Effect of high fat diet with corn oil on PGC-1α and UCP1 gene expression in adipose tissue of Sprague-Dawley rats
Effect of high fat diet with corn oil on PGC-1α and UCP1 gene expression in adipose tissue of Sprague-Dawley rats
Babak Hassankhan,1,*Parichehreh Yaghmaei,2Kazem Parivar,3Azadeh Ebrahim-Habibi,4
1. Department of Biology, Faculty of Basic Sciences, Science and Research Branch, Islamic Azad University, Tehran, Iran 2. Department of Biology, Faculty of Basic Sciences, Science and Research Branch, Islamic Azad University, Tehran, Iran. 3. Department of Biology, Faculty of Basic Sciences, Science and Research Branch, Islamic Azad University, Tehran, Iran 4. Endocrinology and Metabolism Research Center, Tehran University of Medical Sciences, Tehran, Iran.
Introduction: Background and Aim: Excessive dietary fat consumption and composition of fatty acids in diet plays an important role in health and body weight gain. Previous reports suggest that high omega-6 polyunsaturated fatty acids (PUFA) in diet may associate with metabolic syndrome and Non-alcoholic fatty liver disease (NAFLD). A higher amount of n-6 PUFA leads to increase pro-inflammatory cytokines, which contribute towards inflammation and insulin resistance. PGC-1α is a transcriptional coactivator and it plays an important role in the control of cellular energy metabolism. Reduced PGC-1α gene expression in adipose tissue have been associated with obesity and insulin resistance. Expression of PGC-1α was associated with UCP1 upregulation in some adipose tissue. Uncoupling protein 1 (UCP1) is a mitochondrial membran protein in brown adipose tissue (BAT) and it is a chief regulator of energy expenditure in this tissue. In the present study, a high-fat emulsion diet with corn oil (contains high values of omega-6 PUFA) was used to evaluate its effect on obesity, insulin resistance, PGC-1α and UCP1 gene expression in male Sprague-Dawley rats.
Methods: Materials and Methods: Sixteen male rats were divided into normal control group (n=8) and high fat group (n=8). The normal control group received a standard diet. The high fat group received a standard diet and received a high fat emulsion diet containing corn oil by gavage daily for six weeks. After this time, the rats were sacrificed. Blood samples were collected for measurement of biochemical parameters includ serum lipid profile, glucose, insulin, insulin resistance (HOMA-IR), liver enzymes, adiponectin (Adip) and tumor necrosis factor α (TNF-α). Liver tissue was homogenized for measurement of lipid profile and hepatic malondialdehyde (MDA). Liver histological tests with hematoxylin-eosin staining were performed to evaluate fat accumulation in liver tissue. Retroperitoneal adipose tissue was collected for measurement of PGC-1α and UCP1 gene expression by Real-time PCR.
Results: Results: After six weeks, the level of lipid profile, glucose, insulin, insulin resistance (HOMA-IR), TNF-α, in serum and hepatic content of malondialdehyde (MDA), and triglyceride (TG) significantly increased (P<0/05) and serum adiponectin significantly decreased in high fat group compared to the normal control group (P<0/05). Liver sections of high fat group displayed obvious fat droplets and macrovesicular steatosis. The level of PGC-1α and UCP1 gene expression decreased in high fat group compared to the normal control group.
Conclusion: Our results showed that high omega-6 PUFA in diet are associated with reduction of PGC-1α and UCP1 gene expression in retroperitoneal adipose tissue. Reduction of PGC-1α alter adipose tissue metabolism and mey predispose the person to a higher risk of NAFLD. Hence, PGC-1α may be considered as a target for treatment of NAFLD.