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Dual Opposing Roles of Metallothionein Overexpression in C57BL/6J Mouse Pancreatic β-Cells.

Chen S, Han J, Liu Y - PLoS ONE (2015)

Bottom Line: The transgenic MT protein was highly expressed in pancreatic islets.The unique gene expression pattern and abnormal protein levels were observed in MT-tg islets.MT overexpression protected β-cells from acute STZ-induced ROS damages at young age, whereas it impaired GSIS and promoted the development of diabetes in adult C57BL/6J mice, and more severe damage was found in males.

View Article: PubMed Central - PubMed

Affiliation: The Research Institute for Children, Children's Hospital at New Orleans, New Orleans, Louisiana, United States of America; Department of Medical Genetics, Zhongshan Medical College, Sun Yat-sen University, Guangzhou, Guangdong Province, People's Republic of China.

ABSTRACT

Background: Growing evidence indicates that oxidative stress (OS), a persistent state of excess amounts of reactive oxygen species (ROS) along with reactive nitrogen species (RNS), plays an important role in insulin resistance, diabetic complications, and dysfunction of pancreatic β-cells. Pancreatic β-cells contain exceptionally low levels of antioxidant enzymes, rendering them susceptible to ROS-induced damage. Induction of antioxidants has been proposed to be a way for protecting β-cells against oxidative stress. Compared to other antioxidants that act against particular β-cell damages, metallothionein (MT) is the most effective in protecting β-cells from several oxidative stressors including nitric oxide, peroxynitrite, hydrogen peroxide, superoxide and streptozotocin (STZ). We hypothesized that MT overexpression in pancreatic β-cells would preserve β-cell function in C57BL/6J mice, an animal model susceptible to high fat diet-induced obesity and type 2 diabetes.

Research design and methods: The pancreatic β-cell specific MT overexpression was transferred to C57BL/6J background by backcrossing. We studied transgenic MT (MT-tg) mice and wild-type (WT) littermates at 8 weeks and 18 weeks of age. Several tests were performed to evaluate the function of islets, including STZ in vivo treatment, intraperitoneal glucose tolerance tests (IPGTT) and plasma insulin levels during IPGTT, pancreatic and islet insulin content measurement, insulin secretion, and islet morphology assessment. Gene expression in islets was performed by quantitative real-time PCR and PCR array analysis. Protein levels in pancreatic sections were evaluated by using immunohistochemistry.

Results: The transgenic MT protein was highly expressed in pancreatic islets. MT-tg overexpression significantly protected mice from acute STZ-induced ROS at 8 weeks of age; unexpectedly, however, MT-tg impaired glucose stimulated insulin secretion (GSIS) and promoted the development of diabetes. Pancreatic β-cell function was significantly impaired, and islet morphology was also abnormal in MT-tg mice, and more severe damage was detected in males. The unique gene expression pattern and abnormal protein levels were observed in MT-tg islets.

Conclusions: MT overexpression protected β-cells from acute STZ-induced ROS damages at young age, whereas it impaired GSIS and promoted the development of diabetes in adult C57BL/6J mice, and more severe damage was found in males.

No MeSH data available.


Related in: MedlinePlus

Islet morphology, size, DNA, protein and insulin contents in 8-week-old MT-tg and WT male mice.(A) represents images of islet under a microscope; (B) quantified islet size; (C) islet DNA, protein and insulin contents. * p < 0.05, ** p < 0.001 vs WT.
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pone.0137583.g005: Islet morphology, size, DNA, protein and insulin contents in 8-week-old MT-tg and WT male mice.(A) represents images of islet under a microscope; (B) quantified islet size; (C) islet DNA, protein and insulin contents. * p < 0.05, ** p < 0.001 vs WT.

Mentions: MT-tg male isolated islets obviously appeared different from their WT littermates. Under a light microscope, isolated islets showed that the size of MT-tg islets was smaller (Fig 5A, right panel), and a lower number of islets were isolated from the MT-tg mice (80–120 in MT-tg vs. 150–200 in control). The average size of islets (islet area) from MT-tg mice was only 59%-73% of those in WT islets (Fig 5B). Islet protein content and insulin content were significant reduced in MT-tg male mice (Fig 5C). The reductions are consistent with the smaller size and lower density in insulin staining of MT-tg mice (Fig 1), indicating that MT overexpression affects not only β-cells function but also islet morphological features and insulin synthesis.


Dual Opposing Roles of Metallothionein Overexpression in C57BL/6J Mouse Pancreatic β-Cells.

Chen S, Han J, Liu Y - PLoS ONE (2015)

Islet morphology, size, DNA, protein and insulin contents in 8-week-old MT-tg and WT male mice.(A) represents images of islet under a microscope; (B) quantified islet size; (C) islet DNA, protein and insulin contents. * p < 0.05, ** p < 0.001 vs WT.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4559390&req=5

pone.0137583.g005: Islet morphology, size, DNA, protein and insulin contents in 8-week-old MT-tg and WT male mice.(A) represents images of islet under a microscope; (B) quantified islet size; (C) islet DNA, protein and insulin contents. * p < 0.05, ** p < 0.001 vs WT.
Mentions: MT-tg male isolated islets obviously appeared different from their WT littermates. Under a light microscope, isolated islets showed that the size of MT-tg islets was smaller (Fig 5A, right panel), and a lower number of islets were isolated from the MT-tg mice (80–120 in MT-tg vs. 150–200 in control). The average size of islets (islet area) from MT-tg mice was only 59%-73% of those in WT islets (Fig 5B). Islet protein content and insulin content were significant reduced in MT-tg male mice (Fig 5C). The reductions are consistent with the smaller size and lower density in insulin staining of MT-tg mice (Fig 1), indicating that MT overexpression affects not only β-cells function but also islet morphological features and insulin synthesis.

Bottom Line: The transgenic MT protein was highly expressed in pancreatic islets.The unique gene expression pattern and abnormal protein levels were observed in MT-tg islets.MT overexpression protected β-cells from acute STZ-induced ROS damages at young age, whereas it impaired GSIS and promoted the development of diabetes in adult C57BL/6J mice, and more severe damage was found in males.

View Article: PubMed Central - PubMed

Affiliation: The Research Institute for Children, Children's Hospital at New Orleans, New Orleans, Louisiana, United States of America; Department of Medical Genetics, Zhongshan Medical College, Sun Yat-sen University, Guangzhou, Guangdong Province, People's Republic of China.

ABSTRACT

Background: Growing evidence indicates that oxidative stress (OS), a persistent state of excess amounts of reactive oxygen species (ROS) along with reactive nitrogen species (RNS), plays an important role in insulin resistance, diabetic complications, and dysfunction of pancreatic β-cells. Pancreatic β-cells contain exceptionally low levels of antioxidant enzymes, rendering them susceptible to ROS-induced damage. Induction of antioxidants has been proposed to be a way for protecting β-cells against oxidative stress. Compared to other antioxidants that act against particular β-cell damages, metallothionein (MT) is the most effective in protecting β-cells from several oxidative stressors including nitric oxide, peroxynitrite, hydrogen peroxide, superoxide and streptozotocin (STZ). We hypothesized that MT overexpression in pancreatic β-cells would preserve β-cell function in C57BL/6J mice, an animal model susceptible to high fat diet-induced obesity and type 2 diabetes.

Research design and methods: The pancreatic β-cell specific MT overexpression was transferred to C57BL/6J background by backcrossing. We studied transgenic MT (MT-tg) mice and wild-type (WT) littermates at 8 weeks and 18 weeks of age. Several tests were performed to evaluate the function of islets, including STZ in vivo treatment, intraperitoneal glucose tolerance tests (IPGTT) and plasma insulin levels during IPGTT, pancreatic and islet insulin content measurement, insulin secretion, and islet morphology assessment. Gene expression in islets was performed by quantitative real-time PCR and PCR array analysis. Protein levels in pancreatic sections were evaluated by using immunohistochemistry.

Results: The transgenic MT protein was highly expressed in pancreatic islets. MT-tg overexpression significantly protected mice from acute STZ-induced ROS at 8 weeks of age; unexpectedly, however, MT-tg impaired glucose stimulated insulin secretion (GSIS) and promoted the development of diabetes. Pancreatic β-cell function was significantly impaired, and islet morphology was also abnormal in MT-tg mice, and more severe damage was detected in males. The unique gene expression pattern and abnormal protein levels were observed in MT-tg islets.

Conclusions: MT overexpression protected β-cells from acute STZ-induced ROS damages at young age, whereas it impaired GSIS and promoted the development of diabetes in adult C57BL/6J mice, and more severe damage was found in males.

No MeSH data available.


Related in: MedlinePlus