Regulation of the cytochrome P450 epoxyeicosanoid pathway is associated with distinct histologic features in pediatric non-alcoholic fatty liver disease

1,25-dihydroxyvitamin D3 improves non-alcoholic steatohepatitis phenotype in a diet-induced rat model

We studied the potential protective effects of 1,25-dihydroxyvitamin D3 (1,25 VD3) supplementation on liver damage induced by a choline-deficient (CD) diet in rats, where impaired liver function leads to decreased 25-hydroxyvitamin D3 levels, the precursor for the active 1,25 VD3. The CD diet reduced serum 25 VD3 levels and increased liver enzymes, indicative of liver damage. Conversely, 1,25 VD3 supplementation alleviated liver damage, reducing liver enzymes and improving histopathological features characteristic of non-alcoholic steatohepatitis (NASH). Oxidative stress and inflammation were mitigated by 1,25 VD3, as evidenced by decreased malondialdehyde and nuclear factor kappa B (NF-κB) expression, and increased total antioxidant capacity (TAOC). 1,25 VD3 also enhanced fatty acid metabolism by increasing peroxisome proliferator-activated receptor alpha (PPARα) and carnitine palmitoyltransferase-1 (CPT-1) expression, promoting lipid transport and oxidation. Additionally, 1,25 VD3 supplementation modulated inflammation by increasing PPARγ expression, reducing NF-κB expression, and decreasing pro-inflammatory cytokines (TNF-α, IL-1β). Anti-inflammatory cytokines (IL-10, IL-4) were increased, and macrophage polarization was shifted towards an anti-inflammatory M2 phenotype. Moreover, 1,25 VD3 upregulated CYP2J3, a cytochrome P450 epoxygenase that converts arachidonic acid to anti-inflammatory epoxyeicosatrienoic acids (EETs) and decreased soluble epoxide hydrolase activity, likely contributing to increased EET levels. Correlation studies revealed positive associations between 1,25 VD3 supplementation, CYP2J3 expression, EETs, as well as negative correlations with NF-κB and TNF-α. PPARα expression positively correlated with TAOC and CPT-1, while PPARγ expression negatively correlated with inflammatory markers. These findings demonstrate the therapeutic potential of 1,25 VD3 in alleviating NASH through regulation of fatty acid metabolism, inflammation, and oxidative stress.

Royal jelly acid alleviates diet-induced hyperlipidemia through regulation of oxidative stress and tryptophan metabolism

Royal jelly acid is a unique unsaturated fatty acid isolated from royal jelly. Recently, royal jelly acid was proposed to have potential therapeutic effects on hyperlipidemia. However, its effect on hyperlipidemia and the underlying molecular mechanism remains unclear. Therefore, in this study, we analyzed the mechanism of anti-hyperlipidemia of royal jelly acid through animal experiments and plasma metabolomics in conjunction with human network pharmacology and molecular docking analyses. We found that royal jelly acid could significantly decrease the serum lipid levels, ameliorate hepatic pathological injury, and reduce the level of oxidative stress in the experimental rats. A total of 41 key metabolites and 10 hub targets played key roles in the exertion of anti-hyperlipidemic effects, including tumor necrosis factor (TNF), insulin (INS) and epidermal growth factor receptor (EGFR). A total of 24 pathways, including tryptophan, citrate cycle, and arachidonic acid metabolisms, were identified as the key pathways involved in royal jelly acid-alleviated hyperlipidemia. The present findings provide new insights into the pathogenesis, diagnosis, and treatment targets of hyperlipidemia as well as contribute to the development and utilization of royal jelly acid related products.

Emerging mechanisms of organ crosstalk: The role of oxylipins

There is growing interest in the role of oxylipins in the pathophysiology of several diseases. This is accompanied by a limited but evolving evidence base describing augmented oxylipin concentrations in a range of complications including cardiovascular disease, obesity, liver disease and neurological disorders. Despite this, literature describing oxylipin profiles in blood and multiple organs is inconsistent and the mechanisms by which these profiles are altered, and the relationships between localised tissue and circulating oxylipins are poorly understood. Inflammation and immune response associated with disease requires communication across organs and physiological systems. For example, inflammation and comorbidities associated with obesity extend beyond the adipose tissue and affect the vascular, hepatobiliary and digestive systems amongst others. Communication between organs and physiological systems is implicated in the progression of disease as well as the maintenance of homeostasis. There is emerging evidence for the role of oxylipins as a mechanism of communication in organ crosstalk but the role of these in orchestrating multiple organ and system responses is poorly understood. Herein, we review evidence to support and describe the role of oxylipins in organ crosstalk via the cardiosplenic and gut-link axis. In addition, we review emerging mechanisms of oxylipin regulation, the gut microbiome and modification using nutritional intervention. Finally, we describe future perspectives for addressing challenges in measurement and interpretation of oxylipin research with focus on the host genome as a modifier of oxylipin profiles and response to dietary lipid intervention.

Multi-tissue profiling of oxylipins reveal a conserved up-regulation of epoxide:diol ratio that associates with white adipose tissue inflammation and liver steatosis in obesity

BACKGROUND

Obesity drives maladaptive changes in the white adipose tissue (WAT) which can progressively cause insulin resistance, type 2 diabetes mellitus (T2DM) and metabolic dysfunction-associated liver disease (MASLD). Obesity-mediated loss of WAT homeostasis can trigger liver steatosis through dysregulated lipid pathways such as those related to polyunsaturated fatty acid (PUFA)-derived oxylipins. However, the exact relationship between oxylipins and metabolic syndrome remains elusive and cross-tissue dynamics of oxylipins are ill-defined.

METHODS

We quantified PUFA-related oxylipin species in the omental WAT, liver biopsies and plasma of 88 patients undergoing bariatric surgery (female N = 79) and 9 patients (female N = 4) undergoing upper gastrointestinal surgery, using UPLC-MS/MS. We integrated oxylipin abundance with WAT phenotypes (adipogenesis, adipocyte hypertrophy, macrophage infiltration, type I and VI collagen remodelling) and the severity of MASLD (steatosis, inflammation, fibrosis) quantified in each biopsy. The integrative analysis was subjected to (i) adjustment for known risk factors and, (ii) control for potential drug-effects through UPLC-MS/MS analysis of metformin-treated fat explants ex vivo.

FINDINGS

We reveal a generalized down-regulation of cytochrome P450 (CYP)-derived diols during obesity conserved between the WAT and plasma. Notably, epoxide:diol ratio, indicative of soluble epoxide hydrolyse (sEH) activity, increases with WAT inflammation/fibrosis, hepatic steatosis and T2DM. Increased 12,13-EpOME:DiHOME in WAT and liver is a marker of worsening metabolic syndrome in patients with obesity.

INTERPRETATION

These findings suggest a dampened sEH activity and a possible role of fatty acid diols during metabolic syndrome in major metabolic organs such as WAT and liver. They also have implications in view of the clinical trials based on sEH inhibition for metabolic syndrome.

FUNDING

Wellcome Trust (PS3431_WMIH); Duke-NUS (Intramural Goh Cardiovascular Research Award (Duke-NUS-GCR/2022/0020); National Medical Research Council (OFLCG22may-0011); National Institute of Environmental Health Sciences (Z01 ES025034); NIHR Imperial Biomedical Research Centre.

Lipidome Changes Associated with a Diet-Induced Reduction in Hepatic Fat among Adolescent Boys with Metabolic Dysfunction-Associated Steatotic Liver Disease

Little is known about lipid changes that occur in the setting of metabolic-dysfunction-associated steatotic liver disease (MASLD) regression. We previously reported improvements in hepatic steatosis, de novo lipogenesis (DNL), and metabolomic profiles associated with oxidative stress, inflammation, and selected lipid metabolism in 40 adolescent boys (11-16 y) with hepatic steatosis ≥5% (98% meeting the definition of MASLD). Participants were randomized to a low-free-sugar diet (LFSD) (n = 20) or usual diet (n = 20) for 8 weeks. Here, we employed untargeted/targeted lipidomics to examine lipid adaptations associated with the LFSD and improvement of hepatic steatosis. Our LC-MS/MS analysis revealed decreased triglycerides (TGs), diacylglycerols (DGs), cholesteryl esters (ChE), lysophosphatidylcholine (LPC), and phosphatidylcholine (PC) species with the diet intervention (p < 0.05). Network analysis demonstrated significantly lower levels of palmitate-enriched TG species post-intervention, mirroring the previously shown reduction in DNL in response to the LFSD. Targeted oxylipins analysis revealed a decrease in the abundance of 8-isoprostane and 14,15-DiHET and an increase in 8,9-DiHET (p < 0.05). Overall, we observed reductions in TGs, DGs, ChE, PC, and LPC species among participants in the LFSD group. These same lipids have been associated with MASLD progression; therefore, our findings may indicate normalization of key biological processes, including lipid metabolism, insulin resistance, and lipotoxicity. Additionally, our targeted oxylipins assay revealed novel changes in eicosanoids, suggesting improvements in oxidative stress. Future studies are needed to elucidate the mechanisms of these findings and prospects of these lipids as biomarkers of MASLD regression.

METTL3 exacerbates insulin resistance in hepatocytes by regulating m6A modification of cytochrome P450 2B6

BACKGROUND

Insulin resistance (IR) in hepatocytes endangers human health, and frequently results in the development of non-alcoholic fatty liver disease (NAFLD). Research on m6A methylation of RNA molecules has gained popularity in recent years; however, the molecular mechanisms regulating the processes of m6A modification and IR are not known. The cytochrome P450 (CYP450) enzyme system, which is mainly found in the liver, is associated with the pathogenesis of NAFLD. However, few studies have been conducted on CYP450 related m6A methylation. Here, we investigated the role of the methyltransferase METTL3 in exacerbating IR in hepatocytes, mainly focusing on the regulation of m6A modifications in CYP2B6.

METHODS AND RESULTS

Analysis using dot blot and epitranscriptomic chips revealed that the m6A modification pattern of the transcriptome in high-fat diet (HFD)-induced fatty liver and free fatty acid (FFA)-induced fatty hepatocytes showed significant changes. CYP450 family members, especially Cyp2b10, whose homolog in humans is CYP2B6, led to a noticeable increase in m6A levels in HFD-induced mice livers. Application of the METTL3 methyltransferase inhibitor, STM2457, increased the level of insulin sensitivity in hepatocytes. We then analyzed the role of METTL3 in regulating m6A modification of CYP2B6 in hepatocytes. METTL3 regulated the m6A modification of CYP2B6, and a positive correlation was found between the levels of CYP2B6 translation and m6A modifications. Furthermore, interference with METTL3 expression and exposure to STM2457 inhibited METTL3 activity, which in turn interfered with the phosphorylated insulin receptor substrate (pIRS)-glucose transporter 2 (GLUT2) insulin signaling pathway; overexpression of CYP2B6 hindered IRS phosphorylation and translocation of GLUT2 to membranes, which ultimately exacerbated IR.

CONCLUSION

These findings offer unique insights into the role that METTL3-mediated m6A modifications of CYP2B6 play in regulating insulin sensitivity in hepatocytes and provide key information for the development of strategies to induce m6A modifications for the clinical treatment of NAFLD.

Bioactive oxylipins in type 2 diabetes mellitus patients with and without hypertriglyceridemia

Objective

Dyslipidemia, in particular elevated triglycerides (TGs) contribute to increased cardiovascular risk in type 2 diabetes mellitus (T2DM). In this pilot study we aimed to assess how increased TGs affect hepatic fat as well as polyunsaturated fatty acid (PUFA) metabolism and oxylipin formation in T2DM patients.

Methods

40 patients with T2DM were characterized analyzing routine lipid blood parameters, as well as medical history and clinical characteristics. Patients were divided into a hypertriglyceridemia (HTG) group (TG ≥ 1.7mmol/l) and a normal TG group with TGs within the reference range (TG < 1.7mmol/l). Profiles of PUFAs and their oxylipins in plasma were measured by gas chromatography and liquid chromatography/tandem mass spectrometry. Transient elastography (TE) was used to assess hepatic fat content measured as controlled attenuation parameter (CAP) (in dB/m) and the degree of liver fibrosis measured as stiffness (in kPa).

Results

Mean value of hepatic fat content measured as CAP as well as body mass index (BMI) were significantly higher in patients with high TGs as compared to those with normal TGs, and correlation analysis showed higher concentrations of TGs with increasing CAP and BMI scores in patients with T2DM. There were profound differences in plasma oxylipin levels between these two groups. Cytochrome P450 (CYP) and lipoxygenase (LOX) metabolites were generally more abundant in the HTG group, especially those derived from arachidonic acid (AA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), γ-linolenic acid (γ-LA), and α-linolenic acid (α-LA), and a strong correlation between TG levels and plasma metabolites from different pathways was observed.

Conclusions

In adult patients with T2DM, elevated TGs were associated with increased liver fat and BMI. Furthermore, these patients also had significantly higher plasma levels of CYP- and LOX- oxylipins, which could be a novel indicator of increased inflammatory pathway activity, as well as a novel target to dampen this activity.

Role of Oxylipins in the Inflammatory-Related Diseases NAFLD, Obesity, and Type 2 Diabetes

Oxygenated polyunsaturated fatty acids (oxylipins) are bioactive molecules established as important mediators during inflammation. Different classes of oxylipins have been found to have opposite effects, e.g., pro-inflammatory prostaglandins and anti-inflammatory resolvins. Production of the different classes of oxylipins occurs during distinct stages of development and resolution of inflammation. Chronic inflammation is involved in the progression of many pathophysiological conditions and diseases such as non-alcoholic fatty liver disease, insulin resistance, diabetes, and obesity. Determining oxylipin profiles before, during, and after inflammatory-related diseases could provide clues to the onset, development, and prevention of detrimental conditions. This review focusses on recent developments in our understanding of the role of oxylipins in inflammatory disease, and outlines novel technological advancements and approaches to study their action.

Advances in paediatric nonalcoholic fatty liver disease: Role of lipidomics

Due its close relationship with obesity, nonalcoholic fatty liver disease (NAFLD) has become a major worldwide health issue even in childhood. The most accepted pathophysiological hypothesis is represented by the "multiple hits" theory, in which both hepatic intracellular lipid accumulation and insulin resistance mainly contribute to liver injury through several factors. Among these, lipotoxicity has gained particular attention. In this view, the pathogenic role of different lipid classes in NAFLD (e.g., sphingolipids, fatty acids, ceramides, etc.) has been highlighted in recent lipidomics studies. Although there is some contrast between plasma and liver findings, lipidomic profile in the NAFLD context provides novel insights by expanding knowledge in the intricate field of NAFLD pathophysiology as well as by suggesting innovative therapeutic approaches in order to improve both NAFLD prevention and treatment strategies. Selective changes of distinct lipid species might be an attractive therapeutic target for treating NAFLD. Herein the most recent evidence in this attractive field has been summarized to provide a comprehensive overview of the lipidomic scenario in paediatric NAFLD.