Abstract:

Objective: To investigate the effect of dietary Aetobatus flagelum protein (AFP) on cholesterol metabolism in
high cholesterol diet-fed rats and to explore the possible mechanism involved. Methods: Twenty-one male SD rats were
randomly divided into 3 groups, including normal control group (casein), 5% AFP-treated group (containing 5% AFP),
10% AFP-treated group (containing 10% AFP). After 28 days of consecutive administration, serum total cholesterol (TC),
high density lipoprotein cholesterol (HDL-C), hepatic cholesterol concentrations (TC and free cholesterol), and fecal bile
acid and neutral steroid were determined. The mRNA expression of key enzymes related to cholesterol metabolism, such as
HMG-CoA reductase, acyl-CoA-cholesterol acyltrasferase 2 (ACAT2), and cholesterol 7α-hydroxylase 1 (CYP7A1), was
also determined. Results: The levels of serum and hepatic TC were significantly decreased in rats fed AFP compared with
the control group (P < 0.05), while the concentration of serum HDL-C was increased and consequently the atherogenic index
was very significantly decreased in the AFP groups compared with in control group (P < 0.01). Moreover, dietary Aetobatus
flagelum protein significantly aggrandized the concentrations of fecal bile acid and neutral steroid (P < 0.05). The activity
of ACAT2 in liver was inhibited by dietary AFP, whereas the activity of hepatic HMG-CoA was not affected. On the other
hand, the mRNA expression of the CYP7A1 gene was significantly decreased (P < 0.05). Conclusion: Aetobatus flagelum
protein could significantly decrease serum and hepatic cholesterol accumulation, and lead to a decrease in serum atherogenic
index, mainly through promoting the metabolism of cholesterol and the excretion of fecal bile acid and neutral steroid.

Key words: Aetobatus flagelum protein, cholesterol metabolism, mechanism