Biology subjects

Chang, M.

Publications and source records attributed to Chang, M..

At least 55 records · Page 3Linked to original sources

bioRxiv2023

Detecting altered hepatic lipid oxidation by MRI in an animal model of NAFLD

Nonalcoholic fatty liver disease (NAFLD) prevalence is increasing annually and affects over a third of U.S. adults. NAFLD can progress to nonalcoholic steatohepatitis (NASH), characterized by severe inflammation and fibrosis. NASH is predicted to become the primary cause of liver transplant by 2030. Although the etiology of NAFLD/NASH is incompletely understood, dysregulated fatty acid oxidation is implicated in disease pathogenesis. Here, we developed a method for estimating hepatic {beta}-oxidation from the metabolism of [D15]octanoate to deuterated water and detection with deuterium magnetic resonance methods. Application of this method to perfused liver from a mouse model of NAFLD revealed dysregulated hepatic {beta}-oxidation, findings that we confirmed with in vivo imaging. The high-fat diet-induced NAFLD mouse studies indicated that decreased {beta}-oxidative efficiency in the fatty liver could serve as a prognostic indicator of NAFLD progression. Furthermore, our method provides a clinically translatable imaging approach for determining hepatic {beta}-oxidation efficiency.

biochemistry↗

bioRxiv2023

Exuberant de novo dendritic spine growth in mature neurons

Dendritic spines are structural correlates of excitatory synapses maintaining stable synaptic communications. However, this strong spine-synapse relationship was mainly characterized in excitatory pyramidal neurons (PyNs), raising a possibility that inferring synaptic density from dendritic spine number may not be universally applied to all neuronal types. Here we found that the ectopic expression of H-Ras increased dendritic spine numbers regardless of cortical cell types such as layer 2/3 pyramidal neurons (PyNs), parvalbumin (PV)- and vasoactive intestinal peptide (VIP)-positive interneurons (INs) in the primary motor cortex (M1). The probability of detecting dendritic spines was positively correlated with the magnitude of H-Ras activity, suggesting elevated local H-Ras activity is involved in the process of dendritic spine formation. H-Ras overexpression caused high spine turnover rate via adding more spines rather than eliminating them. Two-photon photolysis of glutamate triggered de novo dendritic spine formation in mature neurons, suggesting H-Ras induced spine formation is not restricted to the early development. In PyNs and PV-INs, but not VIP-INs, we observed a shift in average spine neck length towards longer filopodia-like phenotypes. The portion of dendritic spines lacking key excitatory synaptic proteins were significantly increased in H-Ras transfected neurons, suggesting that these increased spines have other distinct functions. High spine density caused by H-Ras did not result in change in the frequency or the amplitude of miniature excitatory postsynaptic currents (mEPSCs). Thus, our results propose that dendritic spines possess more multifaceted functions beyond the morphological proxy of excitatory synapse.

neuroscience↗

bioRxiv2023

Unrecognized Potent Activities of Colistin Against Clinically Important mcr+ Enterobacteriaceae Revealed in Synergy with Host Immunity

Colistin (COL) is a cationic cyclic peptide that disrupts negatively-charged bacterial cell membranes and frequently serves as an antibiotic of last resort to combat multidrug-resistant Gram-negative bacterial infections. Emergence of the horizontally transferable plasmid-borne mobilized colistin resistance (mcr) determinant and its spread to Gram-negative strains harboring extended-spectrum {beta}-lactamase and carbapenemase resistance genes threatens futility of our chemotherapeutic arsenal. COL is widely regarded to have zero activity against mcr+ patients based on standard antimicrobial susceptibility testing (AST) performed in enriched bacteriological growth media; consequently, the drug is withheld from patients with mcr+ infections. However, these standard testing media poorly mimic in vivo physiology and omit host immune factors. Here we report previously unrecognized bactericidal activities of COL against mcr-1+ isolates of Escherichia coli (EC), Klebsiella pneumoniae (KP), and Salmonella enterica (SE) in standard tissue culture media containing the physiological buffer bicarbonate. Moreover, COL promoted serum complement deposition on the mcr-1+ Gram-negative bacterial surface and synergized potently with active human serum in pathogen killing. At COL concentrations readily achievable with standard dosing, the peptide antibiotic killed mcr-1+ EC, KP, and SE in freshly isolated human blood proved effective as monotherapy in a murine model of mcr-1+ EC bacteremia. Our results suggest that COL, currently ignored as a treatment option based on traditional AST, may in fact benefit patients with mcr-1+ Gram negative infections based on evaluations performed in a more physiologic context. These concepts warrant careful consideration in the clinical microbiology laboratory and for future clinical investigation of their merits in high risk patients with limited therapeutic options.

microbiology↗

bioRxiv2023

An adaptive behavioral control motif mediated by cortical axo-axonic inhibition

Neural circuits are reorganized with specificity during learning. Genetically-defined subgroups of inhibitory interneurons are thought to play distinct roles in learning, but heterogeneity within these subgroups has limited our understanding of the scope and nature of their specific contributions to learning. Here we reveal that the chandelier cell (ChC), an interneuron type that specializes in inhibiting the axon-initial segment (AIS) of pyramidal neurons, establishes cortical microcircuits for organizing neural coding through selective axo-axonic synaptic plasticity. We find that organized motor control is mediated by enhanced population coding of direction-tuned premotor neurons, whose tuning is refined through suppression of irrelevant neuronal activity. ChCs are required for learning-dependent refinements via providing selective inhibitory control over pyramidal neurons rather than global suppression. Quantitative analysis on structural plasticity of axo-axonic synapses revealed that ChCs redistributed inhibitory weights to individual pyramidal neurons during learning. These results demonstrate an adaptive logic of the inhibitory circuit motif responsible for organizing distributed neural representations. Thus, ChCs permit efficient cortical computation in a target cell specific manner, which highlights the significance of interneuron diversity.

neuroscience↗

bioRxiv2023

Early retinal deprivation crossmodally alters nascent subplate circuits and activity in the auditory cortex during the precritical period

Sensory perturbation in one modality results in adaptive reorganization of neural pathways within the spared modalities, a phenomenon known as "crossmodal plasticity", which has been examined during or after the classic critical period. Because peripheral perturbations can alter auditory cortex (ACX) activity and functional connectivity of the ACX subplate neurons (SPNs) even before the classic critical period, called the precritical period, we investigated if retinal deprivation at birth crossmodally alters ACX activity and SPN circuits during the precritical period. We deprived newborn mice of visual inputs after birth by performing bilateral enucleation. We performed in vivo imaging in the ACX of awake pups during the first two postnatal weeks to investigate cortical activity. We found that enucleation alters spontaneous and sound-evoked activity in the ACX in an age-dependent manner. Next, we performed whole-cell patch clamp recording combined with laser scanning photostimulation in ACX slices to investigate circuit changes in SPNs. We found that enucleation alters the intracortical inhibitory circuits impinging on SPNs shifting the excitation-inhibition balance towards excitation and this shift persists after ear opening. Together, our results indicate that crossmodal functional changes exist in the developing sensory cortices at early ages before the onset of the classic critical period.

neuroscience↗

bioRxiv2023

Deletion of MEC1 suppresses replicative senescence of the cdc13-2 mutant in Saccharomyces cerevisiae

In Saccharomyces cerevisiae, telomerase recruitment to telomeres depends on a direct interaction between Cdc13, a protein that binds single-stranded telomeric DNA, and the Est1 subunit of telomerase. The cdc13-2 allele disrupts telomerase association with telomeres, resulting in progressive telomere shortening and replicative senescence. The Mec1/ATR kinase is both a positive and negative regulator of telomerase activity, and is required for the cell cycle arrest in telomerase-deficient senescent cells. In this study, we find that deletion of MEC1 suppresses the replicative senescence of cdc13-2. This suppression is dependent on telomerase, indicating that Mec1 antagonizes telomerase-mediated telomere extension in cdc13-2 cells to promote senescence.

molecular biology↗

bioRxiv2023

Neural characterization of the "totonou" state associated with sauna use

Saunas are becoming increasingly popular worldwide, being an activity that promotes relaxation and health. Intense feelings of happiness have been reported shortly after enjoying a hot sauna and cold water, what is known in Japan as the "totonou" state. However, no research has investigated what occurs in the brain during the "totonou" state. In the present study, participants underwent a sauna phase, consisting of three sets of alternating hot sauna, cold water, and rest. We elucidated changes in brain activity and mood in the "totonou" state by measuring and comparing brain activity and emotional scales before and after the sauna phase and during the rest phase in each set. We found significant increases in theta and alpha power during rest and after the sauna phase compared to before the sauna phase. Moreover, in an auditory oddball task, the p300 amplitude decreased significantly and MMN amplitude increased significantly after the sauna phase. The increase in MMN indicates higher activation of the pre-attentional auditory process, leading to a decrease in attention-related brain activity P300. Hence, the brain reaches in a more efficient state. Further, the response time in behavioral tasks decreased significantly. In addition, the participants subjective responses to the questionnaire showed significant changes in physical relaxation and other indicators after being in the sauna. Finally, we developed an artificial intelligence classifier, obtaining an average accuracy of brain state classification of 88.34%. The results have potential for future application.

neuroscience↗

bioRxiv2022

Self-regulation of PIN1-driven auxin transport by cell surface-based auxin signaling in Arabidopsis

PIN-FORMED (PIN)-driven auxin transport contributes to establishing and maintaining a dynamic auxin concentration gradient alongside plant tissues, which drives the majority of developmental processes in plants. To maintain developmental plasticity in ever-changing environments, plants have evolved self-organizing feedback machinery between auxin signaling and its transport, which has been shown to play essential roles in many fundamental plant processes. However, the molecular mechanism behind this mutual regulation has not yet been clarified. Here, we identified a cell surface-triggered auxin signaling that regulates the PIN1-mediated auxin efflux and further developmental patterning in Arabidopsis. Auxin was able to stimulate PIN1 phosphorylation in plants through transmembrane kinases (TMKs), key components in auxin signaling, at the plasma membrane. TMK1 and TMK4 directly interacted with and phosphorylated PIN1 and functioned redundantly in the regulation of PIN1 polarity in plant cells. The phosphorylation sites in PIN1 proteins, targeted by both auxin and TMKs, were required for PIN1 trafficking and polarity, which further controlled auxin responses and downstream developmental patterning in Arabidopsis. Therefore, our findings provide a direct mechanism for the self-regulation between auxin signaling and transport that drives the auxin flows and proper development in plants.

plant biology↗

bioRxiv2022

Mesoscopic oblique plane microscopy (Meso-OPM) - enabling large-scale 4D isotropic cellular resolution imaging with a diffractive light sheet

Fundamental understanding of large-scale dynamic connectivity within a living organism requires volumetric imaging over a large field of view (FOV) at biologically relevant speed and resolution. However, most microscopy methods make trade-offs between FOV and depth resolution, making it challenging to observe highly dynamic processes at cellular resolution in 3D across mesoscopic scales (e.g., whole zebrafish larva). To overcome this limitation, we have developed mesoscopic oblique plane microscopy (Meso-OPM) with a diffractive light sheet. By augmenting the illumination angle of the light sheet with a transmission grating, the axial resolution was improved ~6-fold over existing methods and ~2-fold beyond the diffraction limitation of the primary objective lens. We demonstrated an unprecedented FOV up to 5.4 x 3.3 mm with resolution of 2.5x 3 x 6 m, allowing volumetric imaging of 3D cellular structures with a single scan. Applying Meso-OPM for in vivo imaging of zebrafish larvae, we report here the first in toto whole body volumetric recordings of neuronal activity at 2 Hz volume rate and the first example of whole body volumetric recordings of blood flow dynamics at 5 Hz with 3D cellular resolution.

bioengineering↗

bioRxiv2021

A Substrate-triggered μ-Peroxodiiron(III) Intermediate in the 4-Choro-L-Lysine-Fragmenting Heme-Oxygenase-like Diiron Oxidase (HDO) BesC: Substrate Dissociation from, and C4 Targeting by, the Intermediate

The enzyme BesC from the {beta}-ethynyl-L-serine biosynthetic pathway in Streptomyces cattleya fragments 4-chloro-L-lysine (produced from L-Lysine by BesD) to ammonia, formaldehyde, and 4-chloro-L-allylglycine and can analogously fragment L-Lys itself. BesC belongs to the emerging family of O2-activating non-heme-diiron enzymes with the "heme-oxygenase-like" protein fold (HDOs). Here we show that binding of L-Lys or an analog triggers capture of O2 by the proteins diiron(II) cofactor to form a blue {micro}-peroxodiiron(III) intermediate analogous to those previously characterized in two other HDOs, the olefin-installing fatty acid decarboxylase, UndA, and the guanidino-N-oxygenase domain of SznF. The [~] 5- and [~] 30-fold faster decay of the intermediate in reactions with 4-thia-L-Lys and (4RS)-chloro-DL-lysine than in the reaction with L-Lys itself, and the primary deuterium kinetic isotope effects (D-KIEs) on decay of the intermediate and production of L-allylglycine in the reaction with 4,4,5,5-[2H]-L-Lys, imply that the peroxide intermediate or a successor complex with which it reversibly interconverts initiates the oxidative fragmentation by abstracting hydrogen from C4. Surprisingly, the sluggish substrate L-Lys can dissociate after triggering the intermediate to form, thereby allowing one of the better substrates to bind and react. Observed linkage between Fe(II) and substrate binding suggests that the triggering event involves a previously documented (in SznF) ordering of the dynamic HDO architecture that contributes one of the iron sites, a hypothesis consistent with the observation that the diiron(III) product cluster produced upon decay of the intermediate spontaneously degrades, as it has been shown to do in all other HDOs studied to date.

biochemistry↗

bioRxiv2021

Modeling Western Pacific Amyotrophic Lateral Sclerosis and Parkinsonism dementia Complex with Microglia Containing Cerebral Organoids Derived from Induced Pluripotent Stem Cells

Western Pacific Amyotrophic Lateral Sclerosis and Parkinsonism-dementia Complex (ALS-PDC) is a neurodegenerative disease linked to the traditional consumption of cycad seeds by the Chamorro people of Guam. Little is known about the etiological role of cycad toxin in ALS-PDC. Patient-derived induced pluripotent stem cells were derived from age- and sex-matched affected and unaffected patient lymphoid cells then differentiated into cerebral organoids. After three months, the ALS-PDC affected organoids were smaller, their neurons had less extensive neurite outgrowth, and the organoids had more reactive astrocytes and M1 microglia, fewer resting and M2 microglia, and more open extracellular space. Most of these phenomena could be recapitulated by exposing unaffected organoids to {beta}-methylamino L-alanine (BMAA), a toxic amino acid produced by cyanobacteria living with cycad plants. Furthermore, ALS-PDC affected organoids exhibited an exacerbated neuroinflammatory response to BMAA exposure via activation of caspase1/NLRP3 inflammasome. A genome-wide transcriptome analysis of the organoids showed that the most down-regulated pathways were taurine, alanine, aspartate, and glutamate metabolism; protein digestion; and absorption. The most down-regulated biological processes were type I interferon signaling, regulation of neuron differentiation and extracellular matrix organization. Our results suggested that the etiology of ALS-PDC is due to metabolic disorders that shifted microglia to a more pro-inflammatory M1 state instead of a non-inflammatory, repairing M2 state, which exacerbated inflammation and reduced extracellular matrix strength. Supplementation of transforming growth factor beta (TGF-{beta}) to ALS-PDC affected organoids increased the expression of interferon-induced transmembrane proteins (IFITMs) and restored M2 microglia populations and extracellular matrix organization. Organoids containing networks of neurons, astrocytes, microglia derived from iPSC with our protocol provides an excellent cellular model for neurodegenerative disease modeling. Significance StatementO_LIWestern Pacific Amyotrophic Lateral Sclerosis and Parkinsonism-dementia Complex (ALS-PDC) cerebral organoids containing networks of neurons, astrocytes, and microglia were generated from patient specific lymphoid derived induced pluripotent stem cells. C_LIO_LIALS-PDC affected organoids were smaller, with neurons had less extensive neurite outgrowth, more reactive astrocytes and M1 microglia, fewer resting and M2 microglia, and more open extracellular matrix spaces when compared to ALS-PDC unaffected organoids. C_LIO_LIGenome-wide transcriptome analysis indicated that ALS/PDC affected organoids had significantly lower expression of genes related to vitamin B6, amino acid and protein glycation metabolisms, down-regulated type I interferon signaling, the regulation of neuron differentiation and extracellular matrix production. C_LIO_LIOur results implicated that the etiology of ALS-PDC is due to metabolic disorders that led the shift of microglia to more pro-inflammatory M1 state and less non-inflammatory resting, repairing M2 state of microglia subpopulation, which primed the exacerbated inflammation and reduced extracellular matrix strength. TGF-{beta} promoted interferon-induced transmembrane protein (IFITMs) expression and restored the repairing M2 state of microglia population and extracellular matrix organization. C_LI

neuroscience↗

bioRxiv2021

A synthetic lethal screen identifies HDAC4 as a potential target in MELK overexpressing cancers

Maternal embryonic leucine zipper kinase (MELK) is frequently overexpressed in cancer, but the role of MELK in cancer is still poorly understood. MELK was shown to have roles in many cancer-associated processes including tumor growth, chemotherapy resistance, and tumor recurrence. To determine whether the frequent overexpression of MELK can be exploited in therapy, we performed a high-throughput screen using a library of Saccharomyces cerevisiae mutants to identify genes whose functions become essential when MELK is overexpressed. We identified two such genes: LAG2 and HDA3. LAG2 encodes an inhibitor of the SCF ubiquitin-ligase complex, while HDA3 encodes a subunit of the HDA1 histone deacetylase complex. We find that one of these synthetic lethal interactions is conserved in mammalian cells, as inhibition of a human homolog of HDA3 (HDAC4) is synthetically toxic in MELK overexpression cells. Altogether, our work might provide a new angle of how to exploit MELK overexpression in cancers and might thus lead to novel intervention strategies.

genetics↗

bioRxiv2021

Aplp1 and the Aplp1-Lag3 Complex facilitates transmission of pathologic alpha-synuclein

Pathologic -synuclein (-syn) spreads from cell-to-cell, in part, through binding to the lymphocyte-activation gene 3 (Lag3). Here we report that amyloid {beta} precursor-like protein 1 (Aplp1) forms a complex with Lag3 that facilitates the binding, internalization, transmission, and toxicity of pathologic -syn. Deletion of both Aplp1 and Lag3 eliminates the loss of dopaminergic neurons and the accompanying behavioral deficits induced by -syn preformed fibrils (PFF). Anti-Lag3 prevents the internalization of -syn PFF by disrupting the interaction of Aplp1 and Lag3, and blocks the neurodegeneration induced by -syn PFF in vivo. The identification of Aplp1 and the interplay with Lag3 for -syn PFF induced pathology advances our understanding of the molecular mechanism of cell-to-cell transmission of pathologic -syn and provides additional targets for therapeutic strategies aimed at preventing neurodegeneration in Parkinsons disease and related -synucleinopathies. One Sentence SummaryAplp1 forms a complex with Lag3 that facilitates the binding, internalization, transmission, and toxicity of pathologic -synuclein. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=94 SRC="FIGDIR/small/442157v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@1d746bforg.highwire.dtl.DTLVardef@65acb2org.highwire.dtl.DTLVardef@12cf2f0org.highwire.dtl.DTLVardef@19d6e_HPS_FORMAT_FIGEXP M_FIG Aplp1 and the Aplp1-Lag3 complex facilitates transmission of pathologic -synuclein. Aplp1 is a receptor that drives pathologic -syn transmission, and genetic depletion of Aplp1 can significantly reduce the -synuclein pathogenesis. Aplp1 and Lag3 forms an Aplp1-Lag3 complex that accounts for substantial binding of pathologic -syn to cortical neurons. Together Aplp1 and Lag3 play a major role in pathologic -syn internalization, transmission and toxicity. Double knockout of Aplp1 and Lag3 and or a Lag3 antibody that disrupts the Aplp1 and Lag3 complex almost completely blocks -syn PFF-induced neurodegeneration. C_FIG

neuroscience↗

bioRxiv2021

Suppression of cdc13-2-associated senescence by pif1-m2 requires Ku-mediated telomerase recruitment

In Saccharomyces cerevisiae, recruitment of telomerase to telomeres requires an interaction between Cdc13, which binds single-stranded telomeric DNA, and the Est1 subunit of telomerase. A second pathway involving an interaction between the yKu complex and telomerase RNA (TLC1) contributes to telomerase recruitment, but cannot sufficiently recruit telomerase on its own to prevent replicative senescence when the primary Cdc13-Est1 pathway is abolished--for example, in the cdc13-2 mutant. In this study, we find that mutation of PIF1, which encodes a helicase that inhibits telomerase, suppresses the replicative senescence of cdc13-2 increasing reliance on the yKu-TLC1 pathway for telomerase recruitment. Our findings reveal new insight into telomerase-mediated telomere maintenance.

molecular biology↗

bioRxiv2021

Transmembrane Kinases are essential for plant development

Transmembrane kinase family proteins (TMKs) have been implicated in regulating both auxin signaling and plant development. To obtain insights of the potential TMKs function in plant development, we regenerated new full sets of tmk mutants, and discovered many new phenotypes, such as defective organogenesis, smaller rosette leaves, fertility defects and selfing population defects in different combination of tmk mutants. Taken together, our results demonstrated that TMKs participated in multiple aspects of plant development, which provided a great reference for any future research. One-sentence summaryMultiple tmk mutants analysis illustrated the key roles of TMKs in plant development.

plant biology↗

bioRxiv2021

Identification of gene products involved in plant colonization by Pantoea sp. YR343 using a diguanylate cyclase expressed in the presence of plants

Microbial colonization of plant roots is a highly complex process that requires the coordination and regulation of many gene networks, yet the functions of many of these gene products remain poorly understood. Pantoea sp. YR343, a gamma-proteobacterium isolated from the rhizosphere of Populus deltoides, forms robust biofilms along the root surfaces of Populus and possesses plant growth-promoting characteristics. The mechanisms governing biofilm formation along plant roots by bacteria, including Pantoea sp. YR343, are not fully understood and many genes involved in this process have yet to be discovered. In this work, we identified three diguanylate cyclases in the plant-associated microbe Pantoea sp. YR343 that are expressed in the presence of plant roots, One of these diguanylate cyclases, DGC2884 localizes to discrete sites in the cells and its overexpression results in reduced motility and increased EPS production and biofilm formation. We then performed a genetic screen by expressing this diguanylate cyclase from an inducible promoter in order to identify candidate downstream effectors of c-di-GMP signaling which may be involved in root colonization by Pantoea sp. YR343. Further, we demonstrate the importance of other domains in DGC2884 to its activity, which in combination with the genes identified by transposon mutagenesis, may yield insights into activity and regulation of homologous enzymes in medically and agriculturally relevant microbes.

microbiology↗

bioRxiv2020

Rap1, Rif2, and the Ku complex work in concert to cap chromosome ends

Rap1 is the main protein that binds double-stranded telomeric DNA in Saccharomyces cerevisiae. Examination of the telomere functions of Rap1 is complicated by the fact that it also acts as a transcriptional regulator of hundreds of genes and is encoded by an essential gene. In this study, we disrupt Rap1 telomere association by expressing a mutant telomerase RNA subunit (tlc1-tm) that introduces mutant telomeric repeats. tlc1-tm cells grow similar to wild-type cells, although depletion of Rap1 at telomeres causes defects in telomere length regulation and telomere capping. Rif2 is a protein normally recruited to telomeres by Rap1, but we show that Rif2 can still associate with Rap1-depleted tlc1-tm telomeres, and that this association is required to inhibit telomere degradation by the MRX complex. We find that Rap1, Rif2, and the Ku complex work in parallel to prevent telomere degradation, and absence of all three at telomeres causes lethality. The partially redundant mechanisms may explain the rapid evolution of telomere components in budding yeast species.

molecular biology↗

bioRxiv2020

Metabolic flux signatures of the ER unfolded protein response in vivo reveal decreased hepatic de novo lipogenesis and mobilization of lipids from adipose tissue to liver

The unfolded protein response in the endoplasmic reticulum (UPRER) is involved in a number of metabolic diseases, including non-alcoholic fatty liver disease. Here, we characterize the UPRER induced metabolic changes in mouse liver through in vivo metabolic labeling and mass spectrometric analysis of proteome and lipid fluxes. We induced ER stress in vivo via tunicamycin treatment and measured rates of proteome-wide protein synthesis, de novo lipogenesis and cholesterol synthesis serially over a three-day period, thereby generating a metabolic "signature" of the UPRER over time. Synthesis of most proteins was suppressed under ER stress conditions, including proteins involved in lipogenesis, consistent with reduced de novo lipogenesis at 48 and 72 hours. Electron microscopy revealed striking morphological changes to ER and H&E staining showed lipid droplet enriched livers under ER stress. Pre-labeling of adipose tissue prior to ER stress induction revealed mobilization of lipids from adipose to the liver. Interestingly, the source of these lipids was uptake of free fatty acids, not whole triglycerides or phospholipids from lipoproteins, as demonstrated by replacement of the triglyceride-glycerol moiety in liver concurrently with increased incorporation of labeled palmitate from adipose. We also induced ER stress by a high-fat diet and observed similar metabolic flux signatures, suggesting that this mechanism may play a role in the progression of fatty liver disease. This flux-based approach provides a powerful tool to identify novel regulators of ER stress and potential targets for pharmacological intervention.

physiology↗