Preventing dyslipidemia by Chlorella pyrenoidosa in rats and hamsters after chronic high fat diet treatment

Abstract

The effects of Chlorella pyrenoidosa on serum lipid profiles, after concomitant long-term treatment of high-fat diet (HFD) in rats and hamsters was studied. Wistar rats and Syrian hamsters were fed with or without various concentrations of Chlorella pyrenoidosa contained high-fat diet (CHFD) for 2, 4 and 8 weeks prior to assay of serum lipids. Fasting triglycerides, total cholesterol, and LDL cholesterol as well as HDL cholesterol levels in high-fat diet treated rats and hamster were determined. Results showed that triglycerides, total cholesterol and LDL cholesterol levels in HFD treated rats and hamsters were increased from the normal rodent diet (NRD) treated controls after 2, 4, and 8–week treatments. However, the presence of Chlorella pyrenoidosa in high-fat diets significantly decreased the levels of triglycerides, total cholesterol and LDL cholesterol with comparison to HFD group in rats and hamsters. The total cholesterol/HDL ratios, an indication of occurrence of coronary heart disease, were decreased in all CHFD treated grouped rats and hamsters which suggests administration of Chlorella pyrenoidosa could lower the occurring risk of heart diseases. In conclusion, Chlorella pyrenoidosa has the ability to prevent dyslipidemia in chronic high-fat fed animals and could be potential in use to prevent intestinal absorption of redundant lipid from our daily intake and subsequently to prevent hyperlipidemia as well as atherosclerosis.

Introduction

Chlorella, a type of unicellular green algae, has been a popular foodstuff worldwide especially in Japan and Taiwan. It contains essential amino acids, minerals, and fibers (Borowitzka, 1988, Schubert, 1988). Administration of Chlorella has been shown to play some biochemical functions, such as antihypertensive effects from its peptides inhibiting angiotensin I converting enzyme (Suetsuna and Chen, 2001, Merchant et al., 2002); antioxidant and anti-cataract effects in streptozotocin-induced diabetes rats (Shibata et al., 2003); lowering blood glucose in diabetic animals (Rodriguez-Lopez and Lopez-Quijada, 1971); anti-inflammatory and immunomodulatory activities from its polysaccharides (Guzman et al., 2003); production of cytokine and boosting immune function (Queiroz et al., 2002, Konishi et al., 1996, Singh et al., 1998, Tanaka et al., 1998); ameliorating oxidative stress in mice and preventing stress-induced ulcer (Lee et al., 2003, Tanaka et al., 1997) as well as anti-tumor activities from its glycoproteins (Hasegawa et al., 2002). Chlorella vulgaris, one strain of Chlorella, has also been shown to influence rats' lipid contents in the liver and serum (Shibata et al., 2001). For cholesterol-fed rabbits, Chlorella vulgaris has anti-lipidemic and anti-atherosclerotic actions (Sano and Tanaka, 1987). In human study, Okudo et al. (1975) showed that Chlorella intake reduced cholesterol levels in patients with hypercholesterolemia. Chlorella pyrenoidosa is the main strain of Chlorella produced in Taiwan industries. However, the effects on blood lipids profile have not yet been shown by Chlorella pyrenoidosa in normal rats and hamsters but only in ovariectomized rats (Hidaka et al., 2004). Also in our study, hamster was additional included as one of the research animal models, since hamsters had similar lipoprotein and bile acid metabolism patterns as that in human (Spady et al., 1986a, Spady et al., 1986b). The, the aims of this study are to investigate the effects of Chlorella pyrenoidosa powder on the blood lipid profiles in rats and hamsters after chronic fed with high-fat diet containing cholesterol. This study might shed a light on the potential use of Chlorella pyrenoidosa for a treatment of hyperlipidemia or hypercholesterolemia in human.