Lysophospholipid acyltransferases and eicosanoid biosynthesis in zebrafish myeloid cells

Membrane-bound O-acyltransferase 7 (MBOAT7) shapes lysosomal lipid homeostasis and function to control alcohol-associated liver injury

Recent genome-wide association studies (GWAS) have identified a link between single-nucleotide polymorphisms (SNPs) near the MBOAT7 gene and advanced liver diseases. Specifically, the common MBOAT7 variant (rs641738) associated with reduced MBOAT7 expression is implicated in non-alcoholic fatty liver disease (NAFLD), alcohol-associated liver disease (ALD), and liver fibrosis. However, the precise mechanism underlying MBOAT7-driven liver disease progression remains elusive. Previously, we identified MBOAT7-driven acylation of lysophosphatidylinositol lipids as key mechanism suppressing the progression of NAFLD (Gwag et al., 2019). Here, we show that MBOAT7 loss of function promotes ALD via reorganization of lysosomal lipid homeostasis. Circulating levels of MBOAT7 metabolic products are significantly reduced in heavy drinkers compared to healthy controls. Hepatocyte- (Mboat7-HSKO), but not myeloid-specific (Mboat7-MSKO), deletion of Mboat7 exacerbates ethanol-induced liver injury. Lipidomic profiling reveals a reorganization of the hepatic lipidome in Mboat7-HSKO mice, characterized by increased endosomal/lysosomal lipids. Ethanol-exposed Mboat7-HSKO mice exhibit dysregulated autophagic flux and lysosomal biogenesis, associated with impaired transcription factor EB-mediated lysosomal biogenesis and autophagosome accumulation. This study provides mechanistic insights into how MBOAT7 influences ALD progression through dysregulation of lysosomal biogenesis and autophagic flux, highlighting hepatocyte-specific MBOAT7 loss as a key driver of ethanol-induced liver injury.

Association of GCKR and MBOAT7 genetic polymorphisms with non-alcoholic fatty liver disease

Aim of the study

Non-alcoholic fatty liver disease (NAFLD) is one of the most important causes of chronic liver disease (CLD) in both Western and Asian populations. There is wide inter-individual variability in the occurrence of NAFLD and progression to non-alcoholic steatohepatitis (NASH) even after correcting environmental factors, and its true explanation can be provided by heritability. Two such genetic variations, the glucokinase regulator (GCKR) and membrane bound O-acyltransferase domain containing 7 (MBOAT7) genes, in NAFLD patients were studied in the Indian population.

Material and methods

A cross sectional analytical study was conducted in the Department of Gastroenterology at a tertiary care centre. In total 100 subjects in the age range of 18-65 years were included in the study; 50 were patients with NAFLD including fatty liver, NASH and NASH related cirrhosis, and 50 were healthy subjects (No NAFLD). The polymorphisms rs780094 and rs1260326 for GCKR and rs641738 for MBOAT7 were determined using PCR followed by the PCR-RFLP.

Results

GCKR rs780094 minor allele A was more common in NAFLD patients (p = 0.00001). Within the spectrum of NAFLD, the A allele was present frequently among cirrhotics as compared to NASH and fatty liver (p = 0.00001). Morbidly obese individuals showed significant association with the homozygous A allele (p = 0.028). These results were not seen with GCKR rs1260326 across all alleles. In MBOAT7 (rs641738) the frequency of the minor allele T for NAFLD was 84% vs. 80% in healthy subjects (p = 0.79). The association of the T allele among the spectrum of NAFLD was not statistically significant (p = 0.79).

Conclusions

GCKR genetic variant rs780094 was found to be significantly associated with NAFLD. The MBOAT7 (rs641738) genetic variant was not found to be significantly associated with NAFLD.

MBOAT7 expression is associated with disease progression in COVID-19 patients

BACKGROUND AND AIM

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in late 2019 caused a pandemic of acute respiratory disease, named coronavirus disease 2019 (COVID-19). COVID-19 became one of the most challenging health emergencies, hence the necessity to find different prognostic factors for disease progression, and severity. Membrane bound O-acyltransferase domain containing 7 (MBOAT7) demonstrates anti-inflammatory effects through acting as a fine-tune regulator of the amount of cellular free arachidonic acid. We aimed in this study to evaluate MBOAT7 expression in COVID-19 patients and to correlate it with disease severity and outcomes.

METHODS

This case-control study included 56 patients with confirmed SARS-CoV-2 diagnosis and 28 control subjects. Patients were further classified into moderate (n = 28) and severe (n = 28) cases. MBOAT7, tumor necrosis factor-α (TNF-α), and interleukin-1ß (IL-1ß) mRNA levels were evaluated in peripheral blood mononuclear cells (PBMC) samples isolated from patients and control subjects by real time quantitative polymerase chain reaction (RT-qPCR). In addition, circulating MBOAT7 protein levels were assayed by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Significant lower levels of circulating MBOAT7 mRNA and protein were observed in COVID-19 patients compared to control subjects with severe COVID-19 cases showing significant lower levels compared to moderate cases. Moreover, severe cases showed a significant upregulation of TNF-α and IL-1ß mRNA. MBOAT7 mRNA and protein levels were significantly correlated with inflammatory markers (TNF-α, IL-1ß, C-reactive protein (CRP), and ferritin), liver enzymes, severity, and oxygen saturation levels.

CONCLUSION

COVID-19 is associated with downregulation of MBAOT7, which correlates with disease severity.

MBOAT7 in liver and extrahepatic diseases

MBOAT7 is a protein anchored to endomembranes by several transmembrane domains. It has a catalytic dyad involved in remodelling of phosphatidylinositol with polyunsaturated fatty acids. Genetic variants in the MBOAT7 gene have been associated with the entire spectrum of non-alcoholic fatty liver (NAFLD), recently redefined as metabolic dysfunction-associated fatty liver disease (MAFLD) and, lately, steatotic liver disease (SLD), and to an increasing number of extrahepatic conditions. In this review, we will (a) elucidate the molecular mechanisms by which MBOAT7 loss-of-function predisposes to MAFLD and neurodevelopmental disorders and (b) discuss the growing number of genetic studies linking MBOAT7 to hepatic and extrahepatic diseases. MBOAT7 complete loss of function causes severe changes in brain development resulting in several neurological manifestations. Lower MBOAT7 hepatic expression at both the mRNA and protein levels, due to missense nucleotide polymorphisms (SNPs) in the locus containing the MBOAT7 gene, affects specifically metabolic and viral diseases in the liver from simple steatosis to hepatocellular carcinoma, and potentially COVID-19 disease. This body of evidence shows that phosphatidylinositol remodelling is a key factor for human health.

MBOAT7-driven lysophosphatidylinositol acylation in adipocytes contributes to systemic glucose homeostasis

We previously demonstrated that antisense oligonucleotide-mediated knockdown of Mboat7, the gene encoding membrane bound O-acyltransferase 7, in the liver and adipose tissue of mice promoted high fat diet-induced hepatic steatosis, hyperinsulinemia, and systemic insulin resistance. Thereafter, other groups showed that hepatocyte-specific genetic deletion of Mboat7 promoted striking fatty liver and NAFLD progression in mice but does not alter insulin sensitivity, suggesting the potential for cell autonomous roles. Here, we show that MBOAT7 function in adipocytes contributes to diet-induced metabolic disturbances including hyperinsulinemia and systemic insulin resistance. We generated Mboat7 floxed mice and created hepatocyte- and adipocyte-specific Mboat7 knockout mice using Cre-recombinase mice under the control of the albumin and adiponectin promoter, respectively. Here, we show that MBOAT7 function in adipocytes contributes to diet-induced metabolic disturbances including hyperinsulinemia and systemic insulin resistance. The expression of Mboat7 in white adipose tissue closely correlates with diet-induced obesity across a panel of ∼100 inbred strains of mice fed a high fat/high sucrose diet. Moreover, we found that adipocyte-specific genetic deletion of Mboat7 is sufficient to promote hyperinsulinemia, systemic insulin resistance, and mild fatty liver. Unlike in the liver, where Mboat7 plays a relatively minor role in maintaining arachidonic acid-containing PI pools, Mboat7 is the major source of arachidonic acid-containing PI pools in adipose tissue. Our data demonstrate that MBOAT7 is a critical regulator of adipose tissue PI homeostasis, and adipocyte MBOAT7-driven PI biosynthesis is closely linked to hyperinsulinemia and insulin resistance in mice.

A novel cadmium detoxification pathway in Tri-spine horseshoe crab (Tachypleus tridentatus): A 430-million-years-ago organism

Marine and intertidal heavy metal pollution has been a major concern in recent years. Tachypleus tridentatus has existed on earth for more than 430 million years. It has suffered a sharp decline in population numbers caused by environmental pollution and anthropogenic disturbance for almost 40 years. However, the effects of heavy metal pollution on juvenile T. tridentatus have not been reported. Here we show the mechanism of cadmium (Cd) detoxification in juvenile T. tridentatus using integrated antioxidant indexes and transcriptomic and metabolomic analysis. High Cd²⁺ concentration caused oxidative stress in juvenile T. tridentatus. The hazards increase with increasing Cd²⁺ concentration in juvenile T. tridentatus. Transcriptomics and metabolomics analyses concluded that high Cd²⁺ concentration resulted in the imbalance of glycerophospholipid metabolism in juvenile T. tridentatus to detoxify Cd. Our results offer a rationale for protective measures and further studies of heavy metal stress in T. tridentatus.

Untargeted Metabolomics Reveals Lipid Impairment in the Liver of Adult Zebrafish (Danio rerio) Exposed to Carbendazim

Carbendazim is a systemic fungicide used in several countries, particularly in Brazil. However, studies suggest that it is related to the promotion of tumors, endocrine disruption, and toxicity to organisms, among other effects. As a result, carbendazim is not allowed in the United States, Australia, and some European Union countries. Therefore, further studies are necessary to evaluate its effects, and zebrafish is a model routinely used to provide relevant information regarding the acute and long-term effects of xenobiotics. In this way, zebrafish water tank samples (water samples from aquari containing zebrafish) and liver samples from animals exposed to carbendazim at a concentration of 120 μg/L were analyzed by liquid chromatography coupled to high-resolution mass spectrometry, followed by multivariate and univariate statistical analyses, using the metabolomics approach. Our results suggest impairment of lipid metabolism with a consequent increase in intrahepatic lipids and endocrine disruption. Furthermore, the results suggest two endogenous metabolites as potential biomarkers to determine carbendazim exposure. Finally, the present study showed that it is possible to use zebrafish water tank samples to assess the dysregulation of endogenous metabolites to understand biological effects. Environ Toxicol Chem 2023;42:437-448. © 2022 SETAC.

A metabolic associated fatty liver disease risk variant in MBOAT7 regulates toll like receptor induced outcomes

The breakdown of toll-like receptor (TLR) tolerance results in tissue damage, and hyperactivation of the TLRs and subsequent inflammatory consequences have been implicated as risk factors for more severe forms of disease and poor outcomes from various diseases including COVID-19 and metabolic (dysfunction) associated fatty liver disease (MAFLD). Here we provide evidence that membrane bound O-acyltransferase domain containing 7 (MBOAT7) is a negative regulator of TLR signalling. MBOAT7 deficiency in macrophages as observed in patients with MAFLD and in COVID-19, alters membrane phospholipid composition. We demonstrate that this is associated with a redistribution of arachidonic acid toward proinflammatory eicosanoids, induction of endoplasmic reticulum stress, mitochondrial dysfunction, and remodelling of the accessible inflammatory-related chromatin landscape culminating in macrophage inflammatory responses to TLRs. Activation of MBOAT7 reverses these effects. These outcomes are further modulated by the MBOAT7 rs8736 (T) MAFLD risk variant. Our findings suggest that MBOAT7 can potentially be explored as a therapeutic target for diseases associated with dysregulation of the TLR signalling cascade.

Intestinal metabolomics of juvenile lenok (Brachymystax lenok) in response to heat stress

Changes in the metabolic profile within the intestine of lenok (Brachymystax lenok) when challenged to acute and lethal heat stress (HS) are studied using no-target HPLC-MS/MS metabonomic analysis. A total of 51 differentially expressed metabolites (VIP > 1, P < 0.05) were identified in response to HS, and 34 occurred in the positive ion mode and 17 in negative ion mode, respectively. After heat stress, changes in metabolites related to glycolysis (i.e., alpha-D-glucose, stachyose, and L-lactate) were identified. The metabolites (acetyl carnitine, palmitoylcarnitine, carnitine, and erucic acid) related to fatty acid β-oxidation accumulated significantly, and many amino acids (L-tryptophan, D-proline, L-leucine, L-phenylalanine, L-aspartate, L-tyrosine, L-methionine, L-histidine, and L-glutamine) were significantly decreased in HS-treated lenok. The mitochondrial β-oxidation pathway might be inhibited, while severe heat stress might activate the anaerobic glycolysis and catabolism of amino acid for energy expenditure. Oxidative damage in HS-treated lenok was indicated by the decreased glycerophospholipid metabolites (i.e., glycerophosphocholine, 1-palmitoyl-2-hydroxy-sn-glycero-3-phosphoethanolamine, 1-palmitoyl-sn-glycero-3-phosphocholine, 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine, and 1, 2-dioleoyl-sn-glycero-3-phosphatidylcholine) and the increased oxylipin production (12-HETE and 9R, 10S-EpOME). The minor oxidative pathways (omega-oxidation and peroxisomal beta-oxidation) were likely to be induced in HS-treated lenok.

Lysophosphatidylcholine acyltransferase 3 (LPCAT3) mediates palmitate-induced inflammation in macrophages of large yellow croaker (Larimichthys crocea)

LPCAT3, a subtype of lysophosphatidylcholine acyltransferases, is a key enzyme in phosphatidylcholine remodeling pathway and plays a significant role in mediating inflammatory response in mammals. However, its inflammatory function in fish has yet to be discovered. Herein, this study aimed to investigate its role in inflammation in Larimichthys crocea. We analyzed the coding sequence of Larimichthys crocea LPCAT3 (Lc-LPCAT3) and explored the effect of Lc-LPCAT3 on palmitate (PA)-induced inflammation. We found that in macrophage cell line of Larimichthys crocea, the mRNA expression of Lc-lpcat3 was upregulated by PA with the elevated pro-inflammatory genes expression, including il1β, il6, il8, tnfα and ifnγ. Next, the role of Lc-LPCAT3 in inflammation induced by PA was further investigated. Results showed that knockdown of Lc-LPCAT3 mitigated PA-induced pro-inflammatory genes mRNA expression, including il1β, il8, tnfα and ifnγ, in which JNK signaling pathway was involved. In contrast, overexpression of Lc-LPCAT3 induced pro-inflammatory genes expression including il1β, tnfα and ifnγ. Furthermore, several transcription factors with negative regulation of Lc-LPCAT3 promoter activity were discovered including LXRα, RXRα, PPARα, PPARγ, CEBPα, CEBPβ, CEBPδ, SREBP1 and SREBP2, and SREBP1 had the strongest regulatory effect. In conclusion, we first discovered that fish LPCAT3 participated in PA-induced inflammation, and targeting SREBP1 might be an effective coping strategy.

Membrane-bound O-acyltransferase 7 (MBOAT7)-driven phosphatidylinositol remodeling in advanced liver disease

Advanced liver diseases account for approximately 2 million deaths annually worldwide. Roughly, half of liver disease-associated deaths arise from complications of cirrhosis and the other half driven by viral hepatitis and hepatocellular carcinoma. Unfortunately, the development of therapeutic strategies to treat subjects with advanced liver disease has been hampered by a lack of mechanistic understanding of liver disease progression and a lack of human-relevant animal models. An important advance has been made within the past several years, as several genome-wide association studies have discovered that an SNP near the gene encoding membrane-bound O-acyltransferase 7 (MBOAT7) is associated with severe liver diseases. This common MBOAT7 variant (rs641738, C>T), which reduces MBOAT7 expression, confers increased susceptibility to nonalcoholic fatty liver disease, alcohol-associated liver disease, and liver fibrosis in patients chronically infected with viral hepatitis. Recent studies in mice also show that Mboat7 loss of function can promote hepatic steatosis, inflammation, and fibrosis, causally linking this phosphatidylinositol remodeling enzyme to liver health in both rodents and humans. Herein, we review recent insights into the mechanisms by which MBOAT7-driven phosphatidylinositol remodeling influences liver disease progression and discuss how rapid progress in this area could inform drug discovery moving forward.

The Role of Insulin Resistance in Fueling NAFLD Pathogenesis: From Molecular Mechanisms to Clinical Implications

Non-alcoholic fatty liver disease (NAFLD) represents a predominant hepatopathy that is rapidly becoming the most common cause of hepatocellular carcinoma worldwide. The close association with metabolic syndrome’s extrahepatic components has suggested the nature of the systemic metabolic-related disorder based on the interplay between genetic, nutritional, and environmental factors, creating a complex network of yet-unclarified pathogenetic mechanisms in which the role of insulin resistance (IR) could be crucial. This review detailed the clinical and pathogenetic evidence involved in the NAFLD–IR relationship, presenting both the classic and more innovative models. In particular, we focused on the reciprocal effects of IR, oxidative stress, and systemic inflammation on insulin-sensitivity disruption in critical regions such as the hepatic and the adipose tissue, while considering the impact of genetics/epigenetics on the regulation of IR mechanisms as well as nutrients on specific insulin-related gene expression (nutrigenetics and nutrigenomics). In addition, we discussed the emerging capability of the gut microbiota to interfere with physiological signaling of the hormonal pathways responsible for maintaining metabolic homeostasis and by inducing an abnormal activation of the immune system. The translation of these novel findings into clinical practice could promote the expansion of accurate diagnostic/prognostic stratification tools and tailored pharmacological approaches.

BRAF Modulates Lipid Use and Accumulation

There is increasing evidence that oxidative metabolism and fatty acids play an important role in BRAF-driven tumorigenesis, yet the effect of BRAF mutation and expression on metabolism is poorly understood. We examined how BRAF mutation and expression modulates metabolite abundance. Using the non-transformed NIH3T3 cell line, we generated cells that stably overexpressed BRAF V600E or BRAF WT. We found that cells expressing BRAF V600E were enriched with immunomodulatory lipids. Further, we found a unique transcriptional signature that was exclusive to BRAF V600E expression. We also report that BRAF V600E mutation promoted accumulation of long chain polyunsaturated fatty acids (PUFAs) and rewired metabolic flux for non-Warburg behavior. This cancer promoting mutation further induced the formation of tunneling nanotube (TNT)-like protrusions in NIH3T3 cells that preferentially accumulated lipid droplets. In the plasma of melanoma patients harboring the BRAF V600E mutation, levels of lysophosphatidic acid, sphingomyelin, and long chain fatty acids were significantly increased in the cohort of patients that did not respond to BRAF inhibitor therapy. Our findings show BRAF V600 status plays an important role in regulating immunomodulatory lipid profiles and lipid trafficking, which may inform future therapy across cancers.

Functional and Structural Changes in the Membrane-Bound O-Acyltransferase Family Member 7 (MBOAT7) Protein: The Pathomechanism of a Novel MBOAT7 Variant in Patients With Intellectual Disability

The membrane-bound O-acyltransferase domain-containing 7 (MBOAT7) gene is associated with intellectual disability, early onset seizures, and autism spectrum disorders. This study aimed to determine the pathogenetic mechanism of the MBOAT7 missense variant via molecular modeling. Three patients from a consanguineous family were found to have a homozygous c.757G>A (p.Glu253Lys) variant of MBOAT7. The patients showed prominent dysfunction in gait, swallowing, vocalization, and fine motor function and had intellectual disabilities. Brain magnetic resonance imaging showed signal changes in the bilateral globus pallidi and cerebellar dentate nucleus, which differed with age. In the molecular model of human MBOAT7, Glu253 in the wild-type protein is located close to the backbone carbonyl oxygens in the loop near the helix, suggesting that the ionic interaction could contribute to the conformational stability of the funnel. Molecular modeling showed that Lys253 in the mutant protein was expected to alter the surface charge distribution, thereby potentially affecting substrate specificity. Changes in conformational stability and substrate specificity through varied ionic interactions are the suggested pathophysiological mechanisms of the MBOAT7 variant found in patients with intellectual disabilities.

Quantitative lipidomics and spatial MS-Imaging uncovered neurological and systemic lipid metabolic pathways underlying troglomorphic adaptations in cave-dwelling fish

The Sinocyclocheilus represents a rare, freshwater teleost genus endemic to China that comprises the river-dwelling surface fish and the cave-dwelling cavefish. Using a combinatorial approach of quantitative lipidomics and mass-spectrometry imaging (MSI), we demonstrated that neural compartmentalization of lipid distribution and lipid metabolism are associated with the evolution of troglomorphic traits in Sinocyclocheilus. Attenuated DHA biosynthesis via the Δ4 desaturase pathway led to reductions in docosahexaenoic acid (DHA)-phospholipids in cavefish cerebellum. Instead, cavefish accumulates arachidonic acid (ARA)-phospholipids that may disfavor retinotectal arbor growth. Importantly, MSI of sulfatides, coupled with immunostaining of myelin basic protein and transmission electron microscopy images of hindbrain axons revealed demyelination in cavefish raphe serotonergic neurons. Demyelination in cavefish parallels the loss of neuroplasticity governing social behavior such as aggressive dominance. Outside the brain, quantitative lipidomics and qRT-PCR revealed systemic reductions in membrane esterified DHAs in the liver, attributed to suppression of genes along the Sprecher pathway (elovl2, elovl5, acox1). Development of fatty livers was observed in cavefish, likely mediated by an impeded mobilization of storage lipids, as evident in the diminished expressions of pnpla2, lipea, lipeb, dagla and mgll; and suppressed β-oxidation of fatty acyls via both mitochondria and peroxisomes, reflected in the reduced expressions of cpt1ab, hadhaa, cpt2, decr1 and acox1. These neurological and systemic metabolic adaptations serve to reduce energy expenditure, forming the basis of recessive evolution that eliminates non-essential morphological and behavioral traits, giving cavefish a selective advantage to thrive in caves where proper resource allocation becomes a major determinant of survival.

Comprehensive Analysis of LPCATs Highlights the Prognostic and Immunological Values of LPCAT1/4 in Hepatocellular Carcinoma

Background

The prognosis of patients with advanced hepatocellular carcinoma (HCC) remains poor. Lipid remodeling modulators are considered promising therapeutic targets of cancers, owing to their functions of facilitating cancer cells’ adaption to the limited environment. Lysophosphatidylcholine acyltransferases (LPCATs) are enzymes regulating bio-membrane remodeling, whose roles in HCC have not been fully illuminated.

Methods

Multiple bioinformatic tools were applied to comprehensively evaluate the expression, genetic alterations, clinical relevance, prognostic values, DNA methylation, biological functions, and correlations with immune infiltration of LPCATs in HCC.

Results

We found LPCAT1 was significantly overexpressed and the most frequently altered in HCC. The high-expression of LPCAT1/4 indicated clinicopathological advancements and poor prognoses of HCC patients. Even though the global DNA methylation of LPCATs in HCC showed no significant difference with that in normal liver, the hypermethylation of numerous CpG sites of them implied worse survivals of HCC patients. Thirty LPCATs’ interactive genes were identified, which were generally membrane components and partook in phospholipid metabolism pathways. Finally, we found the expression of LPCATs was extensively positively correlated with the infiltration of various stimulatory and suppressive tumor-infiltrating immune cells (TIICs) in the tumor microenvironment.

Conclusion

This study addressed LPCAT1/4 were potential prognostic and immunotherapeutic biomarkers of HCC targeting bio-membrane lipid remodeling.

Genetics Is of the Essence to Face NAFLD

Nonalcoholic fatty liver disease (NAFLD) is the commonest cause of chronic liver disease worldwide. It is closely related to obesity, insulin resistance (IR) and dyslipidemia so much so it is considered the hepatic manifestation of the Metabolic Syndrome. The NAFLD spectrum extends from simple steatosis to nonalcoholic steatohepatitis (NASH), a clinical condition which may progress up to fibrosis, cirrhosis and hepatocellular carcinoma (HCC). NAFLD is a complex disease whose pathogenesis is shaped by both environmental and genetic factors. In the last two decades, several heritable modifications in genes influencing hepatic lipid remodeling, and mitochondrial oxidative status have been emerged as predictors of progressive hepatic damage. Among them, the patatin-like phospholipase domain-containing 3 (PNPLA3) p.I148M, the Transmembrane 6 superfamily member 2 (TM6SF2) p.E167K and the rs641738 membrane bound-o-acyltransferase domain-containing 7 (MBOAT7) polymorphisms are considered the most robust modifiers of NAFLD. However, a forefront frontier in the study of NAFLD heritability is to postulate score-based strategy, building polygenic risk scores (PRS), which aggregate the most relevant genetic determinants of NAFLD and biochemical parameters, with the purpose to foresee patients with greater risk of severe NAFLD, guaranteeing the most highly predictive value, the best diagnostic accuracy and the more precise individualized therapy.

Mechanisms of Non-Alcoholic Fatty Liver Disease in the Metabolic Syndrome. A Narrative Review

Non-alcoholic fatty liver disease (NAFLD) and metabolic syndrome (MS) are two different entities sharing common clinical and physio-pathological features, with insulin resistance (IR) as the most relevant. Large evidence leads to consider it as a risk factor for cardiovascular disease, regardless of age, sex, smoking habit, cholesterolemia, and other elements of MS. Therapeutic strategies remain still unclear, but lifestyle modifications (diet, physical exercise, and weight loss) determine an improvement in IR, MS, and both clinical and histologic liver picture. NAFLD and IR are bidirectionally correlated and, consequently, the development of pre-diabetes and diabetes is the most direct consequence at the extrahepatic level. In turn, type 2 diabetes is a well-known risk factor for multiorgan damage, including an involvement of cardiovascular system, kidney and peripheral nervous system. The increased MS incidence worldwide, above all due to changes in diet and lifestyle, is associated with an equally significant increase in NAFLD, with a subsequent rise in both morbidity and mortality due to both metabolic, hepatic and cardiovascular diseases. Therefore, the slowdown in the increase of the "bad company" constituted by MS and NAFLD, with all the consequent direct and indirect costs, represents one of the main challenges for the National Health Systems.

A 12-lipoxygenase-Gpr31 signaling axis is required for pancreatic organogenesis in the zebrafish

12-Lipoxygenase (12-LOX) is a key enzyme in arachidonic acid metabolism, and alongside its major product, 12-HETE, plays a key role in promoting inflammatory signaling during diabetes pathogenesis. Although 12-LOX is a proposed therapeutic target to protect pancreatic islets in the setting of diabetes, little is known about the consequences of blocking its enzymatic activity during embryonic development. Here, we have leveraged the strengths of the zebrafish-genetic manipulation and pharmacologic inhibition-to interrogate the role of 12-LOX in pancreatic development. Lipidomics analysis during zebrafish development demonstrated that 12-LOX-generated metabolites of arachidonic acid increase sharply during organogenesis stages, and that this increase is blocked by morpholino-directed depletion of 12-LOX. Furthermore, we found that either depletion or inhibition of 12-LOX impairs both exocrine pancreas growth and unexpectedly, the generation of insulin-producing β cells. We demonstrate that morpholino-mediated knockdown of GPR31, a purported G-protein-coupled receptor for 12-HETE, largely phenocopies both the depletion and the inhibition of 12-LOX. Moreover, we show that loss of GPR31 impairs pancreatic bud fusion and pancreatic duct morphogenesis. Together, these data provide new insight into the requirement of 12-LOX in pancreatic organogenesis and islet formation, and additionally provide evidence that its effects are mediated via a signaling axis that includes the 12-HETE receptor GPR31.

Zebrafish as a model for inflammation and drug discovery

Zebrafish is a small teleost (bony) fish used in many areas of pharmacology and toxicology. This animal model has advantages for the discovery of anti-inflammatory drugs, such as the potential for real-time assessment of cell migration mechanisms. Additionally, zebrafish display a repertoire of inflammatory cells, mediators, and receptors that are similar to those in mammals, including humans. Inflammatory disease modeling in either larvae or adult zebrafish represents a promising tool for the screening of new anti-inflammatory compounds, contributing to our understanding of the mechanisms involved in chronic inflammatory conditions. In this review, we provide an overview of the characterization of inflammatory responses in zebrafish, emphasizing its relevance for drug discovery in this research area.

Genetic and metabolic factors: the perfect combination to treat metabolic associated fatty liver disease

The prevalence of nonalcoholic or more recently re-defined metabolic associated fatty liver disease (MAFLD) is rapidly growing worldwide. It is characterized by hepatic fat accumulation exceeding 5% of liver weight not attributable to alcohol consumption. MAFLD refers to an umbrella of conditions ranging from simple steatosis to nonalcoholic steatohepatitis which may finally progress to cirrhosis and hepatocellular carcinoma. MAFLD is closely related to components of the metabolic syndrome and to environmental factors. In addition to the latter, genetic predisposition plays a key role in MAFLD pathogenesis and strictly contributes to its progressive forms. The candidate genes which have been related to MAFLD hereditability are mainly involved in lipids remodeling, lipid droplets assembly, lipoprotein packaging and secretion, de novo lipogenesis, and mitochondrial redox status. In the recent years, it has emerged the opportunity to translate the genetics into clinics by aggregating the genetic variants mostly associated with MAFLD in polygenic risk scores. These scores might be used in combination with metabolic factors to identify those patients at higher risk to develop more severe liver disease and to schedule an individual therapeutic approach.

Genetics and epigenetics purpose in nonalcoholic fatty liver disease

INTRODUCTION

nonalcoholic fatty liver disease (NAFLD) comprises a broad spectrum of diseases, which can progress from benign steatosis to nonalcoholic steatohepatitis, liver cirrhosis and hepatocellular carcinoma. NAFLD is the most common chronic liver disease in developed countries, affecting approximately 25% of the general population. Insulin resistance, adipose tissue dysfunction, mitochondrial and endoplasmic reticulum stress, chronic inflammation, genetic and epigenetic factors are NAFLD triggers that control the disease susceptibility and progression.

AREAS COVERED

In recent years a large number of investigations have been carried out to elucidate genetic and epigenetic factors in the disease pathogenesis, as well as the search for diagnostic markers and therapeutic targets. This paper objective is to report the most studied genetic and epigenetic variants around NAFLD.

EXPERT OPINION

NAFLD lead to various comorbidities, which have a considerable impact on the patient wellness and life quality, as well as on the costs they generate for the country's health services. It is essential to continue with molecular research, since it could be used as a clinical tool for prognosis and disease severity. Specifically, in the field of hepatology, plasma miRNAs could provide a novel tool in liver diseases diagnosis and monitoring, representing an alternative to invasive diagnostic procedures.

MBOAT7 down-regulation by genetic and environmental factors predisposes to MAFLD

Metabolic associated fatty liver disease (MAFLD) encompasses a broad spectrum of hepatic disorders, which include steatosis, nonalcoholic steatohepatitis (NASH), fibrosis and cirrhosis, that is a critical risk factor for hepatocellular carcinoma (HCC) development. Its pathogenesis is intertwined with obesity and type 2 diabetes (T2D). However, the predisposition to develop MAFLD is severely influenced by environmental and inherited cues. The rs641738 variant close to MBOAT7 gene has been identified by a genome-wide association screening in heavy drinkers. Although this variant has been associated with the entire spectrum of MAFLD, these results have not been completely replicated and the debate is still opened. Thus, functional studies that unravel the biological mechanisms underlying the genetic association with fatty liver are required. This review aims to summarize the clinical and experimental findings regarding the rs641738 variation and MBOAT7 function, with the purpose to shed light to its role as novel player in MAFLD pathophysiology.

Dermal Adipocyte Lipolysis and Myofibroblast Conversion Are Required for Efficient Skin Repair

Mature adipocytes store fatty acids and are a common component of tissue stroma. Adipocyte function in regulating bone marrow, skin, muscle, and mammary gland biology is emerging, but the role of adipocyte-derived lipids in tissue homeostasis and repair is poorly understood. Here, we identify an essential role for adipocyte lipolysis in regulating inflammation and repair after injury in skin. Genetic mouse studies revealed that dermal adipocytes are necessary to initiate inflammation after injury and promote subsequent repair. We find through histological, ultrastructural, lipidomic, and genetic experiments in mice that adipocytes adjacent to skin injury initiate lipid release necessary for macrophage inflammation. Tamoxifen-inducible genetic lineage tracing of mature adipocytes and single-cell RNA sequencing revealed that dermal adipocytes alter their fate and generate ECM-producing myofibroblasts within wounds. Thus, adipocytes regulate multiple aspects of repair and may be therapeutic for inflammatory diseases and defective wound healing associated with aging and diabetes.

Noninvasive Evaluation of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent liver diseases and can progress to advanced fibrosis and end-stage liver disease. Thus, intensive research has been performed to develop noninvasive methods for the diagnosis of nonalcoholic steatohepatitis (NASH) and fibrosis. Currently, no single noninvasive tool covers all of the stages of pathologies and conditions of NAFLD, and the cost and feasibility of known techniques are also important issues. Blood biomarkers for NAFLD may be useful to select subjects who need ultrasonography (US) screening for NAFLD, and noninvasive tools for assessing fibrosis may be helpful to exclude the probability of significant fibrosis and to predict advanced fibrosis, thus guiding the decision of whether to perform liver biopsy in patients with NAFLD. Among various methods, magnetic resonance-based methods have been shown to perform better than other methods in assessing steatosis as well as in detecting hepatic fibrosis. Many genetic markers are associated with the development and progression of NAFLD. Further well-designed studies are needed to determine which biomarker panels, imaging studies, genetic marker panels, or combinations thereof perform well for diagnosing NAFLD, differentiating NASH and fibrosis, and following-up NAFLD, respectively.

Non-Alcoholic Fatty Liver Disease in Patients with Type 2 Diabetes Mellitus: A Position Statement of the Fatty Liver Research Group of the Korean Diabetes Association

This clinical practice position statement, a product of the Fatty Liver Research Group of the Korean Diabetes Association, proposes recommendations for the diagnosis, progression and/or severity assessment, management, and follow-up of non-alcoholic fatty liver disease (NAFLD) in patients with type 2 diabetes mellitus (T2DM). Patients with both T2DM and NAFLD have an increased risk of non-alcoholic steatohepatitis (NASH) and fibrosis and a higher risk of cardiovascular diseases and diabetic complications compared to those without NAFLD. With regards to the evaluation of patients with T2DM and NAFLD, ultrasonography-based stepwise approaches using noninvasive biomarker models such as fibrosis-4 or the NAFLD fibrosis score as well as imaging studies such as vibration-controlled transient elastography with controlled attenuation parameter or magnetic resonance imaging-proton density fat fraction are recommended. After the diagnosis of NAFLD, the stage of fibrosis needs to be assessed appropriately. For management, weight reduction achieved by lifestyle modification has proven beneficial and is recommended in combination with antidiabetic agent(s). Evidence that some antidiabetic agents improve NAFLD/NASH with fibrosis in patients with T2DM is emerging. However, there are currently no definite pharmacologic treatments for NAFLD in patients with T2DM. For specific cases, bariatric surgery may be an option if indicated.

Nutrition and Genetics in NAFLD: The Perfect Binomium

Nonalcoholic fatty liver disease (NAFLD) represents a global healthcare burden since it is epidemiologically related to obesity, type 2 diabetes (T2D) and Metabolic Syndrome (MetS). It embraces a wide spectrum of hepatic injuries, which include simple steatosis, nonalcoholic steatohepatitis (NASH), fibrosis, cirrhosis and hepatocellular carcinoma (HCC). The susceptibility to develop NAFLD is highly variable and it is influenced by several cues including environmental (i.e., dietary habits and physical activity) and inherited (i.e., genetic/epigenetic) risk factors. Nonetheless, even intestinal microbiota and its by-products play a crucial role in NAFLD pathophysiology. The interaction of dietary exposure with the genome is referred to as 'nutritional genomics,' which encompasses both 'nutrigenetics' and 'nutriepigenomics.' It is focused on revealing the biological mechanisms that entail both the acute and persistent genome-nutrient interactions that influence health and it may represent a promising field of study to improve both clinical and health nutrition practices. Thus, the premise of this review is to discuss the relevance of personalized nutritional advices as a novel therapeutic approach in NAFLD tailored management.

Mboat7 down-regulation by hyper-insulinemia induces fat accumulation in hepatocytes

Background

Naturally occurring variation in Membrane-bound O-acyltransferase domain-containing 7 (MBOAT7), encoding for an enzyme involved in phosphatidylinositol acyl-chain remodelling, has been associated with fatty liver and hepatic disorders. Here, we examined the relationship between hepatic Mboat7 down-regulation and fat accumulation.

Methods

Hepatic MBOAT7 expression was surveyed in 119 obese individuals and in experimental models. MBOAT7 was acutely silenced by antisense oligonucleotides in C57Bl/6 mice, and by CRISPR/Cas9 in HepG2 hepatocytes.

Findings

In obese individuals, hepatic MBOAT7 mRNA decreased from normal liver to steatohepatitis, independently of diabetes, inflammation and MBOAT7 genotype. Hepatic MBOAT7 levels were reduced in murine models of fatty liver, and by hyper-insulinemia. In wild-type mice, Mboat7 was down-regulated by refeeding and insulin, concomitantly with insulin signalling activation. Acute hepatic Mboat7 silencing promoted hepatic steatosis in vivo and enhanced expression of fatty acid transporter Fatp1. MBOAT7 deletion in hepatocytes reduced the incorporation of arachidonic acid into phosphatidylinositol, consistently with decreased enzymatic activity, determining the accumulation of saturated triglycerides, enhanced lipogenesis and FATP1 expression, while FATP1 deletion rescued the phenotype.

Interpretation

MBOAT7 down-regulation by hyper-insulinemia contributes to hepatic fat accumulation, impairing phosphatidylinositol remodelling and up-regulating FATP1.

Funding

LV was supported by MyFirst Grant AIRC n.16888, Ricerca Finalizzata Ministero della Salute RF-2016–02,364,358, Ricerca corrente Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico; LV and AG received funding from the European Union Programme Horizon 2020 (No. 777,377) for the project LITMUS-“Liver Investigation: Testing Marker Utility in Steatohepatitis”. MM was supported by Fondazione Italiana per lo Studio del Fegato (AISF) ‘Mario Coppo’ fellowship.

Obesity-linked suppression of membrane-bound O-acyltransferase 7 (MBOAT7) drives non-alcoholic fatty liver disease

Recent studies have identified a genetic variant rs641738 near two genes encoding membrane bound O-acyltransferase domain-containing 7 (MBOAT7) and transmembrane channel-like 4 (TMC4) that associate with increased risk of non-alcoholic fatty liver disease (NAFLD), non-alcoholic steatohepatitis (NASH), alcohol-related cirrhosis, and liver fibrosis in those infected with viral hepatitis (Buch et al., 2015; Mancina et al., 2016; Luukkonen et al., 2016; Thabet et al., 2016; Viitasalo et al., 2016; Krawczyk et al., 2017; Thabet et al., 2017). Based on hepatic expression quantitative trait loci analysis, it has been suggested that MBOAT7 loss of function promotes liver disease progression (Buch et al., 2015; Mancina et al., 2016; Luukkonen et al., 2016; Thabet et al., 2016; Viitasalo et al., 2016; Krawczyk et al., 2017; Thabet et al., 2017), but this has never been formally tested. Here we show that Mboat7 loss, but not Tmc4, in mice is sufficient to promote the progression of NAFLD in the setting of high fat diet. Mboat7 loss of function is associated with accumulation of its substrate lysophosphatidylinositol (LPI) lipids, and direct administration of LPI promotes hepatic inflammatory and fibrotic transcriptional changes in an Mboat7-dependent manner. These studies reveal a novel role for MBOAT7-driven acylation of LPI lipids in suppressing the progression of NAFLD.

Non-alcoholic fatty liver disease, or NAFLD for short, is a medical condition that develops when the liver accumulates excess fat. It can lead to complications such as diabetes and liver scarring. In humans, mutations that inactivate a protein called MBOAT7 increase the risk of fat accumulating in the liver.

Genetic studies suggest that low levels of MBOAT7 in a human’s liver cells increase the severity of NAFLD. Yet the links between MBOAT7, NAFLD and obesity are not well understood. Helsley et al. used data from humans and from obese mice that had been fed a high-fat diet to investigate the relationship between NAFLD and MBOAT7. This revealed that people who are obese have lower levels of MBOAT7 in their livers. Next, obese mice were genetically manipulated to produce less MBOAT7, which led them to develop more severe NAFLD.

Helsley et al. then grew human liver cells in the laboratory and lowered their levels of MBOAT7, which led to excess fat accumulating in the cells. This increase in fat accumulation was, at least in part, due to how these cells metabolize fats when MBOAT7 is reduced: they start making more new fats and consume fewer lipids to produce energy.

These findings provide a link between obesity and liver damage in both humans and mice, and show how a decrease in MBOAT7 levels causes changes in fat metabolism that could lead to NAFLD. The results could drive new approaches to treating liver damage in patients with mutations in the gene that codes for MBOAT7.

Effect of MBOAT7 variant on hepatitis B and C infections in Moroccan patients

The outcomes of HBV and HCV infections are associated both with viral and host genetic factors. Here, we explore the role of a genetic variation located in membrane-bound O-acyltransferase domain-containing protein 7 (MBOAT7) gene on spontaneous clearance of HBV and HCV infections and on liver fibrosis. We genotyped MBOAT7 rs641738 polymorphism in 971 consecutive Moroccan subjects, including 288 patients with chronic hepatitis C (CHC), 98 cases with spontaneous clearance of HCV, 268 patients with chronic hepatitis B (CHB), 126 spontaneously cleared HBV infections and 191 healthy controls. MBOAT7 rs641738 variant is not associated with spontaneous clearance of HBV (OR = 0.67, 95% CI: 0.39-1.14; p = 0.131) and HCV infections (OR = 1.33, 95% CI: 0.79-2.23; p = 0.278). Furthermore, multivariable logistic regression analysis adjusted for biologically relevant covariates and potential confounders associated with the risk of liver disease progression revealed that MBOAT7 rs641738 is not associated either with fibrosis progression in CHC group (OR = 1.12; 95% CI: 0.55-2.28; p = 0.761) or with chronic progressive state in CHB patients (OR = 0.81; 95% CI: 0.41-1.61; p = 0.547). We conclude that the variant MBOAT7 rs641738 genotype is not associated with spontaneous clearance of HBV and HCV infections or with the progression of liver disease in chronic hepatitis B or C in a genetic context of Mediterranean patients.

Dormant 5-lipoxygenase in inflammatory macrophages is triggered by exogenous arachidonic acid

The differentiation of resident tissue macrophages from embryonic precursors and that of inflammatory macrophages from bone marrow cells leads to macrophage heterogeneity. Further plasticity is displayed through their ability to be polarized as subtypes M1 and M2 in a cell culture microenvironment. However, the detailed regulation of eicosanoid production and its involvement in macrophage biology remains unclear. Using a lipidomics approach, we demonstrated that eicosanoid production profiles between bone marrow-derived (BMDM) and peritoneal macrophages differed drastically. In polarized BMDMs, M1 and M2 phenotypes were distinguished by thromboxane B2, prostaglandin (PG) E2, and PGD2 production, in addition to lysophospholipid acyltransferase activity. Although Alox5 expression and the presence of 5-lipoxygenase (5-LO) protein in BMDMs was observed, the absence of leukotrienes production reflected an impairment in 5-LO activity, which could be triggered by addition of exogenous arachidonic acid (AA). The BMDM 5-LO regulatory mechanism was not responsive to PGE2/cAMP pathway modulation; however, treatment to reduce glutathione peroxidase activity increased 5-LO metabolite production after AA stimulation. Understanding the relationship between the eicosanoids pathway and macrophage biology may offer novel strategies for macrophage-associated disease therapy.

Lipid catabolism inhibition sensitizes prostate cancer cells to antiandrogen blockade

Prostate cancer (PCa) is the most common malignancy among Western men and the second leading-cause of cancer related deaths. For men who develop metastatic castration resistant PCa (mCRPC), survival is limited, making the identification of novel therapies for mCRPC critical. We have found that deficient lipid oxidation via carnitine palmitoyltransferase (CPT1) results in decreased growth and invasion, underscoring the role of lipid oxidation to fuel PCa growth. Using immunohistochemistry we have found that the CPT1A isoform is abundant in PCa compared to benign tissue (n=39, p<0.001) especially in those with high-grade tumors. Since lipid oxidation is stimulated by androgens, we have evaluated the synergistic effects of combining CPT1A inhibition and anti-androgen therapy. Mechanistically, we have found that decreased CPT1A expression is associated with decreased AKT content and activation, likely driven by a breakdown of membrane phospholipids and activation of the INPP5K phosphatase. This results in increased androgen receptor (AR) action and increased sensitivity to the anti-androgen enzalutamide. To better understand the clinical implications of these findings, we have evaluated fat oxidation inhibitors (etomoxir, ranolazine and perhexiline) in combination with enzalutamide in PCa cell models. We have observed a robust growth inhibitory effect of the combinations, including in enzalutamide-resistant cells and mouse TRAMPC1 cells, a more neuroendocrine PCa model. Lastly, using a xenograft mouse model, we have observed decreased tumor growth with a systemic combination treatment of enzalutamide and ranolazine. In conclusion, our results show that improved anti-cancer efficacy can be achieved by co-targeting the AR axis and fat oxidation via CPT1A, which may have clinical implications, especially in the mCRPC setting.

The membrane-bound O-acyltransferase domain-containing 7 variant rs641738 increases inflammation and fibrosis in chronic hepatitis B

Chronic hepatitis B (CHB) is characterized by hepatic inflammation that promotes progression to cirrhosis and predisposes to the development of hepatocellular carcinoma (HCC). Subtle interindividual genetic variation as well as viral and environmental factors interact to determine disease progression between individuals. Recently, the rs641738 membrane-bound O-acyltransferase domain-containing 7 (MBOAT7) polymorphism was demonstrated to influence histological liver damage in alcoholic liver disease, nonalcoholic fatty liver disease, and hepatitis C, but no data are available for CHB. We evaluated rs641738 influence on disease severity in a cohort of 1,101 patients with CHB. Forty-two patients underwent gene expression analysis to assess the functional consequences of rs641738 on hepatic MBOAT7 expression. The minor allele (T) of rs641738 was associated with greater inflammation (odds ratio [OR], 1.45; 95% confidence interval [CI], 1.06-1.95; P = 0.001) and fibrosis (OR = 1.31; 95% CI, 1.19-1.92; P = 0.01). Risk allele frequency in whites (0.43) was greater than in Chinese (0.24), translating to a larger size effect in the former. The rs641738 (T) allele was associated with lower hepatic MBOAT7 expression (P = 0.008), and the latter was associated with serum liver enzymes and inflammation. Neither patatin-like phospholipase domain-containing protein 3 rs738409 nor transmembrane 6 superfamily member 2 rs58542926 polymorphisms influenced disease severity.

CONCLUSION

In patients with CHB, MBOAT7 rs641738 influences hepatic inflammation and fibrosis stage. (Hepatology 2017;65:1840-1850).

Inflammatory stimuli induce acyl-CoA thioesterase 7 and remodeling of phospholipids containing unsaturated long (≥C20)-acyl chains in macrophages

Acyl-CoA thioesterase 7 (ACOT7) is an intracellular enzyme that converts acyl-CoAs to FFAs. ACOT7 is induced by lipopolysaccharide (LPS); thus, we investigated downstream effects of LPS-induced induction of ACOT7 and its role in inflammatory settings in myeloid cells. Enzymatic thioesterase activity assays in WT and ACOT7-deficient macrophage lysates indicated that endogenous ACOT7 contributes a significant fraction of total acyl-CoA thioesterase activity toward C20:4-, C20:5-, and C22:6-CoA, but contributes little activity toward shorter acyl-CoA species. Lipidomic analyses revealed that LPS causes a dramatic increase, primarily in bis(monoacylglycero)phosphate species containing long (≥C20) polyunsaturated acyl-chains in macrophages, and that the limited effect observed by ACOT7 deficiency is restricted to glycerophospholipids containing 20-carbon unsaturated acyl-chains. Furthermore, ACOT7 deficiency did not detectably alter the ability of LPS to induce cytokines or prostaglandin E₂ production in macrophages. Consistently, although ACOT7 was induced in macrophages from diabetic mice, hematopoietic ACOT7 deficiency did not alter the stimulatory effect of diabetes on systemic inflammation or atherosclerosis in LDL receptor-deficient mice. Thus, inflammatory stimuli induce ACOT7 and remodeling of phospholipids containing unsaturated long (≥C20)-acyl chains in macrophages, and, although ACOT7 has preferential thioesterase activity toward these lipid species, loss of ACOT7 has no major detrimental effect on macrophage inflammatory phenotypes.≥.

Mutations in MBOAT7, Encoding Lysophosphatidylinositol Acyltransferase I, Lead to Intellectual Disability Accompanied by Epilepsy and Autistic Features

The risk of epilepsy among individuals with intellectual disability (ID) is approximately ten times that of the general population. From a cohort of >5,000 families affected by neurodevelopmental disorders, we identified six consanguineous families harboring homozygous inactivating variants in MBOAT7, encoding lysophosphatidylinositol acyltransferase (LPIAT1). Subjects presented with ID frequently accompanied by epilepsy and autistic features. LPIAT1 is a membrane-bound phospholipid-remodeling enzyme that transfers arachidonic acid (AA) to lysophosphatidylinositol to produce AA-containing phosphatidylinositol. This study suggests a role for AA-containing phosphatidylinositols in the development of ID accompanied by epilepsy and autistic features.