Biology subjects

Maschek, J. A.

Publications and source records attributed to Maschek, J. A..

At least 19 recordsLinked to original sources

bioRxiv2025

Lean breast adipocytes secrete an oxylipin that suppresses breast cancer via ferroptosis

Obesity is predicted to become the largest modifiable risk factor for breast cancer in postmenopausal women, yet the mechanisms underlying this association are unclear. We identified a novel role for the endogenous oxylipin 9S-HODE, secreted by lean adipocytes, to induce ferroptosis in breast cancer cells while sparing normal breast epithelial cells. Obese adipocytes fail to secrete 9S-HODE, suggesting that the loss of ferroptosis induction significantly contributes to the acceleration of obesity-associated breast cancer. Consequently, the inhibition of ferroptosis accelerates breast cancer in lean, but not obese, mice. Further, 9S-HODE inhibits the growth of patient-derived breast cancer organoids, and supplementing 9S-HODE into tumors in obese mice is sufficient to reduce tumor burden, underscoring its potential as a therapeutic agent.

cancer biology↗

bioRxiv2025

Schistosoma mansoni antigen induced innate immune memory features mitochondrial biogenesis and can be inhibited by ovarian produced hormones

We have previously identified that S. mansoni infection induces a unique form of myeloid training that protects male but not female mice from high fat diet induced disease. Here we demonstrate that ovarian derived hormones account for this sex specific difference. Ovariectomy of females prior to infection permits metabolic reprogramming of the myeloid lineage, with BMDM exhibiting carbon source flexibility for cellular respiration, and mice protected from systemic metabolic disease. The innate training phenotype of infection can be replicated by in vivo injection of SEA, and by exposure of bone marrow to SEA in culture prior to macrophage differentiation (Day 0). This protective phenotype is linked to increased chromatin accessibility of lipid and mitochondrial pathways in BMDM including Nrf1 and Tfam, as well as mitochondrial biogenesis. This work provides evidence that S. mansoni antigens induce a unique form of innate training inhibited by ovarian-derived hormones in females.

immunology↗

bioRxiv2024

Semaglutide-induced weight loss improves mitochondrial energy efficiency in skeletal muscle

ObjectiveGlucagon-like peptide 1 receptor agonists (e.g. semaglutide) potently induce weight loss and thereby reducing obesity-related complications. However, weight regain occurs when treatment is discontinued. An increase in skeletal muscle oxidative phosphorylation (OXPHOS) efficiency upon diet-mediated weight loss has been described, which may contribute to reduced systemic energy expenditure and weight regain. We set out to determine the unknown effect of semaglutide on muscle OXPHOS efficiency. MethodsC57BL/6J mice were fed a high-fat diet for 12 weeks before receiving semaglutide or vehicle for 1 or 3 weeks. The rate of ATP production and O2 consumption were measured by a high-resolution respirometry and fluorometry to determine OXPHOS efficiency in skeletal muscle at these 2 timepoints. ResultsSemaglutide treatment led to significant reductions in fat and lean mass. Semaglutide improved skeletal muscle OXPHOS efficiency, measured as ATP produced per O2 consumed (P/O) in permeabilized muscle fibers. Mitochondrial proteomic analysis revealed changes restricted to two proteins linked to complex III assembly (Lyrm7 and Ttc1, p <0.05 without multiple corrections) without substantial changes in the abundance of OXPHOS subunits. ConclusionsThese data indicate that weight loss with semaglutide treatment increases skeletal muscle mitochondrial efficiency. Future studies could test whether it contributes to weight regain.

physiology↗

bioRxiv2024

Cardiolipin deficiency disrupts CoQ redox state and induces steatohepatitis

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a progressive disorder marked by lipid accumulation, leading to metabolic dysfunction-associated steatohepatitis (MASH). A key feature of the transition to MASH involves oxidative stress resulting from defects in mitochondrial oxidative phosphorylation (OXPHOS). Here, we show that pathological alterations in the lipid composition of the inner mitochondrial membrane (IMM) directly instigate electron transfer inefficiency to promote oxidative stress. Specifically, mitochondrial cardiolipin (CL) was downregulated with MASLD/MASH in humans and in mice. Hepatocyte-specific CL synthase knockout (CLS-LKO) led to spontaneous and robust MASH with extensive steatotic and fibrotic phenotype. Loss of CL paradoxically increased mitochondrial respiratory capacity but also promoted electron leak primarily at sites IIIQO and IIF of the electron transport chain, reduced the formation of I+III2+IV respiratory supercomplex, and disrupted the propensity of coenzyme Q (CoQ) to become reduced. Thus, low mitochondrial CL disrupts electron transport chain to promote oxidative stress and contributes to pathogenesis of MASH.

biochemistry↗

bioRxiv2024

Skeletal muscle PGC-1α remodels mitochondrial phospholipidome but does not alter energy efficiency for ATP synthesis

BackgroundExercise training is thought to improve the mitochondrial energy efficiency of skeletal muscle. Some studies suggest exercise training increases the efficiency for ATP synthesis by oxidative phosphorylation (OXPHOS), but the molecular mechanisms are unclear. We have previously shown that exercise remodels the lipid composition of mitochondrial membranes, and some of these changes could contribute to improved OXPHOS efficiency (ATP produced by O2 consumed or P/O). Peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1) is a transcriptional co-activator that coordinately regulates exercise-induced adaptations including mitochondria. We hypothesized that increased PGC-1 activity is sufficient to remodel mitochondrial membrane lipids and promote energy efficiency. MethodsMice with skeletal muscle-specific overexpression of PGC-1 (MCK-PGC-1) and their wildtype littermates were used for this study. Lipid mass spectrometry and quantitative PCR were used to assess muscle mitochondrial lipid composition and their biosynthesis pathway. The abundance of OXPHOS enzymes was determined by western blot assay. High-resolution respirometry and fluorometry analysis were used to characterize mitochondrial bioenergetics (ATP production, O2 consumption, and P/O) for permeabilized fibers and isolated mitochondria. ResultsLipidomic analyses of skeletal muscle mitochondria from wildtype and MCK-PGC-1 mice revealed that PGC-1 increases the concentrations of cone-shaped lipids such as phosphatidylethanolamine (PE), cardiolipin (CL), and lysophospholipids, while decreases the concentrations of phosphatidylcholine (PC), phosphatidylinositol (PI) and phosphatidic acid (PA). However, while PGC-1 overexpression increased the abundance of OXPHOS enzymes in skeletal muscle and the rate of O2 consumption (JO2), P/O values were unaffected with PGC-1 in permeabilized fibers or isolated mitochondria. ConclusionsCollectively, overexpression of PGC-1 promotes the biosynthesis of mitochondrial PE and CL but neither PGC-1 nor the mitochondrial membrane lipid remodeling induced in MCK-PGC-1 mice is sufficient to increase the efficiency for mitochondrial ATP synthesis. These findings suggest that exercise training may increase OXPHOS efficiency by a PGC-1-independent mechanism, and question the hypothesis that mitochondrial lipids directly affect OXPHOS enzymes to improve efficiency for ATP synthesis.

physiology↗

bioRxiv2024

HAF Prevents Hepatocyte Apoptosis and Hepatocellular Carcinoma through Transcriptional Regulation of the NF-κB pathway.

BackgroundHepatocellular carcinoma (HCC) incidence is increasing worldwide due to the obesity epidemic, which drives metabolic dysfunction-associated steatohepatitis (MASH) that can lead to HCC. However, the molecular pathways that lead to MASH-HCC are poorly understood. We have previously reported that male mice with global haploinsufficiency of hypoxia-associated factor, HAF (SART1+/-) spontaneously develop MASH/HCC. However, the cell type(s) responsible for HCC associated with HAF loss are unclear. ResultsSART1-floxed mice were crossed with mice expressing Cre-recombinase within hepatocytes (Alb-Cre; hepS-/-) or macrophages (LysM-Cre, macS-/-). Only hepS-/- mice (both male and female) developed HCC suggesting that HAF protects against HCC primarily within hepatocytes. HAF-deficient macrophages showed decreased P-p65 and P-p50 and in many major components of the NF-{kappa}B pathway, which was recapitulated using HAF siRNA in vitro. HAF depletion increased apoptosis both in vitro and in vivo, suggesting that HAF mediates a tumor suppressor role by suppressing hepatocyte apoptosis. We show that HAF regulates NF-{kappa}B activity by controlling transcription of TRADD and RIPK1. Mice fed a high-fat diet (HFD) showed marked suppression of HAF, P-p65 and TRADD within their livers after 26 weeks, but manifest profound upregulation of HAF, P-65 and TRADD within their livers after 40 weeks of HFD, implicating deregulation of the HAF-NF-{kappa}B axis in the progression to MASH. In humans, HAF was significantly decreased in livers with simple steatosis but significantly increased in HCC compared to normal liver. ConclusionsHAF is novel transcriptional regulator of the NF-{kappa}B pathway that protects against hepatocyte apoptosis and is a key determinant of cell fate during progression to MASH and MASH-HCC.

cancer biology↗

bioRxiv2023

Inhibition of skeletal muscle Lands cycle ameliorates weakness induced by physical inactivity

BackgroundLipid hydroperoxides (LOOH) have been implicated in skeletal muscle atrophy with age and disuse. Lysophosphatidylcholine acyltransferase 3 (LPCAT3), an enzyme of Lands cycle, conjugates a polyunsaturated fatty acyl chain to a lysophospholipid (PUFA-PL) molecule, providing substrates for LOOH propagation. Previous studies suggest that inhibition of Lands cycle is an effective strategy to suppress LOOH. Mice with skeletal muscle-specific tamoxifen-inducible knockout of LPCAT3 (LPCAT3-MKO) were utilized to determine if muscle-specific attenuation of LOOH may alleviate muscle atrophy and weakness with disuse. MethodsLPCAT3-MKO and control mice underwent 7 days of sham or hindlimb unloading (HU model) to study muscle mass and force-generating capacity. LOOH was assessed by quantifying 4-hydroxynonenal (4-HNE)-conjugated peptides. Quantitative PCR and lipid mass spectrometry were used to validate LPCAT3 deletion. Results7 days of HU was sufficient to induce muscle atrophy and weakness concomitant to an increase in 4-HNE. Deletion of LPCAT3 reversed HU-induced increase in muscle 4HNE. No difference was found in body mass, body composition, or caloric intake between genotypes. The soleus (SOL) and plantaris (PLANT) muscles of the LPCAT3-MKO mice were partially protected from atrophy compared to controls, concomitant to attenuated decrease in cross-sectional areas in type I and IIa fibers. Strikingly, SOL and extensor digitorum longus (EDL) were robustly protected from HU-induced reduction in force-generating capacity in the LPCAT3-MKO mice compared to controls. ConclusionOur findings demonstrate that attenuation of muscle LOOH is sufficient to restore skeletal muscle function, in particular a protection from reduction in muscle specific force. Thus, muscle LOOH contributes to atrophy and weakness induced by HU in mice.

physiology↗

bioRxiv2023

Hepatic IRE1 Protects Against Septic Cardiac Failure

SUMMARYMetabolic reprogramming in response to infection plays a critical role for septic survival. During a septic episode, the heart heavily relies on hepatic lipid particles to prevent heart damage and failure. Inositol- Requiring Enzyme 1 (IRE1) is the most conserved unfolded protein response (UPR) regulator that governs homeostasis of the endoplasmic reticulum (ER), the major site for lipid synthesis and processing. Here we show that hepatocyte IRE1 is indispensable for protecting against septic mortality in two different rodent models of experimental sepsis. The protective effect of hepatic IRE1 was not attributed to the inflammatory response since hepatic IRE1 deletion did not alter hepatic or systemic cytokine response. However, loss of IRE1 in the liver significantly augmented septic cardiac dysfunction in part due to a skewed immune-metabolic balance. Lipidomic and metabolomic analyses further revealed that loss of IRE1 in the liver compromised adaptive intrahepatic and circulating lipid reprogramming, including VLDL, in response to septic challenge. Furthermore, we identified that the protective effects against septic mortality are mediated by a non-canonical IRE1-dependent mechanism. Together, our study provides the first insight into how a disruption of hepatic ER-mediated lipid metabolic regulation promotes sepsis-associated cardiac immuno-metabolic imbalance.

pathology↗

bioRxiv2023

Genetic Screen Uncovers a Dual Role for Phospholipids in Mitochondrial-Derived Compartment Biogenesis

Cells utilize multiple mechanisms to maintain mitochondrial homeostasis in response to stress. We recently identified a cellular structure, called the mitochondria-derived compartment (MDC), that is generated from mitochondria in response to amino acid overabundance. MDCs selectively sequester proteins from mitochondria for subsequent degradation, and loss of MDCs sensitizes cells to amino acid stress. Here, we conducted a microscopy-based screen in budding yeast to identify factors that regulate MDC formation. We found that levels of two mitochondrial phospholipids, cardiolipin (CL) and phosphatidylethanolamine (PE), regulate MDC biogenesis in opposing directions. CL depletion impairs MDC biogenesis, whereas PE reduction leads to constitutive MDC formation. Additionally, in response to MDC-inducing agents, cellular and mitochondrial PE declines in an amino acid-dependent manner. Overexpressing mitochondrial PE synthesis pathway components suppresses MDC biogenesis during amino acid stress. Altogether, our data indicate a requirement for CL in MDC biogenesis, and suggest that PE depletion may serve as a regulatory signal for MDC formation downstream of MDC-inducing metabolic stress. SUMMARYXiao et al. identify distinct roles for the phospholipids cardiolipin and phosphatidylethanolamine in mitochondria-derived compartment (MDC) biogenesis. They show that cardiolipin is required for MDC formation, whereas a decline in phosphatidylethanolamine in response to amino acid stress triggers MDC biogenesis.

cell biology↗

bioRxiv2022

Weight loss improves skeletal muscle mitochondrial energy efficiency

Weight loss is associated with a disproportionate decrease in whole-body energy expenditure that may contribute to the heightened risk for weight-regain. Evidence suggests that this energetic mismatch originates from lean tissue. Although this phenomenon is well documented, the mechanisms have remained elusive. We hypothesized that increased mitochondrial energy efficiency in skeletal muscle is associated with reduced expenditure under weight loss. Wildtype male C57BL6/N mice were fed with high-fat diet for 10 wks, followed by a subset of mice that were maintained on the obesogenic diet (OB) or switched to standard chow to promote weight loss (WL) for additional 6 wks. Mitochondrial energy efficiency was evaluated using high-resolution respirometry and fluorometry. Mass spectrometric analyses were employed to describe the mitochondrial proteome and lipidome. Weight loss promoted ~50% increase in the efficiency of oxidative phosphorylation (ATP produced per O2 consumed, or P/O) in skeletal muscle. However, weight loss did not appear to induce significant changes in mitochondrial proteome, nor any changes in respiratory supercomplex formation. Instead, it accelerated the remodeling of mitochondrial cardiolipin (CL) acyl-chains to increase tetralinoleoyl CL (TLCL) content, a species of lipids thought to be functionally critical for the respiratory enzymes. We further show that lowering TLCL by deleting the CL transacylase tafazzin was sufficient to reduce skeletal muscle P/O and protect mice from diet-induced weight gain. These findings implicate skeletal muscle mitochondrial efficiency as a novel mechanism by which weight loss reduces energy expenditure in obesity.

physiology↗

bioRxiv2022

Phosphatidylethanolamine facilitates mitochondrial pyruvate entry to regulate metabolic flexibility

Carbohydrates and lipids provide the majority of substrates to fuel mitochondrial oxidative phosphorylation (OXPHOS). Metabolic inflexibility, defined as an impaired ability to switch between these fuels, is implicated in a number of metabolic diseases. Here we explore the mechanism by which physical inactivity promotes metabolic inflexibility in skeletal muscle. We developed a mouse model of sedentariness by small mouse cage (SMC) that, unlike other classic models of disuse in mice, faithfully recapitulates metabolic responses that occur in humans. Bioenergetic phenotyping of mitochondria displayed metabolic inflexibility induced by physical inactivity, demonstrated by a reduction in pyruvate-stimulated respiration (JO2) in absence of a change in palmitate-stimulated JO2. Pyruvate resistance in these mitochondria was likely driven by a decrease in phosphatidylethanolamine (PE) abundance in the mitochondrial membrane. Reduction in mitochondrial PE by deletion of phosphatidylserine decarboxylase (PSD) was sufficient to induce metabolic inflexibility measured at the whole-body level, as well as at the level of skeletal muscle mitochondria. Low mitochondrial PE was sufficient to increase glucose flux towards lactate. We further implicate that resistance to pyruvate metabolism is due to attenuated mitochondrial entry via mitochondrial pyruvate carrier (MPC). These findings suggest a novel mechanism by which mitochondrial PE directly regulates MPC activity to modulate metabolic flexibility.

physiology↗

bioRxiv2022

Mitochondrial Phosphatidylethanolamine Directly Regulates UCP1 to Promote Brown Adipose Thermogenesis

Thermogenesis by uncoupling protein 1 (UCP1) is one of the primary mechanisms by which brown adipose tissue (BAT) increases energy expenditure. UCP1 resides in the inner mitochondrial membrane (IMM), where it dissipates membrane potential independent of ATP synthase. Here we provide evidence that mitochondrial phosphatidylethanolamine (PE) directly regulates UCP1-dependent proton conductance across IMM to modulate thermogenesis. Mitochondrial lipidomic analyses revealed PE as a signature molecule whose abundance bidirectionally responds to changes in thermogenic burden. Reduction in mitochondrial PE by deletion of phosphatidylserine decarboxylase (PSD) made mice cold intolerant and insensitive to {beta}3 adrenergic receptor agonist-induced increase in whole-body oxygen consumption. High-resolution respirometry and fluorometry of BAT mitochondria showed that loss of mitochondrial PE specifically lowers UCP1-dependent respiration without compromising electron transfer efficiency or ATP synthesis. These findings were confirmed by a reduction in UCP1 proton current in PSD-deficient mitoplasts. Thus, PE performs a previously unknown role as a temperature-responsive rheostat that regulates UCP1-dependent thermogenesis.

biochemistry↗

bioRxiv2022

Disruption of CFAP418 interaction with lipids causes abnormal membrane-associated cellular processes in retinal degenerations

Syndromic ciliopathies and retinal degenerations are large heterogeneous groups of genetic diseases. CFAP418 is a causative gene of both disorders, and its protein sequence is evolutionarily conserved. However, the pathogenic mechanism caused by CFAP418 mutations is largely unknown. Here, we employed affinity purification coupled with mass spectrometry and quantitative lipidomic, proteomic, and phosphoproteomic approaches to address the molecular function of CFAP418 in mouse retinas. We showed that CFAP418 bound to lipid metabolism precursor phosphatidic acid (PA) and mitochondrion-specific lipid cardiolipin but did not form a tight and static complex with proteins. Loss of Cfap418 led to membrane lipid imbalance and protein-membrane association alteration, which subsequently caused mitochondrial defects and membrane remodeling abnormalities in multiple vesicular trafficking pathways. Loss of Cfap418 also increased the activity of PA-binding protein kinase C. Our results indicate that membrane lipid imbalance is a new pathological mechanism underlying syndromic ciliopathies and retinal degenerations, which is associated with other known causative genes for these diseases, such as RAB28 and BBS genes.

cell biology↗

bioRxiv2022

Trade-Offs Between Hepatic Host Defense and Metabolic Programs Underlie Sex-Biased Diseases

Current concepts in evolutionary medicine propose that trade-offs and mismatches with a shifting environment increase disease risk. While biological sex also impacts disease prevalence, contributions of environmental pressures to sex-biased diseases remain unexplored. Here, we show that sex-dependent hepatic programs confer a robust (~300%) survival advantage for male mice during lethal bacterial infection. The transcription factor BCL6, which masculinizes hepatic gene expression at puberty, is essential for this advantage. However, protection by BCL6 comes at a cost following dietary excess, resulting in overt fatty liver and glucose intolerance in males. Deleting hepatic BCL6 reverses these phenotypes but markedly lowers male fitness during infection, thus establishing a sex-dependent tradeoff between host defense and metabolic systems. We suggest that these tradeoffs, coupled with current environmental pressures, drive metabolic disease in males.

physiology↗

bioRxiv2021

Lipid hydroperoxides promote muscle atrophy through lysosomal amplification

Reactive oxygen species (ROS) accumulation is a cardinal feature of skeletal muscle atrophy. ROS refers to a collection of radical molecules whose cellular signals are vast, and it is unclear which downstream consequences of ROS are responsible for the loss of muscle mass and strength. Here we show that lipid hydroperoxides (LOOH) are increased with age and disuse, and the accumulation of LOOH by deletion of glutathione peroxidase 4 (GPx4) is sufficient to augment muscle atrophy. LOOH promoted atrophy in a lysosomal-dependent, proteasomal-independent manner. In young and old mice, genetic and pharmacologic neutralization of LOOH or their secondary reactive lipid aldehydes robustly prevented muscle atrophy and weakness, indicating that LOOH-derived carbonyl stress mediate age- and disuse-induced muscle dysfunction. Our findings provide novel insights for the role of LOOH in sarcopenia including a therapeutic implication by pharmacologic suppression.

physiology↗

bioRxiv2021

S1P controls endothelial sphingolipid homeostasis via ORMDL

Sphingolipids (SL) are both membrane building blocks and potent signaling molecules regulating a variety of cellular functions in both physiological and pathological conditions. Under normal physiology, sphingolipid levels are tightly regulated, whereas disruption of sphingolipid homeostasis and signaling has been implicated in diabetes, cancer, cardiovascular and autoimmune diseases. Yet, mechanisms governing cellular sensing of SL, and according regulation of their biosynthesis remain largely unknown. In yeast, serine palmitoyltransferase (SPT), catalyzing the first and rate limiting step of sphingolipid de novo biosynthesis, is negatively regulated by Orosomucoid 1 and 2 (Orm) proteins. Lowering sphingolipid levels triggers Orms phosphorylation, resulting in the removal of the inhibitory brake on SPT to enhance sphingolipid de novo biosynthesis. However, mammalian orthologs ORMDLs lack the N-terminus hosting the phosphosites. Thus, which sphingolipid(s) are sensed by the cells, and mechanisms of homeostasis remain largely unknown. This study is aimed at filling this knowledge gap. Here, we identify sphingosine-1-phosphate (S1P) as the key sphingolipid sensed by endothelial cells via S1PRs. The increase of S1P-S1PR signaling stabilizes ORMDLs, which downregulates SPT activity to maintain SL homeostasis. These findings reveal the S1PR/ORMDLs axis as the sensor-effector unit regulating SPT activity accordingly. Mechanistically, the hydroxylation of ORMDLs at Pro137 allows a constitutive degradation of ORMDLs via ubiquitin-proteasome pathway, therefore preserving SPT activity at steady state. The disruption of the S1PR/ORMDL axis results in ceramide accrual, mitochondrial dysfunction, and impaired signal transduction, all leading to endothelial dysfunction, which is an early event in the onset of cardio- and cerebrovascular diseases. The disruption of S1P-ORMDL-SPT signaling may be implicated in the pathogenesis of conditions such as diabetes, cancer, cardiometabolic disorders, and neurodegeneration, all characterized by deranged sphingolipid metabolism. Our discovery may provide the molecular basis for a therapeutic intervention to restore sphingolipid homeostasis.

cell biology↗

bioRxiv2021

Critical Role for Isoprenoids in Apicoplast Biogenesis by Malaria Parasites

Isopentenyl pyrophosphate (IPP) is an essential metabolic output of the apicoplast organelle in Plasmodium falciparum malaria parasites and is required for prenylation-dependent vesicular trafficking and other cellular processes. We have elucidated a critical and previously uncharacterized role for IPP in apicoplast biogenesis. Inhibiting IPP synthesis blocks apicoplast elongation and inheritance by daughter merozoites, and apicoplast biogenesis is rescued by exogenous IPP and polyprenols. Knockout of the only known isoprenoid-dependent apicoplast pathway, tRNA prenylation by MiaA, has no effect on blood-stage parasites and thus cannot explain apicoplast reliance on IPP. However, we have localized an annotated polyprenyl synthase (PPS) to the apicoplast lumen. PPS knockdown is lethal to parasites, rescued by IPP, and blocks apicoplast biogenesis, thus explaining apicoplast dependence on isoprenoid synthesis. We hypothesize that PPS synthesizes long-chain polyprenols critical for apicoplast membrane fluidity and biogenesis. This work critically expands the paradigm for isoprenoid utilization in malaria parasites and identifies a novel essential branch of apicoplast metabolism suitable for therapeutic targeting.

microbiology↗

bioRxiv2020

Serine Palmitoyltransferase Controls Stemness of Intestinal Progenitors

Cancers of the gastrointestinal tract including esophageal adenocarcinomas, colorectal cancers, and cancers of the gastric cardia are common comorbidities of obesity. Excessive delivery of macronutrients to the cells lining the gut can increase ones risk for these cancer by inducing imbalances in the rate of intestinal stem cell proliferation vs. differentiation, which can produce polyps and other aberrant growths. We demonstrate that serine palmitoyltransferase (SPT), which diverts dietary fatty and amino acids into the sphingolipid biosynthesis pathway, is a critical modulator of intestinal stem cell homeostasis. SPT and other enzymes in the biosynthetic pathway are upregulated in human colon tumors. These enzymes produce sphingolipids that serve as pro-stemness signals that stimulate peroxisome-proliferator activated receptor alpha (PPAR)-mediated induction of fatty acid binding protein-1. This increases fatty acid uptake and oxidation and enhances the stemness program. Serine palmitoyltransferase thus serves as a critical link between dietary macronutrients, epithelial regeneration, and cancer risk.

cell biology↗