Hypocholesterolemic effect of naringin associated with hepatic cholesterolregulating enzyme changes in rats

The effects of the citrus bioflavonoid naringin were tested by using if as a supplement in a high-cholesterol diet. Male rats were fed for 42 days wit h a 1% (wt/wt) high cholesterol diet either with or without naringin-supple mentation (0.1%, wt/wt) to study the effect on plasma lipid levels, hepatic lipid contents, hepatic enzyme activity, and the excretion of fecal neutra l sterols. Naringin did not significantly alter the levels of plasma trigly cerides, however, the levels of plasma cholesterol (3.80 +/- 0.31 mmol/L: v s. 2.61 +/- 0.30 mmol/L, mean +/- SE; p < 0.05) and hepatic cholesterol (70 .3 +/- 4.3 mg/g vs. 54.3 +/- 3.8 mg/g, mean +/- SD; p < 0.05) were signific antly lowered compared to those of the control. HMG-CoA reductase (2487.0 /- 210.0 pmole/min/mg vs. 1879.0 +/- 236.0 pmole/min/mg, mean +/- SE; p < 0 .05) and ACAT (806.0 +/- 105.0 pmole/min/mg vs. 643.0 +/- 80.0 pmole/min/mg , mean +/- SE; p < 0.05) activities were both substantially lower in the na ringin-supplemented group than in the control. The naringin supplementation markedly decreased the excretion of fecal neutral sterols (204.7 +/- 28.5 mg/day) compared to the control (521.9 +/- 53.9 mg/day). The combination of the inhibited HMG-CoA reductase (-24.4%) and ACAT (-20.2%) activities as a result of naringin supplementation could account for the decrease of fecal neutral sterols.