Involvement of hepatic peroxisome proliferator-activated receptor α/γ in the therapeutic effect of osthole on high-fat and high-sucrose-induced steatohepatitis in rats.

Our previous studies have indicated that osthole may be a dual agonist of peroxisome proliferator-activated receptor (PPAR) α/γ and decrease the hepatic lipid accumulation. But there has been no report about therapeutic effect on steatohepatitis. In the present study, we investigated the action of osthole and its potential mechanisms. The rats with steatohepatitis induced by orally feeding high-fat and high-sucrose emulsion were given osthole 5-20 mg/kg for 4 weeks. The results showed that after treatment with osthole, the serum alanine aminotransferase, aspartate aminotransferase, total cholesterol, triglyceride (TG), and free fatty acid (FFA) levels, the hepatic TG, FFA, tumor necrosis factor-α, monocyte chemotactic protein-1, interleukin-6, and interleukin-8 contents, and the hepatic weight and liver index were lowered, especially in the osthole 20 mg/kg group. The histological evaluation of liver specimens demonstrated that osthole might improve the hepatic steatosis and inflammation. At the same time, osthole treatment increased the hepatic protein expressions of PPARα/γ and lipoprotein lipase, and decreased the hepatic protein expressions of nuclear factor-κB, sterol regulatory element-binding protein-1c, fatty acid synthase, and diacylglycerol acyltransferase. These findings demonstrate that osthole is effective in treating rat steatohepatitis, and the PPARα/γ may be involved in the osthole-induced modulation of hepatic lipogenic gene expressions and inflammatory cytokine production.

Zhao X ，Xue J ，Wang XL ，Zhang Y ，Deng M ，Xie ML ... -  《-》

PPARα/γ agonists and antagonists differently affect hepatic lipid metabolism, oxidative stress and inflammatory cytokine production in steatohepatitic rats.

Peroxisome proliferator-activated receptor (PPAR) α/γ may control lipid metabolism and inflammatory response by regulating the downstream target genes, and play a crucial role in the process of non-alcoholic steatohepatitis (NASH) formation, but the difference and interaction between PPARα and PPARγ are poorly understood. The rat model with NASH was established by orally feeding high-fat and high-sucrose emulsion for 6weeks. The results shown that after the model rats were simultaneously treated with PPARα/γ agonists, the total cholesterol (TC), triglyceride (TG) and inflammatory cytokine levels in serum and hepatic tissue, the hepatic steatosis and inflammatory cellular infiltration were decreased, and were consistent with the results of hepatic lipogenic gene and nuclear factor (NF)-κB protein expressions. Conversely, these indexes were increased by PPARα/γ antagonist treatment. Compared with the model group, the serum free fatty acid (FFA) level was increased in the PPARα agonist-treated group, decreased in the PPARγ agonist-treated group, and unchanged in the PPARα/γ agonists-treated group. The hepatic FFA level was low in the PPARα/γ agonists-treated groups, but no significant variation in the PPARα/γ antagonists-treated groups. The increments of hepatic reduced glutathione (GSH) and superoxide dismutase (SOD) contents in the PPARα/γ agonists-treated groups were accompanied by decreased hepatic malondialdehyde (MDA) content. These findings demonstrated that PPARα/γ activation might decrease the hepatic lipid accumulation, oxidative stress and inflammatory cytokine production, and PPARγ could counterbalance the adverse effect of PPARα on circulating FFA. It was concluded that the integrative application of PPARα and PPARγ agonists might exert a synergic inhibitory effect on NASH formation through the modulation of PPARα/γ-mediated lipogenic and inflammatory gene expressions.

Zhang Y ，Cui Y ，Wang XL ，Shang X ，Qi ZG ，Xue J ，Zhao X ，Deng M ，Xie ML ... -  《-》

Osthole improves glucose and lipid metabolism via modulation of PPARα/γ-mediated target gene expression in liver, adipose tissue, and skeletal muscle in fatty liver rats.

Qi ZG ，Zhao X ，Zhong W ，Xie ML ... -  《-》

PPARα/γ antagonists reverse the ameliorative effects of osthole on hepatic lipid metabolism and inflammatory response in steatohepatitic rats.

Zhao X ，Wang F ，Zhou R ，Zhu Z ，Xie M ... -  《-》

Osthole ameliorates insulin resistance by increment of adiponectin release in high-fat and high-sucrose-induced fatty liver rats.

The objectives of this study were to determine the effect of osthole on the insulin resistance (IR) in high-fat and high-sucrose-induced fatty liver rats and to investigate its potential mechanisms. The rat model was established by orally feeding high-fat and high-sucrose emulsion by gavage for 9 weeks. The experimental rats were treated with osthole 5 and 10 mg/kg, lipanthyl 30 mg/kg, and rosiglitazone 4 mg/kg after oral high-fat and high-sucrose emulsion for 6 weeks and were sacrificed 4 weeks after administration. The total cholesterol (TC), triglycerides (TG), and free fatty acids (FFA) in serum and hepatic tissue, fasting blood glucose (FBG), fasting serum insulin (FINS), serum adiponectin, and liver weight were measured. The homeostasis model assessment of insulin resistance (HOMA-IR) and coefficient of hepatic weight were calculated. The results showed that after treatment with osthole, the serum levels of TC, TG, and FFA, the contents of TG and FFA in hepatic tissue, and body weight gain were lowered, especially in the osthole 10 mg/kg group (p < 0.05 or p < 0.01). Moreover, the histological evaluation of liver specimens demonstrated that the steatosis and inflammation in liver in osthole-treated groups were improved, especially in the 10 mg/kg group (p < 0.05). Importantly, the levels of FBG, FINS, and HOMA-IR in the osthole 10 mg/kg group were decreased (p < 0.01), while the level of serum adiponectin in the osthole-treated groups, like PPAR α agonist lipanthyl and PPAR γ agonist rosiglitazone, was increased (p < 0.05). These results revealed that osthole could improve the IR induced by high-fat and high-sucrose emulsion in fatty liver rats, and its mechanism might be associated with increment of adiponectin release via activation of PPAR α/ γ pathway.

Qi Z ，Xue J ，Zhang Y ，Wang H ，Xie M ... -  《-》