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Li F, Grushin K, Coleman J, Pincet F, Rothman JE. Diacylglycerol-dependent hexamers of the SNARE-assembling chaperone Munc13-1 cooperatively bind vesicles. Proc Natl Acad Sci U S A 2023; 120:e2306086120. [PMID: 37883433 PMCID: PMC10623011 DOI: 10.1073/pnas.2306086120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Accepted: 09/28/2023] [Indexed: 10/28/2023] Open
Abstract
Munc13-1 is essential for vesicle docking and fusion at the active zone of synapses. Here, we report that Munc13-1 self-assembles into molecular clusters within diacylglycerol-rich microdomains present in phospholipid bilayers. Although the copy number of Munc13-1 molecules in these clusters has a broad distribution, a systematic Poisson analysis shows that this is most likely the result of two molecular species: monomers and mainly hexameric oligomers. Each oligomer is able to capture one vesicle independently. Hexamers have also been observed in crystals of Munc13-1 that form between opposed phospholipid bilayers [K. Grushin, R. V. Kalyana Sundaram, C. V. Sindelar, J. E. Rothman, Proc. Natl. Acad. Sci. U.S.A. 119, e2121259119 (2022)]. Mutations targeting the contacts stabilizing the crystallographic hexagons also disrupt the isolated hexamers, suggesting they are identical. Additionally, these mutations also convert vesicle binding from a cooperative to progressive mode. Our study provides an independent approach showing that Munc13-1 can form mainly hexamers on lipid bilayers each capable of vesicle capture.
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Affiliation(s)
- Feng Li
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT06520
- Nanobiology Institute, School of Medicine, Yale University, West Haven, CT06516
| | - Kirill Grushin
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT06520
- Nanobiology Institute, School of Medicine, Yale University, West Haven, CT06516
| | - Jeff Coleman
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT06520
- Nanobiology Institute, School of Medicine, Yale University, West Haven, CT06516
| | - Frederic Pincet
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT06520
- Nanobiology Institute, School of Medicine, Yale University, West Haven, CT06516
- Laboratoire de Physique de l’Ecole normale supérieure, Département de Physique, Ecole Normale Supérieure, Université Paris Sciences & Lettres CNRS, Sorbonne Université, Université de Paris, ParisF-75005, France
| | - James E. Rothman
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT06520
- Nanobiology Institute, School of Medicine, Yale University, West Haven, CT06516
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Grapentine S, Singh RK, Bakovic M. Skeletal Muscle Consequences of Phosphatidylethanolamine Synthesis Deficiency. FUNCTION 2023; 4:zqad020. [PMID: 37342414 PMCID: PMC10278983 DOI: 10.1093/function/zqad020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Revised: 04/24/2023] [Accepted: 04/25/2023] [Indexed: 06/22/2023] Open
Abstract
The maintenance of phospholipid homeostasis is increasingly being implicated in metabolic health. Phosphatidylethanolamine (PE) is the most abundant phospholipid on the inner leaflet of cellular membranes, and we have previously shown that mice with a heterozygous ablation of the PE synthesizing enzyme, Pcyt2 (Pcyt2+/-), develop obesity, insulin resistance, and NASH. Skeletal muscle is a major determinant of systemic energy metabolism, making it a key player in metabolic disease development. Both the total PE levels and the ratio of PE to other membrane lipids in skeletal muscle are implicated in insulin resistance; however, the underlying mechanisms and the role of Pcyt2 regulation in this association remain unclear. Here, we show how reduced phospholipid synthesis due to Pcyt2 deficiency causes Pcyt2+/- skeletal muscle dysfunction and metabolic abnormalities. Pcyt2+/- skeletal muscle exhibits damage and degeneration, with skeletal muscle cell vacuolization, disordered sarcomeres, mitochondria ultrastructure irregularities and paucity, inflammation, and fibrosis. There is intramuscular adipose tissue accumulation, and major disturbances in lipid metabolism with impaired FA mobilization and oxidation, elevated lipogenesis, and long-chain fatty acyl-CoA, diacylglycerol, and triacylglycerol accumulation. Pcyt2+/- skeletal muscle exhibits perturbed glucose metabolism with elevated glycogen content, impaired insulin signaling, and reduced glucose uptake. Together, this study lends insight into the critical role of PE homeostasis in skeletal muscle metabolism and health with broad implications on metabolic disease development.
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Affiliation(s)
- Sophie Grapentine
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph N1G 2W1, Canada
| | - Rathnesh K Singh
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph N1G 2W1, Canada
| | - Marica Bakovic
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph N1G 2W1, Canada
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The role of altered fatty acid in pathological scars and their dermal fibroblasts. Chin J Traumatol 2022; 25:218-223. [PMID: 35478090 PMCID: PMC9252927 DOI: 10.1016/j.cjtee.2022.03.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 03/12/2022] [Accepted: 03/23/2022] [Indexed: 02/04/2023] Open
Abstract
PURPOSE The proposed pathological mechanism for scar formation is controversial, and increased attention has been paid to the fatty acids (FAs) in the formation of pathological scars. Notably, FAs are known to be important in inflammation and mechanotransduction, which is closely related to scar formation. Therefore, it is necessary to clarify the roles of FA in scar formation. METHODS Hypertrophic scar and keloid formed for more than a year and without other treatment, as well as normal skin samples were obtained from patients who underwent plastic surgery. Finally, keloids (n = 10), hypertrophic scars (n = 10), and normal skin samples (n = 10) were collected under informed consent. Primary dermal fibroblasts were isolated and cultured. The amount and variety of FAs were detected by lipid chromatography-mass spectrometry. Immunohistochemistry, real-time PCR, and western blotting were used to verify the expression of sterol regulatory element-binding protein-1 (SREBP1) and fatty acid synthase (FASN) in the samples and their fibroblasts. Student's t-test, ANOVA, and orthogonal partial least square discriminant analysis were performed for statistical analysis (∗p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.001, ∗∗∗∗p < 0.0001). RESULTS Compared with full-thickness normal skin, there were 27 differential FAs in keloids and 15 differential FAs in hypertrophic scars (∗p < 0.05 and variable influence on projection >1.0). The expression of SREBP1 and FASN was lower in pathological scars both at mRNA and protein levels (all ∗p < 0.05). However, the mRNA levels of SREBP1 (∗∗∗p = 0.0002) and FASN (∗∗∗p = 0.0021) in keloid-derived fibroblasts were higher than that in normal skin fibroblasts (NFBs), while the expression in hypertrophic scar-derived fibroblasts was lower than that in NFBs (both ∗p < 0.05). Whereas there was no significant difference in FASN protein expression between keloid-derived fibroblasts and NFBs (p > 0.05). CONCLUSION FAs involved in pathological scars are abnormally changed in scar formation. Thus, fatty acid-derived inflammation and de novo synthesis pathway of FA may play a key role in the formation of pathological scars.
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Murtaza B, Hichami A, Khan AS, Plesnik J, Sery O, Dietrich A, Birnbaumer L, Khan NA. Implication of TRPC3 channel in gustatory perception of dietary lipids. Acta Physiol (Oxf) 2021; 231:e13554. [PMID: 32882106 DOI: 10.1111/apha.13554] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 08/09/2020] [Accepted: 08/27/2020] [Indexed: 12/17/2022]
Abstract
AIM The pathogenesis of obesity has been associated with high intake of dietary fat, and some recent studies have explored the cellular mechanisms of oro-sensory detection of dietary fatty acids. We further assessed the role of transient receptor potential canonical (TRPC) channels in oro-sensory perception of dietary lipids. METHODS We determined by RT-qPCR and western blotting the expression of TRPC3/6/7 channels in mouse fungiform taste bud cells (mTBC). Immunocytochemistry was used to explore whether TRPC3 channels were co-expressed with fatty acid receptors. We employed wild-type (WT) mTBC, and those transfected with small interfering RNAs (siRNAs) against TRPC3 or STIM1. Ca2+ signalling was studied in TBC from TRPC3-/- mice and their WT littermates. RESULTS We demonstrate that mouse fungiform taste bud cells (mTBC) express TRPC3, but not TRPC6 or TRPC7 channels, and their inactivation by siRNA or experiments on TBC from TRPC3-/- mice brought about a decrease in fatty acid-induced gustatory Ca2+ signalling, coupled with taste bud CD36 lipid sensor. TRPC3 channel activation was found to be under the control of STIM1 in lingual mTBC. Behavioural studies showed that spontaneous preference for a dietary long-chain fatty acid was abolished in TRPC3-/- mice, and in mice wherein lingual TRPC3 expression was silenced by employing siRNA. CONCLUSION We report that lingual TRPC3 channels are critically involved in fat taste perception.
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Affiliation(s)
- Babar Murtaza
- U1231 INSERM/UB/AgroSup Physiologie de la Nutrition & Toxicologie Université de Bourgogne‐Franche Comté (UBFC) Dijon France
| | - Aziz Hichami
- U1231 INSERM/UB/AgroSup Physiologie de la Nutrition & Toxicologie Université de Bourgogne‐Franche Comté (UBFC) Dijon France
| | - Amira S. Khan
- U1231 INSERM/UB/AgroSup Physiologie de la Nutrition & Toxicologie Université de Bourgogne‐Franche Comté (UBFC) Dijon France
| | - Jiri Plesnik
- U1231 INSERM/UB/AgroSup Physiologie de la Nutrition & Toxicologie Université de Bourgogne‐Franche Comté (UBFC) Dijon France
- Laboratory of Neurobiology and Molecular Psychiatry Department of Biochemistry Faculty of Science Masaryk University Brno Czech Republic
| | - Omar Sery
- Laboratory of Neurobiology and Molecular Psychiatry Department of Biochemistry Faculty of Science Masaryk University Brno Czech Republic
- Laboratory of Neurobiology and Pathological Physiology Institute of Animal Physiology and Genetics Academy of Sciences of the Czech Republic Brno Czech Republic
| | - Alexander Dietrich
- Walther‐Straub‐Institute of Pharmacology and Toxicology, Member of the German Center for Lung Research (DZL) LMU Munich Munich Germany
| | - Lutz Birnbaumer
- Neurobiology Laboratory National Institute of Environmental Health Sciences Research Triangle Park NC USA
- Institute of Biomedical Research (BIOMED) Catholic University of Argentina Buenos Aires Argentina
| | - Naim A. Khan
- U1231 INSERM/UB/AgroSup Physiologie de la Nutrition & Toxicologie Université de Bourgogne‐Franche Comté (UBFC) Dijon France
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Kobeissy H, Hage-Sleiman R, Dakdouk Z, Kozhaya L, Dbaibo G. Crosstalk between Noxa, Bcl-2, and ceramide in mediating p53-dependent apoptosis in Molt-4 human T-cell leukemia. Mol Cell Biochem 2020; 475:215-226. [PMID: 32767230 DOI: 10.1007/s11010-020-03874-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 08/01/2020] [Indexed: 02/06/2023]
Abstract
Ionizing radiation induces apoptosis in human Molt-4 leukemia cells in a p53-dependent manner. The tumor suppressor p53 stimulates various downstream targets that presumably trigger, individually or in concert, de novo ceramide synthesis and intrinsic apoptosis via mitochondrial outer membrane permeabilization (MOMP). Among these targets, BH3-only protein Noxa was found to be promptly activated by p53 prior to ceramide accumulation and apoptosis in response to irradiation. To evaluate the relation between Noxa and ceramide in irradiation-induced apoptosis, Noxa was silenced in Molt-4 cells and apoptosis, p53 expression, and ceramide accumulation were assessed in response to irradiation. In the absence of Noxa, irradiation of Molt-4 cells still induced apoptosis in a p53-dependent manner however ceramide levels decreased significantly although they remained higher than untreated control. Upon irradiation, Noxa was found to translocate to the mitochondria where endogenous ceramide accumulation was observed. In contrast, overexpression of Bcl-2, another mitochondrial protein, in Molt-4 cells abolished the endogenous ceramide accumulation and apoptosis. In irradiation-induced, p53-dependent pathways of apoptosis, the pro-apoptotic Noxa represents one of several, yet to be identified, pathways simultaneously triggered by p53 to produce mitochondrial ceramide accumulation and apoptosis. In contrast, Bcl-2 functions as a broader inhibitor of both ceramide accumulation and apoptosis. Altogether, these results indicate that members of the Bcl-2 family differentially regulate ceramide accumulation and reveal the existence of crosstalk between Bcl-2 family members and ceramide in mediating p53-dependent apoptosis in Molt-4 human T-cell leukemia.
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Affiliation(s)
- Hadile Kobeissy
- Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
| | - Rouba Hage-Sleiman
- Department of Biology, Faculty of Sciences, Lebanese University, Hadath, Lebanon.
| | - Zeinab Dakdouk
- Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
| | - Lina Kozhaya
- Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
| | - Ghassan Dbaibo
- Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, Beirut, Lebanon. .,Department of Pediatrics and Adolescent Medicine, Center for Infectious Diseases Research, Faculty of Medicine, American University of Beirut, Beirut, Lebanon.
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Lindsay MA, Daniels I, Fletcher J. Phospholipases and the Activation and Priming of Neutrophils by Peritoneal Dialysis Effluent. Perit Dial Int 2020. [DOI: 10.1177/089686089701700510] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
ObjectiveTo investigate the role of phospholipases during the activation and priming of neutrophil nicotinamide adenine dinucleotide phosphate (NADPH) oxidase by peritoneal dialysis effluent (PDE).DesignExamine the action of 4-hour dwell PDE upon phospholipase activation in the circulating neutrophils obtained from healthy individuals.ResultsWe have previously reported that PDE stimulated superoxide release by the NADPH oxidase of human neutrophils and primed the response to the bacterial peptide, fMLP (fMetLeuPhe). To elucidate the biochemical mechanisms underlying these observations, we have examined the roles of phospholipases (PL) C, D, and A2, whose activation causes the release of a range of intracellular secondary messengers. Following fMLP stimulation, we observed a rapid activation of both PLC and PLD as well as a small but nonsignificant increase in PLA2 activity. Peritoneal dialysis effluent alone failed to stimulate either PLC or PLD, while pre-incubation with PDE had no affect upon fMLP-induced PLC and PLD activation. However, PDE caused a small but nonsignificant increase in PLA2 activity (which was comparable to that observed with fMLP) and primed the fMLP-induced response. In common with a role for PLA2 and the subsequent release of arachidonic acid (AA), we have demonstrated dose-dependent inhibition of PDE-induced superoxide release by the PLA2 inhibitor mepacrine, as well as activation and priming of the fMLP-induced superoxide generation by AA.ConclusionsThese results imply that PDE-induced NADPH-oxidase activation and priming in human neutrophils is mediated via a PLA2-dependent but PLC and PLD-independent mechanism.
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Affiliation(s)
- Mark A. Lindsay
- Medical Research Centre, City Hospital, Hucknall Road, Nottingham, United Kingdom
| | - Ian Daniels
- Medical Research Centre, City Hospital, Hucknall Road, Nottingham, United Kingdom
| | - John Fletcher
- Medical Research Centre, City Hospital, Hucknall Road, Nottingham, United Kingdom
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Jayasinghe SU, Tankeu AT, Amati F. Reassessing the Role of Diacylglycerols in Insulin Resistance. Trends Endocrinol Metab 2019; 30:618-635. [PMID: 31375395 DOI: 10.1016/j.tem.2019.06.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Revised: 06/26/2019] [Accepted: 06/27/2019] [Indexed: 12/15/2022]
Abstract
Skeletal muscle (SM) insulin resistance (IR) plays an important role in the burden of obesity, particularly because it leads to glucose intolerance and type 2 diabetes. Among the mechanisms thought to link IR to obesity is the accumulation, in muscle cells, of different lipid metabolites. Diacylglycerols (DAGs) are subject of particular attention due to reported interactions with the insulin signaling cascade. Given that SM accounts for the majority of insulin-stimulated glucose uptake, this review integrates recent observational and mechanistic works with the sole focus on questioning the role of DAGs in SM IR. Particular attention is given to the subcellular distributions and specific structures of DAGs, highlighting future research directions towards reaching a consensus on the mechanistic role played by DAGs.
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Affiliation(s)
- Sisitha U Jayasinghe
- Aging and Muscle Metabolism Laboratory, Department of Physiology, University of Lausanne, Lausanne, Switzerland
| | - Aurel T Tankeu
- Aging and Muscle Metabolism Laboratory, Department of Physiology, University of Lausanne, Lausanne, Switzerland
| | - Francesca Amati
- Aging and Muscle Metabolism Laboratory, Department of Physiology, University of Lausanne, Lausanne, Switzerland; Institute of Sports Sciences, University of Lausanne, Lausanne, Switzerland; Service of Endocrinology, Diabetology and Metabolism, Department of Medicine, University Hospital and Lausanne University, Lausanne, Switzerland.
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Snider JM, Luberto C, Hannun YA. Approaches for probing and evaluating mammalian sphingolipid metabolism. Anal Biochem 2019; 575:70-86. [PMID: 30917945 DOI: 10.1016/j.ab.2019.03.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Revised: 03/22/2019] [Accepted: 03/22/2019] [Indexed: 01/02/2023]
Abstract
Sphingolipid metabolism plays a critical role in regulating processes that control cellular fate. This dynamic pathway can generate and degrade the central players: ceramide, sphingosine and sphingosine-1-phosphate in almost any membrane in the cell, adding an unexpected level of complexity in deciphering signaling events. While in vitro assays have been developed for most enzymes in SL metabolism, these assays are setup for optimal activity conditions and can fail to take into account regulatory components such as compartmentalization, substrate limitations, and binding partners that can affect cellular enzymatic activity. Therefore, many in-cell assays have been developed to derive results that are authentic to the cellular situation which may give context to alteration in SL mass. This review will discuss approaches for utilizing probes for mammalian in-cell assays to interrogate most enzymatic steps central to SL metabolism. The use of inhibitors in conjunction with these probes can verify the specificity of cellular assays as well as provide valuable insight into flux in the SL network. The use of inhibitors specific to each of the central sphingolipid enzymes are also discussed to assist researchers in further interrogation of these pathways.
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Affiliation(s)
- Justin M Snider
- Department of Medicine, Stony Brook University, Stony Brook, NY, USA; The Stony Brook Cancer Center, Stony Brook University, Stony Brook, NY, USA
| | - Chiara Luberto
- The Stony Brook Cancer Center, Stony Brook University, Stony Brook, NY, USA; Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY, USA
| | - Yusuf A Hannun
- Department of Medicine, Stony Brook University, Stony Brook, NY, USA; The Stony Brook Cancer Center, Stony Brook University, Stony Brook, NY, USA; Departments of Biochemistry, Pathology and Pharmacology, Stony Brook University, Stony Brook, NY, USA.
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Ganesh BP, Hall A, Ayyaswamy S, Nelson JW, Fultz R, Major A, Haag A, Esparza M, Lugo M, Venable S, Whary M, Fox JG, Versalovic J. Diacylglycerol kinase synthesized by commensal Lactobacillus reuteri diminishes protein kinase C phosphorylation and histamine-mediated signaling in the mammalian intestinal epithelium. Mucosal Immunol 2018; 11:380-393. [PMID: 28745328 PMCID: PMC5785580 DOI: 10.1038/mi.2017.58] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Accepted: 05/21/2017] [Indexed: 02/04/2023]
Abstract
Lactobacillus reuteri 6475 (Lr) of the human microbiome synthesizes histamine and can suppress inflammation via type 2 histamine receptor (H2R) activation in the mammalian intestine. Gut microbes such as Lr promote H2R signaling and may suppress H1R proinflammatory signaling pathways in parallel by unknown mechanisms. In this study, we identified a soluble bacterial enzyme known as diacylglycerol kinase (Dgk) from Lr that is secreted into the extracellular milieu and presumably into the intestinal lumen. DgK diminishes diacylglycerol (DAG) quantities in mammalian cells by promoting its metabolic conversion and causing reduced protein kinase C phosphorylation (pPKC) as a net effect in mammalian cells. We demonstrated that histamine synthesized by gut microbes (Lr) activates both mammalian H1R and H2R, but Lr-derived Dgk suppresses the H1R signaling pathway. Phospho-PKC and IκBα were diminished within the intestinal epithelium of mice and humans treated by wild-type (WT) Lr, but pPKC and IκBα were not decreased in treatment with ΔdgkA Lr. Mucosal IL-6 and systemic interleukin (IL)-1α, eotaxin, and granulocyte colony-stimulating factor (G-CSF) were suppressed in WT Lr, but not in ΔdgkA Lr colonized mice. Collectively, the commensal microbe Lr may act as a "microbial antihistamine" by suppressing intestinal H1R-mediated proinflammatory responses via diminished pPKC-mediated mammalian cell signaling.
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Affiliation(s)
- Bhanu Priya Ganesh
- Departments of Pathology & Immunology, Baylor College of Medicine, Houston, TX, USA
- Department of Pathology, Texas Children’s Hospital, Houston, TX, USA
- Division of Comparative Medicine, Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Anne Hall
- Departments of Pathology & Immunology, Baylor College of Medicine, Houston, TX, USA
- Department of Pathology, Texas Children’s Hospital, Houston, TX, USA
| | - Sriram Ayyaswamy
- Departments of Pathology & Immunology, Baylor College of Medicine, Houston, TX, USA
- Department of Pathology, Texas Children’s Hospital, Houston, TX, USA
| | - James Willard Nelson
- Graduate Program in Integrative Molecular and Biomedical Sciences, Baylor College of Medicine, Houston, TX, USA
| | - Robert Fultz
- Department of Pathology, Texas Children’s Hospital, Houston, TX, USA
- Graduate Program in Integrative Molecular and Biomedical Sciences, Baylor College of Medicine, Houston, TX, USA
| | - Angela Major
- Departments of Pathology & Immunology, Baylor College of Medicine, Houston, TX, USA
- Department of Pathology, Texas Children’s Hospital, Houston, TX, USA
| | - Anthony Haag
- Department of Pathology, Texas Children’s Hospital, Houston, TX, USA
| | - Magdalena Esparza
- Departments of Pathology & Immunology, Baylor College of Medicine, Houston, TX, USA
- Department of Pathology, Texas Children’s Hospital, Houston, TX, USA
| | - Monica Lugo
- Departments of Pathology & Immunology, Baylor College of Medicine, Houston, TX, USA
- Department of Pathology, Texas Children’s Hospital, Houston, TX, USA
| | - Susan Venable
- Departments of Pathology & Immunology, Baylor College of Medicine, Houston, TX, USA
- Department of Pathology, Texas Children’s Hospital, Houston, TX, USA
| | - Mark Whary
- Division of Comparative Medicine, Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - James G. Fox
- Division of Comparative Medicine, Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - James Versalovic
- Departments of Pathology & Immunology, Baylor College of Medicine, Houston, TX, USA
- Department of Pathology, Texas Children’s Hospital, Houston, TX, USA
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Guo A, Chen R, Wang Y, Huang CK, Chen B, Kutschke W, Hong J, Song LS. Transient activation of PKC results in long-lasting detrimental effects on systolic [Ca 2+] i in cardiomyocytes by altering actin cytoskeletal dynamics and T-tubule integrity. J Mol Cell Cardiol 2018; 115:104-114. [PMID: 29307535 DOI: 10.1016/j.yjmcc.2018.01.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Revised: 12/18/2017] [Accepted: 01/03/2018] [Indexed: 11/25/2022]
Abstract
AIMS Protein kinase C (PKC) isozymes contribute to the development of heart failure through dysregulation of Ca2+ handling properties and disruption of contractile function in cardiomyocytes. However, the mechanisms by which PKC activation leads to Ca2+ dysfunction are incompletely understood. METHODS AND RESULTS Shortly upon ventricular pressure overload in mice, we detected transient PKC activation that was associated with pulsed actin cytoskeletal rearrangement. In cultured cardiomyocytes, transient activation of PKC promoted long-term deleterious effects on the integrity of the transverse (T)- tubule system, resulting in a significant decrease in the amplitude and increase in the rising kinetics of Ca2+ transients. Treatment with a PKCα/β inhibitor restored the synchronization of Ca2+ transients and maintained T-tubule integrity in cultured cardiomyocytes. Supporting these data, PKCα/β inhibition protected against T-tubule remodeling and cardiac dysfunction in a mouse model of pressure overload-induced heart failure. Mechanistically, transient activation of PKC resulted in biphasic actin cytoskeletal rearrangement, consistent with in vivo observations in the pressure overloaded mouse model. Transient inhibition of actin polymerization or depolymerization resulted in severe T-tubule damage, recapitulating the T-tubule damage induced by PKC activation. Moreover, inhibition of stretch activated channels (SAC) protected against T-tubule remodeling and E-C coupling dysfunction induced by transient PKC activation and actin cytoskeletal rearrangement. CONCLUSIONS These data identify a key mechanistic link between transient PKC activation and long-term Ca2+ handling defects through PKC-induced actin cytoskeletal rearrangement and resultant T-tubule damage.
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Affiliation(s)
- Ang Guo
- Division of Cardiovascular Medicine, Department of Internal Medicine & Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA; Tongji Hospital, Tongji University School of Medicine, Shanghai 200065, China
| | - Rong Chen
- Division of Cardiovascular Medicine, Department of Internal Medicine & Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA; Shanghai General Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200080, China
| | - Yihui Wang
- Division of Cardiovascular Medicine, Department of Internal Medicine & Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA; Shanghai General Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200080, China
| | - Chun-Kai Huang
- Division of Cardiovascular Medicine, Department of Internal Medicine & Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA; Shanghai General Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200080, China
| | - Biyi Chen
- Division of Cardiovascular Medicine, Department of Internal Medicine & Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA
| | - William Kutschke
- Division of Cardiovascular Medicine, Department of Internal Medicine & Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA
| | - Jiang Hong
- Shanghai General Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200080, China
| | - Long-Sheng Song
- Division of Cardiovascular Medicine, Department of Internal Medicine & Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA; Department of Veterans Affairs Medical Center, Iowa City, IA 52242, USA.
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Hage-Sleiman R, Hamze AB, El-Hed AF, Attieh R, Kozhaya L, Kabbani S, Dbaibo G. Ceramide inhibits PKCθ by regulating its phosphorylation and translocation to lipid rafts in Jurkat cells. Immunol Res 2017; 64:869-86. [PMID: 26798039 DOI: 10.1007/s12026-016-8787-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Protein kinase C theta (PKCθ) is a novel, calcium-independent member of the PKC family of kinases that was identified as a central player in T cell signaling and proliferation. Upon T cell activation by antigen-presenting cells, PKCθ gets phosphorylated and activated prior to its translocation to the immunological synapse where it couples with downstream effectors. PKCθ may be regulated by ceramide, a crucial sphingolipid that is known to promote differentiation, growth arrest, and apoptosis. To further investigate the mechanism, we stimulated human Jurkat T cells with either PMA or anti-CD3/anti-CD28 antibodies following induction of ceramide accumulation by adding exogenous ceramide, bacterial sphingomyelinase, or Fas ligation. Our results suggest that ceramide regulates the PKCθ pathway through preventing its critical threonine 538 (Thr538) phosphorylation and subsequent activation, thereby inhibiting the kinase's translocation to lipid rafts. Moreover, this inhibition is not likely to be a generic effect of ceramide on membrane reorganization. Other lipids, namely dihydroceramide, palmitate, and sphingosine, did not produce similar effects on PKCθ. Addition of the phosphatase inhibitors okadaic acid and calyculin A reversed the inhibition exerted by ceramide, and this suggests involvement of a ceramide-activated protein phosphatase. Such previously undescribed mechanism of regulation of PKCθ raises the possibility that ceramide, or one of its derivatives, and may prove valuable in novel therapeutic approaches for disorders involving autoimmunity or excessive inflammation-where PKCθ plays a critical role.
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Affiliation(s)
- Rouba Hage-Sleiman
- Department of Biology, Faculty of Sciences, Lebanese University, Hadath, Lebanon
| | - Asmaa B Hamze
- Department of Biomedical Science, Faculty of Health Sciences, Global University, Batrakiyye, Beirut, Lebanon
| | - Aimée F El-Hed
- Department of Pediatrics and Adolescent Medicine, Center for Infectious Diseases Research, Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, PO Box 11-0236 Riad El Solh, Beirut, Lebanon
| | - Randa Attieh
- Department of Pediatrics and Adolescent Medicine, Center for Infectious Diseases Research, Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, PO Box 11-0236 Riad El Solh, Beirut, Lebanon
| | - Lina Kozhaya
- Department of Pediatrics and Adolescent Medicine, Center for Infectious Diseases Research, Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, PO Box 11-0236 Riad El Solh, Beirut, Lebanon
| | - Sarah Kabbani
- Department of Pediatrics and Adolescent Medicine, Center for Infectious Diseases Research, Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, PO Box 11-0236 Riad El Solh, Beirut, Lebanon
| | - Ghassan Dbaibo
- Department of Pediatrics and Adolescent Medicine, Center for Infectious Diseases Research, Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, PO Box 11-0236 Riad El Solh, Beirut, Lebanon.
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Combining NMR Spectroscopy and Molecular Dynamics Simulation to Investigate the Structure and Dynamics of Membrane-Associated Proteins. SPRINGER SERIES IN BIOPHYSICS 2017. [DOI: 10.1007/978-3-319-66601-3_14] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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13
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Ribas V, Drew BG, Zhou Z, Phun J, Kalajian NY, Soleymani T, Daraei P, Widjaja K, Wanagat J, de Aguiar Vallim TQ, Fluitt AH, Bensinger S, Le T, Radu C, Whitelegge JP, Beaven SW, Tontonoz P, Lusis AJ, Parks BW, Vergnes L, Reue K, Singh H, Bopassa JC, Toro L, Stefani E, Watt MJ, Schenk S, Akerstrom T, Kelly M, Pedersen BK, Hewitt SC, Korach KS, Hevener AL. Skeletal muscle action of estrogen receptor α is critical for the maintenance of mitochondrial function and metabolic homeostasis in females. Sci Transl Med 2016; 8:334ra54. [PMID: 27075628 DOI: 10.1126/scitranslmed.aad3815] [Citation(s) in RCA: 161] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Accepted: 02/28/2016] [Indexed: 12/12/2022]
Abstract
Impaired estrogen receptor α (ERα) action promotes obesity and metabolic dysfunction in humans and mice; however, the mechanisms underlying these phenotypes remain unknown. Considering that skeletal muscle is a primary tissue responsible for glucose disposal and oxidative metabolism, we established that reduced ERα expression in muscle is associated with glucose intolerance and adiposity in women and female mice. To test this relationship, we generated muscle-specific ERα knockout (MERKO) mice. Impaired glucose homeostasis and increased adiposity were paralleled by diminished muscle oxidative metabolism and bioactive lipid accumulation in MERKO mice. Aberrant mitochondrial morphology, overproduction of reactive oxygen species, and impairment in basal and stress-induced mitochondrial fission dynamics, driven by imbalanced protein kinase A-regulator of calcineurin 1-calcineurin signaling through dynamin-related protein 1, tracked with reduced oxidative metabolism in MERKO muscle. Although muscle mitochondrial DNA (mtDNA) abundance was similar between the genotypes, ERα deficiency diminished mtDNA turnover by a balanced reduction in mtDNA replication and degradation. Our findings indicate the retention of dysfunctional mitochondria in MERKO muscle and implicate ERα in the preservation of mitochondrial health and insulin sensitivity as a defense against metabolic disease in women.
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Affiliation(s)
- Vicent Ribas
- Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, David Geffen School of Medicine at University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA
| | - Brian G Drew
- Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, David Geffen School of Medicine at University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA
| | - Zhenqi Zhou
- Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, David Geffen School of Medicine at University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA
| | - Jennifer Phun
- Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, David Geffen School of Medicine at University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA
| | - Nareg Y Kalajian
- Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, David Geffen School of Medicine at University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA
| | - Teo Soleymani
- Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, David Geffen School of Medicine at University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA
| | - Pedram Daraei
- Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, David Geffen School of Medicine at University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA
| | - Kevin Widjaja
- Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, David Geffen School of Medicine at University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA
| | - Jonathan Wanagat
- Division of Geriatrics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | | | - Amy H Fluitt
- Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, David Geffen School of Medicine at University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA. Department of Molecular and Medical Pharmacology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Steven Bensinger
- Department of Molecular and Medical Pharmacology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Thuc Le
- Department of Molecular and Medical Pharmacology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA. Ahmanson Translational Imaging Division, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Caius Radu
- Department of Molecular and Medical Pharmacology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA. Ahmanson Translational Imaging Division, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Julian P Whitelegge
- Pasarow Mass Spectrometry Laboratory and Neuropsychiatric Institute-Semel Institute for Neuroscience & Human Behavior, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Simon W Beaven
- Howard Hughes Medical Institute and Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Peter Tontonoz
- Howard Hughes Medical Institute and Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Aldons J Lusis
- Division of Cardiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA. Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Brian W Parks
- Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Laurent Vergnes
- Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Karen Reue
- Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Harpreet Singh
- Department of Anesthesiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Jean C Bopassa
- Department of Anesthesiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Ligia Toro
- Department of Anesthesiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Enrico Stefani
- Department of Anesthesiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Matthew J Watt
- Department of Physiology, Monash University, Clayton, Victoria 3800, Australia
| | - Simon Schenk
- Department of Orthopaedic Surgery, University of California, San Diego, La Jolla, CA 92093, USA
| | - Thorbjorn Akerstrom
- Centre of Inflammation and Metabolism and Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen 2200, Denmark
| | - Meghan Kelly
- Centre of Inflammation and Metabolism and Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen 2200, Denmark
| | - Bente K Pedersen
- Centre of Inflammation and Metabolism and Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen 2200, Denmark
| | - Sylvia C Hewitt
- Receptor Biology Section, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, Durham, NC 27709, USA
| | - Kenneth S Korach
- Receptor Biology Section, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, Durham, NC 27709, USA
| | - Andrea L Hevener
- Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, David Geffen School of Medicine at University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA. UCLA Iris Cantor Women's Health Research Center, Los Angeles, CA 90095, USA.
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Marcinko K, Sikkema SR, Samaan MC, Kemp BE, Fullerton MD, Steinberg GR. High intensity interval training improves liver and adipose tissue insulin sensitivity. Mol Metab 2015; 4:903-15. [PMID: 26909307 PMCID: PMC4731736 DOI: 10.1016/j.molmet.2015.09.006] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Revised: 09/11/2015] [Accepted: 09/18/2015] [Indexed: 12/13/2022] Open
Abstract
Objective Endurance exercise training reduces insulin resistance, adipose tissue inflammation and non-alcoholic fatty liver disease (NAFLD), an effect often associated with modest weight loss. Recent studies have indicated that high-intensity interval training (HIIT) lowers blood glucose in individuals with type 2 diabetes independently of weight loss; however, the organs affected and mechanisms mediating the glucose lowering effects are not known. Intense exercise increases phosphorylation and inhibition of acetyl-CoA carboxylase (ACC) by AMP-activated protein kinase (AMPK) in muscle, adipose tissue and liver. AMPK and ACC are key enzymes regulating fatty acid metabolism, liver fat content, adipose tissue inflammation and insulin sensitivity but the importance of this pathway in regulating insulin sensitivity with HIIT is unknown. Methods In the current study, the effects of 6 weeks of HIIT were examined using obese mice with serine–alanine knock-in mutations on the AMPK phosphorylation sites of ACC1 and ACC2 (AccDKI) or wild-type (WT) controls. Results HIIT lowered blood glucose and increased exercise capacity, food intake, basal activity levels, carbohydrate oxidation and liver and adipose tissue insulin sensitivity in HFD-fed WT and AccDKI mice. These changes occurred independently of weight loss or reductions in adiposity, inflammation and liver lipid content. Conclusions These data indicate that HIIT lowers blood glucose levels by improving adipose and liver insulin sensitivity independently of changes in adiposity, adipose tissue inflammation, liver lipid content or AMPK phosphorylation of ACC. High-intensity interval training (HIIT) improves exercise capacity and whole-body glucose homeostasis. HIIT enhances liver and adipose tissue insulin sensitivity independent of body weight and adiposity. HIIT does not change adipose tissue cell size, macrophage infiltration, inflammation and liver lipid content. HIIT exercise training improves insulin sensitivity independently of the AMPK-ACC signaling pathway.
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Affiliation(s)
- Katarina Marcinko
- Division of Endocrinology and Metabolism, Department of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Sarah R Sikkema
- Division of Endocrinology and Metabolism, Department of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - M Constantine Samaan
- Division of Pediatric Endocrinology, Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada
| | - Bruce E Kemp
- Protein Chemistry and Metabolism, St Vincent's Institute and Department of Medicine, University of Melbourne, 41 Victoria Parade, Fitzroy, Victoria 3065, Australia
| | - Morgan D Fullerton
- Division of Endocrinology and Metabolism, Department of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Gregory R Steinberg
- Division of Endocrinology and Metabolism, Department of Medicine, McMaster University, Hamilton, Ontario, Canada; Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
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15
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Selathurai A, Kowalski GM, Burch ML, Sepulveda P, Risis S, Lee-Young RS, Lamon S, Meikle PJ, Genders AJ, McGee SL, Watt MJ, Russell AP, Frank M, Jackowski S, Febbraio MA, Bruce CR. The CDP-Ethanolamine Pathway Regulates Skeletal Muscle Diacylglycerol Content and Mitochondrial Biogenesis without Altering Insulin Sensitivity. Cell Metab 2015; 21:718-30. [PMID: 25955207 DOI: 10.1016/j.cmet.2015.04.001] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Revised: 02/20/2015] [Accepted: 03/28/2015] [Indexed: 01/20/2023]
Abstract
Accumulation of diacylglycerol (DG) in muscle is thought to cause insulin resistance. DG is a precursor for phospholipids, thus phospholipid synthesis could be involved in regulating muscle DG. Little is known about the interaction between phospholipid and DG in muscle; therefore, we examined whether disrupting muscle phospholipid synthesis, specifically phosphatidylethanolamine (PtdEtn), would influence muscle DG content and insulin sensitivity. Muscle PtdEtn synthesis was disrupted by deleting CTP:phosphoethanolamine cytidylyltransferase (ECT), the rate-limiting enzyme in the CDP-ethanolamine pathway, a major route for PtdEtn production. While PtdEtn was reduced in muscle-specific ECT knockout mice, intramyocellular and membrane-associated DG was markedly increased. Importantly, however, this was not associated with insulin resistance. Unexpectedly, mitochondrial biogenesis and muscle oxidative capacity were increased in muscle-specific ECT knockout mice and were accompanied by enhanced exercise performance. These findings highlight the importance of the CDP-ethanolamine pathway in regulating muscle DG content and challenge the DG-induced insulin resistance hypothesis.
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Affiliation(s)
- Ahrathy Selathurai
- Centre for Physical Activity and Nutrition (C-PAN) Research, School of Exercise and Nutrition Sciences, Deakin University, Burwood, 3125 VIC, Australia
| | - Greg M Kowalski
- Centre for Physical Activity and Nutrition (C-PAN) Research, School of Exercise and Nutrition Sciences, Deakin University, Burwood, 3125 VIC, Australia
| | - Micah L Burch
- Department of Physiology, Monash University, Clayton, 3800 VIC, Australia
| | - Patricio Sepulveda
- Department of Physiology, Monash University, Clayton, 3800 VIC, Australia
| | - Steve Risis
- Cellular and Molecular Metabolism Laboratory, Baker IDI Heart and Diabetes Institute, Prahran, 3004 VIC, Australia
| | - Robert S Lee-Young
- Cellular and Molecular Metabolism Laboratory, Baker IDI Heart and Diabetes Institute, Prahran, 3004 VIC, Australia
| | - Severine Lamon
- Centre for Physical Activity and Nutrition (C-PAN) Research, School of Exercise and Nutrition Sciences, Deakin University, Burwood, 3125 VIC, Australia
| | - Peter J Meikle
- Metabolomics Laboratory, Baker IDI Heart and Diabetes Institute, Prahran, 3004 VIC, Australia
| | - Amanda J Genders
- Metabolic Research Unit, Deakin University, Waurn Ponds, 3216 VIC, Australia
| | - Sean L McGee
- Metabolic Research Unit, Deakin University, Waurn Ponds, 3216 VIC, Australia
| | - Matthew J Watt
- Department of Physiology, Monash University, Clayton, 3800 VIC, Australia
| | - Aaron P Russell
- Centre for Physical Activity and Nutrition (C-PAN) Research, School of Exercise and Nutrition Sciences, Deakin University, Burwood, 3125 VIC, Australia
| | - Matthew Frank
- Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Suzanne Jackowski
- Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Mark A Febbraio
- Cellular and Molecular Metabolism Laboratory, Baker IDI Heart and Diabetes Institute, Prahran, 3004 VIC, Australia
| | - Clinton R Bruce
- Centre for Physical Activity and Nutrition (C-PAN) Research, School of Exercise and Nutrition Sciences, Deakin University, Burwood, 3125 VIC, Australia.
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16
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HPLC separation and ultrasensitive optical quantification of ceramide species applying 7-(diethylamino)coumarin-3-carbonyl azide derivatisation. J Chromatogr B Analyt Technol Biomed Life Sci 2015; 986-987:123-8. [PMID: 25728369 DOI: 10.1016/j.jchromb.2015.02.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Revised: 02/08/2015] [Accepted: 02/09/2015] [Indexed: 11/24/2022]
Abstract
Ceramides are derivatised using 7-(diethylamino)coumarin-3-carbonyl azide; subsequent gradient HPLC separation allows sensitive optical quantification of individual cellular ceramides. Compared to 9-anthracenecarbonyl cyanide (9-anthroyl nitrile) as derivatisation agent, the limit of detection could be improved 415-fold, respectively 10,000-fold (detection limit 0.6 pmol labelled ceramide/sample) when compared to benzoyl chloride-labelling. Acidic or alkaline catalysts are not required, enabling drying and storing of the labelled samples and a free choice of solvents for subsequent HPLC-separation. The quantitative method is characterised by high sensitivity, linearity and robustness in the pico- to nanomolar concentration range and does not require mass-spectrometry for quantification of cellular ceramides.
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Overexpression of sphingosine kinase 1 in liver reduces triglyceride content in mice fed a low but not high-fat diet. Biochim Biophys Acta Mol Cell Biol Lipids 2014; 1851:210-9. [PMID: 25490466 DOI: 10.1016/j.bbalip.2014.12.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Revised: 11/11/2014] [Accepted: 12/01/2014] [Indexed: 11/23/2022]
Abstract
Hepatic insulin resistance is a major risk factor for the development of type 2 diabetes and is associated with the accumulation of lipids, including diacylglycerol (DAG), triacylglycerols (TAG) and ceramide. There is evidence that enzymes involved in ceramide or sphingolipid metabolism may have a role in regulating concentrations of glycerolipids such as DAG and TAG. Here we have investigated the role of sphingosine kinase (SphK) in regulating hepatic lipid levels. We show that mice on a high-fat high-sucrose diet (HFHS) displayed glucose intolerance, elevated liver TAG and DAG, and a reduction in total hepatic SphK activity. Reduced SphK activity correlated with downregulation of SphK1, but not SphK2 expression, and was not associated with altered ceramide levels. The role of SphK1 was further investigated by overexpressing this isoform in the liver of mice in vivo. On a low-fat diet (LFD) mice overexpressing liver SphK1, displayed reduced hepatic TAG synthesis and total TAG levels, but with no change to DAG or ceramide. These mice also exhibited no change in gluconeogenesis, glycogenolysis or glucose tolerance. Similarly, overexpression of SphK1 had no effect on the pattern of endogenous glucose production determined during a glucose tolerance test. Under HFHS conditions, normalization of liver SphK activity to levels observed in LFD controls did not alter hepatic TAG concentrations. Furthermore, DAG, ceramide and glucose tolerance were also unaffected. In conclusion, our data suggest that SphK1 plays an important role in regulating TAG metabolism under LFD conditions.
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18
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Egea-Jiménez AL, Corbalán-García S, Gómez-Fernández JC. The C1B domains of novel PKCε and PKCη have a higher membrane binding affinity than those of the also novel PKCδ and PKCθ. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:1898-909. [DOI: 10.1016/j.bbamem.2014.04.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Revised: 03/28/2014] [Accepted: 04/02/2014] [Indexed: 10/25/2022]
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Drew BG, Ribas V, Le JA, Henstridge DC, Phun J, Zhou Z, Soleymani T, Daraei P, Sitz D, Vergnes L, Wanagat J, Reue K, Febbraio MA, Hevener AL. HSP72 is a mitochondrial stress sensor critical for Parkin action, oxidative metabolism, and insulin sensitivity in skeletal muscle. Diabetes 2014; 63:1488-505. [PMID: 24379352 PMCID: PMC3994950 DOI: 10.2337/db13-0665] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Increased heat shock protein (HSP) 72 expression in skeletal muscle prevents obesity and glucose intolerance in mice, although the underlying mechanisms of this observation are largely unresolved. Herein we show that HSP72 is a critical regulator of stress-induced mitochondrial triage signaling since Parkin, an E3 ubiquitin ligase known to regulate mitophagy, was unable to ubiquitinate and control its own protein expression or that of its central target mitofusin (Mfn) in the absence of HSP72. In wild-type cells, we show that HSP72 rapidly translocates to depolarized mitochondria prior to Parkin recruitment and immunoprecipitates with both Parkin and Mfn2 only after specific mitochondrial insult. In HSP72 knockout mice, impaired Parkin action was associated with retention of enlarged, dysmorphic mitochondria and paralleled by reduced muscle respiratory capacity, lipid accumulation, and muscle insulin resistance. Reduced oxygen consumption and impaired insulin action were recapitulated in Parkin-null myotubes, confirming a role for the HSP72-Parkin axis in the regulation of muscle insulin sensitivity. These data suggest that strategies to maintain HSP72 may provide therapeutic benefit to enhance mitochondrial quality and insulin action to ameliorate complications associated with metabolic diseases, including type 2 diabetes.
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Affiliation(s)
- Brian G. Drew
- David Geffen School of Medicine, Department of Medicine, Division of Endocrinology, Diabetes and Hypertension, University of California, Los Angeles, Los Angeles, CA
| | - Vicente Ribas
- David Geffen School of Medicine, Department of Medicine, Division of Endocrinology, Diabetes and Hypertension, University of California, Los Angeles, Los Angeles, CA
| | - Jamie A. Le
- David Geffen School of Medicine, Department of Medicine, Division of Endocrinology, Diabetes and Hypertension, University of California, Los Angeles, Los Angeles, CA
| | | | - Jennifer Phun
- David Geffen School of Medicine, Department of Medicine, Division of Endocrinology, Diabetes and Hypertension, University of California, Los Angeles, Los Angeles, CA
| | - Zhenqi Zhou
- David Geffen School of Medicine, Department of Medicine, Division of Endocrinology, Diabetes and Hypertension, University of California, Los Angeles, Los Angeles, CA
| | - Teo Soleymani
- David Geffen School of Medicine, Department of Medicine, Division of Endocrinology, Diabetes and Hypertension, University of California, Los Angeles, Los Angeles, CA
| | - Pedram Daraei
- David Geffen School of Medicine, Department of Medicine, Division of Endocrinology, Diabetes and Hypertension, University of California, Los Angeles, Los Angeles, CA
| | - Daniel Sitz
- David Geffen School of Medicine, Department of Medicine, Division of Endocrinology, Diabetes and Hypertension, University of California, Los Angeles, Los Angeles, CA
| | - Laurent Vergnes
- David Geffen School of Medicine, Department of Human Genetics, University of California, Los Angeles, Los Angeles, CA
| | - Jonathan Wanagat
- David Geffen School of Medicine, Department of Medicine, Division of Geriatrics, University of California, Los Angeles, Los Angeles, CA
| | - Karen Reue
- David Geffen School of Medicine, Department of Human Genetics, University of California, Los Angeles, Los Angeles, CA
| | - Mark A. Febbraio
- Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia
| | - Andrea L. Hevener
- David Geffen School of Medicine, Department of Medicine, Division of Endocrinology, Diabetes and Hypertension, University of California, Los Angeles, Los Angeles, CA
- Corresponding author: Andrea L. Hevener,
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Zachariah Tom R, Garcia-Roves PM, Sjögren RJO, Jiang LQ, Holmström MH, Deshmukh AS, Vieira E, Chibalin AV, Björnholm M, Zierath JR. Effects of AMPK activation on insulin sensitivity and metabolism in leptin-deficient ob/ob mice. Diabetes 2014; 63:1560-71. [PMID: 24487023 DOI: 10.2337/db13-0670] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
AMP-activated protein kinase (AMPK) is a heterotrimeric complex, composed of a catalytic subunit (α) and two regulatory subunits (β and γ), which act as a metabolic sensor to regulate glucose and lipid metabolism. A mutation in the γ3 subunit (AMPKγ3(R225Q)) increases basal AMPK phosphorylation, while concomitantly reducing sensitivity to AMP. AMPKγ3(R225Q) (γ3(R225Q)) transgenic mice are protected against dietary-induced triglyceride accumulation and insulin resistance. We determined whether skeletal muscle-specific expression of AMPKγ3(R225Q) prevents metabolic abnormalities in leptin-deficient ob/ob (ob/ob-γ3(R225Q)) mice. Glycogen content was increased, triglyceride content was decreased, and diacylglycerol and ceramide content were unaltered in gastrocnemius muscle from ob/ob-γ3(R225Q) mice, whereas glucose tolerance was unaltered. Insulin-stimulated glucose uptake in extensor digitorum longus muscle during the euglycemic-hyperinsulinemic clamp was increased in lean γ3(R225Q) mice, but not in ob/ob-γ3(R225Q) mice. Acetyl-CoA carboxylase phosphorylation was increased in gastrocnemius muscle from γ3(R225Q) mutant mice independent of adiposity. Glycogen and triglyceride content were decreased after leptin treatment (5 days) in ob/ob mice, but not in ob/ob-γ3(R225Q) mice. In conclusion, metabolic improvements arising from muscle-specific expression of AMPKγ3(R225Q) are insufficient to ameliorate insulin resistance and obesity in leptin-deficient mice. Central defects due to leptin deficiency may override any metabolic benefit conferred by peripheral overexpression of the AMPKγ3(R225Q) mutation.
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Affiliation(s)
- Robby Zachariah Tom
- Integrative Physiology, Department of Molecular Medicine and Surgery, Karolinska Institutet, SE-171 77 Stockholm, Sweden
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Baldanzi G. Inhibition of diacylglycerol kinases as a physiological way to promote diacylglycerol signaling. Adv Biol Regul 2014; 55:39-49. [PMID: 24582387 DOI: 10.1016/j.jbior.2014.02.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2013] [Revised: 01/02/2014] [Accepted: 02/02/2014] [Indexed: 01/12/2023]
Abstract
Diacylglycerol is a key regulator of cell physiology, controlling the membrane recruitment and activation of signaling molecules. Accordingly, diacylglycerol generation and metabolism are strictly controlled, allowing for localized regulation of its concentration. While the increased production of diacylglycerol upon receptor triggering is well recognized, the modulation of diacylglycerol metabolism by diacylglycerol kinases (DGKs) is less characterized. Some agonists induce DGK activation and recruitment to the plasma membrane, promoting diacylglycerol metabolism to phosphatidic acid. Conversely, several reports indicate that signaling pathways that selectively inhibits DGK isoforms can enhance cellular diacylglycerol levels and signal transduction. For example, the impairment of DGKθ activity by RhoA binding to the catalytic domain represents a conserved mechanism controlling diacylglycerol signaling from Caenorhabditis elegans motoneurons to mammalian hepatocytes. Similarly, DGKα activity is inhibited in lymphocytes by TCR signaling, thus contributing to a rise in diacylglycerol concentration for downstream signaling. Finally, DGKμ activity is inhibited by ischemia-reperfusion-generated reactive oxygen species in airway endothelial cells, promoting diacylglycerol-mediated ion channel opening and edema. In those systems, DGKs provide a gatekeeper function by blunting diacylglycerol levels or possibly establishing permissive domains for diacylglycerol signaling. In this review, I discuss the possible general relevance of DGK inhibition to enhanced diacylglycerol signaling.
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Affiliation(s)
- Gianluca Baldanzi
- University "A. Avogadro" del Piemonte Orientale, Department of Translational Medicine, via Solaroli 17, 28100 Novara, Italy.
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22
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Wang M, Hayakawa J, Yang K, Han X. Characterization and quantification of diacylglycerol species in biological extracts after one-step derivatization: a shotgun lipidomics approach. Anal Chem 2014; 86:2146-55. [PMID: 24432906 DOI: 10.1021/ac403798q] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Diacylglycerols (DAGs) are important intermediates of lipid metabolism and cellular signaling. It is well-known that the mass levels of DAG are altered under disease states. Therefore, quantitative analysis of DAGs in biological samples can provide critical information to uncover underlying mechanisms of various cellular functional disorders. Although great efforts on the analysis of individual DAG species have recently been made by utilizing mass spectrometry with or without derivatization, cost-effective and high throughput methodologies for identification and quantification of all DAG species including regioisomers, particularly in an approach of shotgun lipidomics, are still missing. Herein, we described a novel method for directly identifying and quantifying DAG species including regioisomers present in lipid extracts of biological samples after facile one-step derivatization with dimethylglycine based on the principles of multidimensional mass spectrometry-based shotgun lipidomics. The established method provided substantial sensitivity (low limit of quantification at amol/μL), high specificity, and broad linear dynamics range (2500-fold) without matrix effects. By exploiting this novel method, we revealed a 16-fold increase of total DAG mass in the livers of ob/ob mice compared to their wild type controls at 4 months of age (an insulin-resistant state) versus a 5-fold difference between 3 month old mice (with normal insulin). These results demonstrated the importance and power of the method for studying biochemical mechanisms underpinning disease states.
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Affiliation(s)
- Miao Wang
- Diabetes and Obesity Research Center, Sanford-Burnham Medical Research Institute, Orlando, FL 32827
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23
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Fullerton MD, Galic S, Marcinko K, Sikkema S, Pulinilkunnil T, Chen Z, O’Neill HM, Ford RJ, Palanivel R, O’Brien M, Hardie DG, Macaulay SL, Schertzer JD, Dyck JRB, van Denderen BJ, Kemp BE, Steinberg GR. Single phosphorylation sites in Acc1 and Acc2 regulate lipid homeostasis and the insulin-sensitizing effects of metformin. Nat Med 2013; 19:1649-54. [PMID: 24185692 PMCID: PMC4965268 DOI: 10.1038/nm.3372] [Citation(s) in RCA: 610] [Impact Index Per Article: 55.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Accepted: 09/11/2013] [Indexed: 12/15/2022]
Abstract
The obesity epidemic has led to an increased incidence of nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes. AMP-activated protein kinase (Ampk) regulates energy homeostasis and is activated by cellular stress, hormones and the widely prescribed type 2 diabetes drug metformin. Ampk phosphorylates mouse acetyl-CoA carboxylase 1 (Acc1; refs. 3,4) at Ser79 and Acc2 at Ser212, inhibiting the conversion of acetyl-CoA to malonyl-CoA. The latter metabolite is a precursor in fatty acid synthesis and an allosteric inhibitor of fatty acid transport into mitochondria for oxidation. To test the physiological impact of these phosphorylation events, we generated mice with alanine knock-in mutations in both Acc1 (at Ser79) and Acc2 (at Ser212) (Acc double knock-in, AccDKI). Compared to wild-type mice, these mice have elevated lipogenesis and lower fatty acid oxidation, which contribute to the progression of insulin resistance, glucose intolerance and NAFLD, but not obesity. Notably, AccDKI mice made obese by high-fat feeding are refractory to the lipid-lowering and insulin-sensitizing effects of metformin. These findings establish that inhibitory phosphorylation of Acc by Ampk is essential for the control of lipid metabolism and, in the setting of obesity, for metformin-induced improvements in insulin action.
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Affiliation(s)
- Morgan D. Fullerton
- Division of Endocrinology and Metabolism, Department of Medicine, McMaster University, 1280 Main St. W., Hamilton, Ontario, Canada L8N 3Z5
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1280 Main St. W., Hamilton, Ontario, Canada L8N 3Z5
| | - Sandra Galic
- St. Vincent’s Institute of Medical Research and Department of Medicine, University of Melbourne, 41 Victoria Parade, Fitzroy, Vic 3065, Australia
| | - Katarina Marcinko
- Division of Endocrinology and Metabolism, Department of Medicine, McMaster University, 1280 Main St. W., Hamilton, Ontario, Canada L8N 3Z5
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1280 Main St. W., Hamilton, Ontario, Canada L8N 3Z5
| | - Sarah Sikkema
- Division of Endocrinology and Metabolism, Department of Medicine, McMaster University, 1280 Main St. W., Hamilton, Ontario, Canada L8N 3Z5
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1280 Main St. W., Hamilton, Ontario, Canada L8N 3Z5
| | - Thomas Pulinilkunnil
- Cardiovascular Research Centre, Mazankowski Alberta Heart Institute, Department of Pediatrics, Faculty of Medicine and Dentistry, University of Alberta, T6G 2S2 Edmonton, Alberta, Canada
| | - Zhi–Ping Chen
- St. Vincent’s Institute of Medical Research and Department of Medicine, University of Melbourne, 41 Victoria Parade, Fitzroy, Vic 3065, Australia
| | - Hayley M. O’Neill
- Division of Endocrinology and Metabolism, Department of Medicine, McMaster University, 1280 Main St. W., Hamilton, Ontario, Canada L8N 3Z5
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1280 Main St. W., Hamilton, Ontario, Canada L8N 3Z5
- St. Vincent’s Institute of Medical Research and Department of Medicine, University of Melbourne, 41 Victoria Parade, Fitzroy, Vic 3065, Australia
| | - Rebecca J. Ford
- Division of Endocrinology and Metabolism, Department of Medicine, McMaster University, 1280 Main St. W., Hamilton, Ontario, Canada L8N 3Z5
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1280 Main St. W., Hamilton, Ontario, Canada L8N 3Z5
| | - Rengasamy Palanivel
- Division of Endocrinology and Metabolism, Department of Medicine, McMaster University, 1280 Main St. W., Hamilton, Ontario, Canada L8N 3Z5
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1280 Main St. W., Hamilton, Ontario, Canada L8N 3Z5
| | - Matthew O’Brien
- St. Vincent’s Institute of Medical Research and Department of Medicine, University of Melbourne, 41 Victoria Parade, Fitzroy, Vic 3065, Australia
| | - D. Grahame Hardie
- Division of Cell Signaling & Immunology, College of Life Sciences, University of Dundee, Dundee, DD1 5EH, Scotland, UK
| | - S. Lance Macaulay
- CSIRO Preventative Health Flagship, Materials Science and Engineering, Parkville, Vic 3052, Australia
| | - Jonathan D. Schertzer
- Division of Endocrinology and Metabolism, Department of Medicine, McMaster University, 1280 Main St. W., Hamilton, Ontario, Canada L8N 3Z5
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1280 Main St. W., Hamilton, Ontario, Canada L8N 3Z5
- Department of Pediatrics, McMaster University, 1280 Main St. W., Hamilton, Ontario, Canada L8N 3Z5
| | - Jason R. B. Dyck
- Cardiovascular Research Centre, Mazankowski Alberta Heart Institute, Department of Pediatrics, Faculty of Medicine and Dentistry, University of Alberta, T6G 2S2 Edmonton, Alberta, Canada
| | - Bryce J. van Denderen
- St. Vincent’s Institute of Medical Research and Department of Medicine, University of Melbourne, 41 Victoria Parade, Fitzroy, Vic 3065, Australia
| | - Bruce E. Kemp
- St. Vincent’s Institute of Medical Research and Department of Medicine, University of Melbourne, 41 Victoria Parade, Fitzroy, Vic 3065, Australia
| | - Gregory R. Steinberg
- Division of Endocrinology and Metabolism, Department of Medicine, McMaster University, 1280 Main St. W., Hamilton, Ontario, Canada L8N 3Z5
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1280 Main St. W., Hamilton, Ontario, Canada L8N 3Z5
- St. Vincent’s Institute of Medical Research and Department of Medicine, University of Melbourne, 41 Victoria Parade, Fitzroy, Vic 3065, Australia
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Boldyrev IA, Brown RE, Molotkovsky JG. An Expedient Synthesis of Fluorescent Labeled Ceramide-1-phosphate Analogues. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2013; 39:539-542. [PMID: 27429541 PMCID: PMC4943763 DOI: 10.1134/s106816201305004x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A synthesis for fluorescent analogs of ceramide-1-phosphate bearing 9-anthrylvinyl or 4,4-difluoro-3a,4a-diaza-s-indacene-8-yl (Me4-BODIPY) fluorophore at co-position of fatty acid residue was carried out. The key stage of the synthesis is hydrolysis of corresponding sphingomyelins catalyzed by phospholipase D from Streptomyces chromofuscus; the enzymatic yield has been raised to 50-70% by appliance of organic solvent in the incubation medium.
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Affiliation(s)
- I. A. Boldyrev
- Shemyakin–Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, Moscow, 117997 Russian
| | - R. E. Brown
- Hormel Institute, University of Minnesota, Austin, MN 55912 USA
| | - J. G. Molotkovsky
- Shemyakin–Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, Moscow, 117997 Russian
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25
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Egea-Jiménez AL, Pérez-Lara Á, Corbalán-García S, Gómez-Fernández JC. Phosphatidylinositol 4,5-bisphosphate decreases the concentration of Ca2+, phosphatidylserine and diacylglycerol required for protein kinase C α to reach maximum activity. PLoS One 2013; 8:e69041. [PMID: 23874859 PMCID: PMC3707892 DOI: 10.1371/journal.pone.0069041] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Accepted: 06/05/2013] [Indexed: 11/18/2022] Open
Abstract
The C2 domain of PKCα possesses two different binding sites, one for Ca(2+) and phosphatidylserine and a second one that binds PIP2 with very high affinity. The enzymatic activity of PKCα was studied by activating it with large unilamellar lipid vesicles, varying the concentration of Ca(2+) and the contents of dioleylglycerol (DOG), phosphatidylinositol 4,5-bisphosphate (PIP2) and phosphadidylserine (POPS) in these model membranes. The results showed that PIP2 increased the Vmax of PKCα and, when the PIP2 concentration was 5 mol% of the total lipid in the membrane, the addition of 2 mol% of DOG did not increase the activity. In addition PIP2 decreases K0.5 of Ca(2+) more than 3-fold, that of DOG almost 5-fold and that of POPS by a half. The K0.5 values of PIP2 amounted to only 0.11 µM in the presence of DOG and 0.39 in its absence, which is within the expected physiological range for the inner monolayer of a mammalian plasma membrane. As a consequence, PKCα may be expected to operate near its maximum capacity even in the absence of a cell signal producing diacylglycerol. Nevertheless, we have shown that the presence of DOG may also help, since the K0.5 for PIP2 notably decreases in its presence. Taken together, these results underline the great importance of PIP2 in the activation of PKCα and demonstrate that in its presence, the most important cell signal for triggering the activity of this enzyme is the increase in the concentration of cytoplasmic Ca(2+).
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Affiliation(s)
- Antonio L. Egea-Jiménez
- Departamento de Bioquímica y Biología Molecular-A, Facultad de Veterinaria, Regional Campus of International Excellence "Campus Mare Nostrum", Universidad de Murcia, Murcia, Spain
| | - Ángel Pérez-Lara
- Departamento de Bioquímica y Biología Molecular-A, Facultad de Veterinaria, Regional Campus of International Excellence "Campus Mare Nostrum", Universidad de Murcia, Murcia, Spain
| | - Senena Corbalán-García
- Departamento de Bioquímica y Biología Molecular-A, Facultad de Veterinaria, Regional Campus of International Excellence "Campus Mare Nostrum", Universidad de Murcia, Murcia, Spain
| | - Juan C. Gómez-Fernández
- Departamento de Bioquímica y Biología Molecular-A, Facultad de Veterinaria, Regional Campus of International Excellence "Campus Mare Nostrum", Universidad de Murcia, Murcia, Spain
- * E-mail:
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26
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Aurich AC, Niemann B, Pan R, Gruenler S, Issa H, Silber RE, Rohrbach S. Age-dependent effects of high fat-diet on murine left ventricles: role of palmitate. Basic Res Cardiol 2013; 108:369. [PMID: 23836256 DOI: 10.1007/s00395-013-0369-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Revised: 06/25/2013] [Accepted: 06/26/2013] [Indexed: 10/26/2022]
Abstract
Obesity-associated heart disease results in myocardial lipid accumulation leading to lipotoxicity. However, recent studies are suggestive of protective effects of high-fat diets (HFD). To determine whether age results in differential changes in diet-induced obesity, we fed young and old (3 and 18 months) male C57Bl/6 mice control diet, low-fat diet (both 10 kcal% fat) or HFD (45 kcal% fat) for 16 weeks, after which we analyzed LV function, mitochondrial changes, and potential modifiers of myocardial structure. HFD or age did not change LV systolic function, although a mildly increased BNP was observed in all old mice. This was associated with increased myocardial collagen, triglyceride, diacylglycerol, and ceramide content as well as higher caspase 3 activation in old mice with highest levels in old HFD mice. Pyruvate-dependent respiration and mitochondrial biogenesis were reduced in all old mice and in young HFD mice. Activation of AMPK, a strong inducer of mitochondrial biogenesis, was reduced in both HFD groups and in old control or LFD mice. Cardiomyocytes from old rats demonstrated significantly reduced AMPK activation, impaired mitochondrial biogenesis, higher ceramide content, and reduced viability after palmitate (C16:0) in vitro, while no major deleterious effects were observed in young cardiomyocytes. Aged but not young cardiomyocytes were unable to respond to higher palmitate with increased fatty acid oxidation. Thus, HFD results in cardiac structural alterations and accumulation of lipid intermediates predominantly in old mice, possibly due to the inability of old cardiomyocytes to adapt to high-fatty acid load.
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Affiliation(s)
- Anne-Cathleen Aurich
- Institute of Pathophysiology, Martin Luther University Halle-Wittenberg, Halle, Germany
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27
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Strijbis K, Tafesse FG, Fairn GD, Witte MD, Dougan SK, Watson N, Spooner E, Esteban A, Vyas VK, Fink GR, Grinstein S, Ploegh HL. Bruton's Tyrosine Kinase (BTK) and Vav1 contribute to Dectin1-dependent phagocytosis of Candida albicans in macrophages. PLoS Pathog 2013; 9:e1003446. [PMID: 23825946 PMCID: PMC3694848 DOI: 10.1371/journal.ppat.1003446] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2013] [Accepted: 05/07/2013] [Indexed: 12/28/2022] Open
Abstract
Phagocytosis of the opportunistic fungal pathogen Candida albicans by cells of the innate immune system is vital to prevent infection. Dectin-1 is the major phagocytic receptor involved in anti-fungal immunity. We identify two new interacting proteins of Dectin-1 in macrophages, Bruton's Tyrosine Kinase (BTK) and Vav1. BTK and Vav1 are recruited to phagocytic cups containing C. albicans yeasts or hyphae but are absent from mature phagosomes. BTK and Vav1 localize to cuff regions surrounding the hyphae, while Dectin-1 lines the full length of the phagosome. BTK and Vav1 colocalize with the lipid PI(3,4,5)P3 and F-actin at the phagocytic cup, but not with diacylglycerol (DAG) which marks more mature phagosomal membranes. Using a selective BTK inhibitor, we show that BTK contributes to DAG synthesis at the phagocytic cup and the subsequent recruitment of PKCε. BTK- or Vav1-deficient peritoneal macrophages display a defect in both zymosan and C. albicans phagocytosis. Bone marrow-derived macrophages that lack BTK or Vav1 show reduced uptake of C. albicans, comparable to Dectin1-deficient cells. BTK- or Vav1-deficient mice are more susceptible to systemic C. albicans infection than wild type mice. This work identifies an important role for BTK and Vav1 in immune responses against C. albicans.
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Affiliation(s)
- Karin Strijbis
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, United States of America
| | - Fikadu G. Tafesse
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, United States of America
| | - Gregory D. Fairn
- Keenan Research Centre of the Li Ka Shing Knowledge Institute, St. Michael's Hospital, Department of Surgery, University of Toronto, Toronto, Ontario, Canada
| | - Martin D. Witte
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, United States of America
| | - Stephanie K. Dougan
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, United States of America
| | - Nicki Watson
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, United States of America
| | - Eric Spooner
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, United States of America
| | - Alexandre Esteban
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, United States of America
| | - Valmik K. Vyas
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, United States of America
| | - Gerald R. Fink
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, United States of America
| | - Sergio Grinstein
- Keenan Research Centre of the Li Ka Shing Knowledge Institute, St. Michael's Hospital, Department of Surgery, University of Toronto, Toronto, Ontario, Canada
- Program in Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Hidde L. Ploegh
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, United States of America
- * E-mail:
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Chan SM, Sun RQ, Zeng XY, Choong ZH, Wang H, Watt MJ, Ye JM. Activation of PPARα ameliorates hepatic insulin resistance and steatosis in high fructose-fed mice despite increased endoplasmic reticulum stress. Diabetes 2013; 62:2095-105. [PMID: 23349482 PMCID: PMC3661626 DOI: 10.2337/db12-1397] [Citation(s) in RCA: 119] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Endoplasmic reticulum (ER) stress is suggested to cause hepatic insulin resistance by increasing de novo lipogenesis (DNL) and directly interfering with insulin signaling through the activation of the c-Jun N-terminal kinase (JNK) and IκB kinase (IKK) pathway. The current study interrogated these two proposed mechanisms in a mouse model of hepatic insulin resistance induced by a high fructose (HFru) diet with the treatment of fenofibrate (FB) 100 mg/kg/day, a peroxisome proliferator-activated receptor α (PPARα) agonist known to reduce lipid accumulation while maintaining elevated DNL in the liver. FB administration completely corrected HFru-induced glucose intolerance, hepatic steatosis, and the impaired hepatic insulin signaling (pAkt and pGSK3β). Of note, both the IRE1/XBP1 and PERK/eIF2α arms of unfolded protein response (UPR) signaling were activated. While retaining the elevated DNL (indicated by the upregulation of SREBP1c, ACC, FAS, and SCD1 and [3H]H2O incorporation into lipids), FB treatment markedly increased fatty acid oxidation (indicated by induction of ACOX1, p-ACC, β-HAD activity, and [14C]palmitate oxidation) and eliminated the accumulation of diacylglycerols (DAGs), which is known to have an impact on insulin signaling. Despite the marked activation of UPR signaling, neither JNK nor IKK appeared to be activated. These findings suggest that lipid accumulation (mainly DAGs), rather than the activation of JNK or IKK, is pivotal for ER stress to cause hepatic insulin resistance. Therefore, by reducing the accumulation of deleterious lipids, activation of PPARα can ameliorate hepatic insulin resistance against increased ER stress.
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Affiliation(s)
- Stanley M.H. Chan
- Molecular Pharmacology for Diabetes Group, Health Innovations Research Institute and School of Health Sciences, RMIT University, Melbourne, Victoria, Australia
| | - Ruo-Qiong Sun
- Molecular Pharmacology for Diabetes Group, Health Innovations Research Institute and School of Health Sciences, RMIT University, Melbourne, Victoria, Australia
| | - Xiao-Yi Zeng
- Molecular Pharmacology for Diabetes Group, Health Innovations Research Institute and School of Health Sciences, RMIT University, Melbourne, Victoria, Australia
| | - Zi-Heng Choong
- Molecular Pharmacology for Diabetes Group, Health Innovations Research Institute and School of Health Sciences, RMIT University, Melbourne, Victoria, Australia
| | - Hao Wang
- Molecular Pharmacology for Diabetes Group, Health Innovations Research Institute and School of Health Sciences, RMIT University, Melbourne, Victoria, Australia
| | - Matthew J. Watt
- Biology of Lipid Metabolism Laboratory, Department of Physiology, Monash University, Melbourne, Victoria, Australia
| | - Ji-Ming Ye
- Molecular Pharmacology for Diabetes Group, Health Innovations Research Institute and School of Health Sciences, RMIT University, Melbourne, Victoria, Australia
- Corresponding author: Ji-Ming Ye,
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Huang C, Ogawa R. Roles of lipid metabolism in keloid development. Lipids Health Dis 2013; 12:60. [PMID: 23634948 PMCID: PMC3653711 DOI: 10.1186/1476-511x-12-60] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Accepted: 04/26/2013] [Indexed: 11/12/2022] Open
Abstract
Keloids are common cutaneous pathological scars that are characterised by the histological accumulation of fibroblasts, collagen fibres, and clinically significant invasive growth. Although increasing lines of research on keloids have revealed genetic and environmental factors that contribute to their formation, the etiology of these scars remains unclear. Several studies have suggested the involvement of lipid metabolism, from a nutritional point of view. However, the role that lipid metabolism plays in the pathogenesis and progression of keloids has not previously been reviewed. The progress that has been made in understanding the roles of the pro- and anti-inflammatory lipid mediators in inflammation, and how they relate to the formation and progression of keloids, is also outlined. In particular, the possible relationships between mechanotransduction and lipid metabolites in keloids are explored. Mechanotransduction is the process by which physical forces are converted into biochemical signals that are then integrated into cellular responses. It is possible that lipid rafts and caveolae provide the location of lipid signaling and interactions between these signaling pathways and mechanotransduction. Moreover, interactions between lipid signaling pathway molecules and mechanotransduction molecules have been observed. A better understanding of the lipid profile changes and the functional roles lipid metabolism plays in keloids will help to identify target molecules for the development of novel interventions that can prevent, reduce, or even reverse pathological scar formation and/or progression.
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Affiliation(s)
- Chenyu Huang
- Department of Plastic, Reconstructive and Aesthetic Surgery, Nippon Medical School, 1-1-5 Sendagi Bunkyo-ku, Tokyo 113-8603, Japan
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30
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Liang H, Tantiwong P, Sriwijitkamol A, Shanmugasundaram K, Mohan S, Espinoza S, Defronzo RA, Dubé JJ, Musi N. Effect of a sustained reduction in plasma free fatty acid concentration on insulin signalling and inflammation in skeletal muscle from human subjects. J Physiol 2013; 591:2897-909. [PMID: 23529132 DOI: 10.1113/jphysiol.2012.247510] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Free fatty acids (FFAs) have been implicated in the pathogenesis of insulin resistance. Reducing plasma FFA concentration in obese and type 2 diabetic (T2DM) subjects improves insulin sensitivity. However, the molecular mechanism by which FFA reduction improves insulin sensitivity in human subjects is not fully understood. In the present study, we tested the hypothesis that pharmacological FFA reduction enhances insulin action by reducing local (muscle) inflammation, leading to improved insulin signalling. Insulin-stimulated total glucose disposal (TGD), plasma FFA species, muscle insulin signalling, IBα protein, c-Jun phosphorylation, inflammatory gene (toll-like receptor 4 and monocyte chemotactic protein 1) expression, and ceramide and diacylglycerol (DAG) content were measured in muscle from a group of obese and T2DM subjects before and after administration of the antilipolytic drug acipimox for 7 days, and the results were compared to lean individuals. We found that obese and T2DM subjects had elevated saturated and unsaturated FFAs in plasma, and acipimox reduced all FFA species. Acipimox-induced reductions in plasma FFAs improved TGD and insulin signalling in obese and T2DM subjects. Acipimox increased IBα protein (an indication of decreased IB kinase-nuclear factor B signalling) in both obese and T2DM subjects, but did not affect c-Jun phosphorylation in any group. Acipimox also decreased inflammatory gene expression, although this reduction only occurred in T2DM subjects. Ceramide and DAG content did not change. To summarize, pharmacological FFA reduction improves insulin signalling in muscle from insulin-resistant subjects. This beneficial effect on insulin action could be related to a decrease in local inflammation. Notably, the improvements in insulin action were more pronounced in T2DM, indicating that these subjects are more susceptible to the toxic effect of FFAs.
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Affiliation(s)
- Hanyu Liang
- N. Musi: Audie L. Murphy VA Medical Center, 7400 Merton Minter, San Antonio, TX 78229, USA.
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31
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Keung W, Ussher JR, Jaswal JS, Raubenheimer M, Lam VH, Wagg CS, Lopaschuk GD. Inhibition of carnitine palmitoyltransferase-1 activity alleviates insulin resistance in diet-induced obese mice. Diabetes 2013; 62:711-20. [PMID: 23139350 PMCID: PMC3581198 DOI: 10.2337/db12-0259] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Impaired skeletal muscle fatty acid oxidation has been suggested to contribute to insulin resistance and glucose intolerance. However, increasing muscle fatty acid oxidation may cause a reciprocal decrease in glucose oxidation, which might impair insulin sensitivity and glucose tolerance. We therefore investigated what effect inhibition of mitochondrial fatty acid uptake has on whole-body glucose tolerance and insulin sensitivity in obese insulin-resistant mice. C57BL/6 mice were fed a high-fat diet (60% calories from fat) for 12 weeks to develop insulin resistance. Subsequent treatment of mice for 4 weeks with the carnitine palmitoyltransferase-1 inhibitor, oxfenicine (150 mg/kg i.p. daily), resulted in improved whole-body glucose tolerance and insulin sensitivity. Exercise capacity was increased in oxfenicine-treated mice, which was accompanied by an increased respiratory exchange ratio. In the gastrocnemius muscle, oxfenicine increased pyruvate dehydrogenase activity, membrane GLUT4 content, and insulin-stimulated Akt phosphorylation. Intramyocellular levels of lipid intermediates, including ceramide, long-chain acyl CoA, and diacylglycerol, were also decreased. Our results demonstrate that inhibition of mitochondrial fatty acid uptake improves insulin sensitivity in diet-induced obese mice. This is associated with increased carbohydrate utilization and improved insulin signaling in the skeletal muscle, suggestive of an operating Randle Cycle in muscle.
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Boon J, Hoy AJ, Stark R, Brown RD, Meex RC, Henstridge DC, Schenk S, Meikle PJ, Horowitz JF, Kingwell BA, Bruce CR, Watt MJ. Ceramides contained in LDL are elevated in type 2 diabetes and promote inflammation and skeletal muscle insulin resistance. Diabetes 2013; 62:401-10. [PMID: 23139352 PMCID: PMC3554351 DOI: 10.2337/db12-0686] [Citation(s) in RCA: 223] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Dysregulated lipid metabolism and inflammation are linked to the development of insulin resistance in obesity, and the intracellular accumulation of the sphingolipid ceramide has been implicated in these processes. Here, we explored the role of circulating ceramide on the pathogenesis of insulin resistance. Ceramide transported in LDL is elevated in the plasma of obese patients with type 2 diabetes and correlated with insulin resistance but not with the degree of obesity. Treating cultured myotubes with LDL containing ceramide promoted ceramide accrual in cells and was accompanied by reduced insulin-stimulated glucose uptake, Akt phosphorylation, and GLUT4 translocation compared with LDL deficient in ceramide. LDL-ceramide induced a proinflammatory response in cultured macrophages via toll-like receptor-dependent and -independent mechanisms. Finally, infusing LDL-ceramide into lean mice reduced insulin-stimulated glucose uptake, and this was due to impaired insulin action specifically in skeletal muscle. These newly identified roles of LDL-ceramide suggest that strategies aimed at reducing hepatic ceramide production or reducing ceramide packaging into lipoproteins may improve skeletal muscle insulin action.
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MESH Headings
- Animals
- Cells, Cultured
- Ceramides/blood
- Ceramides/pharmacology
- Diabetes Mellitus, Type 2/blood
- Diabetes Mellitus, Type 2/metabolism
- Female
- Glucose/metabolism
- Glucose Transporter Type 4/metabolism
- Humans
- Inflammation/blood
- Inflammation/metabolism
- Insulin/metabolism
- Insulin Resistance/physiology
- Lipoproteins, LDL/blood
- Lipoproteins, LDL/pharmacology
- Macrophages/drug effects
- Macrophages/metabolism
- Male
- Mice
- Mice, Inbred C57BL
- Muscle Fibers, Skeletal/drug effects
- Muscle Fibers, Skeletal/metabolism
- Muscle, Skeletal/drug effects
- Muscle, Skeletal/metabolism
- Obesity/blood
- Obesity/metabolism
- Phosphorylation
- Proto-Oncogene Proteins c-akt/metabolism
- Toll-Like Receptors/metabolism
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Affiliation(s)
- James Boon
- Biology of Lipid Metabolism Laboratory, Department of Physiology, Monash University, Clayton, Victoria, Australia
| | - Andrew J. Hoy
- Biology of Lipid Metabolism Laboratory, Department of Physiology, Monash University, Clayton, Victoria, Australia
| | - Romana Stark
- Biology of Lipid Metabolism Laboratory, Department of Physiology, Monash University, Clayton, Victoria, Australia
| | - Russell D. Brown
- Biology of Lipid Metabolism Laboratory, Department of Physiology, Monash University, Clayton, Victoria, Australia
| | - Ruth C. Meex
- Biology of Lipid Metabolism Laboratory, Department of Physiology, Monash University, Clayton, Victoria, Australia
| | | | - Simon Schenk
- Department of Orthopaedic Surgery, University of California, San Diego, California
| | - Peter J. Meikle
- Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia
| | | | | | - Clinton R. Bruce
- Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia
| | - Matthew J. Watt
- Biology of Lipid Metabolism Laboratory, Department of Physiology, Monash University, Clayton, Victoria, Australia
- Corresponding author: Matthew J. Watt,
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Pokotylo I, Pejchar P, Potocký M, Kocourková D, Krčková Z, Ruelland E, Kravets V, Martinec J. The plant non-specific phospholipase C gene family. Novel competitors in lipid signalling. Prog Lipid Res 2012; 52:62-79. [PMID: 23089468 DOI: 10.1016/j.plipres.2012.09.001] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Revised: 09/25/2012] [Accepted: 09/25/2012] [Indexed: 11/16/2022]
Abstract
Non-specific phospholipases C (NPCs) were discovered as a novel type of plant phospholipid-cleaving enzyme homologous to bacterial phosphatidylcholine-specific phospholipases C and responsible for lipid conversion during phosphate-limiting conditions. The six-gene family was established in Arabidopsis, and growing evidence suggests the involvement of two articles NPCs in biotic and abiotic stress responses as well as phytohormone actions. In addition, the diacylglycerol produced via NPCs is postulated to participate in membrane remodelling, general lipid metabolism and cross-talk with other phospholipid signalling systems in plants. This review summarises information concerning this new plant protein family and focusses on its sequence analysis, biochemical properties, cellular and tissue distribution and physiological functions. Possible modes of action are also discussed.
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Affiliation(s)
- Igor Pokotylo
- Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine, Kyiv, Ukraine
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34
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Watt MJ, Barnett AC, Bruce CR, Schenk S, Horowitz JF, Hoy AJ. Regulation of plasma ceramide levels with fatty acid oversupply: evidence that the liver detects and secretes de novo synthesised ceramide. Diabetologia 2012; 55:2741-2746. [PMID: 22854889 PMCID: PMC3576922 DOI: 10.1007/s00125-012-2649-3] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2012] [Accepted: 06/21/2012] [Indexed: 01/12/2023]
Abstract
AIMS/HYPOTHESIS Plasma ceramide concentrations correlate with insulin sensitivity, inflammation and atherosclerotic risk. We hypothesised that plasma ceramide concentrations are increased in the presence of elevated fatty acid levels and are regulated by increased liver serine C-palmitoyltransferase (SPT) activity. METHODS Lean humans and rats underwent an acute lipid infusion and plasma ceramide levels were determined. One group of lipid-infused rats was administered myriocin to inhibit SPT activity. Liver SPT activity was determined in lipid-infused rats, and obese, insulin resistant mice. The time and palmitate dose-dependent synthesis of intracellular and secreted ceramide was determined in HepG2 liver cells. RESULTS Plasma ceramide levels were increased during lipid infusion in humans and rats, and in obese, insulin-resistant mice. The increase in plasma ceramide was not associated with changes in liver SPT activity, and inhibiting SPT activity by ~50% did not alter plasma ceramide levels in lipid-infused rats. In HepG2 liver cells, palmitate incorporation into extracellular ceramide was both dose- and time-dependent, suggesting the liver cells rapidly secreted the newly synthesised ceramide. CONCLUSIONS/INTERPRETATION Elevated systemic fatty acid availability increased plasma ceramide but this was not associated with changes in hepatic SPT activity, suggesting that liver ceramide synthesis is driven by substrate availability rather than increased SPT activity. This report also provides evidence that the liver is sensitive to the intracellular ceramide concentration, and an increase in liver ceramide secretion may help protect the liver from the deleterious effects of intracellular ceramide accumulation.
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Affiliation(s)
- M J Watt
- Department of Physiology, Monash University, Building 13F, Clayton, VIC, 3800, Australia.
| | - A C Barnett
- Department of Physiology, Monash University, Building 13F, Clayton, VIC, 3800, Australia
| | - C R Bruce
- Department of Physiology, Monash University, Building 13F, Clayton, VIC, 3800, Australia
- Baker IDI Heart & Diabetes Institute, Melbourne, VIC, Australia
| | - S Schenk
- School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
- Department of Orthopaedic Surgery, University of California, San Diego, CA, USA
| | - J F Horowitz
- School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
| | - A J Hoy
- Department of Physiology, Monash University, Building 13F, Clayton, VIC, 3800, Australia.
- Discipline of Physiology, University of Sydney, Anderson Stuart Building (F13), Sydney, NSW, 2006, Australia.
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35
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Davidson EP, Coppey LJ, Holmes A, Yorek MA. Effect of inhibition of angiotensin converting enzyme and/or neutral endopeptidase on vascular and neural complications in high fat fed/low dose streptozotocin-diabetic rats. Eur J Pharmacol 2011; 677:180-7. [PMID: 22198047 DOI: 10.1016/j.ejphar.2011.12.003] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2011] [Revised: 11/10/2011] [Accepted: 12/01/2011] [Indexed: 12/17/2022]
Abstract
Treating high fat fed/low dose streptozotocin-diabetic rats; model of type 2 diabetes, with ilepatril (vasopeptidase inhibitor, blocks neutral endopeptidase (NEP) and angiotensin converting enzyme (ACE)) improved vascular and neural functions. Next, studies were performed to determine the individual effect of inhibition of NEP and ACE on diabetes-induced vascular and neural dysfunctions. High fat fed rats (8 weeks) were treated with 30 mg/kg streptozotocin (i.p.) and after 4 additional weeks, were treated for 12 weeks with ilepatril, enalapril (ACE inhibitor) or candoxatril (NEP inhibitor) followed by analysis of vascular and neural functions. Glucose clearance was impaired in diabetic rats and was not improved with treatment although treatment with ilepatril or candoxatril partially improved insulin stimulated glucose uptake by isolated soleus muscle. Diabetes caused slowing of motor and sensory nerve conduction, thermal hypoalgesia, reduction in intraepidermal nerve fiber (IENF) profiles and impairment in vascular relaxation to acetylcholine and calcitonin gene-related peptide (CGRP) in epineurial arterioles of the sciatic nerve. Inhibition of NEP improved nerve conduction velocity and inhibition of NEP or ACE improved thermal sensitivity and protected IENF density. Ilepatril and candoxatril treatments of diabetic rats were efficacious in improving vascular responsiveness to acetylcholine in epineurial arterioles; whereas all three treatments improved vascular response to CGRP. These studies suggest that inhibition of NEP and ACE activity is an effective approach for treatment of type 2 diabetes neural and vascular complications.
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Affiliation(s)
- Eric P Davidson
- Department of Internal Medicine, University of Iowa, Iowa City, IA, 52246, United States
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36
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Myocardial ATGL overexpression decreases the reliance on fatty acid oxidation and protects against pressure overload-induced cardiac dysfunction. Mol Cell Biol 2011; 32:740-50. [PMID: 22158969 DOI: 10.1128/mcb.06470-11] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Alterations in myocardial triacylglycerol content have been associated with poor left ventricular function, suggesting that enzymes involved in myocardial triacylglycerol metabolism play an important role in regulating contractile function. Myocardial triacylglycerol catabolism is mediated by adipose triglyceride lipase (ATGL), which is rate limiting for triacylglycerol hydrolysis. To address the influence of triacylglycerol hydrolysis on myocardial energy metabolism and function, we utilized mice with cardiomyocyte-specific ATGL overexpression (MHC-ATGL). Biochemical examination of MHC-ATGL hearts revealed chronically reduced myocardial triacylglycerol content but unchanged levels of long-chain acyl coenzyme A esters, ceramides, and diacylglycerols. Surprisingly, fatty acid oxidation rates were decreased in ex vivo perfused working hearts from MHC-ATGL mice, which was compensated by increased rates of glucose oxidation. Interestingly, reduced myocardial triacylglycerol content was associated with moderately enhanced in vivo systolic function in MHC-ATGL mice and increased isoproterenol-induced cell shortening of isolated primary cardiomyocytes. Most importantly, MHC-ATGL mice were protected from pressure overload-induced systolic dysfunction and detrimental structural remodeling following transverse aortic constriction. Overall, this study shows that ATGL overexpression is sufficient to alter myocardial energy metabolism and improve cardiac function.
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37
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Keung W, Palaniyappan A, Lopaschuk GD. Chronic central leptin decreases food intake and improves glucose tolerance in diet-induced obese mice independent of hypothalamic malonyl CoA levels and skeletal muscle insulin sensitivity. Endocrinology 2011; 152:4127-37. [PMID: 21914780 DOI: 10.1210/en.2011-1254] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Although acute leptin administration in the hypothalamus decreases food intake and increases peripheral energy metabolism, the peripheral actions of central chronic leptin administration are less understood. In this study, we investigated what effects chronic (7 d) intracerebroventricular (ICV) administration of leptin has on energy metabolism and insulin sensitivity in diet-induced obese mice. C57/BL mice were fed a low-fat diet (LFD; 10% total calories) or high-fat diet (HFD; 60% total calories) for 8 wk after which leptin was administered ICV for 7 consecutive days. Mice fed a HFD showed signs of insulin resistance, as evidenced by an impaired glucose tolerance test. Chronic leptin treatment resulted in a decrease in food intake and body weight and normalization of glucose clearance but no improvement in insulin sensitivity. Chronic ICV leptin increased hypothalamic signal transducer and activator of transcription-3 and AMP-activated protein kinase phosphorylation but did not change hypothalamic malonyl CoA levels in HFD fed and LFD-fed mice. In the gastrocnemius muscles, the levels of malonyl CoA in both leptin-treated groups were lower than their respective control groups, suggesting an increase in fatty acid oxidation. However, only in the muscles of ICV leptin-treated LFD mice was there a decrease in lipid metabolites including diacylglycerol, triacylglycerol, and ceramide. Our results suggest that chronic ICV leptin decreases food consumption and body weight via a mechanism different from acute ICV leptin administration. Although chronic ICV leptin treatment in HFD mice improves glucose tolerance, this occurs independent of changes in insulin sensitivity in the muscles of HFD mice.
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Affiliation(s)
- Wendy Keung
- Cardiovascular Research Centre, University of Alberta, Edmonton, Alberta, Canada T6G 2S2
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38
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Proteins kinase Cɛ is required for non-small cell lung carcinoma growth and regulates the expression of apoptotic genes. Oncogene 2011; 31:2593-600. [PMID: 21996750 DOI: 10.1038/onc.2011.428] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Protein kinase C (PKC)ɛ, a member of the novel PKC family, has key roles in mitogenesis and survival in normal and cancer cells. PKCɛ is frequently overexpressed in epithelial cancers, particularly in lung cancer. Using a short-hairpin RNA approach, here we established that PKCɛ is required for non-small cell lung carcinoma (NSCLC) growth in vitro as well as tumor growth when inoculated into athymic mice. Moreover, sustained delivery of a PKCɛ-selective inhibitor peptide, ɛV1-2, reduced xenograft growth in mice. Both RNA interference depletion and pharmacological inhibition of PKCɛ caused a marked elevation in the number of apoptotic cells in NSCLC tumors. PKCɛ-depleted NSCLC cells show elevated expression of pro-apoptotic proteins of the Bcl-2 family, caspase recruitment domain-containing proteins and tumor necrosis factor ligands/receptor superfamily members. Moreover, a Gene Set Enrichment Analysis revealed that a vast majority of the genes changed in PKCɛ-depleted cells were also deregulated in human NSCLC. Our results strongly suggest that PKCɛ is required for NSCLC cell survival and maintenance of NSCLC tumor growth. Therefore, PKCɛ may represent an attractive therapeutic target for NSCLC.
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39
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Dolinsky VW, Rueda-Clausen CF, Morton JS, Davidge ST, Dyck JR. Continued postnatal administration of resveratrol prevents diet-induced metabolic syndrome in rat offspring born growth restricted. Diabetes 2011; 60:2274-84. [PMID: 21810598 PMCID: PMC3161324 DOI: 10.2337/db11-0374] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
OBJECTIVE A prenatal hypoxic insult leading to intrauterine growth restriction (IUGR) increases the susceptibility to develop metabolic syndrome (MetS) later in life. Since resveratrol (Resv), the polyphenol produced by plants, exerts insulin-sensitizing effects, we tested whether Resv could prevent deleterious metabolic effects of being born IUGR. RESEARCH DESIGN AND METHODS Pregnant rats were exposed to either a normoxic (control; 21% O(2)) or a hypoxic (IUGR; 11.5% O(2)) environment during the last third of gestation. After weaning, male offspring were randomly assigned to receive either a high-fat (HF; 45% fat) diet or an HF diet with Resv (4 g/kg diet) for 9 weeks when various parameters of the MetS were measured. RESULTS Relative to normoxic controls, hypoxia-induced IUGR offspring developed a more severe MetS, including glucose intolerance and insulin resistance, increased intra-abdominal fat deposition and intra-abdominal adipocyte size, and increased plasma triacylglycerol (TG) and free fatty acids, as well as peripheral accumulation of TG, diacylglycerol, and ceramides. In only IUGR offspring, the administration of Resv reduced intra-abdominal fat deposition to levels comparable with controls, improved the plasma lipid profile, and reduced accumulation of TG and ceramides in the tissues. Moreover, Resv ameliorated insulin resistance and glucose intolerance as well as impaired Akt signaling in the liver and skeletal muscle of IUGR offspring and activated AMP-activated protein kinase, which likely contributed to improved metabolic parameters in Resv-treated IUGR rats. CONCLUSIONS Our results suggest that early, postnatal administration of Resv can improve the metabolic profile of HF-fed offspring born from pregnancies complicated by IUGR.
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Affiliation(s)
- Vernon W. Dolinsky
- Department of Pediatrics, University of Alberta, Edmonton, Canada
- Women and Children’s Health Research Institute, University of Alberta, Edmonton, Canada
- Cardiovascular Research Centre, University of Alberta, Edmonton, Canada
- Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Canada
- Alberta Diabetes Institute, University of Alberta, Edmonton, Canada
| | - Christian F. Rueda-Clausen
- Women and Children’s Health Research Institute, University of Alberta, Edmonton, Canada
- Cardiovascular Research Centre, University of Alberta, Edmonton, Canada
- Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Canada
- Alberta Diabetes Institute, University of Alberta, Edmonton, Canada
- Department of Physiology, University of Alberta, Edmonton, Canada
| | - Jude S. Morton
- Women and Children’s Health Research Institute, University of Alberta, Edmonton, Canada
- Cardiovascular Research Centre, University of Alberta, Edmonton, Canada
- Alberta Diabetes Institute, University of Alberta, Edmonton, Canada
- Department of Obstetrics and Gynecology, University of Alberta, Edmonton, Canada
| | - Sandra T. Davidge
- Women and Children’s Health Research Institute, University of Alberta, Edmonton, Canada
- Cardiovascular Research Centre, University of Alberta, Edmonton, Canada
- Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Canada
- Alberta Diabetes Institute, University of Alberta, Edmonton, Canada
- Department of Physiology, University of Alberta, Edmonton, Canada
- Department of Obstetrics and Gynecology, University of Alberta, Edmonton, Canada
| | - Jason R.B. Dyck
- Department of Pediatrics, University of Alberta, Edmonton, Canada
- Women and Children’s Health Research Institute, University of Alberta, Edmonton, Canada
- Cardiovascular Research Centre, University of Alberta, Edmonton, Canada
- Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Canada
- Alberta Diabetes Institute, University of Alberta, Edmonton, Canada
- Corresponding author: Jason R.B. Dyck,
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40
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Shulga YV, Topham MK, Epand RM. Regulation and functions of diacylglycerol kinases. Chem Rev 2011; 111:6186-208. [PMID: 21800853 DOI: 10.1021/cr1004106] [Citation(s) in RCA: 158] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Yulia V Shulga
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada
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41
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Sarri E, Sicart A, Lázaro-Diéguez F, Egea G. Phospholipid synthesis participates in the regulation of diacylglycerol required for membrane trafficking at the Golgi complex. J Biol Chem 2011; 286:28632-43. [PMID: 21700701 DOI: 10.1074/jbc.m111.267534] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The lipid metabolite diacylglycerol (DAG) is required for transport carrier biogenesis at the Golgi, although how cells regulate its levels is not well understood. Phospholipid synthesis involves highly regulated pathways that consume DAG and can contribute to its regulation. Here we altered phosphatidylcholine (PC) and phosphatidylinositol synthesis for a short period of time in CHO cells to evaluate the changes in DAG and its effects in membrane trafficking at the Golgi. We found that cellular DAG rapidly increased when PC synthesis was inhibited at the non-permissive temperature for the rate-limiting step of PC synthesis in CHO-MT58 cells. DAG also increased when choline and inositol were not supplied. The major phospholipid classes and triacylglycerol remained unaltered for both experimental approaches. The analysis of Golgi ultrastructure and membrane trafficking showed that 1) the accumulation of the budding vesicular profiles induced by propanolol was prevented by inhibition of PC synthesis, 2) the density of KDEL receptor-containing punctated structures at the endoplasmic reticulum-Golgi interface correlated with the amount of DAG, and 3) the post-Golgi transport of the yellow fluorescent temperature-sensitive G protein of stomatitis virus and the secretion of a secretory form of HRP were both reduced when DAG was lowered. We confirmed that DAG-consuming reactions of lipid synthesis were present in Golgi-enriched fractions. We conclude that phospholipid synthesis pathways play a significant role to regulate the DAG required in Golgi-dependent membrane trafficking.
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Affiliation(s)
- Elisabet Sarri
- Departament de Biologia Cellular, Immunologia, i Neurociències, Facultat de Medicina and Institut d'Investigacions Biomèdiques August Pi i Sunyer, Universitat de Barcelona, C/ Casanova, 143, E-08036 Barcelona, Spain.
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42
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Newsom SA, Schenk S, Li M, Everett AC, Horowitz JF. High fatty acid availability after exercise alters the regulation of muscle lipid metabolism. Metabolism 2011; 60:852-9. [PMID: 20870251 PMCID: PMC3011035 DOI: 10.1016/j.metabol.2010.08.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2010] [Revised: 08/11/2010] [Accepted: 08/11/2010] [Indexed: 01/22/2023]
Abstract
We previously reported that a single exercise session protects against fatty acid (FA)-induced insulin resistance, perhaps in part through augmented intramyocellular triacylglycerol (IMTG) synthesis. The aim of this study was to examine the effect of elevated FA availability after exercise on factors regulating IMTG metabolism. After exercise (90 minutes, 65% peak oxygen uptake), 7 healthy women (body mass index, 23 ± 1 kg/m(2)) were infused overnight (16 hours) with either a lipid and heparin solution (LIPID, 0.11 g fat per kilogram per hour) or saline (SALINE). We measured resting FA oxidation (indirect calorimetry) and obtained a skeletal muscle biopsy sample the next morning. The 4-fold increase in overnight plasma FA concentration during LIPID increased IMTG by approximately 30% during LIPID vs SALINE. This was accompanied by an approximately 25% greater membrane-associated abundance of the FA transporter FAT/CD36 (P < .01) and an approximately 8% increase in the activity of the IMTG synthesis enzyme glycerol-3-phosphate acyltransferase (GPAT, P < .01). In contrast, resting FA oxidation was not affected. We also found no difference in the protein abundance of GPAT1 and diacylglycerol acyltransferase-1, diacylglycerol acyltransferase activity, or the abundance of the lipid droplet coat proteins (perilipins 2, 3, 4, and 5) between treatments. Our findings suggest that augmented capacity for FA flux into muscle (ie, via membrane-associated FAT/CD36), perhaps together with a slight yet significant increase in activity of a key IMTG synthesis enzyme (GPAT), may enhance IMTG storage when FA availability is high after exercise. The importance of the absence of a change in perilipin protein abundance despite increased muscle lipid storage remains to be determined.
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Affiliation(s)
| | | | | | | | - Jeffrey F. Horowitz
- Corresponding Author: Jeffrey F. Horowitz, School of Kinesiology, University of Michigan, 401 Washtenaw Ave., Ann Arbor, MI, 48109-2214, Phone: (734) 647-1076, Fax: (734) 936-1925,
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43
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Shibata Y, Kawada-Matsuo M, Shirai Y, Saito N, Li D, Yamashita Y. Streptococcus mutans diacylglycerol kinase homologue: a potential target for anti-caries chemotherapy. J Med Microbiol 2011; 60:625-630. [DOI: 10.1099/jmm.0.026070-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Yukie Shibata
- Section of Preventive and Public Health Dentistry, Division of Oral Health, Growth and Development, Kyushu University Faculty of Dental Science, Fukuoka, Japan
| | - Miki Kawada-Matsuo
- Section of Preventive and Public Health Dentistry, Division of Oral Health, Growth and Development, Kyushu University Faculty of Dental Science, Fukuoka, Japan
| | | | - Naoaki Saito
- Biosignal Research Center, Kobe University, Kobe, Japan
| | - Dan Li
- Section of Preventive and Public Health Dentistry, Division of Oral Health, Growth and Development, Kyushu University Faculty of Dental Science, Fukuoka, Japan
| | - Yoshihisa Yamashita
- Section of Preventive and Public Health Dentistry, Division of Oral Health, Growth and Development, Kyushu University Faculty of Dental Science, Fukuoka, Japan
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Brandon AE, Hoy AJ, Wright LE, Turner N, Hegarty BD, Iseli TJ, Julia Xu X, Cooney GJ, Saha AK, Ruderman NB, Kraegen EW. The evolution of insulin resistance in muscle of the glucose infused rat. Arch Biochem Biophys 2011; 509:133-41. [PMID: 21420928 DOI: 10.1016/j.abb.2011.03.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2011] [Revised: 03/14/2011] [Accepted: 03/15/2011] [Indexed: 11/17/2022]
Abstract
Glucose infusion into rats causes skeletal muscle insulin resistance that initially occurs without changes in insulin signaling. The aim of the current study was to prolong glucose infusion and evaluate other events associated with the transition to muscle insulin resistance. Hyperglycemia was produced in rats by glucose infusion for 3, 5 and 8 h. The rate of infusion required to maintain hyperglycemia was reduced at 5 and 8 h. Glucose uptake into red quadriceps (RQ) and its incorporation into glycogen decreased between 3 and 5 h, further decreasing at 8 h. The earliest observed change in RQ was decreased AMPKα2 activity associated with large increases in muscle glycogen content at 3 h. Activation of the mTOR pathway occurred at 5 h. Akt phosphorylation (Ser(473)) was decreased at 8 h compared to 3 and 5, although no decrease in phosphorylation of downstream GSK-3β (Ser(9)) and AS160 (Thr(642)) was observed. White quadriceps showed a similar but delayed pattern, with insulin resistance developing by 8 h and decreased AMPKα2 activity at 5 h. These results indicate that, in the presence of a nutrient overload, alterations in muscle insulin signaling occur, but after insulin resistance develops and appropriate changes in energy/nutrient sensing pathways occur.
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Affiliation(s)
- Amanda E Brandon
- Diabetes and Obesity Program, Garvan Institute of Medical Research, Darlinghurst, NSW 2010, Australia.
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45
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Hoy AJ, Bruce CR, Turpin SM, Morris AJ, Febbraio MA, Watt MJ. Adipose triglyceride lipase-null mice are resistant to high-fat diet-induced insulin resistance despite reduced energy expenditure and ectopic lipid accumulation. Endocrinology 2011; 152:48-58. [PMID: 21106876 DOI: 10.1210/en.2010-0661] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Adipose triglyceride lipase (ATGL) null (-/-) mice store vast amounts of triacylglycerol in key glucoregulatory tissues yet exhibit enhanced insulin sensitivity and glucose tolerance. The mechanisms underpinning these divergent observations are unknown but may relate to the reduced availability of circulating fatty acids. The aim of this study was to determine whether the enhancements in insulin stimulated glucose metabolism in ATGL-/- mice persist when challenged with a high-fat diet. ATGL-/- mice fed a low-fat diet exhibit improved whole-body insulin sensitivity and glucose tolerance compared with wild-type mice. Wild-type mice became hyperlipidemic and insulin-resistant when challenged with a high-fat diet (HFD, 60% fat) for 4 wk. ATGL-/- mice fed a HFD had elevated circulating fatty acids but had reduced fasting glycemia compared to pre-high-fat diet levels and were refractory to glucose intolerance and insulin resistance. This protection from high-fat diet-induced metabolic perturbations was associated with a preference for fatty acid utilization but reduced energy expenditure and no change in markers of mitochondrial capacity or density. The protection from high-fat diet-induced insulin resistance in ATGL-/- mice was due to increased cardiac and liver insulin-stimulated glucose clearance despite increased lipid content in these tissues. Additionally, there was no difference in skeletal muscle insulin-stimulated glucose disposal, but there was a reduction observed in brown adipose tissue. Overall, these results show that ATGL-/- mice are protected from HFD-induced insulin resistance and reveal a tissue specific disparity between lipid accumulation and insulin sensitivity.
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Affiliation(s)
- Andrew J Hoy
- Monash University, Department of Physiology, Wellington Road, Clayton Victoria, 3800, Australia.
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Hilchie AL, Furlong SJ, Sutton K, Richardson A, Robichaud MRJ, Giacomantonio CA, Ridgway ND, Hoskin DW. Curcumin-induced apoptosis in PC3 prostate carcinoma cells is caspase-independent and involves cellular ceramide accumulation and damage to mitochondria. Nutr Cancer 2010; 62:379-89. [PMID: 20358476 DOI: 10.1080/01635580903441238] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Curcumin, the principal curcuminoid of tumeric, has potent anticancer activity. To determine the mechanism of curcumin-induced cytotoxicity in prostate cancer cells, we exposed PC3 prostate carcinoma cells to 25 to 100 microM curcumin for 24 to 72 h. Curcumin treatment of PC3 cells caused time- and dose-dependent induction of apoptosis and depletion of cellular reduced glutathione (GSH). Exogenous GSH and its precursor N-acetyl-cysteine, but not ascorbic acid (AA) or ebselen, decreased curcumin accumulation in PC3 cells and also prevented curcumin-induced DNA fragmentation. The failure of AA and ebselen to protect PC3 cells from curcumin-induced apoptosis argued against the involvement of reactive oxygen species; rather, GSH-mediated inhibition of curcumin-induced cytotoxicity was due to reduced curcumin accumulation in PC3 cells. Curcumin-treated PC3 cells showed apoptosis-inducing cellular ceramide accumulation and activation of p38 mitogen-activated protein kinase (MAPK) and c-jun N-terminal kinase (JNK). Caspase-3, caspase-8, and caspase-9 were activated, and cytochrome c and apoptosis-inducing factor (AIF) were released from mitochondria following curcumin treatment. Interestingly, curcumin-induced apoptosis was not prevented by p38 MAPK, JNK, or caspase inhibition. We conclude that curcumin-induced cytotoxicity was due to cellular ceramide accumulation and damage to mitochondria that resulted in apoptosis mediated by AIF and other caspase-independent processes.
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Ribas V, Nguyen MTA, Henstridge DC, Nguyen AK, Beaven SW, Watt MJ, Hevener AL. Impaired oxidative metabolism and inflammation are associated with insulin resistance in ERalpha-deficient mice. Am J Physiol Endocrinol Metab 2010; 298:E304-19. [PMID: 19920214 PMCID: PMC2822483 DOI: 10.1152/ajpendo.00504.2009] [Citation(s) in RCA: 232] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Impaired estrogen action is associated with the metabolic syndrome in humans. We sought to determine whether impaired estrogen action in female C57Bl6 mice, produced by whole body Esr1 ablation, could recapitulate aspects of this syndrome, including inflammation, insulin resistance, and obesity. Indeed, we found that global knockout (KO) of the estrogen receptor (ER)alpha leads to reduced oxygen uptake and caloric expenditure compared with wild-type (WT) mice. In addition, fasting insulin, leptin, and PAI-1 levels were markedly elevated, whereas adiponectin levels were reduced in normal chow-fed KO. Furthermore, ERalpha-KO mice exhibited impaired glucose tolerance and marked skeletal muscle insulin resistance that was accompanied by the accumulation of bioactive lipid intermediates, inflammation, and diminished PPARalpha, PPARdelta, and UCP2 transcript levels. Although the relative glucose intolerance and insulin resistance phenotype in KO mice became more severe with high-fat feeding, WT mice were refractory to these dietary-induced effects, and this protection coincided with a marked increase in circulating adiponectin and heat shock protein 72 levels in muscle, liver, and fat. These data indicate that ERalpha is critical for the maintenance of whole body insulin action and protection against tissue inflammation during both normal chow and high-fat feeding.
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Affiliation(s)
- Vicent Ribas
- David Geffen School of Medicine, Department of Medicine, Division of Endocrinology, Diabetes, and Hypertension, University of California Los Angeles, Los Angeles, California 90095-7073, USA
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Gaidhu MP, Anthony NM, Patel P, Hawke TJ, Ceddia RB. Dysregulation of lipolysis and lipid metabolism in visceral and subcutaneous adipocytes by high-fat diet: role of ATGL, HSL, and AMPK. Am J Physiol Cell Physiol 2010; 298:C961-71. [PMID: 20107043 DOI: 10.1152/ajpcell.00547.2009] [Citation(s) in RCA: 196] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
This study investigated the molecular mechanisms by which a high-fat diet (HFD) dysregulates lipolysis and lipid metabolism in mouse epididymal (visceral, VC) and inguinal (subcutaneous, SC) adipocytes. Eight-weeks of HFD feeding increased adipose triglyceride lipase (ATGL) content and comparative gene identification-58 (CGI-58) expression, whereas hormone-sensitive lipase (HSL) phosphorylation and perilipin content were severely reduced. Adipocytes from HFD mice elicited increased basal but blunted epinephrine-stimulated lipolysis and increased diacylglycerol content in both fat depots. Consistent with impaired adrenergic receptor signaling, HFD also increased adipose-specific phospholipase A(2) expression in both fat depots. Inhibition of E-prostanoid 3 receptor increased basal lipolysis in control adipocytes but failed to acutely alter the effects of HFD on lipolysis in both fat depots. In HFD visceral adipocytes, activation of adenylyl cyclases by forskolin increased HSL phosphorylation and surpassed the lipolytic response of control cells. However, in HFD subcutaneous adipocytes, forskolin induced lipolysis without detectable HSL phosphorylation, suggesting activation of an alternative lipase in response to HFD-induced suppression of HSL in VC and SC adipocytes. HFD also powerfully inhibited basal, epinephrine-, and forskolin-induced AMP kinase (AMPK) activation as well peroxisome proliferator-activated receptor gamma coactivator-1alpha expression, citrate synthase activity, and palmitate oxidation in both fat depots. In summary, novel evidence is provided that defective adrenergic receptor signaling combined with upregulation of ATGL and suppression of HSL and AMPK signaling mediate HFD-induced alterations in lipolysis and lipid utilization in VC and SC adipocytes, which may play an important role in defective lipid mobilization and metabolism seen in diet-induced obesity.
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Affiliation(s)
- Mandeep P Gaidhu
- Muscle Health Research Centre, York Univ., 4700 Keele St., Toronto, ON, Canada M3J 1P3
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Haller JF, Smith C, Liu D, Zheng H, Tornheim K, Han GS, Carman GM, Zoeller RA. Isolation of novel animal cell lines defective in glycerolipid biosynthesis reveals mutations in glucose-6-phosphate isomerase. J Biol Chem 2009; 285:866-77. [PMID: 19903819 DOI: 10.1074/jbc.m109.068213] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Glycerolipids are structural components for membranes and serve in energy storage. We describe here the use of a photodynamic selection technique to generate a population of Chinese hamster ovary cells that display a global deficiency in glycerolipid biosynthesis. One isolate from this population, GroD1, displayed a profound reduction in the synthesis of phosphatidylcholine, phosphatidylethanolamine, and triglycerides but presented high levels of phosphatidic acid and normal levels of phosphatidylinositol synthesis. This was accompanied by a reduction in phosphatidate phosphatase 1 (PAP1) activity. Expression cloning and sequencing of the cDNA obtained from GroD1 revealed a point mutation, Gly-189 --> Glu, in glucose-6-phosphate isomerase (GPI), a glycolytic enzyme involved in an inherited disorder that results in anemia and neuromuscular symptoms in humans. GPI activity was reduced by 87% in GroD1. No significant differences were found in DNA synthesis, protein synthesis, and ATP levels, whereas glycerol 3-phosphate levels were increased in the mutant. Expression of wild-type hamster GPI restored GPI activity, glycerolipid biosynthesis, and PAP1 activity in GroD1. Two additional, independently isolated GPI-deficient mutants displayed similar phenotypes with respect to PAP1 activity and glycerolipid biosynthesis. These findings uncover a novel relationship between GPI, involved in carbohydrate metabolism, and PAP1, a lipogenic enzyme. These results may also help to explain neuromuscular symptoms associated with inherited GPI deficiency.
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Affiliation(s)
- Jorge F Haller
- Department of Physiology and Biophysics, Boston University School of Medicine, Massachusetts 02118, USA
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