Hypocholesterolemic mechanism of Chlorella: Chlorella and its indigestible fraction enhance hepatic cholesterol catabolism through up-regulation of cholesterol 7alpha-hydroxylase in rats.
Chlorella powder (CP) has a hypocholesterolemic effect and high bile acid-binding capacity; however, its effects on hepatic cholesterol metabolism are still unclear. In the present study, male Wistar rats were divided into four groups and fed a high sucrose + 10% lard diet (H), an H + 10% CP diet (H+CP), an H + 0.5% cholesterol + 0.25% sodium cholate diet (C), or a C + 10% CP diet (C+CP) for 2 weeks. CP decreased serum and liver cholesterol levels significantly in rats fed C-based diets, but did not affect these parameters in rats fed H-based diets. CP increased the hepatic mRNA level and activity of cholesterol 7alpha-hydroxylase (CYP7A1). CP increased hepatic HMG-CoA reductase (HMGR) activity in the rats fed H-based diets, but not in rats fed C-based diets. CP did not affect hepatic mRNA levels of sterol 27-hydroxylase, HMGR, low-density lipoprotein (LDL) receptor, scavenger receptor class B1, ATP-binding cassette (ABC) A1, ABCG5, or ABCB11. Furthermore, the effect of a 3.08% Chlorella indigestible fraction (CIF, corresponding to 10% CP) on hepatic cholesterol metabolism was determined using the same animal models. CIF also decreased serum and liver cholesterol levels significantly in rats fed C-based diets. CIF increased hepatic CYP7A1 mRNA levels. These results suggest that the hypocholesterolemic effect of CP involves enhancement of cholesterol catabolism through up-regulation of hepatic CYP7A1 expression and that CIF contributes to the hypocholesterolemic effect.
Shibata
Shinya
S
Yakult Central Institute for Microbiological Research, Tokyo, Japan. shinya-shibata@yakult.co.jp
Hayakawa
Kazuhito
K
Egashira
Yukari
Y
Sanada
Hiroo
H
D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis; D020418:Algal Proteins / Q000737:chemistry / Q000494:pharmacology; D000818:Animals; D000924:Anticholesteremic Agents / Q000494:pharmacology*; D002708:Chlorella / Q000737:chemistry*; D002784:Cholesterol / Q000378:metabolism*; D002790:Cholesterol 7-alpha-Hydroxylase / Q000096:biosynthesis*; D004032:Diet; D004435:Eating / Q000187:drug effects; D006903:Hydroxymethylglutaryl CoA Reductases / Q000096:biosynthesis / Q000235:genetics; D050356:Lipid Metabolism / Q000187:drug effects; D008055:Lipids / Q000097:blood; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism; D009929:Organ Size / Q000187:drug effects; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D011973:Receptors, LDL / Q000187:drug effects; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051779:Sterol Regulatory Element Binding Proteins / Q000096:biosynthesis; D015854:Up-Regulation / Q000187:drug effects; D015430:Weight Gain / Q000187:drug effects
D018528:ATP-Binding Cassette Transporters; D020418:Algal Proteins; D000924:Anticholesteremic Agents; D008055:Lipids; D012333:RNA, Messenger; D011973:Receptors, LDL; C470194:Srebf2 protein, rat; D051779:Sterol Regulatory Element Binding Proteins; D002784:Cholesterol; D006903:Hydroxymethylglutaryl CoA Reductases; D002790:Cholesterol 7-alpha-Hydroxylase