br Acknowledgments This study was
Acknowledgments This study was supported by grants from the Spanish Ministry of Economy and CompetitivenessPI10/00387, PI12/01087, PI12/01703, IPT-2011-0817-010000, and RIC Red de Investigación Cardiovascular (RIC)RD12/0042/0055. RIC is an initiative of Instituto de Salud Carlos III (ISCIII), Spain. Authors thank Proteomic Unit, Instituto de Investigación Sanitaria Aragón (IIS), ProteoRed member, for technical support.
Introduction Cholesterol plays an indispensable role in biological functions ranging from cell membrane dynamic to signal transduction (Maxfield, Tabas, 2005, Temel, Brown, 2012). Hypercholesterolaemia can promote atherosclerotic cardiovascular disease, so maintaining cholesterol homeostasis is essential for body health. In the process of cholesterol metabolism, sterols regulatory element-binding proteins (SREBPs, mainly type 2) regulate genes related with the cholesterol synthesis (e.g. HMGR) (Krycer, Phan, & Brown, 2012). Niemann-Pick C1-Like 1 (NPC1L1) locating in the brush border membrane is a crucial transporter for dietary cholesterol harmine or re-absorption and can facilitate cholesterol influx through vesicular endocytosis (Altmann et al., 2004). Among the multistep processes related to cholesterol metabolism, reverse cholesterol transport (RCT) is an important one (Levinson & Wagner, 2015). During the process of RCT, the combined regulatory effects of ATP-binding cassette transporter A1 (ABCA1) and G1 (ABCG1), scavenger receptor class B type I (SR-BI) and cholesterol-7α-hydroxylase (CYP7A1) may play a critical role in modulating the metabolism of cholesterol (Sag et al, 2015, van der Wulp et al, 2013, Wang, Smith, 2014). ABCA1 and ABCG1 transported cellular free cholesterol and phospholipid to assemble nascent pre-β-1 high-density lipoprotein (HDL) particles and cholesterol ester-rich mature α-1 HDL particles, respectively. Subsequently, esterified cholesterol or free cholesterol from HDL particles was transferred to the liver via SR-BI (Valacchi, Sticozzi, Lim, & Pecorelli, 2011). CYP7A1 is responsible for converting cholesterol or cholesteryl ester to bile acids (Jiao, Zhang, Yu, Huang, & Chen, 2010). The ABCG5/G8 heterodimer, located at the apical membrane of the hepatocytes, is also able to transport cholesterol to bile ducts (Yu et al., 2014). As a global conductor of cholesterol homeostasis, LXRα governs the transcription of the above genes directly or indirectly (Bensinger & Tontonoz, 2008). It can limit cholesterol absorption by down-regulating NPC1L1 expression (Bonamassa & Moschetta, 2013). It also promotes cholesterol efflux by up-regulating expression of ABCA1, ABCG1 (Helal, Berrougui, Loued, & Khalil, 2013) and ABCG5/G8 (Yu et al., 2014) as well as CYP7A1 (Jiao et al., 2010). Persimmon (Diospyros kaki L.) fruit is reported to exert hypocholesterolaemic properties in some animal models. It has been found that dietary persimmon fruits prevented hypercholesterolaemia in rats fed with cholesterol diets (Gorinstein, Bartnikowska, Kulasek, Zemser, & Trakhtenberg, 1998). Matsumoto, Yokoyama, and Gato (2008) also investigated the hypolipidaemic effects of young persimmon fruit on apolipoprotein E-deficient C57BL/6.KOR- mice. Besides, our previous studies have confirmed that persimmon tannin, especially the high molecular weight persimmon tannin (HMWPT), was the main contributor of persimmon fruits or extract for its hypolipidaemic effect. HMWPT could significantly reduce serum and hepatic triacylglycerol, total cholesterol and LDL-C in high-cholesterol diet fed rats (Zou et al., 2012). In addition, Gato, Kadowaki, Hashimoto, Yokoyama, and Matsunnoto (2013) demonstrated that tannin-rich fibre from young persimmon fruits decreased plasma cholesterol levels and plasma low-density lipoprotein cholesterol (LDL-C) levels in human subjects. However, the underlying molecular mechanism involved in the hypocholesterolaemic activity of persimmon tannin is poorly elucidated. Our previous study demonstrated that persimmon tannin could significantly enhance faecal bile acids excretion via increasing serum lecithin cholesterol acyl transferase (LCAT) activity and up-regulating hepatic CYP7A1 gene in rats (Zou et al., 2014). However, it is not known how persimmon tannin intervenes with the cholesterol efflux and whether persimmon tannin could block the intestinal cholesterol absorption. Considering the important role of RCT in maintaining the cholesterol homeostasis, we hypothesised that persimmon tannin may regulate cholesterol metabolism by regulating LXRα, CYP7A1, ABCA1 and other genes related with RCT.