Idebenone and coenzyme Q10 are novel PPARα/γ ligands, with potential for treatment of fatty liver diseases

A novel fatty acid mimetic with pan-PPAR partial agonist activity inhibits diet-induced obesity and metabolic dysfunction-associated steatotic liver disease

OBJECTIVE

The prevalence of metabolic diseases is increasing globally at an alarming rate; thus, it is essential that effective, accessible, low-cost therapeutics are developed. Peroxisome proliferator-activated receptors (PPARs) are transcription factors that tightly regulate glucose homeostasis and lipid metabolism and are important drug targets for the treatment of type 2 diabetes and dyslipidemia. We previously identified LDT409, a fatty acid-like compound derived from cashew nut shell liquid, as a novel pan-active PPARα/γ/δ compound. Herein, we aimed to assess the efficacy of LDT409 in vivo and investigate the molecular mechanisms governing the actions of the fatty acid mimetic LDT409 in diet-induced obese mice.

METHODS

C57Bl/6 mice (6-11-month-old) were fed a chow or high fat diet (HFD) for 4 weeks; mice thereafter received once daily intraperitoneal injections of vehicle, 10 mg/kg Rosiglitazone, 40 mg/kg WY14643, or 40 mg/kg LDT409 for 18 days while continuing the HFD. During treatments, body weight, food intake, glucose and insulin tolerance, energy expenditure, and intestinal lipid absorption were measured. On day 18 of treatment, tissues and plasma were collected for histological, molecular, and biochemical analysis.

RESULTS

We found that treatment with LDT409 was effective at reversing HFD-induced obesity and associated metabolic abnormalities in mice. LDT409 lowered food intake and hyperlipidemia, while improving insulin tolerance. Despite being a substrate of both PPARα and PPARγ, LDT409 was crucial for promoting hepatic fatty acid oxidation and reducing hepatic steatosis in HFD-fed mice. We also highlighted a role for LDT409 in white and brown adipocytes in vitro and in vivo where it decreased fat accumulation, increased lipolysis, induced browning of WAT, and upregulated thermogenic gene Ucp1. Remarkably, LDT409 reversed HFD-induced weight gain back to chow-fed control levels. We determined that the LDT409-induced weight-loss was associated with a combination of increased energy expenditure (detectable before weight loss was apparent), decreased food intake, increased systemic fat utilization, and increased fecal lipid excretion in HFD-fed mice.

CONCLUSIONS

Collectively, LDT409 represents a fatty acid mimetic that generates a uniquely favorable metabolic response for the treatment of multiple abnormalities including obesity, dyslipidemia, metabolic dysfunction-associated steatotic liver disease, and diabetes. LDT409 is derived from a highly abundant natural product-based starting material and its development could be pursued as a therapeutic solution to the global metabolic health crisis.

Mitochondrial dysfunction: A promising therapeutic target for liver diseases

The liver is an important metabolic and detoxification organ and hence demands a large amount of energy, which is mainly produced by the mitochondria. Liver tissues of patients with alcohol-related or non-alcohol-related liver diseases contain ultrastructural mitochondrial lesions, mitochondrial DNA damage, disturbed mitochondrial dynamics, and compromised ATP production. Overproduction of mitochondrial reactive oxygen species induces oxidative damage to mitochondrial proteins and mitochondrial DNA, decreases mitochondrial membrane potential, triggers hepatocyte inflammation, and promotes programmed cell death, all of which impair liver function. Mitochondrial DNA may be a potential novel non-invasive biomarker of the risk of progression to liver cirrhosis and hepatocellular carcinoma in patients infected with the hepatitis B virus. We herein present a review of the mechanisms of mitochondrial dysfunction in the development of acute liver injury and chronic liver diseases, such as hepatocellular carcinoma, viral hepatitis, drug-induced liver injury, alcoholic liver disease, and non-alcoholic fatty liver disease. This review also discusses mitochondrion-centric therapies for treating liver diseases.

Mitochondrial Dysfunction in Metabolic Dysfunction Fatty Liver Disease (MAFLD)

Nonalcoholic fatty liver disease (NAFLD) has become an increasingly common disease in Western countries and has become the major cause of liver cirrhosis or hepatocellular carcinoma (HCC) in addition to viral hepatitis in recent decades. Furthermore, studies have shown that NAFLD is inextricably linked to the development of extrahepatic diseases. However, there is currently no effective treatment to cure NAFLD. In addition, in 2020, NAFLD was renamed metabolic dysfunction fatty liver disease (MAFLD) to show that its pathogenesis is closely related to metabolic disorders. Recent studies have reported that the development of MAFLD is inextricably associated with mitochondrial dysfunction in hepatocytes and hepatic stellate cells (HSCs). Simultaneously, mitochondrial stress caused by structural and functional disorders stimulates the occurrence and accumulation of fat and lipo-toxicity in hepatocytes and HSCs. In addition, the interaction between mitochondrial dysfunction and the liver-gut axis has also become a new point during the development of MAFLD. In this review, we summarize the effects of several potential treatment strategies for MAFLD, including antioxidants, reagents, and intestinal microorganisms and metabolites.

Transcriptomic (DNA Microarray) and Metabolome (LC-TOF-MS) Analyses of the Liver in High-Fat Diet Mice after Intranasal Administration of GALP (Galanin-like Peptide)

The aim of this research was to test the efficacy and potential clinical application of intranasal administration of galanin-like peptide (GALP) as an anti-obesity treatment under the hypothesis that GALP prevents obesity in mice fed a high-fat diet (HFD). Focusing on the mechanism of regulation of lipid metabolism in peripheral tissues via the autonomic nervous system, we confirmed that, compared with a control (saline), intranasally administered GALP prevented further body weight gain in diet-induced obesity (DIO) mice with continued access to an HFD. Using an omics-based approach, we identified several genes and metabolites in the liver tissue of DIO mice that were altered by the administration of intranasal GALP. We used whole-genome DNA microarray and metabolomics analyses to determine the anti-obesity effects of intranasal GALP in DIO mice fed an HFD. Transcriptomic profiling revealed the upregulation of flavin-containing dimethylaniline monooxygenase 3 (Fmo3), metallothionein 1 and 2 (Mt1 and Mt2, respectively), and the Aldh1a3, Defa3, and Defa20 genes. Analysis using the DAVID tool showed that intranasal GALP enhanced gene expression related to fatty acid elongation and unsaturated fatty acid synthesis and downregulated gene expression related to lipid and cholesterol synthesis, fat absorption, bile uptake, and excretion. Metabolite analysis revealed increased levels of coenzyme Q10 and oleoylethanolamide in the liver tissue, increased levels of deoxycholic acid (DCA) and taurocholic acid (TCA) in the bile acids, increased levels of taurochenodeoxycholic acid (TCDCA), and decreased levels of ursodeoxycholic acid (UDCA). In conclusion, intranasal GALP administration alleviated weight gain in obese mice fed an HFD via mechanisms involving antioxidant, anti-inflammatory, and fatty acid metabolism effects and genetic alterations. The gene expression data are publicly available at NCBI GSE243376.

Combining idebenone and rosuvastatin prevents atherosclerosis by suppressing oxidative stress and NLRP3 inflammasome activation

Atherosclerosis is a progressive inflammatory disease activated by excessive oxidized low-density lipoprotein (ox-LDL). Statins are the first-line choice to reduce the risk of cardiovascular disease. However, statin-associated side effects prompt dose reduction or discontinuation. Idebenone could protect against atherosclerosis by scavenging reactive oxygen species (ROS). Although both idebenone and statins have certain efficacy, neither of them can achieve a completely satisfactory effect. Here, we aim to investigate the anti-atherosclerotic effect of the combination of idebenone and statins. Apolipoprotein E knockout (ApoE-/-) mice were given idebenone (400 mg/kg/d), rosuvastatin (10 mg/kg/d) or a combination of idebenone and rosuvastatin. Histological and immunohistochemical staining were used to analyze the size and composition of the plaque. In vivo and in vitro experiments were conducted to explore the possible mechanism. Idebenone and rosuvastatin both reduced plaque burden and increased the stability of atherosclerotic plaques in the ApoE-/- mice. Mice receiving the combination therapy had even reduced and more stable atherosclerotic plaques than mice treated with idebenone or rosuvastatin alone. NLRP3 and IL-1β were further downregulated in mice receiving combination therapy compared with mice treated with monotherapy. The combination treatment also markedly reduced oxidative stress and cell apoptosis in vivo and in vitro. In conclusion, our data demonstrate that the combination of idebenone and rosuvastatin works synergistically to inhibit atherosclerosis, and that the use of both substances together is more effective than using either substance alone. From a therapeutic point, combining idebenone and rosuvastatin appears to be a promising strategy to further prevent atherosclerosis.

Coenzyme Q10 Stimulate Reproductive Vatality

Female infertility and pregnancy maintenance are associate with various factors, including quantity and quality of oocytes, genital inflammation, endometriosis, and other diseases. Women are even diagnosed as unexplained infertility or unexplained recurrent spontaneous abortion when failed to achieve pregnancy with current treatment, which are urgent clinical issues need to be addressed. Coenzyme Q10 (CoQ10) is a lipid-soluble electron carrier in the mitochondrial electron transport chain. It is not only essential for the mitochondria to produce energy, but also function as an antioxidant to maintain redox homeostasis in the body. Recently, the capacity of CoQ10 to reduce oxidative stress (OS), enhance mitochondrial activity, regulate gene expression and inhibit inflammatory responses, has been discovered as a novel adjuvant in male reproductive performance enhancing in both animal and human studies. Furthermore, CoQ10 is also proved to regulate immune balance, antioxidant, promote glucose and lipid metabolism. These properties will bring highlight for ovarian dysfunction reversing, ovulation ameliorating, oocyte maturation/fertilization promoting, and embryonic development optimizing. In this review, we systematically discuss the pleiotropic effects of CoQ10 in female reproductive disorders to investigate the mechanism and therapeutic potential to provide a reference in subsequent studies.

Alleviating effects of coenzyme Q10 supplements on biomarkers of inflammation and oxidative stress: results from an umbrella meta-analysis

Introduction: Although several meta-analyses support the positive effect of coenzyme Q10 (CoQ10) on biomarkers of oxidative stress and inflammation, the results of some other studies reject such effects. Methods: Therefore, in this umbrella meta-analysis, we performed a comprehensive systematic search in such databases as Web of Science, PubMed, Scopus, Embase, and Google Scholar up to January 2023. Results: Based on standardized mean difference analysis, CoQ10 supplementation significantly decreased serum C-reactive protein (CRP) (ESSMD = -0.39; 95% CI: 0.77, -0.01, p = 0.042) and malondialdehyde (MDA) (ESSMD = -1.17; 95% CI: 1.55, -0.79, p < 0.001), while it increased the total antioxidant capacity (TAC) (ESSMD = 1.21; 95% CI: 0.61, 1.81, p < 0.001) and serum superoxide dismutase (SOD) activity (ESSMD = 1.08; 95% CI: 0.37, 1.79, p = 0.003). However, CoQ10 supplementation had no significant reducing effect on tumor-necrosis factor-alpha (TNF- α) (ESSMD = -0.70; 95% CI: 2.09, 0.68, p = 0.320) and interleukin-6 (IL-6) levels (ESSMD = -0.85; 95% CI: 1.71, 0.01, p = 0.053). Based on weighted mean difference analysis, CoQ10 supplementation considerably decreased TNF-α (ESWMD = -0.46, 95% CI: 0.65, -0.27; p < 0.001), IL-6 (ESWMD = -0.92, 95% CI: 1.40, -0.45; p < 0.001), and CRP levels (effect sizes WMD = -0.28, 95% CI: 0.47, -0.09; p < 0.001). Discussion: The results of our meta-analysis supported the alleviating effects of CoQ10 on markers of inflammation cautiously. However, CoQ10 had antioxidant effects regarding the improvement of all the studied antioxidant and oxidative stress biomarkers. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=323861, identifier CRD42022323861.

The advancements in targets for ferroptosis in liver diseases

Ferroptosis is a type of regulated cell death caused by iron overload and lipid peroxidation, and its core is an imbalance of redox reactions. Recent studies showed that ferroptosis played a dual role in liver diseases, that was, as a therapeutic target and a pathogenic factor. Therefore, herein, we summarized the role of ferroptosis in liver diseases, reviewed the part of available targets, such as drugs, small molecules, and nanomaterials, that acted on ferroptosis in liver diseases, and discussed the current challenges and prospects.

Nutraceutical approaches to non-alcoholic fatty liver disease (NAFLD): A position paper from the International Lipid Expert Panel (ILEP)

Non-Alcoholic Fatty Liver Disease (NAFLD) is a common condition affecting around 10-25% of the general adult population, 15% of children, and even > 50% of individuals who have type 2 diabetes mellitus. It is a major cause of liver-related morbidity, and cardiovascular (CV) mortality is a common cause of death. In addition to being the initial step of irreversible alterations of the liver parenchyma causing cirrhosis, about 1/6 of those who develop NASH are at risk also developing CV disease (CVD). More recently the acronym MAFLD (Metabolic Associated Fatty Liver Disease) has been preferred by many European and US specialists, providing a clearer message on the metabolic etiology of the disease. The suggestions for the management of NAFLD are like those recommended by guidelines for CVD prevention. In this context, the general approach is to prescribe physical activity and dietary changes the effect weight loss. Lifestyle change in the NAFLD patient has been supplemented in some by the use of nutraceuticals, but the evidence based for these remains uncertain. The aim of this Position Paper was to summarize the clinical evidence relating to the effect of nutraceuticals on NAFLD-related parameters. Our reading of the data is that whilst many nutraceuticals have been studied in relation to NAFLD, none have sufficient evidence to recommend their routine use; robust trials are required to appropriately address efficacy and safety.

CoQ Regulates Brown Adipose Tissue Respiration and Uncoupling Protein 1 Expression

Coenzyme Q (CoQ, aka ubiquinone) is a key component of the mitochondrial electron transport chain (ETC) and membrane-incorporated antioxidant. CoQ10 deficiencies encompass a heterogeneous spectrum of clinical phenotypes and can be caused by hereditary mutations in the biosynthesis pathway or result from pharmacological interventions such as HMG-CoA Reductase inhibitors, and statins, which are widely used to treat hypercholesterolemia and prevent cardiovascular disease. How CoQ deficiency affects individual tissues and cell types, particularly mitochondrial-rich ones such as brown adipose tissue (BAT), has remained poorly understood. Here we show that pharmacological and genetic models of BAT CoQ deficiency show altered respiration that can only in part be explained by classical roles of CoQ in the respiration chain. Instead, we found that CoQ strongly impacts brown and beige adipocyte respiration via the regulation of uncoupling protein 1 (UCP1) expression. CoQ deficiency in BAT robustly decreases UCP1 protein levels and uncoupled respiration unexpectedly, resulting in increased inner mitochondrial membrane potential and decreased ADP/ATP ratios. Suppressed UCP1 expression was also observed in a BAT-specific in vivo model of CoQ deficiency and resulted in enhanced cold sensitivity. These findings demonstrate an as yet unappreciated role of CoQ in the transcriptional regulation of key thermogenic genes and functions.

Systematic Understanding of Anti-Aging Effect of Coenzyme Q10 on Oocyte Through a Network Pharmacology Approach

BACKGROUND

Maternal oocyte aging is strongly contributing to age-related decline in female fertility. Coenzyme Q10 (CoQ10) exerts positive effects in improving aging-related deterioration of oocyte quality, but the exact mechanism is unclear.

OBJECTIVE

To reveal the system-level mechanism of CoQ10's anti-aging effect on oocytes based on network pharmacology.

METHODS

This study adopted a systems network pharmacology approach, including target identification, data integration, network and module construction, bioinformatics analysis, molecular docking, and molecular dynamics simulation.

RESULT

A total of 27 potential therapeutic targets were screened out. Seven hub targets (PPARA, CAT, MAPK14, SQSTM1, HMOX1, GRB2, and GSR) were identified. Functional and pathway enrichment analysis indicated that these 27 putative targets exerted therapeutic effects on oocyte aging by regulating signaling pathways (e.g., PPAR, TNF, apoptosis, necroptosisn, prolactin, and MAPK signaling pathway), and are involved oxidation-reduction process, mitochondrion, enzyme binding, reactive oxygen species metabolic process, ATP binding, among others. In addition, five densely linked functional modules revealed the potential mechanisms of CoQ10 in improving aging-related deterioration of oocyte quality are closely related to antioxidant, mitochondrial function enhancement, autophagy, anti-apoptosis, and immune and endocrine system regulation. The molecular docking study reveals that seven hub targets have a good binding affinity towards CoQ10, and molecular dynamics simulation confirms the stability of the interaction between the hub targets and the CoQ10 ligand.

CONCLUSION

This network pharmacology study revealed the multiple mechanisms involved in the anti-aging effect of CoQ10 on oocytes. The molecular docking and molecular dynamics simulation provide evidence that CoQ10 may act on these hub targets to fight against oocytes aging.

α-Lactalbumin peptide Asp-Gln-Trp alleviates hepatic insulin resistance and modulates gut microbiota dysbiosis in high-fat diet-induced NAFLD mice

α-Lactalbumin peptide Asp-Gln-Trp (DQW) alleviates hepatic insulin resistance via activating the IRS1/PI3K/AKT pathway and modulates gut microbiota dysbiosis in high-fat diet-induced NAFLD mice.

Shc inhibitor idebenone ameliorates liver injury and fibrosis in dietary NASH in mice

Shc expression rises in human nonalcoholic steatohepatitis (NASH) livers, and Shc-deficient mice are protected from NASH-thus Shc inhibition could be a novel therapeutic strategy for NASH. Idebenone was recently identified as the first small-molecule Shc inhibitor drug. We tested idebenone in the fibrotic methionine-choline deficient (MCD) diet and the metabolic fast food diet (FFD) mouse models of NASH. In the fibrotic MCD NASH model, idebenone reduced Shc expression and phosphorylation in peripheral blood mononuclear cells and Shc expression in the liver; decreased serum alanine aminotransferase and aspartate aminotransferase; and attenuated liver fibrosis as observed by quantitative polymerase chain reaction (qPCR) and hydroxyproline quantification. In the metabolic FFD model, idebenone administration improved insulin resistance, and reduced inflammation and fibrosis shown with qPCR, hydroxyproline measurement, and histology. Thus, idebenone ameliorates NASH in two mouse models. As an approved drug with a benign safety profile, Idebenone could be a reasonable human NASH therapy.

Novel Short-Chain Quinones to Treat Vision Loss in a Rat Model of Diabetic Retinopathy

Diabetic retinopathy (DR), one of the leading causes of blindness, is mainly diagnosed based on the vascular pathology of the disease. Current treatment options largely focus on this aspect with mostly insufficient therapeutic long-term efficacy. Mounting evidence implicates mitochondrial dysfunction and oxidative stress in the central etiology of DR. Consequently, drug candidates that aim at normalizing mitochondrial function could be an attractive therapeutic approach. This study compared the mitoprotective compounds, idebenone and elamipretide, side-by-side against two novel short-chain quinones (SCQs) in a rat model of DR. The model effectively mimicked type 2 diabetes over 21 weeks. During this period, visual acuity was monitored by measuring optokinetic response (OKR). Vision loss occurred 5–8 weeks after the onset of hyperglycemia. After 10 weeks of hyperglycemia, visual function was reduced by 65%. From this point, the right eyes of the animals were topically treated once daily with the test compounds. The left, untreated eye served as an internal control. Only three weeks of topical treatment significantly restored vision from 35% to 58–80%, while visual acuity of the non-treated eyes continued to deteriorate. Interestingly, the two novel SCQs restored visual acuity better than idebenone or elamipretide. This was also reflected by protection of retinal pathology against oxidative damage, retinal ganglion cell loss, reactive gliosis, vascular leakage, and retinal thinning. Overall, mitoprotective and, in particular, SCQ-based compounds have the potential to be developed into effective and fast-acting drug candidates against DR.

Nuclear Hormone Receptors and Their Ligands: Metabolites in Control of Transcription

Nuclear hormone receptors are a family of transcription factors regulated by small molecules derived from the endogenous metabolism or diet. There are forty-eight nuclear hormone receptors in the human genome, twenty of which are still orphans. In this review, we make a brief historical journey from the first observations by Berthold in 1849 to the era of orphan receptors that began with the sequencing of the Caenorhabditis elegans genome in 1998. We discuss the evolution of nuclear hormone receptors and the putative ancestral ligands as well as how the ligand universe has expanded over time. This leads us to define four classes of metabolites-fatty acids, terpenoids, porphyrins and amino acid derivatives-that generate all known ligands for nuclear hormone receptors. We conclude by discussing the ongoing efforts to identify new classes of ligands for orphan receptors.

Idebenone: When an antioxidant is not an antioxidant

Idebenone is a well described drug that was initially developed against dementia. The current literature widely portrays this molecule as a potent antioxidant and CoQ₁₀ analogue. While numerous papers seem to support this view, a closer look indicates that the pharmacokinetics of idebenone do not support these claims. A major discrepancy between achievable tissue levels, especially in target tissues such as the brain, and doses required to show the proposed effects, significantly questions our current understanding. This review explains how this has happened and highlights the discrepancies in the current literature. More importantly, based on some recent discoveries, a new framework is presented that can explain the mode of action of this molecule and can align formerly contradictory results. Finally, this new appreciation of the molecular activities of idebenone provides a rational approach to test idebenone in novel indications that might have not been considered previously for this drug.

An optimized QF-binary expression system for use in zebrafish

The zebrafish model organism has been of exceptional utility for the study of vertebrate development and disease through the application of tissue-specific labelling and overexpression of genes carrying patient-derived mutations. However, there remains a need for a binary expression system that is both non-toxic and not silenced over animal generations by DNA methylation. The Q binary expression system derived from the fungus Neurospora crassa is ideal, because the consensus binding site for the QF transcription factor lacks CpG dinucleotides, precluding silencing by CpG-meditated methylation. To optimize this system for zebrafish, we systematically tested several variants of the QF transcription factor: QF full length; QF2, which lacks the middle domain; QF2^w, which is an attenuated version of QF2; and chimeric QFGal4. We found that full length QF and QF2 were strongly toxic to zebrafish embryos, QF2^w was mildly toxic, and QFGal4 was well tolerated, when injected as RNA or expressed ubiquitously from stable transgenes. In addition, QFGal4 robustly activated a Tg(QUAS:GFP^NLS) reporter transgene. To increase the utility of this system, we also modified the QF effector sequence termed QUAS, which consists of five copies of the QF binding site. Specifically, we decreased both the CpG dinucleotide content, as well as the repetitiveness of QUAS, to reduce the risk of transgene silencing via CpG methylation. Moreover, these modifications to QUAS removed leaky QF-independent neural expression that we detected in the original QUAS sequence. To demonstrate the utility of our QF optimizations, we show how the Q-system can be used for lineage tracing using a Cre-dependent Tg(ubi:QFGal4-switch) transgene. We also demonstrate that QFGal4 can be used in transient injections to tag and label endogenous genes by knocking in QFGal4 into sox2 and ubiquitin C genes.

Comparative In Vitro Toxicology of Novel Cytoprotective Short-Chain Naphthoquinones

Short-chain quinones (SCQs) have been identified as potential drug candidates against mitochondrial dysfunction, which largely depends on the reversible redox characteristics of the active quinone core. We recently identified 11 naphthoquinone derivatives, 1–11, from a library of SCQs that demonstrated enhanced cytoprotection and improved metabolic stability compared to the clinically used benzoquinone idebenone. Since the toxicity properties of our promising SCQs were unknown, this study developed multiplex methods and generated detailed toxicity profiles from 11 endpoint measurements using the human hepatocarcinoma cell line HepG2. Overall, the toxicity profiles were largely comparable across different assays, with simple standard assays showing increased sensitivity compared to commercial toxicity assays. Within the 11 naphthoquinones tested, the L-phenylalanine derivative 4 consistently demonstrated the lowest toxicity across all assays. The results of this study not only provide useful information about the toxicity features of SCQs but will also enable the progression of the most promising drug candidates towards their clinical use.

An orally available hypoglycaemic peptide taken up by caveolae transcytosis displays improved hypoglycaemic effects and body weight control in db/db mice

BACKGROUND AND PURPOSE

Type 2 diabetes is one of the most severe chronic diseases and is an increasingly important public health problem worldwide. Several agonists of the glucagon-like peptide-1 (GLP-1) receptor have been developed to treat Type 2 diabetes but most of them are administered by injection. This mode of administration seriously reduces patient compliance and increases the risk of infection. Here, we describe the actions of a novel, orally available, GLP-1 receptor agonist - oral hypoglycaemic peptide 2 (OHP2) - derived from exendin-4 by replacing amino acids. We have also investigated its pharmacokinetic profiles, therapeutic effects and absorption mechanism.

EXPERIMENTAL APPROACH

Healthy Wistar rats were used for pharmacokinetic analyses. In diabetic db/db mice. OHP2 was given for 8 weeks to evaluate its effects on hyperglycaemia, dyslipidaemia, basal metabolism and tissue injury. Possible endocytosis and transcytosis mechanisms of OHP2 uptake were explored in Caco-2 cell monolayers.

KEY RESULTS

In rats, the absolute bioavailability of orally administered OHP2 was 20-fold greater than that of orally administered exendin-4. In db/db mice, OHP2 dose-dependently exhibits good potential in glucose-lowering and weight loss after oral administration. OHP2 also alleviated hyperlipidaemia, ameliorated energy metabolism and promoted tissue repair in diabetic mice. Furthermore, uptake of OHP2 by Caco-2 cells was dependent on caveolae-mediated transcytosis rather than endocytosis mediated by GLP-1 receptors.

CONCLUSIONS AND IMPLICATIONS

OHP2 is a potential, orally bioavailable, candidate drug for the treatment of Type 2 diabetes. Its transcytosis mechanism of uptake could help in the development of absorption enhancers of OHP2.

Coenzyme Q10: Clinical Applications in Cardiovascular Diseases

Coenzyme Q₁₀ (CoQ₁₀) is a ubiquitous factor present in cell membranes and mitochondria, both in its reduced (ubiquinol) and oxidized (ubiquinone) forms. Its levels are high in organs with high metabolism such as the heart, kidneys, and liver because it acts as an energy transfer molecule but could be reduced by aging, genetic factors, drugs (e.g., statins), cardiovascular (CV) diseases, degenerative muscle disorders, and neurodegenerative diseases. As CoQ₁₀ is endowed with significant antioxidant and anti-inflammatory features, useful to prevent free radical-induced damage and inflammatory signaling pathway activation, its depletion results in exacerbation of inflammatory processes. Therefore, exogenous CoQ₁₀ supplementation might be useful as an adjuvant in the treatment of cardiovascular diseases such as heart failure, atrial fibrillation, and myocardial infarction and in associated risk factors such as hypertension, insulin resistance, dyslipidemias, and obesity. This review aims to summarize the current evidences on the use of CoQ₁₀ supplementation as a therapeutic approach in cardiovascular diseases through the analysis of its clinical impact on patients' health and quality of life. A substantial reduction of inflammatory and oxidative stress markers has been observed in several randomized clinical trials (RCTs) focused on several of the abovementioned diseases, even if more RCTs, involving a larger number of patients, will be necessary to strengthen these interesting findings.

Endocrine regulation of multichromatic color vision

Vertebrate color vision requires spectrally selective opsin-based pigments, expressed in distinct cone photoreceptor populations. In primates and in fish, spectrally divergent opsin genes may reside in head-to-tail tandem arrays. Mechanisms underlying differential expression from such arrays have not been fully elucidated. Regulation of human red (LWS) vs. green (MWS) opsins is considered a stochastic event, whereby upstream enhancers associate randomly with promoters of the proximal or distal gene, and one of these associations becomes permanent. We demonstrate that, distinct from this stochastic model, the endocrine signal thyroid hormone (TH) regulates differential expression of the orthologous zebrafish lws1/lws2 array, and of the tandemly quadruplicated rh2-1/rh2-2/rh2-3/rh2-4 array. TH treatment caused dramatic, dose-dependent increases in abundance of lws1, the proximal member of the lws array, and reduced lws2 Fluorescent lws reporters permitted direct visualization of individual cones switching expression from lws2 to lws1 Athyroidism increased lws2 and reduced lws1, except within a small ventral domain of lws1 that was likely sustained by retinoic acid signaling. Changes in lws abundance and distribution in athyroid zebrafish were rescued by TH, demonstrating plasticity of cone phenotype in response to this signal. TH manipulations also regulated the rh2 array, with athyroidism reducing abundance of distal members. Interestingly, the opsins encoded by the proximal lws gene and distal rh2 genes are sensitive to longer wavelengths than other members of their respective arrays; therefore, endogenous TH acts upon each opsin array to shift overall spectral sensitivity toward longer wavelengths, underlying coordinated changes in visual system function during development and growth.

15-keto-prostaglandin E2 activates host peroxisome proliferator-activated receptor gamma (PPAR-γ) to promote Cryptococcus neoformans growth during infection

Cryptococcus neoformans is one of the leading causes of invasive fungal infection in humans worldwide. C. neoformans uses macrophages as a proliferative niche to increase infective burden and avoid immune surveillance. However, the specific mechanisms by which C. neoformans manipulates host immunity to promote its growth during infection remain ill-defined. Here we demonstrate that eicosanoid lipid mediators manipulated and/or produced by C. neoformans play a key role in regulating pathogenesis. C. neoformans is known to secrete several eicosanoids that are highly similar to those found in vertebrate hosts. Using eicosanoid deficient cryptococcal mutants Δplb1 and Δlac1, we demonstrate that prostaglandin E₂ is required by C. neoformans for proliferation within macrophages and in vivo during infection. Genetic and pharmacological disruption of host PGE₂ synthesis is not required for promotion of cryptococcal growth by eicosanoid production. We find that PGE₂ must be dehydrogenated into 15-keto-PGE₂ to promote fungal growth, a finding that implicated the host nuclear receptor PPAR-γ. C. neoformans infection of macrophages activates host PPAR-γ and its inhibition is sufficient to abrogate the effect of 15-keto-PGE₂ in promoting fungal growth during infection. Thus, we describe the first mechanism of reliance on pathogen-derived eicosanoids in fungal pathogenesis and the specific role of 15-keto-PGE₂ and host PPAR-γ in cryptococcosis.

Cryptococcus neoformans is an opportunistic fungal pathogen that is responsible for significant numbers of deaths in the immunocompromised population worldwide. Here we address whether eicosanoids produced by C. neoformans manipulate host innate immune cells during infection. Cryptococcus neoformans produces several eicosanoids that are notable for their similarity to vertebrate eicosanoids, it is therefore possible that fungal-derived eicosanoids may provoke physiological effects in the host. Using a combination of in vitro and in vivo infection models we identify a specific eicosanoid species—prostaglandin E2 –that is required by C. neoformans for growth during infection. We subsequently show that prostaglandin E₂ must be converted to 15-keto-prostaglandin E₂ within the host before it has these effects. Furthermore, we find that prostaglandin E₂/15-keto-prostaglandin E₂ mediated virulence is via activation of host PPAR-γ –an intracellular eicosanoid receptor known to interact with 15-keto-PGE₂.

Spotlight on zebrafish: the next wave of translational research

Five years after the launch of the Disease Models & Mechanisms (DMM) Special Issue on zebrafish as a disease model, the field has progressed significantly. Zebrafish have been used to precisely model human genetic variants, to unpick the mechanisms of metabolic and other diseases, to study infection, inflammation and cancer, and to develop and test new therapeutic approaches. In this Editorial, we highlight recent research published in DMM that uses zebrafish to develop new experimental tools and to provide new insight into disease mechanism and therapy. The broad spectrum of subjects and approaches covered in these articles underscores the versatility of zebrafish in translational research. Further, it highlights the zebrafish community's ethos of creativity and collaboration in translating basic biological research into clinically relevant advances affecting how we understand and treat human disease.

Summary: Zebrafish are a highly versatile and relevant organism for human disease modelling. This Editorial highlights the recent zebrafish research published in DMM.