Hepatic Physiology Research Articles

Homocysteine activates autophagy by inhibition of CFTR expression via interaction between DNA methylation and H3K27me3 in mouse liver

Elevated homocysteine (Hcy) levels have been reported to be involved in liver injury, and autophagy plays an important role in normal hepatic physiology and pathophysiology, but the mechanism underlying Hcy regulated autophagy is currently unknown. In this study, CBS+/- mice were fed with regular diet for 12 weeks to establish a hyperhomocysteinemia (HHcy) model and HL-7702 cells were treated with Hcy, we found that Hcy increases autophagy and aggravates liver injury by downregulation of cystic fibrosis transmembrane conductance regulator (CFTR) expression in vivo and in vitro. Overexpression of CFTR inhibited the formation of autophagosomes and the expression of autophagy-related proteins BECN1, LC3-II/I and Atg12, while the expression of p62 increased in Hcy-treated hepatocytes and CBS+/- mice injected with lentivirus expressing CFTR. Further study showed that CFTR expression is regulated by the interaction of DNA methyltransferase 1 (DNMT1) and enhancer of zeste homolog 2 (EZH2), which, respectively, regulate DNA methylation and histone H3 lysine 27 trimethylation (H3K27me3). In conclusion, our study showed that Hcy activates autophagy by inhibition of CFTR expression via interaction between H3K27me3 and DNA methylation in the mouse liver. These findings provide new insight into the mechanism of Hcy-induced autophagy in liver injury.

Alterations of blood chemistry, hepatic and renal function, and blood cytometry in acrylamide-treated rats.

Acrylamide is a vinyl monomer that is widely used for the synthesis of polyacrylamides, the treatment of drinking water, and as an additive in cosmetics. Acrylamide is also produced during the thermal processing of carbohydrate-rich foods. Although the potential toxic effects of acrylamide have been reported, few studies have evaluated biochemical parameters in blood. The present study investigated alterations of blood chemistry, hepatic function, and blood cytometry in acrylamide-treated rats. Thirty-two male Wistar rats were assigned to four experimental groups (n = 8/group): one control group received 0.3 ml of vehicle (saline solution), and the other three groups received acrylamide (25, 50, and 75 mg/kg, i.p., for 14 days). At the end of treatment, blood samples were collected to obtain serum, which was then processed using a Vitros250 device. For blood cytometry, the samples were processed in a Sysmex analyzer. The blood chemistry results showed that urea nitrogen, urea, and creatinine were elevated in the acrylamide-treated groups. Tests of hepatic function showed that total and direct bilirubins, transaminases, and alkaline phosphatase were also elevated compared with vehicle, whereas the levels of total proteins and albumin decreased. Blood cytometry showed that the levels of erythrocytes, hemoglobin, hematocrit, leukocytes, and platelets and mean cell volume decreased in the acrylamide-treated groups compared with vehicle. Overall, the present findings indicate that acrylamide causes deleterious effects on renal and hepatic physiology, producing dose-dependent alterations of blood chemistry and cytometry parameters in male Wistar rats.

Computational Modeling in Liver Surgery.

The need for extended liver resection is increasing due to the growing incidence of liver tumors in aging societies. Individualized surgical planning is the key for identifying the optimal resection strategy and to minimize the risk of postoperative liver failure and tumor recurrence. Current computational tools provide virtual planning of liver resection by taking into account the spatial relationship between the tumor and the hepatic vascular trees, as well as the size of the future liver remnant. However, size and function of the liver are not necessarily equivalent. Hence, determining the future liver volume might misestimate the future liver function, especially in cases of hepatic comorbidities such as hepatic steatosis. A systems medicine approach could be applied, including biological, medical, and surgical aspects, by integrating all available anatomical and functional information of the individual patient. Such an approach holds promise for better prediction of postoperative liver function and hence improved risk assessment. This review provides an overview of mathematical models related to the liver and its function and explores their potential relevance for computational liver surgery. We first summarize key facts of hepatic anatomy, physiology, and pathology relevant for hepatic surgery, followed by a description of the computational tools currently used in liver surgical planning. Then we present selected state-of-the-art computational liver models potentially useful to support liver surgery. Finally, we discuss the main challenges that will need to be addressed when developing advanced computational planning tools in the context of liver surgery.

Transient Changes in Hepatic Physiology That Alter Bilirubin and Bile Acid Transport May Explain Elevations in Liver Chemistries Observed in Clinical Trials of GGF2 (Cimaglermin Alfa).

GGF2 is a recombinant human neuregulin-1β in development for chronic heart failure. Phase 1 clinical trials of GGF2 were put on hold when transient elevations in serum aminotransferases and total bilirubin were observed in 2 of 43 subjects who received single doses of GGF2 at 1.5 or 0.378 mg/kg. However, aminotransferase elevations were modest and not typical of liver injury sufficient to result in elevated serum bilirubin. Cynomolgus monkeys administered a single 15 mg/kg dose of GGF2 had similar transient elevations in serum aminotransferases and bilirubin as well as transient elevations in serum bile acids. However, no hepatocellular necrosis was observed in liver biopsies obtained during peak elevations. When sandwich-cultured human hepatocytes were treated with GGF2 for up to 72 h at concentrations approximately 0.8-fold average plasma Cmax for the 0.378 mg/kg dose, no cytotoxicity was observed. Gene expression profiling identified approximately 50% reductions in mRNAs coding for bilirubin transporters and bile acid conjugating enzymes, as well as changes in expression of additional genes mimicking the interleukin-6-mediated acute phase response. Similar gene expression changes were observed in GGF2-treated HepG2 cells and primary monkey hepatocytes. Additional studies conducted in sandwich-cultured human hepatocytes revealed a transient and GGF2 concentration-dependent decrease in hepatocyte bile acid content and biliary clearance of taurocholate without affecting biliary taurocholate efflux. Taken together, these data suggest that GGF2 does not cause significant hepatocellular death, but transiently modifies hepatic handling of bilirubin and bile acids, effects that may account for the elevations in serum bilirubin observed in the clinical trial subjects.

Glycogen-gold nanohybrid escalates the potency of silymarin.

In this study, a glycogen–gold nanohybrid was fabricated to enhance the potency of a promising hepatoprotective agent silymarin (Sly) by improving its solubility and gut permeation. By utilizing a facile green chemistry approach, biogenic gold nanoparticles were synthesized from Annona reticulata leaf phytoconstituents in combination with Sly (SGNPs). Further, the SGNPs were aggregated in glycogen biopolymer to yield the therapeutic nanohybrids (GSGNPs). Transmission electron microscopy, UV–Vis spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy analysis confirmed the successful formation and conjugation of both SGNPs and GSGNPs. The fabricated nanohybrids showed significant protection against CCl4-induced hepatic injury in Wistar rats and maintained natural antioxidant (superoxide dismutase and catalase) levels. Animals treated with GSGNPs (10 mg/kg) and SGNPs (20 mg/kg) retained usual hepatic functions with routine levels of hepatobiliary enzymes (aspartate transferase, alanine transaminase, alkaline phosphatase, and lactate dehydrogenase) and inflammatory markers (interleukin-1β and tumor necrosis factor-α) with minimal lipid peroxidation, whereas those treated with 100 mg/kg of Sly showed the similar effect. These results were also supported by histopathology of the livers where pronounced hepatoprotection with normal hepatic physiology and negligible inflammatory infiltrate were observed. Significant higher plasma Cmax supported the enhanced bioavailability of Sly upon GSGNPs treatment compared to SGNPs and free Sly. Graphite furnace atomic absorption spectrophotometry analysis also substantiated the efficient delivery of GSGNPs over SGNPs. The fabricated therapeutic nanohybrids were also found to be biocompatible toward human erythrocytes and L929 mouse fibroblast cells. Overall, due to increased solubility, bioavailability and profuse gut absorption; GSGNPs demonstrated tenfold enhanced potency compared to free Sly.

RNA sequencing of db/db mice liver identifies lncRNA H19 as a key regulator of gluconeogenesis and hepatic glucose output

Liver plays a key role in maintaining glucose homeostasis and impaired hepatic glucose metabolism is associated with type 2 diabetes. In the present study, we used RNA sequencing to profile the transcriptome of the livers of diabetic db/db mice as compared to the normal db/+ mice and identified 218 differentially expressed genes. Amongst these, there were 3 lncRNAs that were significantly downregulated and H19 was the most altered lncRNA in the livers of db/db mice. H19 expression significantly correlated with the expression of genes of the glycolysis and gluconeogenesis pathways, which suggest that altered hepatic H19 levels can directly or indirectly modulate their expression. Inhibition of H19 using specific siRNA in HepG2 cells and primary mouse hepatocytes significantly increased the levels of gluconeogenic genes. This was subsequently accompanied by increased hepatic glucose output. Further,H19 depletion in HepG2 cells impaired insulin signaling and increased nuclear localization of FoxO1, an important transcriptional regulator of gluconeogenic gene expression. Our results reveal a novel link between decreased H19 levels and impaired gluconeogenesis via regulation of FoxO1 nuclear levels. These put forth interesting observations on the regulatory role of H19 in altering hepatic physiology during diabetes.

Insights into the role of hepatocyte PPARα activity in response to fasting.

The liver plays a central role in the regulation of fatty acid metabolism. Hepatocytes are highly sensitive to nutrients and hormones that drive extensive transcriptional responses. Nuclear hormone receptors are key transcription factors involved in this process. Among these factors, PPARα is a critical regulator of hepatic lipid catabolism during fasting. This study aimed to analyse the wide array of hepatic PPARα-dependent transcriptional responses during fasting. We compared gene expression in male mice with a hepatocyte specific deletion of PPARα and their wild-type littermates in the fed (ad libitum) and 24-h fasted states. Liver samples were acquired, and transcriptome and lipidome analyses were performed. Our data extended and confirmed the critical role of hepatocyte PPARα as a central for regulator of gene expression during starvation. Interestingly, we identified novel PPARα-sensitive genes, including Cxcl-10, Rab30, and Krt23. We also found that liver phospholipid remodelling was a novel fasting-sensitive pathway regulated by PPARα. These results may contribute to investigations on transcriptional control in hepatic physiology and underscore the clinical relevance of drugs that target PPARα in liver pathologies, such as non-alcoholic fatty liver disease.

The Liver and Portal System

Understanding of the anatomy and physiology of the liver and techniques for safe anatomic and nonanatomic liver resections has evolved over the past several decades. The liver is composed of a complex arterial and portal venous inflow, which has several important variants that are crucial for the surgeon to understand when planning hepatic resections, both anatomic and nonanatomic. In addition, intra- and extrahepatic biliary configurations may be encountered, and variants must be recognized to prevent complications during common surgical procedures, such as cholecystectomy and liver resection. The liver is responsible for numerous metabolic, homeostatic, and immunologic processes throughout the body. It is crucial for the practicing physician and surgeon to have a fundamental understanding of hepatic anatomy and physiology when treating patients with derangements in liver structure and function. Key words: bile duct, bilirubin, bilirubin metabolism, hepatic artery, hepatic blood flow, hepatic parenchyma microstructure, liver anatomy, portal hypertension, portal vein

The Liver and Portal System

Understanding of the anatomy and physiology of the liver and techniques for safe anatomic and nonanatomic liver resections has evolved over the past several decades. The liver is composed of a complex arterial and portal venous inflow, which has several important variants that are crucial for the surgeon to understand when planning hepatic resections, both anatomic and nonanatomic. In addition, intra- and extrahepatic biliary configurations may be encountered, and variants must be recognized to prevent complications during common surgical procedures, such as cholecystectomy and liver resection. The liver is responsible for numerous metabolic, homeostatic, and immunologic processes throughout the body. It is crucial for the practicing physician and surgeon to have a fundamental understanding of hepatic anatomy and physiology when treating patients with derangements in liver structure and function. Key words: bile duct, bilirubin, bilirubin metabolism, hepatic artery, hepatic blood flow, hepatic parenchyma microstructure, liver anatomy, portal hypertension, portal vein

Role of the Wnt/β-Catenin Pathway in the Pathogenesis of Alcoholic Liver Disease.

The Wnt pathway is a highly conserved signal transduction pathway that plays an important role in diverse aspects of hepatic physiology. The Wnt pathway, consisting of canonical and noncanonical arms, is composed of secreted glycoproteins, cell surface receptors and co-receptors, and complex intracellular regulatory machinery that regulate a large number of cellular functions. β-Catenin is the main effector of the canonical Wnt pathway and hepatocyte-specific loss of the protein leads to increased susceptibility to alcoholic steatohepatitis. Hepatocytes with disrupted β-catenin demonstrate mitochondrial dysfunction, defective oxidative phosphorylation, and increased oxidative stress. β- Catenin knockout mice have decreased expression of alcohol metabolizing enzymes and increased blood alcohol levels that along with hypoglycemia and hyperammonemia, lead to increased mortality upon alcohol exposure. Disruption of hepatic β-catenin affects fatty acid oxidation and fasting ketogenesis and thereby profoundly affects systemic energy homeostasis. Given the combined roles of Wnt/β-catenin signaling in hepatocellular bioenergetics and regeneration, the Wnt pathway also contributes to alcohol-induced hepatic fibrogenesis and hepatocarcinogenesis. Targeting the Wnt/β-catenin pathway represents an attractive strategy for the treatment of alcohol-induced liver disease.

Functional proteomic analysis of corticosteroid pharmacodynamics in rat liver: Relationship to hepatic stress, signaling, energy regulation, and drug metabolism

Corticosteroids (CS) are anti-inflammatory agents that cause extensive pharmacogenomic and proteomic changes in multiple tissues. An understanding of the proteome-wide effects of CS in liver and its relationships to altered hepatic and systemic physiology remains incomplete. Here, we report the application of a functional pharmacoproteomic approach to gain integrated insight into the complex nature of CS responses in liver in vivo. An in-depth functional analysis was performed using rich pharmacodynamic (temporal-based) proteomic data measured over 66h in rat liver following a single dose of methylprednisolone (MPL). Data mining identified 451 differentially regulated proteins. These proteins were analyzed on the basis of temporal regulation, cellular localization, and literature-mined functional information. Of the 451 proteins, 378 were clustered into six functional groups based on major clinically-relevant effects of CS in liver. MPL-responsive proteins were highly localized in the mitochondria (20%) and cytosol (24%). Interestingly, several proteins were related to hepatic stress and signaling processes, which appear to be involved in secondary signaling cascades and in protecting the liver from CS-induced oxidative damage. Consistent with known adverse metabolic effects of CS, several rate-controlling enzymes involved in amino acid metabolism, gluconeogenesis, and fatty-acid metabolism were altered by MPL. In addition, proteins involved in the metabolism of endogenous compounds, xenobiotics, and therapeutic drugs including cytochrome P450 and Phase-II enzymes were differentially regulated. Proteins related to the inflammatory acute-phase response were up-regulated in response to MPL. Functionally-similar proteins showed large diversity in their temporal profiles, indicating complex mechanisms of regulation by CS. SignificanceClinical use of corticosteroid (CS) therapy is frequent and chronic. However, current knowledge on the proteome-level effects of CS in liver and other tissues is sparse. While transcriptomic regulation following methylprednisolone (MPL) dosing has been temporally examined in rat liver, proteomic assessments are needed to better characterize the tissue-specific functional aspects of MPL actions. This study describes a functional pharmacoproteomic analysis of dynamic changes in MPL-regulated proteins in liver and provides biological insight into how steroid-induced perturbations on a molecular level may relate to both adverse and therapeutic responses presented clinically.

The Role of Akt in Chronic Liver Disease and Liver Regeneration

The liver is continuously exposed to diverse insults, which may culminate in pathological processes causing liver disease. An effective therapeutic strategy for chronic liver disease should control the causal factors of the disease and stimulate functional liver regeneration. Preclinical studies have shown that interventions aimed at maintaining Akt activity in a dysfunctional liver meet most of the criteria. Although the central function of Akt is cell survival, other cellular aspects such as glucose uptake, glycogen synthesis, cell-cycle progression, and lipid metabolism have been shown to be prominent functions of Akt in the context of hepatic physiology. In this review, the authors describe the benefits of the Akt signaling pathway, emphasizing its importance in coordinating proper cellular growth and differentiation during liver regeneration, hepatic function, and liver disease.

Sex and age differences in the expression of liver microRNAs during the life span of F344 rats

BackgroundPhysiological factors such as age and sex have been shown to be risk factors for adverse effects in the liver, including liver diseases and drug-induced liver injury. Previously, we have reported age- and sex-related significant differences in hepatic basal gene expression in rats during the life span that may be related to susceptibility to such adverse effects. However, the underlying mechanisms of the gene expression changes were not fully understood. In recent years, increasing evidence for epigenetic mechanisms of gene regulation has fueled interest in the role of microRNAs (miRNAs) in toxicogenomics and biomarker discovery. We therefore proposed that significant age and sex differences exist in baseline liver miRNA expression, and that comprehensive profiling of miRNAs will provide insights into the epigenetic regulation of gene expression in rat liver.MethodsTo address this, liver tissues from male and female F344 rats were examined at 2, 5, 6, 8, 15, 21, 52, 78, and 104 weeks of age for the expression of 677 unique miRNAs. Following data processing, predictive pathway analysis was performed on selected miRNAs that exhibited prominent age and/or sex differences in expression.ResultsOf the 314 miRNAs found to be expressed, 214 were differentially expressed; 65 and 212 miRNAs showed significant (false discovery rate (FDR) <5% and ≥1.5-fold change) sex- and age-related differences in expression, respectively. Thirty-eight miRNAs showed 2-week-specific expression, of which 31 miRNAs were found to be encoded within the Dlk1-Dio3 cluster located on chromosome 6. This cluster has been associated with tissue proliferation and differentiation, and liver energy homeostasis in postnatal development. Predictive pathway analysis linked sex-biased miRNA expression with sexually dimorphic molecular functions and toxicological functions that may reflect sex differences in hepatic physiology and disease. The expression of miRNAs (miR-18a, miR-99a, and miR-203, miR-451) was also found to associate with specific sexually dimorphic hepatic histopathology. The expression of miRNAs involved in regulating cell death, cell proliferation, and cell cycle was found to change as the rats matured from adult to old age.ConclusionsOverall, significant age- and sex-related differences in liver miRNA expression were identified and linked to histopathological findings and predicted functional pathways that may underlie susceptibilities to liver toxicity and disease.

Improved hepatic physiology in hepatic cytochrome P450 reductase null (HRN™) mice dosed orally with fenclozic acid.

Hepatic NADPH-cytochrome P450 oxidoreductase null (HRN™) mice exhibit no functional expression of hepatic cytochrome P450 (P450) when compared to wild type (WT) mice, but have normal hepatic and extrahepatic expression of other biotransformation enzymes. We have assessed the utility of HRN™ mice for investigation of the role of metabolic bioactivation in liver toxicity caused by the nonsteroidal anti-inflammatory drug (NSAID) fenclozic acid. In vitro studies revealed significant NADPH-dependent (i.e. P450-mediated) covalent binding of [14C]-fenclozic acid to liver microsomes from WT mice and HRN™ mice, whereas no in vitro covalent binding was observed in the presence of the UDP-glucuronyltransferase cofactor UDPGA. Oral fenclozic acid administration did not alter the liver histopathology or elevate the plasma liver enzyme activities of WT mice, or affect their hepatic miRNA contents. Livers from HRN™ mice exhibited abnormal liver histopathology (enhanced lipid accumulation, bile duct proliferation, hepatocellular degeneration, necrosis, inflammatory cell infiltration) and plasma clinical chemistry (elevated alanine aminotransferase, glutamate dehydrogenase and alkaline phosphatase activities). Modest apparent improvements in these abnormalities were observed when HRN™ mice were dosed orally with fenclozic acid for 7 days at 100 mg kg-1 day-1. Previously we observed more marked effects on liver histopathology and integrity in HRN™ mice dosed orally with the NSAID diclofenac for 7 days at 30 mg kg-1 day-1. We conclude that HRN™ mice are valuable for assessing P450-related hepatic drug biotransformation, but not for drug toxicity studies due to underlying liver dysfunction. Nonetheless, HRN™ mice may provide novel insights into the role of inflammation in liver injury, thereby aiding its treatment.

Sex- and age-dependent gene expression in human liver: An implication for drug-metabolizing enzymes

Sex and age differences in hepatic expression of drug-metabolizing enzyme genes could cause variations in drug metabolism, but has not been fully elucidated, especially in Asian population. In this study, the global expression of human hepatic genes was analyzed by microarrays in 40 Japanese subjects (27 males and 13 females). Thirty-five sex-biased genes were identified (P < 0.005). Whereas, 60 age-biased genes in two age groups, <60 years and ≥70 years (P < 0.001), were identified in males. By Gene Ontology analysis, the sex-biased genes were related to protein catabolism and modification, while the age-biased genes were related to transcription regulation and cell death. Quantitative polymerase chain reaction confirmed the female-biased expression of drug-metabolizing enzyme genes BChE, CYP4X1, and SULT1E1 (≥1.5-fold, P < 0.05). Further analysis of drug-metabolizing enzyme genes indicated that expression of CYP2A6 and CYP3A4 in females in the ≥70 age group was less than in the <60 age group (≥1.5-fold, P < 0.05), and this trend was also observed for PXR expression in males (≥1.5-fold, P < 0.05). The results presented provide important insights into hepatic physiology and function, especially drug metabolism, with respect to sex and age.

Functional Immune Anatomy of the Liver-As an Allograft.

The liver is an immunoregulatory organ in which a tolerogenic microenvironment mitigates the relative "strength" of local immune responses. Paradoxically, necro-inflammatory diseases create the need for most liver transplants. Treatment of hepatitis B virus, hepatitis C virus, and acute T cell-mediated rejection have redirected focus on long-term allograft structural integrity. Understanding of insults should enable decades of morbidity-free survival after liver replacement because of these tolerogenicproperties. Studies of long-term survivors show low-grade chronic inflammatory, fibrotic, and microvascular lesions, likely related to some combination of environment insults (i.e. abnormal physiology), donor-specific antibodies, and T cell-mediated immunity. The resultant conundrum is familiar in transplantation: adequate immunosuppression produces chronic toxicities, while lightened immunosuppression leads to sensitization, immunological injury, and structural deterioration. The "balance" is more favorable for liver than other solid organ allografts. This occurs because of unique hepatic immune physiology and provides unintended benefits for allografts by modulating various afferent and efferent limbs of allogenic immune responses. This review is intended to provide a better understanding of liver immune microanatomy and physiology and thereby (a) the potential structural consequences of low-level, including allo-antibody-mediated injury; and (b) how liver allografts modulate immune reactions. Special attention is given to the microvasculature and hepatic mononuclear phagocytic system.

Circadian rhythms of liver physiology and disease: experimental and clinical evidence.

The circadian clock system consists of a central clock located in the suprachiasmatic nucleus in the hypothalamus and peripheral clocks in peripheral tissues. Peripheral clocks in the liver have fundamental roles in maintaining liver homeostasis, including the regulation of energy metabolism and the expression of enzymes controlling the absorption and metabolism of xenobiotics. Over the past two decades, research has investigated the molecular mechanisms linking circadian clock genes with the regulation of hepatic physiological functions, using global clock-gene-knockout mice, or mice with liver-specific knockout of clock genes or clock-controlled genes. Clock dysfunction accelerates the development of liver diseases such as fatty liver diseases, cirrhosis, hepatitis and liver cancer, and these disorders also disrupt clock function. Food is an important regulator of circadian clocks in peripheral tissues. Thus, controlling the timing of food consumption and food composition, a concept known as chrononutrition, is one area of active research to aid recovery from many physiological dysfunctions. In this Review, we focus on the molecular mechanisms of hepatic circadian gene regulation and the relationships between hepatic circadian clock systems and liver physiology and disease. We concentrate on experimental data obtained from cell or mice and rat models and discuss how these findings translate into clinical research, and we highlight the latest developments in chrononutritional studies.

Lactobacillus acidophilus Restores Functionality in Uremic Macrophages: Plausible or Lacking Evidence?

Over the past several decades, research has redefined the interactions between gut microbes and vertebrates, now recognizing that the intestinal microbiome and its mammalian host have shared co-evolutionary metabolic interactions that span millennia. Studies from the Human Microbiome Project (HMP) have estimated that humans possess ten times more bacterial cells than there are human cells. In the gastrointestinal (GI) tract, the bacterial cohort contributes approximately 3.3 million non-redundant microbial genes, far exceeding that of the human input [1]. This genetic diversity is likely to provide the necessary cues through host-microbial interactions for the development of regulated signals that promote immunological tolerance, metabolic regulation, and stability, and other factors that may then help control local and extra-intestinal end-organ (e.g., renal, hepatic) physiology. The intestinal mucosa is the largest and most dynamic immunological environment of the body. Often the first point of pathogen or antigen exposure, many microbes use it as a point of entry into the rest of the body. The gut immune system therefore needs to be prepared to respond to insults either from pathogens or other molecular triggers while at the same time not responding to other presumably innocuous environmental antigens, food particles, and commensal bacteria and their respective metabolites. Misdirected immune responses to antigens thought harmless are thought by some to be the underlying cause of food allergies and debilitating conditions such as inflammatory bowel diseases with their unregulated and overcompensated, pro-inflammatory sequelae [2]. As a consequence, dysbiosis of the GI tract describes alteration of bacterial populations thought to increase the risk of developing gut barrier dysfunction with consequent increased permeability, also referred to as a ‘‘leaky gut,’’ with consequent translocation of bacteria, bacterial endotoxins, or environmental antigens across the gut wall. While the immune system is thought to be involved, mechanistic data that link immune function disruption to adverse end-organ physiological functions, which are present for the kidney, are mostly missing for the gut. The supposition that the GI tract bacterial cohort could indirectly and adversely influence the physiological function of an end-organ such as the liver or kidney, by contributing pro-inflammatory activity in the gut mucosa, is a novel concept with biological plausibility [2, 3]. Uremic toxins (e.g., glycation end products, p-cresyl sulfate, indoxyl sulfate) can produce pro-inflammatory responses, including leukocyte stimulation and endothelial dysfunction, which can promote GI tract dysbiosis [3–5]. Therefore, it is highly probable that the 100 trillion bacteria in the GI tract could negatively and positively influence the nutritive, metabolic, physiological, and importantly immunological functions of the host [2]. The diversity of commensal bacteria in the GI tract can, in turn, account for the varied macrophage responses that have been encountered in the intestines [6]. Macrophages, in their eradication of pathogenic microbes so as to maintain homeostasis, are an essential component of innate immunity. The activated phenotype exists in macrophages that present antigens to T lymphocytes in order to initiate an appropriate immune response after recognition of microbial proteins [7]. In addition to serving as antigen-presenting cells, activated macrophages & Luis Vitetta luis.vitetta@sydney.edu.au; luis_vitetta@medlab.co

Elevated Hepatic miR-22-3p Expression Impairs Gluconeogenesis by Silencing the Wnt-Responsive Transcription Factor Tcf7.

Levels of miR-22-3p, a highly abundant hepatic microRNA, are abnormally increased in mouse models of insulin resistance and type 2 diabetes, yet its contribution to deregulated hepatic metabolism under diseased states is not well understood. Here, we unravel a novel link between elevated hepatic miR-22-3p expression and impaired gluconeogenesis in diabetic db/db mice via the regulation of Tcf7 (transcription factor 7). Our data demonstrate that miR-22-3p binds to the 3' untranslated region of TCF7 and downregulates it, and this microRNA-mediated regulation of TCF7 increases the expression of enzymes of the gluconeogenic pathway in HepG2 cells. Small interfering RNA-mediated knockdown of TCF7 in HepG2 cells also causes similar upregulation of gluconeogenic genes. Furthermore, in vivo silencing of miR-22-3p by antagomiR administration lowered random as well as fasting glucose levels in diabetic mice. miR-22-3p antagonism improved glucose tolerance and insulin sensitivity. Importantly, the hepatic Tcf7 levels were restored along with reduced hepatic glucose output, which was also reflected by the decreased expression of gluconeogenic genes. Our results support a critical role for miR-22-3p and its target, Tcf7, in the pathogenesis of diabetes by upregulating gluconeogenesis. Moreover, targeting the miR-22/Tcf7/Wnt axis might hold therapeutic potential for the treatment of altered hepatic physiology during insulin resistance and type 2 diabetes.

Intestinal farnesoid X receptor puts a fresh coat of wax on fatty liver

Intestinal farnesoid X receptor puts a fresh coat of wax on fatty liver