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Spontaneous diabetes in hemizygous human amylin transgenic mice that developed neither islet amyloid nor peripheral insulin resistance.

Wong WP, Scott DW, Chuang CL, Zhang S, Liu H, Ferreira A, Saafi EL, Choong YS, Cooper GJ - Diabetes (2008)

Bottom Line: Glucose tolerance was impaired during the mid- and end-diabetic phases, in which progressive beta-cell loss paralleled decreasing pancreatic and plasma insulin and amylin.Peripheral insulin resistance was absent because glucose uptake rates were equivalent in isolated soleus muscles from transgenic and control animals.These findings are consistent with beta-cell death evoked by misfolded but soluble cytotoxic species, such as those formed by human amylin in vitro.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, Faculty of Science, University of Auckland, Auckland, New Zealand.

ABSTRACT

Objectives: We sought to 1) Determine whether soluble-misfolded amylin or insoluble-fibrillar amylin may cause or result from diabetes in human amylin transgenic mice and 2) determine the role, if any, that insulin resistance might play in these processes.

Research design and methods: We characterized the phenotypes of independent transgenic mouse lines that display pancreas-specific expression of human amylin or a nonaggregating homolog, [(25,28,29)Pro]human amylin, in an FVB/n background.

Results: Diabetes occurred in hemizygous human amylin transgenic mice from 6 weeks after birth. Glucose tolerance was impaired during the mid- and end-diabetic phases, in which progressive beta-cell loss paralleled decreasing pancreatic and plasma insulin and amylin. Peripheral insulin resistance was absent because glucose uptake rates were equivalent in isolated soleus muscles from transgenic and control animals. Even in advanced diabetes, islets lacked amyloid deposits. In islets from nontransgenic mice, glucagon and somatostatin cells were present mainly at the periphery and insulin cells were mainly in the core; in contrast, all three cell types were distributed throughout the islet in transgenic animals. [(25,28,29)Pro]human amylin transgenic mice developed neither beta-cell degeneration nor glucose intolerance.

Conclusions: Overexpression of fibrillogenic human amylin in these human amylin transgenic mice caused beta-cell degeneration and diabetes through mechanisms independent from both peripheral insulin resistance and islet amyloid. These findings are consistent with beta-cell death evoked by misfolded but soluble cytotoxic species, such as those formed by human amylin in vitro.

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Light and electron microscopic analysis of structure and immunofluorescence study of apoptosis were performed in islets from representative nontransgenic (NTG) and human amylin transgenic (TG) mice. Congo red–stained section imaged under polarized light of representative islets from nontransgenic (A, C, and E) and transgenic (B, D, and F) mice at pre-diabetic (A and B), mid-diabetic (C and D), and late-diabetic (E, F) stages. Birefringence is collagenous. Magnification ×400. TEM images of islets from end-stage nontransgenic (G) and human amylin transgenic (H) mice. G: Normal β-cell insulin secretory granules with hallmark dense cores and surrounding halos (arrowed), healthy nucleus (N), and surrounding exocrine acini (Ea). H: Section from end-stage diabetic human amylin transgenic mouse showing characteristic absence of insulin secretory granules and margination of chromatin with invagination of the nuclear membrane typical of apoptosis and surrounding exocrine acini. Ea, endocrine acini; N, nucleus. Scale bars = 2 μm. Immunofluorescence staining for cleaved caspase-3 in nondiabetic nontransgenic mice (I) and mid-diabetic transgenic mice (J). K: Quantitative measurement of islet cell apoptosis by numeric counts of cleaved caspase-3–positive cells. Results are expressed as fold increase of apoptotic cells in transgenic mice compared with nontransgenic mice, whose numbers were set at unity. ***P < 0.001 vs. nontransgenic. (Please see http://dx.doi.org/10.2337/db06-1755 for a high-quality digital representation of this figure.)
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f5: Light and electron microscopic analysis of structure and immunofluorescence study of apoptosis were performed in islets from representative nontransgenic (NTG) and human amylin transgenic (TG) mice. Congo red–stained section imaged under polarized light of representative islets from nontransgenic (A, C, and E) and transgenic (B, D, and F) mice at pre-diabetic (A and B), mid-diabetic (C and D), and late-diabetic (E, F) stages. Birefringence is collagenous. Magnification ×400. TEM images of islets from end-stage nontransgenic (G) and human amylin transgenic (H) mice. G: Normal β-cell insulin secretory granules with hallmark dense cores and surrounding halos (arrowed), healthy nucleus (N), and surrounding exocrine acini (Ea). H: Section from end-stage diabetic human amylin transgenic mouse showing characteristic absence of insulin secretory granules and margination of chromatin with invagination of the nuclear membrane typical of apoptosis and surrounding exocrine acini. Ea, endocrine acini; N, nucleus. Scale bars = 2 μm. Immunofluorescence staining for cleaved caspase-3 in nondiabetic nontransgenic mice (I) and mid-diabetic transgenic mice (J). K: Quantitative measurement of islet cell apoptosis by numeric counts of cleaved caspase-3–positive cells. Results are expressed as fold increase of apoptotic cells in transgenic mice compared with nontransgenic mice, whose numbers were set at unity. ***P < 0.001 vs. nontransgenic. (Please see http://dx.doi.org/10.2337/db06-1755 for a high-quality digital representation of this figure.)

Mentions: Immuno-labelling of α-, β-, and δ-cells at the end-diabetic stage showed markedly decreased β-cell numbers in transgenic islets, consistent with decreased numbers of functional β-cells and decreased insulin production in these animals (Fig. 3F). Electron microscopic studies, in which at least 30 islets were examined from each animal, further confirmed the presence of typical β-cell secretory granules in nondiabetic islets (Fig. 5G) that, by contrast, were largely lacking in those β-cells (defined as endocrine cells present in the body of the pancreas but lacking typical α- or δ-cell granules) remaining in the body of the pancreas in human amylin transgenic mice at the end stage (Fig. 5H).


Spontaneous diabetes in hemizygous human amylin transgenic mice that developed neither islet amyloid nor peripheral insulin resistance.

Wong WP, Scott DW, Chuang CL, Zhang S, Liu H, Ferreira A, Saafi EL, Choong YS, Cooper GJ - Diabetes (2008)

Light and electron microscopic analysis of structure and immunofluorescence study of apoptosis were performed in islets from representative nontransgenic (NTG) and human amylin transgenic (TG) mice. Congo red–stained section imaged under polarized light of representative islets from nontransgenic (A, C, and E) and transgenic (B, D, and F) mice at pre-diabetic (A and B), mid-diabetic (C and D), and late-diabetic (E, F) stages. Birefringence is collagenous. Magnification ×400. TEM images of islets from end-stage nontransgenic (G) and human amylin transgenic (H) mice. G: Normal β-cell insulin secretory granules with hallmark dense cores and surrounding halos (arrowed), healthy nucleus (N), and surrounding exocrine acini (Ea). H: Section from end-stage diabetic human amylin transgenic mouse showing characteristic absence of insulin secretory granules and margination of chromatin with invagination of the nuclear membrane typical of apoptosis and surrounding exocrine acini. Ea, endocrine acini; N, nucleus. Scale bars = 2 μm. Immunofluorescence staining for cleaved caspase-3 in nondiabetic nontransgenic mice (I) and mid-diabetic transgenic mice (J). K: Quantitative measurement of islet cell apoptosis by numeric counts of cleaved caspase-3–positive cells. Results are expressed as fold increase of apoptotic cells in transgenic mice compared with nontransgenic mice, whose numbers were set at unity. ***P < 0.001 vs. nontransgenic. (Please see http://dx.doi.org/10.2337/db06-1755 for a high-quality digital representation of this figure.)
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2551684&req=5

f5: Light and electron microscopic analysis of structure and immunofluorescence study of apoptosis were performed in islets from representative nontransgenic (NTG) and human amylin transgenic (TG) mice. Congo red–stained section imaged under polarized light of representative islets from nontransgenic (A, C, and E) and transgenic (B, D, and F) mice at pre-diabetic (A and B), mid-diabetic (C and D), and late-diabetic (E, F) stages. Birefringence is collagenous. Magnification ×400. TEM images of islets from end-stage nontransgenic (G) and human amylin transgenic (H) mice. G: Normal β-cell insulin secretory granules with hallmark dense cores and surrounding halos (arrowed), healthy nucleus (N), and surrounding exocrine acini (Ea). H: Section from end-stage diabetic human amylin transgenic mouse showing characteristic absence of insulin secretory granules and margination of chromatin with invagination of the nuclear membrane typical of apoptosis and surrounding exocrine acini. Ea, endocrine acini; N, nucleus. Scale bars = 2 μm. Immunofluorescence staining for cleaved caspase-3 in nondiabetic nontransgenic mice (I) and mid-diabetic transgenic mice (J). K: Quantitative measurement of islet cell apoptosis by numeric counts of cleaved caspase-3–positive cells. Results are expressed as fold increase of apoptotic cells in transgenic mice compared with nontransgenic mice, whose numbers were set at unity. ***P < 0.001 vs. nontransgenic. (Please see http://dx.doi.org/10.2337/db06-1755 for a high-quality digital representation of this figure.)
Mentions: Immuno-labelling of α-, β-, and δ-cells at the end-diabetic stage showed markedly decreased β-cell numbers in transgenic islets, consistent with decreased numbers of functional β-cells and decreased insulin production in these animals (Fig. 3F). Electron microscopic studies, in which at least 30 islets were examined from each animal, further confirmed the presence of typical β-cell secretory granules in nondiabetic islets (Fig. 5G) that, by contrast, were largely lacking in those β-cells (defined as endocrine cells present in the body of the pancreas but lacking typical α- or δ-cell granules) remaining in the body of the pancreas in human amylin transgenic mice at the end stage (Fig. 5H).

Bottom Line: Glucose tolerance was impaired during the mid- and end-diabetic phases, in which progressive beta-cell loss paralleled decreasing pancreatic and plasma insulin and amylin.Peripheral insulin resistance was absent because glucose uptake rates were equivalent in isolated soleus muscles from transgenic and control animals.These findings are consistent with beta-cell death evoked by misfolded but soluble cytotoxic species, such as those formed by human amylin in vitro.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, Faculty of Science, University of Auckland, Auckland, New Zealand.

ABSTRACT

Objectives: We sought to 1) Determine whether soluble-misfolded amylin or insoluble-fibrillar amylin may cause or result from diabetes in human amylin transgenic mice and 2) determine the role, if any, that insulin resistance might play in these processes.

Research design and methods: We characterized the phenotypes of independent transgenic mouse lines that display pancreas-specific expression of human amylin or a nonaggregating homolog, [(25,28,29)Pro]human amylin, in an FVB/n background.

Results: Diabetes occurred in hemizygous human amylin transgenic mice from 6 weeks after birth. Glucose tolerance was impaired during the mid- and end-diabetic phases, in which progressive beta-cell loss paralleled decreasing pancreatic and plasma insulin and amylin. Peripheral insulin resistance was absent because glucose uptake rates were equivalent in isolated soleus muscles from transgenic and control animals. Even in advanced diabetes, islets lacked amyloid deposits. In islets from nontransgenic mice, glucagon and somatostatin cells were present mainly at the periphery and insulin cells were mainly in the core; in contrast, all three cell types were distributed throughout the islet in transgenic animals. [(25,28,29)Pro]human amylin transgenic mice developed neither beta-cell degeneration nor glucose intolerance.

Conclusions: Overexpression of fibrillogenic human amylin in these human amylin transgenic mice caused beta-cell degeneration and diabetes through mechanisms independent from both peripheral insulin resistance and islet amyloid. These findings are consistent with beta-cell death evoked by misfolded but soluble cytotoxic species, such as those formed by human amylin in vitro.

Show MeSH
Related in: MedlinePlus