1
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Borén J, Taskinen MR, Packard CJ. Biosynthesis and Metabolism of ApoB-Containing Lipoproteins. Annu Rev Nutr 2024; 44:179-204. [PMID: 38635875 DOI: 10.1146/annurev-nutr-062222-020716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/20/2024]
Abstract
Recent advances in human genetics, together with a substantial body of epidemiological, preclinical and clinical trial evidence, strongly support a causal relationship between triglyceride-rich lipoproteins (TRLs) and atherosclerotic cardiovascular disease. Consequently, the secretion and metabolism of TRLs have a significant impact on cardiovascular health. This knowledge underscores the importance of understanding the molecular mechanisms and regulation of very-low-density lipoprotein (VLDL) and chylomicron biogenesis. Fortunately, there has been a resurgence of interest in the intracellular assembly, trafficking, degradation, and secretion of VLDL, leading to many ground-breaking molecular insights. Furthermore, the identification of molecular control mechanisms related to triglyceride metabolism has greatly advanced our understanding of the complex metabolism of TRLs. In this review, we explore recent advances in the assembly, secretion, and metabolism of TRLs. We also discuss available treatment strategies for hypertriglyceridemia.
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Affiliation(s)
- Jan Borén
- Wallenberg Laboratory, Sahlgrenska University Hospital, Gothenburg, Sweden
- Department of Molecular and Clinical Medicine, University of Gothenburg, Gothenburg, Sweden;
| | - Marja-Riitta Taskinen
- Research Programs Unit, Clinical and Molecular Metabolism, University of Helsinki, Helsinki, Finland
| | - Chris J Packard
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom
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2
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Bernier-Latmani J, González-Loyola A, Petrova TV. Mechanisms and functions of intestinal vascular specialization. J Exp Med 2024; 221:e20222008. [PMID: 38051275 PMCID: PMC10697212 DOI: 10.1084/jem.20222008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 11/10/2023] [Accepted: 11/15/2023] [Indexed: 12/07/2023] Open
Abstract
The intestinal vasculature has been studied for the last 100 years, and its essential role in absorbing and distributing ingested nutrients is well known. Recently, fascinating new insights into the organization, molecular mechanisms, and functions of intestinal vessels have emerged. These include maintenance of intestinal epithelial cell function, coping with microbiota-induced inflammatory pressure, recruiting gut-specific immune cells, and crosstalk with other organs. Intestinal function is also regulated at the systemic and cellular levels, such that the postprandial hyperemic response can direct up to 30% of systemic blood to gut vessels, while micron-sized endothelial cell fenestrations are necessary for nutrient uptake. In this review, we will highlight past discoveries made about intestinal vasculature in the context of new findings of molecular mechanisms underpinning gut function. Such comprehensive understanding of the system will pave the way to breakthroughs in nutrient uptake optimization, drug delivery efficiency, and treatment of human diseases.
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Affiliation(s)
- Jeremiah Bernier-Latmani
- Department of Oncology, University of Lausanne and Ludwig Institute for Cancer Research Lausanne, Lausanne, Switzerland
| | | | - Tatiana V. Petrova
- Department of Oncology, University of Lausanne and Ludwig Institute for Cancer Research Lausanne, Lausanne, Switzerland
- Swiss Institute for Experimental Cancer Research, School of Life Sciences, École polytechnique fédérale de Lausanne, Lausanne, Switzerland
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3
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Xia D, Hu C, Hou Y. Regorafenib loaded self-assembled lipid-based nanocarrier for colorectal cancer treatment via lymphatic absorption. Eur J Pharm Biopharm 2023; 185:165-176. [PMID: 36870399 DOI: 10.1016/j.ejpb.2023.02.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 02/11/2023] [Accepted: 02/27/2023] [Indexed: 03/06/2023]
Abstract
Oral chemotherapy can improve the life quality of patients; however, the therapeutic effects are limited by low bioavailability and rapid in vivo elimination of anticancer drugs. Here, we developed a regorafenib (REG)-loaded self-assembled lipid-based nanocarrier (SALN) to improve oral absorption and anti-colorectal cancer efficacy of REG through lymphatic absorption. SALN was prepared with lipid-based excipients to utilize lipid transport in the enterocytes and enhance lymphatic absorption of the drug in the gastrointestinal tract. The particle size of SALN was 106 ± 10 nm. SALNs were internalized by the intestinal epithelium via the clathrin-mediated endocytosis, and then transported across the epithelium via the chylomicron secretion pathway, resulting in a 3.76-fold increase in drug epithelial permeability (Papp) compared to the solid dispersion (SD). After oral administration to rats, SALNs were transported by the endoplasmic reticulum, Golgi apparatus, and secretory vesicles of enterocytes and were found in the lamina propria of intestinal villi, abdominal mesenteric lymph, and plasma. The oral bioavailability of SALN was 65.9-fold and 1.70-fold greater than that of the coarse powder suspension and SD, respectively, and was highly dependent on the lymphatic route of absorption. Notably, SALN prolonged the elimination half-life of the drug (9.34 ± 2.51 h) compared to the solid dispersion (3.51 ± 0.46 h), increased the biodistribution of REG in the tumor and gastrointestinal (GI) tract, decreased biodistribution in the liver, and showed better therapeutic efficacy than the solid dispersion in colorectal tumor-bearing mice. These results demonstrated that SALN is promising for the treatment of colorectal cancer via lymphatic transport and has potential for clinical translation.
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Affiliation(s)
- Dengning Xia
- School of Pharmaceutical Sciences (Shenzhen), Shenzhen Campus of Sun Yat-sen University, Shenzhen 518107, China.
| | - Cunde Hu
- Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; Nano Science and Technology Institute, University of Science and Technology of China, Suzhou 215123, China
| | - Yulin Hou
- School of Pharmaceutical Sciences (Shenzhen), Shenzhen Campus of Sun Yat-sen University, Shenzhen 518107, China
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4
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Effect of the First Feeding on Enterocytes of Newborn Rats. Int J Mol Sci 2022; 23:ijms232214179. [PMID: 36430658 PMCID: PMC9699143 DOI: 10.3390/ijms232214179] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Revised: 11/06/2022] [Accepted: 11/11/2022] [Indexed: 11/18/2022] Open
Abstract
The transcytosis of lipids through enterocytes occurs through the delivery of lipid micelles to the microvilli of enterocytes, consumption of lipid derivates by the apical plasma membrane (PM) and then their delivery to the membrane of the smooth ER attached to the basolateral PM. The SER forms immature chylomicrons (iChMs) in the ER lumen. iChMs are delivered at the Golgi complex (GC) where they are subjected to additional glycosylation resulting in maturation of iChMs. ChMs are secreted into the intercellular space and delivered into the lumen of lymphatic capillaries (LCs). The overloading of enterocytes with lipids induces the formation of lipid droplets inside the lipid bilayer of the ER membranes and transcytosis becomes slower. Here, we examined components of the enterocyte-to-lymphatic barriers in newly born rats before the first feeding and after it. In contrast to adult animals, enterocytes of newborns rats exhibited apical endocytosis and a well-developed subapical endosomal tubular network. These enterocytes uptake membranes from amniotic fluid. Then these membranes are transported across the polarized GC and secreted into the intercellular space. The enterocytes did not contain COPII-coated buds on the granular ER. The endothelium of blood capillaries situated near the enterocytes contained only a few fenestrae. The LCs were similar to those in adult animals. The first feeding induced specific alterations of enterocytes, which were similar to those observed after the lipid overloading of enterocytes in adult rats. Enlarged chylomicrons were stopped at the level of the LAMP2 and Neu1 positive post-Golgi structures, secreted, fused, delivered to the interstitial space, captured by the LCs and transported to the lymph node, inducing the movement of macrophages from lymphatic follicles into its sinuses. The macrophages captured the ChMs, preventing their delivery into the blood.
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5
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Sesorova IS, Sesorov VV, Soloviev PB, Lakunin KY, Dimov ID, Mironov AA. Role of Endothelial Regeneration and Overloading of Enterocytes with Lipids in Capturing of Lipoproteins by Basement Membrane of Rat Aortic Endothelium. Biomedicines 2022; 10:2858. [PMID: 36359378 PMCID: PMC9687266 DOI: 10.3390/biomedicines10112858] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Revised: 10/11/2022] [Accepted: 10/27/2022] [Indexed: 10/29/2023] Open
Abstract
Atherosclerosis is a complex non-monogenic disease related to endothelial damage in elastic-type arteries and incorrect feeding. Here, using cryodamage of endothelial cells (ECs) of rat abdominal aorta, we examined the role of the EC basement membrane (BM) for re-endothelization endothelial regeneration and its ability to capture low density lipoproteins (LDLs). Regeneration of endothelium induced thickening of the ECBM. Secretion of the BM components occurred in the G2-phase. Multiple regenerations, as well as arterial hypertension and aging, also led to the thickening of the BM. Under these conditions, the speed of re-endothelialization increased. The thick BM captured more LDLs. LDLs formed after overloading of rats with lipids acquired higher affinity to the BM, presumably due to the prolonged transport of chylomicrons through neuraminidase-positive endo-lysosomes. These data provide new molecular and cellular mechanisms of atherogenesis.
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Affiliation(s)
- Irina S. Sesorova
- Department of Anatomy, Ivanovo State Medical Academy, 153012 Ivanovo, Russia
| | - Vitaly V. Sesorov
- Department of Anatomy, Ivanovo State Medical Academy, 153012 Ivanovo, Russia
| | - Pavel B. Soloviev
- Department of Pathological Anatomy, Ivanovo State Medical Academy, 153012 Ivanovo, Russia
| | | | - Ivan D. Dimov
- Department of Anatomy, Saint Petersburg State Pediatric Medical University, 194100 Saint Petersburg, Russia
| | - Alexander A. Mironov
- Italian Foundation for Cancer Research Institute of Molecular Oncology, Via Adamello 16, 20139 Milan, Italy
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6
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Wilting J, Becker J. The lymphatic vascular system: much more than just a sewer. Cell Biosci 2022; 12:157. [PMID: 36109802 PMCID: PMC9476376 DOI: 10.1186/s13578-022-00898-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Accepted: 09/06/2022] [Indexed: 11/18/2022] Open
Abstract
Almost 400 years after the (re)discovery of the lymphatic vascular system (LVS) by Gaspare Aselli (Asellius G. De lactibus, sive lacteis venis, quarto vasorum mesaraicorum genere, novo invento Gasparis Asellii Cremo. Dissertatio. (MDCXXIIX), Milan; 1628.), structure, function, development and evolution of this so-called 'second' vascular system are still enigmatic. Interest in the LVS was low because it was (and is) hardly visible, and its diseases are not as life-threatening as those of the blood vascular system. It is not uncommon for patients with lymphedema to be told that yes, they can live with it. Usually, the functions of the LVS are discussed in terms of fluid homeostasis, uptake of chylomicrons from the gut, and immune cell circulation. However, the broad molecular equipment of lymphatic endothelial cells suggests that they possess many more functions, which are also reflected in the pathophysiology of the system. With some specific exceptions, lymphatics develop in all organs. Although basic structure and function are the same regardless their position in the body wall or the internal organs, there are important site-specific characteristics. We discuss common structure and function of lymphatics; and point to important functions for hyaluronan turn-over, salt balance, coagulation, extracellular matrix production, adipose tissue development and potential appetite regulation, and the influence of hypoxia on the regulation of these functions. Differences with respect to the embryonic origin and molecular equipment between somatic and splanchnic lymphatics are discussed with a side-view on the phylogeny of the LVS. The functions of the lymphatic vasculature are much broader than generally thought, and lymphatic research will have many interesting and surprising aspects to offer in the future.
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Affiliation(s)
- Jörg Wilting
- Department of Anatomy and Cell Biology, University Medical School Göttingen, Göttingen, Germany.
| | - Jürgen Becker
- Department of Anatomy and Cell Biology, University Medical School Göttingen, Göttingen, Germany
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7
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Comparison of the Cisterna Maturation-Progression Model with the Kiss-and-Run Model of Intra-Golgi Transport: Role of Cisternal Pores and Cargo Domains. Int J Mol Sci 2022; 23:ijms23073590. [PMID: 35408951 PMCID: PMC8999060 DOI: 10.3390/ijms23073590] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 03/11/2022] [Accepted: 03/16/2022] [Indexed: 12/22/2022] Open
Abstract
The Golgi complex is the central station of the secretory pathway. Knowledge about the mechanisms of intra-Golgi transport is inconsistent. Here, we compared the explanatory power of the cisterna maturation-progression model and the kiss-and-run model. During intra-Golgi transport, conventional cargoes undergo concentration and form cisternal distensions or distinct membrane domains that contain only one membrane cargo. These domains and distension are separated from the rest of the Golgi cisternae by rows of pores. After the arrival of any membrane cargo or a large cargo aggregate at the Golgi complex, the cis-Golgi SNAREs become enriched within the membrane of cargo-containing domains and then replaced by the trans-Golgi SNAREs. During the passage of these domains, the number of cisternal pores decreases. Restoration of the cisternal pores is COPI-dependent. Our observations are more in line with the kiss-and-run model.
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8
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Xu E, Chen C, Fu J, Zhu L, Shu J, Jin M, Wang Y, Zong X. Dietary fatty acids in gut health: Absorption, metabolism and function. ANIMAL NUTRITION (ZHONGGUO XU MU SHOU YI XUE HUI) 2021; 7:1337-1344. [PMID: 34786506 PMCID: PMC8570925 DOI: 10.1016/j.aninu.2021.09.010] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Revised: 09/17/2021] [Accepted: 09/26/2021] [Indexed: 12/23/2022]
Abstract
In biological responses, fatty acids (FA) are absorbed and metabolized in the form of substrates for energy production. The molecular structures (number of double bonds and chain length) and composition of dietary FA impact digestion, absorption and metabolism, and the biological roles of FA. Recently, increasing evidence indicates that FA are essentially utilized as an energy source and are signaling molecules that exert physiological activity of gut microbiota and immune responses. In addition, FA could serve as natural ligands for orphan G protein-coupled receptors (GPCR), also called free fatty acid receptors (FFAR), which intertwine metabolic and immune systems via multiple mechanisms. The present review explores the recent findings on FA absorption and its impact on gut health, particularly addressing the mechanism by which dietary FA potentially influences intestinal microbiota and epithelial functions. Also, this work attempts to uncover research ideas for devising future strategies for manipulating the composition of dietary FA to regulate gut health and support a normal immune system for metabolic and immune disorders.
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Affiliation(s)
- E. Xu
- Key Laboratory of Animal Genetics, Breeding and Reproduction in the Plateau Mountainous Region, Ministry of Education, College of Aniaml Science, Guizhou University, 550025 Guiyang, China
| | - Chao Chen
- Key Laboratory of Animal Genetics, Breeding and Reproduction in the Plateau Mountainous Region, Ministry of Education, College of Aniaml Science, Guizhou University, 550025 Guiyang, China
| | - Jie Fu
- Key Laboratory of Molecular Animal Nutrition, Ministry of Education, College of Animal Sciences, Zhejiang University, 310058 Hangzhou, China
| | - Luoyi Zhu
- Key Laboratory of Molecular Animal Nutrition, Ministry of Education, College of Animal Sciences, Zhejiang University, 310058 Hangzhou, China
| | - Junlan Shu
- Key Laboratory of Animal Genetics, Breeding and Reproduction in the Plateau Mountainous Region, Ministry of Education, College of Aniaml Science, Guizhou University, 550025 Guiyang, China
| | - Mingliang Jin
- Key Laboratory of Molecular Animal Nutrition, Ministry of Education, College of Animal Sciences, Zhejiang University, 310058 Hangzhou, China
- Key Laboratory of Animal Nutrition and Feed Science in Eastern China, Ministry of Agriculture, College of Animal Sciences, Zhejiang University, 310058 Hangzhou, China
| | - Yizhen Wang
- Key Laboratory of Molecular Animal Nutrition, Ministry of Education, College of Animal Sciences, Zhejiang University, 310058 Hangzhou, China
- Key Laboratory of Animal Nutrition and Feed Science in Eastern China, Ministry of Agriculture, College of Animal Sciences, Zhejiang University, 310058 Hangzhou, China
| | - Xin Zong
- Key Laboratory of Molecular Animal Nutrition, Ministry of Education, College of Animal Sciences, Zhejiang University, 310058 Hangzhou, China
- Key Laboratory of Animal Nutrition and Feed Science in Eastern China, Ministry of Agriculture, College of Animal Sciences, Zhejiang University, 310058 Hangzhou, China
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9
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Sesorova IS, Dimov ID, Kashin AD, Sesorov VV, Karelina NR, Zdorikova MA, Beznoussenko GV, Mirоnоv AA. Cellular and sub-cellular mechanisms of lipid transport from gut to lymph. Tissue Cell 2021; 72:101529. [PMID: 33915359 DOI: 10.1016/j.tice.2021.101529] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 02/26/2021] [Accepted: 03/11/2021] [Indexed: 12/14/2022]
Abstract
Although the general structure of the barrier between the gut and the blood is well known, many details are still missing. Here, we analyse the literature and our own data related to lipid transcytosis through adult mammalian enterocytes, and their absorption into lymph at the tissue level of the intestine. After starvation, the Golgi complex (GC) of enterocytes is in a resting state. The addition of lipids in the form of chyme leads to the initial appearance of pre-chylomicrons (ChMs) in the tubules of the smooth endoplasmic reticulum, which are attached at the basolateral plasma membrane, immediately below the 'belt' of the adhesive junctions. Then pre-ChMs move into the cisternae of the rough endoplasmic reticulum and then into the expansion of the perforated Golgi cisternae. Next, they pass through the GC, and are concentrated in the distensions of the perforated cisternae on the trans-side of the GC. The arrival of pre-ChMs at the GC leads to the transition of the GC to a state of active transport, with formation of intercisternal connections, attachment of cis-most and trans-most perforated cisternae to the medial Golgi cisternae, and disappearance of COPI vesicles. Post-Golgi carriers then deliver ChMs to the basolateral plasma membrane, fuse with it, and secret ChMs into the intercellular space between enterocytes at the level of their interdigitating contacts. Finally, ChMs are squeezed out into the interstitium through pores in the basal membrane, most likely due to the function of the actin-myosin 'cuff' around the interdigitating contacts. These pores appear to be formed by protrusions of the dendritic cells and the enterocytes per se. ChMs are absorbed from the interstitium into the lymphatic capillaries through the special oblique contacts between endothelial cells, which function as valves through the contraction-relaxation of bundles of smooth muscle cells in the interstitium. Lipid overloading of enterocytes results in accumulation of cytoplasmic lipid droplets, an increase in diameter of ChMs, inhibition of intra-Golgi transport, and fusion of ChMs in the interstitium. Here, we summarise and analyse recent findings, and discuss their functional implications.
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Affiliation(s)
- Irina S Sesorova
- Department of Anatomy, Saint Petersburg State Paediatric Medical University, S. Petersburg, Russia
| | - Ivan D Dimov
- Department of Anatomy, Ivanovo State Medical Academy, Ivanovo, Russia
| | - Alexandre D Kashin
- Department of Anatomy, Saint Petersburg State Paediatric Medical University, S. Petersburg, Russia
| | - Vitaly V Sesorov
- Department of Anatomy, Saint Petersburg State Paediatric Medical University, S. Petersburg, Russia
| | | | - Maria A Zdorikova
- Department of Anatomy, Saint Petersburg State Paediatric Medical University, S. Petersburg, Russia
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10
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Assembly and Cellular Exit of Coronaviruses: Hijacking an Unconventional Secretory Pathway from the Pre-Golgi Intermediate Compartment via the Golgi Ribbon to the Extracellular Space. Cells 2021; 10:cells10030503. [PMID: 33652973 PMCID: PMC7996754 DOI: 10.3390/cells10030503] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Revised: 02/18/2021] [Accepted: 02/18/2021] [Indexed: 12/20/2022] Open
Abstract
Coronaviruses (CoVs) assemble by budding into the lumen of the intermediate compartment (IC) at the endoplasmic reticulum (ER)-Golgi interface. However, why CoVs have chosen the IC as their intracellular site of assembly and how progeny viruses are delivered from this compartment to the extracellular space has remained unclear. Here we address these enigmatic late events of the CoV life cycle in light of recently described properties of the IC. Of particular interest are the emerging spatial and functional connections between IC elements and recycling endosomes (REs), defined by the GTPases Rab1 and Rab11, respectively. The establishment of IC-RE links at the cell periphery, around the centrosome and evidently also at the noncompact zones of the Golgi ribbon indicates that—besides traditional ER-Golgi communication—the IC also promotes a secretory process that bypasses the Golgi stacks, but involves its direct connection with the endocytic recycling system. The initial confinement of CoVs to the lumen of IC-derived large transport carriers and their preferential absence from Golgi stacks is consistent with the idea that they exit cells following such an unconventional route. In fact, CoVs may share this pathway with other intracellularly budding viruses, lipoproteins, procollagen, and/or protein aggregates experimentally introduced into the IC lumen.
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11
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Norden PR, Kume T. Molecular Mechanisms Controlling Lymphatic Endothelial Junction Integrity. Front Cell Dev Biol 2021; 8:627647. [PMID: 33521001 PMCID: PMC7841202 DOI: 10.3389/fcell.2020.627647] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Accepted: 12/18/2020] [Indexed: 12/11/2022] Open
Abstract
The lymphatic system is essential for lipid absorption/transport from the digestive system, maintenance of tissue fluid and protein homeostasis, and immune surveillance. Despite recent progress toward understanding the cellular and molecular mechanisms underlying the formation of the lymphatic vascular system, the nature of lymphatic vessel abnormalities and disease in humans is complex and poorly understood. The mature lymphatic vasculature forms a hierarchical network in which lymphatic endothelial cells (LECs) are joined by functionally specialized cell-cell junctions to maintain the integrity of lymphatic vessels. Blind-ended and highly permeable lymphatic capillaries drain interstitial fluid via discontinuous, button-like LEC junctions, whereas collecting lymphatic vessels, surrounded by intact basement membranes and lymphatic smooth muscle cells, have continuous, zipper-like LEC junctions to transport lymph to the blood circulatory system without leakage. In this review, we discuss the recent advances in our understanding of the mechanisms by which lymphatic button- and zipper-like junctions play critical roles in lymphatic permeability and function in a tissue- and organ-specific manner, including lacteals of the small intestine. We also provide current knowledge related to key pathways and factors such as VEGF and RhoA/ROCK signaling that control lymphatic endothelial cell junctional integrity.
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Affiliation(s)
- Pieter R Norden
- Department of Medicine, Feinberg School of Medicine, Feinberg Cardiovascular and Renal Research Institute, Northwestern University, Chicago, IL, United States
| | - Tsutomu Kume
- Department of Medicine, Feinberg School of Medicine, Feinberg Cardiovascular and Renal Research Institute, Northwestern University, Chicago, IL, United States
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Nakano T, Inoue I, Takenaka Y, Ito R, Kotani N, Sato S, Nakano Y, Hirasaki M, Shimada A, Murakoshi T. Ezetimibe impairs transcellular lipid trafficking and induces large lipid droplet formation in intestinal absorptive epithelial cells. Biochim Biophys Acta Mol Cell Biol Lipids 2020; 1865:158808. [PMID: 32860884 DOI: 10.1016/j.bbalip.2020.158808] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 07/30/2020] [Accepted: 08/18/2020] [Indexed: 01/26/2023]
Abstract
Ezetimibe inhibits Niemann-Pick C1-like 1 (NPC1L1) protein, which mediates intracellular cholesterol trafficking from the brush border membrane to the endoplasmic reticulum, where chylomicron assembly takes place in enterocytes or in the intestinal absorptive epithelial cells. Cholesterol is a minor lipid constituent of chylomicrons; however, whether or not a shortage of cholesterol attenuates chylomicron assembly is unknown. The aim of this study was to examine the effect of ezetimibe, a potent NPC1L1 inhibitor, on trans-epithelial lipid transport, and chylomicron assembly and secretion in enterocytes. Caco-2 cells, an absorptive epithelial model, grown onto culture inserts were given lipid micelles from the apical side, and chylomicron-like triacylglycerol-rich lipoprotein secreted basolaterally were analyzed after a 24-h incubation period in the presence of ezetimibe up to 50 μM. The secretion of lipoprotein and apolipoprotein B48 were reduced by adding ezetimibe (30% and 34%, respectively). Although ezetimibe allowed the cells to take up cholesterol normally, the esterification was abolished. Meanwhile, oleic acid esterification was unaffected. Moreover, ezetimibe activated sterol regulatory element-binding protein 2 by approximately 1.5-fold. These results suggest that ezetimibe limited cellular cholesterol mobilization required for lipoprotein assembly. In such conditions, large lipid droplet formation in Caco-2 cells and the enterocytes of mice were induced, implying that unprocessed triacylglycerol was sheltered in these compartments. Although ezetimibe did not reduce the post-prandial lipid surge appreciably in triolein-infused mice, the results of the present study indicated that pharmacological actions of ezetimibe may participate in a novel regulatory mechanism for the efficient chylomicron assembly and secretion.
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Affiliation(s)
- Takanari Nakano
- Department of Biochemistry, Faculty of Medicine, Saitama Medical University, Saitama, Japan.
| | - Ikuo Inoue
- Department of Diabetes and Endocrinology, Faculty of Medicine, Saitama Medical University, Saitama, Japan
| | - Yasuhiro Takenaka
- Department of Diabetes and Endocrinology, Faculty of Medicine, Saitama Medical University, Saitama, Japan; Department of Physiology, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan
| | - Rina Ito
- Department of Biochemistry, Faculty of Medicine, Saitama Medical University, Saitama, Japan
| | - Norihiro Kotani
- Department of Biochemistry, Faculty of Medicine, Saitama Medical University, Saitama, Japan
| | - Sawako Sato
- Department of Diabetes and Endocrinology, Faculty of Medicine, Saitama Medical University, Saitama, Japan
| | - Yuka Nakano
- Department of Diabetes and Endocrinology, Faculty of Medicine, Saitama Medical University, Saitama, Japan
| | - Masataka Hirasaki
- Division of Developmental Biology, Research Center for Genomic Medicine, Faculty of Medicine, Saitama Medical University, Saitama, Japan
| | - Akira Shimada
- Department of Diabetes and Endocrinology, Faculty of Medicine, Saitama Medical University, Saitama, Japan
| | - Takayuki Murakoshi
- Department of Biochemistry, Faculty of Medicine, Saitama Medical University, Saitama, Japan
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13
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Structure of the enterocyte transcytosis compartments during lipid absorption. Histochem Cell Biol 2020; 153:413-429. [DOI: 10.1007/s00418-020-01851-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/04/2020] [Indexed: 12/14/2022]
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14
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Regulation of intestinal lipid metabolism: current concepts and relevance to disease. Nat Rev Gastroenterol Hepatol 2020; 17:169-183. [PMID: 32015520 DOI: 10.1038/s41575-019-0250-7] [Citation(s) in RCA: 232] [Impact Index Per Article: 58.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 12/02/2019] [Indexed: 12/21/2022]
Abstract
Lipids entering the gastrointestinal tract include dietary lipids (triacylglycerols, cholesteryl esters and phospholipids) and endogenous lipids from bile (phospholipids and cholesterol) and from shed intestinal epithelial cells (enterocytes). Here, we comprehensively review the digestion, uptake and intracellular re-synthesis of intestinal lipids as well as their packaging into pre-chylomicrons in the endoplasmic reticulum, their modification in the Golgi apparatus and the exocytosis of the chylomicrons into the lamina propria and subsequently to lymph. We also discuss other fates of intestinal lipids, including intestinal HDL and VLDL secretion, cytosolic lipid droplets and fatty acid oxidation. In addition, we highlight the applicability of these findings to human disease and the development of therapeutics targeting lipid metabolism. Finally, we explore the emerging role of the gut microbiota in modulating intestinal lipid metabolism and outline key questions for future research.
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15
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Zhou A, Qu J, Liu M, Tso P. The Role of Interstitial Matrix and the Lymphatic System in Gastrointestinal Lipid and Lipoprotein Metabolism. Front Physiol 2020; 11:4. [PMID: 32038309 PMCID: PMC6987427 DOI: 10.3389/fphys.2020.00004] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Accepted: 01/06/2020] [Indexed: 12/16/2022] Open
Abstract
This review emphasizes the events that take place after the chylomicrons are secreted by the enterocytes through exocytosis. First, we will discuss the journey of how chylomicrons cross the basement membrane to enter the lamina propria. Then the chylomicrons have to travel across the lamina propria before they can enter the lacteals. To understand the factors affecting the trafficking of chylomicron particles across the lamina propria, it is important to understand the composition and properties of the lamina propria. With different degree of hydration, the pores of the lamina propria (sponge) changes. The greater the hydration, the greater the pore size and thus the easier the diffusion of the chylomicron particles across the lamina propria to enter the lacteals. The mechanism of the entry of lacteals is discussed in considerable details. We and others have demonstrated that intestinal fat absorption, but not the absorption of protein or carbohydrates, activates the intestinal mucosal mast cells to release many products including mucosal mast cell protease II in the rat. The activation of intestinal mucosal mast cells by fat absorption involves the process of chylomicron formation since the absorption of both medium and short-chain fatty acids do not activate the mast cells. Fat absorption has been associated with increased intestinal permeability. We hypothesize that there is a link between fat absorption, activation of mucosal mast cells, and the leaky gut phenomenon (increased intestinal permeability). Microbiome may also be involved in this chain of events associated with fat absorption. This review is presented in sequence under the following headings: (1) Introduction; (2) Structure and properties of the gut epithelial basement membrane; (3) Composition and physical properties of the interstitial matrix of the lamina propria; (4) The movement of chylomicrons across the interstitial matrix of the lamina propria and importance of the hydration of the interstitial matrix of the lamina propria and the movement of chylomicrons; (5) Entry of the chylomicrons into the intestinal lacteals; (6) Activation of mucosal mast cells by fat absorption and the metabolic consequences; and (7) Link between chylomicron transport, mucosal mast cell activation, leaky gut, and the microbiome.
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Affiliation(s)
- Anna Zhou
- Department of Pathology and Laboratory Medicine, University of Cincinnati Reading Campus, Cincinnati, OH, United States
| | - Jie Qu
- Department of Pathology and Laboratory Medicine, University of Cincinnati Reading Campus, Cincinnati, OH, United States
| | - Min Liu
- Department of Pathology and Laboratory Medicine, University of Cincinnati Reading Campus, Cincinnati, OH, United States
| | - Patrick Tso
- Department of Pathology and Laboratory Medicine, University of Cincinnati Reading Campus, Cincinnati, OH, United States
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16
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Hokkanen K, Tirronen A, Ylä-Herttuala S. Intestinal lymphatic vessels and their role in chylomicron absorption and lipid homeostasis. Curr Opin Lipidol 2019; 30:370-376. [PMID: 31361624 DOI: 10.1097/mol.0000000000000626] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
PURPOSE OF REVIEW In this review, we describe novel findings related to intestinal lipid transport in lymphatic vessels. RECENT FINDINGS Studies have shown that chylomicron entry to lacteals and lymph movement in intestinal lymphatic capillaries is an active process. Regulators of this intestinal chylomicron transport include among others the autonomous nervous system, transcription factors like PLAGL2, and molecular regulators, such as VEGF-A/Nrp1/VEGFR1, VEGF-C/VEGFR3, DLL4, CALCRL and GLP-2. Chylomicron transport in intestinal lymphatics is now emerging not only as an option for drug delivery but also as a new candidate for drug targeting in lipid-related disorders. SUMMARY Dysfunctions of lymphatic lipid transport can result in conditions such as dyslipidaemia. Intestinal lymphatics also provide several potential therapeutic possibilities: molecular regulation of lacteal cell-to-cell junctioning and lymph flow could provide new ways of treating conditions like hyperlipidaemia and associated diseases, such as atherosclerosis and other cardiovascular diseases, obesity, diabetes and fatty-liver disease. The intestinal lymphatic system can also be employed to deliver lipid nanoparticles as drug carriers to the venous circulation for improved treatment outcome. These findings highlight the importance and need for research on the different players of intestinal lymphatics in dietary lipid handling and therapeutic applications.
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Affiliation(s)
- Krista Hokkanen
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland
| | - Annakaisa Tirronen
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland
| | - Seppo Ylä-Herttuala
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland
- Heart Center and Gene Therapy Unit, Kuopio University Hospital, Kuopio, Finland
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17
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Ko CW, Qu J, Liu M, Black DD, Tso P. Use of Isotope Tracers to Assess Lipid Absorption in Conscious Lymph Fistula Mice. CURRENT PROTOCOLS IN MOUSE BIOLOGY 2019; 9:e60. [PMID: 30801996 PMCID: PMC6401309 DOI: 10.1002/cpmo.60] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
This protocol provides a comprehensive reference for the evolution of the lymph fistula model, the mechanism of lipid absorption, the detailed procedure for studying lipid absorption using the lymph fistula model, the interpretation of the results, and consideration of the experimental design. The lymph fistula model is an approach to assess the concentration and rate of a range of molecules transported by the lymph by cannulating lymph duct in animals. In this protocol, mice first undergo surgery with the implantation of cannulae in the duodenum and mesenteric lymph duct and are allowed to recover overnight in Bollman restraining cages housed in a temperature-regulated environment. To study in vivo lipid absorption, a lipid emulsion is prepared with labeled tracers, including [3 H]-triolein and [14 C]-cholesterol. On the day of the experiment, mice are continuously infused with lipid emulsion via the duodenum for 6 hr, and lymph is usually collected hourly. At the end of the study, gastrointestinal segments and their luminal contents are collected separately for determination of the digestion, uptake, and transport of exogenous lipids. © 2019 by John Wiley & Sons, Inc.
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Affiliation(s)
- Chih-Wei Ko
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, Ohio 45237
| | - Jie Qu
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, Ohio 45237
| | - Min Liu
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, Ohio 45237
| | - Dennis D Black
- Children’s Foundation Research Institute at Le Bonheur Children’s Hospital, University of Tennessee Health Science Center, Memphis, Tennessee 38103
| | - Patrick Tso
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, Ohio 45237
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18
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Mironov AA, Dimov ID, Beznoussenko GV. Role of Intracellular Transport in the Centriole-Dependent Formation of Golgi Ribbon. Results Probl Cell Differ 2019; 67:49-79. [PMID: 31435792 DOI: 10.1007/978-3-030-23173-6_4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The intracellular transport is the most confusing issue in the field of cell biology. The Golgi complex (GC) is the central station along the secretory pathway. It contains Golgi glycosylation enzymes, which are responsible for protein and lipid glycosylation, and in many cells, it is organized into a ribbon. Position and structure of the GC depend on the position and function of the centriole. Here, we analyze published data related to the role of centriole and intracellular transport (ICT) for the formation of Golgi ribbon and specifically stress the importance of the delivery of membranes containing cargo and membrane proteins to the cell centre where centriole/centrosome is localized. Additionally, we re-examined the formation of Golgi ribbon from the point of view of different models of ICT.
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Affiliation(s)
| | - Ivan D Dimov
- Department of Anatomy, Saint Petersburg State Paediatric Medical University, Saint Petersburg, Russia
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Breslin JW, Yang Y, Scallan JP, Sweat RS, Adderley SP, Murfee WL. Lymphatic Vessel Network Structure and Physiology. Compr Physiol 2018; 9:207-299. [PMID: 30549020 PMCID: PMC6459625 DOI: 10.1002/cphy.c180015] [Citation(s) in RCA: 174] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The lymphatic system is comprised of a network of vessels interrelated with lymphoid tissue, which has the holistic function to maintain the local physiologic environment for every cell in all tissues of the body. The lymphatic system maintains extracellular fluid homeostasis favorable for optimal tissue function, removing substances that arise due to metabolism or cell death, and optimizing immunity against bacteria, viruses, parasites, and other antigens. This article provides a comprehensive review of important findings over the past century along with recent advances in the understanding of the anatomy and physiology of lymphatic vessels, including tissue/organ specificity, development, mechanisms of lymph formation and transport, lymphangiogenesis, and the roles of lymphatics in disease. © 2019 American Physiological Society. Compr Physiol 9:207-299, 2019.
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Affiliation(s)
- Jerome W. Breslin
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, FL
| | - Ying Yang
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, FL
| | - Joshua P. Scallan
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, FL
| | - Richard S. Sweat
- Department of Biomedical Engineering, Tulane University, New Orleans, LA
| | - Shaquria P. Adderley
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, FL
| | - W. Lee Murfee
- Department of Biomedical Engineering, University of Florida, Gainesville, FL
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20
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Xiao C, Stahel P, Carreiro AL, Hung YH, Dash S, Bookman I, Buhman KK, Lewis GF. Oral Glucose Mobilizes Triglyceride Stores From the Human Intestine. Cell Mol Gastroenterol Hepatol 2018; 7:313-337. [PMID: 30704982 PMCID: PMC6357697 DOI: 10.1016/j.jcmgh.2018.10.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Revised: 10/05/2018] [Accepted: 10/05/2018] [Indexed: 12/22/2022]
Abstract
BACKGROUND & AIMS The small intestine regulates plasma triglyceride (TG) concentration. Within enterocytes, dietary TGs are packaged into chylomicrons (CMs) for secretion or stored temporarily in cytoplasmic lipid droplets (CLDs) until further mobilization. We and others have shown that oral and intravenous glucose enhances CM particle secretion in human beings, however, the mechanisms through which this occurs are incompletely understood. METHODS Two separate cohorts of participants ingested a high-fat liquid meal and, 5 hours later, were assigned randomly to ingest either a glucose solution or an equivalent volume of water. In 1 group (N = 6), plasma and lipoprotein TG responses were assessed in a randomized cross-over study. In a separate group (N = 24), duodenal biopsy specimens were obtained 1 hour after ingestion of glucose or water. Ultrastructural and proteomic analyses were performed on duodenal biopsy specimens. RESULTS Compared with water, glucose ingestion increased circulating TGs within 30 minutes, mainly in the CM fraction. It decreased the total number of CLDs and the proportion of large-sized CLDs within enterocytes. We identified 2919 proteins in human duodenal tissue, 270 of which are related to lipid metabolism and 134 of which were differentially present in response to glucose compared with water ingestion. CONCLUSIONS Oral glucose mobilizes TGs stored within enterocyte CLDs to provide substrate for CM synthesis and secretion. Future studies elucidating the underlying signaling pathways may provide mechanistic insights that lead to the development of novel therapeutics for the treatment of hypertriglyceridemia.
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Affiliation(s)
- Changting Xiao
- Division of Endocrinology and Metabolism, Departments of Medicine and Physiology, Banting and Best Diabetes Centre, University of Toronto, Toronto, Ontario, Canada
| | - Priska Stahel
- Division of Endocrinology and Metabolism, Departments of Medicine and Physiology, Banting and Best Diabetes Centre, University of Toronto, Toronto, Ontario, Canada
| | - Alicia L. Carreiro
- Department of Nutrition Science, Purdue University, West Lafayette, Indiana
| | - Yu-Han Hung
- Department of Nutrition Science, Purdue University, West Lafayette, Indiana
| | - Satya Dash
- Division of Endocrinology and Metabolism, Departments of Medicine and Physiology, Banting and Best Diabetes Centre, University of Toronto, Toronto, Ontario, Canada
| | - Ian Bookman
- Kensington Screening Clinic, Toronto, Ontario, Canada
| | - Kimberly K. Buhman
- Department of Nutrition Science, Purdue University, West Lafayette, Indiana
| | - Gary F. Lewis
- Division of Endocrinology and Metabolism, Departments of Medicine and Physiology, Banting and Best Diabetes Centre, University of Toronto, Toronto, Ontario, Canada,Correspondence Address correspondence to: Gary F. Lewis, MD, FRCPC, Toronto General Hospital, 200 Elizabeth Street, EN12-218, Toronto, Ontario, M5G 2C4 Canada. fax: (416) 340-3314.
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21
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Zhang F, Zarkada G, Han J, Li J, Dubrac A, Ola R, Genet G, Boyé K, Michon P, Künzel SE, Camporez JP, Singh AK, Fong GH, Simons M, Tso P, Fernández-Hernando C, Shulman GI, Sessa WC, Eichmann A. Lacteal junction zippering protects against diet-induced obesity. Science 2018; 361:599-603. [PMID: 30093598 PMCID: PMC6317738 DOI: 10.1126/science.aap9331] [Citation(s) in RCA: 181] [Impact Index Per Article: 30.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Revised: 04/04/2018] [Accepted: 06/27/2018] [Indexed: 12/18/2022]
Abstract
Excess dietary lipid uptake causes obesity, a major global health problem. Enterocyte-absorbed lipids are packaged into chylomicrons, which enter the bloodstream through intestinal lymphatic vessels called lacteals. Here, we show that preventing lacteal chylomicron uptake by inducible endothelial genetic deletion of Neuropilin1 (Nrp1) and Vascular endothelial growth factor receptor 1 (Vegfr1; also known as Flt1) renders mice resistant to diet-induced obesity. Absence of NRP1 and FLT1 receptors increased VEGF-A bioavailability and signaling through VEGFR2, inducing lacteal junction zippering and chylomicron malabsorption. Restoring permeable lacteal junctions by VEGFR2 and vascular endothelial (VE)-cadherin signaling inhibition rescued chylomicron transport in the mutant mice. Zippering of lacteal junctions by disassembly of cytoskeletal VE-cadherin anchors prevented chylomicron uptake in wild-type mice. These data suggest that lacteal junctions may be targets for preventing dietary fat uptake.
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Affiliation(s)
- Feng Zhang
- Cardiovascular Research Center, Yale University School of Medicine, New Haven, CT 06510-3221, USA
| | - Georgia Zarkada
- Cardiovascular Research Center, Yale University School of Medicine, New Haven, CT 06510-3221, USA
| | - Jinah Han
- Cardiovascular Research Center, Yale University School of Medicine, New Haven, CT 06510-3221, USA
| | - Jinyu Li
- Cardiovascular Research Center, Yale University School of Medicine, New Haven, CT 06510-3221, USA
| | - Alexandre Dubrac
- Cardiovascular Research Center, Yale University School of Medicine, New Haven, CT 06510-3221, USA
| | - Roxana Ola
- Cardiovascular Research Center, Yale University School of Medicine, New Haven, CT 06510-3221, USA
- Department of Basic, Preventive and Clinical Science, University of Transylvania, 500019 Brasov, Romania
| | - Gael Genet
- Cardiovascular Research Center, Yale University School of Medicine, New Haven, CT 06510-3221, USA
| | - Kevin Boyé
- Cardiovascular Research Center, Yale University School of Medicine, New Haven, CT 06510-3221, USA
| | - Pauline Michon
- Cardiovascular Research Center, Yale University School of Medicine, New Haven, CT 06510-3221, USA
- INSERM U970, Paris Cardiovascular Research Center, 75015 Paris, France
| | - Steffen E Künzel
- Cardiovascular Research Center, Yale University School of Medicine, New Haven, CT 06510-3221, USA
| | - Joao Paulo Camporez
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, USA
| | - Abhishek K Singh
- Departments of Comparative Medicine and Pathology, Vascular Biology and Therapeutics Program and Integrative Cell Signaling and Neurobiology of Metabolism Program, Yale University School of Medicine, New Haven, CT, USA
| | - Guo-Hua Fong
- Department of Cell Biology, University of Connecticut Health Center, Farmington, CT, 06030-3501, USA
| | - Michael Simons
- Cardiovascular Research Center, Yale University School of Medicine, New Haven, CT 06510-3221, USA
| | - Patrick Tso
- Department of Pathology and Laboratory Medicine, Metabolic Diseases Institute, University of Cincinnati, Cincinnati, OH 45237-0507, USA
| | - Carlos Fernández-Hernando
- Departments of Comparative Medicine and Pathology, Vascular Biology and Therapeutics Program and Integrative Cell Signaling and Neurobiology of Metabolism Program, Yale University School of Medicine, New Haven, CT, USA
| | - Gerald I Shulman
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, USA
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT, USA
| | - William C Sessa
- Department of Pharmacology, Vascular Biology and Therapeutics Program, Yale University School of Medicine, New Haven, CT, USA
| | - Anne Eichmann
- Cardiovascular Research Center, Yale University School of Medicine, New Haven, CT 06510-3221, USA.
- INSERM U970, Paris Cardiovascular Research Center, 75015 Paris, France
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT, USA
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22
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Transport mechanism of lipid covered saquinavir pure drug nanoparticles in intestinal epithelium. J Control Release 2018; 269:159-170. [DOI: 10.1016/j.jconrel.2017.11.012] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2017] [Revised: 11/04/2017] [Accepted: 11/09/2017] [Indexed: 12/13/2022]
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23
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Hung YH, Carreiro AL, Buhman KK. Dgat1 and Dgat2 regulate enterocyte triacylglycerol distribution and alter proteins associated with cytoplasmic lipid droplets in response to dietary fat. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1862:600-614. [PMID: 28249764 PMCID: PMC5503214 DOI: 10.1016/j.bbalip.2017.02.014] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Revised: 01/31/2017] [Accepted: 02/24/2017] [Indexed: 12/16/2022]
Abstract
Enterocytes, the absorptive cells of the small intestine, mediate efficient absorption of dietary fat (triacylglycerol, TAG). The digestive products of dietary fat are taken up by enterocytes, re-esterified into TAG, and packaged on chylomicrons (CMs) for secretion into blood or temporarily stored within cytoplasmic lipid droplets (CLDs). Altered enterocyte TAG distribution impacts susceptibility to high fat diet associated diseases, but molecular mechanisms directing TAG toward these fates are unclear. Two enzymes, acyl CoA: diacylglycerol acyltransferase 1 (Dgat1) and Dgat2, catalyze the final, committed step of TAG synthesis within enterocytes. Mice with intestine-specific overexpression of Dgat1 (Dgat1Int) or Dgat2 (Dgat2Int), or lack of Dgat1 (Dgat1-/-), were previously found to have altered intestinal TAG secretion and storage. We hypothesized that varying intestinal Dgat1 and Dgat2 levels alters TAG distribution in subcellular pools for CM synthesis as well as the morphology and proteome of CLDs. To test this we used ultrastructural and proteomic methods to investigate intracellular TAG distribution and CLD-associated proteins in enterocytes from Dgat1Int, Dgat2Int, and Dgat1-/- mice 2h after a 200μl oral olive oil gavage. We found that varying levels of intestinal Dgat1 and Dgat2 altered TAG pools involved in CM assembly and secretion, the number or size of CLDs present in enterocytes, and the enterocyte CLD proteome. Overall, these results support a model where Dgat1 and Dgat2 function coordinately to regulate the process of dietary fat absorption by preferentially synthesizing TAG for incorporation into distinct subcellular TAG pools in enterocytes.
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Affiliation(s)
- Yu-Han Hung
- Department of Nutrition Science, Purdue University, West Lafayette, IN 47907, USA
| | - Alicia L Carreiro
- Department of Nutrition Science, Purdue University, West Lafayette, IN 47907, USA
| | - Kimberly K Buhman
- Department of Nutrition Science, Purdue University, West Lafayette, IN 47907, USA.
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24
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Different Golgi ultrastructure across species and tissues: Implications under functional and pathological conditions, and an attempt at classification. Tissue Cell 2017; 49:186-201. [DOI: 10.1016/j.tice.2016.12.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2016] [Revised: 12/05/2016] [Accepted: 12/05/2016] [Indexed: 02/08/2023]
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25
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Jattan J, Rodia C, Li D, Diakhate A, Dong H, Bataille A, Shroyer NF, Kohan AB. Using primary murine intestinal enteroids to study dietary TAG absorption, lipoprotein synthesis, and the role of apoC-III in the intestine. J Lipid Res 2017; 58:853-865. [PMID: 28159868 DOI: 10.1194/jlr.m071340] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Revised: 01/18/2017] [Indexed: 02/01/2023] Open
Abstract
Since its initial report in 2009, the intestinal enteroid culture system has been a powerful tool used to study stem cell biology and development in the gastrointestinal tract. However, a major question is whether enteroids retain intestinal function and physiology. There have been significant contributions describing ion transport physiology of human intestinal organoid cultures, as well as physiology of gastric organoids, but critical studies on dietary fat absorption and chylomicron synthesis in primary intestinal enteroids have not been undertaken. Here we report that primary murine enteroid cultures recapitulate in vivo intestinal lipoprotein synthesis and secretion, and reflect key aspects of the physiology of intact intestine in regard to dietary fat absorption. We also show that enteroids can be used to elucidate intestinal mechanisms behind CVD risk factors, including tissue-specific apolipoprotein functions. Using enteroids, we show that intestinal apoC-III overexpression results in the secretion of smaller, less dense chylomicron particles along with reduced triacylglycerol secretion from the intestine. This model significantly expands our ability to test how specific genes or genetic polymorphisms function in dietary fat absorption and the precise intestinal mechanisms that are critical in the etiology of metabolic disease.
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Affiliation(s)
- Javeed Jattan
- Department of Nutritional Sciences, University of Connecticut, Storrs, CT
| | - Cayla Rodia
- Department of Nutritional Sciences, University of Connecticut, Storrs, CT
| | - Diana Li
- Department of Nutritional Sciences, University of Connecticut, Storrs, CT
| | - Adama Diakhate
- Department of Nutritional Sciences, University of Connecticut, Storrs, CT
| | - Hongli Dong
- Department of Nutritional Sciences, University of Connecticut, Storrs, CT
| | - Amy Bataille
- Department of Nutritional Sciences, University of Connecticut, Storrs, CT
| | - Noah F Shroyer
- Department of Medicine Section of Gastroenterology and Hepatology, Baylor College of Medicine, Houston, TX
| | - Alison B Kohan
- Department of Nutritional Sciences, University of Connecticut, Storrs, CT
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26
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Mansbach CM, Siddiqi S. Control of chylomicron export from the intestine. Am J Physiol Gastrointest Liver Physiol 2016; 310:G659-68. [PMID: 26950854 DOI: 10.1152/ajpgi.00228.2015] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Accepted: 02/22/2016] [Indexed: 01/31/2023]
Abstract
The control of chylomicron output by the intestine is a complex process whose outlines have only recently come into focus. In this review we will cover aspects of chylomicron formation and prechylomicron vesicle generation that elucidate potential control points. Substrate (dietary fatty acids and monoacylglycerols) availability is directly related to the output rate of chylomicrons. These substrates must be converted to triacylglycerol before packaging in prechylomicrons by a series of endoplasmic reticulum (ER)-localized acylating enzymes that rapidly convert fatty acids and monoacylglycerols to triacylglycerol. The packaging of the prechylomicron with triacylglycerol is controlled by the microsomal triglyceride transport protein, another potential limiting step. The prechylomicrons, once loaded with triacylglycerol, are ready to be incorporated into the prechylomicron transport vesicle that transports the prechylomicron from the ER to the Golgi. Control of this exit step from the ER, the rate-limiting step in the transcellular movement of the triacylglycerol, is a multistep process involving the activation of PKCζ, the phosphorylation of Sar1b, releasing the liver fatty acid binding protein from a heteroquatromeric complex, which enables it to bind to the ER and organize the prechylomicron transport vesicle budding complex. We propose that control of PKCζ activation is the major physiological regulator of chylomicron output.
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Affiliation(s)
- Charles M Mansbach
- Department of Medicine, Division of Gastroenterology, University of Tennessee Health Science Center, Memphis, Tennessee; and Department of Medicine, Veterans Affairs Medical Center, Memphis, Tennessee
| | - Shahzad Siddiqi
- Department of Medicine, Division of Gastroenterology, University of Tennessee Health Science Center, Memphis, Tennessee; and Department of Medicine, Veterans Affairs Medical Center, Memphis, Tennessee
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27
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D'Aquila T, Hung YH, Carreiro A, Buhman KK. Recent discoveries on absorption of dietary fat: Presence, synthesis, and metabolism of cytoplasmic lipid droplets within enterocytes. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:730-47. [PMID: 27108063 DOI: 10.1016/j.bbalip.2016.04.012] [Citation(s) in RCA: 88] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 03/16/2016] [Accepted: 04/16/2016] [Indexed: 02/07/2023]
Abstract
Dietary fat provides essential nutrients, contributes to energy balance, and regulates blood lipid concentrations. These functions are important to health, but can also become dysregulated and contribute to diseases such as obesity, diabetes, cardiovascular disease, and cancer. Within enterocytes, the digestive products of dietary fat are re-synthesized into triacylglycerol, which is either secreted on chylomicrons or stored within cytoplasmic lipid droplets (CLDs). CLDs were originally thought to be inert stores of neutral lipids, but are now recognized as dynamic organelles that function in multiple cellular processes in addition to lipid metabolism. This review will highlight recent discoveries related to dietary fat absorption with an emphasis on the presence, synthesis, and metabolism of CLDs within this process.
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Affiliation(s)
- Theresa D'Aquila
- Department of Nutrition Science, Purdue University, West Lafayette, IN 47907, USA
| | - Yu-Han Hung
- Department of Nutrition Science, Purdue University, West Lafayette, IN 47907, USA
| | - Alicia Carreiro
- Department of Nutrition Science, Purdue University, West Lafayette, IN 47907, USA
| | - Kimberly K Buhman
- Department of Nutrition Science, Purdue University, West Lafayette, IN 47907, USA.
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28
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Utzschneider KM, Kratz M, Damman CJ, Hullar M. Mechanisms Linking the Gut Microbiome and Glucose Metabolism. J Clin Endocrinol Metab 2016; 101:1445-54. [PMID: 26938201 PMCID: PMC4880177 DOI: 10.1210/jc.2015-4251] [Citation(s) in RCA: 135] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
This review details potential mechanisms linking gut dysbiosis to metabolic dysfunction, including lipopolysaccharide, bile acids, short chain fatty acids, gut hormones, and branched-chain amino acids.
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Affiliation(s)
- Kristina M Utzschneider
- Division of Metabolism, Endocrinology and Nutrition (K.M.U.), Department of Medicine, VA Puget Sound Health Care System and the University of Washington, Seattle, Washington; Division of Public Health Sciences (M.K.), Fred Hutchinson Cancer Research Center, and the Department of Epidemiology, University of Washington, Seattle, Washington; Division of Gastroenterology (C.J.D.), Department of Medicine, University of Washington, Seattle, Washington; and Division of Public Health Sciences (M.H.), Fred Hutchinson Cancer Research Center, Seattle, Washington
| | - Mario Kratz
- Division of Metabolism, Endocrinology and Nutrition (K.M.U.), Department of Medicine, VA Puget Sound Health Care System and the University of Washington, Seattle, Washington; Division of Public Health Sciences (M.K.), Fred Hutchinson Cancer Research Center, and the Department of Epidemiology, University of Washington, Seattle, Washington; Division of Gastroenterology (C.J.D.), Department of Medicine, University of Washington, Seattle, Washington; and Division of Public Health Sciences (M.H.), Fred Hutchinson Cancer Research Center, Seattle, Washington
| | - Chris J Damman
- Division of Metabolism, Endocrinology and Nutrition (K.M.U.), Department of Medicine, VA Puget Sound Health Care System and the University of Washington, Seattle, Washington; Division of Public Health Sciences (M.K.), Fred Hutchinson Cancer Research Center, and the Department of Epidemiology, University of Washington, Seattle, Washington; Division of Gastroenterology (C.J.D.), Department of Medicine, University of Washington, Seattle, Washington; and Division of Public Health Sciences (M.H.), Fred Hutchinson Cancer Research Center, Seattle, Washington
| | - Meredith Hullar
- Division of Metabolism, Endocrinology and Nutrition (K.M.U.), Department of Medicine, VA Puget Sound Health Care System and the University of Washington, Seattle, Washington; Division of Public Health Sciences (M.K.), Fred Hutchinson Cancer Research Center, and the Department of Epidemiology, University of Washington, Seattle, Washington; Division of Gastroenterology (C.J.D.), Department of Medicine, University of Washington, Seattle, Washington; and Division of Public Health Sciences (M.H.), Fred Hutchinson Cancer Research Center, Seattle, Washington
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29
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Kerr BJ, Kellner TA, Shurson GC. Characteristics of lipids and their feeding value in swine diets. J Anim Sci Biotechnol 2015; 6:30. [PMID: 26207182 PMCID: PMC4512021 DOI: 10.1186/s40104-015-0028-x] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Accepted: 06/10/2015] [Indexed: 01/14/2023] Open
Abstract
In livestock diets, energy is one of the most expensive nutritional components of feed formulation. Because lipids are a concentrated energy source, inclusion of lipids are known to affect growth rate and feed efficiency, but are also known to affect diet palatability, feed dustiness, and pellet quality. In reviewing the literature, the majority of research studies conducted on the subject of lipids have focused mainly on the effects of feeding presumably high quality lipids on growth performance, digestion, and metabolism in young animals. There is, however, the wide array of composition and quality differences among lipid sources available to the animal industry making it essential to understand differences in lipid composition and quality factors affecting their digestion and metabolism more fully. In addition there is often confusion in lipid nomenclature, measuring lipid content and composition, and evaluating quality factors necessary to understand the true feeding value to animals. Lastly, advances in understanding lipid digestion, post-absorption metabolism, and physiological processes (e.g., cell division and differentiation, immune function and inflammation); and in metabolic oxidative stress in the animal and lipid peroxidation, necessitates a more compressive assessment of factors affecting the value of lipid supplementation to livestock diets. The following review provides insight into lipid classification, digestion and absorption, lipid peroxidation indices, lipid quality and nutritional value, and antioxidants in growing pigs.
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Affiliation(s)
- Brian J. Kerr
- />USDA-ARS-National Laboratory for Agriculture and the Environment, Ames, IA 50011 USA
| | - Trey A. Kellner
- />Department of Animal Science, Iowa State University, Ames, IA 50011 USA
| | - Gerald C. Shurson
- />Department of Animal Science, University of Minnesota, St. Paul, MN 55108 USA
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30
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Saito K, Katada T. Mechanisms for exporting large-sized cargoes from the endoplasmic reticulum. Cell Mol Life Sci 2015; 72:3709-20. [PMID: 26082182 PMCID: PMC4565863 DOI: 10.1007/s00018-015-1952-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2015] [Revised: 05/18/2015] [Accepted: 06/08/2015] [Indexed: 12/14/2022]
Abstract
Cargo proteins exported from the endoplasmic reticulum to the Golgi apparatus are typically transported in coat protein complex II (COPII)-coated vesicles of 60–90 nm diameter. Several cargo molecules including collagens and chylomicrons form structures that are too large to be accommodated by these vesicles, but their secretion still requires COPII proteins. Here, we first review recent progress on large cargo secretions derived especially from animal models and human diseases, which indicate the importance of COPII proteins. We then discuss the recent isolation of specialized factors that modulate the process of COPII-dependent cargo formation to facilitate the exit of large-sized cargoes from the endoplasmic reticulum. Based on these findings, we propose a model that describes the importance of the GTPase cycle for secretion of oversized cargoes. Next, we summarize reports that describe the structures of COPII proteins and how these results provide insight into the mechanism of assembly of the large cargo carriers. Finally, we discuss what issues remain to be solved in the future.
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Affiliation(s)
- Kota Saito
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
| | - Toshiaki Katada
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
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31
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Abstract
Accumulation of triacylglycerols within the cytoplasm of hepatocytes to the degree that lipid droplets are visible microscopically is called liver steatosis. Most commonly, it occurs when there is an imbalance between the delivery or synthesis of fatty acids in the liver and their disposal through oxidative pathways or secretion into the blood as a component of triacylglycerols in very low density lipoprotein. This disorder is called nonalcoholic fatty liver disease (NAFLD) in the absence of alcoholic abuse and viral hepatitis, and it is often associated with insulin resistance, obesity and type 2 diabetes. Also, liver steatosis can be induced by many other causes including excessive alcohol consumption, infection with genotype 3 hepatitis C virus and certain medications. Whereas hepatic triacylglycerol accumulation was once considered the ultimate effector of hepatic lipotoxicity, triacylglycerols per se are quite inert and do not induce insulin resistance or cellular injury. Rather, lipotoxic injury in the liver appears to be mediated by the global ongoing fatty acid enrichment in the liver, paralleling the development of insulin resistance. A considerable number of fatty acid metabolites may be responsible for hepatic lipotoxicity and liver injury. Additional key contributors include hepatic cytosolic lipases and the "lipophagy" of lipid droplets, as sources of hepatic fatty acids. The specific origin of the lipids, mainly triacylglycerols, accumulating in liver has been unraveled by recent kinetic studies, and identifying the origin of the accumulated triacylglycerols in the liver of patients with NAFLD may direct the prevention and treatment of this condition.
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Affiliation(s)
- David Q-H Wang
- Department of Internal Medicine, Division of Gastroenterology and Hepatology, Saint Louis University School of Medicine, St. Louis, Missouri
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32
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Beznoussenko GV, Parashuraman S, Rizzo R, Polishchuk R, Martella O, Di Giandomenico D, Fusella A, Spaar A, Sallese M, Capestrano MG, Pavelka M, Vos MR, Rikers YGM, Helms V, Mironov AA, Luini A. Transport of soluble proteins through the Golgi occurs by diffusion via continuities across cisternae. eLife 2014; 3:e02009. [PMID: 24867214 PMCID: PMC4070021 DOI: 10.7554/elife.02009] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Accepted: 05/25/2014] [Indexed: 12/18/2022] Open
Abstract
The mechanism of transport through the Golgi complex is not completely understood, insofar as no single transport mechanism appears to account for all of the observations. Here, we compare the transport of soluble secretory proteins (albumin and α1-antitrypsin) with that of supramolecular cargoes (e.g., procollagen) that are proposed to traverse the Golgi by compartment progression-maturation. We show that these soluble proteins traverse the Golgi much faster than procollagen while moving through the same stack. Moreover, we present kinetic and morphological observations that indicate that albumin transport occurs by diffusion via intercisternal continuities. These data provide evidence for a transport mechanism that applies to a major class of secretory proteins and indicate the co-existence of multiple intra-Golgi trafficking modes.
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Affiliation(s)
- Galina V Beznoussenko
- Fondazione IFOM, Istituto FIRC di Oncologia Molecolare (IFOM-IEO Campus), Milan, Italy
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
| | - Seetharaman Parashuraman
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
- Institute of Protein Biochemistry, Consiglio Nazionale Delle Ricerche (CNR-IBP), Naples, Italy
| | - Riccardo Rizzo
- Institute of Protein Biochemistry, Consiglio Nazionale Delle Ricerche (CNR-IBP), Naples, Italy
| | - Roman Polishchuk
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
- Telethon Institute for Genetics and Medicine (TIGEM), Naples, Italy
| | - Oliviano Martella
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
| | - Daniele Di Giandomenico
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
| | - Aurora Fusella
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
| | - Alexander Spaar
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
| | - Michele Sallese
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
| | - Maria Grazia Capestrano
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
| | - Margit Pavelka
- Department of Cell Biology and Ultrastructure Research, Center for Anatomy and Cell Biology, Medical University of Vienna, Vienna, Austria
| | | | | | - Volkhard Helms
- Center for Bioinformatics, Saarland University, Saarbruecken, Germany
| | - Alexandre A Mironov
- Fondazione IFOM, Istituto FIRC di Oncologia Molecolare (IFOM-IEO Campus), Milan, Italy
| | - Alberto Luini
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
- Institute of Protein Biochemistry, Consiglio Nazionale Delle Ricerche (CNR-IBP), Naples, Italy
- Telethon Institute for Genetics and Medicine (TIGEM), Naples, Italy
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33
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Abstract
In mammalian cells, the Golgi complex has an elaborate structure consisting of stacked, flattened cisternal membranes collected into a ribbon in the center of the cell. Amazingly, the flattened cisternae can rapidly dilate to accommodate large cargo as it traffics through the organelle. The mechanism by which this occurs is unknown. Exocytosis of large cargo is essential for many physiological processes, including collagen and lipoprotein secretion, and defects in the process lead to disease. In addition, enveloped viruses that bud into the endoplasmic reticulum or Golgi complex must also be transported through Golgi cisternae for secretion from the infected cell. This review summarizes our understanding of intra-Golgi transport of large cargo, and outlines current questions open for experimentation.
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Affiliation(s)
- Carolyn E Machamer
- Department of Cell Biology, Johns Hopkins University School of Medicine, 725 N. Wolfe St., Baltimore, MD 20205, USA.
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34
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Seyer A, Cantiello M, Bertrand-Michel J, Roques V, Nauze M, Bézirard V, Collet X, Touboul D, Brunelle A, Coméra C. Lipidomic and spatio-temporal imaging of fat by mass spectrometry in mice duodenum during lipid digestion. PLoS One 2013; 8:e58224. [PMID: 23560035 PMCID: PMC3616127 DOI: 10.1371/journal.pone.0058224] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Accepted: 02/01/2013] [Indexed: 11/19/2022] Open
Abstract
Intestinal absorption of dietary fat is a complex process mediated by enterocytes leading to lipid assembly and secretion of circulating lipoproteins as chylomicrons, vLDL and intestinal HDL (iHDL). Understanding lipid digestion is of importance knowing the correlation between excessive fat absorption and atherosclerosis. By using time-of-flight secondary ion mass spectrometry (TOF-SIMS), we illustrated a spatio-temporal localization of fat in mice duodenum, at different times of digestion after a lipid gavage, for the first time. Fatty acids progressively increased in enterocytes as well as taurocholic acid, secreted by bile and engaged in the entero-hepatic re-absorption cycle. Cytosolic lipid droplets (CLD) from enterocytes were originally purified separating chylomicron-like, intermediate droplets and smaller HDL-like. A lipidomic quantification revealed their contents in triglycerides, free and esterified cholesterol, phosphatidylcholine, sphingomyelin and ceramides but also in free fatty acids, mono- and di-acylglycerols. An acyl-transferase activity was identified and the enzyme monoacylglycerol acyl transferase 2 (MGAT2) was immunodetected in all CLD. The largest droplets was also shown to contain the microsomal triglyceride transfer protein (MTTP), the acyl-coenzyme A-cholesterol acyltransferases (ACAT) 1 and 2, hormone sensitive lipase (HSL) and adipose triglyceride lipase (ATGL). This highlights the fact that during the digestion of fats, enterocyte CLD contain some enzymes involved in the different stages of the metabolism of diet fatty acids and cholesterol, in anticipation of the crucial work of endoplasmic reticulum in the process. The data further underlines the dual role of chylomicrons and iHDL in fat digestion which should help to efficiently complement lipid-lowering therapy.
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Affiliation(s)
- Alexandre Seyer
- Centre de Recherche de Gif, Institut de Chimie des Substances Naturelles, Centre National de la Recherche Scientifique (CNRS), Gif-sur-Yvette, France
| | - Michela Cantiello
- Institut National de la Santé et de la Recherche Médicale (INSERM) U563, Hôpital Purpan, Toulouse, France
| | - Justine Bertrand-Michel
- Institut National de la Santé et de la Recherche Médicale U1048, Hôpital Rangueil, Toulouse, France
| | - Véronique Roques
- Institut National de la Santé et de la Recherche Médicale U1048, Hôpital Rangueil, Toulouse, France
| | - Michel Nauze
- Institut National de la Santé et de la Recherche Médicale U1048, Hôpital Rangueil, Toulouse, France
| | - Valérie Bézirard
- Institut National de la Recherche Agronomique (INRA) UMR 1331, TOXALIM, Toulouse, France
| | - Xavier Collet
- Institut National de la Santé et de la Recherche Médicale U1048, Hôpital Rangueil, Toulouse, France
| | - David Touboul
- Centre de Recherche de Gif, Institut de Chimie des Substances Naturelles, Centre National de la Recherche Scientifique (CNRS), Gif-sur-Yvette, France
| | - Alain Brunelle
- Centre de Recherche de Gif, Institut de Chimie des Substances Naturelles, Centre National de la Recherche Scientifique (CNRS), Gif-sur-Yvette, France
| | - Christine Coméra
- Institut National de la Santé et de la Recherche Médicale (INSERM) U563, Hôpital Purpan, Toulouse, France
- Institut National de la Recherche Agronomique (INRA) UMR 1331, TOXALIM, Toulouse, France
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35
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Caricilli AM, Saad MJA. The role of gut microbiota on insulin resistance. Nutrients 2013; 5:829-51. [PMID: 23482058 PMCID: PMC3705322 DOI: 10.3390/nu5030829] [Citation(s) in RCA: 150] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Revised: 01/10/2013] [Accepted: 01/15/2013] [Indexed: 12/12/2022] Open
Abstract
The development of obesity and insulin resistance has been extensively studied in the last decades, but the mechanisms underlying these alterations are still not completely understood. The gut microbiota has been identified as a potential contributor to metabolic diseases. It has been shown that obese individuals present different proportions of bacterial phyla compared with lean individuals, with an increase in Firmicutes and Actinobacteria and a decrease in Bacteroidetes. This alteration seems to interfere with intestinal permeability, increasing the absorption of lipopolysaccharide (LPS), which reaches circulation and initiates activation of Toll-like receptor (TLR) 4 and 2 and LPS receptor CD14, leading to increased activation of inflammatory pathways. With these activations, an impairment of the insulin signaling is observed, with decreased phosphorylation of the insulin receptor, insulin receptor substrate (IRS) and Akt, as well as increased inhibitory serine phosphorylation of IRS-1. Altered proportions of bacterial phyla have also been demonstrated to interfere with host’s biochemical pathways, increasing energy extraction and depot in adipose tissue. Therefore, understanding the mechanisms by which the alteration in the gut microbiota produces different signaling activations and phenotype changes may offer an interesting opportunity for the treatment of obesity and type 2 diabetes.
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Affiliation(s)
- Andrea M. Caricilli
- Department of Immunology, ICB IV, University of São Paulo, Av. Prof. Lineu Prestes, 2415, Cidade Universitária, São Paulo, SP, Brazil; E-Mail:
| | - Mario J. A. Saad
- Department of Internal Medicine, State University of Campinas, Rua Tessália Vieira de Camargo, 126, Cidade Universitária, Campinas, SP, Brazil
- Author to whom correspondence should be addressed; E-Mail: ; Tel./Fax: +55-19-35218950
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36
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Kohan AB, Howles PN, Tso P. Methods for studying rodent intestinal lipoprotein production and metabolism. ACTA ACUST UNITED AC 2012; 2:219-230. [PMID: 23024926 DOI: 10.1002/9780470942390.mo120049] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Lipid absorption begins with the digestion of dietary triacylglycerol and ultimately results in the secretion of triacylglycerol in chylomicrons into the lymphatics. Additionally, the intestine also secretes numerous proteins and peptides involved in lipid and lipoprotein metabolism in response to food. Ultimately, chylomicrons and these proteins, peptides, and hormones are found in lymph. The lymph fistula rat model has traditionally been used to study this intestinal absorption of nutrients, especially lipids, but recently, this model has also been used for studying the secretion of hormones by the small intestine. The protocols described in this article include the lymph fistula rat and mouse model, as well as in vivo chylomicron metabolism studies. These experimental models are helpful for the study of metabolic phenotypes, the characterization of intestinal lipid absorption and transport, and determining peripheral metabolism of intestinally derived lipoproteins.
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Affiliation(s)
- Alison B Kohan
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, OH, 45237
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37
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The coronavirus E protein: assembly and beyond. Viruses 2012; 4:363-82. [PMID: 22590676 PMCID: PMC3347032 DOI: 10.3390/v4030363] [Citation(s) in RCA: 193] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2011] [Revised: 02/18/2012] [Accepted: 02/27/2012] [Indexed: 12/14/2022] Open
Abstract
The coronavirus E protein is a small membrane protein that has an important role in the assembly of virions. Recent studies have indicated that the E protein has functions during infection beyond assembly, including in virus egress and in the host stress response. Additionally, the E protein has ion channel activity, interacts with host proteins, and may have multiple membrane topologies. The goal of this review is to highlight the properties and functions of the E protein, and speculate on how they may be related.
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38
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Kohan AB, Yoder SM, Tso P. Using the lymphatics to study nutrient absorption and the secretion of gastrointestinal hormones. Physiol Behav 2011; 105:82-8. [PMID: 21605578 PMCID: PMC3179774 DOI: 10.1016/j.physbeh.2011.04.056] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Revised: 04/25/2011] [Accepted: 04/27/2011] [Indexed: 12/31/2022]
Abstract
The lymph fistula rat model has traditionally been used to study the intestinal absorption of nutrients, especially lipids, but recently this model has also been used for studying the secretion of incretin hormones by the small intestine. The small intestine is not only responsible for the digestion and transport of dietary triacylglycerol, through the formation of chylomicrons, but it also secretes the incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) from enteroendocrine cells. Ultimately, both chylomicrons and incretins are found in lymph. Advantages of the lymph fistula rat model in studying chylomicron and incretin secretion are numerous and include: 1) the concentrations of incretin hormones are higher in lymph than in peripheral or portal plasma; 2) there is reduced degradation of incretin hormones by DPP-IV in the lymph compartment; 3) less dilution by the circulating fluid; 4) this model allows the continuous collection of lymph from conscious animals, eliminating any potential side effects on lymph flow and gastrointestinal function due to anesthesia; and finally, and perhaps most importantly, and 5) the concentration in the intestinal lymph provides a physiologically accurate representation of the hormonal milieu within the intestinal mucosa where incretins may interact with enteroendocrine and/or dendritic cells and signal through the enteric or autonomic neurons. The importance of GIP and GLP-1 in health and disease is becoming more apparent, especially as the prevalence of type 2 diabetes and other metabolic disorders increases. This review focuses on the use of the lymph fistula rat as a model to study the secretion of incretins, as well as dietary lipid.
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Affiliation(s)
- Alison B. Kohan
- Department of Pathology, College of Medicine Metabolic Diseases Institute University of Cincinnati 2180 E. Galbraith Road, ML 0507, Cincinnati, OH 45237
| | - Stephanie M. Yoder
- Department of Pediatrics, Herman B. Wells Center for Pediatric Research Indiana University School of Medicine 635 Barnhill Drive, MS 2055 Indianapolis, IN 46202
| | - Patrick Tso
- Department of Pathology, College of Medicine Metabolic Diseases Institute University of Cincinnati 2180 E. Galbraith Road, ML 0507, Cincinnati, OH 45237
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39
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Uptake of phenothiazines by the harvested chylomicrons ex vivo model: Influence of self-nanoemulsifying formulation design. Eur J Pharm Biopharm 2011; 79:171-80. [DOI: 10.1016/j.ejpb.2011.01.025] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2010] [Revised: 01/27/2011] [Accepted: 01/31/2011] [Indexed: 11/19/2022]
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40
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Granger DN, Kvietys PR, Korthuis RJ, Premen AJ. Microcirculation of the intestinal mucosa. Compr Physiol 2011. [DOI: 10.1002/cphy.cp060139] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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41
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Abstract
Right from birth, the lymphatics play a crucial role in dietary functions. A majority of the lipid absorbed from the newborn's lipid-rich diet enters the blood circulation through the lymphatic system, which transports triglyceride-loaded particles known as chylomicrons from the villi of the small intestine to the venous circulation near the heart. In light of the significance of this role, as well as the fact that lipid transport from the gut was one of the earliest discovered functions of the lymphatic vasculature, it is surprising that so little is known about how chylomicrons initially gain access to the lymphatic vessel. This review will focus on the current mechanisms thought to be important in this process and highlight important questions that need to be answered in the future.
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Affiliation(s)
- J Brandon Dixon
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA.
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42
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Kohan A, Yoder S, Tso P. Lymphatics in intestinal transport of nutrients and gastrointestinal hormones. Ann N Y Acad Sci 2010; 1207 Suppl 1:E44-51. [PMID: 20961305 DOI: 10.1111/j.1749-6632.2010.05753.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The lymph fistula rat has been used for studying intestinal absorption of nutrients, especially lipids. Lipid absorption begins with the digestion of triacylglycerol (TAG) to form 2-monoacylglycerol (2-MAG) and fatty acids (FA), which are then incorporated in bile salt-mixed micelles. The mixed micelles deliver these digestion products to enterocytes for uptake. There, 2-MAG and FA are re-esterified to form TAG, which is then incorporated into chylomicrons (CMs) to be carried by the lymphatic system. Coincident with CMs' secretion into lymph, the small intestine also secretes incretin hormones. Advantages of the lymph fistula model in studying CMs and incretin secretion include the following: (1) the animal being conscious, (2) much less dilution of CMs and incretins than in portal blood, and (3) fewer degrading enzymes than portal blood, e.g., dipeptidyl peptidase-IV. Examples of the lymph fistula model being used for studying CMs' transport in normal and pathophysiologic states are presented. Recently, the lymph fistula rat has also been used for studying the secretion of incretins by the small intestine.
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Affiliation(s)
- Alison Kohan
- Department of Pathology, University of Cincinnati Medical Center, Cincinnati, Ohio 45237, USA
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43
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Caesar R, Fåk F, Bäckhed F. Effects of gut microbiota on obesity and atherosclerosis via modulation of inflammation and lipid metabolism. J Intern Med 2010; 268:320-8. [PMID: 21050286 DOI: 10.1111/j.1365-2796.2010.02270.x] [Citation(s) in RCA: 195] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Recent studies have revealed a close relationship between inflammatory and metabolic pathways, and inflammation is now recognized to have a major role in obesity and metabolic diseases such as insulin resistance and atherosclerosis. The human body is home to a large number of distinct microbial communities, with the densest population in the distal gut (the gut microbiota). Bacteria have long been known to activate inflammatory pathways, and recent data demonstrate that the gut microbiota may affect lipid metabolism and function as an environmental factor that influences the development of obesity and related diseases. Here, we review how the gut microbiota may affect metabolic diseases by activating the innate immune system.
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Affiliation(s)
- R Caesar
- Department of Molecular and Clinical Medicine, Sahlgrenska Center for Cardiovascular and Metabolic Research/Wallenberg Laboratory, University of Gothenburg, Gothenburg, Sweden
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44
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Rémillard-Labrosse G, Lippé R. Meeting of conventional and unconventional pathways at the TGN. Commun Integr Biol 2010; 2:434-6. [PMID: 19907711 DOI: 10.4161/cib.2.5.9217] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2009] [Accepted: 06/05/2009] [Indexed: 11/19/2022] Open
Abstract
The biosynthetic pathway allows the transport of newly synthesized proteins to the TGN via the reticulum endoplasmic and Golgi apparatus. However, many large particles reach the TGN by unconventional means. For instance, Herpes simplex virus type 1(HSV-1) capsids assemble within the nucleus, bud into the perinuclear space, fuse with the outer nuclear membrane and finally travel unenveloped towards the TGN. Given the central role of protein kinase D in the transport of small cargo from the TGN to the cell surface, we probed its potential contribution in HSV-1 egress, as a model for studying large cargo exiting from the TGN. Using a synchronized infection, we show that inactivation of protein kinase D with pharmacological inhibitors, a kinase dead mutant or siRNA all causes the retention of HSV-1 at the TGN. This highlights the role of PKD in viral exit and a dependence of the virus on the classical host cell machinery to leave the TGN, unlike its previous transport steps. Conceptually, this supports a model in which the TGN is a meeting point where conventional and unconventional routes encounter.
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45
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46
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Rémillard-Labrosse G, Mihai C, Duron J, Guay G, Lippé R. Protein kinase D-dependent trafficking of the large Herpes simplex virus type 1 capsids from the TGN to plasma membrane. Traffic 2009; 10:1074-83. [PMID: 19548982 DOI: 10.1111/j.1600-0854.2009.00939.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The biosynthetic pathway carries cargos from the endoplasmic reticulum (ER) to the trans Golgi network (TGN) via a typical passage through the Golgi. Interestingly, large particles such as procollagen, chylomicrons and some viruses all reach the TGN by atypical routes. Given this dichotomy, we anticipated that such cargos might rely on non-classical machineries downstream of the TGN. Using Herpes simplex virus type 1 (HSV-1) as a model and a synchronized infection protocol that focuses on TGN to plasma membrane transport, the present study revealed the surprising implication of the cellular serine-threonine protein kinase D in HSV-1 egress. These findings, confirmed by a variety of complementary means [pharmacological inhibitors, dominant negative mutant, RNA interference and electron microscopy (EM)], identify one of possibly several cellular factors that modulate the egress of viruses transiting at the TGN. Moreover, the involvement of this kinase, previously known to regulate the transport of small basolateral cargos, highlights the trafficking of both small and exceptionally large entities by a common machinery downstream of the TGN, in sharp contrast to earlier steps of transport. Conceptually, this indicates the TGN is not only a sorting station from which cargos can depart towards different destinations but also a meeting point where conventional and unconventional routes can meet along the biosynthetic pathway. Lastly, given the apical release of HSV-1 in neurons, it opens up the possibility that this kinase might regulate some apical sorting.
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Ghoshal S, Witta J, Zhong J, de Villiers W, Eckhardt E. Chylomicrons promote intestinal absorption of lipopolysaccharides. J Lipid Res 2008; 50:90-7. [PMID: 18815435 DOI: 10.1194/jlr.m800156-jlr200] [Citation(s) in RCA: 448] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Recent data suggest that dietary fat promotes intestinal absorption of lipopolysaccharides (LPS) from the gut microflora, which might contribute to various inflammatory disorders. The mechanism of fat-induced LPS absorption is unclear, however. Intestinal-epithelial cells can internalize LPS from the apical surface and transport LPS to the Golgi. The Golgi complex also contains newly formed chylomicrons, the lipoproteins that transport dietary long-chain fat through mesenteric lymph and blood. Because LPS has affinity for chylomicrons, we hypothesized that chylomicron formation promotes LPS absorption. In agreement with our hypothesis, we found that CaCo-2 cells released more cell-associated LPS after incubation with oleic-acid (OA), a long-chain fatty acid that induces chylomicron formation, than with butyric acid (BA), a short-chain fatty acid that does not induce chylomicron formation. Moreover, the effect of OA was blocked by the inhibitor of chylomicron formation, Pluronic L-81. We also observed that intragastric triolein (TO) gavage was followed by increased plasma LPS, whereas gavage with tributyrin (TB), or TO plus Pluronic L-81, was not. Most intestinally absorbed LPS was present on chylomicron remnants (CM-R) in the blood. Chylomicron formation also promoted transport of LPS through mesenteric lymph nodes (MLN) and the production of TNFalpha mRNA in the MLN. Together, our data suggest that intestinal epithelial cells may release LPS on chylomicrons from cell-associated pools. Chylomicron-associated LPS may contribute to postprandial inflammatory responses or chronic diet-induced inflammation in chylomicron target tissues.
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Affiliation(s)
- Sarbani Ghoshal
- Department of Internal Medicine, Division of Digestive Diseases and Nutrition, University of Kentucky, Lexington, KY, USA
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Trevaskis NL, Charman WN, Porter CJ. Lipid-based delivery systems and intestinal lymphatic drug transport: a mechanistic update. Adv Drug Deliv Rev 2008; 60:702-16. [PMID: 18155316 PMCID: PMC7103284 DOI: 10.1016/j.addr.2007.09.007] [Citation(s) in RCA: 277] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2007] [Accepted: 09/30/2007] [Indexed: 12/11/2022]
Abstract
After oral administration, the majority of drug molecules are absorbed across the small intestine and enter the systemic circulation via the portal vein and the liver. For some highly lipophilic drugs (typically log P > 5, lipid solubility > 50 mg/g), however, association with lymph lipoproteins in the enterocyte leads to transport to the systemic circulation via the intestinal lymph. The attendant delivery benefits associated with lymphatic drug transport include a reduction in first-pass metabolism and lymphatic exposure to drug concentrations orders of magnitude higher than that attained in systemic blood. In the current review we briefly describe the mechanisms by which drug molecules access the lymph and the formulation strategies that may be utilised to enhance lymphatic drug transport. Specific focus is directed toward recent advances in understanding regarding the impact of lipid source (both endogenous and exogenous) and intracellular lipid trafficking pathways on lymphatic drug transport and enterocyte-based first-pass metabolism.
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Van Dyck F, Braem CV, Chen Z, Declercq J, Deckers R, Kim BM, Ito S, Wu MK, Cohen DE, Dewerchin M, Derua R, Waelkens E, Fiette L, Roebroek A, Schuit F, Van de Ven WJM, Shivdasani RA. Loss of the PlagL2 transcription factor affects lacteal uptake of chylomicrons. Cell Metab 2007; 6:406-13. [PMID: 17983586 DOI: 10.1016/j.cmet.2007.09.010] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2006] [Revised: 05/29/2007] [Accepted: 09/26/2007] [Indexed: 12/19/2022]
Abstract
Enterocytes assemble dietary lipids into chylomicron particles that are taken up by intestinal lacteal vessels and peripheral tissues. Although chylomicrons are known to assemble in part within membrane secretory pathways, the modifications required for efficient vascular uptake are unknown. Here we report that the transcription factor pleomorphic adenoma gene-like 2 (PlagL2) is essential for this aspect of dietary lipid metabolism. PlagL2(-/-) mice die from postnatal wasting owing to failure of fat absorption. Lipids modified in the absence of PlagL2 exit from enterocytes but fail to enter interstitial lacteal vessels. Dysregulation of enterocyte genes closely linked to intracellular membrane transport identified candidate regulators of critical steps in chylomicron assembly. PlagL2 thus regulates important aspects of dietary lipid absorption, and the PlagL2(-/-) animal model has implications for the amelioration of obesity and the metabolic syndrome.
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Affiliation(s)
- Frederik Van Dyck
- Department of Human Genetics, University of Leuven, B-3000 Leuven, Belgium
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Huang JD, Presley JB, Chimento MF, Curcio CA, Johnson M. Age-related changes in human macular Bruch's membrane as seen by quick-freeze/deep-etch. Exp Eye Res 2007; 85:202-18. [PMID: 17586493 PMCID: PMC2352152 DOI: 10.1016/j.exer.2007.03.011] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2007] [Revised: 03/22/2007] [Accepted: 03/29/2007] [Indexed: 10/23/2022]
Abstract
Lipid-containing inclusions have been observed in human Bruch's membrane (BrM) and are postulated to be associated with age-related maculopathy (ARM), a major cause of legal blindness in developed countries. The dehydration associated with specimen preparation for thin-section transmission electron microscopy causes loss of these inclusions. Better preservation of the ultrastructure of the inclusions and tissue is achieved by using a quick-freeze/deep-etch preparation. We use this technique to examine normal human macular BrM in order to characterize the deposition of the lipid-rich inclusions and their age-related accumulation within different layers of the tissue. We find that various inclusions mentioned in other studies can be formed by combinations of three basic structures: lipoprotein-like particles (LLPs), small granules (SGs) and membrane-like structures. These inclusions are associated with collagen and elastic fibrils by fine filaments. In younger eyes, these inclusions are found mostly in the elastic (EL) and outer collageneous layer (OCL) and occupy a small fraction of the interfibrillar spacing. As age increases, LLPs and SGs gradually fill the interfibrillar spacing of the EL and inner collageneous layer (ICL) of the tissue, and later form a new sublayer, the lipid wall, within the boundary region between the basal lamina of retinal pigment epithelium (RPE) and ICL. Because the formation of the lipid wall only occurs after these inclusions fill the ICL, and it seems unlikely that the LLPs can pass through the packed layer, this result suggests a possible RPE origin of the LLPs that make up the lipid wall.
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Affiliation(s)
- Jiahn-Dar Huang
- Department of Biomedical Engineering, Northwestern University, Evanston IL USA
| | - J. Brett Presley
- Department of Ophthalmology, University of Alabama School of Medicine, Birmingham AL USA
| | - Melissa F. Chimento
- Department of Ophthalmology, University of Alabama School of Medicine, Birmingham AL USA
| | - Christine A. Curcio
- Department of Ophthalmology, University of Alabama School of Medicine, Birmingham AL USA
| | - Mark Johnson
- Department of Biomedical Engineering, Northwestern University, Evanston IL USA
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