| In recent years, the morbidity of obesity, hyperlipidemia, diabetes and metabolic syndrome increased rapidly because of the changes of people’s dietary structure and living style. A large number of clinical surveys suggest that obesity and other chronic liver diseases are often accompanied with non-alcoholic fatty liver disease(NAFLD), which is a kind of chronic metabolic diseases. The early-stage of NAFLD shows reversible fat deposition and could develop into steatohepatitis, hepatic fibrosis, liver cirrhosis or even liver cancer if no actions were taken timely for treatment. With the increasing of prevalence of some chronic diseases like obesity, the prevalence of NAFLD is increasing and has become a worldwide public health issue. It is very important to prevent the occurrence and development of NAFLD since no effective drug can be used clinically.The “two-hit theory” is increasingly being adopted to explain the pathogenesis of NAFLD and NASH. In this theory, the first hit consists of the accumulation of fatty acids/triglycerides and insulin resistence in the liver, while the second hit involves oxidative stress and inflammation, which ultimately cause liver damage. In previous studies that examined lipid metabolism in the context of NAFLD, dysregulation of cholesterol metabolism has received much less attention than have fatty acids and triglycerides.Phytosterol(PS) and phytosterol ester(PSE) are steroids compounds which are widely existed in some plant origin food, and have quite a lot of physiological functions like cholesterol lowering, antioxidation, anti-inflmmatory etc. Here in this study we hypothesize that PS(PSE) may be effective in the prevention of NAFLD according to previous study and its bioactivities.In the present study, male Sprague Dawley Rats(SD rats) were given high fat diet to establish NAFLD model group(HF group) and different doses of PSE group(low[PSEL], medium[PSEM]and high[PSEH] dosage were 0.05g/100 g BW, 0.10g/100 g BW and 0.15 g/100 g BW, respectively.) were given intragastric administration of PSE and high fat diet. Serum TC, TG, HDL-C, LDL-C, liver function and renal function were determined to observe effects of PSE on serum biochemical indexes; The effects of PSE on liver lipid(TC, TG, FFA) content, liver antioxidant indexes(activity of SOD, GPx, CAT, XOD and MDA) and serum cytokines expression level(TNF-α, TGF-β. IL-6, IL-10, Leptin and adiponectin) were also analyzed; Hematoxylin-eosin staining was applied to observe pathologic changes; Real Time PCR was used to detect the mRNA expression of LXRα, ELOVL and SREBP-1 genes to preliminarily explore the mechanism of protective effects of PSE on NAFLD.The experimental results were as followings:Firstly, serum and liver biochemical indexes showed that low-dose PSE(0.050g/100g'BW) could significantly reduce 13.6% of LDL-C level compared with that of HF group(p<0.05), no further lowering effects were observed at higher dosage group. All doses of PSE had no significant influence on serum TC, TG and HDL-C; TC, TG, FFA content in liver were also decreased in three PSE treatment groups(p<0.05), notably, FFA content was close to normal level in PSEL treated group; Pathology results showed that the degree of hepatic steatosis in NAFLD rats treated with low, medium and high doses of PSE were alleviated and liver function were improved in a certain degree as AST, ALT and ALP enzyme activity decreased in PSE intervention groups, among which the reduction were 10%, 5% and 7%, respectively, in PSEL group. In addition, serum GLU decresed significantly in PSEM and PSEH intervention groups compared with HF group(p<0.05) and were close to the normal level. The results of seserum and liver biochemical indexes indicated that PSE treatment could lower serum LDL-C and liver lipids, lleviate steatosis and improve liver function. More over, PSE could modulate serum GLU which implies that it may ameliorate IR induced by heigh fat diet.Secondly, the results of antioxidant indexes detection showed that activity of SOD increased by 9%,XOD decreased by 17% and MDA content reduced by 19% in PSEL, which suggested that PSE was able to improve oxidative stress status in NAFLD rats. There were no significant differences among three PSE groups.Thirdly, the results of cytokines detection showed that three doses of PSE could decrease the level of serum proinflammatory factors as TGF-β, IL-6 and IL-10.In PSEL group, they were reduced by 35%, 10% and 26%(p <0.05), respectively. Besides, TNF-α was observed decreasing tendency in PSEL group while there were no influence on leptin and adiponectin(p>0.05). Higher dosage of PSE in this experiemtn did not enhance the influence on cytokines. The results of this part suggested that PSE played a role in the occurrence and development of NAFLD and NASH by decreasing concentration of some proinflammatory factors.Finally, mRNA expression levels of genes related with lipid metabolism were analyzed. RT-PCR results showed that low-dose of PSE upregulated expression of LXRα and ELOVL2 compared with HF group and showed no significant influence on the expression of SREBP-1; In PSEM and PSEH group, expression of SREBP-1 was upregulated significantly(p<0.05). The results suggested that on the one hand PSE could prevent the occurrence and development of NAFLD through modulating the expression of genes related with lipid metabolism, on the other hand, different doses of PSE maybe have different target genes but it still need further investigation to explore its specific molecular mechanism.The present study may enrich the biological activity research of PSE and offer the theory data in the treatment of NAFLD clinicaly. |
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