Alterations in Enterohepatic Fgf15 Signaling and Changes in Bile Acid Composition Depend on Localization of Murine Intestinal Inflammation

Protective effects and mechanism of Sangyu granule on acetaminophen-induced liver injury in mice

ETHNOPHARMACOLOGICAL RELEVANCE

The Sang Yu granule (SY), a traditional Chinese medicine prescription of Xijing Hospital, was developed based on the Guanyin powder in the classical prescription "Hong's Collection of Proven Prescriptions" and the new theory of modern Chinese medicine. It has been proved to have a certain therapeutic effect on drug-induced liver injury (DILI), but the specific mechanism of action is still unclear.

AIM OF STUDY

Aim of the study was to explore the effect of SangYu granule on treating drug-induced liver injury induced by acetaminophen in mice.

MATERIALS AND METHODS

The chemical composition of SY, serum, and liver tissue was analyzed using ultrahigh-performance liquid chromatography quadrupole time-of-flight mass spectrometry. To assess hepatic function, measurements were taken using kits for total bile acids, as well as serum AST, ALT, and ALP activity. Concentrations of IL-1β and TNF-α in serum were quantified using ELISA kits. Transcriptome Sequencing Analysis and 2bRAD-M microbial diversity analysis were employed to evaluate gene expression variance in liver tissue and fecal microbiota diversity among different groups, respectively. Western blotting was performed to observe differences in the activation levels of FXR, SHP, CYP7A1 and PPARα in the liver, and the levels of FXR and FGF-15 genes and proteins in the ileum of mice. Additionally, fecal microbiota transplantation (FMT) experiments were conducted to investigate the potential therapeutic effect of administering the intestinal microbial suspension from mice treated with SY on drug-induced liver injury.

RESULTS

SY treatment exhibited significant hepatoprotective effects in mice, effectively ameliorating drug-induced liver injury while concurrently restoring intestinal microbial dysbiosis. Furthermore, SY administration demonstrated a reduction in the concentration of total bile acids, the expression of FXR and SHP proteins in the liver was up-regulated, CYP7A1 protein was down-regulated, and the expressions of FXR and FGF-15 proteins in the ileum were up-regulated. However, no notable impact on PPARα was observed. Furthermore, results from FMT experiments indicated that the administration of fecal suspensions derived from mice treated with SY did not yield any therapeutic benefits in the context of drug-induced liver injury.

CONCLUSION

The aforementioned findings strongly suggest that SY exerts a pronounced ameliorative effect on drug-induced liver injury through its ability to modulate the expression of key proteins involved in bile acid secretion, thereby preserving hepato-enteric circulation homeostasis.

Regulatory effect of Yinchenhao decoction on bile acid metabolism to improve the inflammatory microenvironment of hepatocellular carcinoma in mice

Hepatocellular carcinoma (HCC) is a malignant tumor with extremely high mortality. The tumor microenvironment is the "soil" of its occurrence and development, and the inflammatory microenvironment is an important part of the "soil". Bile acid is closely related to the occurrence of HCC. Bile acid metabolism disorder is not only directly involved in the occurrence and development of HCC but also affects the inflammatory microenvironment of HCC. Yinchenhao decoction, a traditional Chinese medicine formula, can regulate bile acid metabolism and may affect the inflammatory microenvironment of HCC. To determine the effect of Yinchenhao decoction on bile acid metabolism in mice with HCC and to explore the possible mechanism by which Yinchenhao decoction improves the inflammatory microenvironment of HCC by regulating bile acid metabolism, we established mice model of orthotopic transplantation of hepatocellular carcinoma. These mice were treated with three doses of Yinchenhao decoction, then liver samples were collected and tested. Yinchenhao decoction can regulate the disorder of bile acid metabolism in liver cancer mice. Besides, it can improve inflammatory reactions, reduce hepatocyte degeneration and necrosis, and even reduce liver weight and the liver index. Taurochenodeoxycholic acid, hyodeoxycholic acid, and taurohyodeoxycholic acid are important molecules in the regulation of the liver inflammatory microenvironment, laying a foundation for the regulation of the liver tumor inflammatory microenvironment based on bile acids. Yinchenhao decoction may improve the inflammatory microenvironment of mice with HCC by ameliorating hepatic bile acid metabolism.

Animal models of inflammatory bowel disease: category and evaluation indexes

Inflammatory bowel disease (IBD) research often relies on animal models to study the etiology, pathophysiology, and management of IBD. Among these models, rats and mice are frequently employed due to their practicality and genetic manipulability. However, for studies aiming to closely mimic human pathology, non-human primates such as monkeys and dogs offer valuable physiological parallels. Guinea pigs, while less commonly used, present unique advantages for investigating the intricate interplay between neurological and immunological factors in IBD. Additionally, New Zealand rabbits excel in endoscopic biopsy techniques, providing insights into mucosal inflammation and healing processes. Pigs, with their physiological similarities to humans, serve as ideal models for exploring the complex relationships between nutrition, metabolism, and immunity in IBD. Beyond mammals, non-mammalian organisms including zebrafish, Drosophila melanogaster, and nematodes offer specialized insights into specific aspects of IBD pathology, highlighting the diverse array of model systems available for advancing our understanding of this multifaceted disease. In this review, we conduct a thorough analysis of various animal models employed in IBD research, detailing their applications and essential experimental parameters. These include clinical observation, Disease Activity Index score, pathological assessment, intestinal barrier integrity, fibrosis, inflammatory markers, intestinal microbiome, and other critical parameters that are crucial for evaluating modeling success and drug efficacy in experimental mammalian studies. Overall, this review will serve as a valuable resource for researchers in the field of IBD, offering insights into the diverse array of animal models available and their respective applications in studying IBD.

Low-dose nano-gel incorporated with bile acids enhanced pharmacology of surgical implants

Aim: Major challenges to islet transplantation in Type 1 diabetes include host-inflammation, which results in failure to maintain survival and functions of transplanted islets. Therefore, this study investigated the applications of encapsulating the bile acid ursodeoxycholic acid (UDCA) with transplanted islets within improved nano-gel systems for Type 1 diabetes treatment. Materials & methods: Islets were harvested from healthy mice, encapsulated using UDCA-nano gel and transplanted into the diabetic mice, while the control group was transplanted encapsulated islets without UDCA. The two groups' survival plot, blood glucose, and inflammation and bile acid profiles were analyzed. Results & conclusion: UDCA-nano gel enhanced survival, glycemia and normalized bile acids' profile, which suggests improved islets functions and potential adjunct treatment for insulin therapy.

Intermittent Fasting Alleviates Risk Markers in a Murine Model of Ulcerative Colitis by Modulating the Gut Microbiome and Metabolome

Clinical trials have demonstrated the health benefits of intermittent fasting (IF). However, the potential mechanism of IF in alleviating dextran sulfate sodium (DSS)-induced colitis is not fully understood. The present study was mainly designed to explore the dynamic changes in the gut microbiota and metabolome after short-term (2 weeks) or long-term (20 weeks) IF and therefore clarify the potential mechanisms by which IF ameliorates DSS-induced colitis in a murine model. Thirty-two C57BL/6 male mice were equally divided into four groups and underwent IF intervention for 2 weeks (SIF group, n = 8), 20 weeks (LIF group, n = 8), or were allowed free access to food for 2 weeks (SAL group, n = 8) or 20 weeks (LAL group, n = 8). The thirty-two C57BL/6 male mice were accepted for the diet intervention of 2 weeks of IF or fed ad libitum. Colitis was induced by drinking 2% DSS for 7 days. Our findings showed that short-term IF prominently elevates the abundance of Bacteroides, Muibaculum and Akkermansia (p < 0.001, p < 0.001, p < 0.001, respectively), and decreased the abundance of Ruminiclostridium (p < 0.05). Long-term IF, however, decreased the abundance of Akkermansia and obviously increased the abundance of Lactobacillus (p < 0.05, p < 0.001, respectively). Metabolites mainly associated with nucleoside, carbohydrate, amino acid, bile acid, fatty acid, polyol, steroid and amine metabolism were identified in the faeces using untargeted GC/MS. In particular, inosine was extremely enriched after short-term IF and long-term IF (p < 0.01, p < 0.01, respectively); butyrate, 2-methyl butyric acid and valeric acid were significantly decreased after short-term IF (p < 0.001, p < 0.001, p < 0.01, respectively); and 2-methyl butyric acid was significantly increased after long-term IF (p < 0.001). The abundance of lithocholic acid (LCA), one of the secondary bile acids, increased significantly after short-term and long-term IF based on UPLC−MS/MS (p < 0.001, p < 0.5, respectively). Of note, IF markedly mitigated DSS-induced acute colitis symptoms and down-regulated pro-inflammatory cytokines IL-1α, IL-6, keratinocyte-derived chemokine (KC) and G-CSF levels in the serum (p < 0.01, p < 0.001, p < 0.05, p < 0.001, respectively). Furthermore, a correlation analysis indicated that the disease activity index (DAI) score and serum levels of IL-1α, IL-6, KC, and G-CSF were negatively correlated with the relative abundance of Akkermansia and the faecal metabolites LCA and inosine. This study confirmed that IF altered microbiota and reprogramed metabolism, which was a promising development in the attempt to prevent DSS-induced colitis. Moreover, our findings provide new insights regarding the correlations among the mucosal barrier dysfunction, metabolome, and microbiome.

Role of metabolites derived from gut microbiota in inflammatory bowel disease

Over the past two decades, it is improved gut microbiota plays an important role in the health and disease pathogenesis. Metabolites, small molecules produced as intermediate or end products of microbial metabolism, is considered as one of the major interaction way for gut microbiota with the host. Bacterial metabolisms of dietary substrates, modification of host molecules or bacteria are the major source of metabolites. Signals from microbial metabolites affect immune maturation and homeostasis, host energy metabolism as well as mucosal integrity maintenance. Based on many researches, the composition and function of the microbiota can be changed, which is also seen in the metabolite profiles of patients with inflammatory bowel disease (IBD). Additionally, some specific classes of metabolites also can trigger IBD. In this paper, definition of the key classes of microbial-derived metabolites which are changed in IBD, description of the pathophysiological basis of association and identification of the precision therapeutic modulation in the future are the major contents.

Role of metabolites derived from gut microbiota in inflammatory bowel disease

Over the past two decades, it is improved gut microbiota plays an important role in the health and disease pathogenesis. Metabolites, small molecules produced as intermediate or end products of microbial metabolism, is considered as one of the major interaction way for gut microbiota with the host. Bacterial metabolisms of dietary substrates, modification of host molecules or bacteria are the major source of metabolites. Signals from microbial metabolites affect immune maturation and homeostasis, host energy metabolism as well as mucosal integrity maintenance. Based on many researches, the composition and function of the microbiota can be changed, which is also seen in the metabolite profiles of patients with inflammatory bowel disease (IBD). Additionally, some specific classes of metabolites also can trigger IBD. In this paper, definition of the key classes of microbial-derived metabolites which are changed in IBD, description of the pathophysiological basis of association and identification of the precision therapeutic modulation in the future are the major contents.

Understanding the hepatoxicity of inorganic mercury through guts: Perturbance to gut microbiota, alteration of gut-liver axis related metabolites and damage to gut integrity

Mercury (Hg) brings adverse effects to the environment and human beings and inorganic mercury (IHg) is a typical hepatic toxin. This work studied the impacts of IHg on gut microbes and metabolome together with its damage to liver and gut in rats through gut microbiome, metabolomics and metallomics. Sprague Dawley (SD) rats were orally exposed to 0.4 μg/mL IHg and sacrificed after 24 h. It was found that IHg perturbed greatly on the gut microbiota, such as increased pathogenic bacteria like G. bacillus. In addition, IHg also changed gut-liver axis related metabolites, which was confirmed by the secretion of a large number of inflammatory factors in both the gut and the liver. The changed gut-liver axis related metabolites correlated well to the changes of gut microbiome. In all, besides the direct deposition in liver of Hg, the perturbance to gut microbiome and alteration of gut-liver axis related metabolites by IHg also contributed to its hepatoxicity, which provides new insights about the hepatoxicity of chemicals. The strategy applied in this work may also be used to understand the hepatoxicity of other chemicals.

The Pathophysiology of Farnesoid X Receptor (FXR) in the GI Tract: Inflammation, Barrier Function and Innate Immunity

The Farnesoid-X Receptor, FXR, is a nuclear bile acid receptor. Its originally described function is in bile acid synthesis and regulation within the liver. More recently, however, FXR has been increasingly appreciated for its breadth of function and expression across multiple organ systems, including the intestine. While FXR’s role within the liver continues to be investigated, increasing literature indicates that FXR has important roles in responding to inflammation, maintaining intestinal epithelial barrier function, and regulating immunity within the gastrointestinal (GI) tract. Given the complicated and multi-factorial nature of intestinal barrier dysfunction, it is not surprising that FXR’s role appears equally complicated and not without conflicting data in different model systems. Recent work has suggested translational applications of FXR modulation in GI pathology; however, a better understanding of FXR physiology is necessary for these treatments to gain widespread use in human disease. This review aims to discuss current scientific work on the role of FXR within the GI tract, specifically in its role in intestinal inflammation, barrier function, and immune response, while also exploring areas of controversy.

Barley Leaf Insoluble Dietary Fiber Alleviated Dextran Sulfate Sodium-Induced Mice Colitis by Modulating Gut Microbiota

Supplementation of dietary fiber has been proved to be an effective strategy to prevent and relieve inflammatory bowel disease (IBD) through gut microbiota modulation. However, more attention has been paid to the efficacy of soluble dietary fiber than that of insoluble dietary fiber (IDF). In the present study, we investigated whether IDF from barley leaf (BLIDF) can inhibit gut inflammation via modulating the intestinal microbiota in DSS-induced colitis mice. The mice were fed 1.52% BLIDF-supplemented diet for 28 days. Results demonstrated that feeding BLIDF markedly mitigated DSS-induced acute colitis symptoms and down-regulated IL-6, TNF-α, and IL-1β levels in the colon and serum of colitis mice. BLIDF supplementation effectively reduced the abundance of Akkermansia and increased the abundance of Parasutterella, Erysipelatoclostridium, and Alistipes. Importantly, the anti-colitis effects of BLIDF were abolished when the intestinal microbiota was depleted by antibiotics. Furthermore, the targeted microbiota-derived metabolites analysis suggested that BLIDF feeding can reverse the DSS-induced decline of short-chain fatty acids and secondary bile acids in mice feces. Finally, BLIDF supplementation elevated the expression of occludin and mucin2, and decreased the expression of claudin-1 in colons of DSS-treated mice. Overall, our observations suggest that BLIDF exerts anti-inflammatory effects via modulating the intestinal microbiota composition and increasing the production of microbiota-derived metabolites.

Bile Acids and Microbiota: Multifaceted and Versatile Regulators of the Liver-Gut Axis

After their synthesis from cholesterol in hepatic tissues, bile acids (BAs) are secreted into the intestinal lumen. Most BAs are subsequently re-absorbed in the terminal ileum and are transported back for recycling to the liver. Some of them, however, reach the colon and change their physicochemical properties upon modification by gut bacteria, and vice versa, BAs also shape the composition and function of the intestinal microbiota. This mutual interplay of both BAs and gut microbiota regulates many physiological processes, including the lipid, carbohydrate and energy metabolism of the host. Emerging evidence also implies an important role of this enterohepatic BA circuit in shaping mucosal colonization resistance as well as local and distant immune responses, tissue physiology and carcinogenesis. Subsequently, disrupted interactions of gut bacteria and BAs are associated with many disorders as diverse as Clostridioides difficile or Salmonella Typhimurium infection, inflammatory bowel disease, type 1 diabetes, asthma, metabolic syndrome, obesity, Parkinson’s disease, schizophrenia and epilepsy. As we cannot address all of these interesting underlying pathophysiologic mechanisms here, we summarize the current knowledge about the physiologic and pathogenic interplay of local site microbiota and the enterohepatic BA metabolism using a few selected examples of liver and gut diseases.

IBD and Bile Acid Absorption: Focus on Pre-clinical and Clinical Observations

Inflammatory bowel disease (IBD) causes chronic inflammation affecting the GI tract. It is classified as consisting of Crohn’s Disease (CD) and Ulcerative Colitis (UC). Bile Acid absorption is altered in both pre-clinical models of Inflammatory Bowel Disease (IB) and in human IBD. The bile acid transporter apical sodium dependent bile acid transporter (ASBT) showed decreased expression in rats with TNBS colitis. Decreased ASBT expression has also been described in murine, canine and rabbit models of intestinal inflammation. Human IBD studies have shown that an inflamed ileum can interrupt enterohepatic recirculation of bile acid, which could be due to inflammatory cytokine induced repression of the ASBT promoter. There are different hypotheses as to why ASBT is downregulated during CD. In addition, one study has demonstrated the beneficial effect of a glucocorticoid on ASBT expression, when treating IBD. Our aim in this paper was to systematically review various aspects of bile acid malabsorption in animal models of intestinal inflammation, as well as in IBD.

Fibroblast Growth Factor 19 modulates intestinal microbiota and inflammation in presence of Farnesoid X Receptor

BACKGROUND

Disruption of bile acid (BA) homeostasis plays a key role in intestinal inflammation. The gut-liver axis is the main site for the regulation of BA synthesis and BA pool size via the combined action of the nuclear Farnesoid X Receptor (FXR) and the enterokine Fibroblast Growth Factor 19 (FGF19). Increasing evidence have linked derangement of BA metabolism with dysbiosis and mucosal inflammation. Thus, here we aimed to investigate the potential action of an FGF19 analogue on intestinal microbiota and inflammation.

METHODS

A novel engineered non-tumorigenic variant of the FGF19 protein, M52-WO 2016/0168219 was generated. WT and FXRnull mice were injected with AAV-FGF19-M52 or the control AAV-GFP and subjected to Sodium Dextran Sulphate-induced colitis.

FINDINGS

FGF19-M52 reduced BA synthesis and pool size, modulated its composition and protected mice from intestinal inflammation. These events were coupled with preservation of the intestinal epithelial barrier integrity, inhibition of inflammatory immune response and modulation of microbiota composition. Interestingly, FGF19-M52-driven systemic and local anti-inflammatory activity was completely abolished in Farnesoid X Receptor (FXR)null mice, thus underscoring the need of FXR to guarantee enterocytes' fitness and complement FGF19 anti-inflammatory activity. To provide a translational perspective, we also show that circulating FGF19 levels are reduced in patients with Crohn's disease.

INTERPRETATION

Reactivation of the FXR-FGF19 axis in a murine model of intestinal inflammation could bona fide provide positive changes in BA metabolism with consequent reduction of intestinal inflammation and modulation of microbiota. These results point to the therapeutic potential of FGF19 in the treatment of intestinal inflammation with concomitant derangement of BA homeostasis.

FUNDING

A. Moschetta is funded by MIUR-PRIN 2017 <- 2017J3E2W2; Italian Association for Cancer Research (AIRC, IG 23239); Interreg V-A Greece-Italy 2014-2020-SILVER WELLBEING, MIS5003627; HDHL-INTIMIC EuJPI-FATMAL; MIUR PON "R&I" 2014-2020-ARS01_01220. No money has been paid by NGM Biopharmaceuticals or any other agency to write this article.

Impaired Intestinal Farnesoid X Receptor Signaling in Cystic Fibrosis Mice

BACKGROUND & AIMS

The bile acid (BA)-activated farnesoid X receptor (FXR) controls hepatic BA synthesis and cell proliferation via the intestinal hormone fibroblast growth factor 19. Because cystic fibrosis (CF) is associated with intestinal dysbiosis, anomalous BA handling, and biliary cirrhosis, we investigated FXR signaling in CF.

METHODS

Intestinal and hepatic expression of FXR target genes and inflammation markers was assessed in Cftr null mice and controls. Localization of the apical sodium-dependent BA transporter was assessed, and BAs in gastrointestinal tissues were analyzed. The CF microbiota was characterized and FXR signaling was investigated in intestinal tissue and organoids.

RESULTS

Ileal murine fibroblast growth factor 19 ortholog (Fgf15) expression was strongly reduced in CF mice, compared with controls. Luminal BA levels and localization of apical sodium-dependent BA transporter was not affected, and BAs induced Fgf15 up to normal levels in CF ileum, ex vivo, and CF organoids. CF mice showed a dysbiosis that was associated with a marked up-regulation of genes involved in host-microbe interactions, including those involved in mucin glycosylation, antimicrobial defense, and Toll-like receptor signaling. Antibiotic treatment reversed the up-regulation of inflammatory markers and restored intestinal FXR signaling in CF mice. Conversely, FXR-dependent gene induction in ileal tissue and organoids was repressed by bacterial lipopolysaccharide and proinflammatory cytokines, respectively. Loss of intestinal FXR activity was associated with a markedly blunted hepatic trophic response to oral BA supplementation, and with impaired repression of Cyp7a1, the gene encoding the rate-limiting enzyme in BA synthesis.

CONCLUSIONS

In CF mice, the gut microbiota represses intestinal FXR activity, and, consequently, FXR-dependent hepatic cell proliferation and feedback control of BA synthesis.

FXR agonist GW4064 improves liver and intestinal pathology and alters bile acid metabolism in rats undergoing small intestinal resection

Mortality associated with liver disease has been observed in patients with short bowel syndrome (SBS); however, its mechanism remains unclear, but bile acid (BA) dysmetabolism has been proposed as a possible cause. The farnesoid X receptor (FXR) is the key regulator of BA synthesis. Here, we showed that, in a rat model of short bowel resection associated with liver disease (SBR-ALD), the BA composition of hepatic tissues reflected a larger proportion of primary and secondary unconjugated BAs, whereas that of the colon contents and serum showed an increased ratio of secondary unconjugated BAs. Both hepatic and intestinal regulation of BA synthesis was characterized by a blunted hepatic FXR activation response. The mRNA expression levels of cholesterol 7a-hydroxylase (CYP7A1), sterol 12a-hydroxylase (CYP8B1), and sterol 27 hydroxylase (CYP27A1), the key enzymes in BA synthesis, were upregulated. After intervention with the FXR agonist GW4064, both the liver histology and serum transaminase activity were improved, which demonstrated the attenuation of SBR-ALD. The BA compositions of hepatic tissue, the colon contents, and serum recovered and were closer to those of the sham group. The expression levels of hepatic FXR increased, and its target genes were activated. Consistent with this, the expression levels of CYP7A1, CYP8B1, and CYP27A1 were downregulated. Ileum tissue FXR and its target genes were slightly elevated. This study showed that the FXR agonist GW4064 could correct BA dysmetabolism to alleviate hepatotoxicity in SBR animals. GW4064 intervention resulted in a decrease in fecal bile excretion and elevated plasma/hepatic conjugated BA levels. GW4064 increased the reabsorption of conjugated BAs by inducing apical sodium-dependent bile salt transporter expression in the ileum. Concomitantly, FXR activation in the presence of GW4064 decreased BA production by repressing the expression of key synthetases, including CYP7A1, CYP8B1, and CYP27A1. These findings provide a clinical research direction for the prevention of liver disease in patients with SBS.NEW & NOTEWORTHY This study assessed the impact of treatment with GW4064, a farnesoid X receptor agonist, on the development of short bowel resection (SBR) associated with liver disease in a rat model of SBR. GW4064 was able to correct bile acid dysmetabolism and alleviate hepatotoxicity in SBR animals.

Guts and Gall: Bile Acids in Regulation of Intestinal Epithelial Function in Health and Disease

Epithelial cells line the entire surface of the gastrointestinal tract and its accessory organs where they primarily function in transporting digestive enzymes, nutrients, electrolytes, and fluid to and from the luminal contents. At the same time, epithelial cells are responsible for forming a physical and biochemical barrier that prevents the entry into the body of harmful agents, such as bacteria and their toxins. Dysregulation of epithelial transport and barrier function is associated with the pathogenesis of a number of conditions throughout the intestine, such as inflammatory bowel disease, chronic diarrhea, pancreatitis, reflux esophagitis, and cancer. Driven by discovery of specific receptors on intestinal epithelial cells, new insights into mechanisms that control their synthesis and enterohepatic circulation, and a growing appreciation of their roles as bioactive bacterial metabolites, bile acids are currently receiving a great deal of interest as critical regulators of epithelial function in health and disease. This review aims to summarize recent advances in this field and to highlight how bile acids are now emerging as exciting new targets for disease intervention.

Fibroblast Growth Factor 15/19: From Basic Functions to Therapeutic Perspectives

Discovered 20 years ago, fibroblast growth factor (FGF)19, and its mouse ortholog FGF15, were the first members of a new subfamily of FGFs able to act as hormones. During fetal life, FGF15/19 is involved in organogenesis, affecting the development of the ear, eye, heart, and brain. At adulthood, FGF15/19 is mainly produced by the ileum, acting on the liver to repress hepatic bile acid synthesis and promote postprandial nutrient partitioning. In rodents, pharmacologic doses of FGF19 induce the same antiobesity and antidiabetic actions as FGF21, with these metabolic effects being partly mediated by the brain. However, activation of hepatocyte proliferation by FGF19 has long been a challenge to its therapeutic use. Recently, genetic reengineering of the molecule has resolved this issue. Despite a global overlap in expression pattern and function, murine FGF15 and human FGF19 exhibit several differences in terms of regulation, molecular structure, signaling, and biological properties. As most of the knowledge originates from the use of FGF19 in murine models, differences between mice and humans in the biology of FGF15/19 have to be considered for a successful translation from bench to bedside. This review summarizes the basic knowledge concerning FGF15/19 in mice and humans, with a special focus on regulation of production, morphogenic properties, hepatocyte growth, bile acid homeostasis, as well as actions on glucose, lipid, and energy homeostasis. Moreover, implications and therapeutic perspectives concerning FGF19 in human diseases (including obesity, type 2 diabetes, hepatic steatosis, biliary disorders, and cancer) are also discussed.

Pharmacological effects of nanoencapsulation of human-based dosing of probucol on ratio of secondary to primary bile acids in gut, during induction and progression of type 1 diabetes

INTRODUCTION

The ratio of secondary to primary bile acids changes during Type 1 Diabetes (T1D) development and these effects might be ameliorated by using cholesterol lowering drugs or hydrophilic bile acids. Probucol is a cholesterol-lowering drug, while ursodeoxycholic acid is a hydrophilic bile acid. This study investigated whether nanoencapsulated probucol with ursodeoxycholic acid altered bile acid ratios and the development of diabetes.

METHODS

Balb/c mice were divided into three groups and gavaged daily with either free probucol, nanoencapsulated probucol or nanoencapsulated probucol with ursodeoxycholic acid for seven days. Alloxan was injected and once T1D was confirmed the mice continued to receive daily gavages until euthanasia. Blood, tissues, faeces and urine were collected for analysis of insulin and bile acids.

RESULTS AND CONCLUSIONS

Nanoencapsulated probucol-ursodeoxycholic acid resulted in significant levels of insulin in the blood, lower levels of secondary bile acids in liver and lower levels of primary bile acids in brain, while ratio of secondary to primary bile acids remains similar among all groups, except in the faeces. Findings suggests that nanoencapsulated probucol-ursodeoxycholic acid may exert a protective effect on pancreatic β-cells and reserve systemic insulin load via modulation of bile acid concentrations in the liver and brain.

Interaction of glucocorticoids with FXR/FGF19/FGF21-mediated ileum-liver crosstalk

At high doses, glucocorticoids (GC) have been associated with enhanced serum bile acids and liver injury. We have evaluated the effect of GC, in the absence of hepatotoxicity, on FXR/FGF91(Fgf15)/FGF21-mediated ileum-liver crosstalk. Rats and mice (wild type and Fxr^-/-, Fgf15^-/- and int-Gr^-/- strains; the latter with GC receptor (Gr) knockout selective for intestinal epithelial cells), were treated (i.p.) with dexamethasone, prednisolone or budesonide. In both species, high doses of GC caused hepatotoxicity. At a non-hepatotoxic dose, GC induced ileal Fgf15 down-regulation and liver Fgf21 up-regulation, without affecting Fxr expression. Fgf21 mRNA levels correlated with those of several genes involved in glucose and bile acid metabolism. Surprisingly, liver Cyp7a1 was not up-regulated. The expression of factors involved in transcriptional modulation by Fxr and Gr (p300, Drip205, CBP and Smrt) was not affected. Pxr target genes Cyp3a11 and Mrp2 were not up-regulated in liver or intestine. In contrast, the expression of some Pparα target genes in liver (Fgf21, Cyp4a14 and Vanin-1) and intestine (Vanin-1 and Cyp3a11) was altered. In mice with experimental colitis, liver Fgf21 was up-regulated (4.4-fold). HepG2 cells transfection with FGF21 inhibited CYP7A1 promoter (prCYP7A1-Luc2). This was mimicked by pure human FGF21 protein or culture in medium previously conditioned by cells over-expressing FGF21. This response was not abolished by deletion of a putative response element for phosphorylated FGF21 effectors present in prCYP7A1. In conclusion, GC interfere with FXR/FGF19-mediated intestinal control of CYP7A1 expression by the liver and stimulate hepatic secretion of FGF21, which inhibits CYP7A1 promoter through an autocrine mechanism.

Whole-Blood Taurine Concentrations in Cats With Intestinal Disease

Background

Increased delivery of taurine‐conjugated bile acids to the distal bowel can lead to dysbiosis resulting in colitis in mouse models of inflammatory bowel disease. A similar situation also could occur in cats with intestinal disease and might therefore result in decreased whole‐body taurine concentration.

Hypothesis/Objectives

To determine whether whole‐blood taurine concentrations are decreased at the time of diagnosis in cats with intestinal disease and to correlate concentrations with clinical and laboratory variables.

Animals

Twenty‐one cats with chronic inflammatory enteropathy and 7 cats with intestinal neoplasia from the University of Bristol.

Methods

Cats that had undergone a thorough investigation consisting of a CBC, serum biochemistry, serum cobalamin and folate concentrations, transabdominal ultrasound examination and histopathology of intestinal biopsy specimens, as well as additional testing if indicated, were included. Whole‐blood from these cats collected at the time of histologic diagnosis and stored in ethylenediaminetetraacetic acid was retrospectively analyzed for taurine with an automated high‐performance liquid chromatography amino acid analyzer.

Results

Although whole‐blood taurine concentrations remained within the reference range, those cats with predominantly large intestinal clinical signs had significantly lower concentrations than did cats with small intestinal and mixed bowel clinical signs (P = 0.033) and this difference also was significant when assessed only in cats with chronic inflammatory enteropathy (P = 0.019).

Conclusions and Clinical Importance

Additional studies are needed to determine whether large intestinal signs in cats with chronic inflammatory enteropathy are caused by alterations in the microbiota arising as a consequence of increased delivery of taurine‐conjugated bile acids.