Intestinal Farnesoid X Receptor Modulates Duodenal Surface Area but Does Not Control Glucose Absorption in Mice.

Bile acids facilitate the intestinal absorption of dietary lipids and act as signalling molecules in the maintenance of metabolic homeostasis. Farnesoid X receptor (FXR) is a bile acid-responsive nuclear receptor involved in bile acid metabolism, as well as lipid and glucose homeostasis. Several studies have suggested a role of FXR in the control of genes regulating intestinal glucose handling. We applied a novel dual-label glucose kinetic approach in intestine-specific FXR-/- mice (iFXR-KO) to directly assess the role of intestinal FXR in glucose absorption. Although iFXR-KO mice showed decreased duodenal expression of hexokinase 1 (Hk1) under obesogenic conditions, the assessment of glucose fluxes in these mice did not show a role for intestinal FXR in glucose absorption. FXR activation with the specific agonist GS3972 induced Hk1, yet the glucose absorption rate remained unaffected. FXR activation increased the duodenal villus length in mice treated with GS3972, while stem cell proliferation remained unaffected. Accordingly, iFXR-KO mice on either chow, short or long-term HFD feeding displayed a shorter villus length in the duodenum compared to wild-type mice. These findings indicate that delayed glucose absorption reported in whole-body FXR-/- mice is not due to the absence of intestinal FXR. Yet, intestinal FXR does have a role in the small intestinal surface area.

Emerging roles of bile acids in control of intestinal functions.

PURPOSE OF REVIEW: Bile acids and their signalling pathways are increasingly recognized as potential therapeutic targets for several diseases. This review summarizes new insights in bile acid physiology, focussing on regulatory roles of bile acids in intestinal functions. RECENT FINDINGS: Recent studies have highlighted the interactions between bile acids and gut microbiome: interfering with microbiome composition may be beneficial in treatment of liver and metabolic diseases by modulating bile acid composition, as different bile acid species have different signalling functions. In the intestine, bile acid receptors FXR, VDR and TGR5 are involved in control of barrier function, paracellular ion transport and hormone release. Specific microbial bile acid metabolites modulate immune responses of the host. In addition, new functions of bile acids in regulation of gastric emptying and satiation via brain-gut-liver axis have been discovered. Identification of Cyp2c70 as the enzyme responsible for generation of hydrophilic mouse/rat-specific muricholic acids has allowed the generation of murine models with a human-like bile acid composition. SUMMARY: Specific bile acids act as important signalling molecules affecting whole body metabolism, specific transport processes and immunity in different segments of the intestinal tract. Their relevance for human (patho)physiology is emerging. Novel mouse models with human-like bile acid composition will aid to accelerate translational research.

FXR overexpression alters adipose tissue architecture in mice and limits its storage capacity leading to metabolic derangements.

The bile acid-activated nuclear receptor, FXR (NR1H4), has been implicated in the control of lipid and energy metabolism, but its role in fat tissue, where it is moderately expressed, is not understood. In view of the recent development of FXR-targeting therapeutics for treatment of human metabolic diseases, understanding the tissue-specific actions of FXR is essential. Transgenic mice expressing human FXR in adipose tissue (aP2-hFXR mice) at three to five times higher levels than endogenous Fxr, i.e., much lower than its expression in liver and intestine, have markedly enlarged adipocytes and show extensive extracellular matrix remodeling. Ageing and exposure to obesogenic conditions revealed a strongly limited capacity for adipose expansion and development of fibrosis in adipose tissues of aP2-hFXR transgenic mice. This was associated with impaired lipid storage capacity, leading to elevated plasma free fatty acids and ectopic fat deposition in liver and muscle as well as whole-body insulin resistance. These studies establish that adipose FXR is a determinant of adipose tissue architecture and contributes to whole-body lipid homeostasis.

Bile acids and Farnesoid X Receptor in renal pathophysiology.

BACKGROUND: Bile acids (BAs) act not only as lipids and lipid-soluble vitamin detergents but also function as signaling molecules, participating in diverse physiological processes. The identification of BA receptors in organs beyond the enterohepatic system, such as the Farnesoid X Receptor (FXR), has initiated inquiries into their organ-specific functions. Among these organs, the kidney prominently expresses FXR. SUMMARY: This review provides a comprehensive overview of various BA species identified in kidneys and delves into the roles of renal apical and basolateral BA transporters. Furthermore, we explore changes in BAs and their potential implications in various renal diseases, particularly in chronic kidney diseases (CKD). Lastly, we center our discussion on FXR, a key BA receptor in the kidney and a potential therapeutic target for renal diseases, providing current insights into the protective mechanisms associated with FXR agonist treatments. KEY MESSAGES: Despite the relatively low concentrations of BAs in the kidney, their presence is noteworthy, with rodents and humans exhibiting distinct renal BA compositions. Renal BA transporters efficiently facilitate either reabsorption into systemic circulation or excretion into the urine. However, adaptive changes in BA transporters are evident during cholestasis. Various renal diseases are accompanied by alterations in BA concentrations and FXR expression. Consequently, the activation of FXR in the kidney could be a promising target for mitigating kidney damage.

Quantitative Profiling of Bile Acids in Feces of Humans and Rodents by Ultra-High-Performance Liquid Chromatography-Quadrupole Time-of-Flight Mass Spectrometry.

A simple, sensitive, and reliable quantification and identification method was developed and validated for simultaneous analysis of 58 bile acids (BAs) in human and rodent (mouse and rat) fecal samples. The method involves an extraction step with a 5% ammonium-ethanol aqueous solution; the BAs were quantified by high-resolution mass spectrometry (ultra-high-performance liquid chromatography coupled with quadrupole-time-of-flight mass spectrometry, UPLC-Q-TOF). The recoveries were 80.05-120.83%, with coefficient variations (CVs) of 0.01-9.82% for three biological species. The limits of detection (LODs) were in the range of 0.01-0.24 µg/kg, and the limits of quantification (LOQs) ranged from 0.03 to 0.81 µg/kg. In addition, the analytical method was used to identify and quantify BAs in end-stage renal disease (ESRD) patients, C57BL/6 mice, and Sprague-Dawley (SD) rats. The fecal BA profile and analysis of BA indices in these samples provide valuable information for further BA metabolic disorder research.

Effect of Different Solvents on the Measurement of Phenolics and the Antioxidant Activity of Mulberry (Morus atropurpurea Roxb.) with Accelerated Solvent Extraction.

The effects of 9 different solvents on the measurement of the total phenolics and antioxidant activities of mulberry fruits were studied using accelerated solvent extraction (ASE). Sixteen to 22 types of phenolics (flavonols, flavan-3-ols, flavanol, hydroxycinnamic acids, hydroxybenzoic acids, and stilbenes) from different mulberry extracts were characterized and quantified using HPLC-MS/MS. The principal component analysis (PCA) was used to determine the suitable solvents to distinguish between different classes of phenolics. Additionally, the phenolic extraction abilities of ASE and ultrasound-assisted extraction (UAE) were compared. The highest extraction efficiency could be achieved by using 50% acidified methanol (50MA) as ASE solvents with 15.14 mg/gallic acid equivalents g dry weight of mulberry fruit. The PCA results revealed that the 50MA followed by 50% acidified acetone (50AA) was the most efficient solvent for the extraction of phenolics, particularly flavonols (627.12 and 510.31 µg/g dry weight, respectively), while water (W) was not beneficial to the extraction of all categories of phenolics. Besides, the results of 3 antioxidant capability assays (DPPH, ABTS free radical-scavenging assay, and ferric-reducing antioxidant power assay) showed that water-based organic solvents increased the antioxidant capabilities of the extracts compared with water or pure organic solvents. ASE was more suitable for the extraction of phenolics than UAE.

The influence of ripening stage and region on the chemical compounds in mulberry fruits (Morus atropurpurea Roxb.) based on UPLC-QTOF-MS.

Mulberries (Morus atropurpurea Roxb.) are rich in beneficial nutrients and secondary metabolites. Dramatic climate differences between western and eastern China lead to differences among the fruiting habits of mulberries grown in these regions. In this study, Xinjiang and Jiangsu, two regions in western and eastern China, respectively, were selected as sites where mulberry fruits (MFs) at different ripening stages were sampled. Their individual components, including both targeted and non-targeted chemical compounds, were detected by rapid ultra performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS). Multivariate statistical analyses, including principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were used to compare MFs during ripening from these two regions. Potential biomarkers, which significantly contributed to the differentiation of the samples, were further identified or tentatively identified to determine the effects of ripening stages and regions on the chemical compounds in MFs. The results show that 43 compounds classified into nine different groups were identified in the MF samples from both the Xinjiang and Jiangsu regions. Among the compounds, all anthocyanins, carbohydrates and dihydroflavonols increased while phenolic acids and hydroxycoumarins decreased during ripening. Caffeoylquinic acids and some of anthocyanins could be regarded as important markers for MF ripening, and the accumulation of organic acids differentiated the samples from the two regions. Together, UPLC-QTOF-MS coupled with multivariate statistical analyses may be effective for metabolite profiling and identification of ripening degrees and cultivation regions.

Effect of meteorological parameters and regions on accumulation pattern of phenolic compounds in different mulberry cultivars grown in China.

The compositions of phenolic compounds in 10 cultivars of two mulberry species (Morus atropurpurea Roxb. and Morus alba Linn.) grown in four regions of China were analysed using HPLC-TOF-MS. Results showed that a total of 27 phenolic compounds were identified in these mulberry cultivars. The Taiwan cultivar from the Jiangsu region showed the highest concentration of hydroxycinnamic acids, quercetin derivatives, and anthocyanins. Multivariate statistical analysis revealed that six mulberry cultivars grown in the region of Jiangsu, Ningxia, and Guangdong were differentiated regarding their species feature and regional characteristics. Cyanidin rhamnosylglucoside, 4-caffeoylquinic acid, dihydroquercetin, and quercetin were further screened out to be the key compounds for the differentiation of these cultivars. The correlation between the regional climate feature (including rainfall, humidity, and temperature) and the accumulation of phenolic compounds in these mulberry cultivars was established.

Effects of piceatannol and pterostilbene against ß-amyloid-induced apoptosis on the PI3K/Akt/Bad signaling pathway in PC12 cells.

Neuron apoptosis induced by ß-amyloid (Aß) is an important precipitating factor in the pathogenesis of Alzheimer's disease (AD). In the present study, the effects of piceatannol (PT) and pterostilbene (PS) against Aß-induced apoptosis in PC12 cells were evaluated. PT and PS both showed observable anti-apoptosis activity. Increased cell viability, decreased apoptosis rate and declining intracellular ROS were observed after PT and PS treatment. For the signaling pathway, PT significantly promoted phosphorylation of Akt and Bad, further suppressed Bcl-2/Bax expression and inhibited cleavage of caspase-9, caspase-3 and PARP. PS promoted phosphorylation of Akt without affecting the other factors. The experimental results, for the first time, unambiguously suggested that PT showed a comprehensive protective effect against Aß-induced apoptosis in PC12 cells via a novel PI3K/Akt/Bad signaling pathway and downstream mitochondria-mediated and caspase-dependent signaling pathway. Unlike PT, PS inhibited apoptosis against Aß through a different PI3K/Akt signaling pathway in which the downstream targets need to be further investigated. The results also provide the basis for dietary intervention involved in the prevention and adjunctive therapy of AD.

Phenolic Profiles, Antioxidant Activities, and Neuroprotective Properties of Mulberry (Morus atropurpurea Roxb.) Fruit Extracts from Different Ripening Stages.

The present work investigated the phenolic profiles (including nonanthocyanin and anthocyanin phenolics), antioxidant activities, and neuroprotective potential of mulberry fruit (MF) (Morus atropurpurea Roxb.) grown in China at different ripening stages. High-performance liquid chromatography-tandem mass spectrometry method (HPLC-MS/MS) was used to identify and quantify the phenolic compounds. The antioxidant capacity, total phenolic content (TPC), total flavonoid content (TFC), and total monomeric anthocyanin content (TAC) were determined using spectrophotometric methods. The neuroprotective effects of MFs at different ripening stages were investigated using Aß25-35 -treated PC12 cells as the cellular model of Alzheimer's disease. Of the 19 phenolic compounds characterized from the MF extracts, the contents of rutin and anthocyanins increased and that of chlorogenic acid decreased significantly with maturity. At the fully ripened stage, MF extracts showed the highest amounts of TPC (11.23 mg gallic acid equivalents/g fresh weight), TFC (15.1 mg rutin equivalents/g fresh weight), and TAC (1177 mg cyanidin 3-O-glucoside equivalents/100 g fresh weight). Meanwhile, antioxidant activity of MF extracts at this stage was highest according to ABTS (an IC50 value of 4.11 µg/mL) and DPPH (an IC50 value of 10.08 µg/mL) assays. Cellular assays revealed increased cell viability in cells treated with the ripe MF extracts; compared with the control groups, the ripening fruits also increased the antioxidant enzyme levels in PC12 cells. Together, these results suggest that the antioxidant activities and neuroprotective properties of ripening MFs are related to the contents and types of phenolic compounds that are present in the fruits.

Comparison of Polyphenol Profile and Inhibitory Activities Against Oxidation and α-Glucosidase in Mulberry (Genus Morus) Cultivars from China.

UNLABELLED: Mulberry (genus Morus) is a significant source of polyphenols, which can promote positive effects on human health. China has various mulberry cultivars, however, many Chinese mulberry cultivars have been only minimally studied. To solve this lack of research, 8 mulberry cultivars (Da10, Tang10, Yueshen74, Yuefenshen, Longsang, Ningxia1hao, Taiwanguosang, and Baiyuwang) from 4 regions of China were assessed to determine their polyphenol profiles using HPLC-MS/MS and then tested for their antioxidant and anti-α-glucosidase activities in vitro. A total of 18 nonanthocyanins and 4 anthocyanins were quantified in mulberry cultivars; among these polyphenols, chlorogenic acid, quercetin 3-O-rutinoside, and cyanidin 3-O-glucoside were confirmed as the major phenolic acid, flavonol derivative, and anthocyanin, respectively. Two types of stilbene compounds, piceid, and piceatannol, were detected for the 1st time in all mulberry cultivars. Moreover, the methanolic extracts of different mulberry cultivars showed disparate antioxidant and α-glucosidase inhibitory activities, and this discrepancy was mainly attributed to varying the anthocyanin content. Based on our results, Taiwanguosang is proposed to be a good candidate suitable for further process due to its high level of anthocyanins. PRACTICAL APPLICATION: The polyphenols of mulberry cultivars are vital for human health and are relevant to the further development of mulberry-based products. China has a wide range of mulberry cultivar resources, and many of these cultivars have not yet been studied. Our research concentrated on the polyphenol profiles, antioxidant, and α-glucosidase inhibitory activities of various mulberry cultivars from different regions of China to provide basic information for mulberry cultivar selection and mulberry-based food production.

Properties of novel polyvinyl alcohol/cellulose nanocrystals/silver nanoparticles blend membranes.

Novel polyvinyl alcohol (PVA) blend membranes containing cellulose nanocrystals (CNs) and silver nanoparticles (AgNPs) were prepared via a simple method. CNs were prepared by sulfuric acid treatment of microcrystalline cellulose. AgNO3 aqueous solution mixed with the CNs aqueous suspension and was reduced by NaBH4 at room temperature. Purified CNs/AgNPs nanocomposites as functional fillers mixed with polyvinyl alcohol to prepare blend membrane. The morphology, mechanical properties, and antibacterial activities of PVA/CNs/AgNPs composite films were investigated. The PVA/CNs/AgNPs composite films were stable and homogeneous. The tensile strength of PVA was increased from 57.02 MPa to 81.21 MPa when filled with CNs/AgNPs. Antibacterial ratio of PVA/CNs/AgNPs composite against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus was 96.9% and 88.2%, respectively. The CNs/AgNPs nanocomposites could be applied as bi-functional nanofillers within PVA to improve the mechanical properties and antibacterial activities.