Transcriptomics informs design of a planar human enterocyte culture system that reveals metformin enhances fatty acid flux
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ABSTRACT: Background & Aims: Absorption, metabolism, and secretion of lipids occurs in the small intestinal epithelium. Caco-2 and organoids have been used to study these processes but are limited in physiological relevance or preclude simultaneous apical and basal access. Here, we develop a dynamic and flexible planar absorptive enterocyte (AE) monolayer system, investigate how fatty acid oxidation (FAO) regulates FA mobilization mechanisms and probe a role for metformin in FA mobilization. Methods: Single-cell RNA-sequencing (scRNAseq) was performed on primary human jejunum. Transcriptomic signatures and trajectory analysis defined in vivo AE maturational signatures, which informed culture methods to differentiate ISCs and mimic in vivo AEs. The system was scaled for high-throughput drug screening and FAO was pharmacologically modulated. BODIPY (B)-labelled fatty acids (FAs) were used to easily and sensitively evaluate FA handling via fluorescence, and thin layer chromatography (TLC). Results: scRNAseq shows increasing expression of lipid-handling genes as AEs mature. In vitro, ISCs differentiate into AEs that mimic the in vivo maturational program, exhibit strong barrier function and express FA-handling genes. FA synthase inhibitor, C75, increased apical to basolateral mobilization of B-C16. Short-chain FA (B-C5) was unaffected and diffused freely through AEs. FAO inhibitor, etomoxir, decreased apical to basolateral mobilization of medium and long chain FAs (B-C12, B-C16) whereas anti-diabetic drug, metformin, augmented this mobilization. Conclusions: Primary human ISCs in culture undergo programmed maturation in vitro to generate a sensitive culture system of absorptive epithelium to investigate FA-handling. Modulating FAO impacts mobilization of FAs across absorptive epithelium and FAO enhanced by metformin increases basolateral mobilization pointing to an intestine-specific role.
Project description:Obesity is an established risk factor for cancer in many tissues such as the gastrointestinal tract. In the mammalian intestine, a pro-obesity high fat diet (HFD) promotes tumorigenesis in part by enhancing intestinal stem cell (ISC) numbers, proliferation and function. Although Ppar (Peroxisome proliferator-activated receptor) nuclear receptor activity has been proposed to mediate some of these effects in HFD ISCs, the exact role that different Ppar family members play in this process is unclear. Here, we find that in loss-of-function in vivo models, both Ppar family members alpha and delta contribute to the HFD response in ISCs. Mechanistically, both PPARs do so by robustly inducing a downstream fatty acid oxidation (FAO) metabolic program. Notably, pharmacologic and genetic disruption of CPT1a (the rate limiting enzyme of FAO) blunts the HFD phenotype in ISCs. Furthermore, just as HFD ISCs depend on CPT1a-mediated FAO, inhibition of CPT1a dampens the pro-tumorigenic consequences of a HFD on early tumor incidence and progression in the intestine. These findings demonstrate that inhibition of a HFD activated FAO program creates a therapeutic opportunity to counter the effects of a HFD on ISCs and intestinal tumorigenesis.
Project description:Obesity is an established risk factor for cancer in many tissues such as the gastrointestinal tract. In the mammalian intestine, a pro-obesity high fat diet (HFD) promotes tumorigenesis in part by enhancing intestinal stem cell (ISC) numbers, proliferation and function. Although Ppar (Peroxisome proliferator-activated receptor) nuclear receptor activity has been proposed to mediate some of these effects in HFD ISCs, the exact role that different Ppar family members play in this process is unclear. Here, we find that in loss-of-function in vivo models, both Ppar family members alpha and delta contribute to the HFD response in ISCs. Mechanistically, both PPARs do so by robustly inducing a downstream fatty acid oxidation (FAO) metabolic program. Notably, pharmacologic and genetic disruption of CPT1a (the rate limiting enzyme of FAO) blunts the HFD phenotype in ISCs. Furthermore, just as HFD ISCs depend on CPT1a-mediated FAO, inhibition of CPT1a dampens the pro-tumorigenic consequences of a HFD on early tumor incidence and progression in the intestine. These findings demonstrate that inhibition of a HFD activated FAO program creates a therapeutic opportunity to counter the effects of a HFD on ISCs and intestinal tumorigenesis.
Project description:Obesity is an established risk factor for cancer in many tissues such as the gastrointestinal tract. In the mammalian intestine, a pro-obesity high fat diet (HFD) promotes tumorigenesis in part by enhancing intestinal stem cell (ISC) numbers, proliferation and function. Although Ppar (Peroxisome proliferator-activated receptor) nuclear receptor activity has been proposed to mediate some of these effects in HFD ISCs, the exact role that different Ppar family members play in this process is unclear. Here, we find that in loss-of-function in vivo models, both Ppar family members alpha and delta contribute to the HFD response in ISCs. Mechanistically, both PPARs do so by robustly inducing a downstream fatty acid oxidation (FAO) metabolic program. Notably, pharmacologic and genetic disruption of CPT1a (the rate limiting enzyme of FAO) blunts the HFD phenotype in ISCs. Furthermore, just as HFD ISCs depend on CPT1a-mediated FAO, inhibition of CPT1a dampens the pro-tumorigenic consequences of a HFD on early tumor incidence and progression in the intestine. These findings demonstrate that inhibition of a HFD activated FAO program creates a therapeutic opportunity to counter the effects of a HFD on ISCs and intestinal tumorigenesis.
Project description:Endothelial cell (EC) CD36 controls tissue fatty acid (FA) uptake. Here we examined how ECs transfer FAs. FA interaction with apical membrane CD36 induced Src phosphorylation of caveolin-1 tyrosine-14 (Cav-1Y14) and ceramide generation in caveolae. Fission of the caveolae yielded vesicles containing FAs, CD36 and ceramide that were secreted basolaterally as small (80-100nm) exosome-like extracellular vesicles (sEVs). We visualized EC transfer of FAs in sEVs to underlying myotubes in transwells. In mice with EC-expression of the exosome marker emeraldGFP-CD63, muscle fibers accumulated circulating FAs in emGFP-labeled puncta. The FA-sEV pathway was mapped through its suppression by CD36 depletion, blocking actin-remodeling, Src inhibition, Cav-1Y14 mutation, and neutral sphingomyelinase 2 inhibition. Suppression of sEV formation in mice reduced muscle FA uptake, raised circulating FAs, which remained in blood vessels, and lowered glucose, mimicking prominent Cd36-/- phenotypes. The findings show that FA uptake influences membrane ceramide, endocytosis, and EC communication with parenchymal cells.
Project description:The subcellular localization of mRNAs plays a pivotal role in biological processes, including cell migration. For instance, β-actin mRNA and its associated RNA binding protein (RBP), ZBP1/IGF2BP1, are recruited to focal adhesions (FAs), to support localized β-actin synthesis, crucial for cell migration. However, whether other mRNAs and RBPs also localize at FAs remains unclear. Here, we identify hundreds of mRNAs that are enriched at FAs (FA-mRNAs). FA-mRNAs share characteristics with stress granule (SG) mRNAs and are found in ribonucleoprotein (RNP) complexes with the SG RBP. Mechanistically, G3BP1 binds to FA proteins in an RNA-dependent manner, and its RNA-binding and dimerization domains, essential for G3BP1 to form RNPs in SG, are required for FA localization and cell migration. We find that G3BP1 RNPs promote cell speed by enhancing FA protein mobility and FA size. These findings suggest a previously unappreciated role for G3BP1 RNPs in regulating FA function under non-stress conditions.
Project description:The subcellular localization of mRNAs plays a pivotal role in biological processes, including cell migration. For instance, β-actin mRNA and its associated RNA binding protein (RBP), ZBP1/IGF2BP1, are recruited to focal adhesions (FAs), to support localized β-actin synthesis, crucial for cell migration. However, whether other mRNAs and RBPs also localize at FAs remains unclear. Here, we identify hundreds of mRNAs that are enriched at FAs (FA-mRNAs). FA-mRNAs share characteristics with stress granule (SG) mRNAs and are found in ribonucleoprotein (RNP) complexes with the SG RBP. Mechanistically, G3BP1 binds to FA proteins in an RNA-dependent manner, and its RNA-binding and dimerization domains, essential for G3BP1 to form RNPs in SG, are required for FA localization and cell migration. We find that G3BP1 RNPs promote cell speed by enhancing FA protein mobility and FA size. These findings suggest a previously unappreciated role for G3BP1 RNPs in regulating FA function under non-stress conditions.
Project description:The essential functions of intestinal stem cells (ISCs) are to self-renew and give rise to progenitors that subsequently differentiate to absorptive or secretory cells, thus maintaining homeostasis in the intestinal epithelium. In this study, we analyzed the transcriptomic and epigenetic changes of ISCs with Klf5 deletion to understand the role of KLF5 in ISC identity and functions.
Project description:Diabetes mellitus, obesity, and dyslipidemia increase risk for cardiovascular disease, and expose the heart to high plasma fatty acid (FA) levels. Recent studies suggest that distinct FA species are cardiotoxic (e.g., palmitate), while others are cardioprotective (e.g., oleate), although the molecular mechanisms mediating these observations are unclear. The purpose of the present study was to investigate the differential effects of distinct FA species (varying carbon length and degree of saturation) on adult rat cardiomyocyte (ARC) gene expression. ARCs were initialy challenged with 0.4 mM octanoate (8:0), palmitate (16:0), stearate (18:0), oleate (18:1), or linoleate (18:2) for 24 h. Microarray analysis revealed differential regulation of gene expression by the distinct FAs; the order regarding the number of genes whose expression was influenced by a specific FA was octanoate (1,188) . stearate (740) . palmitate (590) . oleate (83) . linoleate (65). In general, cardioprotective FAs (e.g., oleate) increased expression of genes promoting FA oxidation to a greater extent than cardiotoxic FAs (e.g., palmitate), whereas the latter induced markers of endoplasmic reticulum and oxidative stress. Subsequent RT-PCR analysis revealed distinct time- and concentration-dependent effects of these FA species, in a gene-specific manner. For example, stearate- and palmitate-mediated ucp3 induction tended to be transient (i.e., initial high induction, followed by subsequent repression), whereas oleate-mediated induction was sustained. These findings may provide insight into why diets high in unsaturated FAs (e.g., oleate) are cardioprotective, whereas diets rich in saturated FAs (e.g., palmitate) are not.
Project description:Adoptive cell therapy (ACT) based on ex vivo expanded autologous tumor-infiltrating lymphocytes (TILs) can mediate durable antitumor responses even in heavily pretreated patients. However, only a subset of patients responds to ACT; efforts to identify correlates of response have focused on profiling the tumor or the TIL but rarely in an interactive environment. Interactive profiling can provide unique insights into the clinical performance of TILs since the fate, function, and metabolism of TILs are influenced by autologous tumor-derived factors. Here, we performed a suite of cell-sparing assays dubbed holistic analysis of the bioactivity of interacting T cells and autologous tumor cells (HABITAT). HABITAT profiling of TILs used for human ACT and their autologous tumor cells included function-based single-cell profiling by timelapse imaging microscopy in nanowell grids (TIMING); multi-omics using RNA-sequencing and proteomics; metabolite inference using genome-scale metabolic modeling, and pulse-chase assays based on confocal microscopy to profile the uptake and fate of fatty acids (FA). Phenotypically, the ACT TILs from both responders (Rs) and nonresponders (NRs) were comprised of predominantly effector memory T cells (TEM cells) and did not express a high frequency of programmed death ligand-1 (PD-L1) and showed no differences in TCR diversity. Our results demonstrate that while tumor cells from both Rs and NRs are efficient at uptaking FAs, R TILs are significantly more efficient at utilizing FA through fatty acid oxidation (FAO) than NR TILs under nutrient starvation conditions. While it is likely that lipid and FA uptake is an inherent adaptation of TIL populations to lipid-rich environments, performing FAO sustains the survival of TILs and allows them to sustain antitumor cytolytic activity. We propose that metabolic plasticity enabling FAO is a desirable attribute of human TILs for ACT leading to clinical responses.
Project description:Movement of circulating fatty acids (FAs) to parenchymal cells requires their transfer across the endothelial cell (EC) barrier. The multi-ligand receptor cluster of differentiation 36 (CD36) facilitates tissue FA uptake and is expressed in ECs and parenchymal cells such as myocytes and adipocytes. Whether tissue uptake of FAs is dependent on EC or parenchymal cell CD36, or both, is unknown. Using a cell-specific deletion approach, we show that CD36-mediated FA transport across ECs rate-limits tissue FA uptake, and its loss leads to metabolic effects in parenchymal cells.