br Acknowledgement We like to thank the

Acknowledgement We like to thank the Austrian Federal Ministry of Science, Research and Economy for financial support (GZ402.000/00014-WF/V/6/2016 within the Sino-Austria project) as well as Andrea Szabo and Patricia Haiss for support regarding the drawing of figures and tables.
Farnesoid X Receptor (FXR), as a member of nuclear receptor superfamily, is a vital transcriptional factor encoded by in mouse and in human. In 1995, farnesol metabolites were identified as activators of FXR. Endogenous ligands of FXR were bile acids which were identified by three groups independently in 1999., , FXR is abundantly expressed in organs involved in the enterohepatic circulation of bile acids including liver and intestine. In addition to liver and intestine, FXR is also expressed in other tissues, such as the adrenal gland, kidney, stomach and adipocytes. FXR subfamily includes two members, FXRα and FXRβ. FXRβ, also known as NR1H5,encoded by which was pseudogene in humans, is not a bile acid-activated receptor. As the most dedicated bile acids receptor, FXR plays a pivotal role in the homeostasis of bile acids. Activation of FXR in the liver suppresses the synthesis of bile acids and reduces the bile acids pool size., , FXR controls the synthesis of bile acids transcriptional induction of the Camptothecin of fibroblast growth factor 19 (FGF19) and small heterodimer partner (SHP). In addition to the maintenance of bile acids homeostasis, FXR also takes control of lipids, glucose and cholesterol metabolism in the liver and intestine. In wild type but not in FXR-null mice, fasting-induced FXR expression led to decreased plasma triglyceride levels. In diabetic mice, activation of FXR by synthetic agonist improves hyperglycemia and hyperlipidemia. Obesity and insulin resistance are emerging as the major contributors of dysfunction or diseases of cardiac, vascular, liver and other system. There is an urgent demand for drug discovery to reduce obesity and insulin resistance. Over the past decade, FXR agonists have emerged in large numbers. Some endogenous bile acids including CDCA, DCA, LCA and CA are FXR agonists. In addition, several semi-synthetic bile acids were determined to be potent FXR agonists, such as 6-ECDCA and TC-100. Among the semi-synthetic FXR agonists, 6-ECDCA is the most exemplary one which has entered into a number of clinical trials, and has been approved for treatment of Primary Biliary Cholangitis. A number of synthetic FXR agonists have been reported, including fexaramine, GW4064, PX-102, XL335 and GSK2324., , , , Solution and solid-phase synthesis led to the discovery of Fex. Fex is poorly absorbed into circulation when delivered orally. In contrast to systemic agonism of FXR, Fex did not activate FXR downstream genes in the liver. Orally delivered Fex improved metabolic profile of high-fat diet induced obesity, including weight gain, increased insulin sensitization, decreased inflammation and browning of white adipose tissue. Gut-restricted FXR agonism led to whole-body benefits. These results suggested that intestinal FXR activation would be a promising and safer treatment for obesity, insulin resistance and metabolic syndrome. To further improve the intestinal-restricted property, a series of Fex derivatives were designed and synthesized by our group. Herein, we reported the Fex derivatives for the treatment of diet-induced obesity in mice with more potent gut-restricted FXR activation. The synthesis routes of these compounds were showed in scheme S1 and scheme S2. Firstly, we investigated the agonist effect of these compounds . We performed the experiments on Caco-2 and HepG-2 cells but the results showed no significant agonist effect on FXR (data not shown). We speculated that the two cell lines may not be suitable for detection of agonist effect on FXR. Then rat primary hepatocytes were utilized for study. We found that Fex-1 and Fex-2 had no agonist effect on rat primary hepatocytes. However, from , Fex-3 and Fex-4 could significantly promote the mRNA expression of BSEP and SHP and suppress CYP7A1, all of which are the target genes of FXR. From this results we supposed that the biphenyl group was very important as Fex-3 and Fex-4 kept this group but Fex-1 and Fex-2 had this group replaced by naphthoyl-group and this was consistence with the reported literature (). Compared with Fex, the results elucidated that Fex-3 and Fex-4 could also act as FXR agonists. As Fex-3 was a little better than Fex-4, we focus on Fex-3 in the following experiments. Through MTT assay, Fex-3 has no cell cytotoxicity even at 100μM ().