Cardiac Metallothionein Synthesis in Streptozotocin-Induced Diabetic Mice, and Its Protection against Diabetes-Induced Cardiac Injury

Abstract

Oxidative stress is involved in the pathogenesis of diabetes and its cardiovascular complications. Metallothionein (MT), a stress-response protein, is significantly increased in the liver and kidney of diabetic animals. We examined whether diabetes also induces cardiac MT synthesis through oxidative damage and whether MT overexpression protects the heart from injury. Diabetes was induced in mice by single injection of streptozotocin (STZ), and cardiac MT mRNA and protein levels were measured 2 weeks and 2 months after STZ treatment. Diabetes significantly increased cardiac MT synthesis 2 weeks and 2 months after STZ treatment, with no change in cardiac metals including zinc, copper, and iron. Serum and cardiac vasopeptide endothelin and inflammatory cytokine tumor necrosis factor-␣ were also significantly increased in diabetic hearts, as were the ratio of oxidized to reduced glutathione and the immunohistochemical staining of 3-nitrotyrosine and 4-hydroxynonenal. To explore the biological importance of increased MT synthesis in the heart, MT-overexpressing transgenic mice were treated with STZ and then examined 2 months later. A loss of inotropic reserve, uncovered during ␤-adrenergic stimulation, and the presence of cardiac fibrosis, shown by increased Sirius red staining of collagen, were evident in the wild-type diabetic mice but not in the MT-overexpressing transgenic diabetic mice. These results suggest that diabetes-induced cardiac MT expression likely associates with systemic increases in endothelin-1 and tumor necrosis factor-␣ and the resulting cardiac oxidative stress. Overexpressing cardiac MT significantly protects the heart from diabetes-induced injury.

Sex-dependent hepatic transcripts and metabolites in the development of glucose intolerance and insulin resistance in Zucker diabetic fatty rats

“…Using mZDF rats, angiotensinogen was recently shown to be induced in mesangial cells via ROS/ ERK/JNK pathways (Ohashi et al 2010), and similar mechanisms might be operating in the liver. MT1 is a potent cellular antioxidant that plays important roles in essential trace element homeostasis, metal detoxification and in the protection against various injuries resulting from ROS (Chiaverini & De Ley 2010), including the development of diabetes and its complications (Ohly et al 2000, Cai 2004, Song et al 2005, Ayaz et al 2006, Tang et al 2010. It has also been shown that levels of MT1 are increased in the livers of diabetic rats (Cai et al 2002), which is in agreement with the results obtained in this study.…”

Metallothionein rescues hypoxia-inducible factor-1 transcriptional activity in cardiomyocytes under diabetic conditions

“…STZ-treated mice with whole blood glucose equal to and higher than 250 mg/dl were considered as diabetic. Mice serving as vehicle controls were given the same volume of sodium citrate [13]. Experimental measurements were performed in the control and diabetic mice 2 weeks after STZ treatment.…”

“…We have shown that over-expression of metallothionein (MT) by zinc or through transgenics prevents diabetic cardiomyopathy [12][13][14]. MT is a small protein rich in cysteine content primarily for essential metal homeostasis and heavy metal detoxification.…”

Protective effect of total aralosides of Aralia elata (Miq) Seem (TASAES) against diabetic cardiomyopathy in rats during the early stage, and possible mechanisms

“…Heart tissue sections at 4 μm were used to perform immunohistochemical staining for CTGF based on our previous method (Zhou et al, 2004;Song et al, 2005) with the following specific antibody: goat anti-rat CTGF antibodies (Santa Cruz Biotechnology, Santa Cruz CA). Color was developed by incubating with diaminobenzidine and counterstaining with hematoxylin.…”

“…Controls were obtained by replacing the primary antibody with PBS. Semi-quantitative analysis of the percentage of positive staining area was evaluated by computer imaging analysis system (Image Proplus), as described previously (Zhou et al, 2004;Song et al, 2005).…”