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Diaz-Vegas A, Cooke KC, Cutler HB, Yau B, Masson SWC, Harney D, Fuller OK, Potter M, Madsen S, Craw NR, Zhang Y, Moreno CL, Kebede MA, Neely GG, Stöckli J, Burchfield JG, James DE. Deletion of miPEP in adipocytes protects against obesity and insulin resistance by boosting muscle metabolism. Mol Metab 2024; 86:101983. [PMID: 38960128 DOI: 10.1016/j.molmet.2024.101983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2024] [Revised: 06/24/2024] [Accepted: 06/27/2024] [Indexed: 07/05/2024] Open
Abstract
Mitochondria facilitate thousands of biochemical reactions, covering a broad spectrum of anabolic and catabolic processes. Here we demonstrate that the adipocyte mitochondrial proteome is markedly altered across multiple models of insulin resistance and reveal a consistent decrease in the level of the mitochondrial processing peptidase miPEP. OBJECTIVE To determine the role of miPEP in insulin resistance. METHODS To experimentally test this observation, we generated adipocyte-specific miPEP knockout mice to interrogate its role in the aetiology of insulin resistance. RESULTS We observed a strong phenotype characterised by enhanced insulin sensitivity and reduced adiposity, despite normal food intake and physical activity. Strikingly, these phenotypes vanished when mice were housed at thermoneutrality, suggesting that metabolic protection conferred by miPEP deletion hinges upon a thermoregulatory process. Tissue specific analysis of miPEP deficient mice revealed an increment in muscle metabolism, and upregulation of the protein FBP2 that is involved in ATP hydrolysis in the gluconeogenic pathway. CONCLUSION These findings suggest that miPEP deletion initiates a compensatory increase in skeletal muscle metabolism acting as a protective mechanism against diet-induced obesity and insulin resistance.
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Affiliation(s)
- Alexis Diaz-Vegas
- School of Life and Environmental Sciences, University of Sydney, Camperdown, New South Wales, Australia; Charles Perkins Centre, University of Sydney, Camperdown, New South Wales, Australia.
| | - Kristen C Cooke
- School of Life and Environmental Sciences, University of Sydney, Camperdown, New South Wales, Australia; Charles Perkins Centre, University of Sydney, Camperdown, New South Wales, Australia
| | - Harry B Cutler
- School of Life and Environmental Sciences, University of Sydney, Camperdown, New South Wales, Australia; Charles Perkins Centre, University of Sydney, Camperdown, New South Wales, Australia
| | - Belinda Yau
- School of Medical Sciences, University of Sydney, Camperdown, New South Wales, Australia
| | - Stewart W C Masson
- School of Life and Environmental Sciences, University of Sydney, Camperdown, New South Wales, Australia; Charles Perkins Centre, University of Sydney, Camperdown, New South Wales, Australia
| | - Dylan Harney
- School of Life and Environmental Sciences, University of Sydney, Camperdown, New South Wales, Australia; Charles Perkins Centre, University of Sydney, Camperdown, New South Wales, Australia
| | - Oliver K Fuller
- School of Life and Environmental Sciences, University of Sydney, Camperdown, New South Wales, Australia; Charles Perkins Centre, University of Sydney, Camperdown, New South Wales, Australia
| | - Meg Potter
- School of Life and Environmental Sciences, University of Sydney, Camperdown, New South Wales, Australia; Charles Perkins Centre, University of Sydney, Camperdown, New South Wales, Australia
| | - Søren Madsen
- School of Life and Environmental Sciences, University of Sydney, Camperdown, New South Wales, Australia; Charles Perkins Centre, University of Sydney, Camperdown, New South Wales, Australia
| | - Niamh R Craw
- School of Life and Environmental Sciences, University of Sydney, Camperdown, New South Wales, Australia; Charles Perkins Centre, University of Sydney, Camperdown, New South Wales, Australia
| | - Yiju Zhang
- School of Life and Environmental Sciences, University of Sydney, Camperdown, New South Wales, Australia; Charles Perkins Centre, University of Sydney, Camperdown, New South Wales, Australia
| | - Cesar L Moreno
- School of Life and Environmental Sciences, University of Sydney, Camperdown, New South Wales, Australia; Charles Perkins Centre, University of Sydney, Camperdown, New South Wales, Australia
| | - Melkam A Kebede
- School of Medical Sciences, University of Sydney, Camperdown, New South Wales, Australia
| | - G Gregory Neely
- School of Life and Environmental Sciences, University of Sydney, Camperdown, New South Wales, Australia; Charles Perkins Centre, University of Sydney, Camperdown, New South Wales, Australia
| | - Jacqueline Stöckli
- School of Life and Environmental Sciences, University of Sydney, Camperdown, New South Wales, Australia; Charles Perkins Centre, University of Sydney, Camperdown, New South Wales, Australia
| | - James G Burchfield
- School of Life and Environmental Sciences, University of Sydney, Camperdown, New South Wales, Australia; Charles Perkins Centre, University of Sydney, Camperdown, New South Wales, Australia
| | - David E James
- School of Life and Environmental Sciences, University of Sydney, Camperdown, New South Wales, Australia; Charles Perkins Centre, University of Sydney, Camperdown, New South Wales, Australia; School of Medical Sciences, University of Sydney, Camperdown, New South Wales, Australia.
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2
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Xiong X, Yang C, Jin Y, Zhang R, Wang S, Gan L, Hou S, Bao Y, Zeng Z, Ye Y, Gao Z. ABHD6 suppresses colorectal cancer progression via AKT signaling pathway. Mol Carcinog 2024; 63:647-662. [PMID: 38197491 DOI: 10.1002/mc.23678] [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] [Received: 07/19/2023] [Revised: 12/05/2023] [Accepted: 12/28/2023] [Indexed: 01/11/2024]
Abstract
Colorectal cancer (CRC) continues to be a prevalent malignancy, posing a significant risk to human health. The involvement of alpha/beta hydrolase domain 6 (ABHD6), a serine hydrolase family member, in CRC development was suggested by our analysis of clinical data. However, the role of ABHD6 in CRC remains unclear. This study seeks to elucidate the clinical relevance, biological function, and potential molecular mechanisms of ABHD6 in CRC. We investigated the role of ABHD6 in clinical settings, conducting proliferation, migration, and cell cycle assays. To determine the influence of ABHD6 expression levels on Oxaliplatin sensitivity, we also performed apoptosis assays. RNA sequencing and KEGG analysis were utilized to uncover the potential molecular mechanisms of ABHD6. Furthermore, we validated its expression levels using Western blot and reactive oxygen species (ROS) detection assays. Our results demonstrated that ABHD6 expression in CRC tissues was notably lower compared to adjacent normal tissues. This low expression correlated with a poorer prognosis for CRC patients. Moreover, ABHD6 overexpression impeded CRC cell proliferation and migration while inducing G0/G1 cell cycle arrest. In vivo experiments revealed that downregulation of ABHD6 resulted in an increase in tumor weight and volume. Mechanistically, ABHD6 overexpression inhibited the activation of the AKT signaling pathway and decreased ROS levels in CRC cells, suggesting the role of ABHD6 in CRC progression via the AKT signaling pathway. Our findings demonstrate that ABHD6 functions as a tumor suppressor, primarily by inhibiting the AKT signaling pathway. This role establishes ABHD6 as a promising prognostic biomarker and a potential therapeutic target for CRC patients.
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Affiliation(s)
- Xiaoyu Xiong
- Department of Gastroenterological Surgery, Peking University People's Hospital, Beijing, China
| | - Changjiang Yang
- Department of Gastroenterological Surgery, Peking University People's Hospital, Beijing, China
| | - Yiteng Jin
- Center for Quantitative Biology, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
| | - Rui Zhang
- Center for Quantitative Biology, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
| | - Shuo Wang
- Department of Gastroenterological Surgery, Peking University People's Hospital, Beijing, China
| | - Lin Gan
- Department of Gastroenterological Surgery, Peking University People's Hospital, Beijing, China
| | - Sen Hou
- Department of Gastroenterological Surgery, Peking University People's Hospital, Beijing, China
| | - Yudi Bao
- Department of Gastroenterological Surgery, Peking University People's Hospital, Beijing, China
| | - Zexian Zeng
- Center for Quantitative Biology, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
| | - Yingjiang Ye
- Department of Gastroenterological Surgery, Peking University People's Hospital, Beijing, China
| | - Zhidong Gao
- Department of Gastroenterological Surgery, Peking University People's Hospital, Beijing, China
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3
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Lee E, Korf H, Vidal-Puig A. Reply to: "Liver-adipose tissue crosstalk in nonalcoholic fatty liver disease: the emerging role of remnant cholesterol": "BAT activation might improve NAFLD in patients, but this might require developing and/or maintaining functionally relevant levels of BAT mass.". J Hepatol 2024; 80:e112-e114. [PMID: 37898347 DOI: 10.1016/j.jhep.2023.10.027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2023] [Accepted: 10/23/2023] [Indexed: 10/30/2023]
Affiliation(s)
- Eunyoung Lee
- Metabolic Research Laboratories, Wellcome Trust MRC Institute of Metabolic Science, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK; Department of Medical Physiology, Graduate School of Medicine; Research Institute of Disaster Medicine, Chiba University, Chiba, Japan
| | - Hannelie Korf
- Laboratory of Hepatology, CHROMETA Department, KU Leuven, Leuven, Belgium.
| | - Antonio Vidal-Puig
- Metabolic Research Laboratories, Wellcome Trust MRC Institute of Metabolic Science, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK; Centro de Investigacion Principe Felipe, Valencia, Spain; Cambridge University Nanjing Centre of Technology and Innovation, Nanjing, China.
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4
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Rao G, Peng X, Li X, An K, He H, Fu X, Li S, An Z. Unmasking the enigma of lipid metabolism in metabolic dysfunction-associated steatotic liver disease: from mechanism to the clinic. Front Med (Lausanne) 2023; 10:1294267. [PMID: 38089874 PMCID: PMC10711211 DOI: 10.3389/fmed.2023.1294267] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Accepted: 10/26/2023] [Indexed: 06/21/2024] Open
Abstract
Metabolic dysfunction-associated steatotic liver disease (MASLD), formerly defined as non-alcoholic fatty liver disease (NAFLD), is a disorder marked by the excessive deposition of lipids in the liver, giving rise to a spectrum of liver pathologies encompassing steatohepatitis, fibrosis/cirrhosis, and hepatocellular carcinoma. Despite the alarming increase in its prevalence, the US Food and Drug Administration has yet to approve effective pharmacological therapeutics for clinical use. MASLD is characterized by the accretion of lipids within the hepatic system, arising from a disarray in lipid provision (whether through the absorption of circulating lipids or de novo lipogenesis) and lipid elimination (via free fatty acid oxidation or the secretion of triglyceride-rich lipoproteins). This disarray leads to the accumulation of lipotoxic substances, cellular pressure, damage, and fibrosis. Indeed, the regulation of the lipid metabolism pathway is intricate and multifaceted, involving a myriad of factors, such as membrane transport proteins, metabolic enzymes, and transcription factors. Here, we will review the existing literature on the key process of lipid metabolism in MASLD to understand the latest progress in this molecular mechanism. Notably, de novo lipogenesis and the roles of its two main transcription factors and other key metabolic enzymes are highlighted. Furthermore, we will delve into the realm of drug research, examining the recent progress made in understanding lipid metabolism in MASLD. Additionally, we will outline prospective avenues for future drug research on MASLD based on our unique perspectives.
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Affiliation(s)
- Guocheng Rao
- Department of Endocrinology and Metabolism, West China Hospital, Sichuan University, Chengdu, China
| | - Xi Peng
- Department of Endocrinology and Metabolism, West China Hospital, Sichuan University, Chengdu, China
- Department of Endocrinology and Metabolism, Affiliated Hospital of North Sichuan Medical College, North Sichuan Medical College, Nanchong, China
| | - Xinqiong Li
- State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University and Collaborative Innovation Center of Biotherapy, Chengdu, China
| | - Kang An
- General Practice Ward/International Medical Center Ward, General Practice Medical Center, National Clinical Research Center for Geriatrics, Multimorbidity Laboratory, West China Hospital, Sichuan University, Chengdu, China
| | - He He
- Department of Laboratory Medicine, West China Hospital, Sichuan University, Chengdu, China
| | - Xianghui Fu
- State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University and Collaborative Innovation Center of Biotherapy, Chengdu, China
| | - Shuangqing Li
- General Practice Ward/International Medical Center Ward, General Practice Medical Center, National Clinical Research Center for Geriatrics, Multimorbidity Laboratory, West China Hospital, Sichuan University, Chengdu, China
| | - Zhenmei An
- Department of Endocrinology and Metabolism, West China Hospital, Sichuan University, Chengdu, China
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5
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Gabbia D, De Martin S. Targeting the Adipose Tissue-Liver-Gut Microbiota Crosstalk to Cure MASLD. BIOLOGY 2023; 12:1471. [PMID: 38132297 PMCID: PMC10741127 DOI: 10.3390/biology12121471] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 11/23/2023] [Accepted: 11/24/2023] [Indexed: 12/23/2023]
Abstract
The gut microbiota is a complex system, playing a peculiar role in regulating innate and systemic immunity. Increasing evidence links dysfunctional gut microbiota to metabolic dysfunction-associated steatotic liver disease (MASLD) due to the activation of multiple pathways in the gut and in the liver, including those mediated by Toll-like receptors (TLRs), that sustain hepatic inflammation. Thus, many efforts have been made to unravel the role of microbiota-associated dysfunction in MASLD, with the final aim of finding novel strategies to improve liver steatosis and function. Moreover, recent evidence underlines the role of adipose tissue in sustaining hepatic inflammation during MASLD development. In this review, we focus on the recently discovered strategies proposed to improve the alteration of gut microbiota observed in MASLD patients, with a particular insight into those known to modulate gut microbiota-associated dysfunction and to affect the complex crosstalk between the gut, the adipose tissue, and the liver.
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Affiliation(s)
- Daniela Gabbia
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, 351131 Padova, Italy;
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6
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Guilherme A, Rowland LA, Wang H, Czech MP. The adipocyte supersystem of insulin and cAMP signaling. Trends Cell Biol 2023; 33:340-354. [PMID: 35989245 PMCID: PMC10339226 DOI: 10.1016/j.tcb.2022.07.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Revised: 07/27/2022] [Accepted: 07/28/2022] [Indexed: 01/28/2023]
Abstract
Adipose tissue signals to brain, liver, and muscles to control whole body metabolism through secreted lipid and protein factors as well as neurotransmission, but the mechanisms involved are incompletely understood. Adipocytes sequester triglyceride (TG) in fed conditions stimulated by insulin, while in fasting catecholamines trigger TG hydrolysis, releasing glycerol and fatty acids (FAs). These antagonistic hormone actions result in part from insulin's ability to inhibit cAMP levels generated through such G-protein-coupled receptors as catecholamine-activated β-adrenergic receptors. Consistent with these antagonistic signaling modes, acute actions of catecholamines cause insulin resistance. Yet, paradoxically, chronically activating adipocytes by catecholamines cause increased glucose tolerance, as does insulin. Recent results have helped to unravel this conundrum by revealing enhanced complexities of these hormones' signaling networks, including identification of unexpected common signaling nodes between these canonically antagonistic hormones.
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Affiliation(s)
- Adilson Guilherme
- Program in Molecular Medicine, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA.
| | - Leslie A Rowland
- Program in Molecular Medicine, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | - Hui Wang
- Program in Molecular Medicine, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | - Michael P Czech
- Program in Molecular Medicine, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA.
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7
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Lee E, Korf H, Vidal-Puig A. An adipocentric perspective on the development and progression of non-alcoholic fatty liver disease. J Hepatol 2023; 78:1048-1062. [PMID: 36740049 DOI: 10.1016/j.jhep.2023.01.024] [Citation(s) in RCA: 39] [Impact Index Per Article: 39.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 12/20/2022] [Accepted: 01/19/2023] [Indexed: 02/07/2023]
Abstract
Alongside the liver, white adipose tissue (WAT) is critical in regulating systemic energy homeostasis. Although each organ has its specialised functions, they must work coordinately to regulate whole-body metabolism. Adipose tissues and the liver are relatively resilient and can adapt to an energy surplus by facilitating triglyceride (TG) storage up to a certain threshold level without significant metabolic disturbances. However, lipid storage in WAT beyond a "personalised" adiposity threshold becomes dysfunctional, leading to metabolic inflexibility, progressive inflammation, and aberrant adipokine secretion. Moreover, the failure of adipose tissue to store and mobilise lipids results in systemic knock-on lipid overload, particularly in the liver. Factors contributing to hepatic lipid overload include lipids released from WAT, dietary fat intake, and enhanced de novo lipogenesis. In contrast, extrahepatic mechanisms counteracting toxic hepatic lipid overload entail coordinated compensation through oxidation of surplus fatty acids in brown adipose tissue and storage of fatty acids as TGs in WAT. Failure of these integrated homeostatic mechanisms leads to quantitative increases and qualitative alterations to the lipidome of the liver. Initially, hepatocytes preferentially accumulate TG species leading to a relatively "benign" non-alcoholic fatty liver. However, with time, inflammatory responses ensue, progressing into more severe conditions such as non-alcoholic steatohepatitis, cirrhosis, and hepatocellular carcinoma, in some individuals (often without an early prognostic clue). Herein, we highlight the pathogenic importance of obesity-induced "adipose tissue failure", resulting in decreased adipose tissue functionality (i.e. fat storage capacity and metabolic flexibility), in the development and progression of NAFL/NASH.
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Affiliation(s)
- Eunyoung Lee
- Metabolic Research Laboratories, Wellcome Trust MRC Institute of Metabolic Science, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK; Department of Medical Physiology, Chiba University, Graduate School of Medicine, Chiba, Japan
| | - Hannelie Korf
- Laboratory of Hepatology, CHROMETA Department, KU Leuven, Leuven, Belgium.
| | - Antonio Vidal-Puig
- Metabolic Research Laboratories, Wellcome Trust MRC Institute of Metabolic Science, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK; Centro de Innvestigacion Principe Felipe, Valencia, Spain; Cambridge University Nanjing Centre of Technology and Innovation, Nanjing, China.
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8
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Vasileva A, Marx T, Beaudry JL, Stern JH. Glucagon receptor signaling at white adipose tissue does not regulate lipolysis. Am J Physiol Endocrinol Metab 2022; 323:E389-E401. [PMID: 36002172 PMCID: PMC9576180 DOI: 10.1152/ajpendo.00078.2022] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Although the physiological role of glucagon receptor signaling in the liver is well defined, the impact of glucagon receptor (Gcgr) signaling on white adipose tissue (WAT) continues to be debated. Although numerous studies propose that glucagon stimulates WAT lipolysis, we lack evidence that physiological concentrations of glucagon regulate WAT lipolysis. In turn, we performed studies in both wild-type and WAT Gcgr knockout mice to determine if glucagon regulates lipolysis at WAT in the mouse. We assessed the effects of fasting and acute exogenous glucagon administration in wild-type C57BL/6J and GcgrAdipocyte+/+ versus GcgrAdipocyte-/- mice. Using an ex vivo lipolysis protocol, we further examined the direct effects of glucagon on physiologically (fasted) and pharmacologically stimulated lipolysis. We found that adipocyte Gcgr expression did not affect fasting-induced lipolysis or hepatic lipid accumulation in lean or diet-induced obese (DIO) mice. Acute glucagon administration did not affect serum nonesterified fatty acids (NEFA), leptin, or adiponectin concentration, but did increase serum glucose and FGF21, regardless of genotype. Glucagon did not affect ex vivo lipolysis in explants from either GcgrAdipocyte+/+ or GcgrAdipocyte-/- mice. Gcgr expression did not affect fasting-induced or isoproterenol-stimulated lipolysis from WAT explants. Moreover, glucagon receptor signaling at WAT did not affect body weight or glucose homeostasis in lean or DIO mice. Our studies have established that physiological levels of glucagon do not regulate WAT lipolysis, either directly or indirectly. Given that glucagon receptor agonism can improve dyslipidemia and decrease hepatic lipid accumulation, it is critical to understand the tissue-specific effects of glucagon receptor action. Unlike the crucial role of hepatic glucagon receptor signaling in maintaining glucose and lipid homeostasis, we observed no metabolic consequence of WAT glucagon receptor deletion.NEW & NOTEWORTHY It has been postulated that glucagon stimulates lipolysis and fatty acid release from white adipose tissue. We observed no metabolic effects of eliminating or activating glucagon receptor signaling at white adipose tissue.
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Affiliation(s)
- Anastasiia Vasileva
- Division of Endocrinology, University of Arizona College of Medicine, Tucson, Arizona
| | - Tyler Marx
- Division of Endocrinology, University of Arizona College of Medicine, Tucson, Arizona
| | - Jacqueline L Beaudry
- Department of Nutritional Sciences, University of Toronto, Toronto, Ontario, Canada
| | - Jennifer H Stern
- Division of Endocrinology, University of Arizona College of Medicine, Tucson, Arizona
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9
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Integrating adipocyte insulin signaling and metabolism in the multi-omics era. Trends Biochem Sci 2022; 47:531-546. [PMID: 35304047 DOI: 10.1016/j.tibs.2022.02.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 02/08/2022] [Accepted: 02/21/2022] [Indexed: 12/16/2022]
Abstract
Insulin stimulates glucose uptake into adipocytes via mTORC2/AKT signaling and GLUT4 translocation and directs glucose carbons into glycolysis, glycerol for TAG synthesis, and de novo lipogenesis. Adipocyte insulin resistance is an early indicator of type 2 diabetes in obesity, a worldwide health crisis. Thus, understanding the interplay between insulin signaling and central carbon metabolism pathways that maintains adipocyte function, blood glucose levels, and metabolic homeostasis is critical. While classically viewed through the lens of individual enzyme-substrate interactions, advances in mass spectrometry are beginning to illuminate adipocyte signaling and metabolic networks on an unprecedented scale, yet this is just the tip of the iceberg. Here, we review how 'omics approaches help to elucidate adipocyte insulin action in cellular time and space.
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10
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Li Y, Li Z, Ngandiri DA, Llerins Perez M, Wolf A, Wang Y. The Molecular Brakes of Adipose Tissue Lipolysis. Front Physiol 2022; 13:826314. [PMID: 35283787 PMCID: PMC8907745 DOI: 10.3389/fphys.2022.826314] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 01/10/2022] [Indexed: 12/11/2022] Open
Abstract
Adaptation to changes in energy availability is pivotal for the survival of animals. Adipose tissue, the body’s largest reservoir of energy and a major source of metabolic fuel, exerts a buffering function for fluctuations in nutrient availability. This functional plasticity ranges from energy storage in the form of triglycerides during periods of excess energy intake to energy mobilization via lipolysis in the form of free fatty acids for other organs during states of energy demands. The subtle balance between energy storage and mobilization is important for whole-body energy homeostasis; its disruption has been implicated as contributing to the development of insulin resistance, type 2 diabetes and cancer cachexia. As a result, adipocyte lipolysis is tightly regulated by complex regulatory mechanisms involving lipases and hormonal and biochemical signals that have opposing effects. In thermogenic brown and brite adipocytes, lipolysis stimulation is the canonical way for the activation of non-shivering thermogenesis. Lipolysis proceeds in an orderly and delicately regulated manner, with stimulation through cell-surface receptors via neurotransmitters, hormones, and autocrine/paracrine factors that activate various intracellular signal transduction pathways and increase kinase activity. The subsequent phosphorylation of perilipins, lipases, and cofactors initiates the translocation of key lipases from the cytoplasm to lipid droplets and enables protein-protein interactions to assemble the lipolytic machinery on the scaffolding perilipins at the surface of lipid droplets. Although activation of lipolysis has been well studied, the feedback fine-tuning is less well appreciated. This review focuses on the molecular brakes of lipolysis and discusses some of the divergent fine-tuning strategies in the negative feedback regulation of lipolysis, including delicate negative feedback loops, intermediary lipid metabolites-mediated allosteric regulation and dynamic protein–protein interactions. As aberrant adipocyte lipolysis is involved in various metabolic diseases and releasing the brakes on lipolysis in thermogenic adipocytes may activate thermogenesis, targeting adipocyte lipolysis is thus of therapeutic interest.
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11
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Zhou H, Zhang J, Yan Z, Qu M, Zhang G, Han J, Wang F, Sun K, Wang L, Yang X. DECR1 directly activates HSL to promote lipolysis in cervical cancer cells. Biochim Biophys Acta Mol Cell Biol Lipids 2021; 1867:159090. [PMID: 34896618 DOI: 10.1016/j.bbalip.2021.159090] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Revised: 11/29/2021] [Accepted: 12/04/2021] [Indexed: 11/30/2022]
Abstract
Fatty acids have a high turnover rate in cancer cells to supply energy for tumor growth and proliferation. Lipolysis is particularly important for the regulation of fatty acid homeostasis and in the maintenance of cancer cells. In the current study, we explored how 2,4-Dienoyl-CoA reductase (DECR1), a short-chain dehydrogenase/reductase associated with mitochondrial and cytoplasmic compartments, promotes cancer cell growth. We report that DECR1 overexpression significantly reduced the triglyceride (TAG) content in HeLa cells; conversely, DECR1 silencing increased intracellular TAG content. Subsequently, our experiments demonstrate that DECR1 promotes lipolysis via effects on hormone sensitive lipase (HSL). The direct interaction of DECR1 with HSL increases HSL phosphorylation and activity, facilitating the translocation of HSL to lipid droplets. The ensuing enhancement of lipolysis thus increases the release of free fatty acids. Downstream effects include the promotion of cervical cancer cell migration and growth, associated with the enhanced levels of p62 protein. In summary, high levels of DECR1 serves to enhance lipolysis and the release of fatty acid energy stores to support cervical cancer cell growth.
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Affiliation(s)
- Huijuan Zhou
- Institute of Physical Science and Information Technology, Institute of Health Sciences Anhui University, Hefei, Anhui Hefei, Anhui 230601, PR China
| | - Jie Zhang
- Institute of Physical Science and Information Technology, Institute of Health Sciences Anhui University, Hefei, Anhui Hefei, Anhui 230601, PR China
| | - ZhongKang Yan
- Institute of Physical Science and Information Technology, Institute of Health Sciences Anhui University, Hefei, Anhui Hefei, Anhui 230601, PR China
| | - Min Qu
- Institute of Physical Science and Information Technology, Institute of Health Sciences Anhui University, Hefei, Anhui Hefei, Anhui 230601, PR China
| | - Gaojian Zhang
- Institute of Physical Science and Information Technology, Institute of Health Sciences Anhui University, Hefei, Anhui Hefei, Anhui 230601, PR China
| | - Jianxiong Han
- Institute of Physical Science and Information Technology, Institute of Health Sciences Anhui University, Hefei, Anhui Hefei, Anhui 230601, PR China
| | - Feifei Wang
- Institute of Physical Science and Information Technology, Institute of Health Sciences Anhui University, Hefei, Anhui Hefei, Anhui 230601, PR China
| | - Kai Sun
- School of Life Science, Anhui University, Hefei, Anhui Hefei, Anhui 230601, PR China
| | - Lili Wang
- School of Life Science, Anhui University, Hefei, Anhui Hefei, Anhui 230601, PR China
| | - Xingyuan Yang
- Institute of Physical Science and Information Technology, Institute of Health Sciences Anhui University, Hefei, Anhui Hefei, Anhui 230601, PR China.
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12
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Guo F, Seldin M, Péterfy M, Charugundla S, Zhou Z, Lee SD, Mouton A, Rajbhandari P, Zhang W, Pellegrini M, Tontonoz P, Lusis AJ, Shih DM. NOTUM promotes thermogenic capacity and protects against diet-induced obesity in male mice. Sci Rep 2021; 11:16409. [PMID: 34385484 PMCID: PMC8361163 DOI: 10.1038/s41598-021-95720-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Accepted: 07/28/2021] [Indexed: 11/29/2022] Open
Abstract
We recently showed that NOTUM, a liver-secreted Wnt inhibitor, can acutely promote browning of white adipose. We now report studies of chronic overexpression of NOTUM in liver indicating that it protects against diet-induced obesity and improves glucose homeostasis in mice. Adeno-associated virus (AAV) vectors were used to overexpress GFP or mouse Notum in the livers of male C57BL/6J mice and the mice were fed an obesifying diet. After 14 weeks of high fat, high sucrose diet feeding, the AAV-Notum mice exhibited decreased obesity and improved glucose tolerance compared to the AAV-GFP mice. Gene expression and immunoblotting analysis of the inguinal fat and brown fat revealed increased expression of beige/brown adipocyte markers in the AAV-Notum group, suggesting enhanced thermogenic capacity by NOTUM. A β3 adrenergic receptor agonist-stimulated lipolysis test suggested increased lipolysis capacity by NOTUM. The levels of collagen and C–C motif chemokine ligand 2 (CCL2) in the epididymal white adipose tissue of the AAV-Notum mice were significantly reduced, suggesting decreased fibrosis and inflammation, respectively. RNA sequencing analysis of inguinal white adipose of 4-week chow diet-fed mice revealed a highly significant enrichment of extracellular matrix (ECM) functional cluster among the down-regulated genes in the AAV-Notum group, suggesting a potential mechanism contributing to improved glucose homeostasis. Our in vitro studies demonstrated that recombinant human NOTUM protein blocked the inhibitory effects of WNT3A on brown adipocyte differentiation. Furthermore, NOTUM attenuated WNT3A’s effects on upregulation of TGF-β signaling and its downstream targets. Overall, our data suggest that NOTUM modulates adipose tissue function by promoting thermogenic capacity and inhibiting fibrosis through inhibition of Wnt signaling.
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Affiliation(s)
- Fangfei Guo
- Department of Microbiology, Immunology, and Molecular Genetics, Division of Cardiology, Department of Medicine, Department of Human Genetics, University of California, 10833 Le Conte Avenue, A2-237 CHS, Los Angeles, CA, 90095-1679, USA
| | - Marcus Seldin
- Department of Biological Chemistry and Center for Epigenetics and Metabolism, University of California, Irvine, CA, 92697, USA
| | - Miklós Péterfy
- Department of Basic Medical Sciences, Western University of Health Sciences, Pomona, CA, 91766, USA
| | - Sarada Charugundla
- Department of Microbiology, Immunology, and Molecular Genetics, Division of Cardiology, Department of Medicine, Department of Human Genetics, University of California, 10833 Le Conte Avenue, A2-237 CHS, Los Angeles, CA, 90095-1679, USA
| | - Zhiqiang Zhou
- Department of Microbiology, Immunology, and Molecular Genetics, Division of Cardiology, Department of Medicine, Department of Human Genetics, University of California, 10833 Le Conte Avenue, A2-237 CHS, Los Angeles, CA, 90095-1679, USA
| | - Stephen D Lee
- Department of Pathology and Laboratory Medicine, University of California, Los Angeles, CA, 90095, USA
| | - Alice Mouton
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA, 90095, USA
| | - Prashant Rajbhandari
- Diabetes, Obesity, and Metabolism Institute, Icahn School of Medicine Mount Sinai, New York, NY, 10029, USA
| | - Wenchao Zhang
- Department of Microbiology, Immunology, and Molecular Genetics, Division of Cardiology, Department of Medicine, Department of Human Genetics, University of California, 10833 Le Conte Avenue, A2-237 CHS, Los Angeles, CA, 90095-1679, USA.,The Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education, Chinese National Health Commission and Chinese Academy of Medical Sciences, The State and Shandong Province Joint Key Laboratory of Translational Cardiovascular Medicine, Department of Cardiology, Qilu Hospital, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China.,Department of Critical Care Medicine, Qilu Hospital, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
| | - Matteo Pellegrini
- Molecular, Cell, and Developmental Biology, University of California, Los Angeles, CA, 90095, USA
| | - Peter Tontonoz
- Department of Pathology and Laboratory Medicine, University of California, Los Angeles, CA, 90095, USA
| | - Aldons J Lusis
- Department of Microbiology, Immunology, and Molecular Genetics, Division of Cardiology, Department of Medicine, Department of Human Genetics, University of California, 10833 Le Conte Avenue, A2-237 CHS, Los Angeles, CA, 90095-1679, USA
| | - Diana M Shih
- Department of Microbiology, Immunology, and Molecular Genetics, Division of Cardiology, Department of Medicine, Department of Human Genetics, University of California, 10833 Le Conte Avenue, A2-237 CHS, Los Angeles, CA, 90095-1679, USA.
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Tegeder I, Kögel D. When lipid homeostasis runs havoc: Lipotoxicity links lysosomal dysfunction to autophagy. Matrix Biol 2021; 100-101:99-117. [DOI: 10.1016/j.matbio.2020.11.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Revised: 11/29/2020] [Accepted: 11/30/2020] [Indexed: 02/07/2023]
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14
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Harney DJ, Cielesh M, Chu R, Cooke KC, James DE, Stöckli J, Larance M. Proteomics analysis of adipose depots after intermittent fasting reveals visceral fat preservation mechanisms. Cell Rep 2021; 34:108804. [PMID: 33657384 DOI: 10.1016/j.celrep.2021.108804] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 01/22/2021] [Accepted: 02/05/2021] [Indexed: 12/21/2022] Open
Abstract
Intermittent fasting is a beneficial dietary treatment for obesity. But the response of each distinct adipose depot is currently poorly defined. Here we explore the response of key adipose depots to every-other-day fasting (EODF) in mice using proteomics. A key change in subcutaneous white adipose tissue (scWAT) and visceral WAT (vWAT) depots is an increase in mitochondrial protein content after EODF. This effect is correlated with increased fatty acid synthesis enzymes in both WAT depots but not in brown adipose tissue. Strikingly, EODF treatment downregulates lipolysis specifically in vWAT, mediated by a large decrease in the abundance of the catecholamine receptor (ADRB3). Together, these changes are important for preservation of the visceral lipid store during EODF. Enrichment analysis highlights downregulation of inflammatory collagen IV specifically in vWAT, allowing improved insulin sensitivity. This resource for adipose-depot-specific fasting adaptations in mice is available using a web-based interactive visualization.
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Affiliation(s)
- Dylan J Harney
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, NSW, Australia
| | - Michelle Cielesh
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, NSW, Australia
| | - Renee Chu
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, NSW, Australia
| | - Kristen C Cooke
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, NSW, Australia
| | - David E James
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, NSW, Australia; School of Medical Sciences, University of Sydney, Camperdown, NSW, Australia
| | - Jacqueline Stöckli
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, NSW, Australia
| | - Mark Larance
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, NSW, Australia.
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15
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Huang G, Guo X, Guo J, Zhang P, Liang W, Bai C, Zhang Y. ABHD15 promotes cell viability, glycolysis, and inhibits apoptosis in cardiomyocytes under hypoxia. Nutr Metab Cardiovasc Dis 2021; 31:681-690. [PMID: 33257193 DOI: 10.1016/j.numecd.2020.09.033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 09/15/2020] [Accepted: 09/30/2020] [Indexed: 11/18/2022]
Abstract
BACKGROUND AND AIMS Myocardial infarction (MI) has been an important heart disease affecting human health. The aim of this study was to investigate the regulatory effect of abhydrolase domain containing 15 (ABHD15) on hypoxic cardiomyocytes. METHODS AND RESULTS Hypoxic cardiomyocytes are commonly used as an vitro model for the study of MI. We found that cardiomyocyte viability was decreased under hypoxia, but cell glucose uptake, insulin receptor phosphorylation level and apoptosis were increased. Interestingly, ABHD15 expression was up-regulated in hypoxia-induced cardiomyocytes. Then, we identified the function of ABHD15 in hypoxic cardiomyocytes by using ABHD15 overexpression vector or short interfering RNA (siRNA) against ABHD15. The results showed that overexpression of ABHD15 promoted hypoxic cardiomyocyte viability, glucose uptake and IR phosphorylation (p-IR), and inhibited cell apoptosis. However, knockdown of ABHD15 attenuated hypoxic cardiomyocyte viability, glucose uptake and IR phosphorylation, and promoted apoptosis. Moreover, we found that ABHD15 promoted glucose transporter 4 (GLUT4) expression, translocation and enhance rate-limiting enzyme activation of glycolysis, thereby affecting glucose uptake. Furthermore, our study suggested that ABHD15 may affect the viability and apoptosis of hypoxic cardiomyocytes through IR/Ras/Raf/ERK/MEK and IR/PI3K/AKT/Bcl2/Bad/caspase9 signaling pathways, respectively. When the phosphorylation of IR, Raf or ERK was blocked by inhibitors, the protective effect of overexpressing ABHD15 on the viability of hypoxic cardiomyocytes was eliminated. Furthermore, inhibiting the phosphorylation of IR, AKT or Bcl2 abolished the inhibitory effect of overexpressing ABHD15 on hypoxic cardiomyocyte apoptosis. CONCLUSION ABHD15 regulated myocardial cell viability, glycolysis, and apoptosis under hypoxia, providing a novel potential therapeutic strategy for MI.
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Affiliation(s)
- Guotao Huang
- Cardiology Department, The First Affiliated Hospital of Xinxiang Medical University, Xinxiang, China
| | - Xiaoliang Guo
- Cardiology Department, The First Affiliated Hospital of Xinxiang Medical University, Xinxiang, China
| | - Junxia Guo
- Cardiology Department, The First Affiliated Hospital of Xinxiang Medical University, Xinxiang, China
| | - Peiyong Zhang
- Cardiology Department, The First Affiliated Hospital of Xinxiang Medical University, Xinxiang, China
| | - Wanqian Liang
- Cardiology Department, The First Affiliated Hospital of Xinxiang Medical University, Xinxiang, China
| | - Caiyan Bai
- Cardiology Department, The First Affiliated Hospital of Xinxiang Medical University, Xinxiang, China
| | - Yongchun Zhang
- Cardiology Department, The First Affiliated Hospital of Xinxiang Medical University, Xinxiang, China.
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16
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Adipocyte lipolysis: from molecular mechanisms of regulation to disease and therapeutics. Biochem J 2020; 477:985-1008. [PMID: 32168372 DOI: 10.1042/bcj20190468] [Citation(s) in RCA: 96] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Revised: 02/19/2020] [Accepted: 02/26/2020] [Indexed: 12/20/2022]
Abstract
Fatty acids (FAs) are stored safely in the form of triacylglycerol (TAG) in lipid droplet (LD) organelles by professional storage cells called adipocytes. These lipids are mobilized during adipocyte lipolysis, the fundamental process of hydrolyzing TAG to FAs for internal or systemic energy use. Our understanding of adipocyte lipolysis has greatly increased over the past 50 years from a basic enzymatic process to a dynamic regulatory one, involving the assembly and disassembly of protein complexes on the surface of LDs. These dynamic interactions are regulated by hormonal signals such as catecholamines and insulin which have opposing effects on lipolysis. Upon stimulation, patatin-like phospholipase domain containing 2 (PNPLA2)/adipocyte triglyceride lipase (ATGL), the rate limiting enzyme for TAG hydrolysis, is activated by the interaction with its co-activator, alpha/beta hydrolase domain-containing protein 5 (ABHD5), which is normally bound to perilipin 1 (PLIN1). Recently identified negative regulators of lipolysis include G0/G1 switch gene 2 (G0S2) and PNPLA3 which interact with PNPLA2 and ABHD5, respectively. This review focuses on the dynamic protein-protein interactions involved in lipolysis and discusses some of the emerging concepts in the control of lipolysis that include allosteric regulation and protein turnover. Furthermore, recent research demonstrates that many of the proteins involved in adipocyte lipolysis are multifunctional enzymes and that lipolysis can mediate homeostatic metabolic signals at both the cellular and whole-body level to promote inter-organ communication. Finally, adipocyte lipolysis is involved in various diseases such as cancer, type 2 diabetes and fatty liver disease, and targeting adipocyte lipolysis is of therapeutic interest.
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17
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Carotti S, Aquilano K, Valentini F, Ruggiero S, Alletto F, Morini S, Picardi A, Antonelli-Incalzi R, Lettieri-Barbato D, Vespasiani-Gentilucci U. An overview of deregulated lipid metabolism in nonalcoholic fatty liver disease with special focus on lysosomal acid lipase. Am J Physiol Gastrointest Liver Physiol 2020; 319:G469-G480. [PMID: 32812776 DOI: 10.1152/ajpgi.00049.2020] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Obesity and type 2 diabetes are frequently complicated by excess fat accumulation in the liver, which is known as nonalcoholic fatty liver disease (NAFLD). In this context, liver steatosis develops as a result of the deregulation of pathways controlling de novo lipogenesis and fat catabolism. Recent evidences suggest the clinical relevance of a reduction in the activity of lysosomal acid lipase (LAL), which is a key enzyme for intracellular fat disposal, in patients with NAFLD. In this review, we provided a comprehensive overview of the critical steps in hepatic fat metabolism and alterations in these pathways in NAFLD, with a special focus on lipophagy and LAL activity. During NAFLD, hepatic fat metabolism is impaired at several levels, which is significantly contributed to by impaired lipophagy, in which reduced LAL activity may play an important role. For further research and intervention in NAFLD, targeting LAL activity may provide interesting perspectives.
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Affiliation(s)
- Simone Carotti
- Unit of Microscopic and Ultrastructural Anatomy, University Campus Bio-Medico, Rome, Italy
| | - Katia Aquilano
- Department of Biology, University of Rome, Tor Vergata, Rome, Italy
| | - Francesco Valentini
- Unit of Microscopic and Ultrastructural Anatomy, University Campus Bio-Medico, Rome, Italy
| | - Sergio Ruggiero
- Unit of Microscopic and Ultrastructural Anatomy, University Campus Bio-Medico, Rome, Italy
| | - Francesca Alletto
- Unit of Internal Medicine and Hepatology, University Campus Bio-Medico, Rome, Italy
| | - Sergio Morini
- Unit of Microscopic and Ultrastructural Anatomy, University Campus Bio-Medico, Rome, Italy
| | - Antonio Picardi
- Unit of Internal Medicine and Hepatology, University Campus Bio-Medico, Rome, Italy
| | | | - Daniele Lettieri-Barbato
- Department of Biology, University of Rome, Tor Vergata, Rome, Italy.,IRCCS Fondazione Santa Lucia, Rome, Italy
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18
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Insulin and β-adrenergic receptors mediate lipolytic and anti-lipolytic signalling that is not altered by type 2 diabetes in human adipocytes. Biochem J 2020; 476:2883-2908. [PMID: 31519735 PMCID: PMC6792037 DOI: 10.1042/bcj20190594] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Revised: 09/11/2019] [Accepted: 09/12/2019] [Indexed: 12/21/2022]
Abstract
Control of fatty acid storage and release in adipose tissue is fundamental in energy homeostasis and the development of obesity and type 2 diabetes. We here take the whole signalling network into account to identify how insulin and β-adrenergic stimulation in concert controls lipolysis in mature subcutaneous adipocytes obtained from non-diabetic and, in parallel, type 2 diabetic women. We report that, and show how, the anti-lipolytic effect of insulin can be fully explained by protein kinase B (PKB/Akt)-dependent activation of the phosphodiesterase PDE3B. Through the same PKB-dependent pathway β-adrenergic receptor signalling, via cAMP and PI3Kα, is anti-lipolytic and inhibits its own stimulation of lipolysis by 50%. Through this pathway both insulin and β-adrenergic signalling control phosphorylation of FOXO1. The dose–response of lipolysis is bell-shaped, such that insulin is anti-lipolytic at low concentrations, but at higher concentrations of insulin lipolysis was increasingly restored due to inhibition of PDE3B. The control of lipolysis was not altered in adipocytes from diabetic individuals. However, the release of fatty acids was increased by 50% in diabetes due to reduced reesterification of lipolytically liberated fatty acids. In conclusion, our results reveal mechanisms of control by insulin and β-adrenergic stimulation — in human adipocytes — that define a network of checks and balances ensuring robust control to secure uninterrupted supply of fatty acids without reaching concentrations that put cellular integrity at risk. Moreover, our results define how selective insulin resistance leave lipolytic control by insulin unaltered in diabetes, while the fatty acid release is substantially increased.
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19
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Czech MP. Mechanisms of insulin resistance related to white, beige, and brown adipocytes. Mol Metab 2020; 34:27-42. [PMID: 32180558 PMCID: PMC6997501 DOI: 10.1016/j.molmet.2019.12.014] [Citation(s) in RCA: 116] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 12/21/2019] [Accepted: 12/23/2019] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND The diminished glucose lowering effect of insulin in obesity, called "insulin resistance," is associated with glucose intolerance, type 2 diabetes, and other serious maladies. Many publications on this topic have suggested numerous hypotheses on the molecular and cellular disruptions that contribute to the syndrome. However, significant uncertainty remains on the mechanisms of its initiation and long-term maintenance. SCOPE OF REVIEW To simplify insulin resistance analysis, this review focuses on the unifying concept that adipose tissue is a central regulator of systemic glucose homeostasis by controlling liver and skeletal muscle metabolism. Key aspects of adipose function related to insulin resistance reviewed are: 1) the modes by which specific adipose tissues control hepatic glucose output and systemic glucose disposal, 2) recently acquired understanding of the underlying mechanisms of these modes of regulation, and 3) the steps in these pathways adversely affected by obesity that cause insulin resistance. MAJOR CONCLUSIONS Adipocyte heterogeneity is required to mediate the multiple pathways that control systemic glucose tolerance. White adipocytes specialize in sequestering triglycerides away from the liver, muscle, and other tissues to limit toxicity. In contrast, brown/beige adipocytes are very active in directly taking up glucose in response to β adrenergic signaling and insulin and enhancing energy expenditure. Nonetheless, white, beige, and brown adipocytes all share the common feature of secreting factors and possibly exosomes that act on distant tissues to control glucose homeostasis. Obesity exerts deleterious effects on each of these adipocyte functions to cause insulin resistance.
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Affiliation(s)
- Michael P Czech
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA, USA.
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20
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Li Y, Peng M, Zeng T, Zheng J, Liao Y, Zhang H, Yang S, Chen L. Protein Arginine Methyltransferase 4 Regulates Adipose Tissue Lipolysis in Type 1 Diabetic Mice. Diabetes Metab Syndr Obes 2020; 13:535-544. [PMID: 32161480 PMCID: PMC7049750 DOI: 10.2147/dmso.s235869] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 02/10/2020] [Indexed: 12/19/2022] Open
Abstract
PURPOSE Hypertriglyceridemia is considered to be driven by increased lipolysis in type 1 diabetes mellitus (T1DM). However, information regarding the transcriptional circuitry that governs lipolysis remains incomplete in T1DM. Protein arginine methyltransferase 4 (PRMT4), a transcriptional coactivation factor, promotes autophagy and may play an important role in lipolysis. We wonder whether activated lipolysis in T1DM is regulated by PRMT4. MATERIALS AND METHODS Recombinant adeno-associated virus was adopted to overexpress PRMT4 in adipose tissue of mice. Streptozotocin (150 mg/kg) was injected intraperitoneally into mice to induce T1DM. Plasma insulin, triglycerides, free fatty acids (FFAs) levels were determined using commercial assay kits. Differentiated adipocytes were applied to verify the regulation of PRMT4 on lipolysis. RESULTS Elevated serum triglycerides and FFAs were observed in PRMT4-overexpressed T1DM mice. We also observed that PRMT4 over-expression induced the decrease of fat pads weights and adipocyte sizes. Moreover, expression levels of lipolysis-related molecules, including ATGL, HSL, and MAGL, and HSL phosphorylation levels were increased in PRMT4-overexpressed mice when compared to those of control mice. In vitro, PRMT4 promoted FFAs release and activated HSL phosphorylation, whereas PRMT4 knockdown inhibited these processes. CONCLUSION PRMT4 promotes lipolysis and increases serum triglyceride in T1DM.
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Affiliation(s)
- Yuanxiang Li
- Department of Endocrinology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei430022, People’s Republic of China
| | - Miaomiao Peng
- Department of Endocrinology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei430022, People’s Republic of China
| | - Tianshu Zeng
- Department of Endocrinology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei430022, People’s Republic of China
| | - Juan Zheng
- Department of Endocrinology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei430022, People’s Republic of China
| | - Yunfei Liao
- Department of Endocrinology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei430022, People’s Republic of China
| | - Hao Zhang
- Department of Endocrinology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei430022, People’s Republic of China
| | - Songtao Yang
- Department of Endocrinology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei430022, People’s Republic of China
| | - Lulu Chen
- Department of Endocrinology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei430022, People’s Republic of China
- Correspondence: Lulu Chen Email
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21
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Kearney AL, Cooke KC, Norris DM, Zadoorian A, Krycer JR, Fazakerley DJ, Burchfield JG, James DE. Serine 474 phosphorylation is essential for maximal Akt2 kinase activity in adipocytes. J Biol Chem 2019; 294:16729-16739. [PMID: 31548312 DOI: 10.1074/jbc.ra119.010036] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Revised: 09/15/2019] [Indexed: 01/06/2023] Open
Abstract
The Ser/Thr protein kinase Akt regulates essential biological processes such as cell survival, growth, and metabolism. Upon growth factor stimulation, Akt is phosphorylated at Ser474; however, how this phosphorylation contributes to Akt activation remains controversial. Previous studies, which induced loss of Ser474 phosphorylation by ablating its upstream kinase mTORC2, have implicated Ser474 phosphorylation as a driver of Akt substrate specificity. Here we directly studied the role of Akt2 Ser474 phosphorylation in 3T3-L1 adipocytes by preventing Ser474 phosphorylation without perturbing mTORC2 activity. This was achieved by utilizing a chemical genetics approach, where ectopically expressed S474A Akt2 was engineered with a W80A mutation to confer resistance to the Akt inhibitor MK2206, and thus allow its activation independent of endogenous Akt. We found that insulin-stimulated phosphorylation of four bona fide Akt substrates (TSC2, PRAS40, FOXO1/3a, and AS160) was reduced by ∼50% in the absence of Ser474 phosphorylation. Accordingly, insulin-stimulated mTORC1 activation, protein synthesis, FOXO nuclear exclusion, GLUT4 translocation, and glucose uptake were attenuated upon loss of Ser474 phosphorylation. We propose a model where Ser474 phosphorylation is required for maximal Akt2 kinase activity in adipocytes.
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Affiliation(s)
- Alison L Kearney
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Kristen C Cooke
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Dougall M Norris
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Armella Zadoorian
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales 2006, Australia
| | - James R Krycer
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Daniel J Fazakerley
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales 2006, Australia
| | - James G Burchfield
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales 2006, Australia
| | - David E James
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales 2006, Australia .,Sydney Medical School, University of Sydney, Sydney, New South Wales 2006, Australia
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