Citrus junos Tanaka peel ameliorates hepatic lipid accumulation in HepG2 cells and in mice fed a high-cholesterol diet

BACKGROUND: Citrus junos Tanaka (yuja), a yellow-coloured citrus fruit has traditionally been consumed in Korea, Japan, and China and has been found effective in preventing certain diseases. However, the inhibitory effect of yuja on hepatic lipid accumulation has not been clearly elucidated thus far. METHODS: The inhibitory effect of yuja on hepatic lipid accumulation was investigated in both cell culture and mouse models. We investigated the inhibitory effect of ethanol extract of yuja peel (YE) using HepG2 cells. We next confirmed the effect of YE in mice fed a high cholesterol diet. Animals were divided into 4 groups (n = 8): a normal diet group (ND), a high-cholesterol diet group (HC), high-cholesterol diet plus 1% YE (YL), high-cholesterol diet plus 5% YE (YH). RESULT: Seventy percent ethanolic extracts of yuja peel (YE) reduced oleic acid-induced hepatic lipid accumulation in HepG2 cells. Treatment with YE at 100, 200 μg/mL up-regulated expression levels of cholesterol metabolism-related proteins such as AMPK, ACC, PPAR-α, and CPT1 and down-regulated the expression of 3-hydroxy-3-methylglutaryl coenzyme A reductase. The hypocholesterolemic effect of YE was further confirmed in mice fed a high-cholesterol diet. Compared to ND (normal diet) mice, HC (high-cholesterol diet) mice showed increased body weight, liver fat content, liver weight, and content of total cholesterol and low-density lipoprotein (LDL) cholesterol. On the contrary, administrations of YL (HC + 1% YE) or YH (HC + 5% YE) significantly reduced body weight, liver fat content, liver weight, total cholesterol, and LDL cholesterol compared to those of only HC fed mice group. As a result of in vitro data, protein expressions of PPAR-α and CPT1 were induced in mice fed YE diet compared to HC diet but HMGCR expression was decreased. CONCLUSIONS: Yuja peel ameliorates hepatic lipid accumulation in both cell culture and mouse models and therefore, could serve as a useful supplement for hypercholesterolemia.