小檗碱对2型糖尿病大鼠视网膜PPARα/δ/γ表达的影响

糖尿病视网膜病是最常见的糖尿病并发症之一，是导致失明的主要原因，因此有必要寻找新的治疗药物。给大鼠腹腔注射链脲菌素(35 mg·kg^-1) 2周后用高糖高脂饲料喂养14周，之后连续16周每天分别拌食给予小檗碱75、150及300 mg·kg^-1、非诺贝特100 mg·kg^-1和罗格列酮4 mg·kg^-1。用HE染色检查视网膜结构和免疫组化检测过氧化物酶体增殖物激活受体(PPARs) α/δ/γ的表达。结果发现，正常对照组大鼠的视网膜厚度大于其他各组，经小檗碱(150及300 mg·kg^-1)和罗格列酮(4 mg·kg^-1)的治疗能增加糖尿病大鼠视网膜的厚度，但视网膜的结构在各组间无差别；小檗碱(150及300 mg·kg^-1)和罗格列酮(4 mg·kg^-1)能明显降低糖尿病大鼠视网膜中PPARγ蛋白表达，小檗碱(150及300 mg·kg^-1)和非诺贝特(100 mg·kg^-1)能显著增加糖尿病大鼠视网膜中PPARα和PPARδ的表达。小檗碱调控视网膜PPAR α/δ/γ蛋白表达可能是其改善糖尿病视网膜病的机制之一，可能成为比罗格列酮和非诺贝特更有效的用于治疗糖尿病视网膜病的药物。     

Ameliorative effect of berberine on endothelial dysfunction in diabetic rats induced by high-fat diet and streptozotocin

Berberine can improve insulin resistance, lower blood glucose, and regulate lipid metabolism disorders which cause endothelial dysfunction, leading to vascular complications of type 2 diabetes mellitus. The aim of the present study was to investigate the effects of berberine on endothelial dysfunction of aortas in type 2 diabetes mellitus rats and its mechanism. Wistar rats were randomly divided into four groups: diabetic rats, control rats, diabetic rats treated with berberine (100 mg/kg), and control rats treated with berberine. The serum fasting blood glucose, insulin, total cholesterol, triglyceride and nitric oxide (NO) levels were tested. Acetylcholine-induced endothelium-dependent relaxation and sodium nitroprusside induced endothelium-independent relaxation were measured in aortas for estimating endothelial function. The expression of endothelial nitric oxide synthase (eNOS) mRNA was measured by RT-PCR, and the protein expressions of eNOS and NADPH oxidase (NOX4) were analyzed by western blot. The results showed that berberine significantly decreased fasting blood glucose, and triglyceride levels in diabetic rats. Berberine also improved endothelium-dependent vasorelaxation impaired in aorta. The expressions of eNOS mRNA and protein were significantly increased, while NOX4 protein expression was decreased in aortas from diabetic rats with berberine treatment. Moreover, serum NO levels were elevated after berberine treatment. In conclusion, berberine restores diabetic endothelial dysfunction through enhanced NO bioavailability by up-regulating eNOS expression and down-regulating expression of NADPH oxidase.     

小檗碱对2型糖尿病大鼠骨骼肌糖脂代谢的影响及其机制

目的观察小檗碱对糖尿病大鼠骨骼肌病理结构改变和糖脂代谢紊乱的影响及其与PPARe α/γ/δ蛋白表达的关系。方法注射链脲菌素（35mg·kg^-1，i．p．）加高糖高脂饲料喂养16周建立2型糖尿病大鼠模型，随后16周每天分别拌食给予低中高剂量小檗碱（75、150、300mg·kg^-1）、非诺贝特（100mg·k^-1）和罗格列酮（4mg·k^-1），用HE染色检查骨骼肌结构病变、分光光度法测定肌糖元和甘油三脂含量及免疫组化检测PPAR α/γ/δ的表达。结果骨骼肌纤维在各组大鼠中仍正常分布，中高剂量小檗碱部分地改善糖尿病肌纤维的萎缩，增加肌糖元和降低甘油三脂含量（P〈0．01）。中高剂量小檗碱和罗格列酮都能明显降低糖尿病大鼠骨骼肌中PPARγ蛋白水平（P〈0．01），中高剂量小檗碱和非诺贝特能促进PPARα和PPARδ的表达（P〈0．01）。结论小檗碱调控骨骼肌PPARα/γ/δ蛋白的表达可能是其改善糖尿病骨骼肌纤维萎缩和糖脂代谢紊乱的机制之一。     

The PPARalpha/gamma dual agonist chiglitazar improves insulin resistance and dyslipidemia in MSG obese rats

1. The aim of this study was to investigate the capacity of chiglitazar to improve insulin resistance and dyslipidemia in monosodium L-glutamate (MSG) obese rats and to determine whether its lipid-lowering effect is mediated through its activation of PPARalpha. 2. Chiglitazar is a PPARalpha/gamma dual agonist. 3. The compound improved impaired insulin and glucose tolerance; decreased plasma insulin level and increased the insulin sensitivity index and decreased HOMA index. Euglycemic hyperinsulinemic clamp studies showed chiglitazar increased the glucose infusion rate in MSG obese rats. 4. Chiglitazar inhibited alanine gluconeogenesis, lowered the hepatic glycogen level in MSG obese rats. Like rosiglitazone, chiglitazar promoted the differentiation of adipocytes and decreased the maximal diameter of adipocytes. In addition, chiglitazar decreased the fibrosis and lipid accumulation in the islets and increased the size of islets. 5. Chiglitazar reduced plasma triglyceride, total cholesterol (TCHO), nonesterified fatty acids (NEFA) and low density lipoprotein-cholesterol levels; lowered hepatic triglyceride and TCHO contents; decreased muscular NEFA level. Unlike rosiglitazone, chiglitazar showed significant increase of mRNA expression of PPARalpha, CPT1, BIFEZ, ACO and CYP4A10 in the liver of MSG obese rats. 6. These data suggest that PPARalpha/gamma coagonist, such as chiglitazar, affect lipid homeostasis with different mechanisms from rosiglitazone, chiglitazar may have better effects on lipid homeostasis in diabetic patients than selective PPARgamma agonists.     

Berberine suppresses intestinal disaccharidases with beneficial metabolic effects in diabetic states, evidences from in vivo and in vitro study

Clinical reports have demonstrated that berberine is a potential antidiabetic agent, but the underlying mechanism is unclear. The purpose of this study was to investigate if berberine exerts its hypoglycemic action via inhibiting intestinal disaccharidases using in vivo and in vitro experiments. Streptozotocin-induced diabetic rats received berberine (100 or 200 mg/kg) orally once daily or acarbose (40 mg/kg) orally twice daily for 5 weeks. Disaccharidase activities and sucrase–isomaltase (SI) complex messenger RNA (mRNA) expression in intestinal regions were assessed. The same treatment was operated in normal rats. Sucrose and maltose loading tests were also documented. In addition, Caco-2 cells were cultured in medium containing berberine or berberine plus chelerythrine. Compound C or H-89 for 5 days, disaccharidase activities, and SI complex mRNA levels were measured. The animal experiments showed that berberine significantly decreased the disaccharidase activities and SI complex mRNA expression both in diabetic rats and normal rats. Berberine can also significantly lower postprandial blood glucose levels induced by sucrose or maltose loading in normal rats. The cellular results showed that berberine may suppress disaccharidase activities and downregulate SI complex mRNA expression in a concentration-dependent manner. Only H-89, an inhibitor of protein kinase A (PKA), may reverse the decrease in disaccharidase activities and SI complex mRNA expression induced by berberine. In conclusion, berberine suppresses disaccharidase activities and SI complex mRNA expression with beneficial metabolic effects in diabetic states. The inhibitory effect, at least partly, involves the PKA-dependent pathway.     

Osthole improves fat milk-induced fatty liver in rats: modulation of hepatic PPAR-alpha/gamma-mediated lipogenic gene expression

The objectives of this study were to determine the therapeutic effect of osthole, an active constituent isolated from Cnidium monnieri (L.) Cusson (Apiaceae), in hyperlipidemic fatty liver (HFL) rats and investigate the possible mechanism of the osthole treatment. The HFL rat model was established by feeding Sprague-Dawley rats with fat milk for 6 weeks. The experimental rats were then treated with a dose of osthole of 5 - 20 mg/kg for 6 weeks. After the treatment, total cholesterol (TC) and triglycerides (TG) in serum and hepatic tissue, as well as the coefficient of hepatic weight were measured. The results showed that the TC and TG in both serum and hepatic tissue and the coefficient of hepatic weight in the osthole-treated rats were lower as compared to those in the experimental group, respectively (P < 0.05 or P < 0.01). Moreover, as compared to the control group, the osthole treatment increased the PPARalpha/gamma mRNA expression by 58.0 - 84.0 % and 20.4 - 77.4 %, respectively. The related target genes for mRNA expression were also increased by osthole-treatment, e. g., 53.4 - 93.2 % for CYP7A, 21.1 - 63.2 % for L-FABP and 34.1 - 57.3 % for FATP4, while the DGAT mRNA expression was decreased by 26.0 - 44.4 %. The therapeutic effect of osthole was further confirmed by histological evaluation of the liver showing a dramatically decreased lipid accumulation and improved ultrastructure of hepatocytes. In conclusion, osthole exerts therapeutic effects on fat milk-induced fatty liver in rats, by regulating mRNA expression of the target genes of CYP7A, DGAT, L-FABP and FATP4 via increasing the PPARalpha/gamma mRNA expression.     

Therapeutic effects of berberine in impaired glucose tolerance rats and its influence on insulin secretion

AIM: To explore the anti-diabetic effects of berberine and its influence on insulin secretion. METHODS: Impaired glucose tolerance rats induced by iv injection of streptozotocin 30 mg/kgwere treated with berberine 187.5 and 562.5 mg/kg while fed with high fat laboratory chow. After rats were treated for 4 weeks, oral glucose tolerance was determined, and for 8 weeks, the fasting blood glucose, insulin, lipid series were determined. In insulin secretion experiments, berberine 93.75, 187…     

小檗碱对高果糖饲养诱导大鼠胰岛素抵抗和肝脏TNF-α表达的影响

目的研究小檗碱对高果糖饲养诱导胰岛素抵抗大鼠的作用。方法高果糖饲料喂养SD大鼠6wk后,分为3组,模型组,小檗碱组(187.5mg.kg-1.d-1灌服)、二甲双胍组(184mg.kg-1.d-1灌服)作为对照,继续高果糖饮食。实验同时设立正常对照组,普通饮食喂养。4wk后处死大鼠;测定血糖、血清胰岛素、胰岛素抵抗指数及血脂的变化,用RT-PCR方法观察肝脏TNF-αmRNA的表达。结果模型组胰岛素、胰岛素抵抗指数、游离脂肪酸(free fatty acids,FFA)及甘油三酯(triglycerides,TG)水平均明显升高;肝脏TNF-αmRNA的表达与正常对照组比较明显升高。小檗碱降低了胰岛素抵抗大鼠的血糖、血清胰岛素、胰岛素抵抗指数、TG、FFA及TNF-αmRNA的表达。二甲双胍降低了大鼠的血糖、血清胰岛素、胰岛素抵抗指数及TG。结论小檗碱可以改善胰岛素抵抗,其机制可能包括抑制肝脏TNF-αmR-NA的表达与改善脂代谢紊乱。     

Lack of hypotriglyceridemic effect of gemfibrozil as a consequence of age-related changes in rat liver PPARalpha

We have investigated if changes in hepatic lipid metabolism produced by old age are related to changes in liver peroxisome proliferator-activated receptor alpha (PPARalpha). Our results indicate that 18-month-old rats showed a marked decrease in the expression and activity of liver PPARalpha, as shown by significant reductions in PPARalpha mRNA, protein and binding activity, resulting in a reduction in the relative mRNA levels of PPARalpha target genes, such as liver-carnitine-palmitoyl transferase-I (CPT-I) and mitochondrial medium-chain acyl-CoA dehydrogenase (MCAD). Further, in accordance with a liver PPARalpha deficiency in old rats, treatment of old animals with a therapeutic dose of gemfibrozil (GFB) (3mg/kg per day, 21 days) was ineffective in reducing plasma triglyceride concentrations (TG), despite attaining a 50% reduction in TG when GFB was administered to young animals at the same dose and length of treatment. We hypothesize that the decrease in hepatic PPARalpha can be related to a state of leptin resistance present in old animals.     

Antihyperglycaemic effect of 'Ilogen-Excel', an ayurvedic herbal formulation in streptozotocin-induced diabetes mellitus

'Ilogen-Excel', an Ayurvedic herbal formulation is composed of eight medicinal plants (Curcuma longa, Strychnos potatorum, Salacia oblonga, Tinospora cordifolia, Vetivelia zizanioides, Coscinium fenestratum, Andrographis paniculata and Mimosa pudica). The present study evaluates the antihyperglycemic effect of 'Ilogen-Excel' in streptozotocin induced diabetic rats. Rats were rendered diabetic by streptozotocin (STZ) (45 mg/kg body weight). Oral administration of 'Ilogen-Excel' (50 mg/kg and 100 mg/kg) for 60 days resulted in significantly lowered levels of blood glucose and significantly increased levels of plasma insulin, hepatic glycogen and total hemoglobin. 'Ilogen-Excel' administration also decreased the levels of glycosylated hemoglobin, plasma thiobarbituric acid reactive substances, hydroperoxides, ceruloplasmin and vitamin E in diabetic rats. Plasma reduced glutathione and vitamin C were significantly elevated by oral administration of 'Ilogen-Excel'. Administration of insulin normalized all the biochemical parameters studied in diabetic rats. The effect at a dose of 100 mg/kg was more pronounced than 50 mg/kg and brought back all the parameters to near normal levels. Thus, our study shows the antihyperglycemic effects of 'Ilogen-Excel' in STZ-induced diabetic rats. Our study also shows that combined therapy is better than individual therapy.     

Effect of tetrahydrocurcumin on blood glucose, plasma insulin and hepatic key enzymes in streptozotocin induced diabetic rats

The enzymes of glucose and lipid metabolism are markedly altered in experimental diabetes. In the present study, we investigated the effect of tetrahydrocurcumin (THC), one of the active metabolites in curcumin, on the key hepatic metabolic enzymes involved in carbohydrate metabolism in streptozotocin-induced diabetic rats. Different doses of THC (20, 40, and 80 mg\kg body weight) were orally administered to diabetic rats for 45 days. The activities of hexokinase, glucose-6-phosphate dehydrogenase (G6PD), glucose-6-phosphatase, fructose-1,6-bisphosphatase, and sorbitol dehydrogenase in liver, and glycogen content in liver and muscle were assayed. In untreated diabetic control rats, the activities of the gluconeogenic enzymes were significantly increased, whereas hexokinase and G6PD activity and glycogen levels were significantly decreased. Both THC and curcumin were able to restore the altered enzyme activities to near normal levels. Tetrahydrocurcumin was more effective than curcumin. Our results indicate that the administration of THC to diabetic animals normalizes blood glucose and causes a marked improvement of altered carbohydrate metabolic enzymes.     

Berberine – a novel approach to cholesterol lowering

Although low-density lipoprotein (LDL)-cholesterol lowering with the statins reduces the mortality and morbidity associated with coronary artery disease, considerable mortality and morbidity remains. Berberine upregulates the LDL receptor (LDLR) by a mechanism distinct from that of the statins, which involves stabilising the LDLR mRNA. In hamsters fed a high-fat and high-cholesterol diet for 2 weeks, the oral administration of berberine 100 mg/kg for 10 days reduced total serum cholesterol from ～ 4.8 to 2.7 mmol/l, and LDL-cholesterol from ～ 2.5 to 1.4 mmol/l. In subjects with hypercholesterolaemia, berberine hydrochloride (0.5 g b.i.d. for 3 months) reduced LDL-cholesterol (from 3.2 to 2.4 mmol/l) without any effect on high-density lipoprotein-cholesterol. Berberine also caused a reduction in triglyceride levels from 2.3 to 1.5 mmol/l. As berberine and statins both upregulate LDLR, their lipid-lowering profiles are similar. Thus, this mechanism is unlikely to make berberine an attractive alternative to statins for lipid lowering in most circumstances. However, the other effects of berberine (antihypertensive, inotropic and class III antiarrhythmic properties) may make it a useful agent in the treatment of cardiovascular disease.     

Berberine reducing insulin resistance by up-regulating IRS-2 mRNA expression in nonalcoholic fatty liver disease (NAFLD) rat liver

This study was performed to investigate the molecular mechanism and the therapeutic effect of berberine on nonalcoholic fatty liver disease (NAFLD). Rat models were given a high-fat diet (42% kcal) until they developed NAFLD, then were given normal saline (n = 10), berberine (n− = 10) at 187.5 mg/kg/day, or pioglitazone (n = 10) at 10.0 mg/kg/day intragastrically for 4 weeks, respectively, and evaluated by hyperinsulinemic euglycemic clamping for insulin sensitivity. Serum biochemical markers and liver triglyceride (TG) were analyzed, real-time RT-PCR for mRNA expression and western blotting for protein expression of insulin receptor (IR) and insulin receptor substrate-2 (IRS-2) in liver tissues were performed, and hepatic histopathology in the rat models with NAFLD at the end of treatment was compared with normal controls (n = 10). The NAFLD rats developed insulin resistance, showing increased fasting blood glucose and insulin levels, decreased glucose infusion rate, increased weight of epididymal fat (g/100 g body weight), obvious hepatic steatosis and inflammation, and down-regulated IRS-2 mRNA and protein levels compared with normal controls (all P < 0.05). In comparison with those treated with saline, model rats treated with berberine or pioglitazone underwent significant recovery, including up-regulated IRS-2 mRNA and protein (all P < 0.05). Our results indicate that berberine may improve insulin resistance of NAFLD by up-regulating mRNA and protein levels of IRS-2, a key molecule in the insulin signaling pathway, suggesting that berberine may be used to treat NAFLD.     

Berberine--a novel approach to cholesterol lowering

Although low-density lipoprotein (LDL)-cholesterol lowering with the statins reduces the mortality and morbidity associated with coronary artery disease, considerable mortality and morbidity remains. Berberine upregulates the LDL receptor (LDLR) by a mechanism distinct from that of the statins, which involves stabilising the LDLR mRNA. In hamsters fed a high-fat and high-cholesterol diet for 2 weeks, the oral administration of berberine 100 mg/kg for 10 days reduced total serum cholesterol from approximately 4.8 to 2.7 mmol/l, and LDL-cholesterol from approximately 2.5 to 1.4 mmol/l. In subjects with hypercholesterolaemia, berberine hydrochloride (0.5 g b.i.d. for 3 months) reduced LDL-cholesterol (from 3.2 to 2.4 mmol/l) without any effect on high-density lipoprotein-cholesterol. Berberine also caused a reduction in triglyceride levels from 2.3 to 1.5 mmol/l. As berberine and statins both upregulate LDLR, their lipid-lowering profiles are similar. Thus, this mechanism is unlikely to make berberine an attractive alternative to statins for lipid lowering in most circumstances. However, the other effects of berberine (antihypertensive, inotropic and class III antiarrhythmic properties) may make it a useful agent in the treatment of cardiovascular disease.     

Antihyperglycemic activity and antidiabetic effect of methyl caffeate isolated from Solanum torvum Swartz. fruit in streptozotocin induced diabetic rats

Natural remedies from medicinal plants are considered to be effective and safe alternatives to treat diabetes mellitus. Solanum torvum Swartz. fruit is widely used in the traditional system of medicine to treat diabetes. In the present study methyl caffeate, isolated from S. torvum fruit, was screened for its efficacy in controlling diabetes in animal models. Antihyperglycemic effect of methyl caffeate was studied in normal glucose-fed rats. The effects of oral administration of methyl caffeate (10, 20 and 40 mg/kg) for 28 days on body weight, fasting blood glucose, plasma insulin, hemoglobin, glycated hemoglobin, total protein, hepatic glycogen and carbohydrate metabolism enzymes in streptozotocin induced diabetic rats were investigated. Histological observations in the pancreas and GLUT4 expression in skeletal muscles were also studied. Methyl caffeate at 40 mg/kg significantly prevented the increase in blood glucose level after glucose administration at 60 min in comparison to the hyperglycemic control group. In streptozotocin induced diabetic rats, methyl caffeate produced significant reduction in blood glucose and increased body weight. The levels and/or activities of other biochemical parameters were near normal due to treatment with methyl caffeate. Methyl caffeate treated diabetic rats showed upregulation of GLUT4 and regeneration of β-cells in the pancreas. These results substantiated that methyl caffeate possessed hypoglycemic effect, and it could be developed into a potent oral antidiabetic drug.     

Berberine inhibits dyslipidemia in C57BL/6 mice with lipopolysaccharide induced inflammation

BackgroundInhibiting the action of proprotein convertase subtilisin/kexin type 9 (PCSK9) on the low-density lipoprotein receptor (LDLR) has emerged as a novel therapeutic target for hypercholesterolemia. Here we investigated the effect of berberine, natural plant extracts, on PCSK9-LDLR pathway in C57BL/6 mice with lipopolysaccharide (LPS) induced inflammation.MethodsForty female mice were divided into four groups (n = 10): control, LPS (5 mg/kg), LPS + berberine 10 (5 mg/kg LPS plus 10 mg/kg berberine), and LPS + berberine 30 (5 mg/kg LPS plus 30 mg/kg berberine). Changes in the levels of blood lipids [total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C)]; pro-inflammatory cytokines [interferon-γ (IFNγ), tumor necrosis factor α (TNFα), and interleukin-1α (IL-1α)], 8-isoprostane, hepatic expressions of PCSK9 and LDLR were determined.ResultsBerberine pretreatment reduced the expression of hepatic PCSK9, decreased the plasma TC, TG, LDL-C, IFNγ, TNFα, IL-1α, and 8-isoprostane concentrations; increased HDL-C level and LDLR expression in mice.ConclusionThe present results suggest that berberine inhibits dyslipidemia in C57BL/6 mice with LPS induced inflammation through regulating PCSK9-LDLR pathway.     

Green tea extract impedes dyslipidaemia and development of cardiac dysfunction in streptozotocin-diabetic rats

1. The efficacy of green tea extract (GTE) on serum and cardiac lipids was investigated in streptozotocin (STZ)-diabetic rats. 2. Diabetes was induced in rats by a single intraperitoneal injection of STZ (60 mg/kg bodyweight). Six weeks after the induction of diabetes, GTE was administered orally for 4 weeks (300 mg/kg bodyweight daily). Bodyweight, heart weight, heart weight : bodyweight ratio, blood glucose, serum and cardiac lipids were determined in experimental rats. 3. In diabetic rats, there was a significant decrease in bodyweight with an increase in heart weight : bodyweight ratio and blood glucose. Diabetic rats had significantly increased serum levels of cholesterol, triglycerides, free fatty acids and low-density lipoprotein-cholesterol (LDL-C) and decreased levels of high-density lipoprotein-cholesterol (HDL-C). In the hearts of diabetic rats, there was a significant increase in cholesterol, triglycerides and free fatty acids levels, with an increase in lipoprotein lipase activity. 4. The administration of GTE to diabetic rats resulted in significant recovery in bodyweight, heart weight : bodyweight ratio and blood glucose levels. The administration of GTE reduced cholesterol, triglyceride, free fatty acid and LDL-C levels, and increased HDL-C levels, in the serum of diabetic rats. In addition, GTE decreased cholesterol, triglyceride, free fatty acids levels and lipoprotein lipase activity in the myocardium of diabetic rats. These beneficial effects of GTE are ascribed to its antihyperglycaemic and hypolipidaemic activity. In conclusion, green tea can reduce the risk of cardiovascular disease in diabetes with a significant improvement in lipid metabolism.