The Effects And Mechanisms Of Zanthoxylum Alkylamides On Sugar And Lipid Metabolism In Rats

With the rapid development of economical level and the changes of life style, the incidence of hyperlipidemia, diabetes and other chronic metabolic disease caused by abnormal lipid and sugar metabolism increased year by year, which are serious threats to human health and life. Thus, regluating lipid and sugar metabolism becomes an important strategy for prevention and treatment of chronic metabolic diseases such as diabetes and hyperlipidemia. However, many of therapic agents produce adverse side effects after long-term use. Thus, safer and more effective components, especially from natural sources, should be developed.Zanthoxylum is widely used as a seasoning spice in our country. Zanthoxylum alkylamides refer to a group of tingling substances and the main active compounds of Zanthoxylum. The alkylamides from Zanthoxylum have shown extensive biological functions, including anti-inflammatory, analgesic, anti-oxidative and anti-platelet aggregation. Previous studies demonstrated that alkylamides extracted from Zanthoxylum act as a transient receptor potential cation channel subfamily V member 1(TRPV1) activator and a cannabinoid receptor 1(CB1) blocker. TRPV1 and CB1 receptors play important roles in lipid metabolism, insulin secretion and glucose homeostasis. However, studies have yet to investigate the effects of Zanthoxylum alkylamides on abnormal sugar and lipid metabolism in hyperlipidemia and diabetic rats, espically the potential mechanisms are still unclear. Thus, the aim of this study was evaluation of the effects and mechanisms of Zanthoxylum alkylamides on sugar and lipid metabolism in rats, which will give scientific supports to the high valuable utilization and healthy consumption for Zanthoxylum.(1) To explore the effect of Zanthoxylum alkylamides on the lipid metabolism in rats fed high diet and its potential mechanisms. Forty male Sprague-Dawley rats were divided randomly and equally into five groups: the normal control group(Control), the model group(MC), the low, medium and high doses of Zanthoxylum alkylamides treated groups(LD, MD and HD). All the animals except that in control group were fed with high fat diet. The rats in LD, MD and HD groups were orally administered with 3, 6, and 9 mg kg-1 bw alkylamides daily for 6 weeks, respectively. Then the plasma and hepatic lipids, bile acids and neutral steroid in feces of the studied rats were determined. The mRNA and protein expression levels involved in lipid metabolism were assessed by real-time PCR and western-bolt.The results demonstrated that the body weight gain, food efficiency, plasma total chestrol, triglycerides, low density lipoprotein-cholesterol level and atherogenic index were significantly increased, and the accumulation of hepatic cholesterol and triglycerides in the MC rats were also markedly increased compared with that of the normal group. However, the Zanthoxylum alkylamides treatment for 6 weeks, the food efficiency and atherogenic index of the rats in LD, MD, HD groups were significantly reduced, the concentration of cholesterol and triglycerides in plasma and liver were also significantly increased. Meanwhile, the histopathological structure of livers showed that hepatic steatosis in Zanthoxylum alkylamides treated groups were reduced, especially Zanthoxylum alkylamides high dose group. The mRNA and protein expressions of hepatic liver X receptor(LXR) and cholesterol 7 alpha-hydroxylase(CYP7A1) were not influenced but the mRNA and protein expressions of hepatic 3-hydroxyl-2-methylglutaryl CoA(HMG-CoA) reductase, sterol regulatory element-binding protein 2(SREBP-2), and ileum bile acid binding protein(IBABP), sodium-dependent bile acids transporter(ASBT) were obviously down-regulated by Zanthoxylum alkylamides. Meanwhile, Zanthoxylum alkylamides significantly up-regulated the expressions of hepatic and ileal TRPV1, and the concentration of total bile acid in the small intestine contents and feces was also increased. These results showed that Zanthoxylum alkylamide could ameliorate abnormal lipid metabolism in rats fed high fat diet, and HD group was much more effective among all groups. The underlying mechanism may be due to down-regulated the expressions of cholesterol synthesis and ileal absorption of bile acids genes, reduce the endogenous cholesterol synthesis and increase the bile acid and neutral sterols excretion.(2) The effects and mechanisms of Zanthoxylum alkylamides on sugar and lipid metabolism in streptozotocin-induced diabetic rats were investigated. Forty male Sprague-Dawley rats were divided randomly into five groups: the normal control group(Control), the model group(diabetic), the low, medium and high doses of Zanthoxylum alkylamides treated groups(diab-LD, diab-MD and diab-HD). Diabetic rats were orally treated with 3, 6, and 9 mg kg-1 bw alkylamides daily for 28 days. As the alkylamides dose increased, the relative weights of the liver and kidney, fasting blood glucose, and fructosamine levels were significantly decreased, the concentration of cholesterol and triglycerides in plasma and liver were also remarkedly reduced. Meanwhile, the alkylamides significantly increased the body weight and improved the oral glucose tolerance of the rats. Likewise, the alkylamides significantly increased the levels of liver and muscle glycogen and plasma insulin. These substances further alleviated the histopathological changes in the livers and pancreas of the diabetic rats. These changes in the paramerers indicated that Zanthoxylum alkylamides could effectively ameliorate the lipid and sugar metabolism disorder in STZ-induced diabetic rats.Western blot and real-time PCR results revealed that the alkylamide treatment significantly decreased the expression levels of the key enzymes(phosphoenolpyruvate caboxykinase and glucose-6-phosphatase) involved in gluconeogenesis and increased glycolysis enzyme(glucokinase) in the liver, and enhanced the expression levels of pancreatic duodenal homeobox-1(PDX-1), glucokinase(GK), and glucose transporter 2(GLUT 2) in the pancreas. In addition, it was also observed that the alkylamides increased TRPV1 and decreased CB1 expressions in the liver and pancreas. Therefore, alkylamides can prevent STZ-induced hyperglycemia by altering the expression levels of the genes related to glucose metabolism and by ameliorating pancreatic dysfunction.(3) To analyze the influence of different doses of Zanthoxylum alkylamides on intestinal structure, gut microbiome composition and its fermentation products in STZ-induced diabetic rats. Forty male Sprague-Dawley rats were assigned randomly into five experimental groups: the normal control group(Control), the model group(diabetic), the low, medium and high doses of Zanthoxylum alkylamides treated groups(diab-LD, diab-MD and diab-HD) for 28 days. Then the weights of cecum tissue, the concentrations of free ammonia and short chain fatty acid, and gut microbiome composition were examined. Meanwhile, histopathological changes in the intestinal tract of the experimental rats were also observed.The results indicated that the weights of cecal tissue, the concentrations of free ammonia, pH and the quantity of harmful bacteria such as Escherichia coli and Enterococcus of cecal content were significantly increased, while the concentrations of short chain fatty acid and the quantity of beneficial bacteria such as Bifidobacteria and Lactic acid bacteria of cecal content were remarkedly reduced in the diabetic rats. These data suggested that diabetes could modify the intestinal microecology, and cause intestinal flora disturbance. However, the adminstration of low and medium doses of Zanthoxylum alkylamides remarkable decreased the concentrations of free ammonia, and inhibited the growth of Escherichia coli and Enterococcus, and significantly increased the concentrations of short chain fatty acid, and promoted the growth of the Bifidobacteria and Lactic acid bacteria of cecal content, and ameliorated intestinal tissue histopathological changes in diabetic rats. But the injury of intestinal mucosa and its cell structural in diabetic rats was caused by high doses of Zanthoxylum alkylamides. In conclusion, low and medium doses of Zanthoxylum alkylamides could effectively regulate the intestinal microecology imbalance. However, the high doses of Zanthoxylum alkylamides causes massive destruction in the intestinal tissues of the diabetic rats.(4) This study aimed to found that whether TRPV1 may mediate body’s sugar metabolism of Zanthoxylum alkylamides. Forty male Sprague-Dawley rats were divided randomly and equally into five groups: the normal control group(CON), the model group(MC), capsazepine treated group(CAPZ), Zanthoxylum alkylamides treated group(ALK), capsazepine and Zanthoxylum alkylamides treated group(CAPZ + ALK) for 28 days. glycogen and blood biochemical parameters, including blood glucose, insulin, fructosamine, oral glucose tolerance, and expressions of genes and proteins related to glucose metabolism and insulin signaling in the liver and pancreas tissues were determined.The results showed that not significant differences were observed in the blood glucose, plasma fructosamine, oral glucose tolerance and hepatic glycogen level between the MC and CAPZ groups. The blood glucose measured in the ALK group showed significantly lower values than those in the MC group. Significant improvements of the oral glucose tolerance as well as plasma insulin and hepatic glycogen were also observed in the ALK group, when compared to the MC group. However, the improving effects of Zanthoxylum alkylamides on sugar metabolism disorder in diabetic rats were markedly inhibited by TRPV1 receptor antagonist capsazepine. In additon, there were significant differences in the levels of mRNA and protein of PEPCK,G6 Pase, GK and CB1 in the livers of the ALK group compared to MC group. Meanwhile, ALK group also exhibited a remarkable increase in the the pancreatic PDX-1, GLUT 2, GK levels and a significant decrease in the expression levels of CB1, but not in the presence of capsazepine. These findings indicated that TRPV1 plays an important role in Zanthoxylum alkylamides regulating the sugar metabolism disorder in diabetic rats, and involved in the regulation of expressions of genes and proteins related to glucose metabolism and insulin secretion in the liver and pancreas.