-
Clinical Gastroenterology and... Jul 2023Primary biliary cholangitis (PBC) is an archetypal autoimmune disease. Chronic lymphocytic cholangitis is associated with interface hepatitis, ductopenia, cholestasis,... (Review)
Review
Primary biliary cholangitis (PBC) is an archetypal autoimmune disease. Chronic lymphocytic cholangitis is associated with interface hepatitis, ductopenia, cholestasis, and progressive biliary fibrosis. People living with PBC are frequently symptomatic, experiencing a quality-of-life burden dominated by fatigue, itch, abdominal pain, and sicca complex. Although the female predominance, specific serum autoantibodies, immune-mediated cellular injury, as well as genetic (HLA and non-HLA) risk factors, identify PBC as autoimmune, to date treatment has focused on cholestatic consequences. Biliary epithelial homeostasis is abnormal and contributes to disease. The impact of cholangiocyte senescence, apoptosis, and impaired bicarbonate secretion enhances chronic inflammation and bile acid retention. First-line therapy is a non-specific anti-cholestatic agent, ursodeoxycholic acid. For those with residual cholestasis biochemically, obeticholic acid is introduced, and this semisynthetic farnesoid X receptor agonist adds choleretic, anti-fibrotic, and anti-inflammatory activity. Future PBC licensed therapy will likely include peroxisome proliferator activated receptor (PPAR) pathway agonists, including specific PPAR-delta agonism (seladelpar), as well as elafibrinor and saroglitazar (both with broader PPAR agonism). These agents dovetail the clinical and trial experience for off-label bezafibrate and fenofibrate use. Symptom management is essential, and encouragingly, PPAR agonists reduce itch; IBAT inhibition (eg, linerixibat) also appears promising for pruritus. For those where liver fibrosis is the target, NOX inhibition is being evaluated. Earlier stage therapies in development include therapy to impact immunoregulation in patients, as well other approaches to treating pruritus (eg, antagonists of MrgprX4). Collectively the PBC therapeutic landscape is exciting. Therapy goals are increasingly proactive and individualized and aspire to rapidly achieve normal serum tests and quality of life with prevention of end-stage liver disease.
Topics: Humans; Female; Male; Liver Cirrhosis, Biliary; Quality of Life; Peroxisome Proliferator-Activated Receptors; Ursodeoxycholic Acid; Cholangitis; Cholestasis; Pruritus
PubMed: 36809835
DOI: 10.1016/j.cgh.2023.02.005 -
Metabolism: Clinical and Experimental Jan 2021Peroxisome proliferator-activated receptors (PPARs) are fatty acid-activated transcription factors of nuclear hormone receptor superfamily that regulate energy... (Review)
Review
Peroxisome proliferator-activated receptors (PPARs) are fatty acid-activated transcription factors of nuclear hormone receptor superfamily that regulate energy metabolism. Currently, three PPAR subtypes have been identified: PPARα, PPARγ, and PPARβ/δ. PPARα and PPARδ are highly expressed in oxidative tissues and regulate genes involved in substrate delivery and oxidative phosphorylation (OXPHOS) and regulation of energy homeostasis. In contrast, PPARγ is more important in lipogenesis and lipid synthesis, with highest expression levels in white adipose tissue (WAT). In addition to tissues regulating whole body energy homeostasis, PPARs are expressed in immune cells and have an emerging critical role in immune cell differentiation and fate commitment. In this review, we discuss the actions of PPARs in the function of the innate and the adaptive immune system and their implications in immune-mediated inflammatory conditions.
Topics: Animals; Humans; Immunity; Inflammation; Lipid Metabolism; Peroxisome Proliferator-Activated Receptors; T-Lymphocytes
PubMed: 32791172
DOI: 10.1016/j.metabol.2020.154338 -
Nature Mar 2016Little is known about how pro-obesity diets regulate tissue stem and progenitor cell function. Here we show that high-fat diet (HFD)-induced obesity augments the numbers...
Little is known about how pro-obesity diets regulate tissue stem and progenitor cell function. Here we show that high-fat diet (HFD)-induced obesity augments the numbers and function of Lgr5(+) intestinal stem cells of the mammalian intestine. Mechanistically, a HFD induces a robust peroxisome proliferator-activated receptor delta (PPAR-δ) signature in intestinal stem cells and progenitor cells (non-intestinal stem cells), and pharmacological activation of PPAR-δ recapitulates the effects of a HFD on these cells. Like a HFD, ex vivo treatment of intestinal organoid cultures with fatty acid constituents of the HFD enhances the self-renewal potential of these organoid bodies in a PPAR-δ-dependent manner. Notably, HFD- and agonist-activated PPAR-δ signalling endow organoid-initiating capacity to progenitors, and enforced PPAR-δ signalling permits these progenitors to form in vivo tumours after loss of the tumour suppressor Apc. These findings highlight how diet-modulated PPAR-δ activation alters not only the function of intestinal stem and progenitor cells, but also their capacity to initiate tumours.
Topics: Animals; Cell Count; Cell Self Renewal; Cell Transformation, Neoplastic; Colonic Neoplasms; Diet, High-Fat; Female; Genes, APC; Humans; Intestines; Male; Mice; Obesity; Organoids; PPAR delta; Signal Transduction; Stem Cell Niche; Stem Cells; beta Catenin
PubMed: 26935695
DOI: 10.1038/nature17173 -
Journal of Hepatology Mar 2015Peroxisome proliferator-activated receptor α (PPARα) is a ligand-activated transcription factor belonging, together with PPARγ and PPARβ/δ, to the NR1C nuclear... (Review)
Review
Peroxisome proliferator-activated receptor α (PPARα) is a ligand-activated transcription factor belonging, together with PPARγ and PPARβ/δ, to the NR1C nuclear receptor subfamily. Many PPARα target genes are involved in fatty acid metabolism in tissues with high oxidative rates such as muscle, heart and liver. PPARα activation, in combination with PPARβ/δ agonism, improves steatosis, inflammation and fibrosis in pre-clinical models of non-alcoholic fatty liver disease, identifying a new potential therapeutic area. In this review, we discuss the transcriptional activation and repression mechanisms by PPARα, the spectrum of target genes and chromatin-binding maps from recent genome-wide studies, paying particular attention to PPARα-regulation of hepatic fatty acid and plasma lipoprotein metabolism during nutritional transition, and of the inflammatory response. The role of PPARα, together with other PPARs, in non-alcoholic steatohepatitis will be discussed in light of available pre-clinical and clinical data.
Topics: Animals; Disease Models, Animal; Humans; Inflammation; Lipid Metabolism; Lipogenesis; Liver Cirrhosis; Mice; Models, Statistical; Non-alcoholic Fatty Liver Disease; PPAR alpha
PubMed: 25450203
DOI: 10.1016/j.jhep.2014.10.039 -
International Journal of Molecular... Jan 2016Adipogenesis is the process by which precursor stem cells differentiate into lipid laden adipocytes. Adipogenesis is regulated by a complex and highly orchestrated gene... (Review)
Review
Adipogenesis is the process by which precursor stem cells differentiate into lipid laden adipocytes. Adipogenesis is regulated by a complex and highly orchestrated gene expression program. In mammalian cells, the peroxisome proliferator-activated receptor γ (PPARγ), and the CCAAT/enhancer binding proteins (C/EBPs) such as C/EBPα, β and δ are considered the key early regulators of adipogenesis, while fatty acid binding protein 4 (FABP4), adiponectin, and fatty acid synthase (FAS) are responsible for the formation of mature adipocytes. Excess accumulation of lipids in the adipose tissue leads to obesity, which is associated with cardiovascular diseases, type II diabetes and other pathologies. Thus, investigating adipose tissue development and the underlying molecular mechanisms is vital to develop therapeutic agents capable of curbing the increasing incidence of obesity and related pathologies. In this review, we address the process of adipogenic differentiation, key transcription factors and proteins involved, adipogenic regulators and potential anti-adipogenic bioactive molecules.
Topics: Adipocytes; Adipogenesis; Adiponectin; Adipose Tissue; Animals; CCAAT-Enhancer-Binding Protein-delta; CCAAT-Enhancer-Binding Proteins; Fatty Acid Synthase, Type I; Fatty Acid-Binding Proteins; Gene Expression Regulation; Genistein; Humans; Hydroxycholesterols; Mice; Obesity; PPAR gamma; Protein Isoforms; Resveratrol; Signal Transduction; Stilbenes
PubMed: 26797605
DOI: 10.3390/ijms17010124 -
Cell Metabolism Jul 2022The ovarian-tumor-domain-containing deubiquitinases (OTUDs) block ubiquitin-dependent protein degradation and are involved in diverse signaling pathways. We discovered a...
The ovarian-tumor-domain-containing deubiquitinases (OTUDs) block ubiquitin-dependent protein degradation and are involved in diverse signaling pathways. We discovered a rare OTUD3 c.863G>A mutation in a family with an early age of onset of diabetes. This mutation reduces the stability and catalytic activity of OTUD3. We next constructed an experiment with Otud3 mice and found that they developed worse obesity, dyslipidemia, and insulin resistance than wild-type mice when challenged with a high-fat diet (HFD). We further found that glucose and fatty acids stimulate CREB-binding-protein-dependent OTUD3 acetylation, promoting its nuclear translocation, where OTUD3 regulates various genes involved in glucose and lipid metabolism and oxidative phosphorylation by stabilizing peroxisome-proliferator-activated receptor delta (PPARδ). Moreover, targeting PPARδ using a specific agonist can partially rescue the phenotype of HFD-fed Otud3 mice. We propose that OTUD3 is an important regulator of energy metabolism and that the OTUD3 c.863G>A is associated with obesity and a higher risk of diabetes.
Topics: Animals; Deubiquitinating Enzymes; Diabetes Mellitus; Glucose; Homeostasis; Insulin Resistance; Mice; Nutritional Status; Obesity; PPAR delta; Stress, Physiological; Ubiquitin-Specific Proteases
PubMed: 35675826
DOI: 10.1016/j.cmet.2022.05.005 -
International Journal of Molecular... Mar 2020Peroxisome proliferator-activated receptor (PPAR) α, β/δ, and γ modulate lipid homeostasis. PPARα regulates lipid metabolism in the liver, the organ that largely... (Review)
Review
Peroxisome proliferator-activated receptor (PPAR) α, β/δ, and γ modulate lipid homeostasis. PPARα regulates lipid metabolism in the liver, the organ that largely controls whole-body nutrient/energy homeostasis, and its abnormalities may lead to hepatic steatosis, steatohepatitis, steatofibrosis, and liver cancer. PPARβ/δ promotes fatty acid β-oxidation largely in extrahepatic organs, and PPARγ stores triacylglycerol in adipocytes. Investigations using liver-specific PPAR-disrupted mice have revealed major but distinct contributions of the three PPARs in the liver. This review summarizes the findings of liver-specific PPAR-null mice and discusses the role of PPARs in the liver.
Topics: Animals; Energy Metabolism; Gene Expression Regulation; Homeostasis; Humans; Lipid Metabolism; Liver; Mice; Mice, Knockout; Multigene Family; Organ Specificity; Peroxisome Proliferator-Activated Receptors; Protein Isoforms; Signal Transduction
PubMed: 32192216
DOI: 10.3390/ijms21062061 -
Inflammation Research : Official... Jun 2019The peroxisome proliferator-activated receptor (PPAR) family includes three transcription factors: PPARα, PPARβ/δ, and PPARγ. PPAR are nuclear receptors activated by... (Review)
Review
The peroxisome proliferator-activated receptor (PPAR) family includes three transcription factors: PPARα, PPARβ/δ, and PPARγ. PPAR are nuclear receptors activated by oxidised and nitrated fatty acid derivatives as well as by cyclopentenone prostaglandins (PGA and 15d-PGJ) during the inflammatory response. This results in the modulation of the pro-inflammatory response, preventing it from being excessively activated. Other activators of these receptors are nonsteroidal anti-inflammatory drug (NSAID) and fatty acids, especially polyunsaturated fatty acid (PUFA) (arachidonic acid, ALA, EPA, and DHA). The main function of PPAR during the inflammatory reaction is to promote the inactivation of NF-κB. Possible mechanisms of inactivation include direct binding and thus inactivation of p65 NF-κB or ubiquitination leading to proteolytic degradation of p65 NF-κB. PPAR also exert indirect effects on NF-κB. They promote the expression of antioxidant enzymes, such as catalase, superoxide dismutase, or heme oxygenase-1, resulting in a reduction in the concentration of reactive oxygen species (ROS), i.e., secondary transmitters in inflammatory reactions. PPAR also cause an increase in the expression of IκBα, SIRT1, and PTEN, which interferes with the activation and function of NF-κB in inflammatory reactions.
Topics: Animals; Cyclooxygenase 2; Humans; Inflammation; Ligands; NF-kappa B; Peroxisome Proliferator-Activated Receptors
PubMed: 30927048
DOI: 10.1007/s00011-019-01231-1 -
Neurochemical Research May 2020Peroxisome proliferator activated receptor alpha (PPAR-α) belongs to the family of ligand-regulated nuclear receptors (PPARs). These receptors after heterodimerization... (Review)
Review
Peroxisome proliferator activated receptor alpha (PPAR-α) belongs to the family of ligand-regulated nuclear receptors (PPARs). These receptors after heterodimerization with retinoid X receptor (RXR) bind in promotor of target genes to PPAR response elements (PPREs) and act as a potent transcription factors. PPAR-α and other receptors from this family, such as PPAR-β/δ and PPAR-γ are expressed in the brain and other organs and play a significant role in oxidative stress, energy homeostasis, mitochondrial fatty acids metabolism and inflammation. PPAR-α takes part in regulation of genes coding proteins that are involved in glutamate homeostasis and cholinergic/dopaminergic signaling in the brain. Moreover, PPAR-α regulates expression of genes coding enzymes engaged in amyloid precursor protein (APP) metabolism. It activates gene coding of α secretase, which is responsible for non-amyloidogenic pathway of APP degradation. It also down regulates β secretase (BACE-1), the main enzyme responsible for amyloid beta (Aβ) peptide release in Alzheimer Diseases (AD). In AD brain expression of genes of PPAR-α and PPAR-γ coactivator-1 alpha (PGC-1α) is significantly decreased. PPARs are altered not only in AD but in other neurodegenerative/neurodevelopmental and psychiatric disorder. PPAR-α downregulation may decrease anti-oxidative and anti-inflammatory processes and could be responsible for the alteration of fatty acid transport, lipid metabolism and disturbances of mitochondria function in the brain of AD patients. Specific activators of PPAR-α may be important for improvement of brain cells metabolism and cognitive function in neurodegenerative and neurodevelopmental disorders.
Topics: Alzheimer Disease; Animals; Brain; Drug Delivery Systems; Fenofibrate; Humans; Neurodegenerative Diseases; PPAR alpha
PubMed: 32170673
DOI: 10.1007/s11064-020-02993-5 -
Cell Reports Aug 2021Peroxisome proliferator-activated receptor β/δ (PPARβ/δ) activates AMP-activated protein kinase (AMPK) and plays a crucial role in glucose and lipid metabolism....
Peroxisome proliferator-activated receptor β/δ (PPARβ/δ) activates AMP-activated protein kinase (AMPK) and plays a crucial role in glucose and lipid metabolism. Here, we examine whether PPARβ/δ activation effects depend on growth differentiation factor 15 (GDF15), a stress response cytokine that regulates energy metabolism. Pharmacological PPARβ/δ activation increases GDF15 levels and ameliorates glucose intolerance, fatty acid oxidation, endoplasmic reticulum stress, and inflammation, and activates AMPK in HFD-fed mice, whereas these effects are abrogated by the injection of a GDF15 neutralizing antibody and in Gdf15 mice. The AMPK-p53 pathway is involved in the PPARβ/δ-mediated increase in GDF15, which in turn activates again AMPK. Consistently, Gdf15 mice show reduced AMPK activation in skeletal muscle, whereas GDF15 administration results in AMPK activation in this organ. Collectively, these data reveal a mechanism by which PPARβ/δ activation increases GDF15 levels via AMPK and p53, which in turn mediates the metabolic effects of PPARβ/δ by sustaining AMPK activation.
Topics: AMP-Activated Protein Kinases; Adenylate Kinase; Animals; Cell Line; Endoplasmic Reticulum Stress; Enzyme Activation; Growth Differentiation Factor 15; Inflammation; Insulin; Lipid Metabolism; Liver; Mice, Inbred C57BL; Mice, Knockout; Muscle, Skeletal; PPAR delta; PPAR-beta; Signal Transduction; Tumor Suppressor Protein p53; Mice
PubMed: 34380027
DOI: 10.1016/j.celrep.2021.109501