Abstract
BackgroundThe liver-specific glucokinase knockout (gckw/–) mouse experiences long-term hyperglycemia and insulin resistance. This study was designed to evaluate the functional and structural changes in the myocardium of 60 week-old gckw/– mice, and to investigate the effect of rosiglitazone on the myocardium in this model.Methods60 week-old gckw/– mice were randomly divided into 3 groups: gckw/–, gckw/– mice treated with insulin (1 U/kg) and gckw/– mice treated with rosiglitazone (18 mg/kg). Insulin or rosiglitazone treatment was for 4 weeks. Gckw/w litermates were used as controls. Echocardiography, electrocardiogram, biochemical, histopathological, ultrastructural, real time PCR and Western blot studies were performed to examine for structural and functional changes.ResultsLong-term liver-specific gck knockout in mice elicits hyperglycaemia and insulin resistance. Compared to age matched gckw/w mice, 60 week-old gckw/– mice showed decreased LV internal dimension, increased posterior wall thickness, lengthened PR and QRS intervals, up-regulated MLC2 protein expression, decreased SOD activity, increased MDA levels and up-regulated Cyba mRNA. Morphological studies revealed that there was an increase in the amount of PAS and Masson positively stained material, as did the number and proportion of the cell occupied by mitochondria in the gckw/– mice. Western blot analysis revealed that the levels of the insulin receptor, Akt, phosphorylated AMPK beta and phosphorylated ACC were reduced in gckw/– mice. These effects were partly attenuated or ablated by treatment with rosiglitazone.ConclusionsOur results indicate that changes in the myocardium occur in the liver-specific glucokinase knockout mouse and suggest that reduced glucokinase expression in the liver may induce diabetic cardiomyopathy by up regulating NADPH oxidase and down regulating insulin receptor and p-AMPK protein levels. Rosiglitazone treatment may protect against diabetic cardiomyopathy by altering the levels of a set of proteins involved in cardiac damage.
Highlights
The liver-specific glucokinase knockout mouse experiences long-term hyperglycemia and insulin resistance
Diabetic cardiomyopathy (DCM) is defined as structural and functional changes in the myocardium, which are independent of hypertension, chronic artery disease or any other known cardiac diseases, and are caused by metabolic and cellular abnormalities induced by diabetes mellitus (DM)
In the gckw/, treatment with rosiglitazone did not change the fasting glucose and calculated homeostasis model assessment (HOMA)-β-cell levels, but did result in a significant decrease in both the Asterisk (*) refers to statistical significance (P < 0.05) in comparisons with gckw/– mice, while #refers to comparisons with gckw/w mice
Summary
The liver-specific glucokinase knockout (gckw/–) mouse experiences long-term hyperglycemia and insulin resistance. This study was designed to evaluate the functional and structural changes in the myocardium of 60 week-old gckw/– mice, and to investigate the effect of rosiglitazone on the myocardium in this model. Hyperglycemia has been viewed as the pivotal pathogenetic factor for the development of DCM It can cause abnormalities at the cardiac myocyte level, eventually leading to functional and structural abnormalities, including systolic and diastolic dysfunction, as well as cardiac hypertrophy and myocardial fibrosis [3]. In some animal models of DCM, drug treatment, or the effects of genetic mutation often leads to obesity and diabetes. All of these models have limitations and none are a perfect phenocopy of the human condition [9]
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