British Journal of Nutrition

Metabolism and Metabolic Studies

The fat and protein fractions of freshwater clam (Corbicula fluminea) extract reduce serum cholesterol and enhance bile acid biosynthesis and sterol excretion in hypercholesterolaemic rats fed a high-cholesterol diet

Takeshi Chijimatsua1a2 c1, Miki Umekia3, Yuji Okudaa4, Koji Yamadaa5, Hiroaki Odaa4 and Satoshi Mochizukia3

a1 Sasaki Food Company, Limited, 276 Sakai, Bungotakada, Oita 879-0615, Japan

a2 Shizenshokken Company, Limited, Oita 879-0615, Japan

a3 Faculty of Education and Welfare Science, Oita University, Oita 870-1192, Japan

a4 Laboratory of Nutritional Biochemistry, Department of Applied Molecular Biosciences, Nagoya University, Nagoya 464-8601, Japan

a5 Garden for Medical Plants, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki 852-8521, Japan


We investigated whether the fat and protein fractions of freshwater clam (Corbicula fluminea) extract (FCE) could ameliorate hypercholesterolaemia in rats fed a high-cholesterol diet. We also explored the mechanism and the components that exert the hypocholesterolaemic effect of FCE. The doses of the fat and protein fractions were equivalent to those in 30 % FCE. The fat and protein fractions of FCE, two major components of FCE, significantly reduced the serum and hepatic cholesterol levels. The fat fraction more strongly reduced serum cholesterol levels than the same level of total FCE. The excretion of faecal neutral sterols increased in rats fed the total the FCE and the fat fraction of FCE. On the other hand, faecal bile acid levels were greater in rats fed the total FCE and the fat and protein fractions of FCE than in control animals. The hepatic gene expression of ATP-binding cassette transporter G5 and cholesterol 7α-hydroxylase was up-regulated by the administration of the total FCE and both the fat and protein fractions of FCE. These results showed that the fat and protein fractions of FCE had hypocholesterolaemic properties, and that these effects were greater with the fat fraction than with the protein fraction. The present study indicates that FCE exerts its hypocholesterolaemic effects through at least two different mechanisms, including enhanced excretion of neutral sterols and up-regulated biosynthesis of bile acids.

(Received May 10 2010)

(Revised July 13 2010)

(Accepted August 26 2010)

(Online publication October 08 2010)


c1 Corresponding author: T. Chijimatsu, fax +81 978 24 0578, email


Abbreviations: ABC, ATP-binding cassette; FCE, freshwater clam extract