Oikawa H (2017) The characteristic taste of Eucommia leaf extract as the additive of a weight-loss and the constipation improvement is not associated with suppression of the feeding behavior of the fast rats with the extract

IntroductionDu-zhong tea is a common drink ingested for health purposes. The tea is made by roasting the leaves of the Eucommia ulmoides tree. In recent years, the study of Eucommia leaf extract (ELE) has been focused on its efficacy in maintaining human health. Reports on the biogenic effectiveness of ELE ingestion have identified the following benefits: 1) antihyperlipidemic effects that reduce visceral fat and suppress elevated levels of triglyceride and cholesterol in the blood [1][2][3][4][5][6][7]; 2) effects on bone, such as preventing the onset of postmenopausal osteoporosis and promoting calcium accumulation in osteoblasts [8][9][10]; 3) antihypertensive effects that slowly decrease blood pressure by maintaining the flexibility of the blood vessels and promoting arterial smooth muscle relaxation [2,11]; 4) rapid eye movement sleep and non-rapid eye movement sleep inducing effect [12]; and 5) preventative effects on ulcerative colitis by asperuloside, one of the major components of ELE [13]. Thus, ELE promotes systemic health. Among the effects of ELE, many anti-obesity effects have been studied from the viewpoint of preventing lifestyle diseases. Therefore, we proposed that ELE ingestion might prevent the obesity caused by nocturnal eating, as ELE ingestion reduces food intake and water consumption during the light phase (i.e., inactive period) in rats [7,14,15]. On the other hand, it has been reported that appetite suppression due to the inhibition of the parasympathetic nervous system, which controls the gastrointestinal tract, is related to the suppression of feeding and the improvement AbstractEucommia leaf extract (ELE) is known to have a preventive effect on obesity. The effect of ELE partially depends on the inhibition of locomotor activity during inactive periods and indirect inhibition of food and water consumption. Moreover, it has been reported that suppression of the parasympathetic nervous system is involved in appetite suppression and that lipid metabolism is improved by ELE ingestion. However, there is no evidence that food and water consumption during the inactive period occur as a result of regulation of the parasympathetic nervous system. Therefore, in this study, the involvement of the parasympathetic nervous system was examined using water intake during the inactive period of rats as an index. Rats were fed a high-fat diet (35% fat; HFD) or an HFD + ELE 5% diet and were observed for 3 days during which pilocarpine (10 mg/kg/day, intraperitoneally; i.p.) or saline (i.p.; used as a control) was administered daily. When compared with the control group, no effect of pilocarpine was observed in the dark phase (active period) or light phases (inactive period). The slightly increased water consumption of the HFD + ELE 5% group was not affected by the administration of pilocarpine in the active period. However, the markedly decreased amount of water consumption in the inactive period that was due to ELE ingestion was restored to the control level by the administration of pilocarpine. These r...