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Li Y, Tang Y, Shi S, Gao S, Wang Y, Xiao D, Chen T, He Q, Zhang J, Lin Y. Tetrahedral Framework Nucleic Acids Ameliorate Insulin Resistance in Type 2 Diabetes Mellitus via the PI3K/Akt Pathway. ACS APPLIED MATERIALS & INTERFACES 2021; 13:40354-40364. [PMID: 34410099 DOI: 10.1021/acsami.1c11468] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Insulin resistance (IR) is one of the essential conditions in the development of type 2 diabetes mellitus (T2DM). IR occurs in hepatic cells when the insulin receptor substrate-1 (IRS-1)/phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) signaling pathway is downregulated; thus, activating this pathway can significantly improve insulin sensitivity and ameliorate T2DM. Tetrahedral framework nucleic acids (tFNAs), a DNA nanomaterial, are synthesized from four single-stranded DNA molecules. tFNAs possess excellent biocompatibility and good water solubility and stability. tFNAs can promote cell proliferation, cell autophagy, wound healing, and nerve regeneration by activating the PI3K/Akt pathway. Herein, we explore the effects and underlying mechanisms of tFNAs on IR. The results displayed that tFNAs could increase glucose uptake and ameliorate IR by activating the IRS-1/PI3K/Akt pathway in glucosamine (GlcN)-stimulated HepG2 cells. By employing a PI3K inhibitor, we confirmed that tFNAs reduce IR through the PI3K/Akt pathway. Moreover, tFNAs can promote hepatic cell proliferation and inhibit GlcN-induced cell apoptosis. In a T2DM mouse model, tFNAs reduce blood glucose levels and ameliorate hepatic IR via the PI3K/Akt pathway. Taken together, tFNAs can improve hepatic IR and alleviate T2DM through the PI3K/Akt pathway, making contribution to the potential application of tFNAs in T2DM.
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Affiliation(s)
- Yanjing Li
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, P. R. China
- Department of Prosthodontics, Tianjin Medical University School of Stomatology, Tianjin 300070, P. R. China
| | - Yuanlin Tang
- West China Medical Center, Sichuan University, Chengdu 610041, P. R. China
| | - Sirong Shi
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, P. R. China
| | - Shaojingya Gao
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, P. R. China
| | - Yun Wang
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, P. R. China
| | - Dexuan Xiao
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, P. R. China
| | - Tianyu Chen
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, P. R. China
| | - Qing He
- Department of Oral and Maxillofacial Surgery, Hospital of Stomatology, Southwest Medical University, Luzhou 646000, P. R. China
| | - Junjiang Zhang
- Department of Prosthodontics, Tianjin Medical University School of Stomatology, Tianjin 300070, P. R. China
| | - Yunfeng Lin
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, P. R. China
- West China Medical Center, Sichuan University, Chengdu 610041, P. R. China
- College of Biomedical Engineering, Sichuan University, Chengdu 610041, P. R. China
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2
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Ikushima YM, Awazawa M, Kobayashi N, Osonoi S, Takemiya S, Kobayashi H, Suwanai H, Morimoto Y, Soeda K, Adachi J, Muratani M, Charron J, Mizukami H, Takahashi N, Ueki K. MEK/ERK Signaling in β-Cells Bifunctionally Regulates β-Cell Mass and Glucose-Stimulated Insulin Secretion Response to Maintain Glucose Homeostasis. Diabetes 2021; 70:1519-1535. [PMID: 33906910 DOI: 10.2337/db20-1295] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Accepted: 04/23/2021] [Indexed: 11/13/2022]
Abstract
In diabetic pathology, insufficiency in β-cell mass, unable to meet peripheral insulin demand, and functional defects of individual β-cells in production of insulin are often concurrently observed, collectively causing hyperglycemia. Here we show that the phosphorylation of ERK1/2 is significantly decreased in the islets of db/db mice as well as in those of a cohort of subjects with type 2 diabetes. In mice with abrogation of ERK signaling in pancreatic β-cells through deletion of Mek1 and Mek2, glucose intolerance aggravates under high-fat diet-feeding conditions due to insufficient insulin production with lower β-cell proliferation and reduced β-cell mass, while in individual β-cells dampening of the number of insulin exocytosis events is observed, with the molecules involved in insulin exocytosis being less phosphorylated. These data reveal bifunctional roles for MEK/ERK signaling in β-cells for glucose homeostasis, i.e., in regulating β-cell mass as well as in controlling insulin exocytosis in individual β-cells, thus providing not only a novel perspective for the understanding of diabetes pathophysiology but also a potential clue for new drug development for diabetes treatment.
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Affiliation(s)
- Yoshiko Matsumoto Ikushima
- Department of Molecular Diabetic Medicine, Diabetes Research Center, Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
| | - Motoharu Awazawa
- Department of Molecular Diabetic Medicine, Diabetes Research Center, Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
| | - Naoki Kobayashi
- Department of Molecular Diabetic Medicine, Diabetes Research Center, Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
| | - Sho Osonoi
- Department of Pathology and Molecular Medicine, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
| | - Seiichi Takemiya
- Department of Molecular Diabetic Medicine, Diabetes Research Center, Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
| | - Hiroshi Kobayashi
- Department of Stem Cell Biology, Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
| | - Hirotsugu Suwanai
- Department of Diabetes, Metabolism and Endocrinology, Tokyo Medical University, Tokyo, Japan
| | - Yuichi Morimoto
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
- International Research Center for Neurointelligence (WPI-IRCN), University of Tokyo Institutes for Advanced Study (UTIAS), The University of Tokyo, Tokyo, Japan
| | - Kotaro Soeda
- Department of Molecular Diabetic Medicine, Diabetes Research Center, Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
| | - Jun Adachi
- Laboratory of Proteome Research, Laboratory of Proteomics for Drug Discovery, Center for Drug Design Research, National Institutes of Biomedical Innovation, Health and Nutrition, Osaka, Japan
| | - Masafumi Muratani
- Department of Genome Biology, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Jean Charron
- Centre de Recherche sur le Cancer de l'Université Laval, L'Hôtel-Dieu de Québec, Quebec City, Quebec, Canada
| | - Hiroki Mizukami
- Department of Pathology and Molecular Medicine, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
| | - Noriko Takahashi
- Department of Physiology, Kitasato University School of Medicine, Sagamihara, Japan
| | - Kohjiro Ueki
- Department of Molecular Diabetic Medicine, Diabetes Research Center, Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
- Department of Molecular Diabetology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
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3
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Sasako T, Ohsugi M, Kubota N, Itoh S, Okazaki Y, Terai A, Kubota T, Yamashita S, Nakatsukasa K, Kamura T, Iwayama K, Tokuyama K, Kiyonari H, Furuta Y, Shibahara J, Fukayama M, Enooku K, Okushin K, Tsutsumi T, Tateishi R, Tobe K, Asahara H, Koike K, Kadowaki T, Ueki K. Hepatic Sdf2l1 controls feeding-induced ER stress and regulates metabolism. Nat Commun 2019; 10:947. [PMID: 30814508 PMCID: PMC6393527 DOI: 10.1038/s41467-019-08591-6] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Accepted: 01/15/2019] [Indexed: 01/11/2023] Open
Abstract
Dynamic metabolic changes occur in the liver during the transition between fasting and feeding. Here we show that transient ER stress responses in the liver following feeding terminated by Sdf2l1 are essential for normal glucose and lipid homeostasis. Sdf2l1 regulates ERAD through interaction with a trafficking protein, TMED10. Suppression of Sdf2l1 expression in the liver results in insulin resistance and increases triglyceride content with sustained ER stress. In obese and diabetic mice, Sdf2l1 is downregulated due to decreased levels of nuclear XBP-1s, whereas restoration of Sdf2l1 expression ameliorates glucose intolerance and fatty liver with decreased ER stress. In diabetic patients, insufficient induction of Sdf2l1 correlates with progression of insulin resistance and steatohepatitis. Therefore, failure to build an ER stress response in the liver may be a causal factor in obesity-related diabetes and nonalcoholic steatohepatitis, for which Sdf2l1 could serve as a therapeutic target and sensitive biomarker.
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Affiliation(s)
- Takayoshi Sasako
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-8655, Japan.,Translational Systems Biology and Medicine Initiative (TSBMI), The University of Tokyo, Tokyo, 113-8655, Japan.,Department of Molecular Diabetic Medicine, Diabetes Research Center, National Center for Global Health and Medicine, Tokyo, 162-8655, Japan.,Division for Health Service Promotion, The University of Tokyo, Tokyo, 113-0033, Japan.,Department of Molecular Sciences on Diabetes, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-8655, Japan
| | - Mitsuru Ohsugi
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-8655, Japan
| | - Naoto Kubota
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-8655, Japan.,Translational Systems Biology and Medicine Initiative (TSBMI), The University of Tokyo, Tokyo, 113-8655, Japan.,Department of Clinical Nutrition Therapy, The University of Tokyo Hospital, The University of Tokyo, Tokyo, 113-865, Japan
| | - Shinsuke Itoh
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-8655, Japan.,Kowa Company Limited, Nagoya, 460-0003, Japan
| | - Yukiko Okazaki
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-8655, Japan.,Department of Molecular Diabetic Medicine, Diabetes Research Center, National Center for Global Health and Medicine, Tokyo, 162-8655, Japan
| | - Ai Terai
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-8655, Japan.,Department of Molecular Diabetic Medicine, Diabetes Research Center, National Center for Global Health and Medicine, Tokyo, 162-8655, Japan
| | - Tetsuya Kubota
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-8655, Japan.,Clinical Nutrition Program, National Institute of Health and Nutrition, Tokyo, 162-8636, Japan.,Division of Cardiovascular Medicine, Toho University Ohashi Medical Center, Tokyo, 143-8541, Japan
| | - Satoshi Yamashita
- Department of Systems BioMedicine, Tokyo Medical and Dental University, Tokyo, 113-8510, Japan
| | - Kunio Nakatsukasa
- Division of Biological Sciences, Graduate School of Science, Nagoya University, Nagoya, 464-8601, Japan.,Graduate School of Natural Sciences, Nagoya City University, Nagoya, 464-8601, Japan
| | - Takumi Kamura
- Division of Biological Sciences, Graduate School of Science, Nagoya University, Nagoya, 464-8601, Japan
| | - Kaito Iwayama
- Graduate School of Comprehensive Human Science, University of Tsukuba, Tsukuba, 305-8577, Japan
| | - Kumpei Tokuyama
- Graduate School of Comprehensive Human Science, University of Tsukuba, Tsukuba, 305-8577, Japan
| | - Hiroshi Kiyonari
- Animal Resource Development Unit, RIKEN Center for Life Science Technologies, Kobe, 650-0047, Japan.,Genetic Engineering Team, RIKEN Center for Life Science Technologies, Kobe, 650-0047, Japan
| | - Yasuhide Furuta
- Animal Resource Development Unit, RIKEN Center for Life Science Technologies, Kobe, 650-0047, Japan.,Genetic Engineering Team, RIKEN Center for Life Science Technologies, Kobe, 650-0047, Japan
| | - Junji Shibahara
- Department of Pathology, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-8655, Japan
| | - Masashi Fukayama
- Department of Pathology, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-8655, Japan
| | - Kenichiro Enooku
- Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-8655, Japan
| | - Kazuya Okushin
- Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-8655, Japan
| | - Takeya Tsutsumi
- Department of Infectious Disease, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-8655, Japan
| | - Ryosuke Tateishi
- Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-8655, Japan
| | - Kazuyuki Tobe
- The First Department of Internal Medicine, Graduate School of Medicine and Pharmaceutical Sciences of Research, The University of Toyama, Toyama, 930-8555, Japan
| | - Hiroshi Asahara
- Department of Systems BioMedicine, Tokyo Medical and Dental University, Tokyo, 113-8510, Japan
| | - Kazuhiko Koike
- Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-8655, Japan
| | - Takashi Kadowaki
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-8655, Japan. .,Translational Systems Biology and Medicine Initiative (TSBMI), The University of Tokyo, Tokyo, 113-8655, Japan. .,Department of Prevention of Diabetes and Lifestyle-Related Diseases, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-8655, Japan. .,Department of Metabolism and Nutrition, Mizonokuchi Hospital, Faculty of Medicine, Teikyo University, Tokyo, 213-8507, Japan.
| | - Kohjiro Ueki
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-8655, Japan. .,Translational Systems Biology and Medicine Initiative (TSBMI), The University of Tokyo, Tokyo, 113-8655, Japan. .,Department of Molecular Diabetic Medicine, Diabetes Research Center, National Center for Global Health and Medicine, Tokyo, 162-8655, Japan.
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4
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Chawla B, Hedman AC, Sayedyahossein S, Erdemir HH, Li Z, Sacks DB. Absence of IQGAP1 Protein Leads to Insulin Resistance. J Biol Chem 2017; 292:3273-3289. [PMID: 28082684 DOI: 10.1074/jbc.m116.752642] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Revised: 01/10/2017] [Indexed: 11/06/2022] Open
Abstract
Insulin binds to the insulin receptor (IR) and induces tyrosine phosphorylation of the receptor and insulin receptor substrate-1 (IRS-1), leading to activation of the PKB/Akt and MAPK/ERK pathways. IQGAP1 is a scaffold protein that interacts with multiple binding partners and integrates diverse signaling cascades. Here we show that IQGAP1 associates with both IR and IRS-1 and influences insulin action. In vitro analysis with pure proteins revealed that the IQ region of IQGAP1 binds directly to the intracellular domain of IR. Similarly, the phosphotyrosine-binding domain of IRS-1 mediates a direct interaction with the C-terminal tail of IQGAP1. Consistent with these observations, both IR and IRS-1 co-immunoprecipitated with IQGAP1 from cells. Investigation of the functional effects of the interactions revealed that in the absence of IQGAP1, insulin-stimulated phosphorylation of Akt and ERK, as well as the association of phosphatidylinositol 3-kinase with IRS-1, were significantly decreased. Importantly, loss of IQGAP1 results in impaired insulin signaling and glucose homeostasis in vivo Collectively, these data reveal that IQGAP1 is a scaffold for IR and IRS-1 and implicate IQGAP1 as a participant in insulin signaling.
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Affiliation(s)
- Bhavna Chawla
- Department of Laboratory Medicine, National Institutes of Health, Bethesda, Maryland 20892
| | - Andrew C Hedman
- Department of Laboratory Medicine, National Institutes of Health, Bethesda, Maryland 20892
| | - Samar Sayedyahossein
- Department of Laboratory Medicine, National Institutes of Health, Bethesda, Maryland 20892
| | - Huseyin H Erdemir
- Department of Laboratory Medicine, National Institutes of Health, Bethesda, Maryland 20892
| | - Zhigang Li
- Department of Laboratory Medicine, National Institutes of Health, Bethesda, Maryland 20892
| | - David B Sacks
- Department of Laboratory Medicine, National Institutes of Health, Bethesda, Maryland 20892.
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5
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Li H, Ma Y, Xu W, Chen H, Day L. MFG-E8 protein promotes C2C12myogenic differentiation by enhancing PI3K/Akt signaling. NEW J CHEM 2017. [DOI: 10.1039/c7nj02216f] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The effect of MFG-E8 on C2C12cell differentiation was analysed by immunocytochemistry, qRT-PCR and Western blot.
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Affiliation(s)
- He Li
- School of Chemistry and Chemical Engineering
- Harbin Institute of Technology
- Harbin 150090
- P. R. China
| | - Ying Ma
- School of Chemistry and Chemical Engineering
- Harbin Institute of Technology
- Harbin 150090
- P. R. China
| | - Weili Xu
- School of Chemistry and Chemical Engineering
- Harbin Institute of Technology
- Harbin 150090
- P. R. China
| | - Haoran Chen
- School of Chemistry and Chemical Engineering
- Harbin Institute of Technology
- Harbin 150090
- P. R. China
| | - Li Day
- School of Chemistry and Chemical Engineering
- Harbin Institute of Technology
- Harbin 150090
- P. R. China
- AgResearch Limited
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6
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Yuasa T, Amo-Shiinoki K, Ishikura S, Takahara M, Matsuoka T, Kaneto H, Kuroda A, Matsuhisa M, Hashida S. Sequential cleavage of insulin receptor by calpain 2 and γ-secretase impairs insulin signalling. Diabetologia 2016; 59:2711-2721. [PMID: 27695899 DOI: 10.1007/s00125-016-4102-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Accepted: 08/08/2016] [Indexed: 10/20/2022]
Abstract
AIMS/HYPOTHESIS Soluble insulin receptor (sIR), the ectodomain of the insulin receptor (IR), has been detected in human plasma and its concentration paralleled that of blood glucose. We have previously developed an in vitro model using HepG2 liver-derived cells, which mimics changes in sIR levels in plasma from diabetic patients and shows that calcium-dependent proteases cleave IR extracellularly (a process known as shedding). The present study aimed to reveal the mechanisms of IR cleavage. METHODS Using the in vitro model, we investigated the molecular mechanisms of IR cleavage, which is accelerated by high-glucose treatment. We also analysed the relationship between IR cleavage and cellular insulin resistance, and the correlation between plasma sIR levels and insulin sensitivity, which was assessed by the euglycaemic-hyperinsulinaemic clamp technique. RESULTS Here, we determined that calpain 2, which is secreted into the extracellular space associated with exosomes, directly cleaved the ectodomain of the IRβ subunit (IRβ), which in turn promoted intramembrane cleavage of IRβ by γ-secretase. IR cleavage impaired insulin signalling and the inhibition of IR cleavage (by knockdown of calpain 2 and γ-secretase), restored IR substrate-1 and Akt, independent of IR. Furthermore, the glucose-lowering drug, metformin, prevented IR cleavage accompanied by inhibition of calpain 2 release in exosomes, and re-established insulin signalling. In patients with type 2 diabetes, plasma sIR levels inversely correlated with insulin sensitivity. CONCLUSIONS/INTERPRETATION Sequential cleavage of IR by calpain 2 and γ-secretase may contribute to insulin signalling in cells and its inhibition may be partly responsible for the glucose-lowering effects of metformin. Thus, IR cleavage may offer a new mechanism for the aetiology of insulin resistance.
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Affiliation(s)
- Tomoyuki Yuasa
- Division of Molecular Genetics, Institute for Enzyme Research, Tokushima University, Tokushima, Japan.
- Department of Community Medicine for Diabetes and Metabolic Disorders, Tokushima University Graduate School, 3-18-15 Kuramoto-cho, Tokushima-shi, Tokushima, 770-8503, Japan.
| | - Kikuko Amo-Shiinoki
- Division of Molecular Genetics, Institute for Enzyme Research, Tokushima University, Tokushima, Japan
- Department of Diabetes Research, Yamaguchi University School of Medicine, Yamaguchi, Japan
| | - Shuhei Ishikura
- Division of Molecular Genetics, Institute for Enzyme Research, Tokushima University, Tokushima, Japan
- Department of Cell Biology, Faculty of Medicine, Fukuoka University, Fukuoka, Japan
| | - Mitsuyoshi Takahara
- Department of Metabolic Medicine, Osaka University Graduate School of Medicine, Osaka, Japan
- Department of Diabetes Care Medicine, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Takaaki Matsuoka
- Department of Metabolic Medicine, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Hideaki Kaneto
- Department of Metabolic Medicine, Osaka University Graduate School of Medicine, Osaka, Japan
- Department of Diabetes, Endocrinology and Metabolism, Kawasaki Medical School, Okayama, Japan
| | - Akio Kuroda
- Diabetes Clinical Research and Development Center, Tokushima University, Tokushima, Japan
- Diabetes Therapeutics and Research Center, Institute for Advanced Medical Sciences, Tokushima University, Tokushima, Japan
| | - Munehide Matsuhisa
- Diabetes Clinical Research and Development Center, Tokushima University, Tokushima, Japan
- Diabetes Therapeutics and Research Center, Institute for Advanced Medical Sciences, Tokushima University, Tokushima, Japan
| | - Seiichi Hashida
- Human Life Science, Tokushima Bunri University, Tokushima, Japan
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7
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Liu J, Wang L, Wang W, Li Y, Jia X, Zhai S, Shi J, Dang S. Application of network construction to estimate functional changes to insulin receptor substrates 1 and 2 in Huh7 cells following infection with the hepatitis C virus. Mol Med Rep 2016; 14:2379-88. [PMID: 27432476 PMCID: PMC4991679 DOI: 10.3892/mmr.2016.5527] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Accepted: 05/03/2016] [Indexed: 12/16/2022] Open
Abstract
Hepatitis C virus (HCV) is closely associated with insulin resistance (IS), acting primarily by interfering with insulin signaling pathways, increasing cytokine-mediated (tumor necrosis factor α, interleukin 6) inflammatory responses and enhancing oxidative stress. In the insulin signaling pathways, the insulin receptor substrate (IRS) is one of the key regulatory factors. The present study constructed gene regulatory sub-networks specific for IRS1 and IRS2 in Huh7 cells and HCV-infected Huh7 (HCV-Huh7) cells using linear programming and a decomposition algorithm, and investigated the possible mechanisms underlying the function of IRS1/2 in HCV-induced IS in Huh7 cells. All data were obtained from GSE20948 of the Gene Expression Omnibus database from the National Center for Biotechnology Information. Genes which were significantly differentially expressed between Huh7 and HCV-Huh7 cells were analyzed using the significance analysis of microarray algorithm. The top 50 genes, including IRS1/2, were used as target genes to determine the gene regulatory networks and next the sub-networks of IRS1 and IRS2 in HCV-Huh7 and Huh7 cells using Gene Regulatory Network Inference Tool, an algorithm based on linear programming and the decomposition process. The IRS1/2 sub-networks were divided into upstream/downstream groups and activation/suppression clusters, and were further analyzed using Molecule Annotation System 3.0 and Database for Annotation, Visualization, and Integrated Discovery software, two online platforms for enrichment and clustering analysis and visualization. The results indicated that in Huh7 cells, the downstream network of IRS2 is more complex than that of IRS1, indicating that the insulin metabolism in Huh7 cells may be primarily mediated by IRS2. In HCV-Huh7 cells, the downstream pathway of IRS2 is blocked, suggesting that this may be the underlying mechanism in HCV infection that leads to insulin resistance. The present findings add a further dimension to the understanding of the pathological mechanisms of HCV infection-associated insulin resistance, and provide novel concepts for insulin resistance and glucose metabolism research.
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Affiliation(s)
- Jingkun Liu
- Department of Infectious Diseases, The Second Affiliated Hospital of Medical School of Xi'an Jiaotong University, Xi'an, Shaanxi 710004, P.R. China
| | - Linbang Wang
- The First Clinical Department, Chongqing Medical University, Chongqing 400016, P.R. China
| | - Wenjun Wang
- Department of Infectious Diseases, The Second Affiliated Hospital of Medical School of Xi'an Jiaotong University, Xi'an, Shaanxi 710004, P.R. China
| | - Yaping Li
- Department of Infectious Diseases, The Second Affiliated Hospital of Medical School of Xi'an Jiaotong University, Xi'an, Shaanxi 710004, P.R. China
| | - Xiaoli Jia
- Department of Infectious Diseases, The Second Affiliated Hospital of Medical School of Xi'an Jiaotong University, Xi'an, Shaanxi 710004, P.R. China
| | - Song Zhai
- Department of Infectious Diseases, The Second Affiliated Hospital of Medical School of Xi'an Jiaotong University, Xi'an, Shaanxi 710004, P.R. China
| | - Juan Shi
- Department of Infectious Diseases, The Second Affiliated Hospital of Medical School of Xi'an Jiaotong University, Xi'an, Shaanxi 710004, P.R. China
| | - Shuangsuo Dang
- Department of Infectious Diseases, The Second Affiliated Hospital of Medical School of Xi'an Jiaotong University, Xi'an, Shaanxi 710004, P.R. China
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8
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Yang P, Pei Q, Yu T, Chang Q, Wang D, Gao M, Zhang X, Liu Y. Compromised Wound Healing in Ischemic Type 2 Diabetic Rats. PLoS One 2016; 11:e0152068. [PMID: 27028201 PMCID: PMC4814123 DOI: 10.1371/journal.pone.0152068] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Accepted: 03/07/2016] [Indexed: 02/06/2023] Open
Abstract
Ischemia is one of the main epidemic factors and characteristics of diabetic chronic wounds, and exerts a profound effect on wound healing. To explore the mechanism of and the cure for diabetic impaired wound healing, we established a type 2 diabetic rat model. We used an 8weeks high fat diet (HFD) feeding regimen followed by multiple injections of streptozotocin (STZ) at a dose of 10mg/kg to induce Wister rat to develop type 2 diabetes. Metabolic characteristics were assessed at the 5th week after the STZ injections to confirm the establishment of diabetes mellitus on the rodent model. A bipedicle flap, with length to width ratio 1.5, was performed on the back of the rat to make the flap area ischemic. Closure of excisional wounds on this bipedicle flap and related physiological and pathological changes were studied using histological, immunohistochemical, real time PCR and protein immunoblot approaches. Our results demonstrated that a combination of HFD feeding and a low dose of STZ is capable of inducing the rats to develop type 2 diabetes with noticeable insulin resistance, persistent hyperglycemia, moderate degree of insulinemia, as well as high serum cholesterol and high triglyceride levels. The excision wounds on the ischemic double pedicle flap showed deteriorative healing features comparing with non-ischemic diabetic wounds, including: delayed healing, exorbitant wound inflammatory response, excessive and prolonged ROS production and excessive production of MMPs. Our study suggested that HFD feeding combined with STZ injection could induce type 2 diabetes in rat. Our ischemic diabetic wound model is suitable for the investigation of human diabetic related wound repair; especically for diabetic chronic wounds.
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Affiliation(s)
- Peilang Yang
- Department of Burn and Plastic Surgery, Shanghai Jiao Tong University School of Medicine, Ruijin Hospital, Shanghai 200025, China
| | - Qing Pei
- Department of Burn and Plastic Surgery, Shanghai Jiao Tong University School of Medicine, Ruijin Hospital, Shanghai 200025, China
| | - Tianyi Yu
- Department of Burn and Plastic Surgery, Shanghai Jiao Tong University School of Medicine, Ruijin Hospital, Shanghai 200025, China
| | - Qingxuan Chang
- Department of Burn and Plastic Surgery, Shanghai Jiao Tong University School of Medicine, Ruijin Hospital, Shanghai 200025, China
| | - Di Wang
- Department of Burn and Plastic Surgery, Shanghai Jiao Tong University School of Medicine, Ruijin Hospital, Shanghai 200025, China
| | - Min Gao
- Department of Burn and Plastic Surgery, Shanghai Jiao Tong University School of Medicine, Ruijin Hospital, Shanghai 200025, China
| | - Xiong Zhang
- Department of Burn and Plastic Surgery, Shanghai Jiao Tong University School of Medicine, Ruijin Hospital, Shanghai 200025, China
| | - Yan Liu
- Department of Burn and Plastic Surgery, Shanghai Jiao Tong University School of Medicine, Ruijin Hospital, Shanghai 200025, China
- * E-mail:
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9
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Noh H, Yu MR, Kim HJ, Jang EJ, Hwang ES, Jeon JS, Kwon SH, Han DC. Uremic toxin p-cresol induces Akt-pathway-selective insulin resistance in bone marrow-derived mesenchymal stem cells. Stem Cells 2015; 32:2443-53. [PMID: 24805773 DOI: 10.1002/stem.1738] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Revised: 04/04/2014] [Accepted: 04/11/2014] [Indexed: 11/06/2022]
Abstract
We reported a functional incompetence in mesenchymal stem cells (MSCs) under uremia, but the mechanisms have not been explored. To study the mechanisms of dysfunctional MSCs induced by uremia, we characterized insulin signaling in MSCs and investigated the effect of uremic toxin, p-cresol, on the proangiogenic actions of insulin. In MSCs, insulin induced hypoxia-inducible factor (HIF)-1α, vascular endothelial growth factor, and stromal cell-derived factor 1α expressions via PI3K/Akt-dependent pathway. MSCs treated with p-cresol exhibited altered insulin signaling in a selective manner for insulin receptor substrate-1/PI3K/Akt pathway, whereas ERK pathway remained active. The insulin-induced increase of HIF-1α was blunted by p-cresol treatment. This Akt-selective insulin resistance was also observed in MSCs isolated from chronic kidney disease (CKD) mice. In mice model of hindlimb ischemia, blood flow recovery, capillary density, and local production of angiogenic factors in the ischemic limb treated with CKD MSCs were significantly inferior to those promoted by control MSCs. However, modifying CKD MSCs by overexpression of HIF-1α restored all of these changes. Taken together, these data suggest that p-cresol contributes to insulin resistance in a selective manner for Akt pathway. This might be a biological explanation for the functional incompetence of MSCs under uremia through defects in the insulin-induced elevation of HIF-1α protein expression.
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Affiliation(s)
- Hyunjin Noh
- Department of Internal Medicine, Soon Chun Hyang University, Seoul, Korea; Hyonam Kidney Laboratory, Soon Chun Hyang University, Seoul, Korea
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Sajan MP, Ivey RA, Farese RV. BMI-related progression of atypical PKC-dependent aberrations in insulin signaling through IRS-1, Akt, FoxO1 and PGC-1α in livers of obese and type 2 diabetic humans. Metabolism 2015; 64:1454-65. [PMID: 26386696 PMCID: PMC4576742 DOI: 10.1016/j.metabol.2015.08.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Revised: 08/19/2015] [Accepted: 08/20/2015] [Indexed: 12/16/2022]
Abstract
Information on insulin resistance in human liver is limited. In mouse diet-induced obesity (DIO), hepatic insulin resistance initially involves: lipid+insulin-induced activation of atypical protein kinase C (aPKC); elevated Akt activity/activation but selective impairment of compartmentalized Akt-dependent FoxO1 phosphorylation; and increases in gluconeogenic and lipogenic enzymes. In advanced stages, e.g., in hepatocytes of type 2 diabetes (T2D) humans, insulin activation of insulin receptor substrate-1(IRS-1) and Akt fails, further increasing FoxO1-dependent gluconeogenic/lipogenic enzyme expression. Increases in hepatic PGC-1α also figure prominently, but uncertainly, in this scheme. Here, we examined signaling factors in liver samples harvested from human transplant donors with increasing BMI, 20→25→30→35→40→45. We found, relative to lean (BMI=20-25) humans, obese (BMI>30) humans had all abnormalities seen in early mouse DIO, but, surprisingly, at all elevated BMI levels, had decreased insulin receptor-1 (IRS-1) levels, decreased Akt activity, and increased expression/abundance of aPKC-ι and PGC-1α. Moreover, with increasing BMI, there were: progressive increases in aPKC activity and PKC-ι expression/abundance; progressive decreases in IRS-1 levels, Akt activity and FoxO1 phosphorylation; progressive increases in expression/abundance of PGC-1α; and progressive increases in gluconeogenic and lipogenic enzymes. Remarkably, all abnormalities reached T2D levels at higher BMI levels. Most importantly, both "early" and advanced abnormalities were largely reversed by 24-hour treatment of T2D hepatocytes with aPKC inhibitor. We conclude: hepatic insulin resistance in human obesity is: advanced; BMI-correlated; and sequentially involves increased aPKC-activating ceramide; increased aPKC levels and activity; decreases in IRS-1 levels, Akt activity, and FoxO1 phosphorylation; and increases in expression/abundance of PGC-1α and gluconeogenic and lipogenic genes.
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Affiliation(s)
- Mini P Sajan
- Research and Internal Medicine Services of the James A. Haley VA Medical Center, Tampa, FL; Department of Internal Medicine, University of South Florida College of Medicine, Tampa, FL
| | - Robert A Ivey
- Research and Internal Medicine Services of the James A. Haley VA Medical Center, Tampa, FL
| | - Robert V Farese
- Research and Internal Medicine Services of the James A. Haley VA Medical Center, Tampa, FL; Department of Internal Medicine, University of South Florida College of Medicine, Tampa, FL.
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Liu M, Pan Q, Chen Y, Yang X, Zhao B, Jia L, Zhu Y, Zhang B, Gao X, Li X, Han J, Duan Y. Administration of Danhong Injection to diabetic db/db mice inhibits the development of diabetic retinopathy and nephropathy. Sci Rep 2015; 5:11219. [PMID: 26061387 PMCID: PMC4462147 DOI: 10.1038/srep11219] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2015] [Accepted: 05/18/2015] [Indexed: 12/21/2022] Open
Abstract
Danhong Injection (DHI), a Chinese medicine for treatment of patients with coronary heart disease, inhibits primary abdominal aortic aneurysms in apoE deficient (apoE−/−) mice. Formation of microaneurysms plays an important role in the development of diabetic retinopathy and nephropathy. It remains unknown if DHI can reduce these diabetic complications. In this study, diabetic db/db mice in two groups were injected with saline and DHI, respectively, for 14 weeks. Blood and tissue samples were collected to determine serum glucose, lipids and tissue structure. DHI reduced diabetes-induced body weight gain, serum cholesterol and glucose levels. In retinas, DHI blocked the shrink of whole retina and retinal sub-layers by inhibiting expression of caspase 3, matrix metalloproteinase 2 (MMP-2) and MMP-9, accumulation of carbohydrate macromolecules and formation of acellular capillaries. DHI improved renal functions by inhibiting mesangial matrix expansion, expression of vascular endothelial growth factor A, fibronectin and advanced glycation end products in kidneys. Mechanistically, DHI induced expression of glucokinase, AMPKα/phosphorylated AMPKα, insulin receptor substrate 1, fibroblast growth factor 21 and peroxisome proliferator-activated γ. Expression of genes responsible for energy expenditure was also activated by DHI. Therefore, DHI inhibits diabetic retinopathy and nephropathy by ameliorating glucose metabolism and demonstrates a potential application in clinics.
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Affiliation(s)
- Mengyang Liu
- 1] State Key Laboratory of Medicinal Chemical Biology, Nankai University, Tianjin 300071, China [2] College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Quan Pan
- 1] State Key Laboratory of Medicinal Chemical Biology, Nankai University, Tianjin 300071, China [2] College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Yuanli Chen
- 1] State Key Laboratory of Medicinal Chemical Biology, Nankai University, Tianjin 300071, China [2] Collaborative Innovation Center for Biotherapy, Nankai University, Tianjin 300071, China
| | - Xiaoxiao Yang
- 1] State Key Laboratory of Medicinal Chemical Biology, Nankai University, Tianjin 300071, China [2] College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Buchang Zhao
- Buchang Pharmaceutical Co. Ltd., Xi'an 712000, China
| | - Lifu Jia
- Buchang Pharmaceutical Co. Ltd., Xi'an 712000, China
| | - Yan Zhu
- Tianjin University of Traditional Chinese Medicine, Tianjin 300193, China
| | - Boli Zhang
- Tianjin University of Traditional Chinese Medicine, Tianjin 300193, China
| | - Xiumei Gao
- Tianjin University of Traditional Chinese Medicine, Tianjin 300193, China
| | - Xiaoju Li
- College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Jihong Han
- 1] State Key Laboratory of Medicinal Chemical Biology, Nankai University, Tianjin 300071, China [2] Collaborative Innovation Center for Biotherapy, Nankai University, Tianjin 300071, China
| | - Yajun Duan
- 1] State Key Laboratory of Medicinal Chemical Biology, Nankai University, Tianjin 300071, China [2] Collaborative Innovation Center for Biotherapy, Nankai University, Tianjin 300071, China
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Williams MJ, Almén MS, Fredriksson R, Schiöth HB. What model organisms and interactomics can reveal about the genetics of human obesity. Cell Mol Life Sci 2012; 69:3819-34. [PMID: 22618246 PMCID: PMC11114734 DOI: 10.1007/s00018-012-1022-5] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Revised: 04/22/2012] [Accepted: 05/02/2012] [Indexed: 01/05/2023]
Abstract
Genome-wide association studies have identified a number of genes associated with human body weight. While some of these genes are large fields within obesity research, such as MC4R, POMC, FTO and BDNF, the majority do not have a clearly defined functional role explaining why they may affect body weight. Here, we searched biological databases and discovered 33 additional genes associated with human obesity (CADM2, GIPR, GPCR5B, LRP1B, NEGR1, NRXN3, SH2B1, FANCL, GNPDA2, HMGCR, MAP2K5, NUDT3, PRKD1, QPCTL, TNNI3K, MTCH2, DNAJC27, SLC39A8, MTIF3, RPL27A, SEC16B, ETV5, HMGA1, TFAP2B, TUB, ZNF608, FAIM2, KCTD15, LINGO2, POC5, PTBP2, TMEM18, TMEM160). We find that the majority have orthologues in distant species, such as D. melanogaster and C. elegans, suggesting that they are important for the biology of most bilateral species. Intriguingly, signalling cascade genes and transcription factors are enriched among these obesity genes, and several of the genes show properties that could be useful for potential drug discovery. In this review, we demonstrate how information from several distant model species, interactomics and signalling pathway analysis represents an important way to better understand the functional diversity of the surprisingly high number of molecules that seem to be important for human obesity.
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Affiliation(s)
- Michael J. Williams
- Department of Neuroscience, Functional Pharmacology, Biomedical Center, Uppsala University, Box 593, 75 124 Uppsala, Sweden
| | - Markus S. Almén
- Department of Neuroscience, Functional Pharmacology, Biomedical Center, Uppsala University, Box 593, 75 124 Uppsala, Sweden
| | - Robert Fredriksson
- Department of Neuroscience, Functional Pharmacology, Biomedical Center, Uppsala University, Box 593, 75 124 Uppsala, Sweden
| | - Helgi B. Schiöth
- Department of Neuroscience, Functional Pharmacology, Biomedical Center, Uppsala University, Box 593, 75 124 Uppsala, Sweden
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Buitrago CG, Arango NS, Boland RL. 1α,25(OH)2D3-dependent modulation of Akt in proliferating and differentiating C2C12 skeletal muscle cells. J Cell Biochem 2012; 113:1170-81. [PMID: 22095470 DOI: 10.1002/jcb.23444] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
We previously reported that 1α,25-dihydroxy-vitamin D(3) [1α,25(OH)(2)D(3)] induces non-transcriptional rapid responses through activation of Src and MAPKs in the skeletal muscle cell line C2C12. In the present study we investigated the modulation of Akt by the secosteroid hormone in C2C12 cells at proliferative stage (myoblasts) and at early differentiation stage. In proliferating cells, 1α,25(OH)(2)D(3) activates Akt by phosphorylation in Ser473 in a time-dependent manner (5-60 min). When these cells were pretreated with methyl-beta-cyclodextrin to disrupt caveolae microdomains, hormone-induced activation of Akt was suppressed. Similar results were obtained by siRNA silencing of caveolin-1 expression, further indicating that hormone effects on cell membrane caveolae are required for downstream signaling. PI3K and p38 MAPK, but not ERK1/2, participate in 1α,25(OH)(2)D(3) activation of Akt in myoblasts. The involvement of p38 MAPK in Akt phosphorylation by the hormone probably occurs through MAPK-activated protein kinase 2 (MK2), which is activated by the steroid. In addition, the participation of Src in Akt phosphorylation by 1α,25(OH)(2)D(3) was demonstrated using the inhibitor PP2 and antisense oligodeoxynucleotides that suppress Src expression. We also observed that PI3K participates in hormone-induced proliferation. During the early phase of C2C12 cell differentiation 1α,25(OH)(2)D(3) also increases Akt phosphorylation and activates Src. Of relevance, Src and PI3K are involved in Akt activation and in MHC and myogenin increased expression by 1α,25(OH)(2)D(3). Altogether, these data suggest that 1α,25(OH)(2)D(3) upregulates Akt through Src, PI(3)K, and p38 MAPK to stimulate myogenesis in C2C12 cells.
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Affiliation(s)
- Claudia G Buitrago
- Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, 8000 Bahía Blanca, Argentina
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Leal ADC, Canton APM, Montenegro LR, Coutinho DC, Arnhold IJP, Jorge AADL. [Mutations in insulin-like growth factor receptor 1 gene (IGF1R) resulting in intrauterine and postnatal growth retardation]. ACTA ACUST UNITED AC 2012; 55:541-9. [PMID: 22218435 DOI: 10.1590/s0004-27302011000800007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2011] [Accepted: 10/20/2011] [Indexed: 11/22/2022]
Abstract
Approximately 10% of children born small-for-gestational age (SGA) do not show spontaneous growth catch-up. The causes of this deficit in prenatal growth and its maintenance after birth are not completely known, in most cases. Over the past eight years, several heterozygous inactivating mutations and deletions in IGF1R gene have been reported, indicating the role of defects in the IGFs/IGF1R axis as a cause of growth deficit. It has been hypothesized that at least 2.5% of children born SGA may have IGF1R gene defects. The clinical presentation of these patients is highly variable in the severity of growth retardation and hormonal parameters. In the most evident cases, patients have microcephaly, mild cognitive impairment and high levels of IGF-1, associated with short stature of prenatal onset. This review will describe the clinical, molecular and treatment of short stature with hrGH of children with mutations in the IGF1R gene.
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Affiliation(s)
- Andréa de Castro Leal
- Unidade de Endocrinologia do Desenvolvimento, Laboratório de Hormônios e Genética Molecular, Hospital das Clínicas, São Paulo, Brasil
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15
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Abstract
PURPOSE OF REVIEW To review the aberrations of insulin signaling to atypical protein kinase C (aPKC) in muscle and liver that generate cardiovascular risk factors, including obesity, hypertriglyceridemia, hypercholesterolemia, insulin resistance and glucose intolerance in type 2 diabetes mellitus (T2DM), and obesity-associated metabolic syndrome (MetSyn). RECENT FINDINGS aPKC and Akt mediate the insulin effects on glucose transport in muscle and synthesis of lipids, cytokines and glucose in liver. In T2DM, whereas Akt and aPKC activation are diminished in muscle, and hepatic Akt activation is diminished, hepatic aPKC activation is conserved. Imbalance between muscle and hepatic aPKC activation (and expression of PKC-ι in humans) by insulin results from differential downregulation of insulin receptor substrates that control phosphatidylinositol-3-kinase. Conserved activation of hepatic aPKC in hyperinsulinemic states of T2DM, obesity and MetSyn is problematic, as excessive activation of aPKC-dependent lipogenic, gluconeogenic and proinflammatory pathways increases the cardiovascular risk factors. Indeed, selective inhibition of hepatic aPKC by adenoviral-mediated expression of kinase-inactive aPKC, or newly developed small-molecule biochemicals, dramatically improves abdominal obesity, hepatosteatosis, hypertriglyceridemia, hypercholesterolemia, insulin resistance and glucose intolerance in murine models of obesity and T2DM. SUMMARY Hepatic aPKC is a unifying target for treating multiple clinical abnormalities that increase the cardiovascular risk in insulin-resistant states of obesity, MetSyn and T2DM.
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Affiliation(s)
- Robert V Farese
- Medical and Research Services, James A. Haley Veterans Medical Center Department of Internal Medicine, University of South Florida College of Medicine, Tampa Metabolism Division, Roskamp Institute, Sarasota, Florida, USA
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16
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Sajan MP, Farese RV. Insulin signalling in hepatocytes of humans with type 2 diabetes: excessive production and activity of protein kinase C-ι (PKC-ι) and dependent processes and reversal by PKC-ι inhibitors. Diabetologia 2012; 55:1446-57. [PMID: 22349071 PMCID: PMC3543149 DOI: 10.1007/s00125-012-2477-5] [Citation(s) in RCA: 25] [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: 10/28/2011] [Accepted: 12/21/2011] [Indexed: 12/28/2022]
Abstract
AIMS/HYPOTHESIS We examined the role of protein kinase C-ι (PKC-ι) in mediating alterations in the abundance of enzymes in hepatocytes of type 2 diabetic humans that contribute importantly to the development of lipid and carbohydrate abnormalities in type 2 diabetes. METHODS We examined (1) insulin signalling in isolated hepatocytes of non-diabetic and type 2 diabetic humans and (2) the effects of two newly developed small molecule PKC-ι inhibitors on aberrant signalling and downstream processes. RESULTS In contrast with PKC-ι deficiency in diabetic muscle, which diminishes glucose transport, PKC-ι in diabetic hepatocytes was overproduced and overactive, basally and after insulin treatment, and, moreover, was accompanied by increased abundance of PKC-ι-dependent lipogenic, proinflammatory and gluconeogenic enzymes. Heightened PKC-ι activity most likely reflected heightened activity of IRS-2-dependent phosphatidylinositol 3-kinase (PI3K), as IRS-1 levels and IRS-1/PI3K activity were markedly diminished. Importantly, insulin-stimulated PKC-ι abundance and its overabundance in diabetic hepatocytes was reversed in vitro by both insulin deprivation and PKC-ι inhibitors; this suggested operation of an insulin-driven, feed-forward/positive-feedback mechanism. In contrast with PKC-ι, protein kinase B (Akt2) activity and activation by insulin was diminished, apparently reflecting IRS-1 deficiency. Treatment of diabetic hepatocytes with PKC-ι/λ inhibitors diminished abundance of lipogenic, proinflammatory and gluconeogenic enzymes. CONCLUSIONS/INTERPRETATION Our findings suggest that a vicious cycle of PKC-ι overactivity and overproduction exists in hepatocytes of humans with type 2 diabetes and contributes importantly to maintaining overactivity of lipogenic, proinflammatory and gluconeogenic pathways, which underlies the lipid and carbohydrate abnormalities in type 2 diabetes.
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Affiliation(s)
- M P Sajan
- Medical and Research Services, James A Haley Veterans Medical Center, 13000 Bruce B Downs Blvd, Tampa, FL 33612, USA
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17
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Hu S, Yao J, Howe AA, Menke BM, Sivitz WI, Spector AA, Norris AW. Peroxisome proliferator-activated receptor γ decouples fatty acid uptake from lipid inhibition of insulin signaling in skeletal muscle. Mol Endocrinol 2012; 26:977-88. [PMID: 22474127 DOI: 10.1210/me.2011-1253] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Peroxisome proliferator-activated receptor γ (PPARγ) is expressed at low levels in skeletal muscle, where it protects against adiposity and insulin resistance via unclear mechanisms. To test the hypothesis that PPARγ directly modulates skeletal muscle metabolism, we created two models that isolate direct PPARγ actions on skeletal myocytes. PPARγ was overexpressed in murine myotubes by adenotransfection and in mouse skeletal muscle by plasmid electroporation. In cultured myotubes, PPARγ action increased fatty acid uptake and incorporation into myocellular lipids, dependent upon a 154 ± 20-fold up-regulation of CD36 expression. PPARγ overexpression more than doubled insulin-stimulated thymoma viral proto-oncogene (AKT) phosphorylation during low lipid availability. Furthermore, in myotubes exposed to palmitate levels that inhibit insulin signaling, PPARγ overexpression increased insulin-stimulated AKT phosphorylation and glycogen synthesis over 3-fold despite simultaneously increasing myocellular palmitate uptake. The insulin signaling enhancement was associated with an increase in activating phosphorylation of phosphoinositide-dependent protein kinase 1 and a normalized expression of palmitate-induced genes that antagonize AKT phosphorylation. In vivo, PPARγ overexpression more than doubled insulin-dependent AKT phosphorylation in lipid-treated mice but did not augment insulin-stimulated glucose uptake. We conclude that direct PPARγ action promotes myocellular storage of energy by increasing fatty acid uptake and esterification while simultaneously enhancing insulin signaling and glycogen formation. However, direct PPARγ action in skeletal muscle is not sufficient to account for the hypoglycemic actions of PPARγ agonists during lipotoxicity.
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Affiliation(s)
- Shanming Hu
- Department of Pediatrics, University of Iowa, Iowa City, IA 52242, USA
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18
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Aronis KN, Mantzoros CS. A brief history of insulin resistance: from the first insulin radioimmunoassay to selectively targeting protein kinase C pathways. Metabolism 2012; 61:445-9. [PMID: 22304840 DOI: 10.1016/j.metabol.2012.01.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/03/2012] [Accepted: 01/03/2012] [Indexed: 12/29/2022]
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Sajan MP, Nimal S, Mastorides S, Acevedo-Duncan M, Kahn CR, Fields AP, Braun U, Leitges M, Farese RV. Correction of metabolic abnormalities in a rodent model of obesity, metabolic syndrome, and type 2 diabetes mellitus by inhibitors of hepatic protein kinase C-ι. Metabolism 2012; 61:459-69. [PMID: 22225955 PMCID: PMC3786325 DOI: 10.1016/j.metabol.2011.12.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/24/2011] [Revised: 12/13/2011] [Accepted: 12/19/2011] [Indexed: 12/16/2022]
Abstract
Excessive activity of hepatic atypical protein kinase (aPKC) is proposed to play a critical role in mediating lipid and carbohydrate abnormalities in obesity, the metabolic syndrome, and type 2 diabetes mellitus. In previous studies of rodent models of obesity and type 2 diabetes mellitus, adenoviral-mediated expression of kinase-inactive aPKC rapidly reversed or markedly improved most if not all metabolic abnormalities. Here, we examined effects of 2 newly developed small-molecule PKC-ι/λ inhibitors. We used the mouse model of heterozygous muscle-specific knockout of PKC-λ, in which partial deficiency of muscle PKC-λ impairs glucose transport in muscle and thereby causes glucose intolerance and hyperinsulinemia, which, via hepatic aPKC activation, leads to abdominal obesity, hepatosteatosis, hypertriglyceridemia, and hypercholesterolemia. One inhibitor, 1H-imidazole-4-carboxamide, 5-amino-1-[2,3-dihydroxy-4-[(phosphonooxy)methyl]cyclopentyl-[1R-(1a,2b,3b,4a)], binds to the substrate-binding site of PKC-λ/ι, but not other PKCs. The other inhibitor, aurothiomalate, binds to cysteine residues in the PB1-binding domains of aPKC-λ/ι/ζ and inhibits scaffolding. Treatment with either inhibitor for 7 days inhibited aPKC, but not Akt, in liver and concomitantly improved insulin signaling to Akt and aPKC in muscle and adipocytes. Moreover, both inhibitors diminished excessive expression of hepatic, aPKC-dependent lipogenic, proinflammatory, and gluconeogenic factors; and this was accompanied by reversal or marked improvements in hyperglycemia, hyperinsulinemia, abdominal obesity, hepatosteatosis, hypertriglyceridemia, and hypercholesterolemia. Our findings highlight the pathogenetic importance of insulin signaling to hepatic PKC-ι in obesity, the metabolic syndrome, and type 2 diabetes mellitus and suggest that 1H-imidazole-4-carboxamide, 5-amino-1-[2,3-dihydroxy-4-[(phosphonooxy)methyl]cyclopentyl-[1R-(1a,2b,3b,4a)] and aurothiomalate or similar agents that selectively inhibit hepatic aPKC may be useful treatments.
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Affiliation(s)
- Mini P. Sajan
- Medical and Research Services, James A. Haley Veterans Medical Center, Tampa, FL 33612, USA
| | | | - Stephen Mastorides
- Medical and Research Services, James A. Haley Veterans Medical Center, Tampa, FL 33612, USA
| | - Mildred Acevedo-Duncan
- Medical and Research Services, James A. Haley Veterans Medical Center, Tampa, FL 33612, USA
| | - C. Ronald Kahn
- Joslin Research Foundation, Haruard Medical School, Boston, MA, USA
| | - Alan P. Fields
- Pathology Department, Mayo Clinic, Jacksonuille, FL, USA
| | | | | | - Robert V. Farese
- Medical and Research Services, James A. Haley Veterans Medical Center, Tampa, FL 33612, USA
- Roskamp Institute, Sarasota, FA, USA
- Department of Internal Medicine, Uniuersity of South Florida College of Medicine, Tampa, FL 33612, USA
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20
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Maeno Y, Li Q, Park K, Rask-Madsen C, Gao B, Matsumoto M, Liu Y, Wu IH, White MF, Feener EP, King GL. Inhibition of insulin signaling in endothelial cells by protein kinase C-induced phosphorylation of p85 subunit of phosphatidylinositol 3-kinase (PI3K). J Biol Chem 2011; 287:4518-30. [PMID: 22158866 DOI: 10.1074/jbc.m111.286591] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The regulation of endothelial function by insulin is consistently abnormal in insulin-resistant states and diabetes. Protein kinase C (PKC) activation has been reported to inhibit insulin signaling selectively in endothelial cells via the insulin receptor substrate/PI3K/Akt pathway to reduce the activation of endothelial nitric-oxide synthase (eNOS). In this study, it was observed that PKC activation differentially inhibited insulin receptor substrate 1/2 (IRS1/2) signaling of insulin's activation of PI3K/eNOS by decreasing only tyrosine phosphorylation of IRS2. In addition, PKC activation, by general activator and specifically by angiotensin II, increased the phosphorylation of p85/PI3K, which decreases its association with IRS1 and activation. Thr-86 of p85/PI3K was identified to be phosphorylated by PKC activation and confirmed to affect IRS1-mediated activation of Akt/eNOS by insulin and VEGF using a deletion mutant of the Thr-86 region of p85/PI3K. Thus, PKC and angiotensin-induced phosphorylation of Thr-86 of p85/PI3K may partially inhibit the activation of PI3K/eNOS by multiple cytokines and contribute to endothelial dysfunction in metabolic disorders.
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Affiliation(s)
- Yasuhiro Maeno
- Section of Vascular Cell Biology, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts 02115, USA
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21
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Ortmeyer HK, Sajan MP, Miura A, Kanoh Y, Rivas J, Li Y, Standaert ML, Ryan AS, Bodkin NL, Farese RV, Hansen BC. Insulin signaling and insulin sensitizing in muscle and liver of obese monkeys: peroxisome proliferator-activated receptor gamma agonist improves defective activation of atypical protein kinase C. Antioxid Redox Signal 2011; 14:207-19. [PMID: 20518698 PMCID: PMC3014763 DOI: 10.1089/ars.2010.3234] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Obesity, the metabolic syndrome, and aging share several pathogenic features in both humans and non-human primates, including insulin resistance and inflammation. Since muscle and liver are considered key integrators of metabolism, we sought to determine in biopsies from lean and obese aging rhesus monkeys the nature of defects in insulin activation and, further, the potential for mitigation of such defects by an in vivo insulin sensitizer, rosiglitazone, and a thiazolidinedione activator of the peroxisome proliferator-activated receptor gamma. The peroxisome proliferator-activated receptor gamma agonist reduced hyperinsulinemia, improved insulin sensitivity, lowered plasma triglycerides and free fatty acids, and increased plasma adiponectin. In muscle of obese monkeys, previously shown to exhibit defective insulin signaling, the insulin sensitizer improved insulin activation of atypical protein kinase C (aPKC), the defective direct activation of aPKC by phosphatidylinositol (PI)-3,4,5-(PO₄)₃, and 5'-AMP-activated protein kinase and increased carnitine palmitoyltransferase-1 mRNA expression, but it did not improve insulin activation of insulin receptor substrate (IRS)-1-dependent PI 3-kinase (IRS-1/PI3K), protein kinase B, or glycogen synthase. We found that, although insulin signaling was impaired in muscle, insulin activation of IRS-1/PI3K, IRS-2/PI3K, protein kinase B, and aPKC was largely intact in liver and that rosiglitazone improved insulin signaling to aPKC in muscle by improving responsiveness to PI-3,4,5-(PO₄)₃.
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Affiliation(s)
- Heidi K Ortmeyer
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA
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Spontaneous Irs1 passenger mutation linked to a gene-targeted SerpinB2 allele. Proc Natl Acad Sci U S A 2010; 107:16904-9. [PMID: 20837540 DOI: 10.1073/pnas.1012050107] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
In characterizing mice with targeted disruption of the SerpinB2 gene, we observed animals that were small at birth with delayed growth and decreased life expectancy. Although this phenotype cosegregated with homozygosity for the inactive SerpinB2 allele, analysis of homozygous SerpinB2-deficient mice derived from two additional independent embryonic stem (ES) cell clones exhibited no growth abnormalities. Examination of additional progeny from the original SerpinB2-deficient line revealed recombination between the small phenotype (smla) and the SerpinB2 locus. The locus responsible for smla was mapped to a 2.78-Mb interval approximately 30 Mb proximal to SerpinB2, bounded by markers D1Mit382 and D1Mit216. Sequencing of Irs1 identified a nonsense mutation at serine 57 (S57X), resulting in complete loss of IRS1 protein expression. Analysis of ES cell DNA suggests that the S57X Irs1 mutation arose spontaneously in an ES cell subclone during cell culture. Although the smla phenotype is similar to previously reported Irs1 alleles, mice exhibited decreased survival, in contrast to the enhanced longevity reported for IRS1 deficiency generated by gene targeting. This discrepancy could result from differences in strain background, unintended indirect effects of the gene targeting, or the minimal genetic interference of the S57X mutation compared with the conventionally targeted Irs1-KO allele. Spontaneous mutations arising during ES cell culture may be a frequent but underappreciated occurrence. When linked to a targeted allele, such mutations could lead to incorrect assignment of phenotype and may account for a subset of markedly discordant results from experiments independently targeting the same gene.
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Farese RV, Sajan MP. Metabolic functions of atypical protein kinase C: "good" and "bad" as defined by nutritional status. Am J Physiol Endocrinol Metab 2010; 298:E385-94. [PMID: 19996389 PMCID: PMC3774273 DOI: 10.1152/ajpendo.00608.2009] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Atypical protein kinase C (aPKC) isoforms mediate insulin effects on glucose transport in muscle and adipose tissues and lipid synthesis in liver and support other metabolic processes, expression of enzymes needed for islet insulin secretion and hepatic glucose production/release, CNS appetite suppression, and inflammatory responses. In muscle, selective aPKC deficiency impairs glucose uptake and produces insulin resistance and hyperinsulinemia, which, by activating hepatic aPKC, provokes inordinate increases in lipid synthesis and produces typical "metabolic syndrome" features. In contrast, hepatic aPKC deficiency diminishes lipid synthesis and protects against metabolic syndrome features. Unfortunately, aPKC is deficient in muscle but paradoxically conserved in liver in obesity and type 2 diabetes mellitus; this combination is particularly problematic because it promotes lipid and carbohydrate abnormalities. Accordingly, metabolic effects of aPKCs can be "good" or "bad," depending upon nutritional status; thus, muscle glucose uptake, islet insulin secretion, hepatic glucose and lipid production/release, and adipose fat synthesis/storage would be important for survival during periods of limited food availability and therefore be "good." However, during times of food surfeit, excessive activation of hepatic aPKC, whether caused by overnutrition or impairments in extrahepatic effects of insulin, would lead to inordinate increases in hepatic lipid synthesis and metabolic syndrome features and therefore be "bad." In keeping with these ideas, the inhibition of hepatic aPKC markedly ameliorates lipid and carbohydrate abnormalities in experimental models of obesity and type 2 diabetes. We postulate that a similar approach may be useful for treating humans.
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Affiliation(s)
- Robert V Farese
- James A. Haley Veteran's Administration Medical Center, Tampa, FL 33612, USA.
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24
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Yoshizawa T, Hinoi E, Jung DY, Kajimura D, Ferron M, Seo J, Graff JM, Kim JK, Karsenty G. The transcription factor ATF4 regulates glucose metabolism in mice through its expression in osteoblasts. J Clin Invest 2009; 119:2807-17. [PMID: 19726872 DOI: 10.1172/jci39366] [Citation(s) in RCA: 165] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2009] [Accepted: 06/10/2009] [Indexed: 12/29/2022] Open
Abstract
The recent demonstration that osteoblasts have a role in controlling energy metabolism suggests that they express cell-specific regulatory genes involved in this process. Activating transcription factor 4 (ATF4) is a transcription factor that accumulates predominantly in osteoblasts, where it regulates virtually all functions linked to the maintenance of bone mass. Since Atf4-/- mice have smaller fat pads than littermate controls, we investigated whether ATF4 also influences energy metabolism. Here, we have shown, through analysis of Atf4-/- mice, that ATF4 inhibits insulin secretion and decreases insulin sensitivity in liver, fat, and muscle. Several lines of evidence indicated that this function of ATF4 occurred through its osteoblastic expression. First, insulin sensitivity is enhanced in the liver of Atf4-/- mice, but not in cultured hepatocytes from these mice. Second, mice overexpressing ATF4 in osteoblasts only [termed here alpha1(I)Collagen-Atf4 mice] displayed a decrease in insulin secretion and were insulin insensitive. Third, the alpha1(I)Collagen-Atf4 transgene corrected the energy metabolism phenotype of Atf4-/- mice. Fourth, and more definitely, mice lacking ATF4 only in osteoblasts presented the same metabolic abnormalities as Atf4-/- mice. Molecularly, ATF4 favored expression in osteoblasts of Esp, which encodes a product that decreases the bioactivity of osteocalcin, an osteoblast-specific secreted molecule that enhances secretion of and sensitivity to insulin. These results provide a transcriptional basis to the observation that osteoblasts fulfill endocrine functions and identify ATF4 as a regulator of most functions of osteoblasts.
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Affiliation(s)
- Tatsuya Yoshizawa
- Department of Genetics and Development, Columbia University College of Physicians and Surgeons, New York, New York, USA
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25
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Sajan MP, Standaert ML, Rivas J, Miura A, Kanoh Y, Soto J, Taniguchi CM, Kahn CR, Farese RV. Role of atypical protein kinase C in activation of sterol regulatory element binding protein-1c and nuclear factor kappa B (NFkappaB) in liver of rodents used as a model of diabetes, and relationships to hyperlipidaemia and insulin resistance. Diabetologia 2009; 52:1197-207. [PMID: 19357831 PMCID: PMC4766834 DOI: 10.1007/s00125-009-1336-5] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/22/2009] [Accepted: 02/25/2009] [Indexed: 02/06/2023]
Abstract
AIMS/HYPOTHESIS Previous findings in rodents used as a model of diabetes suggest that insulin activation of atypical protein kinase C (aPKC) is impaired in muscle, but, unexpectedly, conserved in liver, despite impaired hepatic protein kinase B (PKB/Akt) activation. Moreover, aPKC at least partly regulates two major transactivators: (1) hepatic sterol receptor binding protein-1c (SREBP-1c), which controls lipid synthesis; and (2) nuclear factor kappa B (NFkappaB), which promotes inflammation and systemic insulin resistance. METHODS In Goto-Kakizaki rats used as a model of type 2 diabetes, we examined: (1) whether differences in hepatic aPKC and PKB activation reflect differences in activation of IRS-1- and IRS-2-dependent phosphatidylinositol 3-kinase (PI3K); (2) whether hepatic SREBP-1c and NFkappaB are excessively activated by aPKC; and (3) metabolic consequences of excessive activation of hepatic aPKC, SREBP-1c and NFkappaB. RESULTS In liver, as well as in muscle, IRS-2/PI3K activation by insulin was intact, whereas IRS-1/PI3K activation by insulin was impaired. Moreover, hepatic IRS-2 is known to control hepatic aPKC during insulin activation. Against this background, selective inhibition of hepatic aPKC by adenoviral-mediated expression of mRNA encoding kinase-inactive aPKC or short hairpin RNA targeting Irs2 mRNA and partially depleting hepatic IRS-2 diminished hepatic SREBP-1c production and NFkappaB activities, concomitantly improving serum lipids and insulin signalling in muscle and liver. Similar improvements in SREBP-1c, NFkappaB and insulin signalling were seen in ob/ob mice following inhibition of hepatic aPKC. CONCLUSIONS/INTERPRETATION In diabetic rodent liver, diminished PKB activation may largely reflect impaired IRS-1/PI3K activation, while conserved aPKC activation reflects retained IRS-2/PI3K activity. Hepatic aPKC may also contribute importantly to excessive SREPB-1c and NFkappaB activities. Excessive hepatic aPKC-dependent activation of SREBP-1c and NFkappaB may contribute importantly to hyperlipidaemia and systemic insulin resistance.
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Affiliation(s)
- M P Sajan
- Research Service, James A Haley Veterans Hospital, Tampa, FL 33612, USA
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26
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Awazawa M, Ueki K, Inabe K, Yamauchi T, Kaneko K, Okazaki Y, Bardeesy N, Ohnishi S, Nagai R, Kadowaki T. Adiponectin suppresses hepatic SREBP1c expression in an AdipoR1/LKB1/AMPK dependent pathway. Biochem Biophys Res Commun 2009; 382:51-6. [PMID: 19254698 DOI: 10.1016/j.bbrc.2009.02.131] [Citation(s) in RCA: 139] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2009] [Accepted: 02/22/2009] [Indexed: 02/08/2023]
Abstract
Adiponectin, one of the insulin-sensitizing adipokines, has been shown to activate fatty acid oxidation in liver and skeletal muscle, thus maintaining insulin sensitivity. However, the precise roles of adiponectin in fatty acid synthesis are poorly understood. Here we show that adiponectin administration acutely suppresses expression of sterol regulatory element-binding protein (SREBP) 1c, the master regulator which controls and upregulates the enzymes involved in fatty acid synthesis, in the liver of +Lepr(db)/+Lepr(db) (db/db) mouse as well as in cultured hepatocytes. We also show that adiponectin suppresses SREBP1c by AdipoR1, one of the functional receptors for adiponetin, and furthermore that suppressing either AMP-activated protein kinase (AMPK) via its upstream kinase LKB1 deletion cancels the negative effect of adiponectin on SREBP1c expression. These data show that adiponectin suppresses SREBP1c through the AdipoR1/LKB1/AMPK pathway, and suggest a possible role for adiponectin in the regulation of hepatic fatty acid synthesis.
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Affiliation(s)
- Motoharu Awazawa
- Department of Metabolic Diseases, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan
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27
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Sajan MP, Standaert ML, Nimal S, Varanasi U, Pastoor T, Mastorides S, Braun U, Leitges M, Farese RV. The critical role of atypical protein kinase C in activating hepatic SREBP-1c and NFkappaB in obesity. J Lipid Res 2009; 50:1133-45. [PMID: 19202134 DOI: 10.1194/jlr.m800520-jlr200] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Obesity is frequently associated with systemic insulin resistance, glucose intolerance, and hyperlipidemia. Impaired insulin action in muscle and paradoxical diet/insulin-dependent overproduction of hepatic lipids are important components of obesity, but their pathogenesis and inter-relationships between muscle and liver are uncertain. We studied two murine obesity models, moderate high-fat-feeding and heterozygous muscle-specific PKC-lambda knockout, in both of which insulin activation of atypical protein kinase C (aPKC) is impaired in muscle, but conserved in liver. In both models, activation of hepatic sterol receptor element binding protein-1c (SREBP-1c) and NFkappaB (nuclear factor-kappa B), major regulators of hepatic lipid synthesis and systemic insulin resistance, was chronically increased in the fed state. In support of a critical mediatory role of aPKC, in both models, inhibition of hepatic aPKC by adenovirally mediated expression of kinase-inactive aPKC markedly diminished diet/insulin-dependent activation of hepatic SREBP-1c and NFkappaB, and concomitantly improved hepatosteatosis, hypertriglyceridemia, hyperinsulinemia, and hyperglycemia. Moreover, in high-fat-fed mice, impaired insulin signaling to IRS-1-dependent phosphatidylinositol 3-kinase, PKB/Akt and aPKC in muscle and hyperinsulinemia were largely reversed. In obesity, conserved hepatic aPKC-dependent activation of SREBP-1c and NFkappaB contributes importantly to the development of hepatic lipogenesis, hyperlipidemia, and systemic insulin resistance. Accordingly, hepatic aPKC is a potential target for treating obesity-associated abnormalities.
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Affiliation(s)
- Mini P Sajan
- James A. Haley Veterans Hospital, Tampa, FL, USA
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28
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Ramocki NM, Wilkins HR, Magness ST, Simmons JG, Scull BP, Lee GH, McNaughton KK, Lund PK. Insulin receptor substrate-1 deficiency promotes apoptosis in the putative intestinal crypt stem cell region, limits Apcmin/+ tumors, and regulates Sox9. Endocrinology 2008; 149:261-7. [PMID: 17916629 PMCID: PMC2194604 DOI: 10.1210/en.2007-0869] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Reduced apoptosis of crypt stem/progenitor cells and elevated insulin and IGFs are linked to colon cancer risk. Insulin receptor substrate-1 (IRS-1) mediates the actions of insulin, IGF-I, and IGF-II, but the role of endogenous IRS-1 in crypt apoptosis and cancer is undefined. Using IRS-1(-/-), IRS-1(+/-), and IRS-1(+/+) mice, we tested the hypothesis that reduced IRS-1 expression increases apoptosis of intestinal crypt cells and protects against Apc(min/+) (Min)/beta-catenin-driven intestinal tumors. Expression of Sox9, a transcriptional target of Tcf/beta-catenin and putative biomarker of crypt stem cells, was assessed in intestine of different IRS-1 genotypes and cell lines. Irradiation-induced apoptosis was significantly increased in the crypts and crypt stem cell region of IRS-1-deficient mice. Tumor load was significantly reduced by 31.2 +/- 14.6% in IRS-1(+/-)/Min and by 64.1 +/- 7.6% in IRS-1(-/-)/Min mice, with more prominent reductions in tumor number than size. Compared with IRS-1(+/+)/Min, IRS-1(-/-)/Min mice had fewer Sox9-positive cells in intestinal crypts and reduced Sox9 mRNA in intestine. IRS-1 overexpression increased Sox9 expression in an intestinal epithelial cell line. We conclude that even small reductions in endogenous IRS-1 increase apoptosis of crypt stem or progenitor cells, protect against beta-catenin-driven intestinal tumors, and reduce Sox9, a Tcf/beta-catenin target and putative stem/progenitor cell biomarker.
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Affiliation(s)
- Nicole M Ramocki
- Department of Cell and Molecular Physiology, University of North Carolina at Chapel Hill, North Carolina 27599-7545, USA. or
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29
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Farese RV, Sajan MP, Yang H, Li P, Mastorides S, Gower WR, Nimal S, Choi CS, Kim S, Shulman GI, Kahn CR, Braun U, Leitges M. Muscle-specific knockout of PKC-lambda impairs glucose transport and induces metabolic and diabetic syndromes. J Clin Invest 2007. [PMID: 17641777 DOI: 10.1172/jci31408c1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Obesity, the metabolic syndrome, and type 2 diabetes mellitus (T2DM) are major global health problems. Insulin resistance is frequently present in these disorders, but the causes and effects of such resistance are unknown. Here, we generated mice with muscle-specific knockout of the major murine atypical PKC (aPKC), PKC-lambda, a postulated mediator for insulin-stimulated glucose transport. Glucose transport and translocation of glucose transporter 4 (GLUT4) to the plasma membrane were diminished in muscles of both homozygous and heterozygous PKC-lambda knockout mice and were accompanied by systemic insulin resistance; impaired glucose tolerance or diabetes; islet beta cell hyperplasia; abdominal adiposity; hepatosteatosis; elevated serum triglycerides, FFAs, and LDL-cholesterol; and diminished HDL-cholesterol. In contrast to the defective activation of muscle aPKC, insulin signaling and actions were intact in muscle, liver, and adipocytes. These findings demonstrate the importance of aPKC in insulin-stimulated glucose transport in muscles of intact mice and show that insulin resistance and resultant hyperinsulinemia owing to a specific defect in muscle aPKC is sufficient to induce abdominal obesity and other lipid abnormalities of the metabolic syndrome and T2DM. These findings are particularly relevant because humans who have obesity, impaired glucose tolerance, and T2DM reportedly have defective activation and/or diminished levels of muscle aPKC.
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Affiliation(s)
- Robert V Farese
- James A. Haley Veterans Medical Center, Tampa, Florida 33612, USA.
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30
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Farese RV, Sajan MP, Yang H, Li P, Mastorides S, Gower WR, Nimal S, Choi CS, Kim S, Shulman GI, Kahn CR, Braun U, Leitges M. Muscle-specific knockout of PKC-lambda impairs glucose transport and induces metabolic and diabetic syndromes. J Clin Invest 2007; 117:2289-301. [PMID: 17641777 PMCID: PMC1913489 DOI: 10.1172/jci31408] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2007] [Accepted: 05/08/2007] [Indexed: 12/11/2022] Open
Abstract
Obesity, the metabolic syndrome, and type 2 diabetes mellitus (T2DM) are major global health problems. Insulin resistance is frequently present in these disorders, but the causes and effects of such resistance are unknown. Here, we generated mice with muscle-specific knockout of the major murine atypical PKC (aPKC), PKC-lambda, a postulated mediator for insulin-stimulated glucose transport. Glucose transport and translocation of glucose transporter 4 (GLUT4) to the plasma membrane were diminished in muscles of both homozygous and heterozygous PKC-lambda knockout mice and were accompanied by systemic insulin resistance; impaired glucose tolerance or diabetes; islet beta cell hyperplasia; abdominal adiposity; hepatosteatosis; elevated serum triglycerides, FFAs, and LDL-cholesterol; and diminished HDL-cholesterol. In contrast to the defective activation of muscle aPKC, insulin signaling and actions were intact in muscle, liver, and adipocytes. These findings demonstrate the importance of aPKC in insulin-stimulated glucose transport in muscles of intact mice and show that insulin resistance and resultant hyperinsulinemia owing to a specific defect in muscle aPKC is sufficient to induce abdominal obesity and other lipid abnormalities of the metabolic syndrome and T2DM. These findings are particularly relevant because humans who have obesity, impaired glucose tolerance, and T2DM reportedly have defective activation and/or diminished levels of muscle aPKC.
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Affiliation(s)
- Robert V Farese
- James A. Haley Veterans Medical Center, Tampa, Florida 33612, USA.
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31
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Ma K, Saha PK, Chan L, Moore DD. Farnesoid X receptor is essential for normal glucose homeostasis. J Clin Invest 2006; 116:1102-9. [PMID: 16557297 PMCID: PMC1409738 DOI: 10.1172/jci25604] [Citation(s) in RCA: 655] [Impact Index Per Article: 36.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2005] [Accepted: 01/31/2006] [Indexed: 12/13/2022] Open
Abstract
The bile acid receptor farnesoid X receptor (FXR; NR1H4) is a central regulator of bile acid and lipid metabolism. We show here that FXR plays a key regulatory role in glucose homeostasis. FXR-null mice developed severe fatty liver and elevated circulating FFAs, which was associated with elevated serum glucose and impaired glucose and insulin tolerance. Their insulin resistance was confirmed by the hyperinsulinemic euglycemic clamp, which showed attenuated inhibition of hepatic glucose production by insulin and reduced peripheral glucose disposal. In FXR-/- skeletal muscle and liver, multiple steps in the insulin signaling pathway were markedly blunted. In skeletal muscle, which does not express FXR, triglyceride and FFA levels were increased, and we propose that their inhibitory effects account for insulin resistance in that tissue. In contrast to the results in FXR-/- mice, bile acid activation of FXR in WT mice repressed expression of gluconeogenic genes and decreased serum glucose. The absence of this repression in both FXR-/- and small heterodimer partner-null (SHP-/-) mice demonstrated that the previously described FXR-SHP nuclear receptor cascade also targets glucose metabolism. Taken together, our results identify a link between lipid and glucose metabolism mediated by the FXR-SHP cascade.
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Affiliation(s)
- Ke Ma
- Department of Molecular and Cellular Biology and
Section of Endocrinology and Metabolism, Departments of Molecular and Cellular Biology and Medicine, Baylor College of Medicine, Houston, Texas, USA
| | - Pradip K. Saha
- Department of Molecular and Cellular Biology and
Section of Endocrinology and Metabolism, Departments of Molecular and Cellular Biology and Medicine, Baylor College of Medicine, Houston, Texas, USA
| | - Lawrence Chan
- Department of Molecular and Cellular Biology and
Section of Endocrinology and Metabolism, Departments of Molecular and Cellular Biology and Medicine, Baylor College of Medicine, Houston, Texas, USA
| | - David D. Moore
- Department of Molecular and Cellular Biology and
Section of Endocrinology and Metabolism, Departments of Molecular and Cellular Biology and Medicine, Baylor College of Medicine, Houston, Texas, USA
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32
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Taniguchi CM, Ueki K, Kahn R. Complementary roles of IRS-1 and IRS-2 in the hepatic regulation of metabolism. J Clin Invest 2005; 115:718-27. [PMID: 15711641 PMCID: PMC548317 DOI: 10.1172/jci23187] [Citation(s) in RCA: 199] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2004] [Accepted: 12/21/2004] [Indexed: 01/07/2023] Open
Abstract
Hepatic insulin resistance is a critical component in the development of type 2 diabetes mellitus. In many cases, insulin resistance in liver is associated with reduced expression of both major insulin receptor substrate (IRS) proteins, IRS-1 and IRS-2. To investigate the specific functions of IRS-1 and IRS-2 in regulating liver function in vivo, we developed an adenovirus-mediated RNA interference technique in which short hairpin RNAs (shRNAs) are used to knock down IRS-1, IRS-2, or both, by 70-80% in livers of WT mice. The knockdown of IRS-1 resulted in an upregulation of the gluconeogenic enzymes glucose-6 phosphatase and phosphoenolpyruvate carboxykinase, as well as a marked increase in hepatic nuclear factor-4 alpha. Decreased IRS-1 was also associated with a decrease in glucokinase expression and a trend toward increased blood glucose, whereas knockdown of IRS-2 resulted in the upregulation of lipogenic enzymes SREBP-1c and fatty acid synthase, as well as increased hepatic lipid accumulation. The concomitant injection of IRS-1 and IRS-2 adenoviral shRNAs resulted in systemic insulin resistance, glucose intolerance, and hepatic steatosis. The alterations in the dual-knockdown mice were associated with defective Akt activation and Foxo1 phosphorylation. Taken together, our results demonstrate that hepatic IRS-1 and IRS-2 have complementary roles in the control of hepatic metabolism, with IRS-1 more closely linked to glucose homeostasis and IRS-2 more closely linked to lipid metabolism.
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Affiliation(s)
- Cullen M Taniguchi
- Research Division, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts, USA
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33
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Haj FG, Zabolotny JM, Kim YB, Kahn BB, Neel BG. Liver-specific Protein-tyrosine Phosphatase 1B (PTP1B) Re-expression Alters Glucose Homeostasis of PTP1B–/–Mice. J Biol Chem 2005; 280:15038-46. [PMID: 15699041 DOI: 10.1074/jbc.m413240200] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Protein-tyrosine phosphatase 1B (PTP1B) is an important negative regulator of insulin and leptin signaling in vivo. Mice lacking PTP1B (PTP1B-/- mice) are hyper-responsive to insulin and leptin and resistant to diet-induced obesity. The tissue(s) that mediate these effects of global PTP1B deficiency remain controversial. We exploited the high degree of hepatotropism of adenoviruses to assess the role of PTP1B in the liver. Liver-specific re-expression of PTP1B in PTP1B-/- mice led to marked attenuation of their enhanced insulin sensitivity. This correlated with, and was probably caused by, decreased insulin-stimulated tyrosyl phosphorylation of the insulin receptor (IR) and IR substrate 2-associated phosphatidylinositide 3-kinase activity. Analysis using phospho-specific antibodies for the IR revealed preferential dephosphorylation of Tyr-1162/1163 compared with Tyr-972 by PTP1B in vivo. Our findings show that the liver is a major site of the peripheral action of PTP1B in regulating glucose homeostasis.
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Affiliation(s)
- Fawaz G Haj
- Cancer Biology Program, Division of Hematology-Oncology, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, 02215, USA
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34
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Kawaguchi T, Yoshida T, Harada M, Hisamoto T, Nagao Y, Ide T, Taniguchi E, Kumemura H, Hanada S, Maeyama M, Baba S, Koga H, Kumashiro R, Ueno T, Ogata H, Yoshimura A, Sata M. Hepatitis C virus down-regulates insulin receptor substrates 1 and 2 through up-regulation of suppressor of cytokine signaling 3. THE AMERICAN JOURNAL OF PATHOLOGY 2004; 165:1499-508. [PMID: 15509521 PMCID: PMC1618659 DOI: 10.1016/s0002-9440(10)63408-6] [Citation(s) in RCA: 423] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The pathogenesis of hepatitis C virus (HCV)-associated insulin resistance remains unclear. Therefore, we investigated mechanisms for HCV-associated insulin resistance. Homeostasis model assessment for insulin resistance was increased in patients with HCV infection. An increase in fasting insulin levels was associated with the presence of serum HCV core, the severity of hepatic fibrosis and a decrease in expression of insulin receptor substrate (IRS) 1 and IRS2, central molecules of the insulin-signaling cascade, in patients with HCV infection. Down-regulation of IRS1 and IRS2 was also seen in HCV core-transgenic mice livers and HCV core-transfected human hepatoma cells. Carbobenzoxy-l-leucyl-l-leucyl-l-leucinal, a potent proteosomal proteolysis inhibitor, blocked down-regulation of IRS1 and IRS2 in HCV core-transfected hepatoma cells. In human hepatoma cells, HCV core up-regulated suppressor of cytokine signaling (SOCS) 3 and caused ubiquitination of IRS1 and IRS2. HCV core-induced down-regulation of IRS1 and IRS2 was not seen in SOCS3(-/-) mouse embryonic fibroblast cells. Furthermore, HCV core suppressed insulin-induced phosphorylation of p85 subunit of phosphatidylinositol 3-kinase and Akt, activation of 6-phosphofructo-2-kinase, and glucose uptake. In conclusion, HCV infection changes a subset of hepatic molecules regulating glucose metabolism. A possible mechanism is that HCV core-induced SOCS3 promotes proteosomal degradation of IRS1 and IRS2 through ubiquitination.
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Affiliation(s)
- Takumi Kawaguchi
- Second Department of Medicine, Kurume University School of Medicine. 67 Asahi-machi, Kurume 830-0011, Japan.
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35
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Oshikawa J, Otsu K, Toya Y, Tsunematsu T, Hankins R, Kawabe JI, Minamisawa S, Umemura S, Hagiwara Y, Ishikawa Y. Insulin resistance in skeletal muscles of caveolin-3-null mice. Proc Natl Acad Sci U S A 2004; 101:12670-5. [PMID: 15314230 PMCID: PMC515114 DOI: 10.1073/pnas.0402053101] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Type 2 diabetes is preceded by the development of insulin resistance, in which the action of insulin is impaired, largely in skeletal muscles. Caveolin-3 (Cav3) is a muscle-specific subtype of caveolin, an example of a scaffolding protein found within membranes. Cav is also known as growth signal inhibitor, although it was recently demonstrated that the genetic disruption of Cav3 did not augment growth in mice. We found, however, that the lack of Cav3 led to the development of insulin resistance, as exemplified by decreased glucose uptake in skeletal muscles, impaired glucose tolerance test performance, and increases in serum lipids. Such impairments were markedly augmented in the presence of streptozotocin, a pancreatic beta cell toxin, suggesting that the mice were susceptible to severe diabetes in the presence of an additional risk factor. Insulin-stimulated activation of insulin receptors and downstream molecules, such as IRS-1 and Akt, was attenuated in the skeletal muscles of Cav3 null mice, but not in the liver, without affecting protein expression or subcellular localization. Genetic transfer of Cav3 by needle injection restored insulin signaling in skeletal muscles. Our findings suggest that Cav3 is an enhancer of insulin signaling in skeletal muscles but does not act as a scaffolding molecule for insulin receptors.
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Affiliation(s)
- Jin Oshikawa
- Departments of Physiology and Medicine, Yokohama City University School of Medicine, 3-9 Fukuura Kanazawa, Yokohama 236-0004, Japan
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36
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Li L, Grønning LM, Anderson PO, Li S, Edvardsen K, Johnston J, Kioussis D, Shepherd PR, Wang P. Insulin Induces SOCS-6 Expression and Its Binding to the p85 Monomer of Phosphoinositide 3-Kinase, Resulting in Improvement in Glucose Metabolism. J Biol Chem 2004; 279:34107-14. [PMID: 15123678 DOI: 10.1074/jbc.m312672200] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The suppressors of cytokine signaling (SOCS) family is thought to act largely as a negative regulator of signaling by cytokines and some growth factors. Surprisingly, the SOCS-6 transgenics had no significant defects in the cytokine signaling and hematopoietic system but displayed significant improvements in glucose metabolism. Insulin stimulation of Akt/protein kinase B was also potentiated. Biochemical analysis showed that, after insulin stimulation, SOCS-6 interacted with the monomeric p85 subunit of class-Ia phosphoinositide (PI) 3-kinase but not with p85/p110 dimers. Furthermore, SOCS-6 expression is transiently increased by serum and insulin in normal fibroblasts. However, both the mRNA and protein of SOCS-6 were rapidly degraded after induction by insulin. The degradation of the SOCS-6 protein was partially inhibited by a proteasome inhibitor, suggesting a proteasome-mediated degradation mechanism. In contrast, SOCS-6-associated p85 was not degraded and could be recruited to the newly synthesized SOCS-6 molecules in the presence of insulin, suggesting that SOCS-6 expression and its interaction with p85, but not the degradation, is regulated by insulin. The phenotype of SOCS-6 transgenic mice bears a striking resemblance to p85 knock-out mouse models in which glucose metabolism stimulated by insulin is significantly improved despite reduced activation of PI 3-kinase. This suggests that monomeric p85 might play a physiologically important role in attenuating signaling through PI 3-kinase-dependent pathways in unstimulated cells. Therefore, our results indicate that SOCS-6 may provide a dynamically regulated mechanism by which insulin can transiently overcome the negative effects that p85 monomers have on signaling via PI 3-kinase-dependent signaling pathways.
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Affiliation(s)
- Li Li
- Immunology Group, Institute of Cell and Molecular Sciences, St. Barts and The Royal London School of Medicine, 59 Bartholomew's Close, London EC1A 7ED, United Kingdom
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37
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Ueki K, Kondo T, Tseng YH, Kahn CR. Central role of suppressors of cytokine signaling proteins in hepatic steatosis, insulin resistance, and the metabolic syndrome in the mouse. Proc Natl Acad Sci U S A 2004; 101:10422-7. [PMID: 15240880 PMCID: PMC478587 DOI: 10.1073/pnas.0402511101] [Citation(s) in RCA: 282] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Insulin resistance, obesity, diabetes, dyslipidemia, and nonalcoholic fatty liver are components of the metabolic syndrome, a disease complex that is increasing at epidemic rates in westernized countries. Although proinflammatory cytokines have been suggested to contribute to the development of these disorders, the molecular mechanism is poorly understood. Here we show that overexpression of suppressors of cytokine signaling (SOCS)-1 and SOCS-3 in liver causes insulin resistance and an increase in the key regulator of fatty acid synthesis in liver, sterol regulatory element-binding protein (SREBP)-1c. Conversely, inhibition of SOCS-1 and -3 in obese diabetic mice improves insulin sensitivity, normalizes the increased expression of SREBP-1c, and dramatically ameliorates hepatic steatosis and hypertriglyceridemia. In obese animals, increased SOCS proteins enhance SREBP-1c expression by antagonizing STAT3-mediated inhibition of SREBP-1c promoter activity. Thus, SOCS proteins play an important role in pathogenesis of the metabolic syndrome by concordantly modulating insulin signaling and cytokine signaling.
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Affiliation(s)
- Kohjiro Ueki
- Research Division, Joslin Diabetes Center and Department of Medicine, Harvard Medical School, Boston, MA 02215, USA
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38
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Ueki K, Kondo T, Kahn CR. Suppressor of cytokine signaling 1 (SOCS-1) and SOCS-3 cause insulin resistance through inhibition of tyrosine phosphorylation of insulin receptor substrate proteins by discrete mechanisms. Mol Cell Biol 2004; 24:5434-46. [PMID: 15169905 PMCID: PMC419873 DOI: 10.1128/mcb.24.12.5434-5446.2004] [Citation(s) in RCA: 492] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Insulin resistance is a pathophysiological component of type 2 diabetes and obesity and also occurs in states of stress, infection, and inflammation associated with an upregulation of cytokines. Here we show that in both obesity and lipopolysaccharide (LPS)-induced endotoxemia there is an increase in suppressor of cytokine signaling (SOCS) proteins, SOCS-1 and SOCS-3, in liver, muscle, and, to a lesser extent, fat. In concordance with these increases by LPS, tyrosine phosphorylation of the insulin receptor (IR) is partially impaired and phosphorylation of the insulin receptor substrate (IRS) proteins is almost completely suppressed. Direct overexpression of SOCS-3 in liver by adenoviral-mediated gene transfer markedly decreases tyrosine phosphorylation of both IRS-1 and IRS-2, while SOCS-1 overexpression preferentially inhibits IRS-2 phosphorylation. Neither affects IR phosphorylation, although both SOCS-1 and SOCS-3 bind to the insulin receptor in vivo in an insulin-dependent fashion. Experiments with cultured cells expressing mutant insulin receptors reveal that SOCS-3 binds to Tyr960 of IR, a key residue for the recognition of IRS-1 and IRS-2, whereas SOCS-1 binds to the domain in the catalytic loop essential for IRS-2 recognition in vitro. Moreover, overexpression of either SOCS-1 or SOCS-3 attenuates insulin-induced glycogen synthesis in L6 myotubes and activation of glucose uptake in 3T3L1 adipocytes. By contrast, a reduction of SOCS-1 or SOCS-3 by antisense treatment partially restores tumor necrosis factor alpha-induced downregulation of tyrosine phosphorylation of IRS proteins in 3T3L1 adipocytes. These data indicate that SOCS-1 and SOCS-3 act as negative regulators in insulin signaling and serve as one of the missing links between insulin resistance and cytokine signaling.
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Affiliation(s)
- Kohjiro Ueki
- Research Division, Joslin Diabetes Center, and Departmentof Medicine, Harvard Medical School, Boston, MA 02215, USA
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39
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Standaert ML, Sajan MP, Miura A, Kanoh Y, Chen HC, Farese RV, Farese RV. Insulin-induced Activation of Atypical Protein Kinase C, but Not Protein Kinase B, Is Maintained in Diabetic (ob/ob and Goto-Kakazaki) Liver. J Biol Chem 2004; 279:24929-34. [PMID: 15069067 DOI: 10.1074/jbc.m402440200] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Insulin resistance in type 2 diabetes is characterized by defects in muscle glucose uptake and hepatic overproduction of both glucose and lipids. These hepatic defects are perplexing because insulin normally suppresses glucose production and increases lipid synthesis in the liver. To understand the mechanisms for these seemingly paradoxical defects, we examined the activation of atypical protein kinase C (aPKC) and protein kinase B (PKB), two key signaling factors that operate downstream of phosphatidylinositol 3-kinase and regulate various insulin-sensitive metabolic processes. Livers and muscles of three insulin-resistant rodent models were studied. In livers of type 2 diabetic non-obese Goto-Kakazaki rats and ob/ob-diabetic mice, the activation of PKB was impaired, whereas activation of aPKC was surprisingly maintained. In livers of non-diabetic high fatfed mice, the activation of both aPKC and PKB was maintained. In contrast to the maintenance of aPKC activation in the liver, insulin activation of aPKC was impaired in muscles of Goto-Kakazaki-diabetic rats and ob/ob-diabetic and non-diabetic high fat-fed mice. These findings suggest that, at least in these rodent models, (a) defects in aPKC activation contribute importantly to skeletal muscle insulin resistance observed in both high fat feeding and type 2 diabetes; (b) insulin signaling defects in muscle are not necessarily accompanied by similar defects in liver; (c) defects in hepatic PKB activation occur in association with, and probably contribute importantly to, the development of overt diabetes; and (d) maintenance of hepatic aPKC activation may explain the continued effectiveness of insulin for stimulating certain metabolic actions in the liver.
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Affiliation(s)
- Mary L Standaert
- Research Service, James A. Haley Veterans Medical Center and Department of Internal Medicine, University of South Florida College of Medicine, Tampa, Florida 33612, USA
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40
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Giannoukakis N, Robbins PD. Gene and cell therapies for diabetes mellitus: strategies and clinical potential. BioDrugs 2003; 16:149-73. [PMID: 12102644 DOI: 10.2165/00063030-200216030-00001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The last 5 years have witnessed an explosion in the use of genes and cells as biomedicines. While primarily aimed at cancer, gene engineering and cell therapy strategies have additionally been used for Mendelian, neurodegenerative and metabolic disorders. The main focus of gene and cell therapy strategies in metabolism has been diabetes mellitus. This disease is a disorder of glucose homeostasis, either due to the immune-mediated eradication of pancreatic beta cells in the islets of Langerhans (type 1 diabetes) or resulting from insulin resistance and obesity syndromes where the insulin-producing capability of the beta cell is ultimately exhausted in the face of insensitivity to the effects of insulin in the peripheral glucose-utilising tissues (type 2 diabetes). A significant number of animal studies have demonstrated the potential in restoring normoglycaemia by islet transplantation in the context of immunoregulation achieved by gene transfer of immunoregulatory genes to allo- and xenogeneic islets ex vivo. Additionally, gene and cell therapy has also been used to induce tolerance to auto- and alloantigens and to generate the tolerant state in autoimmune rodent animal models of type 1 diabetes or rodent recipients of allogeneic/xenogeneic islet transplants. The achievements of gene and cell therapy in type 2 diabetes are less evident, but seminal studies promise that this modality can be relevant to treat and perhaps prevent the underlying causes of the disease. Here we present an overview of the current status of gene and cell therapy for type 1 and 2 diabetes and we propose potential therapeutic options that could be clinically useful. For type 1 diabetes, transplantation of islets engineered to evade or suppress the recipient immune response is the most readily-available technology today. A number of gene delivery vectors encoding proteins that impair a variety of immune cells have already been examined and proven versatile. More challenging but, nonetheless, just over the horizon are attempts to promote tolerance to islet allografts. Type 2 diabetes will likely require a better understanding of the processes that determine insulin sensitivity in the periphery. Targeting tissues such as muscle and fat with vectors encoding genes whose products promote insulin sensitivity and glucose uptake is an approach that does not carry with it the side-effects often associated with pharmacologic agents currently in use. In the end, progress in vector design, elucidation of antigen-specific immunity and insulin sensitivity will provide the framework for gene drug use in the treatment of type 1 and type 2 diabetes.
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Affiliation(s)
- Nick Giannoukakis
- Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA.
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Yamauchi T, Kamon J, Minokoshi Y, Ito Y, Waki H, Uchida S, Yamashita S, Noda M, Kita S, Ueki K, Eto K, Akanuma Y, Froguel P, Foufelle F, Ferre P, Carling D, Kimura S, Nagai R, Kahn BB, Kadowaki T. Adiponectin stimulates glucose utilization and fatty-acid oxidation by activating AMP-activated protein kinase. Nat Med 2002; 8:1288-95. [PMID: 12368907 DOI: 10.1038/nm788] [Citation(s) in RCA: 2987] [Impact Index Per Article: 135.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2002] [Accepted: 09/19/2002] [Indexed: 02/07/2023]
Abstract
Adiponectin (Ad) is a hormone secreted by adipocytes that regulates energy homeostasis and glucose and lipid metabolism. However, the signaling pathways that mediate the metabolic effects of Ad remain poorly identified. Here we show that phosphorylation and activation of the 5'-AMP-activated protein kinase (AMPK) are stimulated with globular and full-length Ad in skeletal muscle and only with full-length Ad in the liver. In parallel with its activation of AMPK, Ad stimulates phosphorylation of acetyl coenzyme A carboxylase (ACC), fatty-acid oxidation, glucose uptake and lactate production in myocytes, phosphorylation of ACC and reduction of molecules involved in gluconeogenesis in the liver, and reduction of glucose levels in vivo. Blocking AMPK activation by dominant-negative mutant inhibits each of these effects, indicating that stimulation of glucose utilization and fatty-acid oxidation by Ad occurs through activation of AMPK. Our data may provide a novel paradigm that an adipocyte-derived antidiabetic hormone, Ad, activates AMPK, thereby directly regulating glucose metabolism and insulin sensitivity in vitro and in vivo.
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Affiliation(s)
- T Yamauchi
- Department of Internal Medicine, Graduate School of Medicine, University of Tokyo, Tokyo, Japan
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Meyer MM, Levin K, Grimmsmann T, Perwitz N, Eirich A, Beck-Nielsen H, Klein HH. Troglitazone treatment increases protein kinase B phosphorylation in skeletal muscle of normoglycemic subjects at risk for the development of type 2 diabetes. Diabetes 2002; 51:2691-7. [PMID: 12196460 DOI: 10.2337/diabetes.51.9.2691] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
We investigated whether the effect of troglitazone on glucose disposal is associated with altered insulin signaling. Nondiabetic first-degree relatives of type 2 diabetic patients (age 30 +/- 2 years, BMI 30 +/- 1 kg/m(2); n = 20) were randomized in a double-blind manner to 3 months of troglitazone (200 mg/day) or placebo treatment. Before and after treatment, 3-h euglycemic-hyperinsulinemic glucose clamps (40 mU. m(-2). min(-1)) were performed, and muscle biopsies were obtained immediately before and after the clamps. In the biopsies, insulin receptor kinase (IRK) activity, insulin receptor substrate (IRS)-1-associated phosphatidylinositol 3-kinase (PI3K) activity, Ser(473) and Thr(308) phosphorylation of protein kinase B (PKB), and protein expression of IRS-1, IRS-2, phosphoinositol-dependent kinase-1 (PDK-1), PKB, and GLUT-4 were determined. After troglitazone treatment, insulin-stimulated glucose disposal was increased compared with pretreatment and placebo (279 +/- 37 vs. 211 +/- 26 and 200 +/- 25 mg. m(-2). min(-1); both P < 0.05). IRK and PI3K activities were not altered by troglitazone, but PKB Ser(473) phosphorylation was enhanced compared with pretreatment and placebo at the clamp insulin level (138 +/- 36 vs. 77 +/- 16 and 55 +/- 13 internal standard units; both P < 0.05) and with pretreatment at the basal level (31 +/- 9 vs. 14 +/- 4 internal standard units; P < 0.05). PKB Thr(308) phosphorylation also tended to be higher, but this was not statistically significant. Troglitazone did not alter insulin receptor number or IRS-1, IRS-2, PKB, PDK-1, or GLUT-4 protein expression. We conclude that increased PKB phosphorylation may contribute to the insulin-sensitizing effects of thiazolidinediones in human skeletal muscle.
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Affiliation(s)
- Marco M Meyer
- Medizinische Klinik 1, Medizinische Universität zu Lübeck, Lübeck, Germany
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43
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Leitges M, Plomann M, Standaert ML, Bandyopadhyay G, Sajan MP, Kanoh Y, Farese RV, Letiges M. Knockout of PKC alpha enhances insulin signaling through PI3K. Mol Endocrinol 2002; 16:847-58. [PMID: 11923480 DOI: 10.1210/mend.16.4.0809] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Insulin stimulates glucose transport and certain other metabolic processes by activating atypical PKC isoforms (lambda, zeta, iota) and protein kinase B (PKB) through increases in D3-polyphosphoinositides derived from the action of PI3K. The role of diacylglycerol-sensitive PKC isoforms is less clear as they have been suggested to be both activated by insulin and yet inhibit insulin signaling to PI3K. Presently, we found that insulin signaling to insulin receptor substrate 1-dependent PI3K, PKB, and PKC lambda, and downstream processes, glucose transport and activation of ERK, were enhanced in skeletal muscles and adipocytes of mice in which the ubiquitous conventional diacylglycerol-sensitive PKC isoform, PKC alpha, was knocked out by homologous recombination. On the other hand, insulin provoked wortmannin-insensitive increases in immunoprecipitable PKC alpha activity in adipocytes and skeletal muscles of wild-type mice and rats. We conclude that 1) PKC alpha is not required for insulin-stimulated glucose transport, and 2) PKC alpha is activated by insulin at least partly independently of PI3K, and largely serves as a physiological feedback inhibitor of insulin signaling to the insulin receptor substrate 1/PI3K/PKB/PKC lambda/zeta/iota complex and dependent metabolic processes.
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Affiliation(s)
- Michael Leitges
- Max-Planck Institute for Experimental Endocrinology, 30625 Hannover, Germany
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44
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Mauvais-Jarvis F, Ueki K, Fruman DA, Hirshman MF, Sakamoto K, Goodyear LJ, Iannacone M, Accili D, Cantley LC, Kahn CR. Reduced expression of the murine p85alpha subunit of phosphoinositide 3-kinase improves insulin signaling and ameliorates diabetes. J Clin Invest 2002; 109:141-9. [PMID: 11781359 PMCID: PMC150818 DOI: 10.1172/jci13305] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
A critical component of insulin action is the enzyme phosphoinositide (PI) 3-kinase. The major regulatory subunits of PI 3-kinase, p85alpha and its splice variants, are encoded by the Pik3r1 gene. Heterozygous disruption of Pik3r1 improves insulin signaling and glucose homeostasis in normal mice and mice made insulin-resistant by heterozygous deletion of the Insulin receptor and/or insulin receptor substrate-1 (IRS1) genes. Reduced expression of p85 modulates the molecular balance between this protein, the p110 catalytic subunit of PI 3-kinase, and the IRS proteins. Thus, despite the decrease in p85alpha, PI 3-kinase activation is normal, insulin-stimulated Akt activity is increased, and glucose tolerance and insulin sensitivity are improved. Furthermore, Pik3r1 heterozygosity protects mice with genetic insulin resistance from developing diabetes. These data suggest that regulation of p85alpha levels may provide a novel therapeutic target for the treatment of type 2 diabetes.
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MESH Headings
- Alleles
- Animals
- Diabetes Mellitus, Experimental/enzymology
- Diabetes Mellitus, Experimental/genetics
- Diabetes Mellitus, Experimental/physiopathology
- Diabetes Mellitus, Type 2/enzymology
- Diabetes Mellitus, Type 2/genetics
- Diabetes Mellitus, Type 2/physiopathology
- Heterozygote
- Insulin/physiology
- Insulin Receptor Substrate Proteins
- Insulin Resistance/genetics
- Insulin Resistance/physiology
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Mice, Mutant Strains
- Phosphatidylinositol 3-Kinases/chemistry
- Phosphatidylinositol 3-Kinases/genetics
- Phosphatidylinositol 3-Kinases/metabolism
- Phosphoproteins/genetics
- Protein Subunits
- Receptor, Insulin/genetics
- Signal Transduction
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Affiliation(s)
- Franck Mauvais-Jarvis
- Research Division, Joslin Diabetes Center and Department of Medicine, Harvard Medical School, Boston, Massachusetts 02115, USA
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Mauvais-Jarvis F, Ueki K, Fruman DA, Hirshman MF, Sakamoto K, Goodyear LJ, Iannacone M, Accili D, Cantley LC, Kahn CR. Reduced expression of the murine p85α subunit of phosphoinositide 3-kinase improves insulin signaling and ameliorates diabetes. J Clin Invest 2002. [DOI: 10.1172/jci0213305] [Citation(s) in RCA: 176] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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