Activation of human peroxisome proliferator-activated receptor (PPAR) subtypes by pioglitazone

PPAR-mediated reduction of lipid accumulation in hepatocytes involves the autophagy-lysosome-mitochondrion axis

BACKGROUND AND AIM

Lipid accumulation in hepatocytes is reduced by the activation of the peroxisome proliferator-activated receptor (PPAR) α, which is associated with increased lysosomal acid lipase (LAL) activity, transcription factor EB (TFEB) expression, and mitochondrial β-oxidation.Aim of the study was to assess whether the three isoforms of PPAR, i.e. α, δ and γ, share the same ability to reduce lipid accumulation in hepatocytes and to clarify the involvement of autophagy activation, lysosomal hydrolysis, and mitochondrial β-oxidation in lipid clearance induced by PPARs.

METHODS

HepG2 cells were treated with oleate/palmitate (O/P) to induce lipid accumulation and exposed to the PPARα agonist fenofibric acid, the γ agonist pioglitazone, the δ agonist seladelpar, or the dual α/γ agonist saroglitazar.

RESULTS

The treatment of HepG2 cells with fenofibric acid, pioglitazone, seladelpar, or saroglitazar halved lipid accumulation induced by O/P. PPAR agonists increased TFEB, p62, and LC3 expression and rescued LAL impairment induced by O/P. Moreover, PPAR agonists significantly increased mitochondrial mass and the expression of genes involved in mitochondrial dynamics and fatty acid catabolism. Interestingly, PPAR agonists lost their ability to reduce lipid accumulation when autophagic flux, LAL activity, or fatty acid transport in the mitochondria were blocked by specific inhibitors.

CONCLUSION

All PPAR agonists were able to promote the clearance of lipids in cells loaded with long-chain fatty acids. The key role of acid hydrolysis to generate fatty acids, which can be then catabolized in the mitochondria, and the ability of the PPAR system to sustain each phase of this clearing process were elucidated.

Cannabidiol dose dependently reduces alcohol intake in mice via a non-5-HT1A receptor mechanism: Exploration of other potential receptor targets

BACKGROUND AND PURPOSE

Binge drinking is a risky pattern of alcohol intake and a major predictor of alcohol use disorder (AUD). Current AUD medications have limited efficacy and poor patient compliance, calling for more effective therapeutics. Cannabidiol (CBD), a non-intoxicating component of cannabis, has emerged as a potential novel therapeutic. However, receptor mechanisms in CBD's alcohol-related effects have not been investigated comprehensively.

EXPERIMENTAL APPROACH

Using the murine drinking-in-the-dark model of binge drinking, our research aimed to confirm a reduction of alcohol consumption with CBD (7.5, 15, 30, 60, 120 mg kg-1) in male and female mice. Behavioural pharmacological approaches were used to explore CBD interactions with identified target mechanisms: serotonin-1A receptor (5-HT1AR) and peroxisome proliferator-activated receptor-gamma (PPARɣ), and the novel targets, chemokine receptor type-4 (CXCR4) and neuropeptide S receptor (NPSR).

KEY RESULTS

Acute CBD dose dependently suppressed binge-like drinking and blood ethanol concentration. The effect was not driven by locomotor impairments and was maintained across sub-chronic treatment. Blockade of 5-HT1AR and PPARɣ had no impact on CBD's reduction of alcohol consumption. Co-administration of subthreshold CBD doses and a NPSR antagonist implicated NPSR blockade as a potential mechanism contributing to CBD's effect, whereas co-administration of CBD and a CXCR4 antagonist suggested CXCR4 was not involved. However, the potent and selective CXCR4 antagonist AMD3100 reduced ethanol consumption.

CONCLUSIONS AND IMPLICATIONS

CBD represents a promising candidate to reduce voluntary alcohol consumption. Mechanisms driving CBD's alcohol-related effects remain unclear and may involve polypharmacology, including actions at the NPSR identified in the present study.

Cannabidiol reduces neuropathic pain and cognitive impairments through activation of spinal PPARγ

The purpose of this study was to evaluate the participation of spinal peroxisome proliferator-activated receptor gamma (PPARγ) in the antiallodynic effect of cannabidiol, the expression of PPARγ in sites relevant to the spinal nociceptive processing, and the effect of this cannabinoid on cognitive deficits induced by neuropathic pain in female mice. Either acute or repeated treatment with cannabidiol reduced tactile allodynia and spontaneous pain (flinching) in female neuropathic mice. Cannabidiol induced a greater effect in female mice. Pioglitazone partially reduced tactile allodynia, and this effect was fully blocked by the PPARγ antagonist GW9662. Likewise, intrathecal injection of cannabidiol reduced tactile allodynia, while PPARγ antagonist GW9662 or 5-HT1A receptor antagonist WAY-100635, but not the PPARα antagonist GW6479, partially prevented this effect. GW9662 and WAY-100635 administrated per se did not modify tactile allodynia in neuropathic female mice. Co-administration of GW9662 and WAY-100635 fully prevented the antiallodynic effect of cannabidiol in mice. Nerve injury up-regulated PPARγ expression at the spinal cord and dorsal root ganglia, while cannabidiol further enhanced nerve injury-induced up-regulation of PPARγ expression in both tissues. Repeated intrathecal injection of cannabidiol reduced tactile allodynia and several pain makers (ERK, p-ERK, p38MAPK and p-p38MAPK). In addition, this treatment restored nerve injury-induced interleukin-10 down-regulation and increased PPARγ expression at the spinal cord. Repeated treatment with cannabidiol also improved nerve injury-induced cognitive impairment in mice. These results provide compelling evidence for the involvement of PPARγ in the antiallodynic effect of cannabidiol in mice and highlight its multifaceted therapeutic potential in neuropathic pain management and its comorbidities. PERSPECTIVE: The present study reveals cannabidiol's dual effects in female mice by reducing neuropathic pain through spinal PPARγ and 5-HT1A receptor activation and ameliorating nerve injury-induced cognitive impairment. These findings may assist clinicians seeking new therapeutic approaches for managing neuropathic pain and its associated cognitive deficits.

Molecular Docking, Pharmacophore Modeling and ADMET Prediction of Novel Heterocyclic Leads as Glucokinase Activators

BACKGROUND

A pivotal impetus has driven the development of numerous small molecules aiming to improve therapeutic strategies for type 2 diabetes. Glucokinase (GK) activation has been offered a new realm of therapeutic antidiabetic activity with novel heterocyclic derivatives. In the context of antidiabetic drug design, GK is an interesting and newly validated target. A key enzyme needed for blood glucose homeostasis is Glucokinase, which is dysfunctional in individuals with type 2 diabetes. Heterocyclic derivatives are utilized in this innovative approach to activate GK enzymes as medicinal agents that will significantly improve type 2 diabetes management.

OBJECTIVES

To address type 2 diabetes, as well as minimize unwanted side effects, this research endeavor aimed to develop activators of glucokinase.

METHODS

A rigorous scrutiny was conducted of the Maybridge online repository, which houses a formidable collection of 53,000 lead compounds. A collection of 125 compounds that contain the thiazolidinedione core was selected from this extensive collection. The structures were generated using ChemDraw 2D, stabilized conformation with ChemBioDraw Ultra, and docked using Auto Dock Vina 1.5.6 in this methodology. In addition, log P was predicted online using the Swiss ADME algorithm. The PKCSM software was used to predict the toxicity of the leading compounds.

RESULTS

The highest binding affinity was found for AS72 and AS108 to GK receptors. GI absorption and excretion of these compounds were efficient due to Lipinski's Rule of Five compliance. When compared with the standard drugs Dorzagliatin (GKA) and MRK (co-crystallized ligand), these substances demonstrated a notable lack of AMES toxicity, skin sensitization, and hepatotoxicity.

CONCLUSION

In recent studies, lead molecules that possess enhanced pharmacokinetic profiles, increased binding affinity, and lower toxicity were developed to act as glucokinase activators.

Metabolic dysfunction and insulin sensitizers in acute and chronic disease

INTRODUCTION

The concept of insulin resistance has been a major topic for more than 5 decades. While there are several treatments that may impact insulin resistance, this pathology is uniquely addressed by mitochondrially directed thiazolidinedione (TZD) insulin sensitizers. Understanding of this mechanism of action and consideration of 'insulin resistance' as a consequence of metabolic inflammation allows a new paradigm for approaching chronic diseases.

AREAS COVERED

We review evolving understanding of the mitochondrial pyruvate carrier (MPC) as a mitochondrial mechanism of action of the TZD insulin sensitizers and discuss how reprogramming of mitochondrial metabolism impacts pleotropic pharmacology in multiple tissues. Additional lines of investigation are proposed.

EXPERT OPINION

A change in paradigm can facilitate rethinking of insulin sensitizers in clinical trials, specifically beyond the treatment of frank type 2 diabetes. There should be broader clinical evaluation of insulin sensitizers in combination with weight loss and lifestyle approaches across diseases/syndromes associated with insulin resistance. Finally, 'connecting all the dots' to unwind the interconnectedness of cell biology involved in the syndromes impacted by metabolic dysfunction and the efficacy of TZD insulin sensitizers may also uncover new molecular targets. New studies should facilitate the discovery and development of novel pharmacologic agents.

Coronary Plaque Regression and Fractional Flow Reserve Improvement in a Chronic Coronary Syndrome Case: Early Optimal Medical Therapy and Fractional Flow Reserve-Computed Tomography Follow-Up Strategy

Background: Optimal medical therapy (OMT) is increasingly recognized as a cornerstone in managing chronic coronary syndrome (CCS), offering a non-invasive alternative to percutaneous coronary intervention (PCI). Case Presentation: A 38-year-old male with diabetes, dyslipidemia, and hypertension was treated with early and comprehensive OMT, including statins, ezetimibe, sodium-glucose cotransporter 2 inhibitors (SGLT2i), pioglitazone, and renin-angiotensin system inhibitors. Insulin was introduced during the acute phase to stabilize glycemic control. His HbA1c decreased to 6.3% within 4 months. Results: Over 8 months, the patient experienced a reduction in coronary plaque burden and an improvement in fractional flow reserve (FFR) from 0.75 to 0.90, indicating enhanced coronary blood flow. Plaque volume burden decreased from 85% to 52% in key coronary segments. Conclusions: This case highlights the effectiveness of OMT, including statins, ezetimibe, SGLT2i, and pioglitazone, in achieving outcomes comparable to PCI. FFR-computed tomography follow-up is critical in guiding treatment decisions. Continued OMT is recommended if plaque stabilization is observed. If no improvement is observed, OMT should be intensified, and PCI considered as appropriate.

Pioglitazone treatment mitigates cardiovascular bioprosthetic degeneration in a chronic kidney disease model

Aims

Chronic kidney disease (CKD) is a risk factor for the development of cardiovascular diseases, e.g., atherosclerosis and calcific aortic valve disease, leading inevitably to valve replacement surgery. CKD patients with bioprosthetic cardiovascular grafts, in turn, have a higher risk of premature graft degeneration. Peroxisome proliferator-activated receptor gamma (PPARγ) activation by pioglitazone has cardio-renal protective properties, and research using a heterotopic valve implantation model has shown anti-degenerative effects of PPARγ activation on bioprosthetic valved grafts (BVG) in rats. The present work aims to analyze a potential protective effect of pioglitazone treatment on BVG in an adenine-induced rat model of CKD.

Methods and Results

BVG of Sprague Dawley rats were heterotopically implanted in Wistar rats in an infrarenal position for 4 and 8 weeks. Animals were distributed into three groups for each time point: 1) control group receiving standard chow, 2) CKD group receiving 0.25% adenine and 3) CKD + pioglitazone group (300 mg per kg of 0.25% adenine chow). BVG function was analyzed by echocardiography. Plasma analytes were determined and explanted grafts were analyzed by semi-quantitative real-time PCR, Western blot analysis, histology and immunohistology.PPARγ activation significantly reduced CKD-induced calcification of aortic and valvular segments of BVG by 44% and 53%, respectively. Pioglitazone treatment significantly also reduced CKD-induced intima hyperplasia by 60%. Plasma analysis revealed significantly attenuated potassium and phosphate levels after pioglitazone treatment. Moreover, PPARγ activation led to significantly decreased interleukin-6 gene expression (by 57%) in BVG compared to CKD animals. Pioglitazone treatment leads to functional improvement of BVG.

Conclusion

This study broadens the understanding of the potential value of PPARγ activation in cardio-renal diseases and delineates pioglitazone treatment as a valuable option to prevent bioprosthetic graft failure in CKD. Further mechanistic studies, e.g., using small molecules activating PPARγ signaling pathways, are necessary for the evaluation of involved mechanisms. Additionally, the translation into pre-clinical studies using large animals is intended as the next research project.

Antidiabetic drugs in Parkinson's disease

This review explores the intricate connections between type 2 diabetes (T2D) and Parkinson's disease (PD), both prevalent chronic conditions that primarily affect the aging population. These diseases share common early biochemical pathways that contribute to tissue damage. This manuscript also systematically compiles potential shared cellular mechanisms between T2D and PD and discusses the literature on the utilization of antidiabetic drugs as potential therapeutic options for PD. This review encompasses studies investigating the experimental and clinical efficacy of antidiabetic drugs in the treatment of Parkinson's disease, along with the proposed mechanisms of action. The exploration of the benefits of antidiabetic drugs in PD presents a promising avenue for the treatment of this neurodegenerative disorder.

MASLD/MASH and type 2 diabetes: Two sides of the same coin? From single PPAR to pan-PPAR agonists

Type 2 diabetes (T2D) and metabolic dysfunction-associated steatotic liver disease (MASLD), mainly related to nutrition and lack of physical activity, are both very common conditions, share several disease pathways and clinical manifestations, and increasingly co-occur with disease progression. Insulin resistance is an upstream node in the biology of both conditions and triggers liver parenchymal injury, inflammation and fibrosis. Peroxisome proliferator-activated receptor (PPAR) nuclear transcription factors are master regulators of energy homeostasis - insulin signaling in liver, adipose and skeletal muscle tissue - and affect immune and fibrogenesis pathways. Among distinct yet overlapping effects, PPARα regulates lipid metabolism and energy expenditure, PPARβ/δ has anti-inflammatory effects and increases glucose uptake by skeletal muscle, while PPARγ improves insulin sensitivity and exerts direct antifibrotic effects on hepatic stellate cells. Together PPARs thus represent pharmacological targets across the entire biology of MASH. Single PPAR agonists are approved for hypertriglyceridemia (PPARα) and T2D (PPARγ), but these, as well as dual PPAR agonists, have shown mixed results as anti-MASH treatments in clinical trials. Agonists of all three PPAR isoforms have the potential to improve the full disease spectrum from insulin resistance to fibrosis, and correspondingly to improve cardiometabolic and hepatic health, as has been shown (phase II data) with the pan-PPAR agonist lanifibranor.

Prospective de novo drug design with deep interactome learning

De novo drug design aims to generate molecules from scratch that possess specific chemical and pharmacological properties. We present a computational approach utilizing interactome-based deep learning for ligand- and structure-based generation of drug-like molecules. This method capitalizes on the unique strengths of both graph neural networks and chemical language models, offering an alternative to the need for application-specific reinforcement, transfer, or few-shot learning. It enables the "zero-shot" construction of compound libraries tailored to possess specific bioactivity, synthesizability, and structural novelty. In order to proactively evaluate the deep interactome learning framework for protein structure-based drug design, potential new ligands targeting the binding site of the human peroxisome proliferator-activated receptor (PPAR) subtype gamma are generated. The top-ranking designs are chemically synthesized and computationally, biophysically, and biochemically characterized. Potent PPAR partial agonists are identified, demonstrating favorable activity and the desired selectivity profiles for both nuclear receptors and off-target interactions. Crystal structure determination of the ligand-receptor complex confirms the anticipated binding mode. This successful outcome positively advocates interactome-based de novo design for application in bioorganic and medicinal chemistry, enabling the creation of innovative bioactive molecules.

Fasting upregulates the monocarboxylate transporter MCT1 at the rat blood-brain barrier through PPAR δ activation

BACKGROUND

The blood-brain barrier (BBB) is pivotal for the maintenance of brain homeostasis and it strictly regulates the cerebral transport of a wide range of endogenous compounds and drugs. While fasting is increasingly recognized as a potential therapeutic intervention in neurology and psychiatry, its impact upon the BBB has not been studied. This study was designed to assess the global impact of fasting upon the repertoire of BBB transporters.

METHODS

We used a combination of in vivo and in vitro experiments to assess the response of the brain endothelium in male rats that were fed ad libitum or fasted for one to three days. Brain endothelial cells were acutely purified and transcriptionaly profiled using RNA-Seq. Isolated brain microvessels were used to assess the protein expression of selected BBB transporters through western blot. The molecular mechanisms involved in the adaptation to fasting were investigated in primary cultured rat brain endothelial cells. MCT1 activity was probed by in situ brain perfusion.

RESULTS

Fasting did not change the expression of the main drug efflux ATP-binding cassette transporters or P-glycoprotein activity at the BBB but modulated a restrictive set of solute carrier transporters. These included the ketone bodies transporter MCT1, which is pivotal for the brain adaptation to fasting. Our findings in vivo suggested that PPAR δ, a major lipid sensor, was selectively activated in brain endothelial cells in response to fasting. This was confirmed in vitro where pharmacological agonists and free fatty acids selectively activated PPAR δ, resulting in the upregulation of MCT1 expression. Moreover, dosing rats with a specific PPAR δ antagonist blocked the upregulation of MCT1 expression and activity induced by fasting.

CONCLUSIONS

Altogether, our study shows that fasting affects a selected set of BBB transporters which does not include the main drug efflux transporters. Moreover, we describe a previously unknown selective adaptive response of the brain vasculature to fasting which involves PPAR δ and is responsible for the up-regulation of MCT1 expression and activity. Our study opens new perspectives for the metabolic manipulation of the BBB in the healthy or diseased brain.

Current knowledge of bone-derived factor osteocalcin: its role in the management and treatment of diabetes mellitus, osteoporosis, osteopetrosis and inflammatory joint diseases

Osteocalcin (OC) is the most abundant non-collagenous and osteoblast-secreted protein in bone. It consists of two forms such as carboxylated OC (cOC) and undercarboxylated OC (ucOC). While cOC promotes bone mineralization and increases bone strength, ucOC is regarded an endocrinologically active form that may have several functions in multiple end organs and tissues. Total OC (tOC) includes both of these forms (cOC and ucOC) and is considered a marker of bone turnover in clinical settings. Most of the data on OC is limited to preclinical studies and therefore may not accurately reflect the situation in clinical conditions. For the stated reason, the aim of this review was not only to summarize current knowledge of all forms of OC and characterize its role in diabetes mellitus, osteoporosis, osteopetrosis, inflammatory joint diseases, but also to provide new interpretations of its involvement in the management and treatment of aforementioned diseases. In this context, special emphasis was placed on available clinical trials. Significantly lower levels of tOC and ucOC could be associated with the risk of type 2 diabetes mellitus. On the contrary, tOC level does not seem to be a good indicator of high bone turnover status in postmenopausal osteoporosis, osteoarthritis and rheumatoid arthritis. The associations between several pharmacological drugs used to treat all disorders mentioned above and OC levels have also been provided. From this perspective, OC may serve as a medium through which certain medications can influence glucose metabolism, body weight, adiponectin secretion, and synovial inflammation.

Adolescent polycystic ovary syndrome without obesity: HOTAIR rs1443512 genotype relates to fat mass and to the redistribution of fat mass on low-dose pioglitazone

INTRODUCTION

Adolescent polycystic ovary syndrome (PCOS) is characterized by androgen excess and oligo-amenorrhea, and often results from ectopic lipid storage due to a mismatch between early adipogenesis and later lipogenesis. Endogenous HOX transcript antisense RNA (HOTAIR) and exogenous pioglitazone are enhancers of subcutaneous adipogenesis, particularly in the gluteofemoral region. The A allele of HOTAIR rs1443512 is an equivalent of a natural knock-down and is, thus, a candidate to influence the distribution of fat mass, and also the redistribution of fat mass by pioglitazone in adolescent PCOS-without-obesity.

SUBJECTS AND METHODS

We performed two post hoc analyses by HOTAIR rs1443512 genotype. In the first, we analyzed the pooled pre-treatment data (auxology; endocrinology; body composition by dual X-ray absorptiometry; abdominal fat distribution by magnetic resonance imaging) of 65 adolescent girls with PCOS-without-obesity in three reported studies (ISRCTN45546616; ISRCTN29234515; ISRCTN11062950). In the second, we analyzed the results of 24 adolescent girls with PCOS-without-obesity, who received pioglitazone (7.5 mg/d for 1 year) as part of a randomized combination treatment (with spironolactone and metformin) in two reported studies (ISRCTN29234515; ISRCTN11062950). All data had been obtained in a blinded-to-genotype way.

RESULTS

The pre-treatment data disclosed that the girls-with-A-allele of HOTAIR rs1443512 had developed PCOS with a lower BMI (22.3 ± 2.3 kg/m2; N = 17) than the other girls (24.1 ± 2.7 kg/m2; N = 48), this difference being essentially attributable to a lower fat mass (mean difference 4.6 kg; P < 0.01). On low-dose pioglitazone, girls-with-A-allele (N = 12) raised their fat mass while the other girls (N = 12) did not (total fat mass + 2.2 ± 1.8 kg vs  - 0.9 ± 2.2 kg; P < 0.001), particularly in the gynoid area (gluteofemoral fat + 0.6 ± 0.4 kg vs  - 0.1 ± 0.5 kg; hip circumference + 2.3 ± 1.9 cm vs  - 1.7 ± 3.1 cm; both P < 0.001).

CONCLUSION

The present findings suggest that the HOTAIR rs1443512 genotype influences not only the distribution of fat mass in adolescent girls with PCOS-without-obesity but also the redistribution of fat mass during prolonged treatment with low-dose pioglitazone.

TRIAL REGISTRATION

ISRCTN45546616 ( https://doi.org/10.1186/ISRCTN45546616 ). ISRCTN29234515 ( https://doi.org/10.1186/ISRCTN29234515 ). ISRCTN11062950 ( https://doi.org/10.1186/ISRCTN11062950 ).

A structural basis for the activation of peroxisome proliferator-activated receptor gamma (PPARγ) by perfluorooctanoic acid (PFOA)

Perfluorooctanoic acid (PFOA) is a widespread environmental pollutant of the perfluoroalkyl substance (PFAS) class that is extremely resistant to environmental and metabolic degradation, leading to bioaccumulation. PFOA exposure has been linked to many health effects including endocrine disruption and metabolic dysregulation, but our understanding of the molecular mechanisms resulting in these outcomes remains incomplete. One target affected by PFOA is the ligand regulated nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ) which plays a critical role in controlling metabolic homeostasis through regulating processes such as adipogenesis, glucose homeostasis, inflammation and osteogenesis. It has been previously established that PFOA activates PPARγ through binding to the PPARγ ligand binding domain (PPARγ LBD) leading to increased expression of PPARγ controlled target genes. However, the mechanism by which PFOA achieves this has remained elusive. Here, we employed a combination of X-ray crystallography and fluorescence polarization assays to provide a structural basis for PFOA mediated activation of PPARγ via binding to the PPARγ LBD. Using X-ray crystallography, the cocrystal structure of the PPARγ LBD:PFOA complex was solved. This revealed that PFOA occupies three distinct sites, two within the PPARγ LBD and one within the activation function 2 (AF2) on the protein surface. Structural comparison of PFOA binding with previously reported PPARγ:ligand complexes supports that PFOA activates PPARγ by a partial agonist mechanism at micromolar concentrations. Fluorescence polarization assays also revealed that PFOA binding to the AF2 is unlikely to occur in a cellular context and confirmed that PFOA behaves as a partial agonist in vitro, weakly recruiting a coactivator peptide to the AF2 of the PPARγ LBD. This discovery provides an advancement in understanding PFOA mediated regulation of PPARγ, giving new insight regarding regulation of PPARγ by PFAS and PFAS substitutes in general and can be applied to the design and assessment of safer PFAS.

Vimentin protein is a factor for decreasing breast cancer cell proliferation co-culture with human bone marrow-derived mesenchymal stem cells pre-treated with thiazolidinedione solutions

BACKGROUND

Our previous study investigated the levels of soluble growth factors in the conditioned media of bone marrow-derived mesenchymal stem cells (BMSCs) pre-treated with thiazolidinedione solutions. The present study aimed to investigate the complex intracellular proteins extracted from BMSCs pre-treated with pioglitazone and/or rosiglitazone using proteomics.

METHODS

The proliferative effect of the identified protein on MCF-7 cells that interacted non-adhesively with BMSCs pre-treated with pioglitazone and/or rosiglitazone was evaluated using cell culture inserts and conditioned media. The mRNA expression of proliferation and lipid accumulation markers was also evaluated in the interacted MCF-7 cells by reverse transcription-quantitative PCR. Finally, the correlation between the identified protein and fibroblast growth factor 4 (FGF-4) protein in the conditioned media of the pre-treated BMSCs was evaluated by ELISA.

RESULTS

The present study identified vimentin as the specific protein among the complex intracellular proteins that likely plays a role in MCF-7 cell proliferation when the breast cancer cells interacted non-adhesively with BMSCs pre-treated with a combination of pioglitazone and rosiglitazone. The inhibition of this protein promoted the proliferation of MCF-7 cells when the breast cancer cells interacted with pre-treated BMSCs. Gene expression analysis indicated that pre-treatment of BMSCs with a combination of pioglitazone and rosiglitazone decreased the mRNA expression of Ki67 and proliferating cell nuclear antigen in MCF-7 cells. The pre-treatment did not induce mRNA expression of PPARγ, which is a sign of lipid accumulation. The level of vimentin protein was also associated with the FGF-4 protein expression level in the conditioned media of the pre-treated BMSCs. Bioinformatics analysis revealed that vimentin regulated the expression of FGF-4 through its interaction with SRY-box 2 and POU class 5 homeobox 1.

CONCLUSIONS

The present study identified a novel intracellular protein that may represent the promising target in pre-treated BMSCs to decrease the proliferation of breast cancer MCF-7 cells for human health and wellness.

Treating NASH by targeting peroxisome proliferator-activated receptors

The pathophysiology of non-alcoholic steatohepatitis (NASH) encompasses a complex set of intra- and extrahepatic driving mechanisms, involving numerous metabolic, inflammatory, vascular and fibrogenic pathways. The peroxisome proliferator-activated receptors (PPARs) α, β/δ and γ belong to the nuclear receptor family of ligand-activated transcription factors. Activated PPARs modulate target tissue transcriptomic profiles, enabling the body's adaptation to changing nutritional, metabolic and inflammatory environments. PPARs hence regulate several pathways involved in NASH pathogenesis. Whereas single PPAR agonists exert robust anti-NASH activity in several preclinical models, their clinical effects on histological endpoints of NASH resolution and fibrosis regression appear more modest. Simultaneous activation of several PPAR isotypes across different organs and within-organ cell types, resulting in pleiotropic actions, enhances the therapeutic potential of PPAR agonists as pharmacological agents for NASH and NASH-related hepatic and extrahepatic morbidity, with some compounds having already shown clinical efficacy on histological endpoints.

International Union of Basic and Clinical Pharmacology CXIII: Nuclear Receptor Superfamily-Update 2023

The NR superfamily comprises 48 transcription factors in humans that control a plethora of gene network programs involved in a wide range of physiologic processes. This review will summarize and discuss recent progress in NR biology and drug development derived from integrating various approaches, including biophysical techniques, structural studies, and translational investigation. We also highlight how defective NR signaling results in various diseases and disorders and how NRs can be targeted for therapeutic intervention via modulation via binding to synthetic lipophilic ligands. Furthermore, we also review recent studies that improved our understanding of NR structure and signaling. SIGNIFICANCE STATEMENT: Nuclear receptors (NRs) are ligand-regulated transcription factors that are critical regulators of myriad physiological processes. NRs serve as receptors for an array of drugs, and in this review, we provide an update on recent research into the roles of these drug targets.

Selective PPAR-Delta/PPAR-Gamma Activation Improves Cognition in a Model of Alzheimer's Disease

Background: The continuously increasing association of Alzheimer's disease (AD) with increased mortality rates indicates an unmet medical need and the critical need for establishing novel molecular targets for therapeutic potential. Agonists for peroxisomal proliferator activating receptors (PPAR) are known to regulate energy in the body and have shown positive effects against Alzheimer's disease. There are three members of this class (delta, gamma, and alpha), with PPAR-gamma being the most studied, as these pharmaceutical agonists offer promise for AD because they reduce amyloid beta and tau pathologies, display anti-inflammatory properties, and improve cognition. However, they display poor brain bioavailability and are associated with several adverse side effects on human health, thus limiting their clinical application. Methods: We have developed a novel series of PPAR-delta and PPAR-gamma agonists in silico with AU9 as our lead compound that displays selective amino acid interactions focused upon avoiding the Tyr-473 epitope in the PPAR-gamma AF2 ligand binding domain. Results: This design helps to avoid the unwanted side effects of current PPAR-gamma agonists and improve behavioral deficits and synaptic plasticity while reducing amyloid-beta levels and inflammation in 3xTgAD animals. Conclusions: Our innovative in silico design of PPAR-delta/gamma agonists may offer new perspectives for this class of agonists for AD.

PPAR-γ signaling in nonalcoholic fatty liver disease: Pathogenesis and therapeutic targets

Non-alcoholic fatty liver disease (NAFLD), currently the leading cause of global chronic liver disease, has emerged as a major public health problem, more efficient therapeutics of which are thus urgently needed. Peroxisome proliferator-activated receptor γ (PPAR-γ), ligand-activated transcription factors of the nuclear hormone receptor superfamily, is considered a crucial metabolic regulator of hepatic lipid metabolism and inflammation. The role of PPAR-γ in the pathogenesis of NAFLD is gradually being recognized. Here, we outline the involvement of PPAR-γ in the pathogenesis of NAFLD through adipogenesis, insulin resistance, inflammation, oxidative stress, endoplasmic reticulum stress, and fibrosis. In addition, the evidence for PPAR-γ- targeted therapy for NAFLD are summarized. Altogether, PPAR-γ is a promising therapeutic target for NAFLD, and the development of drugs that can balance the beneficial and undesirable effects of PPAR-γ will bring new light to NAFLD patients.

Screening for DAX1/EWS-FLI1 functional inhibitors identified dihydroorotate dehydrogenase as a therapeutic target for Ewing's sarcoma

OBJECTIVE

EWS-FLI1 is the most common oncogenic fusion protein in Ewing's sarcoma family tumors (ESFTs). DAX1, an orphan member of the nuclear receptor superfamily, is up-regulated by EWS-FLI1 and plays a key role in the transformed phenotype of ESFTs.

METHODS

To discover a functional inhibitor of DAX1 and EWS-FLI1, we screened small-molecular inhibitors using a DAX1 reporter assay system.

RESULTS

K-234 and its derivatives, which were dihydroorotate dehydrogenase (DHODH) inhibitors, showed inhibitory effects in the reporter assay. K-234 inhibited the growth of Ewing's sarcoma with various fusion types, and K-234 derivatives altered the expression of EWS-FLI1-regulated genes. The DAX1 expression had no effect on the growth inhibitory effect of the K-234 derivatives, while DHODH overexpression or uridine treatment attenuated their inhibitory effects, suggesting that inhibition by K-234 derivatives occurs through DHODH inhibition. An in vivo study showed that a K-234 derivative clearly inhibited tumor growth in an Ewing's sarcoma xenograft mouse model.

CONCLUSION

Taken together, the present results suggest that DHODH inhibitors can inhibit the function of DAX1/EWS-FLI1 in ESFTs and might be a therapeutic agent with potent anti-tumor activity for Ewing's sarcoma patients.

Neuroprotective and Anti-Inflammatory Effects of Pioglitazone on Parkinson's Disease: A Comprehensive Narrative Review of Clinical and Experimental Findings

Parkinson's disease (PD) is a chronic and progressive neurological disorder characterized by the degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNc). The pathogenesis of PD is strongly related to mitochondrial dysfunction, oxidative stress, and neuroinflammation. This indicates that PD can be treated with anti-oxidative substitutes and anti-inflammatory compounds. The neuroprotective and anti-inflammatory effects of peroxisome proliferator-activated receptor γ (PPAR-γ) agonists decrease cell death and halt the increase in neurodegeneration, which is why they have been given a lot of importance in research. Antidiabetic and anti-inflammatory effects have been observed to be generated by pioglitazone (PG), a selective peroxisome proliferator-activated receptor γ (PPAR-γ) agonist that regulates neural plasticity in various neurodegenerative disorders. The neuroprotective and anti-inflammatory effects of PG are assessed in this article. It was found that the patients with DM who received PG treatment were noticeably at a lower risk of PD. However, some clinical studies have not proven a strong link between the therapeutic effects of PG on PD. As per suggestions of preclinical studies, the therapeutic effects of PG treatment include; increased life expectancy of neurons, decreased oxidative stress, halted microglial activity, lower inflammation (reduced NF-κB, COX-2, and iNOS), reduced mitochondrial dysfunction, rise in motor function (motor agility) and non-motor function (lowered cognitive dysfunction). In conclusion, we determined that PG exerts neuroprotective and anti-inflammatory effects in PD models and it can be considered a potential therapeutic candidate for PD.

PPAR-Targeted Therapies in the Treatment of Non-Alcoholic Fatty Liver Disease in Diabetic Patients

Peroxisome proliferator-activated receptors (PPAR), ligand-activated transcription factors of the nuclear hormone receptor superfamily, have been identified as key metabolic regulators in the liver, skeletal muscle, and adipose tissue, among others. As a leading cause of liver disease worldwide, non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) cause a significant burden worldwide and therapeutic strategies are needed. This review provides an overview of the evidence on PPAR-targeted treatment of NAFLD and NASH in individuals with type 2 diabetes mellitus. We considered current evidence from clinical trials and observational studies as well as the impact of treatment on comorbid metabolic conditions such as obesity, dyslipidemia, and cardiovascular disease. Future areas of research, such as possible sexually dimorphic effects of PPAR-targeted therapies, are briefly reviewed.

Prescription Drugs and Mitochondrial Metabolism

Mitochondria are central to the physiology and survival of nearly all eukaryotic cells and house diverse metabolic processes including oxidative phosphorylation, reactive oxygen species buffering, metabolite synthesis/exchange, and Ca2+ sequestration. Mitochondria are phenotypically heterogeneous and this variation is essential to the complexity of physiological function among cells, tissues, and organ systems. As a consequence of mitochondrial integration with so many physiological processes, small molecules that modulate mitochondrial metabolism induce complex systemic effects. In the case of many common prescribed drugs, these interactions may contribute to drug therapeutic mechanisms, induce adverse drug reactions, or both. The purpose of this article is to review historical and recent advances in the understanding of the effects of prescription drugs on mitochondrial metabolism. Specific 'modes' of xenobiotic-mitochondria interactions are discussed to provide a set of qualitative models that aid in conceptualizing how the mitochondrial energy transduction system may be affected. Findings of recent in vitro high-throughput screening studies are reviewed, and a few candidate drug classes are chosen for additional brief discussion (i.e. antihyperglycemics, antidepressants, antibiotics, and antihyperlipidemics). Finally, recent improvements in pharmacokinetic models that aid in quantifying systemic effects of drug-mitochondria interactions are briefly considered.

Pioglitazone, Bladder Cancer and the Presumption of Innocence

BACKGROUND

Thiazolidinediones are potent exogenous agonists of PPAR-γ, which augment the effects of insulin to its cellular targets and mainly at the level of adipose tissue. Pioglitazone, the main thiazolidinedione in clinical practice, has shown cardiovascular and renal benefits in patients with type 2 diabetes, durable reduction of glycated hemoglobulin levels, important improvements of several components of the metabolic syndrome and beneficial effects of non-alcoholic fatty liver disease.

OBJECTIVE

Despite all of its established advantages, the controversy for an increased risk of developing bladder cancer, combined with the advent of newer drug classes that achieved major cardiorenal effects have significantly limited its use spreading a persistent shadow of doubt for its future role.

METHODS

Pubmed, Google and Scope databases have been thoroughly searched and relevant studies were selected.

RESULTS

This paper explores thoroughly both in vitro and in vivo (animal models and humans) studies that investigated the possible association of pioglitazone with bladder cancer.

CONCLUSION

Currently the association of pioglitazone with bladder cancer cannot be based on solid evidence. This evidence cannot justify its low clinical administration, especially in the present era of individualised treatment strategies. Definite clarification of this issue is imperative and urgently anticipated from future high quality and rigorous pharmacoepidemiologic research, keeping in mind its unique mechanism of action and its significant pleiotropic effects.

Modulatory effects of pioglitazone as a ligand for the peroxisome proliferator-activated receptor on semen quality and fertility potential of broiler breeder roosters

Fertility potential in roosters is a crucial topic in broiler breeder reproduction which is thought to be associated with age. This study aims to investigate effects of 2 levels of pioglitazone (PIO) supplementation on peroxisome proliferator-activated receptor gamma (PPAR-γ) expression, semen quality, and fertility parameters of aged broiler breeder roosters. The efficacy of PIO was divided into 2 sections: receptor-dependent and receptor-independent. Expression of PPAR-γ mRNA and protein was assessed in sperm to monitor receptor-dependent actions. Sperm motility, velocity parameters, viability, mitochondrial activity, and apoptosis were assessed for the receptor-independent actions. Broiler breeder roosters were randomly assigned to 3 groups: 1) control received a basal diet (CTRL); 2) PIO-5 received a basal diet supplemented with 5 mg PIO/bird/day, and 3) PIO-10 received a basal diet supplemented with 10 mg PIO/bird/day. In addition, semen samples were collected from 24 Ross broiler breeder roosters at 30, 43, and 53 wk of age. Effects of PIO were significant in terms of total motility, straight-line velocity, mitochondrial activity, and apoptosis (P ≤ 0.05). Total motility, straight-line velocity and mitochondrial activity improved in both PIO groups (P ≤ 0.05) along with a significant reduction in early and late apoptosis in the PIO groups (P ≤ 0.05). Pioglitazone addition affected total motility, mitochondrial activity, early apoptosis and late apoptosis in a linearly and quadratically manner (P < 0.05). PPAR-γ mRNA and protein expression were not significantly upregulated by the different doses of PIO (P > 0.05). Similarly, fertility performance was not significantly changed in the PIO groups (P > 0.05). Moreover, PIO improved mitochondrial activity and decreased the apoptosis rate in the sperm of aged broiler breeder roosters. These improvements were associated with the receptor-independent actions of PIO and the mechanism of action of PIO did not appear to be affected by the PPAR-γ receptor in broiler breeder roosters.

Xenobiotic-Induced Aggravation of Metabolic-Associated Fatty Liver Disease

Metabolic-associated fatty liver disease (MAFLD), which is often linked to obesity, encompasses a large spectrum of hepatic lesions, including simple fatty liver, steatohepatitis, cirrhosis and hepatocellular carcinoma. Besides nutritional and genetic factors, different xenobiotics such as pharmaceuticals and environmental toxicants are suspected to aggravate MAFLD in obese individuals. More specifically, pre-existing fatty liver or steatohepatitis may worsen, or fatty liver may progress faster to steatohepatitis in treated patients, or exposed individuals. The mechanisms whereby xenobiotics can aggravate MAFLD are still poorly understood and are currently under deep investigations. Nevertheless, previous studies pointed to the role of different metabolic pathways and cellular events such as activation of de novo lipogenesis and mitochondrial dysfunction, mostly associated with reactive oxygen species overproduction. This review presents the available data gathered with some prototypic compounds with a focus on corticosteroids and rosiglitazone for pharmaceuticals as well as bisphenol A and perfluorooctanoic acid for endocrine disruptors. Although not typically considered as a xenobiotic, ethanol is also discussed because its abuse has dire consequences on obese liver.

Neutral sphingomyelinase-2 and cardiometabolic diseases

Sphingolipids, in particular ceramides, play vital role in pathophysiological processes linked to metabolic syndrome, with implications in the development of insulin resistance, pancreatic ß-cell dysfunction, type 2 diabetes, atherosclerosis, inflammation, nonalcoholic steatohepatitis, and cancer. Ceramides are produced by the hydrolysis of sphingomyelin, catalyzed by different sphingomyelinases, including neutral sphingomyelinase 2 (nSMase2), whose dysregulation appears to underlie many of the inflammation-related pathologies. In this review, we discuss the current knowledge on the biochemistry of nSMase2 and ceramide production and its regulation by inflammatory cytokines, with particular reference to cardiometabolic diseases. nSMase2 contribution to pathogenic processes appears to involve cyclical feed-forward interaction with proinflammatory cytokines, such as TNF-α and IL-1ß, which activate nSMase2 and the production of ceramides, that in turn triggers the synthesis and release of inflammatory cytokines. We elaborate these pathogenic interactions at the molecular level and discuss the potential therapeutic benefits of inhibiting nSMase2 against inflammation-driven cardiometabolic diseases.

Functional effects of berberine in modulating mitochondrial dysfunction and inflammatory response in the respective amyloidogenic cells and activated microglial cells - In vitro models simulating Alzheimer's disease pathology

AIM

Berberine (BBR) is an alkaloid extracted from Coptidis Rhizoma, also known as Huang-Lian. Huang-Lian has been used extensively in traditional Chinese medicine for the treatment of various diseases, including diabetes and dementia. Because Alzheimer's disease (AD) is a complex disease that involves various pathophysiological changes, the diverse neuroprotective effects of BBR may be useful for improving the brain's energy state at an early stage of the disease.

MAIN METHODS

We performed extracellular flux and ¹H NMR-based metabolic profiling analyses to investigate the effects of BBR on metabolic processes in these cells. Pioglitazone (PIO), a peroxisome proliferator-activated receptor-γ (PPARγ) agonist has been studied extensively for the treatment of AD. We explored the combination dosing effects of BBR and PIO in vitro, then leveraged computational methods to explain the experimental finding.

KEY FINDINGS

BBR demonstrates potential in modulating the mitochondrial bioenergetics and attenuating dysfunction of the primary energy and glutathione metabolism pathways in an AD cell model. It also suppresses basal respiration and reduces the production of pro-inflammatory cytokines in activated microglial cells. Both experimental and computational observations indicate that BBR and PIO have comparable binding affinities to the PPARγ protein, suggesting both drugs may have some overlapping effects for AD.

SIGNIFICANCE

BBR exerts beneficial effects on disrupted metabolic processes in amyloidogenic cells and activated microglial cells, which are important for preventing or delaying early-stage disease progression. The choice of BBR or PIO for AD treatment depends on their respective pharmacokinetic profiles, delivery, efficacy and safety, and warrants further study.

Reassessment of Pioglitazone for Alzheimer's Disease

Alzheimer's disease is a quintessential 'unmet medical need', accounting for ∼65% of progressive cognitive impairment among the elderly, and 700,000 deaths in the United States in 2020. In 2019, the cost of caring for Alzheimer's sufferers was $244B, not including the emotional and physical toll on caregivers. In spite of this dismal reality, no treatments are available that reduce the risk of developing AD or that offer prolonged mitiagation of its most devestating symptoms. This review summarizes key aspects of the biology and genetics of Alzheimer's disease, and we describe how pioglitazone improves many of the patholophysiological determinants of AD. We also summarize the results of pre-clinical experiments, longitudinal observational studies, and clinical trials. The results of animal testing suggest that pioglitazone can be corrective as well as protective, and that its efficacy is enhanced in a time- and dose-dependent manner, but the dose-effect relations are not monotonic or sigmoid. Longitudinal cohort studies suggests that it delays the onset of dementia in individuals with pre-existing type 2 diabetes mellitus, which small scale, unblinded pilot studies seem to confirm. However, the results of placebo-controlled, blinded clinical trials have not borne this out, and we discuss possible explanations for these discrepancies.

Atherosclerosis: Conventional intake of cardiovascular drugs versus delivery using nanotechnology - A new chance for causative therapy?

Atherosclerosis is the leading cause of death in developed countries. The pathogenetic mechanism relies on a macrophage-based immune reaction to low density lipoprotein (LDL) deposition in blood vessels with dysfunctional endothelia. Thus, atherosclerosis is defined as a chronic inflammatory disease. A plethora of cardiovascular drugs have been developed and are on the market, but the major shortcoming of standard medications is that they do not address the root cause of the disease. Statins and thiazolidinediones that have recently been recognized to exert specific anti-atherosclerotic effects represent a potential breakthrough on the horizon. But their whole potential cannot be realized due to insufficient availability at the pathological site and severe off-target effects. The focus of this review will be to elaborate how both groups of drugs could immensely profit from nanoparticulate carriers. This delivery principle would allow for their accumulation in target macrophages and endothelial cells of the atherosclerotic plaque, increasing bioavailability where it is needed most. Based on the analyzed literature we conclude design criteria for the delivery of statins and thiazolidinediones with nanoparticles for anti-atherosclerotic therapy. Nanoparticles need to be below a diameter of 100 nm to accumulate in the atherosclerotic plaque and should be fabricated using biodegradable materials. Further, the thiazolidinediones or statins must be encapsulated into the particle core, because especially for thiazolidindiones the uptake into cells is prerequisite for their mechanism of action. For optimal uptake into targeted macrophages and endothelial cells, the ideal particle should present ligands on its surface which bind specifically to scavenger receptors. The impact of statins on the lectin-type oxidized LDL receptor 1 (LOX1) seems particularly promising because of its outstanding role in the inflammatory process. Using this pioneering concept, it will be possible to promote the impact of statins and thiazolidinediones on macrophages and endothelial cells and significantly enhance their anti-atherosclerotic therapeutic potential.

Epo receptor signaling in macrophages alters the splenic niche to promote erythroid differentiation

Anemic stress induces stress erythropoiesis, which rapidly generates new erythrocytes to restore tissue oxygenation. Stress erythropoiesis is best understood in mice where it is extramedullary and occurs primarily in the spleen. However, both human and mouse stress erythropoiesis use signals and progenitor cells that are distinct from steady-state erythropoiesis. Immature stress erythroid progenitors (SEPs) are derived from short-term hematopoietic stem cells. Although the SEPs are capable of self-renewal, they are erythroid restricted. Inflammation and anemic stress induce the rapid proliferation of SEPs, but they do not differentiate until serum erythropoietin (Epo) levels increase. Here we show that rather than directly regulating SEPs, Epo promotes this transition from proliferation to differentiation by acting on macrophages in the splenic niche. During the proliferative stage, macrophages produce canonical Wnt ligands that promote proliferation and inhibit differentiation. Epo/Stat5-dependent signaling induces the production of bioactive lipid mediators in macrophages. Increased production of prostaglandin J2 (PGJ2) activates peroxisome proliferator-activated receptor γ (PPARγ)-dependent repression of Wnt expression, whereas increased production of prostaglandin E2 (PGE2) promotes the differentiation of SEPs.

Yulink, predicted from evolutionary analysis, is involved in cardiac function

Background

The comparative evolutionary genomics analysis was used to study the functions of novel Ka/Ks-predicted human exons in a zebrafish model. The Yulink (MIOS, Entrez Gene: 54,468), a conserved gene from zebrafish to human with WD40 repeats at N-terminus, was identified and found to encode an 875 amino acid in human. The biological function of this Yulink gene in cardiomyocytes remains unexplored. The purpose of this study is to determine the involvement of Yulink in the functions of cardiomyocytes and to investigate its molecular regulatory mechanism.

Methods

Knockdown of Yulink was performed using morpholino or shRNA in zebrafish, mouse HL-1 cardiomyocytes, and human iPSC-derived cardiomyocytes. The expression levels of mRNA and protein were quantified by qPCR and western blots. Other methods including DNA binding, ligand uptake, agonists treatment and Ca²⁺ imaging assays were used to study the molecular regulatory mechanism by Yulink. Statistical data were shown as mean ± SD or mean ± standard error.

Results

The knockdown of yulink with three specific morpholinos in zebrafish resulted in cardiac dysfunctions with pericardial edema, decreased heart beats and cardiac output. The Yulink knockdown in mouse HL-1 cardiomyocytes disrupted Ca²⁺ cycling, reduced DNA binding activity of PPARγ (peroxisome proliferator-activated receptor gamma) and resulted in a reduction of Serca2 (sarcoplasmic reticulum Ca²⁺ ATPase 2) expression. Expression of Serca2 was up-regulated by PPARγ agonists and down-regulated by PPARγ-shRNA knockdown, suggesting that Yulink regulates SERCA2 expression through PPARγ in mouse HL-1 cardiomyocytes. On the other hand, YULINK, PPARγ or SERCA2 over-expression rescued the phenotypes of Yulink KD cells. In addition, knockdown of YULINK in human iPSC-derived cardiomyocytes also disrupted Ca²⁺ cycling via decreased SERCA2 expression.

Conclusions

Overall, our data showed that Yulink is an evolutionarily conserved gene from zebrafish to human. Mechanistically Yulink regulated Serca2 expression in cardiomyocytes, presumably mediated through PPARγ nuclear entry. Deficiency of Yulink in mouse and human cardiomyocytes resulted in irregular Ca²⁺ cycling, which may contribute to arrhythmogenesis.

Nonalcoholic steatohepatitis: the role of peroxisome proliferator-activated receptors

The increasing epidemic of obesity worldwide is linked to serious health effects, including increased prevalence of type 2 diabetes mellitus, cardiovascular disease and nonalcoholic fatty liver disease (NAFLD). NAFLD is the liver manifestation of the metabolic syndrome and includes the spectrum of liver steatosis (known as nonalcoholic fatty liver) and steatohepatitis (known as nonalcoholic steatohepatitis), which can evolve into progressive liver fibrosis and eventually cause cirrhosis. Although NAFLD is becoming the number one cause of chronic liver diseases, it is part of a systemic disease that affects many other parts of the body, including adipose tissue, pancreatic β-cells and the cardiovascular system. The pathomechanism of NAFLD is multifactorial across a spectrum of metabolic derangements and changes in the host microbiome that trigger low-grade inflammation in the liver and other organs. Peroxisome proliferator-activated receptors (PPARs) are a group of nuclear regulatory factors that provide fine tuning for key elements of glucose and fat metabolism and regulate inflammatory cell activation and fibrotic processes. This Review summarizes and discusses the current literature on NAFLD as the liver manifestation of the systemic metabolic syndrome and focuses on the role of PPARs in the pathomechanisms as well as in the potential targeting of disease.

Therapeutic Opportunities for Intestinal Angioectasia- Targeting PPARγ and Oxidative Stress

Recurrent and acute bleeding from intestinal tract angioectasia (AEC) presents a major challenge for clinical intervention. Current treatments are empiric, with frequent poor clinical outcomes. Improvements in understanding the pathophysiology of these lesions will help guide treatment. Using data from the US Food and Drug Administration (FDA)'s Adverse Event Reporting System (FAERS), we analyzed 12 million patient reports to identify drugs inversely correlated with gastrointestinal bleeding and potentially limiting AEC severity. FAERS analysis revealed that drugs used in patients with diabetes and those targeting PPARγ-related mechanisms were associated with decreased AEC phenotypes (P < 0.0001). Electronic health records (EHRs) at University of Cincinnati Hospital were analyzed to validate FAERS analysis. EHR data showed a 5.6% decrease in risk of AEC and associated phenotypes in patients on PPARγ agonists. Murine knockout models of AEC phenotypes were used to construct a gene-regulatory network of candidate drug targets and pathways, which revealed that wound healing, vasculature development and regulation of oxidative stress were impacted in AEC pathophysiology. Human colonic tissue was examined for expression differences across key pathway proteins, PPARγ, HIF1α, VEGF, and TGFβ1. In vitro analysis of human AEC tissues showed lower expression of PPARγ and TGFβ1 compared with controls (0.55 ± 0.07 and 0.49 ± 0.05). National Center for Biotechnology Information (NCBI) Gene Expression Omnibus (GEO) RNA-Seq data was analyzed to substantiate human tissue findings. This integrative discovery approach showing altered expression of key genes involved in oxidative stress and injury repair mechanisms presents novel insight into AEC etiology, which will improve targeted mechanistic studies and more optimal medical therapy for AEC.

Dysregulated lipid metabolism links NAFLD to cardiovascular disease

Background

Non-alcoholic fatty liver disease (NAFLD) is rapidly becoming a global health problem. Cardiovascular diseases (CVD) are the most common cause of mortality in NAFLD patients. NAFLD and CVD share several common risk factors including obesity, insulin resistance, and type 2 diabetes (T2D). Atherogenic dyslipidemia, characterized by plasma hypertriglyceridemia, increased small dense low-density lipoprotein (LDL) particles, and decreased high-density lipoprotein cholesterol (HDL-C) levels, is often observed in NAFLD patients.

Scope of review

In this review, we highlight recent epidemiological studies evaluating the link between NAFLD and CVD risk. We further focus on recent mechanistic insights into the links between NAFLD and altered lipoprotein metabolism. We also discuss current therapeutic strategies for NAFLD and their potential impact on NAFLD-associated CVD risk.

Major conclusions

Alterations in hepatic lipid and lipoprotein metabolism are major contributing factors to the increased CVD risk in NAFLD patients, and many promising NASH therapies in development also improve dyslipidemia in clinical trials.

Role of peroxisome proliferator-activated receptors in stroke prevention and therapy-The best is yet to come?

Role of peroxisome proliferator-activated receptors (PPARs) in the pathophysiology of stroke and protective effects of PPAR ligands have been widely investigated in the last 20 years. Activation of all three PPAR isoforms, but especially PPAR-γ, was documented to limit postischemic injury in the numerous in vivo, as well as in in vitro studies. PPARs have been demonstrated to act on multiple mechanisms and were shown to activate multiple protective pathways related to inflammation, apoptosis, BBB protection, neurogenesis, and oxidative stress. The aim of this review was to summarize two decades of PPAR research in stroke with emphasis on in vivo animal studies. We focus on each PPAR receptor separately and detail their implication in stroke. This review also discusses recent clinical efforts in the field and the epidemiological data with regard to role of PPAR polymorphisms in susceptibility to stroke, and tries to draw conclusions and describe future perspectives.

PPARγ Deacetylation Confers the Antiatherogenic Effect and Improves Endothelial Function in Diabetes Treatment

Cardiovascular disease (CVD) is the leading cause of death in patients with diabetes, and tight glycemic control fails to reduce the risk of developing CVD. Thiazolidinediones (TZDs), a class of peroxisome proliferator-activated receptor γ (PPARγ) agonists, are potent insulin sensitizers with antiatherogenic properties, but their clinical use is limited by side effects. PPARγ deacetylation on two lysine residues (K268 and K293) induces brown remodeling of white adipose tissue and uncouples the adverse effects of TZDs from insulin sensitization. Here we show that PPARγ deacetylation confers antiatherogenic properties and retains the insulin-sensitizing effects of TZD while circumventing its detriments. We generated mice homozygous with mice with deacetylation-mimetic PPARγ mutations K268R/K293R (2KR) on an LDL-receptor knockout (Ldlr ^-/- ) background. 2KR:Ldlr ^-/- mice showed smaller atherosclerotic lesion areas than Ldlr ^-/- mice, particularly in aortic arches. With rosiglitazone treatment, 2KR:Ldlr ^-/- mice demonstrated a residual antiatherogenic response and substantial protection against bone loss and fluid retention. The antiatherosclerotic effect of 2KR was attributed to the protection of endothelium, indicated by improved endothelium-dependent vasorelaxation and repressed expression of proatherogenic factors including inducible nitric oxide synthase, interleukin-6, and NADPH oxidase 2. Therefore, manipulating PPARγ acetylation is a promising therapeutic strategy to control risk of CVD in diabetes treatment.

The impact of single and combined PPAR-α and PPAR-γ activation on the neurological outcomes following cerebral ischemia reperfusion

AIM

The neuronal damage and accompanied functional deficits induced by cerebral ischemia are among the most common causes of disabilities in adults. Activation of subtypes of peroxisome proliferator-activated receptors (PPARs); PPAR-α and PPAR-γ have shown neuroprotective effects in different neurodegenerative diseases including stroke. Thus, this study aimed to compare the effects of two different agonists: PPAR-α (fenofibrate) and PPAR-γ (pioglitazone) as well as the effect of their combination in ameliorating post-ischemia behavioral deficits.

METHODS

Male Wistar rats were either pretreated with vehicle, fenofibrate (100 mg/kg/day p.o), pioglitazone (10 mg/kg/day p.o) or their combination for 14 days prior to bilateral common carotid artery occlusion followed by reperfusion for 24 hoursh. The sensory motor functions of rats were assessed, then rats were sacrificed to determine infarct volume and histopathological changes as well as oxidative stress, inflammatory and apoptotic markers in the brain tissue.

KEY FINDINGS

Pre-treatment with fenofibrate and pioglitazone in addition to their combination improved neurobehavioral dysfunction, reduced cerebral infarct volume, attenuated inflammatory and apoptotic markers and ameliorated histopathological changes in I/R injured rats. The effect of pioglitazone in cerebral cortex was higher than its corresponding effect in fenofibrate while the combined administration of both drugs had additive neuroprotective effect and normalized inflammatory and apoptotic mediators in ischemic rats.

SIGNIFICANCE

The study compared the neuroprotective effects of PPAR-α and PPAR-γ agonists, and tested the impact of their combination. We concluded that no additional benefits on the functional outcomes might be gained upon their combination.

To Probe Full and Partial Activation of Human Peroxisome Proliferator-Activated Receptors by Pan-Agonist Chiglitazar Using Molecular Dynamics Simulations

Chiglitazar is a promising new-generation insulin sensitizer with low reverse effects for the treatment of type II diabetes mellitus (T2DM) and has shown activity as a nonselective pan-agonist to the human peroxisome proliferator-activated receptors (PPARs) (i.e., full activation of PPARγ and a partial activation of PPARα and PPARβ/δ). Yet, it has no high-resolution complex structure with PPARs and its detailed interactions and activation mechanism remain unclear. In this study, we docked chiglitazar into three experimentally resolved crystal structures of hPPAR subtypes, PPARα, PPARβ/δ, and PPARγ, followed by 3 μs molecular dynamics simulations for each system. Our MM-GBSA binding energy calculation revealed that chiglitazar most favorably bound to hPPARγ (-144.6 kcal/mol), followed by hPPARα (-138.0 kcal/mol) and hPPARβ (-135.9 kcal/mol), and the order is consistent with the experimental data. Through the decomposition of the MM-GBSA binding energy by residue and the use of two-dimensional interaction diagrams, key residues involved in the binding of chiglitazar were identified and characterized for each complex system. Additionally, our detailed dynamics analyses support that the conformation and dynamics of helix 12 play a critical role in determining the activities of the different types of ligands (e.g., full agonist vs. partial agonist). Rather than being bent fully in the direction of the agonist versus antagonist conformation, a partial agonist can adopt a more linear conformation and have a lower degree of flexibility. Our finding may aid in further development of this new generation of medication.

Macrophage NCOR1 protects from atherosclerosis by repressing a pro-atherogenic PPARγ signature

AIMS

Nuclear receptors and their cofactors regulate key pathophysiological processes in atherosclerosis development. The transcriptional activity of these nuclear receptors is controlled by the nuclear receptor corepressors (NCOR), scaffolding proteins that form the basis of large corepressor complexes. Studies with primary macrophages demonstrated that the deletion of Ncor1 increases the expression of atherosclerotic molecules. However, the role of nuclear receptor corepressors in atherogenesis is unknown.

METHODS AND RESULTS

We generated myeloid cell-specific Ncor1 knockout mice and crossbred them with low-density lipoprotein receptor (Ldlr) knockouts to study the role of macrophage NCOR1 in atherosclerosis. We demonstrate that myeloid cell-specific deletion of nuclear receptor corepressor 1 (NCOR1) aggravates atherosclerosis development in mice. Macrophage Ncor1-deficiency leads to increased foam cell formation, enhanced expression of pro-inflammatory cytokines, and atherosclerotic lesions characterized by larger necrotic cores and thinner fibrous caps. The immunometabolic effects of NCOR1 are mediated via suppression of peroxisome proliferator-activated receptor gamma (PPARγ) target genes in mouse and human macrophages, which lead to an enhanced expression of the CD36 scavenger receptor and subsequent increase in oxidized low-density lipoprotein uptake in the absence of NCOR1. Interestingly, in human atherosclerotic plaques, the expression of NCOR1 is reduced whereas the PPARγ signature is increased, and this signature is more pronounced in ruptured compared with non-ruptured carotid plaques.

CONCLUSIONS

Our findings show that macrophage NCOR1 blocks the pro-atherogenic functions of PPARγ in atherosclerosis and suggest that stabilizing the NCOR1-PPARγ binding could be a promising strategy to block the pro-atherogenic functions of plaque macrophages and lesion progression in atherosclerotic patients.

Renal cyst growth is attenuated by a combination treatment of tolvaptan and pioglitazone, while pioglitazone treatment alone is not effective

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is one of the most common monogenic disorders, characterized by the progressive formation of fluid-filled cysts. Tolvaptan is an approved drug for ADPKD patients, but is also associated with multiple side effects. The peroxisome proliferator-activator receptor gamma (PPARγ) agonist pioglitazone slows disease progression in the PCK rat model for PKD. Here, we tested whether a combination treatment of relevant doses of tolvaptan and pioglitazone leads to improved efficacy in an adult-onset PKD mouse model. Tolvaptan indeed slowed PKD progression, but the combination treatment was not more effective than tolvaptan alone. In addition, although pioglitazone raised plasma levels of its surrogate drug marker adiponectin, the drug unexpectedly failed to slow PKD progression. The pioglitazone target PPARγ was expressed at surprisingly low levels in mouse, rat and human kidneys. Other pioglitazone targets were more abundantly expressed, but this pattern was comparable across various species. The data suggest that several potential pharmacokinetic and pharmacodynamic (PK/PD) differences between different species may underlie whether or not pioglitazone is able to slow PKD progression. The ongoing phase II clinical trial with low-dose pioglitazone treatment (NCT02697617) will show whether pioglitazone is a suitable drug candidate for ADPKD treatment.

Insulin Resistance and Atherosclerosis: Implications for Insulin-Sensitizing Agents

Patients with type 2 diabetes mellitus (T2DM) are at high risk for macrovascular complications, which represent the major cause of mortality. Despite effective treatment of established cardiovascular (CV) risk factors (dyslipidemia, hypertension, procoagulant state), there remains a significant amount of unexplained CV risk. Insulin resistance is associated with a cluster of cardiometabolic risk factors known collectively as the insulin resistance (metabolic) syndrome (IRS). Considerable evidence, reviewed herein, suggests that insulin resistance and the IRS contribute to this unexplained CV risk in patients with T2DM. Accordingly, CV outcome trials with pioglitazone have demonstrated that this insulin-sensitizing thiazolidinedione reduces CV events in high-risk patients with T2DM. In this review the roles of insulin resistance and the IRS in the development of atherosclerotic CV disease and the impact of the insulin-sensitizing agents and of other antihyperglycemic medications on CV outcomes are discussed.

Thiazolidinediones: the Forgotten Diabetes Medications

PURPOSE OF REVIEW

Thiazolidinediones (TZDs) are the only pharmacologic agents that specifically treat insulin resistance. The beneficial effects of TZDs on the cardiovascular risk factors associated with insulin resistance have been well documented. TZD use has been limited because of concern about safety issues and side effects.

RECENT FINDINGS

Recent studies indicate that cardiovascular toxicity with rosiglitazone and increase in bladder cancer with pioglitazone are no longer significant issues. There are new data which show that pioglitazone treatment reduces myocardial infarctions and ischemic strokes. New data concerning TZD-mediated edema, congestive heart failure, and bone fractures improves the clinician's ability to select patients that will have minimal significant side effects. Thiazolidinediones are now generic and less costly than pharmaceutical company-promoted therapies. Better understanding of the side effects coupled with clear benefits on the components of the insulin resistance syndrome should promote TZD use in treating patients with type 2 diabetes.

Pioglitazone Reduces β Amyloid Levels via Inhibition of PPARγ Phosphorylation in a Neuronal Model of Alzheimer's Disease

It has been demonstrated that peroxisome proliferator-activated receptor γ (PPARγ) can regulate the transcription of its target gene, insulin-degrading enzyme (IDE), and thus enhance the expression of the IDE protein. The protein can degrade β amyloid (Aβ), a core pathological product of Alzheimer’s disease (AD). PPARγ can also regulate the transcription of other target gene, β-amyloid cleavage enzyme 1 (BACE1), and thus inhibit the expression of the BACE1 protein. BACE1 can hydrolyze amyloid precursor protein (APP), the precursor of Aβ. In adipose tissue, PPARγ agonists can inhibit the phosphorylation of PPARγ by inhibiting cyclin-dependent kinase 5 (CDK5), which in turn affects the expression of target genes regulated by PPARγ. PPARγ agonists may also exert inhibitory effects on the phosphorylation of PPARγ in the brain, thereby affecting the expression of the aforementioned PPARγ target genes and reducing Aβ levels. The present study confirmed this hypothesis by showing that PPARγ agonist pioglitazone attenuated the neuronal apoptosis of primary rat hippocampal neurons induced by Aβ_1–42, downregulated CDK5 expression, weakened the binding of CDK5 to PPARγ, reduced PPARγ phosphorylation, increased the expression of PPARγ and IDE, decreased the expression of BACE1, reduced APP production, and downregulated intraneuronal Aβ_1–42 levels. These effects were inhibited by the PPARγ antagonist GW9662. After CDK5 silencing with CDK5 shRNA, the above effect of pioglitazone was not observed, except when upregulating the expression of PPARγ in Aβ_1–42 treated neurons. In conclusion, this study demonstrated that pioglitazone could inhibit the phosphorylation of PPARγ in vitro by inhibiting CDK5 expression, which in turn affected the expression of PPARγ target genes Ide and Bace1, thereby promoting Aβ degradation and reducing Aβ production. This reduced Aβ levels in the brain, thereby exerting neuroprotective effects in an AD model.

Pioglitazone Improves Mitochondrial Organization and Bioenergetics in Down Syndrome Cells

Mitochondrial dysfunction plays a primary role in neurodevelopmental anomalies and neurodegeneration of Down syndrome (DS) subjects. For this reason, targeting mitochondrial key genes, such as PGC-1α/PPARGC1A, is emerging as a good therapeutic approach to attenuate cognitive disability in DS. After demonstrating the efficacy of the biguanide metformin (a PGC-1α activator) in a cell model of DS, we extended the study to other molecules that regulate the PGC-1α pathway acting on PPAR genes. We, therefore, treated trisomic fetal fibroblasts with different doses of pioglitazone (PGZ) and evaluated the effects on mitochondrial dynamics and function. Treatment with PGZ significantly increased mRNA and protein levels of PGC-1α. Mitochondrial network was fully restored by PGZ administration affecting the fission-fusion mitochondrial machinery. Specifically, optic atrophy 1 (OPA1) and mitofusin 1 (MFN1) were upregulated while dynamin-related protein 1 (DRP1) was downregulated. These effects, together with a significant increase of basal ATP content and oxygen consumption rate, and a significant decrease of reactive oxygen species (ROS) production, provide strong evidence of an overall improvement of mitochondria bioenergetics in trisomic cells. In conclusion, we demonstrate that PGZ is able to improve mitochondrial phenotype even at low concentrations (0.5 μM). We also speculate that a combination of drugs that target mitochondrial function might be advantageous, offering potentially higher efficacy and lower individual drug dosage.

Mitochondrial Genetic Disorders: Cell Signaling and Pharmacological Therapies

Mitochondrial fatty acid oxidation (FAO) and respiratory chain (RC) defects form a large group of inherited monogenic disorders sharing many common clinical and pathophysiological features, including disruption of mitochondrial bioenergetics, but also, for example, oxidative stress and accumulation of noxious metabolites. Interestingly, several transcription factors or co-activators exert transcriptional control on both FAO and RC genes, and can be activated by small molecules, opening to possibly common therapeutic approaches for FAO and RC deficiencies. Here, we review recent data on the potential of various drugs or small molecules targeting pivotal metabolic regulators: peroxisome proliferator activated receptors (PPARs), sirtuin 1 (SIRT1), AMP-activated protein kinase (AMPK), and protein kinase A (PKA)) or interacting with reactive oxygen species (ROS) signaling, to alleviate or to correct inborn FAO or RC deficiencies in cellular or animal models. The possible molecular mechanisms involved, in particular the contribution of mitochondrial biogenesis, are discussed. Applications of these pharmacological approaches as a function of genotype/phenotype are also addressed, which clearly orient toward personalized therapy. Finally, we propose that beyond the identification of individual candidate drugs/molecules, future pharmacological approaches should consider their combination, which could produce additive or synergistic effects that may further enhance their therapeutic potential.

PPARγ activation serves as therapeutic strategy against bladder cancer via inhibiting PI3K-Akt signaling pathway

Background

Heterogeneity in bladder cancer results in variable clinical outcomes, posing challenges for clinical management of this malignancy. Recent studies suggest both tumor suppressive and oncogenic role of PPARγ in bladder cancer. The fuction of PPARγ signaling pathway in modulating carcinogenesis is controversial.

Methods

The expression of PPARγ and association with overall survival were analyzed in patients from two cohorts. The effect of PPARγ activation on cell proliferation, cell cycle, and cell apoptosis were determined with the agonists (rosiglitazone and pioglitazone), the inverse agonist (T0070907), and the antagonist (GW9662) in Umuc-3 and 5637 bladder cancer cells. The correlation of PPARγ activation with PI3K-Akt pathway was evaluated with RNA sequencing data from the TCGA cases and 30 human bladder cancer cell lines. The effect of PPARγ activation on tumor growth was validated with subcutaneous tumor models in vivo. The effect of PPARγ activation on PI3K-Akt signaling transduction was determined with multiple assays including immunohistochemistry, flow cytometry, proteomic array, and western blotting.

Results

We showed that PPARγ was a favorable prognostic factor in patients with bladder cancer. PPARγ activation by rosiglitazone and pioglitazone markedly induced cell cycle G2 arrest and apoptosis in bladder cancer cells, which resulted in inhibition of cell proliferation in vitro and suppression of tumor growth in vivo. The underlying mechanism involved marked inhibition of PI3K-Akt pathway.

Conclusions

This study reported the tumor-suppressive effect of PPARγ agonists in bladder cancer, suggesting that transactivation of PPARγ could be served as a potential strategy for the chemoprevention and therapeutic treatment of bladder cancer.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5426-6) contains supplementary material, which is available to authorized users.

The Pioglitazone Trek via Human PPAR Gamma: From Discovery to a Medicine at the FDA and Beyond

For almost two decades, pioglitazone has been prescribed primarily to prevent and treat insulin resistance in some type 2 diabetic patients. In this review, we trace the path to discovery of pioglitazone as a thiazolidinedione compound, the glitazone tracks through the regulatory agencies, the trek to molecular agonism in the nucleus and the binding of pioglitazone to the nuclear receptor PPAR gamma. Given the rise in consumption of pioglitazone in T2D patients worldwide and the increased number of clinical trials currently testing alternate medical uses for this drug, there is also merit to some reflection on the reported adverse effects. Going forward, it is imperative to continue investigations into the mechanisms of actions of pioglitazone, the potential of glitazone drugs to contribute to unmet needs in complex diseases associated with the dynamics of adaptive homeostasis, and also the routes to minimizing adverse effects in every-day patients throughout the world.