1
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Gugliucci A. Sugar and Dyslipidemia: A Double-Hit, Perfect Storm. J Clin Med 2023; 12:5660. [PMID: 37685728 PMCID: PMC10488931 DOI: 10.3390/jcm12175660] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Revised: 08/10/2023] [Accepted: 08/29/2023] [Indexed: 09/10/2023] Open
Abstract
The availability of sugar has expanded over the past 50 years, due to improved industrial processes and corn subsidies, particularly in the form of sweetened beverages. This correlates with a surge in the prevalence of cardiometabolic disorders, which has brought this issue back into the spotlight for public health. In this narrative review, we focus on the role of fructose in the genesis of cardiometabolic dyslipidemia (an increase in serum triglyceride-rich lipoproteins (TRL): VLDL, chylomicrons (CM), and their remnants) bringing together the most recent data on humans, which demonstrates the crucial interaction between glucose and fructose, increasing the synthesis while decreasing the catabolism of these particles in a synergistic downward spiral. After reviewing TRL metabolism, we discuss the fundamental principles governing the metabolism of fructose in the intestine and liver and the effects of dysregulated fructolysis, in conjunction with the activation of carbohydrate-responsive element-binding protein (ChREBP) by glucose and the resulting crosstalk. The first byproduct of fructose catabolism, fructose-1-P, is highlighted for its function as a signaling molecule that promotes fat synthesis. We emphasize the role of fructose/glucose interaction in the liver, which enhances de novo lipogenesis, triglyceride (TG) synthesis, and VLDL production. In addition, we draw attention to current research that demonstrates how fructose affects the activity of lipoprotein lipase by increasing the concentration of inhibitors such as apolipoprotein CIII (apoCIII) and angiopoietin-like protein 3 (ANGPTL3), which reduce the catabolism of VLDL and chylomicrons and cause the building up of their atherogenic remnants. The end outcome is a dual, synergistic, and harmful action that encourages atherogenesis. Thus, considering the growing concerns regarding the connection between sugar consumption and cardiometabolic disease, current research strongly supports the actions of public health organizations aimed at reducing sugar intake, including dietary guidance addressing "safe" limits for sugar consumption.
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Affiliation(s)
- Alejandro Gugliucci
- Glycation, Oxidation and Disease Laboratory, Touro University California, Vallejo, CA 94592, USA
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2
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Papadea P, Skipitari M, Kalaitzopoulou E, Varemmenou A, Spiliopoulou M, Papasotiriou M, Papachristou E, Goumenos D, Onoufriou A, Rosmaraki E, Margiolaki I, Georgiou CD. Methods on LDL particle isolation, characterization, and component fractionation for the development of novel specific oxidized LDL status markers for atherosclerotic disease risk assessment. Front Med (Lausanne) 2023; 9:1078492. [PMID: 36687450 PMCID: PMC9851470 DOI: 10.3389/fmed.2022.1078492] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Accepted: 12/05/2022] [Indexed: 01/06/2023] Open
Abstract
The present study uses simple, innovative methods to isolate, characterize and fractionate LDL in its main components for the study of specific oxidations on them that characterize oxidized low-density lipoprotein (oxLDL) status, as it causatively relates to atherosclerosis-associated cardiovascular disease (CVD) risk assessment. These methods are: (a) A simple, relatively time-short, low cost protocol for LDL isolation, to avoid shortcomings of the currently employed ultracentrifugation and affinity chromatography methodologies. (b) LDL purity verification by apoB100 SDS-PAGE analysis and by LDL particle size determination; the latter and its serum concentration are determined in the present study by a simple method more clinically feasible as marker of CVD risk assessment than nuclear magnetic resonance. (c) A protocol for LDL fractionation, for the first time, into its main protein/lipid components (apoB100, phospholipids, triglycerides, free cholesterol, and cholesteryl esters), as well as into LDL carotenoid/tocopherol content. (d) Protocols for the measurement, for the first time, of indicative specific LDL component oxidative modifications (cholesteryl ester-OOH, triglyceride-OOH, free cholesterol-OOH, phospholipid-OOH, apoB100-MDA, and apoB100-DiTyr) out of the many (known/unknown/under development) that collectively define oxLDL status, which contrasts with the current non-specific oxLDL status evaluation methods. The indicative oxLDL status markers, selected in the present study on the basis of expressing early oxidative stress-induced oxidative effects on LDL, are studied for the first time on patients with end stage kidney disease on maintenance hemodialysis, selected as an indicative model for atherosclerosis associated diseases. Isolating LDL and fractionating its protein and main lipid components, as well as its antioxidant arsenal comprised of carotenoids and tocopherols, paves the way for future studies to investigate all possible oxidative modifications responsible for turning LDL to oxLDL in association to their possible escaping from LDL's internal antioxidant defense. This can lead to studies to identify those oxidative modifications of oxLDL (after their artificial generation on LDL), which are recognized by macrophages and convert them to foam cells, known to be responsible for the formation of atherosclerotic plaques that lead to the various CVDs.
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Affiliation(s)
| | | | | | | | | | - Marios Papasotiriou
- Department of Nephrology, General University Hospital of Patras, Patras, Greece,Marios Papasotiriou,
| | | | - Dimitrios Goumenos
- Department of Nephrology, General University Hospital of Patras, Patras, Greece
| | - Anny Onoufriou
- Department of Microbiology, General University Hospital of Patras, University of Patras Medical School, Patras, Greece
| | | | | | - Christos D. Georgiou
- Department of Biology, University of Patras, Patras, Greece,*Correspondence: Christos D. Georgiou,
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3
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Anaganti N, Chattopadhyay A, Poirier JT, Hussain MM. Generation of hepatoma cell lines deficient in microsomal triglyceride transfer protein. J Lipid Res 2022; 63:100257. [PMID: 35931202 PMCID: PMC9405095 DOI: 10.1016/j.jlr.2022.100257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 07/03/2022] [Accepted: 07/08/2022] [Indexed: 01/05/2023] Open
Abstract
The microsomal triglyceride transfer protein (MTP) is essential for the secretion of apolipoprotein B (apoB)48- and apoB100-containing lipoproteins in the intestine and liver, respectively. Loss of function mutations in MTP cause abetalipoproteinemia. Heterologous cells are used to evaluate the function of MTP in apoB secretion to avoid background MTP activity in liver and intestine-derived cells. However, these systems are not suitable to study the role of MTP in the secretion of apoB100-containing lipoproteins, as expression of a large apoB100 peptide using plasmids is difficult. Here, we report a new cell culture model amenable for studying the role of different MTP mutations on apoB100 secretion. The endogenous MTTP gene was ablated in human hepatoma Huh-7 cells using single guide RNA and RNA-guided clustered regularly interspaced short palindromic repeats-associated sequence 9 ribonucleoprotein complexes. We successfully established three different clones that did not express any detectable MTTP mRNA or MTP protein or activity. These cells were defective in secreting apoB-containing lipoproteins and accumulated lipids. Furthermore, we show that transfection of these cells with plasmids expressing human MTTP cDNA resulted in the expression of MTP protein, restoration of triglyceride transfer activity, and secretion of apoB100. Thus, these new cells can be valuable tools for studying structure-function of MTP, roles of different missense mutations in various lipid transfer activities of MTP, and their ability to support apoB100 secretion, compensatory changes associated with loss of MTP, and in the identification of novel proteins that may require MTP for their synthesis and secretion.
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Affiliation(s)
- Narasimha Anaganti
- Department of Foundations of Medicine, NYU Long Island School of Medicine, Mineola, NY, USA
| | - Atrayee Chattopadhyay
- Department of Foundations of Medicine, NYU Long Island School of Medicine, Mineola, NY, USA
| | - John T Poirier
- Perlmutter Cancer Center, New York University Langone Health, New York, NY, USA
| | - M Mahmood Hussain
- Department of Foundations of Medicine, NYU Long Island School of Medicine, Mineola, NY, USA; VA New York Harbor Healthcare System, Brooklyn, NY, USA.
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4
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Wang B, Shen Y, Zhai L, Xia X, Gu HM, Wang M, Zhao Y, Chang X, Alabi A, Xing S, Deng S, Liu B, Wang G, Qin S, Zhang DW. Atherosclerosis-associated hepatic secretion of VLDL but not PCSK9 is dependent on cargo receptor protein Surf4. J Lipid Res 2021; 62:100091. [PMID: 34118252 PMCID: PMC8261665 DOI: 10.1016/j.jlr.2021.100091] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Revised: 05/11/2021] [Accepted: 06/01/2021] [Indexed: 02/05/2023] Open
Abstract
Plasma LDL is produced from catabolism of VLDL and cleared from circulation mainly via the hepatic LDL receptor (LDLR). Proprotein convertase subtilisin/kexin type 9 (PCSK9) promotes LDLR degradation, increasing plasma LDL-C levels. Circulating PCSK9 is mainly secreted by the liver, whereas VLDL is exclusively secreted by hepatocytes. However, the mechanism regulating their secretion is not completely understood. Surfeit 4 (Surf4) is a cargo receptor localized in the ER membrane. It recruits cargos into coat protein complex II vesicles to facilitate their secretion. Here, we investigated the role of Surf4 in VLDL and PCSK9 secretion. We generated Surf4 liver-specific knockout mice and found that knockout of Surf4 did not affect PCSK9 secretion, whereas it significantly reduced plasma levels of cholesterol, triglyceride, and lipid-binding protein apolipoprotein B (apoB). In cultured human hepatocytes, Surf4 coimmunoprecipitated and colocalized with apolipoprotein B100, and Surf4 silencing reduced secretion of apolipoprotein B100. Furthermore, knockdown of Surf4 in LDLR knockout (Ldlr−/−) mice significantly reduced triglyceride secretion, plasma levels of apoB and non-HDL-C, and the development of atherosclerosis. However, Surf4 liver-specific knockout mice and Surf4 knockdown in Ldlr−/− mice displayed similar levels of liver lipids and plasma alanine aminotransferase activity as control mice, indicating that inhibition of Surf4 does not cause notable liver damage. Expression of stearoyl-CoA desaturase-1 was also reduced in the liver of these mice, suggesting a reduction in de novo lipogenesis. In summary, hepatic deficiency of Surf4 reduced VLDL secretion and the development of atherosclerosis but did not cause significant hepatic lipid accumulation or liver damage.
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Affiliation(s)
- Bingxiang Wang
- Institute of Atherosclerosis and College of Basic Medical Sciences in Shandong First Medical University (Shandong Academy of Medical Sciences), Taian, China
| | - Yishi Shen
- Department of Pediatrics and Group on the Molecular and Cell Biology of Lipids, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Lei Zhai
- Institute of Atherosclerosis and College of Basic Medical Sciences in Shandong First Medical University (Shandong Academy of Medical Sciences), Taian, China
| | - Xiaodan Xia
- Department of Orthopedics, The Sixth Affiliated Hospital of Guangzhou Medical University, Qingyuan People's Hospital, Qingyuan, China
| | - Hong-Mei Gu
- Department of Pediatrics and Group on the Molecular and Cell Biology of Lipids, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Maggie Wang
- Department of Pediatrics and Group on the Molecular and Cell Biology of Lipids, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Yongfang Zhao
- Institute of Atherosclerosis and College of Basic Medical Sciences in Shandong First Medical University (Shandong Academy of Medical Sciences), Taian, China
| | - Xiaole Chang
- Institute of Atherosclerosis and College of Basic Medical Sciences in Shandong First Medical University (Shandong Academy of Medical Sciences), Taian, China
| | - Adekunle Alabi
- Department of Pediatrics and Group on the Molecular and Cell Biology of Lipids, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Sijie Xing
- Department of Pediatrics and Group on the Molecular and Cell Biology of Lipids, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Shijun Deng
- Department of Pediatrics and Group on the Molecular and Cell Biology of Lipids, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Boyan Liu
- Institute of Atherosclerosis and College of Basic Medical Sciences in Shandong First Medical University (Shandong Academy of Medical Sciences), Taian, China
| | - Guiqing Wang
- Department of Orthopedics, The Sixth Affiliated Hospital of Guangzhou Medical University, Qingyuan People's Hospital, Qingyuan, China
| | - Shucun Qin
- Institute of Atherosclerosis and College of Basic Medical Sciences in Shandong First Medical University (Shandong Academy of Medical Sciences), Taian, China.
| | - Da-Wei Zhang
- Department of Pediatrics and Group on the Molecular and Cell Biology of Lipids, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.
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5
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Takahashi M, Ozaki N, Nagashima S, Wakabayashi T, Iwamoto S, Ishibashi S. Normal plasma apoB48 despite the virtual absence of apoB100 in a compound heterozygote with novel mutations in the MTTP gene. J Clin Lipidol 2021; 15:569-573. [PMID: 34052173 DOI: 10.1016/j.jacl.2021.04.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Revised: 04/23/2021] [Accepted: 04/28/2021] [Indexed: 11/27/2022]
Abstract
"Normotriglyceridemic abetalipoproteinemia (ABL)" was originally described as a clinical entity distinct from either ABL or hypobetalipoproteinemia. Subsequent studies identified mutations in APOB gene which encoded truncated apoB longer than apoB48. Therefore, "Normotriglyceridemic ABL" can be a subtype of homozygous familial hypobetalipoproteinemia 1. Here, we report an atypical female case of ABL who was initially diagnosed with "normotriglyceridemic ABL", because she had normal plasma apoB48 despite the virtual absence of apoB100 and low plasma TG level. Next generation sequencing revealed that she was a compound heterozygote of two novel MTTP mutations: nonsense (p.Q272X) and missense (p.G709R). We speculate that p.G709R might confer residual triglyceride transfer activity of MTTP preferentially in the intestinal epithelium to the hepatocytes, allowing production of apoB48. Together, "normotriglyceridemic ABL" may be a heterogenous disorder which is caused by specific mutations in either APOB or MTTP gene.
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Affiliation(s)
- Manabu Takahashi
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Jichi Medical University, Shimotsuke, Tochigi 329-0498, Japan.
| | - Nobuaki Ozaki
- Division of Endocrinology, Japanese Red Cross Nagoya Daiichi Hospital, Nagoya 453-8511, Japan
| | - Shuichi Nagashima
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Jichi Medical University, Shimotsuke, Tochigi 329-0498, Japan
| | - Tetsuji Wakabayashi
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Jichi Medical University, Shimotsuke, Tochigi 329-0498, Japan
| | - Sadahiko Iwamoto
- Division of Human Genetics, Center for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi 329-0498, Japan
| | - Shun Ishibashi
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Jichi Medical University, Shimotsuke, Tochigi 329-0498, Japan.
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6
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Björnson E, Packard CJ, Adiels M, Andersson L, Matikainen N, Söderlund S, Kahri J, Hakkarainen A, Lundbom N, Lundbom J, Sihlbom C, Thorsell A, Zhou H, Taskinen MR, Borén J. Apolipoprotein B48 metabolism in chylomicrons and very low-density lipoproteins and its role in triglyceride transport in normo- and hypertriglyceridemic human subjects. J Intern Med 2020; 288:422-438. [PMID: 31846520 DOI: 10.1111/joim.13017] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND Renewed interest in triglyceride-rich lipoproteins as causative agents in cardiovascular disease mandates further exploration of the integrated metabolism of chylomicrons and very low-density lipoproteins (VLDL). METHODS Novel tracer techniques and an integrated multi-compartmental model were used to determine the kinetics of apoB48- and apoB100-containing particles in the chylomicron and VLDL density intervals in 15 subjects with a wide range of plasma triglyceride levels. RESULTS Following a fat-rich meal, apoB48 appeared in the chylomicron, VLDL1 and VLDL2 fractions in all subjects. Chylomicrons cleared rapidly from the circulation but apoB48-containing VLDL accumulated, and over the day were 3-fold higher in those with high versus low plasma triglyceride. ApoB48-containing particles were secreted directly into both the chylomicron and VLDL fractions at rates that were similar across the plasma triglyceride range studied. During fat absorption, whilst most triglyceride entered the circulation in chylomicrons, the majority of apoB48 particles were secreted into the VLDL density range. CONCLUSION The intestine secretes apoB48-containing particles not only as chylomicrons but also directly into the VLDL1 and VLDL2 density ranges both in the basal state and during dietary lipid absorption. Over the day, apoB48-containing particles appear to comprise about 20-25% of circulating VLDL and, especially in those with elevated triglycerides, form part of a slowly cleared 'remnant' particle population, thereby potentially increasing CHD risk. These findings provide a metabolic understanding of the potential consequences for increased CHD risk when slowed lipolysis leads to the accumulation of remnants, especially in individuals with hypertriglyceridemia.
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Affiliation(s)
- E Björnson
- Department of Molecular and Clinical Medicine, University of Gothenburg, Gothenburg, Sweden
| | - C J Packard
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UK
| | - M Adiels
- Department of Molecular and Clinical Medicine, University of Gothenburg, Gothenburg, Sweden
| | - L Andersson
- Department of Molecular and Clinical Medicine, University of Gothenburg, Gothenburg, Sweden
| | - N Matikainen
- Research Programs Unit, Clinical and Molecular Metabolism, University of Helsinki, Helsinki, Finland.,Endocrinology, Abdominal Center, Helsinki University Hospital, Helsinki, Finland
| | - S Söderlund
- Research Programs Unit, Clinical and Molecular Metabolism, University of Helsinki, Helsinki, Finland.,Endocrinology, Abdominal Center, Helsinki University Hospital, Helsinki, Finland
| | - J Kahri
- Department of Internal Medicine and Rehabilitation, Helsinki University Hospital, Helsinki, Finland
| | - A Hakkarainen
- Radiology, HUS Medical Imaging Center, Helsinki University Hospital, University of Helsinki, Helsinki, Finland.,Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, Espoo, Finland
| | - N Lundbom
- Radiology, HUS Medical Imaging Center, Helsinki University Hospital, University of Helsinki, Helsinki, Finland
| | - J Lundbom
- Radiology, HUS Medical Imaging Center, Helsinki University Hospital, University of Helsinki, Helsinki, Finland
| | - C Sihlbom
- Proteomics Facility, University of Gothenburg, Gothenburg, Sweden
| | - A Thorsell
- Proteomics Facility, University of Gothenburg, Gothenburg, Sweden
| | - H Zhou
- Merck Research Laboratories, Merck & Co. Inc., Kenilworth, NJ, USA
| | - M-R Taskinen
- Research Programs Unit, Clinical and Molecular Metabolism, University of Helsinki, Helsinki, Finland
| | - J Borén
- Department of Molecular and Clinical Medicine, University of Gothenburg, Gothenburg, Sweden.,Sahlgrenska University Hospital, Gothenburg, Sweden
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7
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Zhang J, Jazii FR, Haghighi MM, Alvares D, Liu L, Khosraviani N, Adeli K. miR-130b is a potent stimulator of hepatic very-low-density lipoprotein assembly and secretion via marked induction of microsomal triglyceride transfer protein. Am J Physiol Endocrinol Metab 2020; 318:E262-E275. [PMID: 31821038 DOI: 10.1152/ajpendo.00276.2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
miR-130b is a microRNA whose expression is particularly elevated within adipose tissue and in the circulation in diabetic states. Hepatic miR-130b expression has been linked to hepatocellular carcinoma and changes in lipid metabolism. Here, we investigated the role of miR-130b in hepatic lipid homeostasis and lipoprotein export. We observed that overexpression of miR-130b-3p or -5p in HepG2 cells markedly enhanced the secretion of very-low-density lipoprotein (VLDL) particles, enhanced the secretion of [3H]glycerol metabolically labeled triglyceride (TG), and significantly increased the number or the average size of lipid droplets (LDs), respectively. Overexpression of miR-130b also altered the expression of key genes involved in lipid metabolism and in particular markedly increased both mRNA and protein expression levels of microsomal triglyceride transfer protein (MTP). Conversely, the miR-130b inhibitor decreased mRNA levels of MTP and fatty acid synthase (FAS) in HepG2 cells. However, dual-luciferase reporter assays indicated that MTP is not a direct target of miR-130b-3p. miR-130b overexpression did not alter de novo synthesized TG or the stability and secretion of apolipoprotein B 100. Interestingly, knockdown of phosphatase and tensin homolog (PTEN) blocked the upregulation of MTP mRNA induced by miR-130b. Finally, miR-130b-induced stimulation of VLDL secretion was also observed in a second hepatocyte cell culture model, immortalized human hepatocytes, confirming the effects observed in HepG2 cells. Overall, these data suggest a potential role for miR-130b in promoting hepatic VLDL assembly and secretion mediated by marked stimulation of MTP expression and TG mobilization. Thus miR-130b overexpression corrects the defect in VLDL production in HepG2 cells.
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Affiliation(s)
- Jing Zhang
- Molecular Medicine, Research Institute, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
| | - Ferdous Rastgar Jazii
- Molecular Medicine, Research Institute, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
| | - Mahdi Montazer Haghighi
- Molecular Medicine, Research Institute, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
| | - Danielle Alvares
- Molecular Medicine, Research Institute, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
| | - Lipei Liu
- Molecular Medicine, Research Institute, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
| | - Negar Khosraviani
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
| | - Khosrow Adeli
- Molecular Medicine, Research Institute, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
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8
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Nakajima K, Tokita Y, Tanaka A. Hypothesis II: The majority of VLDL-apoB48 remnants in postprandial plasma are derived from the liver, not from the intestine. Clin Chim Acta 2019; 490:12-6. [PMID: 30553860 DOI: 10.1016/j.cca.2018.12.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Revised: 12/10/2018] [Accepted: 12/10/2018] [Indexed: 11/21/2022]
Abstract
We have long thought that remnant lipoproteins (RLP) in the postprandial plasma contain CM remnants (exogenous remnants; RLP-apoB48) and VLDL remnants (endogenous remnants; RLP-apoB100) of different origin, i.e. produced in the intestine and liver, respectively. However, the majority of CM remnants incorporated into liver from the circulation are degraded in liver and may be reused for the remodeling of VLDL. Namely, the most of the apoB48 in CM remnants are smoothly incorporated into the liver after fat intake along with lipids and other apolipoproteins via the LDL receptor and LDL-receptor-related protein (LRP). Subsequently, apoB48 may be reconstituted in VLDL as VLDL apoB48 through an essential physiological pathway similar or the same to that of VLDL apoB100 formation in the liver and secreted into the circulation as VLDL apoB48 to form their remnants. Because those particles are newly reconstituted in liver as a portion of VLDL, we propose that both RLP-apoB100 and RLP-apoB48 are endogenous VLDL remnants produced in liver after fat intake. Also we predict the presence of a new pathway for the formation of VLDL apoB48 along with VLDL apoB100 in liver in humans similar in mice and rats.
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9
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Vikøren LA, Drotningsvik A, Mjøs SA, Mellgren G, Gudbrandsen OA. Salmon Fillet Intake Led to Higher Serum Triacylglycerol in Obese Zucker Fa/Fa Rats But Not in Normolipidemic Long-Evans Rats. Nutrients 2018; 10:E1459. [PMID: 30297656 DOI: 10.3390/nu10101459] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Revised: 09/20/2018] [Accepted: 10/01/2018] [Indexed: 12/02/2022] Open
Abstract
The triacylglycerol lowering effect of fatty fish and fish oils is well recognized, however we recently showed that salmon intake resulted in higher serum triacylglycerol concentration in obese Zucker fa/fa rats. Since effects of salmon fillet have never before been studied in rats, the objective of this study was to compare effects of salmon intake on serum lipids in hyperlipidemic obese rats with normolipidemic lean rats. Zucker fa/fa rats and Long-Evans rats were fed diets with 25% protein from baked salmon fillet and 75% protein from casein, or casein as sole protein source (control group) for four weeks. Serum triacylglycerol concentration was higher, and cholesterol and apolipoproteinB-100 concentrations were lower in Zucker fa/fa rats fed Baked Salmon Diet compared to Zucker fa/fa rats fed Control Diet, with no differences in serum triacylglycerol, cholesterol and apolipoproteinB-100 between Long-Evans rats fed Baked Salmon Diet or Control Diet. Serum triacylglycerol fatty acid composition showed greater similarities to dietary fatty acids in Zucker fa/fa rats than in Long-Evans rats. To conclude, intake of baked salmon fillet resulted in higher serum triacylglycerol concentration and lower serum cholesterol concentration in hyperlipidemic obese Zucker fa/fa rats but did not affect serum lipids in normolipidemic lean Long-Evans rats.
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10
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Amengual J, Guo L, Strong A, Madrigal-Matute J, Wang H, Kaushik S, Brodsky JL, Rader DJ, Cuervo AM, Fisher EA. Autophagy Is Required for Sortilin-Mediated Degradation of Apolipoprotein B100. Circ Res 2018; 122:568-582. [PMID: 29301854 DOI: 10.1161/circresaha.117.311240] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/01/2017] [Revised: 12/28/2017] [Accepted: 12/29/2017] [Indexed: 12/30/2022]
Abstract
RATIONALE Genome-wide association studies identified single-nucleotide polymorphisms near the SORT1 locus strongly associated with decreased plasma LDL-C (low-density lipoprotein cholesterol) levels and protection from atherosclerotic cardiovascular disease and myocardial infarction. The minor allele of the causal SORT1 single-nucleotide polymorphism locus creates a putative C/EBPα (CCAAT/enhancer-binding protein α)-binding site in the SORT1 promoter, thereby increasing in homozygotes sortilin expression by 12-fold in liver, which is rich in this transcription factor. Our previous studies in mice have showed reductions in plasma LDL-C and its principal protein component, apoB (apolipoprotein B) with increased SORT1 expression, and in vitro studies suggested that sortilin promoted the presecretory lysosomal degradation of apoB associated with the LDL precursor, VLDL (very-low-density lipoprotein). OBJECTIVE To determine directly that SORT1 overexpression results in apoB degradation and to identify the mechanisms by which this reduces apoB and VLDL secretion by the liver, thereby contributing to understanding the clinical phenotype of lower LDL-C levels. METHODS AND RESULTS Pulse-chase studies directly established that SORT1 overexpression results in apoB degradation. As noted above, previous work implicated a role for lysosomes in this degradation. Through in vitro and in vivo studies, we now demonstrate that the sortilin-mediated route of apoB to lysosomes is unconventional and intersects with autophagy. Increased expression of sortilin diverts more apoB away from secretion, with both proteins trafficking to the endosomal compartment in vesicles that fuse with autophagosomes to form amphisomes. The amphisomes then merge with lysosomes. Furthermore, we show that sortilin itself is a regulator of autophagy and that its activity is scaled to the level of apoB synthesis. CONCLUSIONS These results strongly suggest that an unconventional lysosomal targeting process dependent on autophagy degrades apoB that was diverted from the secretory pathway by sortilin and provides a mechanism contributing to the reduced LDL-C found in individuals with SORT1 overexpression.
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Affiliation(s)
- Jaume Amengual
- From the Division of Cardiology (J.A., L.G., H.W., E.A.F.), Department of Medicine (J.A., L.G., H.W., E.A.F.), and Marc and Ruti Bell Program in Vascular Biology (J.A., E.A.F., L.G, H.W.), NYU School of Medicine; Institute for Translational Medicine and Therapeutics, Cardiovascular Institute, and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia (A.S., D.J.R.); Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York (J.M.-M., S.K., A.M.C.); and Department of Biological Sciences, University of Pittsburgh, PA (J.L.B.)
| | - Liang Guo
- From the Division of Cardiology (J.A., L.G., H.W., E.A.F.), Department of Medicine (J.A., L.G., H.W., E.A.F.), and Marc and Ruti Bell Program in Vascular Biology (J.A., E.A.F., L.G, H.W.), NYU School of Medicine; Institute for Translational Medicine and Therapeutics, Cardiovascular Institute, and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia (A.S., D.J.R.); Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York (J.M.-M., S.K., A.M.C.); and Department of Biological Sciences, University of Pittsburgh, PA (J.L.B.)
| | - Alanna Strong
- From the Division of Cardiology (J.A., L.G., H.W., E.A.F.), Department of Medicine (J.A., L.G., H.W., E.A.F.), and Marc and Ruti Bell Program in Vascular Biology (J.A., E.A.F., L.G, H.W.), NYU School of Medicine; Institute for Translational Medicine and Therapeutics, Cardiovascular Institute, and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia (A.S., D.J.R.); Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York (J.M.-M., S.K., A.M.C.); and Department of Biological Sciences, University of Pittsburgh, PA (J.L.B.)
| | - Julio Madrigal-Matute
- From the Division of Cardiology (J.A., L.G., H.W., E.A.F.), Department of Medicine (J.A., L.G., H.W., E.A.F.), and Marc and Ruti Bell Program in Vascular Biology (J.A., E.A.F., L.G, H.W.), NYU School of Medicine; Institute for Translational Medicine and Therapeutics, Cardiovascular Institute, and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia (A.S., D.J.R.); Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York (J.M.-M., S.K., A.M.C.); and Department of Biological Sciences, University of Pittsburgh, PA (J.L.B.)
| | - Haizhen Wang
- From the Division of Cardiology (J.A., L.G., H.W., E.A.F.), Department of Medicine (J.A., L.G., H.W., E.A.F.), and Marc and Ruti Bell Program in Vascular Biology (J.A., E.A.F., L.G, H.W.), NYU School of Medicine; Institute for Translational Medicine and Therapeutics, Cardiovascular Institute, and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia (A.S., D.J.R.); Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York (J.M.-M., S.K., A.M.C.); and Department of Biological Sciences, University of Pittsburgh, PA (J.L.B.)
| | - Susmita Kaushik
- From the Division of Cardiology (J.A., L.G., H.W., E.A.F.), Department of Medicine (J.A., L.G., H.W., E.A.F.), and Marc and Ruti Bell Program in Vascular Biology (J.A., E.A.F., L.G, H.W.), NYU School of Medicine; Institute for Translational Medicine and Therapeutics, Cardiovascular Institute, and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia (A.S., D.J.R.); Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York (J.M.-M., S.K., A.M.C.); and Department of Biological Sciences, University of Pittsburgh, PA (J.L.B.)
| | - Jeffrey L Brodsky
- From the Division of Cardiology (J.A., L.G., H.W., E.A.F.), Department of Medicine (J.A., L.G., H.W., E.A.F.), and Marc and Ruti Bell Program in Vascular Biology (J.A., E.A.F., L.G, H.W.), NYU School of Medicine; Institute for Translational Medicine and Therapeutics, Cardiovascular Institute, and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia (A.S., D.J.R.); Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York (J.M.-M., S.K., A.M.C.); and Department of Biological Sciences, University of Pittsburgh, PA (J.L.B.)
| | - Daniel J Rader
- From the Division of Cardiology (J.A., L.G., H.W., E.A.F.), Department of Medicine (J.A., L.G., H.W., E.A.F.), and Marc and Ruti Bell Program in Vascular Biology (J.A., E.A.F., L.G, H.W.), NYU School of Medicine; Institute for Translational Medicine and Therapeutics, Cardiovascular Institute, and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia (A.S., D.J.R.); Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York (J.M.-M., S.K., A.M.C.); and Department of Biological Sciences, University of Pittsburgh, PA (J.L.B.)
| | - Ana Maria Cuervo
- From the Division of Cardiology (J.A., L.G., H.W., E.A.F.), Department of Medicine (J.A., L.G., H.W., E.A.F.), and Marc and Ruti Bell Program in Vascular Biology (J.A., E.A.F., L.G, H.W.), NYU School of Medicine; Institute for Translational Medicine and Therapeutics, Cardiovascular Institute, and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia (A.S., D.J.R.); Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York (J.M.-M., S.K., A.M.C.); and Department of Biological Sciences, University of Pittsburgh, PA (J.L.B.)
| | - Edward A Fisher
- From the Division of Cardiology (J.A., L.G., H.W., E.A.F.), Department of Medicine (J.A., L.G., H.W., E.A.F.), and Marc and Ruti Bell Program in Vascular Biology (J.A., E.A.F., L.G, H.W.), NYU School of Medicine; Institute for Translational Medicine and Therapeutics, Cardiovascular Institute, and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia (A.S., D.J.R.); Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York (J.M.-M., S.K., A.M.C.); and Department of Biological Sciences, University of Pittsburgh, PA (J.L.B.).
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11
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Fabbrini E, Luecking CT, Love-Gregory L, Okunade AL, Yoshino M, Fraterrigo G, Patterson BW, Klein S. Physiological Mechanisms of Weight Gain-Induced Steatosis in People With Obesity. Gastroenterology 2016; 150:79-81.e2. [PMID: 26376348 PMCID: PMC4691551 DOI: 10.1053/j.gastro.2015.09.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Revised: 07/15/2015] [Accepted: 09/03/2015] [Indexed: 02/06/2023]
Abstract
Weight gain is associated with an increase in intrahepatic triglycerides (IHTGs), and is the primary cause of nonalcoholic fatty liver disease in obese individuals. We combined imaging and stable isotope tracer techniques to evaluate the physiologic mechanisms of weight gain-induced steatosis in 27 obese people. Weight gain appeared to increase IHTG content by generating an imbalance between hepatic fatty acid availability and disposal, and resulted in increased hepatic de novo lipogenesis, decreased intrahepatic fatty acid oxidation, and inadequate increases in IHTG export via very low-density lipoprotein secretion. ClinicalTrials.gov ID NCT01184170.
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Affiliation(s)
| | | | | | | | | | | | | | - Samuel Klein
- Center for Human Nutrition and Atkins Center of Excellence in Obesity Medicine, Washington University School of Medicine, St Louis, Missouri.
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