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Targeted inhibition of calpain reduces myocardial hypertrophy and fibrosis in mouse models of type 1 diabetes.

Li Y, Ma J, Zhu H, Singh M, Hill D, Greer PA, Arnold JM, Abel ED, Peng T - Diabetes (2011)

Bottom Line: Calpain activity, cardiomyocyte cross-sectional areas, and myocardial collagen deposition were significantly increased in both STZ-induced and OVE26 diabetic hearts, and these were accompanied by elevated expression of hypertrophic and fibrotic collagen genes.These effects were associated with a normalization of the nuclear factor of activated T-cell nuclear factor-κB and matrix metalloproteinase (MMP) activities in diabetic hearts.Thus targeted inhibition of calpain represents a potential novel therapeutic strategy for reversing diabetic cardiomyopathy.

View Article: PubMed Central - PubMed

Affiliation: Critical Illness Research, Lawson Health Research Institute, University of Western Ontario, London, Ontario, Canada.

ABSTRACT

Objective: Recently we have shown that calpain-1 activation contributes to cardiomyocyte apoptosis induced by hyperglycemia. This study was undertaken to investigate whether targeted disruption of calpain would reduce myocardial hypertrophy and fibrosis in mouse models of type 1 diabetes.

Research design and methods: Diabetes in mice was induced by injection of streptozotocin (STZ), and OVE26 mice were also used as a type 1 diabetic model. The function of calpain was genetically manipulated by cardiomyocyte-specific knockout Capn4 in mice and the use of calpastatin transgenic mice. Myocardial hypertrophy and fibrosis were investigated 2 and 5 months after STZ injection or in OVE26 diabetic mice at the age of 5 months. Cultured isolated adult mouse cardiac fibroblast cells were also investigated under high glucose conditions.

Results: Calpain activity, cardiomyocyte cross-sectional areas, and myocardial collagen deposition were significantly increased in both STZ-induced and OVE26 diabetic hearts, and these were accompanied by elevated expression of hypertrophic and fibrotic collagen genes. Deficiency of Capn4 or overexpression of calpastatin reduced myocardial hypertrophy and fibrosis in both diabetic models, leading to the improvement of myocardial function. These effects were associated with a normalization of the nuclear factor of activated T-cell nuclear factor-κB and matrix metalloproteinase (MMP) activities in diabetic hearts. In cultured cardiac fibroblasts, high glucose-induced proliferation and MMP activities were prevented by calpain inhibition.

Conclusions: Myocardial hypertrophy and fibrosis in diabetic mice are attenuated by reduction of calpain function. Thus targeted inhibition of calpain represents a potential novel therapeutic strategy for reversing diabetic cardiomyopathy.

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Related in: MedlinePlus

Assessment of cardiac hypertrophy in diabetic Capn4−/− (knockout [KO]) and Tg-CAST mice. Cardiac hypertrophy was determined by measuring cardiomyocyte cross-sectional areas and hypertrophic gene expression (ANP and β-MHC). A–D: Deficiency of Capn4 reduced cardiomyocyte cross-sectional areas (A), the mRNA levels of ANP (B) and β-MHC (C), and caspase-3 activity (D) in diabetic Capn4−/− hearts. E–H: Cardiomyocyte cross-sectional areas (E), the mRNA levels of ANP (F) and β-MHC (G), and caspase-3 activity (H) were decreased in diabetic Tg-CAST hearts. Data are mean ± SD; n = 8. *P < 0.05 vs. sham in wild-type (WT); #P < 0.05 vs. STZ in WT.
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Figure 3: Assessment of cardiac hypertrophy in diabetic Capn4−/− (knockout [KO]) and Tg-CAST mice. Cardiac hypertrophy was determined by measuring cardiomyocyte cross-sectional areas and hypertrophic gene expression (ANP and β-MHC). A–D: Deficiency of Capn4 reduced cardiomyocyte cross-sectional areas (A), the mRNA levels of ANP (B) and β-MHC (C), and caspase-3 activity (D) in diabetic Capn4−/− hearts. E–H: Cardiomyocyte cross-sectional areas (E), the mRNA levels of ANP (F) and β-MHC (G), and caspase-3 activity (H) were decreased in diabetic Tg-CAST hearts. Data are mean ± SD; n = 8. *P < 0.05 vs. sham in wild-type (WT); #P < 0.05 vs. STZ in WT.

Mentions: Capn4−/− and Capn4+/+ mice were rendered diabetic with STZ. Two months after STZ injection, mice exhibited hyperglycemia, hyperphagia, polydipsia, and decreased body weight versus vehicle-treated animals. There were no evident differences in body weight, heart weight, and blood glucose concentration between Capn4−/− and Capn4+/+ diabetic mice (Supplementary Table 1). Consistent with our recent report (25), histological analysis of cardiomyocyte cross-sectional areas in wild-type mice revealed increased cardiomyocyte size in diabetic versus nondiabetic hearts, indicative of cardiomyocyte hypertrophy. However, cardiomyocyte sizes were not increased in diabetic Capn4−/− hearts (Fig. 3A). Furthermore, gene expression measurements of diabetic hearts showed upregulation of both ANP and β-MHC mRNA (Fig. 3B and C), providing further evidence of a hypertrophic phenotype. Although both genes were also upregulated in Capn4−/− diabetic hearts, those increases were significantly reduced relative to wild-type mice (Fig. 3B and C). Interestingly, there were no differences in cardiomyocyte size and hypertrophic gene expression when comparing Capn4−/− and Capn4+/+ nondiabetic hearts (Fig. 3B and C). These results demonstrated that Capn4 knockout prevents myocardial hypertrophy in a mouse model of STZ-induced type 1 diabetes. Deletion of Capn4 also decreased myocardial caspase-3 activity (Fig. 3D) and cytoplasmic histone-associated DNA fragments (Supplementary Fig. 3), suggesting a reduction of apoptosis, which is consistent with our recent report (14). Similarly, 5 months after STZ injection, cardiomyocyte size and hypertrophic gene expression were reduced in Capn4−/− compared with Capn4+/+ hearts (Supplementary Fig. 4A and B), suggesting that the protective effects of Capn4 deletion may be sustained in diabetic cardiomyopathy.


Targeted inhibition of calpain reduces myocardial hypertrophy and fibrosis in mouse models of type 1 diabetes.

Li Y, Ma J, Zhu H, Singh M, Hill D, Greer PA, Arnold JM, Abel ED, Peng T - Diabetes (2011)

Assessment of cardiac hypertrophy in diabetic Capn4−/− (knockout [KO]) and Tg-CAST mice. Cardiac hypertrophy was determined by measuring cardiomyocyte cross-sectional areas and hypertrophic gene expression (ANP and β-MHC). A–D: Deficiency of Capn4 reduced cardiomyocyte cross-sectional areas (A), the mRNA levels of ANP (B) and β-MHC (C), and caspase-3 activity (D) in diabetic Capn4−/− hearts. E–H: Cardiomyocyte cross-sectional areas (E), the mRNA levels of ANP (F) and β-MHC (G), and caspase-3 activity (H) were decreased in diabetic Tg-CAST hearts. Data are mean ± SD; n = 8. *P < 0.05 vs. sham in wild-type (WT); #P < 0.05 vs. STZ in WT.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3198063&req=5

Figure 3: Assessment of cardiac hypertrophy in diabetic Capn4−/− (knockout [KO]) and Tg-CAST mice. Cardiac hypertrophy was determined by measuring cardiomyocyte cross-sectional areas and hypertrophic gene expression (ANP and β-MHC). A–D: Deficiency of Capn4 reduced cardiomyocyte cross-sectional areas (A), the mRNA levels of ANP (B) and β-MHC (C), and caspase-3 activity (D) in diabetic Capn4−/− hearts. E–H: Cardiomyocyte cross-sectional areas (E), the mRNA levels of ANP (F) and β-MHC (G), and caspase-3 activity (H) were decreased in diabetic Tg-CAST hearts. Data are mean ± SD; n = 8. *P < 0.05 vs. sham in wild-type (WT); #P < 0.05 vs. STZ in WT.
Mentions: Capn4−/− and Capn4+/+ mice were rendered diabetic with STZ. Two months after STZ injection, mice exhibited hyperglycemia, hyperphagia, polydipsia, and decreased body weight versus vehicle-treated animals. There were no evident differences in body weight, heart weight, and blood glucose concentration between Capn4−/− and Capn4+/+ diabetic mice (Supplementary Table 1). Consistent with our recent report (25), histological analysis of cardiomyocyte cross-sectional areas in wild-type mice revealed increased cardiomyocyte size in diabetic versus nondiabetic hearts, indicative of cardiomyocyte hypertrophy. However, cardiomyocyte sizes were not increased in diabetic Capn4−/− hearts (Fig. 3A). Furthermore, gene expression measurements of diabetic hearts showed upregulation of both ANP and β-MHC mRNA (Fig. 3B and C), providing further evidence of a hypertrophic phenotype. Although both genes were also upregulated in Capn4−/− diabetic hearts, those increases were significantly reduced relative to wild-type mice (Fig. 3B and C). Interestingly, there were no differences in cardiomyocyte size and hypertrophic gene expression when comparing Capn4−/− and Capn4+/+ nondiabetic hearts (Fig. 3B and C). These results demonstrated that Capn4 knockout prevents myocardial hypertrophy in a mouse model of STZ-induced type 1 diabetes. Deletion of Capn4 also decreased myocardial caspase-3 activity (Fig. 3D) and cytoplasmic histone-associated DNA fragments (Supplementary Fig. 3), suggesting a reduction of apoptosis, which is consistent with our recent report (14). Similarly, 5 months after STZ injection, cardiomyocyte size and hypertrophic gene expression were reduced in Capn4−/− compared with Capn4+/+ hearts (Supplementary Fig. 4A and B), suggesting that the protective effects of Capn4 deletion may be sustained in diabetic cardiomyopathy.

Bottom Line: Calpain activity, cardiomyocyte cross-sectional areas, and myocardial collagen deposition were significantly increased in both STZ-induced and OVE26 diabetic hearts, and these were accompanied by elevated expression of hypertrophic and fibrotic collagen genes.These effects were associated with a normalization of the nuclear factor of activated T-cell nuclear factor-κB and matrix metalloproteinase (MMP) activities in diabetic hearts.Thus targeted inhibition of calpain represents a potential novel therapeutic strategy for reversing diabetic cardiomyopathy.

View Article: PubMed Central - PubMed

Affiliation: Critical Illness Research, Lawson Health Research Institute, University of Western Ontario, London, Ontario, Canada.

ABSTRACT

Objective: Recently we have shown that calpain-1 activation contributes to cardiomyocyte apoptosis induced by hyperglycemia. This study was undertaken to investigate whether targeted disruption of calpain would reduce myocardial hypertrophy and fibrosis in mouse models of type 1 diabetes.

Research design and methods: Diabetes in mice was induced by injection of streptozotocin (STZ), and OVE26 mice were also used as a type 1 diabetic model. The function of calpain was genetically manipulated by cardiomyocyte-specific knockout Capn4 in mice and the use of calpastatin transgenic mice. Myocardial hypertrophy and fibrosis were investigated 2 and 5 months after STZ injection or in OVE26 diabetic mice at the age of 5 months. Cultured isolated adult mouse cardiac fibroblast cells were also investigated under high glucose conditions.

Results: Calpain activity, cardiomyocyte cross-sectional areas, and myocardial collagen deposition were significantly increased in both STZ-induced and OVE26 diabetic hearts, and these were accompanied by elevated expression of hypertrophic and fibrotic collagen genes. Deficiency of Capn4 or overexpression of calpastatin reduced myocardial hypertrophy and fibrosis in both diabetic models, leading to the improvement of myocardial function. These effects were associated with a normalization of the nuclear factor of activated T-cell nuclear factor-κB and matrix metalloproteinase (MMP) activities in diabetic hearts. In cultured cardiac fibroblasts, high glucose-induced proliferation and MMP activities were prevented by calpain inhibition.

Conclusions: Myocardial hypertrophy and fibrosis in diabetic mice are attenuated by reduction of calpain function. Thus targeted inhibition of calpain represents a potential novel therapeutic strategy for reversing diabetic cardiomyopathy.

Show MeSH
Related in: MedlinePlus