Strain dropouts reveal interactions that govern the metabolic output of the gut microbiome.

The gut microbiome is complex, raising questions about the role of individual strains in the community. Here, we address this question by constructing variants of a complex defined community in which we eliminate strains that occupy the bile acid 7α-dehydroxylation niche. Omitting Clostridium scindens (Cs) and Clostridium hylemonae (Ch) eliminates secondary bile acid production and reshapes the community in a highly specific manner: eight strains change in relative abundance by >100-fold. In single-strain dropout communities, Cs and Ch reach the same relative abundance and dehydroxylate bile acids to a similar extent. However, Clostridium sporogenes increases >1,000-fold in the ΔCs but not ΔCh dropout, reshaping the pool of microbiome-derived phenylalanine metabolites. Thus, strains that are functionally redundant within a niche can have widely varying impacts outside the niche, and a strain swap can ripple through the community in an unpredictable manner, resulting in a large impact on an unrelated community-level phenotype.

A gut microbial metabolite of dietary polyphenols reverses obesity-driven hepatic steatosis.

The molecular mechanisms by which dietary fruits and vegetables confer cardiometabolic benefits remain poorly understood. Historically, these beneficial properties have been attributed to the antioxidant activity of flavonoids. Here, we reveal that the host metabolic benefits associated with flavonoid consumption hinge, in part, on gut microbial metabolism. Specifically, we show that a single gut microbial flavonoid catabolite, 4-hydroxyphenylacetic acid (4-HPAA), is sufficient to reduce diet-induced cardiometabolic disease (CMD) burden in mice. The addition of flavonoids to a high fat diet heightened the levels of 4-HPAA within the portal plasma and attenuated obesity, and continuous delivery of 4-HPAA was sufficient to reverse hepatic steatosis. The antisteatotic effect was shown to be associated with the activation of AMP-activated protein kinase α (AMPKα). In a large survey of healthy human gut metagenomes, just over one percent contained homologs of all four characterized bacterial genes required to catabolize flavonols into 4-HPAA. Our results demonstrate the gut microbial contribution to the metabolic benefits associated with flavonoid consumption and underscore the rarity of this process in human gut microbial communities.

Fibrosis in IBD: from pathogenesis to therapeutic targets.

BACKGROUND: Intestinal fibrosis resulting in stricture formation and obstruction in Crohn's disease (CD) and increased wall stiffness leading to symptoms in ulcerative colitis (UC) is among the largest unmet needs in inflammatory bowel disease (IBD). Fibrosis is caused by a multifactorial and complex process involving immune and non-immune cells, their soluble mediators and exposure to luminal contents, such as microbiota and environmental factors. To date, no antifibrotic therapy is available. Some progress has been made in creating consensus definitions and measurements to quantify stricture morphology for clinical practice and trials, but approaches to determine the degree of fibrosis within a stricture are still lacking. OBJECTIVE: We herein describe the current state of stricture pathogenesis, measuring tools and clinical trial endpoints development. DESIGN: Data presented and discussed in this review derive from the past and recent literature and the authors' own research and experience. RESULTS AND CONCLUSIONS: Significant progress has been made in better understanding the pathogenesis of fibrosis, but additional studies and preclinical developments are needed to define specific therapeutic targets.

Milk fat globule-epidermal growth factor 8 (MFGE8) prevents intestinal fibrosis.

OBJECTIVE: Intestinal fibrosis is considered an inevitable consequence of chronic IBD, leading to stricture formation and need for surgery. During the process of fibrogenesis, extracellular matrix (ECM) components critically regulate the function of mesenchymal cells. We characterised the composition and function of ECM in fibrostenosing Crohn's disease (CD) and control tissues. DESIGN: Decellularised full-thickness intestinal tissue platforms were tested using three different protocols, and ECM composition in different tissue phenotypes was explored by proteomics and validated by quantitative PCR (qPCR) and immunohistochemistry. Primary human intestinal myofibroblasts (HIMFs) treated with milk fat globule-epidermal growth factor 8 (MFGE8) were evaluated regarding the mechanism of their antifibrotic response, and the action of MFGE8 was tested in two experimental intestinal fibrosis models. RESULTS: We established and validated an optimal decellularisation protocol for intestinal IBD tissues. Matrisome analysis revealed elevated MFGE8 expression in CD strictured (CDs) tissue, which was confirmed at the mRNA and protein levels. Treatment with MFGE8 inhibited ECM production in normal control HIMF but not CDs HIMF. Next-generation sequencing uncovered functionally relevant integrin-mediated signalling pathways, and blockade of integrin αvß5 and focal adhesion kinase rendered HIMF non-responsive to MFGE8. MFGE8 prevented and reversed experimental intestinal fibrosis in vitro and in vivo. CONCLUSION: MFGE8 displays antifibrotic effects, and its administration may represent a future approach for prevention of IBD-induced intestinal strictures.

Muscular Hyperplasia in Crohn's disease Strictures: Through Thick and Thin.

Fibrostenosing Crohn's disease (CD) represents a challenging clinical condition characterized by the development of symptomatic strictures within the gastrointestinal tract. Despite therapeutic advancements in managing inflammation, the progression of fibrostenotic complications remains a significant concern, often necessitating surgical intervention. Recent investigations have unveiled the pivotal role of smooth muscle cell hyperplasia in driving luminal narrowing and clinical symptomatology. Drawing parallels to analogous inflammatory conditions affecting other organs, such as the airways and blood vessels, sheds light on common underlying mechanisms of muscular hyperplasia. This review synthesizes current evidence to elucidate the mechanisms underlying smooth muscle cell proliferation in CD-associated strictures, offering insights into potential therapeutic targets. By highlighting the emerging significance of muscle thickening as a novel therapeutic target, this review aims to inform future research endeavors and clinical strategies with the goal to mitigate the burden of fibrostenotic complications in CD and other conditions.

Metaorganismal choline metabolism shapes olfactory perception.

Microbes living in the intestine can regulate key signaling processes in the central nervous system that directly impact brain health. This gut-brain signaling axis is partially mediated by microbe-host-dependent immune regulation, gut-innervating neuronal communication, and endocrine-like small molecule metabolites that originate from bacteria to ultimately cross the blood-brain barrier. Given the mounting evidence of gut-brain crosstalk, a new therapeutic approach of "psychobiotics" has emerged, whereby strategies designed to primarily modify the gut microbiome have been shown to improve mental health or slow neurodegenerative diseases. Diet is one of the most powerful determinants of gut microbiome community structure, and dietary habits are associated with brain health and disease. Recently, the metaorganismal (i.e., diet-microbe-host) trimethylamine N-oxide (TMAO) pathway has been linked to the development of several brain diseases including Alzheimer's, Parkinson's, and ischemic stroke. However, it is poorly understood how metaorganismal TMAO production influences brain function under normal physiological conditions. To address this, here we have reduced TMAO levels by inhibiting gut microbe-driven choline conversion to trimethylamine (TMA), and then performed comprehensive behavioral phenotyping in mice. Unexpectedly, we find that TMAO is particularly enriched in the murine olfactory bulb, and when TMAO production is blunted at the level of bacterial choline TMA lyase (CutC/D), olfactory perception is altered. Taken together, our studies demonstrate a previously underappreciated role for the TMAO pathway in olfactory-related behaviors.

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.

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.

Parents' perceptions of school recess policies and practices.

BACKGROUND: Previous research has shown that school recess can provide children with physical, social and cognitive benefits; yet, recess opportunities and experiences may be different for different groups of children, specifically for children living in lower income environments, children of different racial groups other than white, and for children with disabilities. Parent perceptions of recess are important to consider as they serve as advocates for their children's access and opportunities at school as well as an additional informant for children's experiences at recess that may be useful for policymakers and school boards to consider. OBJECTIVE: To examine parent perceptions of recess by children's disability status, children's race and ethnicity, and family household income. METHOD: Participants included 473 parents from the U.S.A. stratified across six household income levels. Data were collected through an online survey using Prolific in May of 2020]. Confirmatory factor analyses were run for measures assessing parents' perception of belonging and victimization at recess, recess policies, and recess procedures. Regression analyses were run to examine if parents' perception of recess were predicted by race, income, or child disability status. RESULTS: Results revealed that parents' perceptions of recess were predicted by child disability status but not race or income. Specifically, parents' perceptions were significantly predicted by child disability status regarding victimization (b = .13, SE = .06, p = .05), recess policies about withholding recess (b = .171, SE = .07, p = .01), and finally, student engagement at recess (b = .165, SE = .07, p = .02). CONCLUSION: Results show that parents of children with a disability perceive a different recess experience for their child that involves more instances of victimization compared to parents of typically developing children. Based on these findings, school, district, and state policy makers could consider ensuring that recess includes multiple activities, is supervised by adults, and is a space where conflict resolution occurs, for creating a more inclusive environment for children with disabilities.

An observational study of recess quality and physical activity in urban primary schools.

BACKGROUND: To date, there is scant literature that examines the recess context concurrent with, but separate from, levels of physical activity. The primary purpose of the current study was to examine how recess quality impacted physical activity levels, and how this was moderated by gender. A secondary purpose was to examine if differences in children's engagement in activities occurred between recess sessions scored as low- or high- quality. METHODS: This was an observational study of children at 13 urban elementary schools in the U.S. Across the 13 schools, data were collected at 55 recess sessions, with 3419 child-level observations (n = 1696 boys; n = 1723 girls). Physical activity data were collected using Fitbit accelerometers, recess quality data were collected using the Great Recess Framework - Observational Tool (GRF-OT), recess engagement data were collected using the Observation of Playground Play (OPP), and basic psychological need satisfaction (BPNS) data were collected using a modified version of the BPNS for recess physical activity survey. Primary analyses were conducted using Hierarchical Linear Modeling (HLM) with children nested within recess sessions. RESULTS: Gender moderated the relationship between adult engagement and moderate-to-vigorous physical activity (MVPA) (b = .012; 95% CI .001, .024), student behavior and MVPA (b = -.014; 95% CI -.021, -.007), and student behaviors and light physical activity (b = .009, 95% CI .003, .015). Both boys and girls engaged in more play during recess sessions scored as high quality on the GRF-OT. Children reported higher levels of basic psychological need satisfaction at recesses sessions scored as high quality on the GRF-OT. CONCLUSIONS: Results of the current study showed that the quality of the recess environment, and the interactions of both adults and students in that environment, need to be taken into consideration in future school-based recess studies.

Sporting Activities for Individuals Who Experienced Trauma During Their Youth: A Meta-Study.

The purpose of this study was to critically examine the qualitative research on childhood trauma survivors' experiences of sporting activities. A comprehensive search of health and social science databases, manual journal searches, and contact with experts yielded 7,395 records. Full-text screening resulted in a final sample of 16 studies. Meta-study methodology was used as a diagnostic tool to rigorously analyze the theory, methods, and findings of the included studies. Studies with explicit connections between philosophy, theory, and methodology resulted in a more robust and critical contribution to the literature. There was much diversity in terms of methodological approaches and qualitative methods which was important in revealing the multifaceted nature of experiences in sporting activities following trauma. Findings from the reviewed studies indicated that a sense of belonging, psychological escape, embodied experience, and the physical and social environmental are important considerations in the study of sporting activities for trauma survivors.

Perceived Barriers Before and After a 3-Month Period of Modified Ride-On Car Use.

PURPOSE: The purpose of the study is to examine how perceived barriers change before and after a 3-month period of modified ride-on car use. METHODS: This study used a qualitative content analysis of perceived barriers. Fourteen caregivers (13 mothers; 1 grandmother) responded to a single-question, free-response survey before and after a 3-month period of modified ride-on car use. RESULTS: A total of 11 and 20 perceived barriers were reported before and after the 3-month period. Environmental barriers were the most frequently reported before and after the 3-month period. CONCLUSIONS: Pediatric physical therapists need to be aware of the potential perceived barriers that families may experience in regard to young children with disabilities using modified ride-on cars and determine strategies to support families on an individual basis.

Perceived Barriers of Modified Ride-On Car Use of Young Children With Disabilities: A Content Analysis.

PURPOSE: Modified ride-on cars have emerged as an early powered mobility option for young children with disabilities. The purpose of this study was to identify, extract, and synthesize perceived barriers of modified ride-on car use reported in previous studies. METHODS: This study was descriptive using a qualitative content analysis of previously published studies identified from a systematic literature search. RESULTS: Categories of perceived barriers were identified: device, environmental, child-related perceived barriers regarding health, tolerance, and abilities, and caregiver-related perceived barriers regarding physical requirements, time, and motivation. Device and environmental perceived barriers were the most reported. CONCLUSIONS: Pediatric physical therapists play a critical role in working with families to promote their self-efficacy for using the modified ride-on car and their capacity for overcoming the inherent difficulties associated with use. Most of the reported perceived barriers are modifiable, at least to some degree, with likely effects on modified ride-on car use.

Sport-based youth development interventions in the United States: a systematic review.

BACKGROUND: The growing number of sport-based youth development interventions provide a potential avenue for integrating sport meaningfully into the U.S. public health agenda. However, efficacy and quality must be reliably established prior to widespread implementation. METHODS: A comprehensive search of databases, peer-reviewed journals, published reviews, and both published and unpublished documents yielded 10,077 distinct records. Title and abstract screening, followed by full-text screening using 6 criteria, resulted in 56 distinct studies (coalescing into 10 sport-based youth development intervention types) included in the synthesis. These studies were then independently assessed and critically appraised. RESULTS: Limited efficacy data were identified, with the quality of methods and evidence largely classified as weak. Processes likely to contribute to the outcomes of sport-based youth development interventions were identified (e.g., predictors of ongoing engagement, alignment between target population and intervention, intervention design), although more rigorous research is needed on these and other processes. Physical health outcomes were only studied in 3 of the 10 intervention types. CONCLUSIONS: The evidence base does not yet warrant wide-scale implementation of sport-based youth development interventions for public health goals within the U. S., although there is promising research that identifies areas for further exploration.

Development of the great recess framework - observational tool to measure contextual and behavioral components of elementary school recess.

BACKGROUND: Physical activity (PA) remains the primary behavioral outcome associated with school recess, while many other potentially relevant indicators of recess remain unexamined. Few studies have assessed observations of teacher/student interactions, peer conflict, social interactions, or safety within the recess environment. Furthermore, a psychometrically-sound instrument does not exist to examine safety, resources, student engagement, adult engagement, pro-social/anti-social behavior, and student empowerment on the playground. The purpose of the current study was to develop a valid, and reliable, assessment tool intended for use in measurement of the contextual factors associated with recess. METHODS: An iterative and multi-step process was used to develop a tool that measures safety and structure, adult engagement and supervision, student behaviors, and transitions at recess. Exploratory structural equation modeling (Mplus v. 7.4) was used to examine the underlying measurement model with observational data of the recess environment collected at 649 school-based recess periods that spanned across 22 urban/metropolitan areas in the USA. Data were also collected by two researchers at 162 recess sessions across 9 schools to examine reliability. RESULTS: A 17-item observation instrument, the Great Recess Framework - Observational Tool (GRF-OT), was created. Findings of exploratory structural equation modeling (ESEM) analyses supported factorial validity for a 4-factor solution and linear regressions established convergent validity where 'structure and safety', 'adult engagement and supervision', and 'student behaviors' were all significantly related to observed activity levels. Each sub-scale of the GRF-OT showed adequate levels of inter-rater reliability and test-retest reliability analysis indicated a higher level of stability for the GRF-OT when using a three-day average across two time points as compared to a two-day average. CONCLUSIONS: Initial evidence for a valid, and reliable, assessment tool to observationally measure the recess environment with a specific focus on safety, resources, student engagement, adult engagement, pro-social/anti-social behavior, and student empowerment was established in this study. Use of the GRF-OT can inspire evaluation, and subsequent intervention, to strategically create consistent, appropriate, and engaging school recess that impact children's physical, cognitive, social and emotional development.

"And I still remember it to this day": A qualitative exploration of retrospective memories of school-based recess.

Objectives: Previous research has shown the most common memory of physical education (PE) was embarrassment, and that childhood memories of PE relate to physical activity (PA) attitude, intention, and sedentary behavior in adulthood [13]. Recess memories may have a similar effect on adult attitudes towards PA, given that recess is a physically active part of the school day, yet is more autonomous and less supervised than PE. Recent literature has supported this, as Massey and colleagues (2021b) reported memories of recess enjoyment were associated with PA enjoyment in adulthood, whereas negative recess memories were associated with social isolation. In an effort to better understand recess memories, and how they may be related to adult behaviors, the purpose of this study was to examine qualitative descriptions of adults' worst recess memories as it related to physical and social health. Study design: Mixed methods design; inductive content analysis and analysis of covariance. Methods: As part of a larger project, 433 participants between the ages of 19 and 77 (M = 44.91; SD = 15.35) were asked to recall their worst recess memories and the grades in which those memories occurred. Participants identified as predominantly female (52%), White (72%), and college educated (46%). Data analysis was conducted via an inductive content analysis by three research team members. Results: The most common negative memories included isolating experiences, physical injuries, victimization, and contextual factors (e.g., weather). Through a series of analysis of covariance, self-reported isolation and self-efficacy of exercise were significantly related to participants with social isolation and physical injury memories respectively. Conclusions: This study adds to a growing line of research documenting the importance of recess as a developmentally impactful environment with implications for physical and emotional health.

Improving Recess through Collaboration: Exploring the Facilitators and Barriers to Sustaining Positive Playground Behavior.

BACKGROUND: School recess quality is vital to children's social and emotional skill development. However, there is a research-to-practice gap where academic findings are ineffectively translated back to schools. The aims of this study were to examine how a co-designed intervention would impact negative behaviors observed during recess and to explore the facilitators and barriers to recess implementation over the course of a school year. METHODS: Utilizing a research-practice partnership, the authors collaborated with staff at an elementary school to design, implement, and assess an intervention focused on improving recess quality. The intervention offered training in research-supported recess practices through professional development training and teaching students transitions and games. The school's recess behavioral report log of negative playground behaviors across the academic year and notes from recess staff meetings were analyzed. RESULTS: Quantitative results pointed to a stable decrease in negative playground behaviors post-intervention compared to pre-intervention. Qualitative analyses suggest school leadership and practitioners should focus on "reculturing" recess prior to making structural changes, and empowering recess staff to sustain change. CONCLUSION: Prior to considering interventions at recess, there is a need to assess both school and recess culture. In doing so, reculturing around the importance of recess during the school day and the roles of adults in the process is needed to ensure the sustainability of any changes made.

Membrane Bound O-Acyltransferase 7 (MBOAT7) Shapes Lysosomal Lipid Homeostasis and Function to Control Alcohol-Associated Liver Injury.

Several recent genome-wide association studies (GWAS) have identified single nucleotide polymorphism (SNPs) near the gene encoding membrane-bound O -acyltransferase 7 ( MBOAT7 ) that is associated with advanced liver diseases. In fact, a common MBOAT7 variant (rs641738), which is associated with reduced MBOAT7 expression, confers increased susceptibility to non-alcoholic fatty liver disease (NAFLD), alcohol-associated liver disease (ALD), and liver fibrosis in those chronically infected with hepatitis viruses B and C. The MBOAT7 gene encodes a lysophosphatidylinositol (LPI) acyltransferase enzyme that produces the most abundant form of phosphatidylinositol 38:4 (PI 18:0/20:4). Although these recent genetic studies clearly implicate MBOAT7 function in liver disease progression, the mechanism(s) by which MBOAT7-driven LPI acylation regulates liver disease is currently unknown. Previously we showed that antisense oligonucleotide (ASO)-mediated knockdown of Mboat7 promoted non-alcoholic fatty liver disease (NAFLD) in mice (Helsley et al., 2019). Here, we provide mechanistic insights into how MBOAT7 loss of function promotes alcohol-associated liver disease (ALD). In agreement with GWAS studies, we find that circulating levels of metabolic product of MBOAT7 (PI 38:4) are significantly reduced in heavy drinkers compared to age-matched healthy controls. Hepatocyte specific genetic deletion ( Mboat7 HSKO ), but not myeloid-specific deletion ( Mboat7 MSKO ), of Mboat7 in mice results in enhanced ethanol-induced hepatic steatosis and high concentrations of plasma alanine aminotransferase (ALT). Given MBOAT7 is a lipid metabolic enzyme, we performed comprehensive lipidomic profiling of the liver and identified a striking reorganization of the hepatic lipidome upon ethanol feeding in Mboat7 HSKO mice. Specifically, we observed large increases in the levels of endosomal/lysosomal lipids including bis(monoacylglycero)phosphates (BMP) and phosphatidylglycerols (PGs) in ethanol-exposed Mboat7 HSKO mice. In parallel, ethanol-fed Mboat7 HSKO mice exhibited marked dysregulation of autophagic flux and lysosomal biogenesis when exposed to ethanol. This was associated with impaired transcription factor EB (TFEB)-mediated lysosomal biogenesis and accumulation of autophagosomes. Collectively, this works provides new molecular insights into how genetic variation in MBOAT7 impacts ALD progression in humans and mice. This work is the first to causally link MBOAT7 loss of function in hepatocytes, but not myeloid cells, to ethanol-induced liver injury via dysregulation of lysosomal biogenesis and autophagic flux.

The nonvesicular sterol transporter Aster-C plays a minor role in whole body cholesterol balance.

Introduction: The Aster-C protein (encoded by the Gramd1c gene) is an endoplasmic reticulum (ER) resident protein that has been reported to transport cholesterol from the plasma membrane to the ER. Although there is a clear role for the closely-related Aster-B protein in cholesterol transport and downstream esterification in the adrenal gland, the specific role for Aster-C in cholesterol homeostasis is not well understood. Here, we have examined whole body cholesterol balance in mice globally lacking Aster-C under low or high dietary cholesterol conditions. Method: Age-matched Gramd1c +/+ and Gramd1c -/- mice were fed either low (0.02%, wt/wt) or high (0.2%, wt/wt) dietarycholesterol and levels of sterol-derived metabolites were assessed in the feces, liver, and plasma. Results: Compared to wild type controls (Gramd1c +/+) mice, mice lackingGramd1c (Gramd1c -/-) have no significant alterations in fecal, liver, or plasma cholesterol. Given the potential role for Aster C in modulating cholesterol metabolism in diverse tissues, we quantified levels of cholesterol metabolites such as bile acids, oxysterols, and steroid hormones. Compared to Gramd1c +/+ controls, Gramd1c -/- mice had modestly reduced levels of select bile acid species and elevated cortisol levels, only under low dietary cholesterol conditions. However, the vast majority of bile acids, oxysterols, and steroid hormones were unaltered in Gramd1c -/- mice. Bulk RNA sequencing in the liver showed that Gramd1c -/- mice did not exhibit alterations in sterol-sensitive genes, but instead showed altered expression of genes in major urinary protein and cytochrome P450 (CYP) families only under low dietary cholesterol conditions. Discussion: Collectively, these data indicate nominal effects of Aster-C on whole body cholesterol transport and metabolism under divergent dietary cholesterol conditions. These results strongly suggest that Aster-C alone is not sufficient to control whole body cholesterol balance, but can modestly impact circulating cortisol and bile acid levels when dietary cholesterol is limited.

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.