Molecular mechanisms of nonalcoholic fatty liver disease: Potential role for 12-lipoxygenase

A systematic review of the anti-inflammatory and anti-fibrotic potential of human umbilical cord mesenchymal stem cells-derived exosomes in experimental models of liver regeneration

Chronic liver injuries and their complications are leading causes of death, especially in developing countries (Sharma and Nagalli in Sex/Gender-Specific Medicine in the Gastrointestinal Diseases, StatPearls Publishing, 2023). The available and effective treatment plans are limited, implicating the need for innovative treatment approaches (Tsuchiya et al. in Inflamm Regener, 2019;Sharma and Nagalli in Sex/Gender-Specific Medicine in the Gastrointestinal Diseases, StatPearls Publishing, 2023;Younossi et al. in Clin Gastroenterol Hepatol 21:1978-1991, 2023;). This paper aims to summarize the effects and mechanisms of hUC-MSC-exo on liver injuries and its complications; it also suggests future directions for future research. The outcomes of interest are the morphology and histology of the liver, pathology score, liver function enzyme, glucose and lipid metabolism, and the effect hUC-MSC-exo had on gene regulation regarding liver diseases. A comprehensive review of nineteen studies was conducted to assess the effectiveness of the implementation of the hUC-MSC-Exo, instilling confidence in the validity of the findings. Regarding the morphology and histology of the liver and pathology score, hUC-MSC-exo treatment resulted in improved liver morphology post-treatment, as indicated by the reduction in pathology scores. However, these observed improvements in the liver surface are not directly attributed to the hUC-MSC-Exo itself but to the overall healing processes stimulated by the treatment. In physiological outcomes, hUC-MSC-exo also improves glucose and lipid metabolism, especially in diet-induced liver injury and its complications. In gene regulation, one interesting gene in this intervention is the fat mass and obesity-associated (FTO), in which hUC-MSC-exo combined with miRNAs can suppress FTO. HUC-MSC-Exo can improve by utilizing several possible pathways, targeting pinpoints in the pathogenesis of liver disease or glucose and lipid metabolism. This study presents hUC-MSC-exo better in all outcomes of interest compared to the control or sham group. Further specification of indications of the hUC-MSC-exo method may be beneficial and essential to be analyzed in future reviews to better understand the effectiveness of each hUC-MSC-exo dose, duration, and medium.

Hepatic oxylipin profiles in mouse models of Wilson disease: New insights into early hepatic manifestations

Hepatic inflammation is commonly identified in Wilson disease (WD), a genetic disease of hepatic and brain copper accumulation. Copper accumulation is associated with increased oxidative stress and reactive oxygen species generation which may result in non-enzymatic oxidation of membrane-bound polyunsaturated fatty acids (PUFA). PUFA can be oxidized enzymatically via lipoxygenases (LOX), cyclooxygenases (COX), and cytochrome P450 monooxygenases (CYP). Products of PUFA oxidation are collectively known as oxylipins (OXL) and are bioactive lipids that modulate hepatic inflammation. We examined hepatic OXL profiles at early stages of WD in two mouse models, the toxic milk mouse from The Jackson Laboratory (tx-j) and the Atp7b knockout on a C57Bl/6 background (Atp7b-/-B6). Targeted lipidomic analysis performed by ultra-high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry showed that in both tx-j and Atp7b-/-B6 mice, hepatic OXL profiles were altered with higher thromboxane and prostaglandins levels. The levels of oxidative stress marker, 9-HETE were increased more markedly in tx-j mice. However, both genotypes showed upregulated transcript levels of many genes related to oxidative stress and inflammation. Both genotypes showed higher prostaglandins, thromboxin along with higher PUFA-derived alcohols, diols, and ketones with altered epoxides; the expression of Alox5 was upregulated and many CYP-related genes were dysregulated. Pathway analyses show dysregulation in arachidonic acid and linoleic acid metabolism characterizes mice with WD. Our findings indicate alterations in hepatic PUFA metabolism in early-stage WD and suggest the upregulation of both, non-enzymatic ROS-dependent and enzymatic PUFA oxidation, which could have implications for hepatic manifestations in WD and represent potential targets for future therapies.

α-Lipoic acid - a promising agent for attenuating inflammation and preventing steatohepatitis in rats fed a high-fat diet

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a prevalent liver disorder affecting a significant part of the global population. This study aimed to investigate the potential therapeutic effects of α-lipoic acid (α-LA) on the inflammatory response during simple steatosis development and progression into steatohepatitis. The study used the MASLD model in male Wistar rats that were fed a standard diet or a high-fat diet (HFD) for 8 weeks. Throughout the entire experiment, half of the animals received α-LA supplementation. The hepatic activity of pro-inflammatory n-6 and anti-inflammatory n-3 polyunsaturated fatty acid (PUFA) pathways and the concentration of arachidonic acid (AA) in selected lipid fractions were determined by the gas-liquid chromatography (GLC). The hepatic expression of proteins from inflammatory pathway was measured by the Western blot technique. The level of eicosanoids, cytokines and chemokines was assessed by the ELISA or multiplex assay kits. The results showed that α-LA supplementation attenuated the activity of n-6 PUFA pathway in FFA and DAG and increased the activity of n-3 PUFA pathway in PL, TAG and DAG. In addition, the administration of α-LA decreased the concentration of AA in DAG and FFA, indicating its potential protective effect on the deterioration of simple hepatic steatosis. The supplementation of α-LA also increased the expression of COX-1 and COX-2 with the lack of significant changes in prostaglandins profile. We observed an increase in the expression of 12/15-LOX, which was reflected in an increase in lipoxin A4 (LXA4) level. A decrease in pro-inflammatory cytokines and an increase in anti-inflammatory cytokines was also noticed in the liver of rats treated with HFD and α-LA. Our observations confirm that α-LA treatment has potential protective effects on inflammation development in the MASLD model. We believe that α-LA has a preventive impact when it comes to the progression of simple steatosis lesions to steatohepatitis.

Inflammatory signaling in NASH driven by hepatocyte mitochondrial dysfunctions

Liver steatosis, inflammation, and variable degrees of fibrosis are the pathological manifestations of nonalcoholic steatohepatitis (NASH), an aggressive presentation of the most prevalent chronic liver disease in the Western world known as nonalcoholic fatty liver (NAFL). Mitochondrial hepatocyte dysfunction is a primary event that triggers inflammation, affecting Kupffer and hepatic stellate cell behaviour. Here, we consider the role of impaired mitochondrial function caused by lipotoxicity during oxidative stress in hepatocytes. Dysfunction in oxidative phosphorylation and mitochondrial ROS production cause the release of damage-associated molecular patterns from dying hepatocytes, leading to activation of innate immunity and trans-differentiation of hepatic stellate cells, thereby driving fibrosis in NASH.

Risk Factors of Non-alcoholic Fatty Liver Disease in the Iranian Adult Population: A Systematic Review and Meta-analysis

Context: Non-alcoholic fatty liver disease (NAFLD) is progressing considerably worldwide. Identifying the risk factors of NAFLD is a critical step in preventing its progression. Methods: In November 2022, two independent researchers studied seven databases, including PubMed, ISI/WoS, ProQuest, Scopus, SID, Magiran, and Google Scholar, and reference list of relevant articles, searching studies that assessed NAFLD risk factors in the Iranian adult population. Heterogeneity between studies was assessed by Cochran’s test and its composition using I2 statistics. A random-effects model was used when heterogeneity was observed; otherwise, a fixed-effects model was applied. Egger’s regression test and Trim-and-Fill analysis were used to assess publication bias. Comprehensive Meta-analysis software (version 3) was used for the analyses of the present study. Results: The results of this study showed significant associations between NAFLD with age (n = 15, odds ratio (OR) = 2.12, 95% CI: 1.79 - 2.51), body mass index (n = 46, OR = 5.00, 95% CI: 3.34 - 7.49), waist circumference (n = 20, OR = 6.37, 95% CI: 3.25 - 12.48), waist-to-hip ratio (n = 17, OR = 4.72, 95% CI: 3.93 - 5.66), total cholesterol (n = 39, OR = 1.80, 95% CI: 1.52 - 2.13), high-density lipoprotein (n = 37, OR = 0.53, 95% CI: 0.44 - 0.65), low-density lipoprotein (n = 31, OR = 1.68, 95% CI: 1.38 - 2.05), triglyceride (n = 31, OR = 3.21, 95% CI: 2.67 - 3.87), alanine aminotransferase (n = 26, OR = 4.06, 95% CI: 2.94 - 5.62), aspartate aminotransferase (n = 27, OR = 2.16, 95% CI: 1.50 - 3.12), hypertension (n = 13, OR = 2.53, 95% CI: 2.32 - 2.77), systolic blood pressure (n = 13, OR = 1.83, 95% CI: 1.53 - 2.18), diastolic blood pressure (n = 14, OR = 1.80, 95% CI: 1.48 - 2.20), fasting blood sugar (n = 31, OR = 2.91, 95% CI: 2.11- 4.01), homeostatic model assessment for insulin resistance (n = 5, OR = 1.92, 95% CI: 1.48 - 2.59), diabetes mellitus (n = 15, OR = 3.04, 95% CI: 2.46 - 3.75), metabolic syndrome (n = 10, OR = 3.56, 95% CI: 2.79 - 4.55), and physical activity (n = 11, OR = 0.32, 95% CI: 0.24 - 0.43) (P < 0.05). Conclusions: In conclusion, several factors are significantly associated with NAFLD. However, anthropometric indices had the strongest relationship with NAFLD in the Iranian adult population.

Functional Characterization of Transgenic Mice Overexpressing Human 15-Lipoxygenase-1 (ALOX15) under the Control of the aP2 Promoter

Arachidonic acid lipoxygenases (ALOX) have been implicated in the pathogenesis of inflammatory, hyperproliferative, neurodegenerative, and metabolic diseases, but the physiological function of ALOX15 still remains a matter of discussion. To contribute to this discussion, we created transgenic mice (aP2-ALOX15 mice) expressing human ALOX15 under the control of the aP2 (adipocyte fatty acid binding protein 2) promoter, which directs expression of the transgene to mesenchymal cells. Fluorescence in situ hybridization and whole-genome sequencing indicated transgene insertion into the E1-2 region of chromosome 2. The transgene was highly expressed in adipocytes, bone marrow cells, and peritoneal macrophages, and ex vivo activity assays proved the catalytic activity of the transgenic enzyme. LC-MS/MS-based plasma oxylipidome analyses of the aP2-ALOX15 mice suggested in vivo activity of the transgenic enzyme. The aP2-ALOX15 mice were viable, could reproduce normally, and did not show major phenotypic alterations when compared with wildtype control animals. However, they exhibited gender-specific differences with wildtype controls when their body-weight kinetics were evaluated during adolescence and early adulthood. The aP2-ALOX15 mice characterized here can now be used for gain-of-function studies evaluating the biological role of ALOX15 in adipose tissue and hematopoietic cells.

Effect of atorvastatin on lipoxygenase pathway-related gene expression in an in vitro model of lipid accumulation in hepatocytes

Lipid accumulation in hepatocytes can result from an imbalance between lipid acquisition and lipid catabolism. In recent years, it has been discovered that eicosanoids derived from arachidonic acid (AA) have the potential to create specialized pro-resolving lipid mediators to actively resolve inflammation, but it is not clear whether AA and lipoxygenases exert effects on hepatic inflammation. Here, the effects of atorvastatin on the expression of cytoplasmic phospholipase A2 (cPLA2) and lipoxygenase pathway genes (ALOX5, ALOX12, ALOX15, and ALOX15B) were evaluated in an in vitro model of palmitic acid (PA)-induced hepatocyte lipid accumulation in McA-RH7777 (McA) cells. Palmitic acid increased cPLA2 expression, intracellular AA levels, and ALOX12 expression (P < 0.05). Atorvastatin at various concentrations had no significant effects on AA levels or on cPLA2, ALOX15, and ALOX15B expressions. ALOX5 was not detected, despite multiple measurements. Pro-inflammatory IL-1β expression levels were upregulated by PA (P < 0.01) and attenuated by atorvastatin (P < 0.001). TNFα did not differ among groups. The expression levels of anti-inflammatory IL-10 decreased in response to PA (P < 0.05), but were not affected by atorvastatin. In conclusion, in an in vitro model of lipid accumulation in McA cells, atorvastatin reduced IL-1β; however, its effect was not mediated by AA and the lipoxygenase pathway at the established doses and treatment duration. Further research is required to investigate time-response data, as well as other drugs and integrated cell systems that could influence the lipoxygenase pathway and modulate inflammation in liver diseases.

Metabolomics Provides Insights into Renoprotective Effects of Semaglutide in Obese Mice

PURPOSE

Semaglutide, a new long-acting glucagon-like peptide-1 analogue, has shown benefits for renal diseases, but its direct role on kidney metabolism under obesity remains unclear. The study aims to elucidate the protective effect and metabolic modulation mechanism of semaglutide on obesity-related kidney injury.

METHODS

Male C57BL/6J mice were divided into control and obesity groups. Mice in the obesity group had a high-fat diet and were treated with or without semaglutide (30nmol/kg/day). The study assayed blood biochemistry and then evaluated renal pathological injury through Periodic Acid-Schiff staining and electron microscopy. Metabolomics was utilized to analyze obesity-related metabolites in kidney samples.

RESULTS

Semaglutide significantly improved glucose homeostasis, insulin resistance, and kidney injury in obese mice. We successfully identified 377 altered metabolites (P<0.05). It was suggested that semaglutide directly improved oxidative stress and inflammation-related metabolites such as nicotinamide adenine dinucleotide (NAD+) and adenosine in the kidney of obese mice, which have not been documented in obesity-related kidney injury. Relevant enriched pathways were included phospholipids and lysophospholipids metabolism, purine metabolism, NAD+ metabolism, and insulin resistance-related metabolism. They could serve as potential targets for intervention of obesity-related kidney injury.

CONCLUSION

Our study revealed the metabolomics-based renoprotective mechanism of semaglutide in obese mice for the first time. The innovation lied in the identified metabolites such as NAD+ and adenosine targeted by semaglutide, which have not been documented in obesity-related kidney injury. Semaglutide may be a promising therapy for obesity-related kidney diseases.

Potential role of selenium in alleviating obesity-related iron dyshomeostasis

Obesity is a serious health problem in modern life and increases the risk of many comorbidities including iron dyshomeostasis. In contrast to malnourished anemia, obesity-related iron dyshomeostasis is mainly caused by excessive fat accumulation, inflammation, and disordered gut microbiota. In obesity, iron dyshomeostasis also induces disorders associated with gut microbiota, neurodegenerative injury, oxidative damage, and fat accumulation in the liver. Selenium deficiency is often accompanied by obesity or iron deficiency, and selenium supplementation has been shown to alleviate obesity and overcome iron deficiency. Selenium inhibits fat accumulation and exhibits anti-inflammatory activity. It regulates gut microbiota, prevents neurodegenerative injury, alleviates oxidative damage to the body, and ameliorates hepatic fat accumulation. These effects theoretically meet the requirements for the inhibition of factors underlying obesity-related iron dyshomeostasis. Selenium supplementation may have a potential role in the alleviation of obesity-related iron dyshomeostasis. This review verifies this hypothesis in theory. All the currently reported causes and results of obesity-related iron dyshomeostasis are reviewed comprehensively, together with the effects of selenium. The challenges and strategies of selenium supplementation are also discussed. The findings demonstrate the possibility of selenium-containing drugs or functional foods in alleviating obesity-related iron dyshomeostasis.

Platelet-Activating Factor Promotes the Development of Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a multifaceted clinicopathological syndrome characterised by excessive hepatic lipid accumulation that causes steatosis, excluding alcoholic factors. Platelet-activating factor (PAF), a biologically active lipid transmitter, induces platelet activation upon binding to the PAF receptor. Recent studies have found that PAF is associated with gamma-glutamyl transferase, which is an indicator of liver disease. Moreover, PAF can stimulate hepatic lipid synthesis and cause hypertriglyceridaemia. Furthermore, the knockdown of the PAF receptor gene in the animal models of NAFLD helped reduce the inflammatory response, improve glucose homeostasis and delay the development of NAFLD. These findings suggest that PAF is associated with NAFLD development. According to reports, patients with NAFLD or animal models have marked platelet activation abnormalities, mainly manifested as enhanced platelet adhesion and aggregation and altered blood rheology. Pharmacological interventions were accompanied by remission of abnormal platelet activation and significant improvement in liver function and lipids in the animal model of NAFLD. These confirm that platelet activation may accompany a critical importance in NAFLD development and progression. However, how PAFs are involved in the NAFLD signalling pathway needs further investigation. In this paper, we review the relevant literature in recent years and discuss the role played by PAF in NAFLD development. It is important to elucidate the pathogenesis of NAFLD and to find effective interventions for treatment.

Multiple omics study identifies an interspecies conserved driver for nonalcoholic steatohepatitis

Lipotoxicity is a recognized pathological trigger and accelerator of nonalcoholic steatohepatitis (NASH). However, the molecular basis of lipotoxicity-induced NASH remains elusive. Here, we systematically mapped the changes in hepatic transcriptomic landscapes in response to lipotoxic insults across multiple species. Conserved and robust activation of the arachidonic acid pathway, in particular the arachidonate 12-lipoxygenase (ALOX12) gene, was closely correlated with NASH severity in humans, macaques with spontaneously developed NASH, as well as swine and mouse dietary NASH models. Using gain- and loss-of-function studies, we found that ALOX12 markedly exacerbated NASH in both mice and Bama pig models. ALOX12 was shown to induce NASH by directly targeting acetyl-CoA carboxylase 1 (ACC1) via a lysosomal degradation mechanism. Overall, our findings reveal a key molecular driver of NASH pathogenesis and suggest that ALOX12-ACC1 interaction may be a therapeutic target in NASH.

Antisense overlapping long non-coding RNA regulates coding arachidonate 12-lipoxygenase gene by translational interference

The arachidonate 12-lipoxygenase (ALOX12) enzyme catalyzes polyunsaturated fatty acids and facilitates generation of bioactive lipid mediators associated with various biological processes and disease pathologies. The human genome assembly revealed that the ALOX12 gene overlaps an antisense non-coding gene designated as ALOX12-antisense 1 (ALOX12-AS1). This arrangement indicates that the uncharacterized ALOX12-AS1 long non-coding RNA (lncRNA) may bind to the sense coding ALOX12 mRNA to form an antisense-sense duplex providing the basis of a novel ALOX12 regulatory mechanism. Therefore, this study was designed to determine whether the interaction of ALOX12-AS1 with ALOX12 mRNA functions as an anti-sense/sense duplex-mediated regulatory mechanism controlling the cellular content of ALOX12. Our findings indicate that two major isoforms of ALOX12-AS1 lncRNA are ubiquitously expressed in a variety of primary adult human tissues and different transformed cell types. RNA-FISH revealed cell-type-specific cytosolic as well as nuclear and nucleolar localization of the lncRNA. Interestingly, phorbol ester-induced nucleo-cytoplasmic translocation of the lncRNA in monocytic THP-1 cells resulted in a reduction of ALOX12 protein without a concomitant change in its mRNA level. This indicated ALOX12-AS1 operates via an antisense-sense duplex-mediated translational downregulation mechanism. This deduction was validated by demonstrating sense/antisense duplex formation and an association of the duplex with ribosomal proteins in HEK293 cells. Overall, this study revealed a hitherto unknown mechanism of antisense lncRNA-mediated translational downregulation of ALOX12 that adds to the existing regulatory mechanisms for the modulation of potent bioactive lipid mediators that contribute to both health and disease.

New Insights Into the Role of Autophagy in Liver Surgery in the Setting of Metabolic Syndrome and Related Diseases

Visceral obesity is an important component of metabolic syndrome, a cluster of diseases that also includes diabetes and insulin resistance. A combination of these metabolic disorders damages liver function, which manifests as non-alcoholic fatty liver disease (NAFLD). NAFLD is a common cause of abnormal liver function, and numerous studies have established the enormously deleterious role of hepatic steatosis in ischemia-reperfusion (I/R) injury that inevitably occurs in both liver resection and transplantation. Thus, steatotic livers exhibit a higher frequency of post-surgical complications after hepatectomy, and using liver grafts from donors with NAFLD is associated with an increased risk of post-surgical morbidity and mortality in the recipient. Diabetes, another MetS-related metabolic disorder, also worsens hepatic I/R injury, and similar to NAFLD, diabetes is associated with a poor prognosis after liver surgery. Due to the large increase in the prevalence of MetS, NAFLD, and diabetes, their association is frequent in the population and therefore, in patients requiring liver resection and in potential liver graft donors. This scenario requires advancement in therapies to improve postoperative results in patients suffering from metabolic diseases and undergoing liver surgery; and in this sense, the bases for designing therapeutic strategies are in-depth knowledge about the molecular signaling pathways underlying the effects of MetS-related diseases and I/R injury on liver tissue. A common denominator in all these diseases is autophagy. In fact, in the context of obesity, autophagy is profoundly diminished in hepatocytes and alters mitochondrial functions in the liver. In insulin resistance conditions, there is a suppression of autophagy in the liver, which is associated with the accumulation of lipids, being this is a risk factor for NAFLD. Also, oxidative stress occurring in hepatic I/R injury promotes autophagy. The present review aims to shed some light on the role of autophagy in livers undergoing surgery and also suffering from metabolic diseases, which may lead to the discovery of effective therapeutic targets that could be translated from laboratory to clinical practice, to improve postoperative results of liver surgeries when performed in the presence of one or more metabolic diseases.

Arachidonate 12S-lipoxygenase of platelet-type in hepatic stellate cells of methionine and choline-deficient diet-fed mice

A role of 12-lipoxygenase in the progression of non-alcoholic steatohepatitis (NASH) is suggested, although the underlying mechanism is not entirely understood. The catalytic activity of 12S-lipoxygenase that was hardly observed in liver cytosol of normal chow-fed mice was clearly detectable in that of NASH model mice prepared by feeding a methionine and choline-deficient (MCD) diet. The product profile, substrate specificity and immunogenicity indicated that the enzyme was the platelet-type isoform. The expression levels of mRNA and protein of platelet-type 12S-lipoxygenase in the liver of MCD diet-fed mice were significantly increased compared with those of normal chow-fed mice. Immunohistochemical analysis showed that platelet-type 12S-lipoxygenase colocalized with α-smooth muscle actin as well as vitamin A in the cells distributing along liver sinusoids. These results indicate that the expression level of platelet-type 12S-lipoxygenase in hepatic stellate cells was increased during the cell activation in MCD diet-fed mice, suggesting a possible role of the enzyme in pathophysiology of liver fibrosis.

Eicosanoids in Nonalcoholic Fatty Liver Disease (NAFLD) Progression. Do Serum Eicosanoids Profile Correspond with Liver Eicosanoids Content during NAFLD Development and Progression?

Nonalcoholic fatty liver disease (NAFLD) is becoming a major public health problem worldwide. The study aimed to evaluate the concentration of eicosanoids in serum and liver tissue during steatosis progression and to assess whether eicosanoid change scores may predict liver tissue remodeling. Thirty six eight-week-old male Sprague Dawley rats were enrolled and sacrificed at different stages of NAFLD. Eicosanoid concentrations, namely lipoxin A₄, hydroxyeicosatetraenoic acids (HETE), hydroxyloctadecadienoic acids (HODE), protectin DX, Maresine1, leucotriene B₄, prostaglandin E₂, and resolvin D₁ measurement in serum and liver tissue with Agilent Technologies 1260 liquid chromatography were evaluated. For the liver and serum concentrations of 9-HODE and 13-HODE, the correlations were found to be strong and positive (r > 0.7, p < 0.05). Along with NAFLD progression, HODE concentration significantly increased, and change scores were more abundant in the liver. The moderate positive correlation between liver and serum (r = 0.52, p < 0.05) was also observed for resolvin E1. The eicosanoid concentration decreased during NAFLD progression, but mostly in serum. There were significant correlations between HETE concentrations in liver and serum, but their associations were relatively low and changes the most in liver tissue. Eicosanoids profile, predominantly 9-HODE and 13-HODE, may serve as a potential biomarker for NAFLD development.

Systemic redox imbalance in patients with nonalcoholic fatty liver disease

BACKGROUND

Oxidative stress is one of the major pathologic mechanisms for the progression of nonalcoholic fatty liver disease (NAFLD). The aim of this study was to evaluate the relationship between the extent of steatosis and oxidative stress parameters in patients with NAFLD.

METHODS

The data obtained from 122 patients with NAFLD and 106 healthy controls aged 20-60 years with body mass index (BMI) ranging from 25 to 35 kg/m² . Abdominal ultrasonography was performed in participants in order to the grading of hepatic steatosis. Fasting blood samples and anthropometric measurements were collected for all study subjects. Oxidative stress was evaluated by measurement of serum malondialdehyde (MDA), oxidized low-density lipoprotein (ox-LDL), total antioxidant capacity (TAC) and erythrocyte superoxide dismutase (SOD) as well as glutathione peroxidase (GPx) activities.

RESULTS

Serum levels of liver enzymes (P < .0001) and MDA (P = .018), as well as erythrocyte SOD activity (P < .0001), were significantly higher in patients with NAFLD compared to healthy controls. Furthermore, patients with NAFLD had significantly lower serum TAC levels compared to healthy controls (P < .0001). No significant differences were observed in serum ox-LDL level and erythrocyte GPx activity between the groups. The probability of being NAFLD increased with increasing serum levels of MDA (P = .020) and SOD activity (P < .0001). In contrast, decreased serum TAC levels predicted the probability of being NAFLD (P < .0001).

CONCLUSIONS

Increased extent of hepatic steatosis could be considered as a pathological mechanism for enhancing oxidative stress in patients with NAFLD, independent of obesity, and is exacerbated further in patients with more severe condition.

12-Lipoxygenase is a Critical Mediator of Type II Pneumocyte Senescence, Macrophage Polarization and Pulmonary Fibrosis after Irradiation

Radiation-induced pulmonary fibrosis (RIPF) is a chronic, progressive complication of therapeutic irradiation of the thorax. It has been suggested that senescence of type II pneumocytes (AECIIs), an alveolar stem cell, plays a role in the development of RIPF through loss of replicative reserve and via senescent AECII-driven release of proinflammatory and profibrotic cytokines. Within this context, we hypothesized that arachidonate 12-lipoxygenase (12-LOX) is a critical mediator of AECII senescence and RIPF. Treatment of wild-type AECIIs with 12S-hydroxyeicosateraenoic acid (12S-HETE), a downstream product of 12-LOX, was sufficient to induce senescence in a NADPH oxidase 4 (NOX4)-dependent manner. Mice deficient in 12-LOX exhibited reduced AECII senescence, pulmonary collagen accumulation and accumulation of alternatively activated (M2) macrophages after thoracic irradiation (5 × 6 Gy) compared to wild-type mice. Conditioned media from irradiated or 12S-HETE-treated primary pneumocytes contained elevated levels of IL-4 and IL-13 compared to untreated pneumocytes. Primary macrophages treated with conditioned media from irradiated AECII demonstrated preferential M2 type polarization when AECIIs were derived from wild-type mice compared to 12-LOX-deficient mice. Together, these data identified 12-LOX as a critical component of RIPF and a therapeutic target for radiation-induced lung injury.

Metabolomics Characterizes the Effects and Mechanisms of Quercetin in Nonalcoholic Fatty Liver Disease Development

As metabolomics is widely used in the study of disease mechanisms, an increasing number of studies have found that metabolites play an important role in the occurrence of diseases. The aim of this study is to investigate the effects and mechanisms of quercetin in high-fat-sucrose diet (HFD)-induced nonalcoholic fatty liver disease (NAFLD) development using nontargeted metabolomics. A rat model of NAFLD was established by feeding with an HFD for 30 and 50 days. The results indicated quercetin exhibited hepatoprotective activity in 30-day HFD-induced NAFLD rats by regulating fatty acid related metabolites (adrenic acid, etc.), inflammation-related metabolites (arachidonic acid, etc.), oxidative stress-related metabolites (2-hydroxybutyric acid) and other differential metabolites (citric acid, etc.). However, quercetin did not improve NAFLD in the 50-day HFD; perhaps quercetin was unable to reverse the inflammation induced by a long-term high-fat diet. These data indicate that dietary quercetin may be beneficial to NAFLD in early stages. Furthermore, combining metabolomics and experimental approaches opens avenues to study the effects and mechanisms of drugs for complex diseases.

Lipid mediators of liver injury in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) comprises a spectrum of histopathological phenotypes ranging from simple steatosis to more severe liver disease associated with cell injury, including nonalcoholic steatohepatitis (NASH), advanced fibrosis, and cirrhosis. Only a subset of patients with NAFLD develop NASH from yet incompletely understood mechanisms. Emerging data suggest lipid species other than triglycerides as contributors to the pathogenesis of NASH. In this mini review, we focus on the recent data on the mechanisms of NASH, focusing on these lipid mediators and their potential as therapeutic targets in NASH.

Hepatocyte ALOXE3 is induced during adaptive fasting and enhances insulin sensitivity by activating hepatic PPARγ

The hepatic glucose fasting response is gaining traction as a therapeutic pathway to enhance hepatic and whole-host metabolism. However, the mechanisms underlying these metabolic effects remain unclear. Here, we demonstrate the epidermal-type lipoxygenase, eLOX3 (encoded by its gene, Aloxe3), is a potentially novel effector of the therapeutic fasting response. We show that Aloxe3 is activated during fasting, glucose withdrawal, or trehalose/trehalose analogue treatment. Hepatocyte-specific Aloxe3 expression reduced weight gain and hepatic steatosis in diet-induced and genetically obese (db/db) mouse models. Aloxe3 expression, moreover, enhanced basal thermogenesis and abrogated insulin resistance in db/db diabetic mice. Targeted metabolomics demonstrated accumulation of the PPARγ ligand 12-KETE in hepatocytes overexpressing Aloxe3. Strikingly, PPARγ inhibition reversed hepatic Aloxe3–mediated insulin sensitization, suppression of hepatocellular ATP production and oxygen consumption, and gene induction of PPARγ coactivator-1α (PGC1α) expression. Moreover, hepatocyte-specific PPARγ deletion reversed the therapeutic effect of hepatic Aloxe3 expression on diet-induced insulin intolerance. Aloxe3 is, therefore, a potentially novel effector of the hepatocellular fasting response that leverages both PPARγ-mediated and pleiotropic effects to augment hepatic and whole-host metabolism, and it is, thus, a promising target to ameliorate metabolic disease.

The lipoxygenase ALOXE3 is an effector of the hepatic fasting response that improves insulin sensitivity by activating hepatic PPARγ.

Comparative Metabolomics Analysis of Cervicitis in Human Patients and a Phenol Mucilage-Induced Rat Model Using Liquid Chromatography Tandem Mass Spectrometry

Cervicitis is an exceedingly common gynecological disorder that puts women at high risk of sexually transmitted infections and induces a series of reproductive system diseases. This condition also has a significant impact on quality of life and is commonly misdiagnosed in clinical practice due to its complicated pathogenesis. In the present study, we performed non-targeted plasma metabolomics analysis of cervicitis in both plasma samples obtained from human patients and plasma samples from a phenol mucilage induced rat model of cervicitis, using ultra-performance liquid chromatography coupled to quadrupole time-of-flight tandem mass spectrometry. In addition to differences in histopathology, we identified differences in the metabolic profile between the cervicitis and control groups using unsupervised principal component analysis and orthogonal projections to latent structures discriminant analysis. These results demonstrated changes in plasma metabolites, with 27 and 22 potential endogenous markers identified in rat and human samples, respectively. The metabolic pathway analysis showed that linoleic acid, arachidonic acid, ether lipid, and glycerophospholipid metabolism are key metabolic pathways involved in cervicitis. This study showed the rat model was successfully created and applied to understand the pathogenesis of cervicitis.