Impairment of cardiac insulin signaling and myocardial contractile performance in high-cholesterol/fructose-fed rats.
Although insulin resistance is recognized as a potent and prevalent risk factor for coronary heart disease, less is known as to whether insulin resistance causes an altered cardiac phenotype independent of coronary atherosclerosis. In this study, we investigated the relationship between insulin resistance and cardiac contractile dysfunctions by generating a new insulin resistance animal model with rats on high cholesterol-fructose diet. Male Sprague-Dawley rats were given high cholesterol-fructose (HCF) diet for 15 wk; the rats developed insulin resistance syndrome characterized by elevated blood pressure, hyperlipidemia, hyperinsulinemia, impaired glucose tolerance, and insulin resistance. The results show that HCF induced insulin resistance not only in metabolic-response tissues (i.e., liver and muscle) but also in the heart as well. Insulin-stimulated cardiac glucose uptake was significantly reduced after 15 wk of HCF feeding, and cardiac insulin resistance was associated with blunted Akt-mediated insulin signaling along with glucose transporter GLUT4 translocation. Basal fatty acid transporter FATP1 levels were increased in HCF rat hearts. The cardiac performance of the HCF rats exhibited a marked reduction in cardiac output, ejection fraction, stroke volume, and end-diastolic volume. It also showed decreases in left ventricular end-systolic elasticity, whereas the effective arterial elasticity was increased. In addition, the relaxation time constant of left ventricular pressure was prolonged in the HCF group. Overall, these results indicate that insulin resistance reduction of cardiac glucose uptake is associated with defects in insulin signaling. The cardiac metabolic alterations that impair contractile functions may lead to the development of cardiomyopathy.
Deng
Jen-Ying
JY
Department of Life Science, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan.
Huang
Jiung-Pang
JP
Lu
Long-Sheng
LS
Hung
Li-Man
LM
D000818:Animals; D002302:Cardiac Output; D009202:Cardiomyopathies / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D002791:Cholesterol, Dietary; D004040:Dietary Carbohydrates; D004195:Disease Models, Animal; D004548:Elasticity; D050556:Fatty Acid-Binding Proteins / Q000378:metabolism; D005632:Fructose; D005947:Glucose / Q000378:metabolism*; D051275:Glucose Transporter Type 4 / Q000378:metabolism; D007328:Insulin / Q000378:metabolism*; D007333:Insulin Resistance; D008297:Male; D009200:Myocardial Contraction; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D013318:Stroke Volume; D013997:Time Factors; D016277:Ventricular Function, Left; D017725:Ventricular Pressure
D002791:Cholesterol, Dietary; D004040:Dietary Carbohydrates; D050556:Fatty Acid-Binding Proteins; D051275:Glucose Transporter Type 4; D007328:Insulin; C493570:Slc27a1 protein, rat; C495694:Slc2a4 protein, rat; D005632:Fructose; D051057:Proto-Oncogene Proteins c-akt; D005947:Glucose