1
|
Akl MG, Baccetto R, Stebbings BM, Li L, Widenmaier SB. Euglycemia is affected by stress defense factor hepatocyte NRF1, but not NRF2. Biochem Biophys Res Commun 2023; 668:96-103. [PMID: 37245295 DOI: 10.1016/j.bbrc.2023.05.082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Accepted: 05/21/2023] [Indexed: 05/30/2023]
Abstract
Hepatocyte stress signaling has been established to alter glucose metabolism and impair systemic glucose homeostasis. In contrast, the role of stress defenses in the control of glucose homeostasis is less understood. Nuclear factor erythroid 2 related factor-1 (NRF1) and -2 (NRF2) are transcription factors that promote stress defense and can exert hepatocyte stress defense programming via complementary gene regulation. To identify whether there are independent or complementary roles of these factors in hepatocytes on glucose homeostasis, we investigated the effect of adult-onset, hepatocyte-specific deletion of NRF1, NRF2, or both on glycemia in mice fed 1-3 weeks with a mildly stressful diet enriched with fat, fructose, and cholesterol. Compared to respective control, NRF1 deficiency and combined deficiency reduced glycemia, in some cases resulting in hypoglycemia, whereas there was no effect of NRF2 deficiency. However, reduced glycemia in NRF1 deficiency did not occur in the leptin-deficient mouse model of obesity and diabetes, suggesting hepatocyte NRF1 support defenses that counteract hypoglycemia but does not promote hyperglycemia. Consistent with this, NRF1 deficiency was associated with reduced liver glycogen and glycogen synthase expression as well as marked alteration to circulating level of glycemia-influencing hormones, growth hormone and insulin-like growth factor-1 (IGF1). Overall, we identify a role for hepatocyte NRF1 in modulating glucose homeostasis, which may be linked to liver glycogen storage and the growth hormone/IGF1 axis.
Collapse
Affiliation(s)
- May G Akl
- Department of Anatomy, Physiology, and Pharmacology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada; Department of Physiology, Faculty of Medicine, University of Alexandria, Alexandria, Egypt
| | - Raquel Baccetto
- Department of Anatomy, Physiology, and Pharmacology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Brynne M Stebbings
- Department of Anatomy, Physiology, and Pharmacology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Lei Li
- Department of Anatomy, Physiology, and Pharmacology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Scott B Widenmaier
- Department of Anatomy, Physiology, and Pharmacology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
| |
Collapse
|
2
|
Akl MG, Li L, Baccetto R, Phanse S, Zhang Q, Trites MJ, McDonald S, Aoki H, Babu M, Widenmaier SB. Complementary gene regulation by NRF1 and NRF2 protects against hepatic cholesterol overload. Cell Rep 2023; 42:112872. [PMID: 37454293 DOI: 10.1016/j.celrep.2023.112872] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/18/2023] Open
|
3
|
Trites MJ, Stebbings BM, Aoki H, Phanse S, Akl MG, Li L, Babu M, Widenmaier SB. HDL functionality is dependent on hepatocyte stress defense factors Nrf1 and Nrf2. Front Physiol 2023; 14:1212785. [PMID: 37501930 PMCID: PMC10369849 DOI: 10.3389/fphys.2023.1212785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Accepted: 06/30/2023] [Indexed: 07/29/2023] Open
Abstract
High density lipoproteins (HDL) promote homeostasis and counteract stressful tissue damage that underlie cardiovascular and other diseases by mediating reverse cholesterol transport, reducing inflammation, and abrogating oxidative damage. However, metabolically stressful conditions associated with atherosclerosis can impair these effects. Hepatocytes play a major role in the genesis and maturation of circulating HDL, and liver stress elicits marked regulatory changes to circulating HDL abundance and composition, which affect its functionality. The mechanisms linking liver stress to HDL function are incompletely understood. In this study, we sought to determine whether stress defending transcription factors nuclear factor erythroid 2 related factor-1 (Nrf1) and -2 (Nrf2) promote hepatocyte production of functional HDL. Using genetically engineered mice briefly fed a mild metabolically stressful diet, we investigated the effect of hepatocyte-specific deletion of Nrf1, Nrf2, or both on circulating HDL cholesterol, protein composition, and function. Combined deletion, but not single gene deletion, reduced HDL cholesterol and apolipoprotein A1 levels as well as the capacity of HDL to accept cholesterol undergoing efflux from cultured macrophages and to counteract tumor necrosis factor α-induced inflammatory effect on cultured endothelial cells. This coincided with substantial alteration to the HDL proteome, which correlated with liver gene expression profiles of corresponding proteins. Thus, our findings show complementary actions by hepatocyte Nrf1 and Nrf2 play a role in shaping HDL abundance and composition to promote production of functionally viable HDL. Consequently, our study illuminates the possibility that enhancing stress defense programming in the liver may improve atheroprotective and perhaps other health promoting actions of HDL.
Collapse
Affiliation(s)
- Michael J. Trites
- Department of Anatomy, Physiology and Pharmacology, University of Saskatchewan, Saskatoon, SK, Canada
| | - Brynne M. Stebbings
- Department of Anatomy, Physiology and Pharmacology, University of Saskatchewan, Saskatoon, SK, Canada
| | - Hiroyuki Aoki
- Department of Biochemistry, University of Regina, Regina, SK, Canada
| | - Sadhna Phanse
- Department of Biochemistry, University of Regina, Regina, SK, Canada
| | - May G. Akl
- Department of Anatomy, Physiology and Pharmacology, University of Saskatchewan, Saskatoon, SK, Canada
- Department of Physiology, Faculty of Medicine, University of Alexandria, Alexandria, Egypt
| | - Lei Li
- Department of Anatomy, Physiology and Pharmacology, University of Saskatchewan, Saskatoon, SK, Canada
| | - Mohan Babu
- Department of Biochemistry, University of Regina, Regina, SK, Canada
| | - Scott B. Widenmaier
- Department of Anatomy, Physiology and Pharmacology, University of Saskatchewan, Saskatoon, SK, Canada
| |
Collapse
|
4
|
Akl MG, Li L, Baccetto R, Phanse S, Zhang Q, Trites MJ, McDonald S, Aoki H, Babu M, Widenmaier SB. Complementary gene regulation by NRF1 and NRF2 protects against hepatic cholesterol overload. Cell Rep 2023; 42:112399. [PMID: 37060561 DOI: 10.1016/j.celrep.2023.112399] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 10/04/2022] [Accepted: 03/30/2023] [Indexed: 04/16/2023] Open
Abstract
Hepatic cholesterol overload promotes steatohepatitis. Insufficient understanding of liver stress defense impedes therapy development. Here, we elucidate the role of stress defense transcription factors, nuclear factor erythroid 2 related factor-1 (NRF1) and -2 (NRF2), in counteracting cholesterol-linked liver stress. Using a diet that increases liver cholesterol storage, expression profiles and phenotypes of liver from mice with hepatocyte deficiency of NRF1, NRF2, or both are compared with controls, and chromatin immunoprecipitation sequencing is undertaken to identify target genes. Results show NRF1 and NRF2 co-regulate genes that eliminate cholesterol and mitigate inflammation and oxidative damage. Combined deficiency, but not deficiency of either alone, results in severe steatohepatitis, hepatic cholesterol overload and crystallization, altered bile acid metabolism, and decreased biliary cholesterol. Moreover, therapeutic effects of NRF2-activating drug bardoxolone require NRF1 and are supplemented by NRF1 overexpression. Thus, we discover complementary gene programming by NRF1 and NRF2 that counteract cholesterol-associated fatty liver disease progression.
Collapse
Affiliation(s)
- May G Akl
- Department of Anatomy, Physiology, and Pharmacology, University of Saskatchewan, Saskatoon, SK, Canada; Department of Physiology, Faculty of Medicine, University of Alexandria, Alexandria, Egypt
| | - Lei Li
- Department of Anatomy, Physiology, and Pharmacology, University of Saskatchewan, Saskatoon, SK, Canada
| | - Raquel Baccetto
- Department of Anatomy, Physiology, and Pharmacology, University of Saskatchewan, Saskatoon, SK, Canada
| | - Sadhna Phanse
- Department of Chemistry and Biochemistry, University of Regina, Regina, SK, Canada
| | - Qingzhou Zhang
- Department of Chemistry and Biochemistry, University of Regina, Regina, SK, Canada
| | - Michael J Trites
- Department of Anatomy, Physiology, and Pharmacology, University of Saskatchewan, Saskatoon, SK, Canada
| | - Sherin McDonald
- Department of Anatomy, Physiology, and Pharmacology, University of Saskatchewan, Saskatoon, SK, Canada
| | - Hiroyuki Aoki
- Department of Chemistry and Biochemistry, University of Regina, Regina, SK, Canada
| | - Mohan Babu
- Department of Chemistry and Biochemistry, University of Regina, Regina, SK, Canada
| | - Scott B Widenmaier
- Department of Anatomy, Physiology, and Pharmacology, University of Saskatchewan, Saskatoon, SK, Canada.
| |
Collapse
|
5
|
Akl MG, Widenmaier SB. Immunometabolic factors contributing to obesity-linked hepatocellular carcinoma. Front Cell Dev Biol 2023; 10:1089124. [PMID: 36712976 PMCID: PMC9877434 DOI: 10.3389/fcell.2022.1089124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Accepted: 12/27/2022] [Indexed: 01/15/2023] Open
Abstract
Hepatocellular carcinoma (HCC) is a major public health concern that is promoted by obesity and associated liver complications. Onset and progression of HCC in obesity is a multifactorial process involving complex interactions between the metabolic and immune system, in which chronic liver damage resulting from metabolic and inflammatory insults trigger carcinogenesis-promoting gene mutations and tumor metabolism. Moreover, cell growth and proliferation of the cancerous cell, after initiation, requires interactions between various immunological and metabolic pathways that provide stress defense of the cancer cell as well as strategic cell death escape mechanisms. The heterogenic nature of HCC in addition to the various metabolic risk factors underlying HCC development have led researchers to focus on examining metabolic pathways that may contribute to HCC development. In obesity-linked HCC, oncogene-induced modifications and metabolic pathways have been identified to support anabolic demands of the growing HCC cells and combat the concomitant cell stress, coinciding with altered utilization of signaling pathways and metabolic fuels involved in glucose metabolism, macromolecule synthesis, stress defense, and redox homeostasis. In this review, we discuss metabolic insults that can underlie the transition from steatosis to steatohepatitis and from steatohepatitis to HCC as well as aberrantly regulated immunometabolic pathways that enable cancer cells to survive and proliferate in the tumor microenvironment. We also discuss therapeutic modalities targeted at HCC prevention and regression. A full understanding of HCC-associated immunometabolic changes in obesity may contribute to clinical treatments that effectively target cancer metabolism.
Collapse
Affiliation(s)
- May G. Akl
- Department of Anatomy, Physiology, and Pharmacology, University of Saskatchewan, Saskatoon, SK, Canada,Department of Physiology, University of Alexandria, Alexandria, Egypt
| | - Scott B. Widenmaier
- Department of Anatomy, Physiology, and Pharmacology, University of Saskatchewan, Saskatoon, SK, Canada,*Correspondence: Scott B. Widenmaier,
| |
Collapse
|
6
|
Abstract
The proper production, degradation, folding and activity of proteins, proteostasis, is essential for any cellular function. From single cell organisms to humans, selective pressures have led to the evolution of adaptive programs that ensure proteins are properly produced and disposed of when necessary. Environmental factors such as temperature, nutrient availability, pathogens as well as predators have greatly influenced the development of mechanisms such as the unfolded protein response, endoplasmic reticulum-associated protein degradation and autophagy, working together in concert to secure cellular proteostasis. In our modern society, the metabolic systems of the human body face the distinct challenge of changed diets, chronic overnutrition and sedentary lifestyles. Obesity and excess white adipose tissue accumulation are linked to a cluster of metabolic diseases and disturbed proteostasis is a common feature. Conversely, processes that promote energy expenditure such as exercise, shivering as well as non-shivering thermogenesis by brown adipose tissue (BAT) and beige adipocytes counteract metabolic dysfunction. Here we review the basic concepts of proteostasis in obesity-linked metabolic diseases and focus on adipocytes, which are critical regulators of mammalian energy metabolism.
Collapse
Affiliation(s)
- Alexander Bartelt
- Institute for Cardiovascular Prevention (IPEK), Ludwig Maximilians University, Pettenkoferstr. 9, D-81377 Munich, Germany
- German Center for Cardiovascular Research (DZHK), Partner Site Munich Heart Alliance, Technische Universität München, Biedersteiner Straße 29, D-80802 Munich, Germany
- Institute for Diabetes and Cancer (IDC), Helmholtz Center Munich, Ingolstädter Landstraße 1, D-85764 Neuherberg, Germany
- Department of Molecular Metabolism, Harvard T.H. Chan School of Public Health, 665 Huntington Avenue, Boston MA 02115, USA
| | - Scott B Widenmaier
- Department of Anatomy, Physiology and Pharmacology in the College of Medicine, University of Saskatchewan, 107 Wiggins Rd, Saskatchewan, S7N 5E5 Saskatoon, Canada
| |
Collapse
|
7
|
Bartelt A, Widenmaier SB, Schlein C, Johann K, Goncalves RLS, Eguchi K, Fischer AW, Parlakgül G, Snyder NA, Nguyen TB, Bruns OT, Franke D, Bawendi MG, Lynes MD, Leiria LO, Tseng YH, Inouye KE, Arruda AP, Hotamisligil GS. Brown adipose tissue thermogenic adaptation requires Nrf1-mediated proteasomal activity. Nat Med 2018; 24:292-303. [PMID: 29400713 PMCID: PMC5839993 DOI: 10.1038/nm.4481] [Citation(s) in RCA: 117] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Accepted: 01/02/2018] [Indexed: 12/14/2022]
Abstract
Adipocytes possess remarkable adaptive capacity to respond to nutrient excess, fasting or cold exposure, and they are thus an important cell type for the maintenance of proper metabolic health. Although the endoplasmic reticulum (ER) is a critical organelle for cellular homeostasis, the mechanisms that mediate adaptation of the ER to metabolic challenges in adipocytes are unclear. Here we show that brown adipose tissue (BAT) thermogenic function requires an adaptive increase in proteasomal activity to secure cellular protein quality control, and we identify the ER-localized transcription factor nuclear factor erythroid 2-like 1 (Nfe2l1, also known as Nrf1) as a critical driver of this process. We show that cold adaptation induces Nrf1 in BAT to increase proteasomal activity and that this is crucial for maintaining ER homeostasis and cellular integrity, specifically when the cells are in a state of high thermogenic activity. In mice, under thermogenic conditions, brown-adipocyte-specific deletion of Nfe2l1 (Nrf1) resulted in ER stress, tissue inflammation, markedly diminished mitochondrial function and whitening of the BAT. In mouse models of both genetic and dietary obesity, stimulation of proteasomal activity by exogenously expressing Nrf1 or by treatment with the proteasome activator PA28α in BAT resulted in improved insulin sensitivity. In conclusion, Nrf1 emerges as a novel guardian of brown adipocyte function, providing increased proteometabolic quality control for adapting to cold or to obesity.
Collapse
Affiliation(s)
- Alexander Bartelt
- Department of Genetics and Complex Diseases and Sabri Ülker Center, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
| | - Scott B Widenmaier
- Department of Genetics and Complex Diseases and Sabri Ülker Center, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
| | - Christian Schlein
- Department of Genetics and Complex Diseases and Sabri Ülker Center, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
| | - Kornelia Johann
- Department of Genetics and Complex Diseases and Sabri Ülker Center, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
| | - Renata L S Goncalves
- Department of Genetics and Complex Diseases and Sabri Ülker Center, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
| | - Kosei Eguchi
- Department of Genetics and Complex Diseases and Sabri Ülker Center, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
| | - Alexander W Fischer
- Department of Genetics and Complex Diseases and Sabri Ülker Center, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
| | - Günes Parlakgül
- Department of Genetics and Complex Diseases and Sabri Ülker Center, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
| | - Nicole A Snyder
- Department of Genetics and Complex Diseases and Sabri Ülker Center, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
| | - Truc B Nguyen
- Department of Genetics and Complex Diseases and Sabri Ülker Center, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
| | - Oliver T Bruns
- Department of Chemistry, Massachusetts Institute of Technology (MIT), Cambridge, Massachusetts, USA
| | - Daniel Franke
- Department of Chemistry, Massachusetts Institute of Technology (MIT), Cambridge, Massachusetts, USA
| | - Moungi G Bawendi
- Department of Chemistry, Massachusetts Institute of Technology (MIT), Cambridge, Massachusetts, USA
| | - Matthew D Lynes
- Section on Integrative Physiology and Metabolism, Research Division, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts, USA
| | - Luiz O Leiria
- Section on Integrative Physiology and Metabolism, Research Division, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts, USA
| | - Yu-Hua Tseng
- Section on Integrative Physiology and Metabolism, Research Division, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts, USA
| | - Karen E Inouye
- Department of Genetics and Complex Diseases and Sabri Ülker Center, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
| | - Ana Paula Arruda
- Department of Genetics and Complex Diseases and Sabri Ülker Center, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
| | - Gökhan S Hotamisligil
- Department of Genetics and Complex Diseases and Sabri Ülker Center, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
- Broad Institute of Harvard and MIT, Cambridge, Massachusetts, USA
| |
Collapse
|
8
|
Widenmaier SB, Snyder NA, Nguyen TB, Arduini A, Lee GY, Arruda AP, Saksi J, Bartelt A, Hotamisligil GS. NRF1 Is an ER Membrane Sensor that Is Central to Cholesterol Homeostasis. Cell 2017; 171:1094-1109.e15. [DOI: 10.1016/j.cell.2017.10.003] [Citation(s) in RCA: 94] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Revised: 08/14/2017] [Accepted: 09/30/2017] [Indexed: 12/13/2022]
|
9
|
Abstract
Chronic metabolic challenges have severe consequences on physiological systems. In this issue of Immunity, Ito et al. (2016) show that defects in cholesterol metabolism in CD11c+ immune cells result in impaired antigen presentation and ultimately in autoimmune disease.
Collapse
Affiliation(s)
- Scott B Widenmaier
- Department of Genetics and Complex Diseases and Sabri Ülker Center, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA
| | - Gökhan S Hotamışlıgil
- Department of Genetics and Complex Diseases and Sabri Ülker Center, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA; Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA.
| |
Collapse
|
10
|
Abstract
B-cell lymphoma 2 (Bcl-2) family proteins are established regulators of cell survival, but their involvement in the normal function of primary cells has only recently begun to receive attention. In this study, we demonstrate that chemical and genetic loss-of-function of antiapoptotic Bcl-2 and Bcl-x(L) significantly augments glucose-dependent metabolic and Ca(2+) signals in primary pancreatic β-cells. Antagonism of Bcl-2/Bcl-x(L) by two distinct small-molecule compounds rapidly hyperpolarized β-cell mitochondria, increased cytosolic Ca(2+), and stimulated insulin release via the ATP-dependent pathway in β-cell under substimulatory glucose conditions. Experiments with single and double Bax-Bak knockout β-cells established that this occurred independently of these proapoptotic binding partners. Pancreatic β-cells from Bcl-2(-/-) mice responded to glucose with significantly increased NAD(P)H levels and cytosolic Ca(2+) signals, as well as significantly augmented insulin secretion. Inducible deletion of Bcl-x(L) in adult mouse β-cells also increased glucose-stimulated NAD(P)H and Ca(2+) responses and resulted in an improvement of in vivo glucose tolerance in the conditional Bcl-x(L) knockout animals. Our work suggests that prosurvival Bcl proteins normally dampen the β-cell response to glucose and thus reveals these core apoptosis proteins as integrators of cell death and physiology in pancreatic β-cells.
Collapse
Affiliation(s)
- Dan S. Luciani
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Surgery, University of British Columbia, Vancouver, British Columbia, Canada
- Child & Family Research Institute, Vancouver, British Columbia, Canada
- Corresponding authors: James D. Johnson, , and Dan S. Luciani,
| | - Sarah A. White
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Surgery, University of British Columbia, Vancouver, British Columbia, Canada
- Child & Family Research Institute, Vancouver, British Columbia, Canada
| | - Scott B. Widenmaier
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Varun V. Saran
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada the
- University of British Columbia James Hogg Research Centre, St. Paul's Hospital, Vancouver, British Columbia, Canada
| | - Farnaz Taghizadeh
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Xiaoke Hu
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Michael F. Allard
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada the
- University of British Columbia James Hogg Research Centre, St. Paul's Hospital, Vancouver, British Columbia, Canada
| | - James D. Johnson
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Surgery, University of British Columbia, Vancouver, British Columbia, Canada
- Corresponding authors: James D. Johnson, , and Dan S. Luciani,
| |
Collapse
|
11
|
Kim SJ, Widenmaier SB, Choi WS, Nian C, Ao Z, Warnock G, McIntosh CHS. Pancreatic β-cell prosurvival effects of the incretin hormones involve post-translational modification of Kv2.1 delayed rectifier channels. Cell Death Differ 2011; 19:333-44. [PMID: 21818121 DOI: 10.1038/cdd.2011.102] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are the major incretin hormones that exert insulinotropic and anti-apoptotic actions on pancreatic β-cells. Insulinotropic actions of the incretins involve modulation of voltage-gated potassium (Kv) channels. In multiple cell types, Kv channel activity has been implicated in cell volume changes accompanying initiation of the apoptotic program. Focusing on Kv2.1, we examined whether regulation of Kv channels in β-cells contributes to the prosurvival effects of incretins. Overexpression of Kv2.1 in INS-1 β-cells potentiated apoptosis in response to mitochondrial and ER stress and, conversely, co-stimulation with GIP/GLP-1 uncoupled this potentiation, suppressing apoptosis. In parallel, incretins promoted phosphorylation and acetylation of Kv2.1 via pathways involving protein kinase A (PKA)/mitogen- and stress-activated kinase-1 (MSK-1) and histone acetyltransferase (HAT)/histone deacetylase (HDAC). Further studies demonstrated that acetylation of Kv2.1 was mediated by incretin actions on nuclear/cytoplasmic shuttling of CREB binding protein (CBP) and its interaction with Kv2.1. Regulation of β-cell survival by GIP and GLP-1 therefore involves post-translational modifications (PTMs) of Kv channels by PKA/MSK-1 and HAT/HDAC. This appears to be the first demonstration of modulation of delayed rectifier Kv channels contributing to the β-cell prosurvival effects of incretins and of 7-transmembrane G protein-coupled receptor (GPCR)-stimulated export of a nuclear lysine acetyltransferase that regulates cell surface ion channel function.
Collapse
Affiliation(s)
- S-J Kim
- Departments of Cellular & Physiological Sciences and the Diabetes Research Group, Life Sciences Institute, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, Canada
| | | | | | | | | | | | | |
Collapse
|
12
|
Widenmaier SB, Ao Z, Kim SJ, Warnock G, McIntosh CHS. Suppression of p38 MAPK and JNK via Akt-mediated inhibition of apoptosis signal-regulating kinase 1 constitutes a core component of the beta-cell pro-survival effects of glucose-dependent insulinotropic polypeptide. J Biol Chem 2009; 284:30372-82. [PMID: 19748889 DOI: 10.1074/jbc.m109.060178] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Glucose-dependent insulinotropic polypeptide (GIP) potentiates glucose-stimulated insulin secretion, insulin biosynthesis, and beta-cell proliferation and survival. In previous studies GIP was shown to promote beta-cell survival by modulating the activity of multiple signaling modules and regulating gene transcription of pro- and anti-apoptotic bcl-2 family proteins. We have now evaluated the mechanisms by which GIP regulates the dynamic interactions between cytoplasmic bcl-2 family members and the mitochondria in INS-1 cells during apoptosis induced by treatment with staurosporine (STS), an activator of the mitochondria-mediated apoptotic pathway. STS induced translocation of bad and bimEL, activation of mitochondrial bax, release of mitochondrial cytochrome c, cleavage of caspase-3, and apoptosis. Each response was significantly diminished by GIP. Using selective enzyme inhibitors, overexpression of dominant-negative Akt, and Akt siRNA, it was demonstrated that GIP promoted beta-cell survival via Akt-dependent suppression of p38 MAPK and JNK and that combined inhibition was sufficient to explain the entire pro-survival responses to GIP during STS treatment. This signaling pathway also explained the pro-survival effects of GIP on INS-1 cells exposed to two other promoters of stress: thapsigargin (endoplasmic reticulum stress) and etoposide (genotoxic stress). Importantly, we discovered that GIP suppressed p38 MAPK and JNK via Akt-mediated changes in the phosphorylation state of the apoptosis signal-regulating kinase 1 in INS-1 cells and human islets, resulting in inhibition of its activity. Inhibition of apoptosis by GIP is therefore mediated via a key pathway involving Akt-dependent inhibition of apoptosis signal-regulating kinase 1, which subsequently prevents the pro-apoptotic actions of p38 MAPK and JNK.
Collapse
Affiliation(s)
- Scott B Widenmaier
- Department of Cellular and Physiological Sciences and the Diabetes Research Group, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | | | | | | | | |
Collapse
|
13
|
Widenmaier SB, Sampaio AV, Underhill TM, McIntosh CHS. Noncanonical activation of Akt/protein kinase B in {beta}-cells by the incretin hormone glucose-dependent insulinotropic polypeptide. J Biol Chem 2009; 284:10764-73. [PMID: 19233842 DOI: 10.1074/jbc.m809116200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Therapeutics based on the actions of the incretin hormones, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), have recently been introduced for the treatment of type 2 diabetes mellitus. The serine/threonine kinase Akt is a major mediator of incretin action on the pancreatic islet, increasing beta-cell mass and function and promoting beta-cell survival. The mechanisms underlying incretin activation of Akt are thought to involve an essential phosphoinositide 3-kinase-mediated phosphorylation of threonine 308, similar to the prototypical Akt activator, insulin-like growth factor-I (IGF-I). In this study, using activity assays on immunoprecipitated Akt, we discovered that GIP and GLP-1 were capable of stimulating Akt in the INS-1 beta-cell line and isolated mouse islets via a mechanism that did not require phosphoinositide 3-kinase or phosphorylation of Thr(308) and Ser(473), and this pathway involved the production of cAMP. Furthermore, we found that GIP stimulated anti-apoptotic signaling via this alternate mode of Akt activation. We conclude that incretins can activate Akt via a novel noncanonical mechanism that may provide an alternative therapeutic target for the treatment of type 2 diabetes mellitus and have broader implications for Akt physiology in human health and disease.
Collapse
Affiliation(s)
- Scott B Widenmaier
- Department of Cellular and Physiological Sciences and the Diabetes Research Group, Life Sciences Institute, University of British Columbia, Vancouver V6T 1Z3, Canada
| | | | | | | |
Collapse
|
14
|
Matz CJ, Christensen MR, Bone AD, Gress CD, Widenmaier SB, Weger HG. Only iron-limited cells of the cyanobacteriumAnabaena flos-aquaeinhibit growth of the green algaChlamydomonas reinhardtii. ACTA ACUST UNITED AC 2004. [DOI: 10.1139/b04-022] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cocultivation of iron-limited cells of the cyanobacterium Anabaena flos-aquae (Lyng.) Brèb. and the green alga Chlamydomonas reinhardtii Dangeard resulted in growth of Anabaena but not Chlamydomonas, even in the presence of excess exogenous iron. This effect was also observed during the cultivation of Chlamydomonas in a medium in which iron-limited Anabaena cells had been growing, but were removed prior to culture of Chlamydomonas. Conversely, iron-limited Chlamydomonas cells grew very well in medium from iron (nutrient)-sufficient, phosphate-limited, and nitrogen-limited Anabaena cultures. Iron-limited Anabaena cultures produced siderophores, while the other types of Anabaena cultures did not. Treatment of Anabaena iron-limited medium with activated charcoal completely removed the inhibitory effect on Chlamydomonas growth, and boiling the medium removed most of the inhibitory effect. Both the charcoal and the boiling treatments also removed siderophores from the medium. Partially purified Anabaena siderophore preparations were also inhibitory to Chlamydomonas growth. The inhibitory effect of iron-limited Anabaena medium could be partially overcome by addition of excess micronutrients (especially cobalt copper) but not by addition of iron. We suggest that Anabaena-derived siderophores, present only in iron-limited Anabaena medium, inhibit the growth of Chlamydomonas cells via a previously uncharacterized toxicity. This effect is different from previously described experiments in which cyanobacterial siderophores suppressed green algal growth via competition for limiting amounts of iron.Key words: Anabaena, Chlamydomonas, cocultivation, iron limitation, micronutrients; siderophores.
Collapse
|