Natural products as modulators of the nuclear receptors and metabolic sensors LXR,FXR and RXR

Nuclear receptors (NRs) represent attractive targets for the treatment of metabolic syndrome-related diseases. In addition, natural products are an interesting pool of potential ligands since they have been refined under evolutionary pressure to interact with proteins or other biological targets.This review aims to briefly summarize current basic knowledge regarding the liver X (LXR) and farnesoid X receptors (FXR) that form permissive heterodimers with retinoid X receptors (RXR). Natural product-based ligands for these receptors are summarized and the potential of LXR, FXR and RXR as targets in precision medicine is discussed.     

Intake of stigmasterol and β-sitosterol alters lipid metabolism and alleviates NAFLD in mice fed a high-fat western-style diet

Objective

To investigate and compare the effects of two common dietary phytosterols, stigmasterol and β-sitosterol, in altering lipid metabolism and attenuating nonalcoholic fatty liver disease (NAFLD).

Post-transplant cholangiopathy: Classification,pathogenesis, and preventive strategies

Biliary complications are the most frequent cause of morbidity, re-transplantation, and even mortality after liver transplantation. In general, biliary leakage and anastomotic and non-anastomotic biliary strictures (NAS) can be recognized. There is no consensus on the exact definition of NAS and different names and criteria have been used in literature. We propose to use the term post-transplant cholangiopathy for the spectrum of abnormalities of large donor bile ducts, that includes NAS, but also intraductal casts and intrahepatic biloma formation, in the presence of a patent hepatic artery. Combinations of these manifestations of cholangiopathy are not infrequently found in the same liver and ischemia-reperfusion injury is generally considered the common underlying mechanism. Other factors that contribute to post-transplant cholangiopathy are biliary injury due to bile salt toxicity and immune-mediated injury. This review provides an overview of the various types of post-transplant cholangiopathy, the presumed pathogenesis, clinical implications, and preventive strategies.     

Ablating both Fabp1 and Scp2/Scpx (TKO) induces hepatic phospholipid and cholesterol accumulation in high fat-fed mice

Although singly ablating Fabp1 or Scp2/Scpx genes may exacerbate the impact of high fat diet (HFD) on whole body phenotype and non-alcoholic fatty liver disease (NAFLD), concomitant upregulation of the non-ablated gene, preference for ad libitum fed HFD, and sex differences complicate interpretation. Therefore, these issues were addressed in male and female mice ablated in both genes (Fabp1/Scp2/Scpx null or TKO) and pair-fed HFD. Wild-type (WT) males gained more body weight as fat tissue mass (FTM) and exhibited higher hepatic lipid accumulation than WT females. The greater hepatic lipid accumulation in WT males was associated with higher hepatic expression of enzymes in glyceride synthesis, higher hepatic bile acids, and upregulation of transporters involved in hepatic reuptake of serum bile acids. While TKO had little effect on whole body phenotype and hepatic bile acid accumulation in either sex, TKO increased hepatic accumulation of lipids in both, specifically phospholipid and cholesteryl esters in males and females and free cholesterol in females. TKO-induced increases in glycerides were attributed not only to complete loss of FABP1, SCP2 and SCPx, but also in part to sex-dependent upregulation of hepatic lipogenic enzymes. These data with WT and TKO mice pair-fed HFD indicate that: i) Sex significantly impacted the ability of HFD to increase body weight, induce hepatic lipid accumulation and increase hepatic bile acids; and ii) TKO exacerbated the HFD ability to induce hepatic lipid accumulation, regardless of sex, but did not significantly alter whole body phenotype in either sex.     

MDR3（ABCB4）、BSEP（ABCB11）和FIC1（ATP881）基因在人绒毛和正常妊娠胎盘组织表达的研究

目的检测肝脏胆盐载体FIC1（ATP881）、BSEP（ABCB11）和MDR3（ABCB4）在正常绒毛和胎盘组织中转录水平和蛋白水平的表达情况,探讨肝脏胆盐载体在人类胎盘胆汁酸排泌过程中的作用和功能。方法选择正常妊娠6～12周的孕妇（早孕组）15例和妊娠38～40周的孕妇（晚孕组）20例,采用实时定量逆转录一聚合酶链反应技术（realtimeRT．PCR）检测绒毛和胎盘组织中上3种载体的mRNA,采用免疫组织化学（S-P）法分别检测后两种载体蛋白在上述35例胎盘组织中的表达,并通过免疫印迹技术分析这两种载体在胎盘组织中的含量。结果在所有绒毛和胎盘组织中均检测到3种载体的mRNA。MDR3mRNA在正常绒毛中的表达量较低为（0．15±0．04）,正常晚期妊娠胎盘中表达量为（0．58±0．06）,两者比较有显著性差异（P〈0．05）。与早孕组相比,FIC1mRNA表达水平明显由（0．65±0．03）下降至（0．23±0．04）,差别有非常显著意义（P〈0．01）。而BSEPmRNA表达无改变（0．06±0．01和0．05±0．01）（P〉0．05）。MDR3蛋白、BSEP蛋白在正常绒毛和胎盘组织中均有表达,且两种载体在正常早孕绒毛及晚期妊娠胎盘分布范围基本一致,主要分布在绒毛合体滋养细胞母体面游离缘。MDR3、BSEP蛋白在绒毛和晚期妊娠胎盘中的表达趋势与其mRNA相似,MDR3蛋白Western印迹条带的光密度值为（11357±3618）（早孕组）和（46753±2834）（晚孕组）,两组比较有显著性差异（P〈0．05）。BSEP蛋白早孕组Western印迹条带的光密度值为（1296±436）,晚孕组为（1798±575）,两组比较差异无显著性（P〉0．05）。结论3种肝脏胆盐载体FIC1、MDR3和BSEP在正常绒毛和胎盘组织中均有表达,可能参与了胎盘胆汁酸的排泌功能。妊娠期间MDR3、FIC1和BSEPmRNA和蛋白表达发生变化,可能与胎儿生长发育的需要有关。     

Regulation of MRP2/ABCC2 and BSEP/ABCB11 Expression in Sandwich Cultured Human and Rat Hepatocytes Exposed to Inflammatory Cytokines TNF-α, IL-6, and IL-1β

In the present study MRP2/ABCC2 and BSEP/ABCB11 expression were investigated in sandwich cultured (SC) human and rat hepatocytes exposed to the proinflammatory cytokines. The investigation was also done in lipopolysaccharide (LPS)-treated rats. In SC human hepatocytes, both absolute protein and mRNA levels of MRP2/ABCC2 were significantly down-regulated by TNF-α, IL-6, or IL-1β. In contrast to mRNA decrease, which was observed for BSEP/ABCB11, the protein amount was significantly increased by IL-6 or IL-1β. A discrepancy between the change in BSEP/ABCB11 mRNA and protein levels was encountered in SC human hepatocytes treated with proinflammatory cytokines. In SC rat hepatocytes, Mrp2/Abcc2 mRNA was down-regulated by TNF-α and IL-6, whereas the protein level was decreased by all three cytokines. Down-regulations of both Bsep/Abcb11 mRNA and protein levels were found in SC rat hepatocytes exposed to TNF-α or IL-1β. Administration of LPS triggered the release of the proinflammatory cytokines and caused the decrease of Mrp2/Abcc2 and Bsep/Abcb11 protein in liver at 24 h post-treatment; however, the Mrp2 and Bsep protein levels rebounded at 48 h post-LPS treatment. In total, our results indicate that proinflammatory cytokines regulate the expression of MRP2/Mrp2 and BSEP/Bsep and for the first time demonstrate the differential effects on BSEP/Bsep expression between SC human and rat hepatocytes. Furthermore, the agreement between transporter regulation in vitro in SC rat hepatocytes and in vivo in LPS-treated rats during the acute response phase demonstrates the utility of in vitro SC hepatocyte models for predicting in vivo effects.     

Disruption of Stard10 gene alters the PPARα-mediated bile acid homeostasis

STARD10, a member of the steroidogenic acute regulatory protein (StAR)-related lipid transfer (START) protein family, is highly expressed in the liver and has been shown to transfer phosphatidylcholine. Therefore it has been assumed that STARD10 may function in the secretion of phospholipids into the bile. To help elucidate the physiological role of STARD10, we produced Stard10 knockout mice (Stard10^−/−) and studied their phenotype. Neither liver content nor biliary secretion of phosphatidylcholine was altered in Stard10^−/− mice. Unexpectedly, the biliary secretion of bile acids from the liver and the level of taurine-conjugated bile acids in the bile were significantly higher in Stard10^−/− mice than wild type (WT) mice. In contrast, the levels of the secondary bile acids were lower in the liver of Stard10^−/− mice, suggesting that the enterohepatic cycling is impaired. STARD10 was also expressed in the gallbladder and small intestine where the expression level of apical sodium dependent bile acid transporter (ASBT) turned out to be markedly lower in Stard10^−/− mice than in WT mice when measured under fed condition. Consistent with the above results, the fecal excretion of bile acids was significantly increased in Stard10^−/− mice. Interestingly, PPARα-dependent genes responsible for the regulation of bile acid metabolism were down-regulated in the liver of Stard10^−/− mice. The loss of STARD10 impaired the PPARα activity and the expression of a PPARα-target gene such as Cyp8b1 in mouse hepatoma cells. These results indicate that STARD10 is involved in regulating bile acid metabolism through the modulation of PPARα-mediated mechanism.