Anti-Obesity Effects of Polymethoxyflavone-Rich Fraction from Jinkyool (Citrus sunki Hort. ex Tanaka) Leaf on Obese Mice Induced by High-Fat Diet

Polymethoxyflavones (PMFs) are flavonoids exclusively found in certain citrus fruits and have been reported to be beneficial to human health. Most studies have been conducted with PMFs isolated from citrus peels, while there is no study on PMFs isolated from leaves. In this study, we prepared a PMF-rich fraction (PRF) from the leaves of Citrus sunki Hort ex. Tanaka (Jinkyool) and investigated whether the PRF could improve metabolic decline in obese mice induced by a high-fat diet (HFD) for 5 weeks. The HFD-induced obese mice were assigned into HFD, OR (HFD + orlistat at 15.6 mg/kg of body weight/day), and PRF (HFD + 50, 100, and 200 mg/kg of body weight/day) groups. Orlistat and PRF were orally administered for 5 weeks. At the end of the experiment, the serum biochemical parameters, histology, and gene expression profiles in the tissues of each group were analyzed. The body weight gain of the obese mice was significantly reduced after orlistat and PRF administration for 5 weeks. PRF effectively improved HFD-induced insulin resistance and dyslipidemia. Histological analysis in the liver demonstrated that PRF decreased adipocyte size and potentially improved the liver function, as it inhibited the incidence of fatty liver. PRF activated AMP-activated protein kinase (AMPK), acetyl-CoA carboxylase (ACC), and hormone-sensitive lipase (HSL) in HFD-induced obese mice. Moreover, liver transcriptome analysis revealed that PRF administration enriched genes mainly related to fatty-acid metabolism and immune responses. Overall, these results suggest that the PRF exerted an anti-obesity effect via the modulation of lipid metabolism.