Efficacy of fenofibrate for hepatic steatosis in rats after severe burn

Objective To observe the efficacy of fenofibrate for hepatic steatosis in rats after severe burn. Methods Twenty-seven male SD rats were divided into sham injury group, burn group, and burn+ fenofibrate group according to the random number table, with 9 rats in each group. Rats in sham injury group were sham injured on the back by immersing in 37 ℃ warm water for 15 s and then remained without other treatment. Rats in burn group and burn+ fenofibrate group were inflicted with 30% total body surface area full-thickness scald (hereinafter referred to as burn) on the back by immersing in 98 ℃ hot water for 15 s, and then they were intraperitoneally injected with lactated Ringer's solution at post injury hour (PIH) 1. From PIH 24 to post injury day (PID) 8, rats in burn+ fenofibrate group were treated with fenofibrate in the dose of 80 mg·kg^-1·d^-1, while those in burn group were treated with equivalent volume of saline. (1) Three rats of each group were respectively selected on PID 4, 6, and 8 for the collection of inferior vena caval blood samples. Serum content of total cholesterol (TC), triglyceride (TG), free fatty acid (FFA), high density lipoprotein (HDL), and low density lipoprotein (LDL) was determined with fully automatic biochemical analyzer. Body mass of each rat was measured immediately after blood sampling, and then rats were sacrificed to collect liver tissue for weighing wet mass. The ratio of wet mass of liver tissue to body mass (liver index) was calculated. Meanwhile, gross observation of liver was performed. (2) One liver tissue sample was harvested from each rat at each time point to observe histopathologic changes with HE staining. One liver tissue slice of each rat at each time point was collected to evaluate degree of hepatic steatosis, and the number of rats in each group in each grade of hepatic steatosis was recorded. Measurement data were processed with analysis of variance of factorial design and SNK test, and enumeration data were processed with Kruskal-Wallis test and Nemenyi test. Results (1) The content of TC, TG, FFA, and HDL of rats in burn group on PID 4 was obviously different from that in sham injury group (with P values below 0.05). Compared with that in burn group, the content of TC, TG, and FFA of rats was significantly decreased (with P values below 0.05), while the content of HDL of rats was not obviously changed in burn+ fenofibrate group on PID 4 (P>0.05). There were no obvious differences in the content of LDL of rats among 3 groups on PID 4 (with P values above 0.05). The content of TC, TG, and HDL of rats in burn group on PID 6 was obviously different from that in sham injury group (with P values below 0.05). Compared with that in burn group, the content of TC and TG of rats was significantly decreased (with P values below 0.05), while the content of HDL of rats was significantly increased in burn+ fenofibrate group on PID 6 (P<0.05). There were no obvious differences in the content of FFA and LDL of rats among 3 groups on PID 6 (with P values above 0.05). The content of TC and HDL of rats in burn group on PID 8 was obviously different from that in sham injury group (with P values below 0.05). Compared with that in burn group, the content of TC of rats was significantly decreased (P<0.05), while the content of HDL of rats was not obviously changed in burn+ fenofibrate group on PID 8 (P>0.05). There were no obvious differences in content of TG, FFA, and LDL of rats among 3 groups on PID 8 (with P values above 0.05). (2) The texture of liver tissue of rats in burn+ fenofibrate group at each time point was tender and soft, without oil or fat on the section, which was close to the gross condition of liver of rats in sham injury group. Dark yellow plaque scattered on the surface of liver tissue of rats in burn group at each time point with oil and fat on the section, which was especially obvious on PID 6. There was no obvious difference in liver index of rats among 3 groups on PID 4 (F=1.63, P>0.05). On PID 6 and 8, the liver indexes of rats in sham injury group, burn group, and burn+ fenofibrate group were 0.041 6±0.001 6, 0.053 3±0.005 4, and 0.037 0±0.006 9; 0.042 3±0.003 4, 0.062 4±0.000 5, and 0.044 4±0.004 2 respectively. The liver indexes of rats in burn group on PID 6 and 8 were significantly higher than those in the other two groups (with P values below 0.05). There were no obvious differences in the liver indexes of rats between burn+ fenofibrate group and sham injury group on PID 6 and 8 (with P values above 0.05). (3) The liver tissue structure of rats in sham injury group was normal at each time point. Hepatic steatosis of rats in burn group at each time point appeared microvesicular and disperse, which was especially obvious on PID 6. Mild hepatic steatosis was observed in rats of burn+ fenofibrate group on PID 4, and then the structure of liver tissue gradually recovered to normal level from PID 6 on. The degree of hepatic steatosis of rats in sham injury group was 0 grade. One rat in Ⅰ grade, 1 rat in Ⅱ grade, and 7 rats in Ⅲ grade were observed in hepatic steatosis of rats in burn group. Three rats in 0 grade, 4 rats in Ⅰ grade, and 2 rats in Ⅱ grade were observed in hepatic steatosis of rats in burn+ fenofibrate group. The degree of hepatic steatosis of rats in burn group was more severe than that in the other two groups (with χ² values respectively 56.25 and 162.44, P values below 0.05). The degree of hepatic steatosis of rats in burn+ fenofibrate group was more severe than that in sham injury group (χ²=27.51, P<0.05). Conclusions Fenofibrate can ameliorate the dyslipidemia of severely burned rat, and it can alleviate the degree of hepatic steatosis in certain degree.