. To determine the time course and nature of amyloid-like accumulations and the role of glucose, transgenic mouse islets were cultured for 2±12 days in medium containing glucose (4.2 mmol/l, 11.1 mmol/l or 16.7 mmol/l) or 3.3 mmol/l glucose plus non-glucose secretagogues, 10 mmol/l leucine, 10 mmol/l leucine + 0.1 mmol/l tolbutamide, 10 mmol/l alpha-ketoisocaproic acid + 10 mmol/l glutamine. The extent of fibril formation was determined by quantitative immuno-electron microscopy. Insulin and islet amyloid polypeptide secretion into the media was measured by radioimmunoassay. Results. Extracellular amyloid fibrils immunoreactive for islet amyloid polypeptide were visible initially after 6 days of culture in 11.1 mmol/l glucose and formed 2.3 ± 0.8 % of the islet area after 12 days; small accumulations of intracellular fibrils and amorphous extracellular islet amyloid polypeptide-immunoreactive material were present at 6±12 days. Beta-cell secretion was increased significantly by 16.7 mmol/l glucose and by alpha-ketoisocaproic acid + glutamine. The proportion of fibrillar amyloid (amyloid area/islet area%) correlated with the amount of insulin (r = 0.55, p < 0.05) and IAPP (r = 0.5, p < 0.05) in the culture media. Evidence of cellular damage was present in less than 10 % cells and correlated with the degree of fibril deposition (r = 0.8, p < 0.0001). Conclusion/interpretation. These data suggest that islet amyloid polypeptide amyloid is formed primarily at extracellular sites in isolated transgenic mouse islets and progressive fibril formation correlates with beta-cell secretion. [Diabetologia (1999[Diabetologia ( ) 42: 1219± 1227

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“…To study factors that may be important in islet amyloid formation, we and others have generated transgenic mice expressing human IAPP (hIAPP) in their islet ␤-cells (15)(16)(17)(18)(19). Islet amyloid deposition was observed in the vast majority of our hIAPP transgenic mice when maintained on a breeder chow (20) but not regular chow (17).…”

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confidence: 99%

Increased Dietary Fat Promotes Islet Amyloid Formation and β-Cell Secretory Dysfunction in a Transgenic Mouse Model of Islet Amyloid

et al. 2003

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Transgenic mice expressing the amyloidogenic human islet amyloid polypeptide (hIAPP) in their islet ␤-cells are a model of islet amyloid formation as it occurs in type 2 diabetes. Our hIAPP transgenic mice developed islet amyloid when fed a breeder chow but not regular chow. Because the breeder chow contained increased amounts of fat, we hypothesized that increased dietary fat enhances islet amyloid formation. To test this hypothesis, we fed male hIAPP transgenic and nontransgenic control mice diets containing 15% (low fat), 30% (medium fat), or 45% (high fat) of calories derived from fat for 12 months, and we measured islet amyloid, islet endocrine cell composition, and ␤-cell function. Increased dietary fat in hIAPP transgenic mice was associated with a dose-dependent increase in both the prevalence (percentage of islets containing amyloid deposits; 34 ؎ 8, 45 ؎ 8, and 58 ؎ 10%, P < 0.05) and severity (percentage of islet area occupied by amyloid; 0.8 ؎ 0.5, 1.0 ؎ 0.5, and 4.6 ؎ 2.5%, P ‫؍‬ 0.05) of islet amyloid. In addition, in these hIAPP transgenic mice, there was a dose-dependent decrease in the proportion of islet area comprising ␤-cells, with no significant change in islet size. In contrast, nontransgenic mice adapted to diet-induced obesity by increasing their islet size more than twofold. Increased dietary fat was associated with impaired insulin secretion in hIAPP transgenic (P ‫؍‬ 0.05) but not nontransgenic mice. In summary, dietary fat enhances both the prevalence and severity of islet amyloid and leads to ␤-cell loss and impaired insulin secretion. Because both morphologic and functional defects are present in hIAPP transgenic mice, this would suggest that the effect of dietary fat to enhance islet amyloid formation might play a role in the pathogenesis of the islet lesion of type 2 diabetes in humans. Diabetes 52:372-379, 2003 T ype 2 diabetes is characterized by ␤-cell dysfunction and insulin resistance. An underlying defect in the islet ␤-cell is thought to contribute to the inability of the ␤-cell to compensate for the increased demand for insulin, leading to decreased glucose tolerance and eventually type 2 diabetes. The cause(s) of this ␤-cell dysfunction is unknown and is likely associated with both genetic and environmental factors. One of these environmental factors appears to be increased dietary fat, which has been associated with obesity, insulin resistance, and type 2 diabetes in humans (1-3), and in animal studies it leads to the development of insulin resistance (4,5). In addition to the ␤-cell secretory defect, islet amyloid deposition occurs in the pancreatic islets of the vast majority of subjects with type 2 diabetes (6,7). Islet amyloid has been shown to lead to a progressive loss of ␤-cell mass and function (8 -11), and thus it has been proposed as a factor contributing toward the ␤-cell secretory defect in type 2 diabetes. The unique protein component of islet amyloid is the 37-amino acid peptide islet amyloid polypeptide (IAPP, also known as amylin) (12,13), a normal secret...

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Formation of islet amyloid fibrils in beta-secretory granules of transgenic mice expressing human islet amyloid polypeptide/amylin

Cited by 47 publications

References 35 publications

Spontaneous diabetes mellitus in transgenic mice expressing human islet amyloid polypeptide.

Spontaneous diabetes mellitus in transgenic mice expressing human islet amyloid polypeptide.

Amyloid fibril formation is progressive and correlates with beta-cell secretion in transgenic mouse isolated islets

Increased Dietary Fat Promotes Islet Amyloid Formation and β-Cell Secretory Dysfunction in a Transgenic Mouse Model of Islet Amyloid

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