Abstract:

The influence of black rice on serum lipid (TC, TG, HDL-C) levels and the expression of intestinal cholesterol
metabolism-related genes (HMG-CoA-R, MTP, ABCG5/8, ABCA1 and NPC1L1) induced by high fat and high cholesterol
diet (HFHC) was investigated in mice. Male mice (n = 48) were divided into four groups. They were fed a HFHC
diet alone (C group, n = 12), or supplemented with 52.6 g/100 g corn starch or with white rice (C+W group, n = 12),
26.3 g/100 g black rice (C+BL group, n = 12) or 52.6 g/100 g black rice (C+BH group, n = 12). After administration for 8
weeks, blood samples were collected for lipid measurements and viscera were removed at the end of the protocol. Serum
total cholesterol (TC), triglyceride (TG) and high-density lipoprotein cholesterol (HDL-C) were assayed by commercial
kits. Gas chromatography (GC) was used to determine cholesterol content in hepatic cells. The mRNA expression levels of
intestinal HMG-CoA-R, MTP, ABCG5/8, ABCA1 and NPC1L1 were detected by real-time PCR. The contents of serum TC,
TG and HDL-C in the experimental groups were similar with those of the control group. However, HDL-C in the black rice
groups was significantly elevated when compared with that of the control group (P < 0.05 or P < 0.01). Hepatic cholesterol
content were significantly decreased in the C + BL（P < 0.05）and C + BH（P < 0.01）groups when compared with that
of the C group. The mRNA expression levels of ABCG5/8 and ABCA1 in intestines were up-regulated by dietary back rice
(P < 0.01) when compared with those of the C group. The expression level of NPC1L1 mRNA was downregulated in the
C + BL (P < 0.05) and C + BH (P < 0.01) groups. The increase of cholesterol excretion and the inhibition of cholesterol
absorption in intestines may explain the mechanisms underlying the hypolipidemic effect of black rice.

Key words: black rice, mice, ABCG5/8, ABCA1, NPC1L1