Who is the real 12-HETrE?

The fatty acid omega hydroxylase genes (CYP4 family) in the progression of metabolic dysfunction-associated steatotic liver disease (MASLD): An RNA sequence database analysis and review

Fatty acid omega hydroxylase P450s consist of enzymes that hydroxylate various chain-length saturated and unsaturated fatty acids (FAs) and bioactive eicosanoid lipids. The human cytochrome P450 gene 4 family (CYP4) consists of 12 members that are associated with several human diseases. However, their role in the progression of metabolic dysfunction-associated fatty liver disease (MASLD) remains largely unknown. It has long been thought that the induction of CYP4 family P450 during fasting and starvation prevents FA-related lipotoxicity through FA metabolism to dicarboxylic acids that are chain-shortened in peroxisomes and then transported to the mitochondria for complete oxidation. Several studies have revealed that peroxisome succinate transported to the mitochondria is used for gluconeogenesis during fasting and starvation, and recent evidence suggests that peroxisome acetate can be utilized for lipogenesis and lipid droplet formation as well as epigenetic modification of gene transcription. In addition, omega hydroxylation of the bioactive eicosanoid arachidonic acid to 20-Hydroxyeicosatetraenoic acid (20-HETE) is essential for activating the GPR75 receptor, leading to vasoconstriction and cell proliferation. Several mouse models of diet-induced MASLD have revealed the induction of selective CYP4A members and the suppression of CYP4F during steatosis and steatohepatitis, suggesting a critical metabolic role in the progression of fatty liver disease. Thus, to further investigate the functional roles of CYP4 genes, we analyzed the differential gene expression of 12 members of CYP4 gene family in datasets from the Gene Expression Omnibus (GEO) from patients with steatosis, steatohepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma. We also observed the differential expression of various CYP4 genes in the progression of MASLD, indicating that different CYP4 members may have unique functional roles in the metabolism of specific FAs and eicosanoids at various stages of fatty liver disease. These results suggest that targeting selective members of the CYP4A family is a viable therapeutic approach for treating and managing MASLD.

Eicosanoids and Oxylipin Signature in Hereditary Hemochromatosis Patients Are Similar to Dysmetabolic Iron Overload Syndrome Patients but Are Impacted by Dietary Iron Absorption

INTRODUCTION

Oxylipins are mediators of oxidative stress. To characterize the underlying inflammatory processes and phenotype effect of iron metabolism disorders, we investigated the oxylipin profile in hereditary hemochromatosis (HH) and dysmetabolic iron overload syndrome (DIOS) patients.

METHODS

An LC-MS/MS-based method was performed to quantify plasma oxylipins in 20 HH and 20 DIOS patients in fasting conditions and 3 h after an iron-rich meal in HH patients.

RESULTS

Principal component analysis showed no separation between HH and DIOS, suggesting that the clinical phenotype has no direct impact on oxylipin metabolism. 20-HETE was higher in DIOS and correlated with hypertension (p = 0.03). Different oxylipin signatures were observed in HH before and after the iron-rich meal. Discriminant oxylipins include epoxy fatty acids derived from docosahexaenoic acid and arachidonic acid as well as 13-HODE and 9-HODE. Mediation analysis found no major contribution of dietary iron absorption for 16/22 oxylipins significantly affected by the meal.

DISCUSSION

The oxylipin profiles of HH and DIOS seemed similar except for 20-HETE, possibly reflecting different hypertension prevalence between the two groups. Oxylipins were significantly affected by the iron-rich meal, but the specific contribution of iron was not clear. Although iron may contribute to oxidative stress and inflammation in HH and DIOS, this does not seem to directly affect oxylipin metabolism.

The enantioselective separation and quantitation of the hydroxy-metabolites of arachidonic acid by liquid chromatography - tandem mass spectrometry

Arachidonic acid (AA) is a polyunsaturated fatty acid with a structure of 20:4(ω-6). Cytochrome P450s (CYPs) metabolize AA to several regioisomers and enantiomers of hydroxyeicosatetraenoic acids (HETEs). The hydroxy-metabolites (HETEs) exist as enantiomers in the biological system. The chiral assays developed for HETEs are so far limited to a few assays reported for midchain HETEs. The developed method is capable of quantitative analysis for midchain, subterminal HETE enantiomers, and terminal HETEs in microsomes. The peak area or height ratios were linear over concentrations ranging (0.01 -0.6 µg/ml) with r2 > 0.99. The intra-run percent error and coefficient of variation (CV) were ≤ ± 12 %. The inter-run percent error and coefficient of variation (CV)were ≤ ± 13 %, and ≤ 15 %, respectively. The matrix effect for the assay was also within the acceptable limit (≤ ± 15 %). The recovery of HETE metabolites ranged from 70 % to 115 %. The method showed a reliable and robust performance for chiral analysis of cytochrome P450-mediated HETE metabolites.

Exploring human CYP4 enzymes: physiological roles, function in diseases and focus on inhibitors

The cytochrome P450 (CYP)4 family of enzymes are monooxygenases responsible for the ω-oxidation of endogenous fatty acids and eicosanoids and play a crucial part in regulating numerous eicosanoid signaling pathways. Recently, CYP4 gained attention as a potential therapeutic target for several human diseases, including cancer, cardiovascular diseases and inflammation. Small-molecule inhibitors of CYP4 could provide promising treatments for these diseases. The aim of the present review is to highlight the advances in the field of CYP4, discussing the physiology and pathology of the CYP4 family and compiling CYP4 inhibitors into groups based on their chemical classes to provide clues for the future discovery of drug candidates targeting CYP4. Teaser: This review provides an updated view of the physiology and pathology of CYP4 enzymes. CYP4 inhibitors are compiled based on their skeletons to provide clues for the future discovery of drug candidates targeting CYP4.

The Plasma Oxylipin Signature Provides a Deep Phenotyping of Metabolic Syndrome Complementary to the Clinical Criteria

Metabolic syndrome (MetS) is a complex condition encompassing a constellation of cardiometabolic abnormalities. Oxylipins are a superfamily of lipid mediators regulating many cardiometabolic functions. Plasma oxylipin signature could provide a new clinical tool to enhance the phenotyping of MetS pathophysiology. A high-throughput validated mass spectrometry method, allowing for the quantitative profiling of over 130 oxylipins, was applied to identify and validate the oxylipin signature of MetS in two independent nested case/control studies involving 476 participants. We identified an oxylipin signature of MetS (coined OxyScore), including 23 oxylipins and having high performances in classification and replicability (cross-validated AUC_ROC of 89%, 95% CI: 85–93% and 78%, 95% CI: 72–85% in the Discovery and Replication studies, respectively). Correlation analysis and comparison with a classification model incorporating the MetS criteria showed that the oxylipin signature brings consistent and complementary information to the clinical criteria. Being linked with the regulation of various biological processes, the candidate oxylipins provide an integrative phenotyping of MetS regarding the activation and/or negative feedback regulation of crucial molecular pathways. This may help identify patients at higher risk of cardiometabolic diseases. The oxylipin signature of patients with metabolic syndrome enhances MetS phenotyping and may ultimately help to better stratify the risk of cardiometabolic diseases.

Eicosanoids in inflammation in the blood and the vessel

Polyunsaturated fatty acids (PUFAs) are structural components of membrane phospholipids in cells. PUFAs regulate cellular function through the formation of derived lipid mediators termed eicosanoids. The oxygenation of 20-carbon PUFAs via the oxygenases cyclooxygenases, lipoxygenases, or cytochrome P450, generates a class of classical eicosanoids including prostaglandins, thromboxanes and leukotrienes, and also the more recently identified hydroxy-, hydroperoxy-, epoxy- and oxo-eicosanoids, and the specialized pro-resolving (lipid) mediators. These eicosanoids play a critical role in the regulation of inflammation in the blood and the vessel. While arachidonic acid-derived eicosanoids are extensively studied due to their pro-inflammatory effects and therefore involvement in the pathogenesis of inflammatory diseases such as atherosclerosis, diabetes mellitus, hypertension, and the coronavirus disease 2019; in recent years, several eicosanoids have been reported to attenuate exacerbated inflammatory responses and participate in the resolution of inflammation. This review focused on elucidating the biosynthesis and the mechanistic signaling of eicosanoids in inflammation, as well as the pro-inflammatory and anti-inflammatory effects of these eicosanoids in the blood and the vascular wall.

The Role of Arachidonic Acid Metabolism in Myocardial Ischemia-Reperfusion Injury

Patients with myocardial ischemic diseases or who are undergoing one of various heart treatments, such as open heart surgery, coronary artery bypass grafting, percutaneous coronary artery intervention or drug thrombolysis, face myocardial ischemia-reperfusion injury (MIRI). However, no effective treatment is currently available for MIRI. To improve the prognosis of people with cardiovascular disease, it is important to research the mechanism of MIRI. Arachidonic acid (AA) is one of the focuses of current research. The various metabolic pathways of AA are closely related to the development of cardiovascular disease, and the roles of various metabolites in ischemia-reperfusion injury have gradually been confirmed. AA is mainly metabolized in the cyclooxygenase (COX) pathway, lipoxygenase (LOX) pathway, and cytochrome P450 monooxygenase (CYP) pathway. This paper summarizes the progress of research on these three major AA metabolic pathways with respect to MIRI.