Dyslipidemia in rat fed with high-fat diet is not associated with PCSK9-LDL-receptor pathway but ageing

BACKGROUND Obesity is associated with unfavorable alternations in plasma lipid profile and a broad spectrum of cardio-metabolic disorders. Proprotein convestase subtilisin kexin type 9 (PCSK9) is a novel circulating protein that promotes hypercholesterolemia by decreasing hepatic low lipoprotein density receptor (LDLR) protein. However, the relationship between PCSK9 concentration and lipid profile in an obesity condition has less been investigated. OBJECTIVE To examine the changes of plasma PCSK9 concentration in a rat model fed with high fat diet (HFD) and its correlation to lipid profile, body weight and ageing. METHODS Twenty male Sprague Dawley (SD) rats were divided into two groups, control group (fed with normal pellet for 4 weeks), and high-fat diet group (fed with 3% cholesterol enrich diet for 4 weeks). Blood samples of rats were obtained before and at days 14, 21, and 28 in both groups. The body weight, plasma metabolic parameters (glucose, lipid profile) and PCSK9 were determined at indicated time points. RESULTS The body weights were significantly increased in rats fed with HFD compared to that in rats with normal pellets at day 28. Additionally, total cholesterol (TC), triglyceride (TG), and low density lipoprotein cholesterol (LDL-C) levels in rat fed with HFD were also higher than that in rats fed with control diet while decreased high density lipoprotein cholesterol (HDL-C) levels were found in rats with HFD at day 28. More interesting, there were no differences of plasma PCSK9 concentrations as well as hepatic expression of LDLR between the two groups at day 28. CONCLUSIONS Although the body weight and LDL-C were significantly increased in rats fed with HFD at 4 weeks, there were no differences of changes in plasma PCSK9 concentration and LDLR expression of liver tissue in both groups at baseline and day 28, suggesting that dyslipidemia in the rat model with HFD appears not to be associated with PCSK9-LDLR pathway but ageing.