1
|
Omagari K, Maruta A, Yayama N, Yoshida Y, Okamoto K, Shirouchi B, Takeuchi S, Suruga K, Koba K, Ichimura-Shimizu M, Tsuneyama K. The Effects of Overnight Fasting Duration on Glucose and Lipid Metabolism in a Sprague-Dawley Rat Model of Nonalcoholic Steatohepatitis with Advanced Fibrosis. J Nutr Sci Vitaminol (Tokyo) 2023; 69:357-369. [PMID: 37940576 DOI: 10.3177/jnsv.69.357] [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: 11/10/2023]
Abstract
Nonalcoholic steatohepatitis (NASH) can progress to hepatic fibrosis, and is associated with cardiovascular and liver-related mortality. To understand the pathogenesis of NASH, reliable animal models of the disease are useful. In animal studies, the animals are usually fasted overnight before biospecimens are taken, but little is known about the effects of fasting. Here, we investigated the impact of overnight fasting for approximately 9 to 17 h on glucose and lipid metabolism in a Sprague-Dawley (SD) rat model of diet-induced moderate and advanced NASH in comparison to normal SD rats. Our results revealed that in the moderate NASH model rats, the fasting duration did not affect glucose and lipid metabolism, the histopathological findings, or the hepatic mRNA expression levels of genes related to lipid metabolism, cholesterol metabolism, inflammation, fibrosis, and oxidative stress. In contrast, in the normal rats, significant fasting time-dependent reductions were observed in the epididymal fat pad weight and the hepatic mRNA expression levels of adipose differentiation-related protein and heme oxygenase-1. Moreover, in the advanced NASH model rats, a significant fasting time-dependent reduction and increase were observed in the serum insulin level and mRNA expression level of alpha-smooth muscle actin, respectively. Our present results suggest that the influence of the overnight fasting duration differs among the healthy condition, moderate NASH, and advanced NASH statuses. Further studies are needed in humans to determine the appropriate overnight fasting duration for the accurate evaluation of glucose and lipid metabolism in NASH patients.
Collapse
Affiliation(s)
- Katsuhisa Omagari
- Department of Nutritional Science, Faculty of Nursing and Nutrition, University of Nagasaki
| | - Ayumi Maruta
- Department of Nutritional Science, Faculty of Nursing and Nutrition, University of Nagasaki
| | - Natsuki Yayama
- Department of Nutritional Science, Faculty of Nursing and Nutrition, University of Nagasaki
| | - Yuki Yoshida
- Department of Nutritional Science, Faculty of Nursing and Nutrition, University of Nagasaki
| | - Kyoko Okamoto
- Department of Nutritional Science, Faculty of Nursing and Nutrition, University of Nagasaki
| | - Bungo Shirouchi
- Department of Nutritional Science, Faculty of Nursing and Nutrition, University of Nagasaki
| | - Shouhei Takeuchi
- Department of Nutritional Science, Faculty of Nursing and Nutrition, University of Nagasaki
| | - Kazuhito Suruga
- Department of Nutritional Science, Faculty of Nursing and Nutrition, University of Nagasaki
| | - Kazunori Koba
- Department of Nutritional Science, Faculty of Nursing and Nutrition, University of Nagasaki
| | | | - Koichi Tsuneyama
- Department of Pathology and Laboratory Medicine, Tokushima University Graduate School
| |
Collapse
|
2
|
Singh J, Sanghavi P, Mallik R. Microtubule motor driven interactions of lipid droplets: Specificities and opportunities. Front Cell Dev Biol 2022; 10:893375. [PMID: 36200039 PMCID: PMC9527339 DOI: 10.3389/fcell.2022.893375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 09/05/2022] [Indexed: 11/29/2022] Open
Abstract
Lipid Droplets (LDs) are evolutionarily conserved cellular organelles that store neutral lipids such as triacylglycerol and cholesterol-esters. Neutral lipids are enclosed within the limiting membrane of the LD, which is a monolayer of phospholipids and is therefore fundamentally different from the bilayer membrane enclosing most other organelles. LDs have long been viewed as a storehouse of lipids needed on demand for generating energy and membranes inside cells. Outside this classical view, we are now realizing that LDs have significant roles in protein sequestration, supply of signalling lipids, viral replication, lipoprotein production and many other functions of important physiological consequence. To execute such functions, LDs must often exchange lipids and proteins with other organelles (e.g., the ER, lysosomes, mitochondria) via physical contacts. But before such exchanges can occur, how does a micron-sized LD with limited ability to diffuse around find its cognate organelle? There is growing evidence that motor protein driven motion of LDs along microtubules may facilitate such LD-organelle interactions. We will summarize some aspects of LD motion leading to LD-organelle contacts, how these change with metabolic state and pathogen infections, and also ask how these pathways could perhaps be targeted selectively in the context of disease and drug delivery. Such a possibility arises because the binding of motor proteins to the monolayer membrane on LDs could be different from motor binding to the membrane on other cellular organelles.
Collapse
Affiliation(s)
- Jagjeet Singh
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, India
- *Correspondence: Roop Mallik, ; Jagjeet Singh,
| | - Paulomi Sanghavi
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, India
| | - Roop Mallik
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India
- *Correspondence: Roop Mallik, ; Jagjeet Singh,
| |
Collapse
|
3
|
Sar1 Affects the Localization of Perilipin 2 to Lipid Droplets. Int J Mol Sci 2022; 23:ijms23126366. [PMID: 35742827 PMCID: PMC9223735 DOI: 10.3390/ijms23126366] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Revised: 06/03/2022] [Accepted: 06/03/2022] [Indexed: 02/05/2023] Open
Abstract
Lipid droplets (LDs) are intracellular organelles that are ubiquitous in many types of cells. The LD core consists of triacylglycerols (TGs) surrounded by a phospholipid monolayer and surface proteins such as perilipin 2 (PLIN2). Although TGs accumulate in the phospholipid bilayer of the endoplasmic reticulum (ER) and subsequently nascent LDs buds from ER, the mechanism by which LD proteins are transported to LD particles is not fully understood. Sar1 is a GTPase known as a regulator of coat protein complex Ⅱ (COPⅡ) vesicle budding, and its role in LD formation was investigated in this study. HuH7 human hepatoma cells were infected with adenoviral particles containing genes coding GFP fused with wild-type Sar1 (Sar1 WT) or a GTPase mutant form (Sar1 H79G). When HuH7 cells were treated with oleic acid, Sar1 WT formed a ring-like structure around the LDs. The transient expression of Sar1 did not significantly alter the levels of TG and PLIN2 in the cells. However, the localization of PLIN2 to the LDs decreased in the cells expressing Sar1 H79G. Furthermore, the effects of Sar1 on PLIN2 localization to the LDs were verified by the suppression of endogenous Sar1 using the short hairpin RNA technique. In conclusion, it was found that Sar1 has some roles in the intracellular distribution of PLIN2 to LDs in liver cells.
Collapse
|
4
|
Auclair N, Melbouci L, St-Pierre D, Levy E. Gastrointestinal factors regulating lipid droplet formation in the intestine. Exp Cell Res 2018; 363:1-14. [PMID: 29305172 DOI: 10.1016/j.yexcr.2017.12.031] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Revised: 12/28/2017] [Accepted: 12/29/2017] [Indexed: 12/22/2022]
Abstract
Cytoplasmic lipid droplets (CLD) are considered as neutral lipid reservoirs, which protect cells from lipotoxicity. It became clear that these fascinating dynamic organelles play a role not only in energy storage and metabolism, but also in cellular lipid and protein handling, inter-organelle communication, and signaling among diverse functions. Their dysregulation is associated with multiple disorders, including obesity, liver steatosis and cardiovascular diseases. The central aim of this review is to highlight the link between intra-enterocyte CLD dynamics and the formation of chylomicrons, the main intestinal dietary lipid vehicle, after overviewing the morphology, molecular composition, biogenesis and functions of CLD.
Collapse
Affiliation(s)
- N Auclair
- Research Centre, CHU Sainte-Justine and Department of Montreal, Quebec, Canada H3T 1C5; Nutrition, Université de Montréal, Montreal, Quebec, Canada H3T 1C5
| | - L Melbouci
- Research Centre, CHU Sainte-Justine and Department of Montreal, Quebec, Canada H3T 1C5; Department of Sciences and Physical Activities, UQAM, Quebec, Canada H2X 1Y4
| | - D St-Pierre
- Research Centre, CHU Sainte-Justine and Department of Montreal, Quebec, Canada H3T 1C5; Department of Sciences and Physical Activities, UQAM, Quebec, Canada H2X 1Y4
| | - E Levy
- Research Centre, CHU Sainte-Justine and Department of Montreal, Quebec, Canada H3T 1C5; Nutrition, Université de Montréal, Montreal, Quebec, Canada H3T 1C5; Institute of Nutrition and Functional Foods (INAF), Université Laval, Quebec, Quebec, Canada G1V 0A6.
| |
Collapse
|
5
|
Abstract
The liver secretes lipids in a controlled manner despite vast changes in its internal lipid content. This buffering function of the liver is essential for lipid/energy homeostasis, but its molecular and cellular mechanism is unknown. We show that motor protein kinesin transports lipid droplets (LDs) to the endoplasmic reticulum (ER) in liver cells, engineering ER−droplet contacts and supplying lipids to the ER for secretion as lipoprotein. However, when fasting induces massive lipid accumulation in liver, kinesin is removed from LDs, inhibiting lipid supply to the ER and homeostatically tempering lipid secretion from liver in a fasted state. Interestingly, reducing kinesin also blocks propagation of hepatitis-C virus inside liver cells, possibly because viral proteins cannot transfer from the ER to LDs. Despite massive fluctuations in its internal triglyceride content, the liver secretes triglyceride under tight homeostatic control. This buffering function is most visible after fasting, when liver triglyceride increases manyfold but circulating serum triglyceride barely fluctuates. How the liver controls triglyceride secretion is unknown, but is fundamentally important for lipid and energy homeostasis in animals. Here we find an unexpected cellular and molecular mechanism behind such control. We show that kinesin motors are recruited to triglyceride-rich lipid droplets (LDs) in the liver by the GTPase ARF1, which is a key activator of lipolysis. This recruitment is activated by an insulin-dependent pathway and therefore responds to fed/fasted states of the animal. In fed state, ARF1 and kinesin appear on LDs, consequently transporting LDs to the periphery of hepatocytes where the smooth endoplasmic reticulum (sER) is present. Because the lipases that catabolize LDs in hepatocytes reside on the sER, LDs can now be catabolized efficiently to provide triglyceride for lipoprotein assembly and secretion from the sER. Upon fasting, insulin is lowered to remove ARF1 and kinesin from LDs, thus down-regulating LD transport and sER–LD contacts. This tempers triglyceride availabiity for very low density lipoprotein assembly and allows homeostatic control of serum triglyceride in a fasted state. We further show that kinesin knockdown inhibits hepatitis-C virus replication in hepatocytes, likely because translated viral proteins are unable to transfer from the ER to LDs.
Collapse
|
6
|
Feeding-fasting dependent recruitment of membrane microdomain proteins to lipid droplets purified from the liver. PLoS One 2017; 12:e0183022. [PMID: 28800633 PMCID: PMC5553754 DOI: 10.1371/journal.pone.0183022] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Accepted: 07/30/2017] [Indexed: 01/23/2023] Open
Abstract
Lipid droplets (LDs) are cellular stores of neutral fat that facilitate lipid and protein trafficking in response to metabolic cues. Unlike other vesicles, the phospholipid membrane on the LD is a monolayer. Interestingly, this monolayer membrane has free cholesterol, and may therefore contain lipid microdomains that serve as a platform for assembling proteins involved in signal transduction, cell polarity, pathogen entry etc. In support of this, cell culture studies have detected microdomain-associated "raftophilic" proteins on LDs. However, the physiological significance of this observation has been unclear. Here we show that two proteins (Flotillin-1 and SNAP23) that bind to membrane microdomains associate differently with LDs purified from rat liver depending on the feeding/fasting state of the animal. Flotillin-1 increases on LDs in the fed state, possibly because LDs interact with the endoplasmic reticulum (ER), facilitating supply of flotillin-1 from ER to LDs. Interestingly, this increase in flotillin-1 is correlated with an increase in free cholesterol on the LDs in fed state. In opposite behaviour to flotillin-1, SNAP23 increases on LDs in the fasted state and this appears to mediate LD-mitochondria interactions. Such LD-mitochondria interactions may provide fatty acids to mitochondria for promoting beta-oxidation in hepatocytes in response to fasting. Our work brings out physiologically relevant aspects of lipid droplet biology that are different from, and may not be entirely possible to replicate and study in cell culture.
Collapse
|
7
|
Huang CW, Chen YJ, Yang JT, Chen CY, Ajuwon KM, Chen SE, Su NW, Chen YS, Mersmann HJ, Ding ST. Docosahexaenoic acid increases accumulation of adipocyte triacylglycerol through up-regulation of lipogenic gene expression in pigs. Lipids Health Dis 2017; 16:33. [PMID: 28173868 PMCID: PMC5297193 DOI: 10.1186/s12944-017-0428-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Accepted: 02/01/2017] [Indexed: 12/14/2022] Open
Abstract
Background Changing dietary fatty acid composition in modern diet influences the prevalence of obesity. Increasing evidences suggest favorable effects of n-3 PUFA for protecting against obesity and the metabolic syndrome. However, the regulation of n-3 PUFA in adipose is still unclear. Thus, this study addressed metabolism of different dietary fats in the adipose tissue of porcine model. Methods Eight-week-old cross-bred pigs were randomly assigned to three groups and fed a 2% fat diet for 30 days from either soybean oil (SBO), docosahexaenoic acid (DHA) or beef tallow. An in vitro experiment was conducted in which linoleic acid (LA), DHA or oleic acid (OA) were added to represent the major fatty acid in the SBO-, DHA- or BT- diets, respectively. Adipocytes size and lipid metabolism related genes were analyzed. Results Plasma triacylglycerol (TAG) was lower in DHA- than in BT-fed pigs, and the product of lipolysis, glycerol was highest in BT-fed pigs. In addition, expression of the lipolytic genes, adipose triglyceride lipase and hormone sensitive lipase was higher in BT-fed pigs and with OA treatment in vitro. DHA promoted protein kinase A activity in pigs without affecting lipolytic genes. Adipocyte cell sizes, TAG content and expression of lipogenic-related genes including, adipose differentiated related protein (ADRP) and diacylglycerol acyltransferase 1 (DGAT1) were elevated by DHA in vivo and in vitro, indicating DHA promoted adipogenesis to trap TAG in adipose tissue. Fatty acid β-oxidation genes were increased in the DHA-fed pigs. Conclusion This effect was partly explained by the effect of DHA to promote adipogenesis to trap TAG in adipocytes and also increase expression of genes involved in adipocyte fatty acid oxidation. Therefore, our results suggest a direct effect of DHA on adipocyte metabolism, resulting in TAG turnover and fatty acid dissipation to facilitate plasma lipid uptake from the circulation. Electronic supplementary material The online version of this article (doi:10.1186/s12944-017-0428-3) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Chao-Wei Huang
- Department of Animal Science and Technology, National Taiwan University, No.50, Ln. 155, Sec. 3, Keelung Rd., Da'an Dist, Taipei City, 10672, Taiwan
| | - Yu-Jen Chen
- Institute of Biotechnology, National Taiwan University, Taipei, 10672, Taiwan
| | - Jui-Ting Yang
- Department of Animal Science and Technology, National Taiwan University, No.50, Ln. 155, Sec. 3, Keelung Rd., Da'an Dist, Taipei City, 10672, Taiwan
| | - Ching-Yi Chen
- Department of Animal Science and Technology, National Taiwan University, No.50, Ln. 155, Sec. 3, Keelung Rd., Da'an Dist, Taipei City, 10672, Taiwan
| | - Kolapo M Ajuwon
- Department of Animal Sciences, Purdue University, West Lafayette, IN, 47907-2054, USA
| | - Shuen-Ei Chen
- Department of Animal Science, National Chung-Hsing University, Taichung, 40227, Taiwan
| | - Nan-Wei Su
- Department of Agricultural Chemistry, National Taiwan University, Taipei, 10672, Taiwan
| | - Yu-Shan Chen
- Department of Animal Science and Technology, National Taiwan University, No.50, Ln. 155, Sec. 3, Keelung Rd., Da'an Dist, Taipei City, 10672, Taiwan
| | - Harry J Mersmann
- Department of Animal Science and Technology, National Taiwan University, No.50, Ln. 155, Sec. 3, Keelung Rd., Da'an Dist, Taipei City, 10672, Taiwan
| | - Shih-Torng Ding
- Department of Animal Science and Technology, National Taiwan University, No.50, Ln. 155, Sec. 3, Keelung Rd., Da'an Dist, Taipei City, 10672, Taiwan. .,Institute of Biotechnology, National Taiwan University, Taipei, 10672, Taiwan.
| |
Collapse
|
8
|
Yamaguchi T, Fujikawa N, Nimura S, Tokuoka Y, Tsuda S, Aiuchi T, Kato R, Obama T, Itabe H. Characterization of lipid droplets in steroidogenic MLTC-1 Leydig cells: Protein profiles and the morphological change induced by hormone stimulation. Biochim Biophys Acta Mol Cell Biol Lipids 2015; 1851:1285-95. [PMID: 26143378 DOI: 10.1016/j.bbalip.2015.06.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Revised: 06/22/2015] [Accepted: 06/30/2015] [Indexed: 12/11/2022]
Abstract
Lipid droplets (LDs) are functional subcellular organelles involved in multiple intracellular processes. LDs are found in nearly all types of eukaryotic cells, but their properties are highly variable in different types of tissues. Steroidogenic cells synthesize steroid hormones de novo from the cholesterol deposited in cytosolic LDs. However, the roles of LD proteins in steroidogenesis under pituitary hormone stimulation have not been well elucidated. The protein profile of isolated LDs from the mouse Leydig tumor cell line MLTC-1 was distinct from that of hepatic cells or macrophages. By proteomic analysis of the components using mass spectrometry, two enzymes for steroidogenesis, 3β-hydroxysteroid dehydrogenase type 1 (3βHSD1) and 17 β-hydroxysteroid dehydrogenase type 11 (17βHSD11), were identified in two strong bands in the LD fractions. The LD fraction of MLTC-1 cells also included CYP11A1 and CYP17, suggesting that the LDs contain all the enzymes needed for testosterone synthesis. The steroidogenesis in Leydig cells is activated by luteinizing hormone through a PKA-dependent pathway. Stimulation of MLTC-1 cells with luteinizing hormone or 8-bromo-cAMP caused drastic changes in the morphology of the LDs in the MLTC-1 cells. Upon stimulation, large perinuclear LDs are turned into much smaller LDs and dispersed throughout the cytosol. These results raise the possibility that LDs are involved in a regulatory pathway of steroidogenesis, not just by serving as a storage depot for cholesterol esters, but also by providing enzymes and generating sites for enzymatic activity.
Collapse
Affiliation(s)
- Tomohiro Yamaguchi
- Division of Biological Chemistry, Department of Molecular Biology, Showa University School of Pharmacy, 1-5-8 Hatanodai, Shinagawa, Tokyo 142-8555, Japan.
| | - Noriyuki Fujikawa
- Division of Biological Chemistry, Department of Molecular Biology, Showa University School of Pharmacy, 1-5-8 Hatanodai, Shinagawa, Tokyo 142-8555, Japan
| | - Satomi Nimura
- Division of Biological Chemistry, Department of Molecular Biology, Showa University School of Pharmacy, 1-5-8 Hatanodai, Shinagawa, Tokyo 142-8555, Japan
| | - Yutaro Tokuoka
- Division of Biological Chemistry, Department of Molecular Biology, Showa University School of Pharmacy, 1-5-8 Hatanodai, Shinagawa, Tokyo 142-8555, Japan
| | - Sonoka Tsuda
- Division of Biological Chemistry, Department of Molecular Biology, Showa University School of Pharmacy, 1-5-8 Hatanodai, Shinagawa, Tokyo 142-8555, Japan
| | - Toshihiro Aiuchi
- Division of Biological Chemistry, Department of Molecular Biology, Showa University School of Pharmacy, 1-5-8 Hatanodai, Shinagawa, Tokyo 142-8555, Japan
| | - Rina Kato
- Division of Biological Chemistry, Department of Molecular Biology, Showa University School of Pharmacy, 1-5-8 Hatanodai, Shinagawa, Tokyo 142-8555, Japan
| | - Takashi Obama
- Division of Biological Chemistry, Department of Molecular Biology, Showa University School of Pharmacy, 1-5-8 Hatanodai, Shinagawa, Tokyo 142-8555, Japan
| | - Hiroyuki Itabe
- Division of Biological Chemistry, Department of Molecular Biology, Showa University School of Pharmacy, 1-5-8 Hatanodai, Shinagawa, Tokyo 142-8555, Japan.
| |
Collapse
|
9
|
Tuazon MA, McConnell TR, Wilson GJ, Anthony TG, Henderson GC. Intensity-dependent and sex-specific alterations in hepatic triglyceride metabolism in mice following acute exercise. J Appl Physiol (1985) 2015; 118:61-70. [PMID: 25257878 PMCID: PMC6195669 DOI: 10.1152/japplphysiol.00440.2014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Accepted: 09/24/2014] [Indexed: 01/14/2023] Open
Abstract
Precise regulation of hepatic triglyceride (TG) metabolism and secretion is critical for health, and exercise could play a significant role. We compared one session of high-intensity interval exercise (HIIE) vs. continuous exercise (CE) on hepatic TG metabolism. Female and male mice were assigned to CE, HIIE, or sedentary control (CON). HIIE was a 30-min session of 30-s running intervals (30 m/min) interspersed with 60-s walking periods (5 m/min). CE was a distance- and duration-matched run at 13.8 m/min. Hepatic content of TG and TG secretion rates, as well as expression of relevant genes/proteins, were measured at 3 h (day 1) and 28 h (day 2) postexercise. On day 1, hepatic [TG] in CE and HIIE were both elevated vs. CON in both sexes with an approximately twofold greater elevation in HIIE vs. CE in females. In both sexes, hepatic perilipin 2 (PLIN2) protein on day 1 was increased significantly by both exercise types with a significantly greater increase with HIIE than CE, whereas the increase in mRNA reached significance only after HIIE. On day 2 in both sexes the increases in hepatic TG and PLIN2 with exercise declined toward CON levels. Only HIIE on day 2 resulted in reduced hepatic TG secretion by ∼20% in females with no effect in males. Neither exercise modality altered AMPK signaling or microsomal triglyceride transfer protein expression. Females exhibited higher hepatic TG secretion than males in association with different expression levels of related metabolic enzymes. These intensity-dependent and sex-specific alterations following exercise may have implications for sex-based exercise prescription.
Collapse
Affiliation(s)
- Marc A Tuazon
- Department of Exercise Science, Rutgers University, New Brunswick, New Jersey; Center for Lipid Research, Rutgers University, New Brunswick, New Jersey
| | - Taylor R McConnell
- Department of Exercise Science, Rutgers University, New Brunswick, New Jersey; Center for Lipid Research, Rutgers University, New Brunswick, New Jersey
| | - Gabriel J Wilson
- Department of Nutritional Sciences, Rutgers University, New Brunswick, New Jersey; and Center for Lipid Research, Rutgers University, New Brunswick, New Jersey
| | - Tracy G Anthony
- Department of Nutritional Sciences, Rutgers University, New Brunswick, New Jersey; and Center for Lipid Research, Rutgers University, New Brunswick, New Jersey
| | - Gregory C Henderson
- Department of Exercise Science, Rutgers University, New Brunswick, New Jersey; Center for Lipid Research, Rutgers University, New Brunswick, New Jersey
| |
Collapse
|
10
|
Lemieux GA, Ashrafi K. Insights and challenges in using C. elegans for investigation of fat metabolism. Crit Rev Biochem Mol Biol 2014; 50:69-84. [PMID: 25228063 DOI: 10.3109/10409238.2014.959890] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
C. elegans provides a genetically tractable system for deciphering the homeostatic mechanisms that underlie fat regulation in intact organisms. Here, we provide an overview of the recent advances in the C. elegans fat field with particular attention to studies of C. elegans lipid droplets, the complex links between lipases, autophagy, and lifespan, and analyses of key transcriptional regulatory mechanisms that coordinate lipid homeostasis. These studies demonstrate the ancient origins of mammalian and C. elegans fat regulatory pathways and highlight how C. elegans is being used to identify and analyze novel lipid pathways that are then shown to function similarly in mammals. Despite its many advantages, study of fat regulation in C. elegans is currently faced with a number of conceptual and methodological challenges. We critically evaluate some of the assumptions in the field and highlight issues that we believe should be taken into consideration when interpreting lipid content data in C. elegans.
Collapse
Affiliation(s)
- George A Lemieux
- Department of Physiology, University of California , San Francisco, CA , USA
| | | |
Collapse
|
11
|
Elpek G&O. Cellular and molecular mechanisms in the pathogenesis of liver fibrosis: An update. World J Gastroenterol 2014; 20:7260-7276. [PMID: 24966597 PMCID: PMC4064072 DOI: 10.3748/wjg.v20.i23.7260] [Citation(s) in RCA: 242] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2013] [Revised: 02/08/2014] [Accepted: 05/26/2014] [Indexed: 02/06/2023] Open
Abstract
There have been considerable recent advances towards a better understanding of the complex cellular and molecular network underlying liver fibrogenesis. Recent data indicate that the termination of fibrogenic processes and the restoration of deficient fibrolytic pathways may allow the reversal of advanced fibrosis and even cirrhosis. Therefore, efforts have been made to better clarify the cellular and molecular mechanisms that are involved in liver fibrosis. Activation of hepatic stellate cells (HSCs) remains a central event in fibrosis, complemented by other sources of matrix-producing cells, including portal fibroblasts, fibrocytes and bone marrow-derived myofibroblasts. These cells converge in a complex interaction with neighboring cells to provoke scarring in response to persistent injury. Defining the interaction of different cell types, revealing the effects of cytokines on these cells and characterizing the regulatory mechanisms that control gene expression in activated HSCs will enable the discovery of new therapeutic targets. Moreover, the characterization of different pathways associated with different etiologies aid in the development of disease-specific therapies. This article outlines recent advances regarding the cellular and molecular mechanisms involved in liver fibrosis that may be translated into future therapies. The pathogenesis of liver fibrosis associated with alcoholic liver disease, non-alcoholic fatty liver disease and viral hepatitis are also discussed to emphasize the various mechanisms involved in liver fibrosis.
Collapse
|
12
|
Ohsaki Y, Suzuki M, Fujimoto T. Open Questions in Lipid Droplet Biology. ACTA ACUST UNITED AC 2014; 21:86-96. [DOI: 10.1016/j.chembiol.2013.08.009] [Citation(s) in RCA: 114] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2013] [Revised: 08/12/2013] [Accepted: 08/23/2013] [Indexed: 12/31/2022]
|
13
|
Barak P, Rai A, Rai P, Mallik R. Quantitative optical trapping on single organelles in cell extract. Nat Methods 2013; 10:68-70. [PMID: 23241632 PMCID: PMC3605797 DOI: 10.1038/nmeth.2287] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2012] [Accepted: 11/04/2012] [Indexed: 12/14/2022]
Abstract
We have developed an optical trapping method to precisely measure the force generated by motor proteins on single organelles of unknown size in cell extract. This approach, termed VMatch, permits the functional interrogation of native motor complexes. We apply VMatch to measure the force, number and activity of kinesin-1 on motile lipid droplets isolated from the liver of normally fed and food-deprived rats.
Collapse
Affiliation(s)
- Pradeep Barak
- Department of Biological Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road Mumbai – 400005, India
| | - Ashim Rai
- Department of Biological Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road Mumbai – 400005, India
| | - Priyanka Rai
- Department of Biological Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road Mumbai – 400005, India
| | - Roop Mallik
- Department of Biological Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road Mumbai – 400005, India
| |
Collapse
|