No abstract

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-a 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 b-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.

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.

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.

The cortex of Eucommia ulmoides Oliver is widely used to treat kidney deficiency in traditional Chinese medicine. Its leaves have recently been reported to have anti-obesity properties in metabolic syndrome-like rat models. Due to a sharp decline in estrogen production, obesity, together with osteoporosis, are common problems in postmenopausal women. In this study, we examined the potential effect of Eucommia leaf extract (ELE) in preventing osteoporosis and obesity induced by ovariectomy (OVX). Forty-six female Wistar rats were divided into six groups: Sham-Cont, OVX-Cont, and four OVX groups administered estradiol and different concentrations of ELE 1.25%, ELE 2.5%, and ELE 5%. Treatments were administered after ovariectomy at six weeks of age and continued for 12 weeks. OVX induced a significant decrease in the bone mineral density (BMD) of the lumbar, femora, and tibiae, together with a marked increase in body mass index (BMI). The administration of 5% ELE led to a significant increase in tibial and femoral BMD, as well as significantly increased bone-strength parameters when compared with OVX-Cont rats. According to the suppressed Dpd and increased osteocalcin concentrations in ELE 5% rats, we suggest that varying proportions of bone formation and bone absorption contributed to the enhanced BMD in the femora and tibiae. In addition, significant decreases in body weight, BMI and fat tissue in 5% ELE rats were also observed. These results suggest that ELE may have curative properties for BMD and BMI in OVX rats, and could provide an alternative therapy for the prevention of both postmenopausal osteoporosis and obesity.