Effects of du-zhong leaf extract on serum and hepatic lipids in rats fed a high-fat diet

Eucommia ulmoides extracts prevent the formation of advanced glycation end products

Proteins non-enzymatically react with reducing sugars to form advanced glycation end-products (AGEs), resulting in the induction of protein denaturation. Because the levels of AGE increase with age and are elevated in age-related diseases, such as diabetes and atherosclerosis, the intake of compound(s) that inhibit the formation of AGEs by daily meal may represent a potential strategy for preventing age-related diseases. In this study, we measured the inhibitory effects of several Eucommia ulmoides extracts on the formation of AGEs, N(ε)-(carboxymethyl)lysine (CML) and N(ω)-(carboxymethyl)arginine (CMA). Although a crude extract obtained from E. ulmoides bark is widely used as herbal medicine, E. ulmoides leaf extract (ELE) inhibited CML and CMA formation more effectively during the incubation of gelatin with ribose. Therefore, the inhibitory effects of compounds present in ELE on CML and CMA formation were studied. As a result, isoquercetin showed the strongest inhibitory effect of all the tested ELE components. These results indicate that the oral intake of ELE may inhibit the formation of AGEs, thereby ameliorating age-related diseases.

The Restorative Effects of Eucommia ulmoides Oliver Leaf Extract on Vascular Function in Spontaneously Hypertensive Rats

Eucommia ulmoides Oliv. leaf is a traditional Chinese antihypertensive and antidiabetic medicine. We examined the effects of chronic Eucommia leaf extract (ELE) administration on artery function and morphology in spontaneously hypertensive rats (SHRs). ELE was orally administered via normal diet ad libitum to six-week-old male SHRs at a concentration of 5% for seven weeks. Acetylcholine (ACh)-induced endothelium-dependent relaxation, sodium nitroprusside (SNP)-induced endothelium-independent relaxation, plasma nitric oxide (NO) levels, and media thickness were assessed. ELE significantly improved ACh-induced aortic endothelium-dependent relaxation but did not affect SNP-induced endothelium-independent relaxation in the SHRs, as compared to the animals receiving normal diet. Plasma NO levels and media thickness were significantly increased and decreased, respectively, in the ELE-treated SHRs. Therefore, long-term ELE administration may effectively improve vascular function by increasing plasma NO levels and bioavailability, and by preventing vascular hypertrophy in the SHR aorta.

Asperuloside stimulates metabolic function in rats across several organs under high-fat diet conditions, acting like the major ingredient of Eucommia leaves with anti-obesity activity

Eucommia leaves (Eucommia ulmoides Oliver) contain chlorogenic acid (a caffeic acid derivative) and geniposidic acid and asperuloside (ASP), iridoid glucosides used in beverages. We used a metabolic syndrome rat model, produced by feeding a 35 % high-fat diet (HFD), to examine potential anti-obesity and anti-metabolic syndrome effects and mechanisms of chronic administration of ASP. These effects were compared with Eucommia leaf extract (ELE), the positive control, which exhibits anti-obesity effects. A total of six rats were studied for 3 months in five groups. ASP suppressed body weight, visceral fat weight, food intake and circulating levels of glucose, insulin and lipids, and increased the plasma adiponectin level in rats on a HFD. These effects are similar to those of ELE, except for the influence on the plasma glucose level. RT-PCR studies showed that ASP (like ELE with known anti-obesity effects) diminished isocitrate dehydrogenase 3α, NADH dehydrogenase flavoprotein 1 (Comp I) mRNA and fatty acid synthase levels (white adipose tissue), increased carnitine palmitoyltransferase 1α and acyl-CoA dehydrogenase, very-long-chain mRNA levels (liver), and increased Glut4, citrate synthase, isocitrate dehydrogenase 3α, succinyl CoA synthase, peroxisomal 3-ketoacyl-CoA thiolase, dihydrolipoamide succinyl transferase and succinate dehydrogenase mRNA levels (skeletal muscle) under HFD conditions. Interestingly, ASP administration resulted in significantly increased mRNA levels of uncoupling protein 1 (UCP1) in the brown adipose tissue of HFD-fed rats; ELE did not affect the expression of UCP1. The increased expression of UCP1 may be negated by many ingredients other than ASP in the ELE. These findings suggest that chronic administration of ASP stimulates anti-obesity and anti-metabolic syndrome activity in HFD-fed rats across several organs, similar to ELE administration; thus, ASP may be an important ingredient of ELE.

Facilitative effects of Eucommia ulmoides on fatty acid oxidation in hypertriglyceridaemic rats

BACKGROUND

Tea made from Eucommia ulmoides leaves is widely consumed as a health food, since recent studies have revealed various pharmacological effects of the tea, e.g. a hypotriglyceridaemic effect. This study was conducted to elucidate the mechanisms underlying the plasma triglyceride-lowering effect of E. ulmoides leaves.

RESULTS

Rats were divided into four groups: a normal group, a group fed a high-fat/high-fructose diet (untreated group) and two groups fed a high-fat/high-fructose diet and E. ulmoides tea (4 or 20 g L(-1) extract, treated groups). Plasma triglyceride concentrations were reduced in treated groups in a dose-dependent manner compared with the untreated group. DNA microarray analysis revealed that genes involved in hepatic α-, β- and ω-oxidation, mainly related to the peroxisome proliferator-activated receptor α and δ signalling pathway, were up-regulated in the treated group. High-performance liquid chromatography analysis showed that E. ulmoides leaves contain three phytochemicals that make up 60 mg g(-1) of the material and are likely to be the active components.

CONCLUSION

This study indicates that the promotion of fatty acid oxidation, probably by the action of phytochemicals, participates in the ameliorative effect of E. ulmoides leaves on hypertriglyceridaemia. These findings provide the scientific evidence for the functionality of E. ulmoides.

Chronic administration of Eucommia leaf stimulates metabolic function of rats across several organs

Eucommia bark (Eucommia ulmoides Oliver) has been used as an herbal medicine, and more recently, the plant's leaves have been widely used to prepare tea which may have anti-obesity properties. We used a metabolic syndrome-like rat model, produced by feeding a 35 % high-fat diet (HFD), to examine potential anti-obesity and anti-metabolic syndrome effects and mechanisms of chronic administration of Eucommia leaf as an extract or green leaf powder. Eighty rats were studied for 3 months in ten groups. Both forms of Eucommia leaves minimised increases in body weight and visceral fat in a dose-dependent fashion. Increases in plasma levels of TAG and NEFA, and insulin resistance secondary to HFD were lessened by both forms of Eucommia leaf. Concomitantly, an increase in plasma adiponectin levels and suppression of plasma resistin and TNF-α levels were confirmed. Real-time PCR studies showed that both forms of Eucommia leaf enhanced metabolic function across several organs, including diminishing ATP production (white adipose tissue), accelerating β-oxidation (liver) and increasing the use of ketone bodies/glucose (skeletal muscle), all of which may exert anti-obesity effects under HFD conditions. These findings suggest that chronic administration of either form of Eucommia leaves stimulates the metabolic function in rats across several organs. The anti-obesity and anti-metabolic syndrome activity in this rat model may be maintained through secretion and regulation of adipocytokines that depend on the accumulation of visceral fat to improve insulin resistance or hyperlipaemia.

Ameliorative effect of Eucommia ulmoides Oliv. leaves extract (ELE) on insulin resistance and abnormal perivascular innervation in fructose-drinking rats

AIM OF THE STUDY

Eucommia ulmoides Oliv. leaf is a traditional Chinese medicine that exhibits an anti-diabetic action. This study was designed to investigate whether long-term administration of Eucommia ulmoides Oliv. leaves extract (ELE) ameliorates pre-diabetic state of insulin resistance and abnormal perivascular innervation in the hyperinsulinemic state.

MATERIALS AND METHODS

ELE at doses of 500 and 1000mg/kg was administered orally once daily for 4 weeks in fructose-drinking rats (FDRs). Plasma levels of insulin, blood glucose levels, and perivascular innervation were assessed using biochemical and immunohistochemical methods.

RESULTS

FDR showed significant increase in plasma levels of insulin, an index for insulin resistance (Homeostasis Model Assessment ratio-HOMA-IR) and systolic blood pressure (SBP), but not blood glucose levels, as compared with control rats. Immunohistochemical study showed significantly greater density of tyrosine hydroxylase (TH)-like immunoreactivity (LI)-containing nerves and significantly lower density of calcitonin gene-related peptide (CGRP)-LI-containing nerves in mesenteric arteries of FDR than those in control. A 4-week treatment with ELE (500 and 1000mg/kg, p.o.) significantly decreased plasma levels of insulin and HOMA-IR without affecting blood glucose levels and significantly lowered SBP in FDR. ELE treatment in FDR resulted in significant increase in CGRP-LI never fiber density and significant decrease in TH-LI never fiber density in mesenteric arteries of FDR.

CONCLUSIONS

These results suggest that long-term ELE treatment effectively prevents insulin resistance development and ameliorates abnormal perivascular innervation in FDR.

Chinese green tea lowers cholesterol level through an increase in fecal lipid excretion

Lung Chen Tea, a Chinese green tea, has been found to lower serum and liver cholesterol. In this study, its dose response and mechanisms of action on cholesterol lowering in diet-induced hypercholesterolemic Sprague-Dawley rats were investigated. The activities of three major lipid metabolizing enzymes, 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-Co A) reductase, cholesterol 7alpha-hydroxylase and fatty acid synthase (FAS), as well as fecal excretion of bile acids and cholesterol were examined. Lung Chen Tea administration for eight weeks significantly lowered the serum cholesterol in the 2% and 4% groups. The activities of the three enzymes were not affected by Lung Chen Tea, but the fecal bile acids and cholesterol excretions were significantly increased. These results demonstrated that Lung Chen Tea lowered plasma cholesterol by increasing fecal bile acids and cholesterol excretion. Further investigation is required to evaluate the exact mechanisms of action of Lung Chen Tea.