In vivo adenine base editing rescues adrenoleukodystrophy in a humanized mouse model.

X-linked adrenoleukodystrophy (ALD), an inherited neurometabolic disorder caused by mutations in ABCD1, which encodes the peroxisomal ABC transporter, mainly affects the brain, spinal cord, adrenal glands, and testes. In ALD patients, very-long-chain fatty acids (VLCFAs) fail to enter the peroxisome and undergo subsequent ß-oxidation, resulting in their accumulation in the body. It has not been tested whether in vivo base editing or prime editing can be harnessed to ameliorate ALD. We developed a humanized mouse model of ALD by inserting a human cDNA containing the pathogenic variant into the mouse Abcd1 locus. The humanized ALD model showed increased levels of VLCFAs. To correct the mutation, we tested both base editing and prime editing and found that base editing using ABE8e(V106W) could correct the mutation in patient-derived fibroblasts at an efficiency of 7.4%. Adeno-associated virus (AAV)-mediated systemic delivery of NG-ABE8e(V106W) enabled robust correction of the pathogenic variant in the mouse brain (correction efficiency: ∼5.5%), spinal cord (∼5.1%), and adrenal gland (∼2%), leading to a significant reduction in the plasma levels of C26:0/C22:0. This established humanized mouse model and the successful correction of the pathogenic variant using a base editor serve as a significant step toward treating human ALD disease.

Metabolomic pathways in food allergy.

Food allergy (FA) is a widespread issue, affecting as many as 10% of the population. Over the past two to three decades, the prevalence of FA has been on the rise, particularly in industrialized and westernized countries. FA is a complex, multifactorial disease mediated by type 2 immune responses and involving environmental and genetic factors. However, the precise mechanisms remain inadequately understood. Metabolomics has the potential to identify disease endotypes, which could beneficially promote personalized prevention and treatment. A metabolome approach would facilitate the identification of surrogate metabolite markers reflecting the disease activity and prognosis. Here, we present a literature overview of recent metabolomic studies conducted on children with FA.

Gut microbiota composition and metabolite profiling in smokers: a comparative study between emphysema and asymptomatic individuals with therapeutic implications.

BACKGROUND: Diet has a crucial role in the gut microbiota, and dysbiosis in the gut and lungs has been suggested to be associated with chronic obstructive pulmonary disease. We compared the diet, microbiome and metabolome between asymptomatic smokers and those with emphysema. METHODS: We enrolled 10 asymptomatic smokers with preserved lung function and 16 smokers with emphysema with severe airflow limitation. Dietary intake information was gathered by a self-reported questionnaire. Sputum and faecal samples were collected for microbial and metabolomics analysis. A murine model of emphysema was used to determine the effect of metabolite supplementation. RESULTS: Despite having a similar smoking history with emphysema patients, asymptomatic smokers had higher values of body mass index, fibre intake and faecal acetate level. Linear discriminant analysis identified 17 microbial taxonomic members that were relatively enriched in the faeces of asymptomatic smokers. Analysis of similarity results showed dissimilarity between the two groups (r=0.287, p=0.003). Higher acetate level was positively associated with forced expiratory volume in one second in the emphysema group (r=0.628, p=0.012). Asymptomatic smokers had a greater number of species associated with acetate and propionate (r>0.6) than did those with emphysema (30 vs 19). In an emphysema mouse model, supplementation of acetate and propionate reduced alveolar destruction and the production of proinflammatory cytokines, and propionate decreased the CD3+CD4+IL-17+ T-cell population in the lung and spleen. CONCLUSION: Smokers with emphysema showed differences in diet, microbiome and short-chain fatty acids compared with asymptomatic smokers. Acetate and propionate showed therapeutic effects in a smoking-induced murine model of emphysema.

The alternative bile acid pathway can predict food allergy persistence in early childhood.

BACKGROUND: Mechanisms underlying persistent food allergy (FA) are not well elucidated. The intestinal mucosa is the primary exposure route of food allergens. However, no study has examined intestinal metabolites associated with FA persistence. The goal of this study was to investigate intestinal metabolites and associated microbiomes in early life that aid in determining the development and persistence of FA. METHODS: We identified metabolomic alterations in the stool of infants according to FA by mass spectrometry-based untargeted metabolome profiling. The targeted metabolomic analysis of bile acid metabolites and stool microbiome was performed. Bile acid metabolite composition in infancy was evaluated by characterizing the subjects at the age of 3 into FA remission and persistent FA. RESULTS: In untargeted metabolomics, primary bile acid biosynthesis was significantly different between subjects with FA and healthy controls. In targeted metabolomics for bile acids, intestinal bile acid metabolites synthesized by the alternative pathway were reduced in infants with FA than those in healthy controls. Subjects with persistent FA were also distinguished from healthy controls and those with FA remission by bile acid metabolites of the alternative pathway. These metabolites were negatively correlated with specific IgE levels in egg white. The abundance of intestinal Clostridia was decreased in the FA group and was correlated with ursodeoxycholic acid. CONCLUSION: Intestinal bile acid metabolites of the alternative pathway could be predictive biomarkers for persistent FA in early childhood. These findings require replication in future studies.

A targeted metabolomics approach for sepsis-induced ARDS and its subphenotypes.

BACKGROUND: Acute respiratory distress syndrome (ARDS) is etiologically and clinically a heterogeneous disease. Its diagnostic characteristics and subtype classification, and the application of these features to treatment, have been of considerable interest. Metabolomics is becoming important for identifying ARDS biology and distinguishing its subtypes. This study aimed to identify metabolites that could distinguish sepsis-induced ARDS patients from non-ARDS controls, using a targeted metabolomics approach, and to identify whether sepsis-induced direct and sepsis-induced indirect ARDS are metabolically distinct groups, and if so, confirm their metabolites and associated pathways. METHODS: This study retrospectively analyzed 54 samples of ARDS patients from a sepsis registry that was prospectively collected from March 2011 to February 2018, along with 30 non-ARDS controls. The cohort was divided into direct and indirect ARDS. Metabolite concentrations of five analyte classes (energy metabolism, free fatty acids, amino acids, phospholipids, sphingolipids) were measured using liquid chromatography-tandem mass spectrometry and gas chromatography-mass spectrometry by targeted metabolomics. RESULTS: In total, 186 metabolites were detected. Among them, 102 metabolites could differentiate sepsis-induced ARDS patients from the non-ARDS controls, while 14 metabolites could discriminate sepsis-induced ARDS subphenotypes. Using partial least-squares discriminant analysis, we showed that sepsis-induced ARDS patients were metabolically distinct from the non-ARDS controls. The main distinguishing metabolites were lysophosphatidylethanolamine (lysoPE) plasmalogen, PE plasmalogens, and phosphatidylcholines (PCs). Sepsis-induced direct and indirect ARDS were also metabolically distinct subgroups, with differences in lysoPCs. Glycerophospholipid and sphingolipid metabolism were the most significant metabolic pathways involved in sepsis-induced ARDS biology and in sepsis-induced direct/indirect ARDS, respectively. CONCLUSION: Our study demonstrated a marked difference in metabolic patterns between sepsis-induced ARDS patients and non-ARDS controls, and between sepsis-induced direct and indirect ARDS subpheonotypes. The identified metabolites and pathways can provide clues relevant to the diagnosis and treatment of individuals with ARDS.

Lipid signatures reflect the function of the murine primary placentation†.

The placenta regulates maternal-fetal communication, and its defect leads to significant pregnancy complications. The maternal and embryonic circulations are primitively connected in early placentation, but the function of the placenta during this developmentally essential period is relatively unknown. We thus performed a comparative proteomic analysis of the placenta before and after primary placentation and found that the metabolism and transport of lipids were characteristically activated in this period. The placental fatty acid (FA) carriers in specific placental compartments were upregulated according to gestational age, and metabolomic analysis also showed that the placental transport of FAs increased in a time-dependent manner. Further analysis of two mutant mice models with embryonic lethality revealed that lipid-related signatures could reflect the functional state of the placenta. Our findings highlight the importance of the nutrient transport function of the primary placenta in the early gestational period and the role of lipids in embryonic development. SUMMARY SENTENCE: The placenta is activated characteristically in terms of lipid transport during primary placentation, and the lipid-related signatures closely reflect the functional state of the placenta.

Down-regulated surfactant protein B in obese asthmatics.

BACKGROUND: Obesity is a common comorbid condition in adult asthmatics and known as a feature of asthma severity. However, the molecular mechanism under obesity-induced inflammation has not yet been fully understood. OBJECTIVE: Considering the essential role of hydrophobic surfactant protein B (SP-B) in lung function, SP-B was targeted to examine its involvement in the development of obesity-induced airway inflammation in asthmatics. METHODS: The aim was to examine an alteration in circulating SP-B according to obesity in adult asthmatics, 129 asthmatics were enrolled and classified into 3 groups (obese, overweight and normal-weight groups) according to body mass index (BMI). Circulating SP-B levels were determined by enzyme-linked immunosorbent assay. Four single nucleotide polymorphisms of SFTPB gene were genotyped. Serum ceramide levels were measured by liquid chromatography-tandem mass spectrometry. RESULTS: Significantly lower serum SP-B levels were noted in the obese group than in the overweight or normal-weight group (p = .002). The serum SP-B level was significantly correlated with serum levels of C18:0 ceramide and transforming growth factor beta 1 as well as BMI (r = -0.200; r = -0.215; r = -0.332, p < .050 for all). An inverse correlation was noted between serum SP-B and fractional exhaled nitric oxide levels in female asthmatics (r = -0.287, p = .009). Genetic predisposition of the SFTPB gene at 9306 A>G to the obese and overweight groups was noted. CONCLUSION: Obesity altered ceramide metabolism leading to pulmonary surfactant dysfunction and impaired resolution of airway inflammation, finally contributing to the phenotypes of obese asthmatics.

Sphingomyelin synthase 1 mediates hepatocyte pyroptosis to trigger non-alcoholic steatohepatitis.

OBJECTIVE: Lipotoxic hepatocyte injury is a primary event in non-alcoholic steatohepatitis (NASH), but the mechanisms of lipotoxicity are not fully defined. Sphingolipids and free cholesterol (FC) mediate hepatocyte injury, but their link in NASH has not been explored. We examined the role of free cholesterol and sphingomyelin synthases (SMSs) that generate sphingomyelin (SM) and diacylglycerol (DAG) in hepatocyte pyroptosis, a specific form of programmed cell death associated with inflammasome activation, and NASH. DESIGN: Wild-type C57BL/6J mice were fed a high fat and high cholesterol diet (HFHCD) to induce NASH. Hepatic SMS1 and SMS2 expressions were examined in various mouse models including HFHCD-fed mice and patients with NASH. Pyroptosis was estimated by the generation of the gasdermin-D N-terminal fragment. NASH susceptibility and pyroptosis were examined following knockdown of SMS1, protein kinase Cδ (PKCδ), or the NLR family CARD domain-containing protein 4 (NLRC4). RESULTS: HFHCD increased the hepatic levels of SM and DAG while decreasing the level of phosphatidylcholine. Hepatic expression of Sms1 but not Sms2 was higher in mouse models and patients with NASH. FC in hepatocytes induced Sms1 expression, and Sms1 knockdown prevented HFHCD-induced NASH. DAG produced by SMS1 activated PKCδ and NLRC4 inflammasome to induce hepatocyte pyroptosis. Depletion of Nlrc4 prevented hepatocyte pyroptosis and the development of NASH. Conditioned media from pyroptotic hepatocytes activated the NOD-like receptor family pyrin domain containing 3 inflammasome (NLRP3) in Kupffer cells, but Nlrp3 knockout mice were not protected against HFHCD-induced hepatocyte pyroptosis. CONCLUSION: SMS1 mediates hepatocyte pyroptosis through a novel DAG-PKCδ-NLRC4 axis and holds promise as a therapeutic target for NASH.

Treatment of chemotherapy-induced cachexia with BST204: a multimodal validation study.

INTRODUCTION: Chemotherapy is a major etiology of cachexia. Ginseng products are known to have various anti-cachectic and health-promoting effects, such as inhibiting inflammation and promoting energy production. In particular, BST204, purified ginseng dry extract, contains multiple ginsenosides that can reduce chemotherapy-related fatigue and toxicity. OBJECTIVES: To investigate the effects of BST204 on the alleviation of chemotherapy-induced cachexia using a multimodal approach. METHODS: In a CT26 mouse syngeneic colon cancer model, cachexia was predominantly induced by chemotherapy with 5-fluorouracil (5-FU) than by tumor growth. BST204 at a dose of 100 or 200 mg/kg was administered to 5-FU-treated mice. RESULTS: BST204 significantly mitigated the decrease in tumor-excluded body weight (change in 5-FU group and BST204 groups: - 13% vs. - 6% on day 7; - 30% vs. - 20% on day 11), muscle volume (- 19% vs. - 11%), and fat volume (- 91% vs. - 56%). The anti-cachectic effect of BST204 was histologically demonstrated by an improved balance between muscle regeneration and degeneration and a decrease in muscle cross-sectional area reduction. CONCLUSION: Chemotherapy-induced cachexia was biochemically and metabolically characterized by activated inflammation, enhanced oxidative stress, increased protein degradation, decreased protein stabilization, reduced glucose-mediated energy production, and deactivated glucose-mediated biosynthesis. These adverse effects were significantly improved by BST204 treatment. Overall, our multimodal study demonstrated that BST204 could effectively alleviate chemotherapy-induced cachexia.

Stearic acid attenuates profibrotic signalling in idiopathic pulmonary fibrosis.

BACKGROUND AND OBJECTIVE: Lipid metabolism dysregulation has been implicated in the pathogenesis of IPF; however, the roles of most lipid metabolites in lung fibrosis remain unexplored. Therefore, we aimed to identify changes in lipid metabolites in the lung tissues of IPF patients and determine their roles in pulmonary fibrosis. METHODS: Free fatty acids in the lung tissues of IPF patients and controls were quantified using a metabolomic approach. The roles of free fatty acids in fibroblasts or epithelial cells treated with TGF-ß1 were evaluated using fibrotic markers. The antifibrotic role of stearic acid was also assessed in a bleomycin-induced lung fibrosis mouse model. Protein levels in cell lysates or tissues were measured by western blotting. RESULTS: The levels of stearic acid were lower in IPF lung tissues than in control lung tissues. Stearic acid significantly reduced TGF-ß1-induced α-SMA and collagen type 1 expression in MRC-5 cells. Furthermore, stearic acid decreased the levels of p-Smad2/3 and ROS in MRC-5 cells treated with TGF-ß1 and disrupted TGF-ß1-induced EMT in Beas-2B cells. Stearic acid reduced the levels of bleomycin-induced hydroxyproline in a mouse model. CONCLUSION: Changes in the free fatty acid profile, including low levels of stearic acid, were observed in IPF patients. Stearic acid may exert antifibrotic activity by regulating profibrotic signalling.

Mass Spectrometry-based Metabolomics in Translational Research.

Metabolomics is the systematic study of metabolite profiles of complex biological systems, and involves the systematic identification and quantification of metabolites. Metabolism is integrated with all biochemical reactions in biological systems; thus metabolite profiles provide collective information on biochemical processes induced by genetic or environmental perturbations. Transcriptomes or proteomes may not be functionally active and not always reflect phenotypic variations. The metabolome, however, consists of the biomolecules closest to the phenotype of living organisms, and is often called the molecular phenotype of biological systems. Thus, metabolome alterations can easily result in disease states, providing important clues to understand pathophysiological mechanisms contributing to various biomedical symptoms. The metabolome and metabolomics have been emphasized in translational research related to biomarker discovery, drug target discovery, drug responses, and disease mechanisms. This review describes the basic concepts, workflows, and applications of mass spectrometry-based metabolomics in translational research.

An RNA-binding-protein, NONO governs energy metabolism by regulating NAMPT in lung cancer.

The RNA binding proteins (RBPs) have multiple roles in human cancer. However, their molecular target and function have not been clearly identified. Our genomic analysis derived from patients reveals that NONO is a potential oncogenic gene in lung cancer. NONO is highly expressed in lung cancer tissues compared with normal tissues, and its expression has been correlated with the prognosis of lung cancer patients. We found that NONO significantly influences cancer cell proliferation in lung cancer. Gene expression profiles with NONO-depleted cells revealed that the sirtuin signaling pathway is highly correlated with NONO. Thus, NONO-silenced cells caused reduction of the TCA cycle and glycolysis metabolism. We identified that NONO regulated NAMPT, which is a well-known gene involved in sirtuin signaling, and NONO has a significant correlation with NAMPT in lung cancer patients. We propose that NONO modulates energy metabolism by direct interaction with NAMPT and suggest that a functional relationship between NONO and NAMPT contributes to lung cancer cell survival. Targeting the axis can be a promising approach for patient treatment in lung cancer.

Metabolic shift favoring C18:0 ceramide accumulation in obese asthma.

BACKGROUND: Obesity associated with various complications has increased worldwide. Body weight gain alters lipid metabolites (especially sphingolipids) contributing to obesity-induced inflammation. However, the significance of the metabolites in the development of obese asthma is not yet clear. METHODS: The serum levels of sphingolipids were measured using liquid chromatography-tandem mass spectrometry in obese controls (n = 7) and patients with asthma: the obese group (BMI > 25 kg/m2 , n = 13) vs the nonobese (n = 28) group. To examine the relationship between metabolic changes in sphingolipids and macrophage polarization, public microarray data were analyzed. In addition, the alteration in sphingolipid metabolism was investigated in wild-type BALB/c mice fed a high-fat diet. RESULTS: The obese asthma had higher levels of serum C18:0 and C20:0 ceramides than the nonobese asthma group (P = .028 and P = .040, respectively). The value of the serum C18:0 ceramide (184.3 ng/mL) for discriminating the obese asthma from the nonobese asthma group showed 53.9% sensitivity and 85.7% specificity (AUC = 0.721, P = .024). The microarray data showed significantly increased ceramide synthesis and metabolic shift to ceramide accumulation during M1 macrophage polarization in humans. Increased airway hyperresponsiveness, M1 macrophage polarization, and C18:0 ceramide levels were noted in obese mice, but not in nonobese mice. Increased expression of ceramide synthase (CerS) 1 and CerS6 (not CerS2) was noted in lung tissues of obese mice. CONCLUSION: Alteration in sphingolipid metabolism favoring ceramide accumulation (especially long-chain ceramides) may contribute to developing obese asthma.

Ceramide/sphingosine-1-phosphate imbalance is associated with distinct inflammatory phenotypes of uncontrolled asthma.

BACKGROUND: Asthma is associated with inflammatory dysregulation, but the underlying metabolic signatures are unclear. This study aimed to classify asthma inflammatory phenotypes based on cellular and metabolic features. METHODS: To determine cellular and metabolic profiles, we assessed inflammatory cell markers using flow cytometry, sphingolipid (SL) metabolites using LC-MS/MS, and serum cytokines using ELISA. Targeted gene polymorphisms were determined to identify genetic predispositions related to the asthma inflammatory phenotype. RESULTS: In total, 137 patients with asthma and 20 healthy controls (HCs) were enrolled. Distinct cellular and metabolic profiles were found between them; patients with asthma showed increased expressions of inflammatory cell markers and higher levels of SL metabolites compared to HCs (P < .05 for all). Cellular markers (CD66+ neutrophils, platelet-adherent eosinophils) and SL metabolic markers (C16:0 and C24:0 ceramides) for uncontrolled asthma were also identified; higher levels were observed in uncontrolled asthma compared to controlled asthma (P < .05 for all). Asthmatics patients with higher levels of CD66+ neutrophils had lower FEV1(%), higher ACQ (but lower AQLO) scores, and higher sphingosine and C16:0 ceramide levels compared to those with low levels of CD66+ neutrophils. Asthmatics patients with higher levels of platelet-adherent eosinophils had higher S1P levels compared to those with lower levels of platelet-adherent eosinophils. Patients carrying TT genotype of ORMDL3 had more CD66+ neutrophils; those with AG/ GG genotypes of SGMS1 exhibited higher platelet-adherent eosinophils. CONCLUSION: Patients with uncontrolled asthma possess distinct inflammatory phenotypes including increased CD66+ neutrophils and platelet-adherent eosinophils, with an imbalanced ceramide/S1P rheostat, potentially involving ORMDL3 and SGMS1 gene polymorphisms. Ceramide/S1P synthesis could be targeted to control airway inflammation.

Perilipin 1 (Plin1) deficiency promotes inflammatory responses in lean adipose tissue through lipid dysregulation.

Lipid droplets are specialized cellular organelles that contain neutral lipid metabolites and play dynamic roles in energy homeostasis. Perilipin 1 (Plin1), one of the major lipid droplet-binding proteins, is highly expressed in adipocytes. In mice, Plin1 deficiency impairs peripheral insulin sensitivity, accompanied with reduced fat mass. However, the mechanisms underlying insulin resistance in lean Plin1 knockout (Plin1-/-) mice are largely unknown. The current study demonstrates that Plin1 deficiency promotes inflammatory responses and lipolysis in adipose tissue, resulting in insulin resistance. M1-type adipose tissue macrophages (ATMs) were higher in Plin1-/- than in Plin1+/+ mice on normal chow diet. Moreover, using lipidomics analysis, we discovered that Plin1-/- adipocytes promoted secretion of pro-inflammatory lipid metabolites such as prostaglandins, which potentiated monocyte migration. In lean Plin1-/- mice, insulin resistance was relieved by macrophage depletion with clodronate, implying that elevated pro-inflammatory ATMs might be attributable for insulin resistance under Plin1 deficiency. Together, these data suggest that Plin1 is required to restrain fat loss and pro-inflammatory responses in adipose tissue by reducing futile lipolysis to maintain metabolic homeostasis.

V232M substitution restricts a distinct O-glycosylation of PLD3 and its neuroprotective function.

The link between Val232Met variant of phospholipase D3 (PLD3) and late-onset Alzheimer's disease (AD) is still obscure. While it may not affect directly the amyloid precursor protein function, PLD3 could be regulating multiple cellular compartments. Here, we investigated the function of wild-type human PLD3 (PLD3WT) and the Val232Met variant (PLD3VM) in the presence of ß-amyloid (Aß) in a Drosophila melanogaster model of AD. We expressed PLD3WT in CNS of the Aß-model flies and monitored its effect on the ER stress, cell apoptosis and recovery the Aß-induced cognitive impairment. The expression reduced ER stress and neuronal apoptosis, which resulted in normalized antioxidative phospholipids levels and brain protection. A specific O-glycosylation at pT271 in PLD3 is essential for its normal trafficking and cellular localization. The V232 M substitution impairs this O-glycosylation, leading to enlarged lysosomes and plausibly aberrant protein recycling. PLD3VM was less neuroprotective, and while, PLD3WT expression enhances the lysosomal functions, V232 M attenuated PLD3's trafficking to the lysosomes. Thus, the V232 M mutation may affect AD pathogenesis. Further understanding of the mechanistic role of PLD3 in AD could lead to developing novel therapeutic agents.

Generation of expandable human pluripotent stem cell-derived hepatocyte-like liver organoids.

BACKGROUND & AIMS: The development of hepatic models capable of long-term expansion with competent liver functionality is technically challenging in a personalized setting. Stem cell-based organoid technologies can provide an alternative source of patient-derived primary hepatocytes. However, self-renewing and functionally competent human pluripotent stem cell (PSC)-derived hepatic organoids have not been developed. METHODS: We developed a novel method to efficiently and reproducibly generate functionally mature human hepatic organoids derived from PSCs, including human embryonic stem cells and induced PSCs. The maturity of the organoids was validated by a detailed transcriptome analysis and functional performance assays. The organoids were applied to screening platforms for the prediction of toxicity and the evaluation of drugs that target hepatic steatosis through real-time monitoring of cellular bioenergetics and high-content analyses. RESULTS: Our organoids were morphologically indistinguishable from adult liver tissue-derived epithelial organoids and exhibited self-renewal. With further maturation, their molecular features approximated those of liver tissue, although these features were lacking in 2D differentiated hepatocytes. Our organoids preserved mature liver properties, including serum protein production, drug metabolism and detoxifying functions, active mitochondrial bioenergetics, and regenerative and inflammatory responses. The organoids exhibited significant toxic responses to clinically relevant concentrations of drugs that had been withdrawn from the market due to hepatotoxicity and recapitulated human disease phenotypes such as hepatic steatosis. CONCLUSIONS: Our organoids exhibit self-renewal (expandable and further able to differentiate) while maintaining their mature hepatic characteristics over long-term culture. These organoids may provide a versatile and valuable platform for physiologically and pathologically relevant hepatic models in the context of personalized medicine. LAY SUMMARY: A functionally mature, human cell-based liver model exhibiting human responses in toxicity prediction and drug evaluation is urgently needed for pre-clinical drug development. Here, we develop a novel human pluripotent stem cell-derived hepatocyte-like liver organoid that is critically advanced in terms of its generation method, functional performance, and application technologies. Our organoids can contribute to the better understanding of liver development and regeneration, and provide insights for metabolic studies and disease modeling, as well as toxicity assessments and drug screening for personalized medicine.

Protective role of endogenous plasmalogens against hepatic steatosis and steatohepatitis in mice.

Free cholesterol (FC) accumulation in the liver is an important pathogenic mechanism of nonalcoholic steatohepatitis (NASH). Plasmalogens, key structural components of the cell membrane, act as endogenous antioxidants and are primarily synthesized in the liver. However, the role of hepatic plasmalogens in metabolic liver disease is unclear. In this study, we found that hepatic levels of docosahexaenoic acid (DHA)-containing plasmalogens, expression of glyceronephosphate O-acyltransferase (Gnpat; the rate-limiting enzyme in plasmalogen biosynthesis), and expression of Pparα were lower in mice with NASH caused by accumulation of FC in the liver. Cyclodextrin-induced depletion of FC transactivated Δ-6 desaturase by increasing sterol regulatory element-binding protein 2 expression in cultured hepatocytes. DHA, the major product of Δ-6 desaturase activation, activated GNPAT, thereby explaining the association between high hepatic FC and decreased Gnpat expression. Gnpat small interfering RNA treatment significantly decreased peroxisome proliferator-activated receptor α (Pparα) expression in cultured hepatocytes. In addition to GNPAT, DHA activated PPARα and increased expression of Pparα and its target genes, suggesting that DHA in the DHA-containing plasmalogens contributed to activation of PPARα. Accordingly, administration of the plasmalogen precursor, alkyl glycerol (AG), prevented hepatic steatosis and NASH through a PPARα-dependent increase in fatty acid oxidation. Gnpat+/- mice were more susceptible to hepatic lipid accumulation and less responsive to the preventive effect of fluvastatin on NASH development, suggesting that endogenous plasmalogens prevent hepatic steatosis and NASH. CONCLUSION: Increased hepatic FC in animals with NASH decreased plasmalogens, thereby sensitizing animals to hepatocyte injury and NASH. Our findings uncover a novel link between hepatic FC and plasmalogen homeostasis through GNPAT regulation. Further study of AG or other agents that increase hepatic plasmalogen levels may identify novel therapeutic strategies against NASH. (Hepatology 2017;66:416-431).

Meal-related oscillations in the serum serotonin levels in healthy young men.

CONTEXT: Serotonin acts as a neurotransmitter in the central and enteric nervous systems, modulating psychological, metabolic and gastrointestinal functions. Serotonin is also found in the serum or plasma, indicating its potential role as a hormone. OBJECTIVE: We aimed to assess the 24-hour diurnal profile of serum serotonin in relation to meal ingestion in healthy adult men. METHODS: Ten healthy (5 lean and 5 obese) male subjects were enrolled in this study. Blood samples were drawn every 30-60 minutes throughout a 24-hour period to determine the serotonin levels. Three meals were provided on a fixed schedule. To confirm the effect of meal intake on serum serotonin levels, 4 subjects underwent fasting until 1500 h and were then provided a meal without notice. RESULTS: Serum serotonin levels had distinct diurnal variations, with the highest levels early in the morning and the lowest levels in the midafternoon and during sleep. Notably, these diurnal oscillations were markedly reduced in obese subjects. Fluctuations in serum serotonin levels were associated with meal intake, and the levels peaked 30 minutes before meals and exhibited a trough during the postprandial period. Fasting blunted the meal-related oscillations in serum serotonin levels. Moreover, unexpected meal intake did not lead to a premeal increase in serum serotonin levels. CONCLUSIONS: Serum serotonin levels displayed meal-related diurnal oscillations, which were disrupted by fasting and obesity. These findings suggest the possibility that circulating serotonin modulates metabolic function in humans.

Fecal Fatty Acid Profiling as a Potential New Screening Biomarker in Patients with Colorectal Cancer.

BACKGROUND: The fatty acid profile of the fecal metabolome and its association with colorectal cancer (CRC) has not been fully evaluated. AIMS: We aimed to compare the fecal fatty acid profiles of CRC patients and healthy controls. METHODS: We enrolled 26 newly diagnosed CRC patients and 28 healthy individuals between July 2014 and August 2014 from our institute. Long- and short-chain fatty acids were extracted from fecal samples and analyzed using gas chromatography-mass spectrometry. RESULTS: Regarding fecal long-chain fatty acids, the levels of total ω-6 polyunsaturated fatty acids and, particularly, of linoleic acid (C18:2ω-6) were significantly higher in male CRC patients than in healthy men (2.750 ± 2.583 vs. 1.254 ± 0.966 µg/mg feces, P = 0.040; 2.670 ± 2.507 vs. 1.226 ± 0.940 µg/mg feces, P = 0.034, respectively). In addition, the levels of total monounsaturated fatty acid and, particularly, of oleic acid (C18:1ω-9) were significantly higher in male CRC patients than in healthy men (1.802 ± 1.331 vs. 0.977 ± 0.625 µg/mg feces, P = 0.027; 1.749 ± 1.320 vs. 0.932 ± 0.626 µg/mg feces, P = 0.011, respectively). However, those differences were not shown in female gender. The level of fecal short-chain fatty acids was not different between CRC patients and healthy controls. CONCLUSIONS: There were changes in the profiles of fecal fatty acid metabolomes in CRC patients compared to healthy controls, implying that fecal fatty acids could be used as a novel screening tool for CRC.