Résumé
To observe and investigate the effects and mechanisms of the pure total flavonoids from Citrus changshan-huyou(PTFC) on blood lipid metabolism in hyperlipidemic rats. SD rats were fed with high fat diet for 4 weeks to induce hyperlipidemic rats model, meanwhile three dosages (50, 100, 200 mg•kg ⁻¹•d ⁻¹) of PTFC were administrated intragastrically for 4 weeks respectively.After 2 weeks of modeling, their tail blood was taken and serum TC, TG, and HDL-C levels were detected by biochemical method and their body weight was measured. After 4 weeks of modeling, their body weight was measured and liver weight was measured, then the levels of TC, TG, HDL-C, LDL-C, ALT, AST, MDA and SOD in serum were detected to calculate lipid comprehensive index(LDL-C/HDL-C and LDL-C/TC ratios) and atherogenic index(AI); in addition, MDA and SOD levels were detected by biochemical method. The hitopathological changes of the liver tissues were observed by HE staining; the protein expression levels of PPAR-α, Lpl, and Lipc were detected by ELISA; and the mRNA expression levels of PPAR-α in the liver tissue were detected by Real-time PCR. The results showed that gavage administration of the PTFC significantly decreased the body weight, liver weight, liver index, serum ALT and AST activities, the levels of serum TC, TG, LDL-C, LDL-C/HDL-C, AI and increased serum HDL and LDL/TC level. Moreover, the PTFC significantly enhanced SOD activity and decreased the concentration of MDA in serum and liver tissue. Further mechanism investigation indicated that PTFC inhibited serum lipid accumulation by increasing the expressions PPAR-α, Lpl, Lipc protein and PPAR-α mRNA of the liver tissues. PTFC could actively regulate blood lipid metabolism by ameliorating hepatic function, improving the body's antioxidant capacity, lowering levels of oxidative stress, as well as positively regulating the expression levels of PPAR-α, Lpl, Lipc protein and PPAR-α mRNA of the liver tissues in rats.
Résumé
BACKGROUNDS/AIMS: During the acute phase response, cytokines induce marked alterations in lipid metabolism including an increase in serum triglyceride levels and a decrease in hepatic fatty acid oxidation, in bile acid synthesis, and in high-density lipoprotein levels. METHODS: Peroxisome proliferator-activated receptors (PPARs: PPARalpha, beta/delta, and gamma) regulate fatty acid metabolism, glucose homeostasis, cell proliferation, differentiation and inflammation. Proinflammatory profiles including tumor necrosis factor alpha (TNF-alpha), interleukin-1beta (IL-1beta), and interleukin-6 (IL-6) are the important pathological factors in inflammatory responses during the pathological progression of the acute phase response. Lipopolysaccarides (LPS) induced the expression of TNF-alpha, IL-1beta, and IL-6. LPS-induced inflammation decrease the expression of peroxisome proliferator-activated receptor alpha (PPARalpha), PPARbeta/delta, PPARgamma, and coactivators PPARgamma co-activator 1 alpha (PGC-1alpha), PGC-1beta messenger RNA (mRNA) in the liver of Balb/c mouse. In addition, LPS-induced inflammation diminishes the protein level of PPARalpha, PPARbeta/delta, and PPARgamma. Proinflammatory cytokines including TNFalpha, IL-1beta, and IL-6 are the principal reducer of PPARs. However, the knockout mouse model against TNFalpha and IL-6 does not block decrease of PPARs in serum and liver. The mice were pretreated with fenofibrate at 100 mg/kg for 2 days. RESULTS: These treatment protocols increased the amount of PPARs mRNA in the liver. Fenofibrate inhibited LPS-induced TNF-alpha, IL-1beta, and IL-6 production in the serum and liver. Similar results were obtained when human hepatoma HepG2 cells exposed to LPS were co-incubated with fenofibrate. LPS-treated HepG2 cells decreased expression of IkappaB. Moreover, activation of PPARs abrogated LPS-induced degradation of IkappaB, thus suppressing LPS-induced NF-kappaB activities. CONCLUSIONS: Therefore, fenofibrate decreases the expression and secretion of TNF-alpha, IL-1beta, and IL-6 via the NF-kappaB signaling pathway, thus serving as therapeutic targets to attenuate inflammation that is involved in hepatic pathological progression.