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Bo T, Gao L, Yao Z, Shao S, Wang X, Proud CG, Zhao J. Hepatic selective insulin resistance at the intersection of insulin signaling and metabolic dysfunction-associated steatotic liver disease. Cell Metab 2024; 36:947-968. [PMID: 38718757 DOI: 10.1016/j.cmet.2024.04.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Revised: 01/22/2024] [Accepted: 04/09/2024] [Indexed: 06/26/2024]
Abstract
Insulin resistance (IR) is a major pathogenic factor in the progression of MASLD. In the liver, insulin suppresses gluconeogenesis and enhances de novo lipogenesis (DNL). During IR, there is a defect in insulin-mediated suppression of gluconeogenesis, but an unrestrained increase in hepatic lipogenesis persists. The mechanism of increased hepatic steatosis in IR is unclear and remains controversial. The key discrepancy is whether insulin retains its ability to directly regulate hepatic lipogenesis. Blocking insulin/IRS/AKT signaling reduces liver lipid deposition in IR, suggesting insulin can still regulate lipid metabolism; hepatic glucose metabolism that bypasses insulin's action may contribute to lipogenesis; and due to peripheral IR, other tissues are likely to impact liver lipid deposition. We here review the current understanding of insulin's action in governing different aspects of hepatic lipid metabolism under normal and IR states, with the purpose of highlighting the essential issues that remain unsettled.
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Affiliation(s)
- Tao Bo
- Key Laboratory of Endocrine Glucose & Lipids Metabolism and Brain Aging, Ministry of Education, Department of Endocrinology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong, China; Central Laboratory, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong, China; Medical Science and Technology Innovation Center, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, Shandong, China
| | - Ling Gao
- Key Laboratory of Endocrine Glucose & Lipids Metabolism and Brain Aging, Ministry of Education, Department of Endocrinology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong, China; Central Laboratory, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong, China; Shandong Key Laboratory of Endocrinology and Lipid Metabolism, Jinan, Shandong, China
| | - Zhenyu Yao
- Key Laboratory of Endocrine Glucose & Lipids Metabolism and Brain Aging, Ministry of Education, Department of Endocrinology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong, China; Shandong Key Laboratory of Endocrinology and Lipid Metabolism, Jinan, Shandong, China
| | - Shanshan Shao
- Key Laboratory of Endocrine Glucose & Lipids Metabolism and Brain Aging, Ministry of Education, Department of Endocrinology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong, China; Shandong Key Laboratory of Endocrinology and Lipid Metabolism, Jinan, Shandong, China
| | - Xuemin Wang
- Lifelong Health, South Australian Health & Medical Research Institute, North Terrace, Adelaide, SA, Australia
| | - Christopher G Proud
- Lifelong Health, South Australian Health & Medical Research Institute, North Terrace, Adelaide, SA, Australia.
| | - Jiajun Zhao
- Key Laboratory of Endocrine Glucose & Lipids Metabolism and Brain Aging, Ministry of Education, Department of Endocrinology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong, China; Shandong Key Laboratory of Endocrinology and Lipid Metabolism, Jinan, Shandong, China.
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Ye X, Chen W, Huang XF, Yan FJ, Deng SG, Zheng XD, Shan PF. Anti-diabetic effect of anthocyanin cyanidin-3-O-glucoside: data from insulin resistant hepatocyte and diabetic mouse. Nutr Diabetes 2024; 14:7. [PMID: 38429305 PMCID: PMC10907696 DOI: 10.1038/s41387-024-00265-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Revised: 02/07/2024] [Accepted: 02/15/2024] [Indexed: 03/03/2024] Open
Abstract
BACKGROUND Anthocyanins are a group of natural products widely found in plants. They have been found to alleviate the disorders of glucose metabolism in type 2 diabetes mellitus (T2DM), while the underlying mechanisms remain unclear. METHODS HepG2 and L02 cells were incubated with 0.2 mM PA and 30 mM glucose for 24 h to induce IR, and cells treated with 5 mM glucose were used as the control. C57BL/6 J male mice and db/db male mice were fed with a chow diet and gavaged with pure water or cyanidin-3-O-glucoside (C3G) solution (150 mg/kg/day) for 6 weeks. RESULTS In this study, the anthocyanin C3G, extracted from red bayberry, was found to alleviate disorders of glucose metabolism, which resulted in increased insulin sensitivity in hepatocytes, and achieved by enhancing the glucose consumption as well as glycogen synthesis in insulin resistance (IR) hepatpcytes. Subsequently, the expression of key proteins involved in IR was detected by western blotting analysis. Protein tyrosine phosphatase-1B (PTP1B), a negative regulator of insulin signaling, could reduce cellular sensitivity to insulin by inhibiting the phosphorylation of insulin receptor substrate-2 (IRS-2). Results of this study showed that C3G inhibited the increase in PTP1B after high glucose and palmitic acid treatment. And this inhibition was accompanied by increased phosphorylation of IRS proteins. Furthermore, the effect of C3G on improving IR in vivo was validated by using a diabetic db/db mouse model. CONCLUSION These findings demonstrated that C3G could alleviate IR in vitro and in vivo to increase insulin sensitivity, which may offer a new insight for regulating glucose metabolism during T2DM by using the natural dietary bioactive components. C3G promotes the phosphorylation of IRS-2 proteins by suppressing the expression of PTP1B, and then enhances the sensitivity of hepatocyte to insulin.
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Affiliation(s)
- Xiang Ye
- Department of Endocrinology and Metabolism, The Second Affiliated Hospital of Zhejiang University School of Medicine, 310058, Hangzhou, China
- College of Biosystems Engineering and Food Science, Zhejiang University, 310058, Hangzhou, China
| | - Wen Chen
- College of Biosystems Engineering and Food Science, Zhejiang University, 310058, Hangzhou, China
| | - Xu-Fan Huang
- Department of Endocrinology and Metabolism, The Second Affiliated Hospital of Zhejiang University School of Medicine, 310058, Hangzhou, China
| | - Fu-Jie Yan
- College of Biosystems Engineering and Food Science, Zhejiang University, 310058, Hangzhou, China
| | - Shui-Guang Deng
- Advanced Computing and System Laboratory, College of Computer Science and Technology, Zhejiang University, 310058, Hangzhou, China
- Innovation Centre for Information, Binjiang Institute of Zhejiang University, 310058, Hangzhou, China
| | - Xiao-Dong Zheng
- College of Biosystems Engineering and Food Science, Zhejiang University, 310058, Hangzhou, China.
| | - Peng-Fei Shan
- Department of Endocrinology and Metabolism, The Second Affiliated Hospital of Zhejiang University School of Medicine, 310058, Hangzhou, China.
- Innovation Centre for Information, Binjiang Institute of Zhejiang University, 310058, Hangzhou, China.
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Bjune MS, Lawrence-Archer L, Laupsa-Borge J, Sommersten CH, McCann A, Glastad RC, Johnston IG, Kern M, Blüher M, Mellgren G, Dankel SN. Metabolic role of the hepatic valine/3-hydroxyisobutyrate (3-HIB) pathway in fatty liver disease. EBioMedicine 2023; 91:104569. [PMID: 37084480 PMCID: PMC10148099 DOI: 10.1016/j.ebiom.2023.104569] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2022] [Revised: 03/30/2023] [Accepted: 03/30/2023] [Indexed: 04/23/2023] Open
Abstract
BACKGROUND The valine (branched-chain amino acid) metabolite 3-hydroxyisobutyrate (3-HIB), produced by 3-Hydroxyisobutyryl-CoA Hydrolase (HIBCH), is associated with insulin resistance and type 2 diabetes, but implicated tissues and cellular mechanisms are poorly understood. We hypothesized that HIBCH and 3-HIB regulate hepatic lipid accumulation. METHODS HIBCH mRNA in human liver biopsies ("Liver cohort") and plasma 3-HIB ("CARBFUNC" cohort) were correlated with fatty liver and metabolic markers. Human Huh7 hepatocytes were supplemented with fatty acids (FAs) to induce lipid accumulation. Following HIBCH overexpression, siRNA knockdown, inhibition of PDK4 (a marker of FA β-oxidation) or 3-HIB supplementation, we performed RNA-seq, Western blotting, targeted metabolite analyses and functional assays. FINDINGS We identify a regulatory feedback loop between the valine/3-HIB pathway and PDK4 that shapes hepatic FA metabolism and metabolic health and responds to 3-HIB treatment of hepatocytes. HIBCH overexpression increased 3-HIB release and FA uptake, while knockdown increased cellular respiration and decreased reactive oxygen species (ROS) associated with metabolic shifts via PDK4 upregulation. Treatment with PDK4 inhibitor lowered 3-HIB release and increased FA uptake, while increasing HIBCH mRNA. Implicating this regulatory loop in fatty liver, human cohorts show positive correlations of liver fat with hepatic HIBCH and PDK4 expression (Liver cohort) and plasma 3-HIB (CARBFUNC cohort). Hepatocyte 3-HIB supplementation lowered HIBCH expression and FA uptake and increased cellular respiration and ROS. INTERPRETATION These data implicate the hepatic valine/3-HIB pathway in mechanisms of fatty liver, reflected in increased plasma 3-HIB concentrations, and present possible targets for therapeutic intervention. FUNDING Funding was provided by the Research Council of Norway (263124/F20), the University of Bergen, the Western Norway Health Authorities, Novo Nordisk Scandinavia AS, the Trond Mohn Foundation and the Norwegian Diabetes Association.
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Affiliation(s)
- Mona Synnøve Bjune
- Mohn Nutrition Research Laboratory, Department of Clinical Science, University of Bergen, Bergen, Norway; Hormone Laboratory, Haukeland University Hospital, Bergen, Norway
| | - Laurence Lawrence-Archer
- Mohn Nutrition Research Laboratory, Department of Clinical Science, University of Bergen, Bergen, Norway; Hormone Laboratory, Haukeland University Hospital, Bergen, Norway
| | - Johnny Laupsa-Borge
- Mohn Nutrition Research Laboratory, Department of Clinical Science, University of Bergen, Bergen, Norway; Bevital AS, Bergen, Norway
| | - Cathrine Horn Sommersten
- Mohn Nutrition Research Laboratory, Department of Clinical Science, University of Bergen, Bergen, Norway; Mohn Nutrition Research Laboratory, Department of Clinical Medicine, University of Bergen, Bergen, Norway
| | | | | | - Iain George Johnston
- Department of Mathematics, University of Bergen, Bergen, Norway; Computational Biology Unit, University of Bergen, Bergen, Norway
| | - Matthias Kern
- Helmholtz Institute for Metabolic, Obesity and Vascular Research (HI-MAG) of the Helmholtz Zentrum München at the University of Leipzig and University Hospital Leipzig, Leipzig, Germany; Medical Department III-Endocrinology, Nephrology, Rheumatology, University of Leipzig Medical Center, Leipzig, Germany
| | - Matthias Blüher
- Helmholtz Institute for Metabolic, Obesity and Vascular Research (HI-MAG) of the Helmholtz Zentrum München at the University of Leipzig and University Hospital Leipzig, Leipzig, Germany; Medical Department III-Endocrinology, Nephrology, Rheumatology, University of Leipzig Medical Center, Leipzig, Germany
| | - Gunnar Mellgren
- Mohn Nutrition Research Laboratory, Department of Clinical Science, University of Bergen, Bergen, Norway; Hormone Laboratory, Haukeland University Hospital, Bergen, Norway
| | - Simon N Dankel
- Mohn Nutrition Research Laboratory, Department of Clinical Science, University of Bergen, Bergen, Norway; Hormone Laboratory, Haukeland University Hospital, Bergen, Norway.
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Han S, Zhang XL, Jiang X, Li X, Ding J, Zuo LJ, Duan SS, Chen R, Sun BB, Hu XY, Gao YN, Zhang XL. Long Non-Coding RNA and mRNA Expression Analysis in Liver of Mice With Clonorchis sinensis Infection. Front Cell Infect Microbiol 2022; 11:754224. [PMID: 35127549 PMCID: PMC8807509 DOI: 10.3389/fcimb.2021.754224] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 12/07/2021] [Indexed: 12/13/2022] Open
Abstract
Clonorchiasis is recognized as an important zoonotic parasitic disease worldwide. However, the roles of host long non-coding RNAs (lncRNAs) and messenger RNAs (mRNAs) in the response to Clonorchis sinensis (C. sinensis) infection remain unknown. Here we compared the expression of lncRNAs and mRNAs in the liver tissue of mice infected with C. sinensis, in order to further understand the molecular mechanisms of clonorchiasis. A total of 388 lncRNAs and 1,172 mRNAs were found to be differentially expressed with absolute value of fold change (FC) ≥ 2.0 and p < 0.05 by microarray. Compared with controls, Gm6135 and 4930581F22Rik were the most over- and under-expressed lncRNAs; flavin-containing monooxygenase 3 (Fmo3) and deleted in malignant brain tumors 1 (Dmbt1) were the most over- and under-expressed mRNAs. Moreover, functional annotation showed that the significantly different mRNAs were related with “FOXO signaling pathway”, “Wnt signaling pathway”, and “AMPK signaling pathway”. Remarkably, lncRNA Gm8801 were significantly correlated with mRNA glycerol-3-phosphate acyltransferase mitochondrial (Gpam), insulin receptor substrate 2 (Irs2), and tumor necrosis factor receptor superfamily member 19 (Tnfrsf19) in ceRNA networks. These results showed that the expression profiles of lncRNAs and mRNAs in the liver changed after C. sinensis infection. Our results provided valuable insights into the lncRNAs and mRNAs involved in clonorchiasis pathogenesis, which may be useful for future control strategies.
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Affiliation(s)
- Su Han
- Department of Parasitology, Harbin Medical University, Harbin, China
| | - Xue-Li Zhang
- Department of Parasitology, Harbin Medical University, Harbin, China
| | - Xu Jiang
- Department of Parasitology, Harbin Medical University, Harbin, China
| | - Xiang Li
- Department of Parasitology, Harbin Medical University, Harbin, China
| | - Jian Ding
- Department of Parasitology, Harbin Medical University, Harbin, China
| | - Li-Jiao Zuo
- Department of Parasitology, Harbin Medical University, Harbin, China
| | - Shan-Shan Duan
- Department of Parasitology, Harbin Medical University, Harbin, China
| | - Rui Chen
- Department of Orthopaedic Surgery, The Fourth Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Bei-Bei Sun
- Clinical Laboratory, Zhuhai Maternal and Child Health Hospital, Zhuhai, China
| | - Xin-Yi Hu
- Department of Stomatology, Laixi People’s Hospital, Qingdao, China
| | - Yan-Nan Gao
- Department of Parasitology, Harbin Medical University, Harbin, China
| | - Xiao-Li Zhang
- Department of Parasitology, Harbin Medical University, Harbin, China
- *Correspondence: Xiao-Li Zhang,
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Hayashi T, Kubota T, Mariko I, Takamoto I, Aihara M, Sakurai Y, Wada N, Miki T, Yamauchi T, Kubota N, Kadowaki T. Lack of Brain Insulin Receptor Substrate-1 Causes Growth Retardation, With Decreased Expression of Growth Hormone-Releasing Hormone in the Hypothalamus. Diabetes 2021; 70:1640-1653. [PMID: 33980693 DOI: 10.2337/db20-0482] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Accepted: 05/07/2021] [Indexed: 11/13/2022]
Abstract
Insulin receptor substrate-1 (Irs1) is one of the major substrates for insulin receptor and insulin-like growth factor-1 (IGF-1) receptor tyrosine kinases. Systemic Irs1-deficient mice show growth retardation, with resistance to insulin and IGF-1, although the underlying mechanisms remain poorly understood. For this study, we generated mice with brain-specific deletion of Irs1 (NIrs1KO mice). The NIrs1KO mice exhibited lower body weights, shorter bodies and bone lengths, and decreased bone density. Moreover, the NIrs1KO mice exhibited increased insulin sensitivity and glucose utilization in the skeletal muscle. Although the ability of the pituitary to secrete growth hormone (GH) remained intact, the amount of hypothalamic growth hormone-releasing hormone (GHRH) was significantly decreased and, accordingly, the pituitary GH mRNA expression levels were impaired in these mice. Plasma GH and IGF-1 levels were also lower in the NIrs1KO mice. The expression levels of GHRH protein in the median eminence, where Irs1 antibody staining is observed, were markedly decreased in the NIrs1KO mice. In vitro, neurite elongation after IGF-1 stimulation was significantly impaired by Irs1 downregulation in the cultured N-38 hypothalamic neurons. In conclusion, brain Irs1 plays important roles in the regulation of neurite outgrowth of GHRH neurons, somatic growth, and glucose homeostasis.
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Affiliation(s)
- Takanori Hayashi
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
- Department of Clinical Nutrition, National Institute of Health and Nutrition, National Institutes of Biomedical Innovation, Health and Nutrition (NIBIOHN), Tokyo, Japan
| | - Tetsuya Kubota
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
- Department of Clinical Nutrition, National Institute of Health and Nutrition, National Institutes of Biomedical Innovation, Health and Nutrition (NIBIOHN), Tokyo, Japan
- Laboratory for Intestinal Ecosystem, RIKEN Center for Integrative Medical Sciences, Kanagawa, Japan
- Division of Diabetes and Metabolism, The Institute of Medical Science, Asahi Life Foundation, Tokyo, Japan
- Division of Cardiovascular Medicine, Toho University, Ohashi Hospital, Tokyo, Japan
| | - Inoue Mariko
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
- Department of Clinical Nutrition, National Institute of Health and Nutrition, National Institutes of Biomedical Innovation, Health and Nutrition (NIBIOHN), Tokyo, Japan
| | - Iseki Takamoto
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Masakazu Aihara
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Yoshitaka Sakurai
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Nobuhiro Wada
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
- Department of Clinical Nutrition, National Institute of Health and Nutrition, National Institutes of Biomedical Innovation, Health and Nutrition (NIBIOHN), Tokyo, Japan
| | - Takashi Miki
- Department of Medical Physiology, Chiba University, Graduate School of Medicine, Chiba, Japan
| | - Toshimasa Yamauchi
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Naoto Kubota
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
- Department of Clinical Nutrition, National Institute of Health and Nutrition, National Institutes of Biomedical Innovation, Health and Nutrition (NIBIOHN), Tokyo, Japan
- Department of Clinical Nutrition Therapy, The University of Tokyo, Tokyo, Japan
| | - Takashi Kadowaki
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
- Department of Prevention of Diabetes and Lifestyle-Related Diseases, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
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Saeed NM, Mansour AM, Allam S. Lycopene induces insulin signaling and alleviates fibrosis in experimental model of non-alcoholic fatty liver disease in rats. PHARMANUTRITION 2020. [DOI: 10.1016/j.phanu.2020.100225] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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7
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Maffei A, Lembo G, Carnevale D. PI3Kinases in Diabetes Mellitus and Its Related Complications. Int J Mol Sci 2018; 19:ijms19124098. [PMID: 30567315 PMCID: PMC6321267 DOI: 10.3390/ijms19124098] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Revised: 12/13/2018] [Accepted: 12/15/2018] [Indexed: 02/07/2023] Open
Abstract
Recent studies have shown that phosphoinositide 3-kinases (PI3Ks) have become the target of many pharmacological treatments, both in clinical trials and in clinical practice. PI3Ks play an important role in glucose regulation, and this suggests their possible involvement in the onset of diabetes mellitus. In this review, we gather our knowledge regarding the effects of PI3K isoforms on glucose regulation in several organs and on the most clinically-relevant complications of diabetes mellitus, such as cardiomyopathy, vasculopathy, nephropathy, and neurological disease. For instance, PI3K α has been proven to be protective against diabetes-induced heart failure, while PI3K γ inhibition is protective against the disease onset. In vessels, PI3K γ can generate oxidative stress, while PI3K β inhibition is anti-thrombotic. Finally, we describe the role of PI3Ks in Alzheimer’s disease and ADHD, discussing the relevance for diabetic patients. Given the high prevalence of diabetes mellitus, the multiple effects here described should be taken into account for the development and validation of drugs acting on PI3Ks.
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Affiliation(s)
- Angelo Maffei
- Department of Angiocardioneurology and Translational Medicine, IRCCS Neuromed, 86077 Pozzilli, Italy.
| | - Giuseppe Lembo
- Department of Angiocardioneurology and Translational Medicine, IRCCS Neuromed, 86077 Pozzilli, Italy.
- Department of Molecular Medicine, "Sapienza" University of Rome, 00161 Rome, Italy.
| | - Daniela Carnevale
- Department of Angiocardioneurology and Translational Medicine, IRCCS Neuromed, 86077 Pozzilli, Italy.
- Department of Molecular Medicine, "Sapienza" University of Rome, 00161 Rome, Italy.
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Yokota SI, Nakamura K, Ando M, Haraguchi A, Omori K, Shibata S. A low-protein diet eliminates the circadian rhythm of serum insulin and hepatic lipid metabolism in mice. J Nutr Biochem 2018; 63:177-185. [PMID: 30412906 DOI: 10.1016/j.jnutbio.2018.10.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Revised: 09/14/2018] [Accepted: 10/04/2018] [Indexed: 12/27/2022]
Abstract
Insulin is a key molecule that synchronizes peripheral clocks, such as that in the liver. Although we previously reported that mice fed a low-protein diet showed altered expression of lipid-related genes in the liver and induction of hepatic steatosis, it is unknown whether a low-protein diet impairs insulin secretion and modifies the hepatic circadian rhythm. Therefore, we investigated the effects of the intake of a low-protein diet on the circadian rhythm of insulin secretion and hepatic lipid metabolism in mice. Under 12-h light/12-h dark cycle, mice fed a low-protein diet for 7 days displayed enhanced food intake at the end of the light phase, although central and peripheral PER2 expression rhythm was maintained. Serum insulin levels in mice fed a low-protein diet remained low during the day, and the insulin secretion in OGTT was also markedly lower than in normal mice. In mice fed low-protein diet, hepatic TG accumulation was observed during the nighttime, with relatively high levels of ACC1 mRNA and total ACC proteins. Although there were no differences in the activity rhythm of hepatic mTOR between mice fed a normal or low-protein diet, hepatic IRS-2 expression in mice fed a low-protein diet remained low during the day, with no increase at the beginning of the light period. These results suggested that the low-protein diet eliminated the circadian rhythm of serum insulin and hepatic lipid metabolism in mice, providing insights into our understanding of the mechanisms of hepatic disorders of lipid metabolism.
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Affiliation(s)
- Shin-Ichi Yokota
- Department of Physiology and Pharmacology, School of Advanced Science and Engineering, Waseda University, Tokyo, Japan; Amami Laboratory of Injurious Animals, Institute of Medical Science, The University of Tokyo, Japan
| | - Kaai Nakamura
- Department of Physiology and Pharmacology, School of Advanced Science and Engineering, Waseda University, Tokyo, Japan
| | - Midori Ando
- Department of Physiology and Pharmacology, School of Advanced Science and Engineering, Waseda University, Tokyo, Japan
| | - Atsushi Haraguchi
- Department of Physiology and Pharmacology, School of Advanced Science and Engineering, Waseda University, Tokyo, Japan
| | - Kanako Omori
- Department of Physiology and Pharmacology, School of Advanced Science and Engineering, Waseda University, Tokyo, Japan
| | - Shigenobu Shibata
- Department of Physiology and Pharmacology, School of Advanced Science and Engineering, Waseda University, Tokyo, Japan.
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Torii S, Kubota C, Saito N, Kawano A, Hou N, Kobayashi M, Torii R, Hosaka M, Kitamura T, Takeuchi T, Gomi H. The pseudophosphatase phogrin enables glucose-stimulated insulin signaling in pancreatic β cells. J Biol Chem 2018; 293:5920-5933. [PMID: 29483197 DOI: 10.1074/jbc.ra117.000301] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Revised: 02/14/2018] [Indexed: 12/18/2022] Open
Abstract
Autocrine insulin signaling is critical for pancreatic β-cell growth and activity and is at least partially controlled by protein-tyrosine phosphatases (PTPs) that act on insulin receptors (IRs). The receptor-type PTP phogrin primarily localizes on insulin secretory granules in pancreatic β cells. We recently reported that phogrin knockdown decreases the protein levels of insulin receptor substrate 2 (IRS2), whereas high-glucose stimulation promotes formation of a phogrin-IR complex that stabilizes IRS2. However, the underlying molecular mechanisms by which phogrin affects IRS2 levels are unclear. Here, we found that relative to wildtype mice, IRS2 levels in phogrin-knockout mice islets decreased by 44%. When phogrin was silenced by shRNA in pancreatic β-cell lines, glucose-induced insulin signaling led to proteasomal degradation of IRS2 via a negative feedback mechanism. Phogrin overexpression in a murine hepatocyte cell line consistently prevented chronic insulin treatment-induced IRS2 degradation. In vitro, phogrin directly bound the IR without the assistance of other proteins and protected recombinant PTP1B from oxidation to potentiate its activity toward the IR. Furthermore, phogrin expression suppressed insulin-induced local generation of hydrogen peroxide and subsequent PTP1B oxidation, which allowed progression of IR dephosphorylation. Together, these results suggest that a transient interaction of phogrin with the IR enables glucose-stimulated autocrine insulin signaling through the regulation of PTP1B activity, which is essential for suppressing feedback-mediated IRS2 degradation in pancreatic β cells.
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Affiliation(s)
| | | | | | | | - Ni Hou
- From the Biosignal Research Center and
| | - Masaki Kobayashi
- Metabolic Signal Research Center, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8512, Japan
| | | | - Masahiro Hosaka
- the Department of Biotechnology, Akita Prefectural University, Akita 010-0195, Japan
| | - Tadahiro Kitamura
- Metabolic Signal Research Center, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8512, Japan
| | - Toshiyuki Takeuchi
- From the Biosignal Research Center and.,the Administration Office, Gunma University, Maebashi, Gunma 371-8512, Japan, and
| | - Hiroshi Gomi
- the Department of Veterinary Anatomy, College of Bioresource Sciences, Nihon University, Fujisawa, Kanagawa 252-8510, Japan
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Abstract
Enlarged fat cells in obese adipose tissue diminish capacity to store fat and are resistant to the anti-lipolytic effect of insulin. Insulin resistance (IR)-associated S-nitrosylation of insulin-signaling proteins increases in obesity. In accordance with the inhibition of insulin-mediated anti-lipolytic action, plasma free fatty acid (FFA) levels increase. Additionally, endoplasmic reticulum stress stimuli induce lipolysis by activating cyclic adenosine monophosphate/Protein kinase A (cAMP/PKA) and extracellular signal-regulated kinase ½ (ERK1/2) signaling in adipocytes. Failure of packaging of excess lipid into lipid droplets causes chronic elevation of circulating fatty acids, which can reach to toxic levels within non-adipose tissues. Deleterious effects of lipid accumulation in non-adipose tissues are known as lipotoxicity. In fact, triglycerides may also serve a storage function for long-chain non-esterified fatty acids and their products such as ceramides and diacylglycerols (DAGs). Thus, excess DAG, ceramide and saturated fatty acids in obesity can induce chronic inflammation and have harmful effect on multiple organs and systems. In this context, chronic adipose tissue inflammation, mitochondrial dysfunction and IR have been discussed within the scope of lipotoxicity.
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Chen H, Bai J, Dong F, Fang H, Zhang Y, Meng W, Liu B, Luo Y, Liu M, Bai Y, Abdul-Ghani MA, Li R, Wu J, Zeng R, Zhou Z, Dong LQ, Liu F. Hepatic DsbA-L protects mice from diet-induced hepatosteatosis and insulin resistance. FASEB J 2017; 31:2314-2326. [PMID: 28232481 DOI: 10.1096/fj.201600985r] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Accepted: 01/30/2017] [Indexed: 01/28/2023]
Abstract
Hepatic insulin resistance and hepatosteatosis in diet-induced obesity are associated with various metabolic diseases, yet the underlying mechanisms remain to be fully elucidated. Here we show that the expression levels of the disulfide-bond A oxidoreductase-like protein (DsbA-L) are significantly reduced in the liver of obese mice and humans. Liver-specific knockout or adenovirus-mediated overexpression of DsbA-L exacerbates or alleviates, respectively, high-fat diet-induced mitochondrial dysfunction, hepatosteatosis, and insulin resistance in mice. Mechanistically, we found that DsbA-L is localized in mitochondria and that its deficiency is associated with impairment of maximum respiratory capacity, elevated cellular oxidative stress, and increased JNK activity. Our results identify DsbA-L as a critical regulator of mitochondrial function, and its down-regulation in the liver may contribute to obesity-induced hepatosteatosis and whole body insulin resistance.-Chen, H., Bai, J., Dong, F., Fang, H., Zhang, Y., Meng, W., Liu, B., Luo, Y., Liu, M., Bai, Y., Abdul-Ghani, M. A., Li, R., Wu, J., Zeng, R., Zhou, Z., Dong, L. Q., Liu, F. Hepatic DsbA-L protects mice from diet-induced hepatosteatosis and insulin resistance.
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Affiliation(s)
- Hongzhi Chen
- Department of Metabolism and Endocrinology, Metabolic Syndrome Research Center, Key Laboratory of Diabetes Immunology, Ministry of Education, National Clinical Research Center for Metabolic Disease, Second Xiangya Hospital, Central South University, Changsha, China.,Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas, USA
| | - Juli Bai
- Department of Metabolism and Endocrinology, Metabolic Syndrome Research Center, Key Laboratory of Diabetes Immunology, Ministry of Education, National Clinical Research Center for Metabolic Disease, Second Xiangya Hospital, Central South University, Changsha, China.,Department of Pharmacology, University of Texas Health Science Center, San Antonio, Texas, USA
| | - Feng Dong
- Department of Medicine, University of Texas Health Science Center, San Antonio, Texas, USA
| | - Hezhi Fang
- Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio, Texas, USA
| | - Yun Zhang
- Department of Metabolism and Endocrinology, Metabolic Syndrome Research Center, Key Laboratory of Diabetes Immunology, Ministry of Education, National Clinical Research Center for Metabolic Disease, Second Xiangya Hospital, Central South University, Changsha, China
| | - Wen Meng
- Department of Metabolism and Endocrinology, Metabolic Syndrome Research Center, Key Laboratory of Diabetes Immunology, Ministry of Education, National Clinical Research Center for Metabolic Disease, Second Xiangya Hospital, Central South University, Changsha, China
| | - Bilian Liu
- Department of Metabolism and Endocrinology, Metabolic Syndrome Research Center, Key Laboratory of Diabetes Immunology, Ministry of Education, National Clinical Research Center for Metabolic Disease, Second Xiangya Hospital, Central South University, Changsha, China
| | - Yan Luo
- Department of Metabolism and Endocrinology, Metabolic Syndrome Research Center, Key Laboratory of Diabetes Immunology, Ministry of Education, National Clinical Research Center for Metabolic Disease, Second Xiangya Hospital, Central South University, Changsha, China
| | - Meilian Liu
- Department of Metabolism and Endocrinology, Metabolic Syndrome Research Center, Key Laboratory of Diabetes Immunology, Ministry of Education, National Clinical Research Center for Metabolic Disease, Second Xiangya Hospital, Central South University, Changsha, China.,Department of Biochemistry and Molecular Biology, University of New Mexico Health Science Center, Albuquerque, New Mexico, USA
| | - Yidong Bai
- Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio, Texas, USA
| | - Muhammad A Abdul-Ghani
- Department of Medicine, University of Texas Health Science Center, San Antonio, Texas, USA
| | - Rongxia Li
- Key Laboratory of Systems Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Jiarui Wu
- Key Laboratory of Systems Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Rong Zeng
- Key Laboratory of Systems Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Zhiguang Zhou
- Department of Metabolism and Endocrinology, Metabolic Syndrome Research Center, Key Laboratory of Diabetes Immunology, Ministry of Education, National Clinical Research Center for Metabolic Disease, Second Xiangya Hospital, Central South University, Changsha, China
| | - Lily Q Dong
- Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio, Texas, USA
| | - Feng Liu
- Department of Metabolism and Endocrinology, Metabolic Syndrome Research Center, Key Laboratory of Diabetes Immunology, Ministry of Education, National Clinical Research Center for Metabolic Disease, Second Xiangya Hospital, Central South University, Changsha, China; .,Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas, USA.,Department of Pharmacology, University of Texas Health Science Center, San Antonio, Texas, USA
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12
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Vogt JA, Domzig C, Wabitsch M, Denzer C. Prehepatic secretion and disposal of insulin in obese adolescents as estimated by three-hour, eight-sample oral glucose tolerance tests. Am J Physiol Endocrinol Metab 2016; 311:E82-94. [PMID: 27143555 DOI: 10.1152/ajpendo.00455.2014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Accepted: 04/25/2016] [Indexed: 01/10/2023]
Abstract
The body compensates for early-stage insulin resistance by increasing insulin secretion. A reliable and easy-to-use mathematical assessment of insulin secretion and disposal could be a valuable tool for identifying patients at risk for the development of type 2 diabetes. Because the pathophysiology of insulin resistance is incompletely understood, assessing insulin metabolism with minimal assumptions regarding its metabolic regulation is a major challenge. To assess insulin secretion and indexes of insulin disposal, our marginalized and regularized absorption approach (MRA) was applied to a sparse sampling oral glucose tolerance test (OGTT) protocol measuring the insulin and C-peptide concentrations. Identifiability and potential bias of metabolic parameters were estimated from published data with dense sampling. The MRA was applied to OGTT data from 135 obese adolescents to demonstrate its clinical applicability. Individual prehepatic basal and dynamic insulin secretion and clearance levels were determined with a precision and accuracy greater than 10% of the nominal value. The intersubject variability in these parameters was approximately four times higher than the intrasubject variability, and there was a strong negative correlation between prehepatic secretion and plasma clearance of insulin. MRA-based analysis provides reliable estimates of insulin secretion and clearance, thereby enabling detailed glucose homeostasis characterization based on restricted datasets that are obtainable during routine patient care.
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Affiliation(s)
- Josef A Vogt
- Institut für Anästhesiologische Pathophysiologie und Verfahrensentwicklung, Universitätsklinikum Ulm, Ulm, Germany; and
| | - Christian Domzig
- Division of Pediatric Endocrinology and Diabetes, Interdisciplinary Obesity Unit, Department of Pediatrics and Adolescent Medicine, University Medical Center Ulm, Ulm, Germany
| | - Martin Wabitsch
- Division of Pediatric Endocrinology and Diabetes, Interdisciplinary Obesity Unit, Department of Pediatrics and Adolescent Medicine, University Medical Center Ulm, Ulm, Germany
| | - Christian Denzer
- Division of Pediatric Endocrinology and Diabetes, Interdisciplinary Obesity Unit, Department of Pediatrics and Adolescent Medicine, University Medical Center Ulm, Ulm, Germany
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13
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Al-Lahham R, Deford JH, Papaconstantinou J. Mitochondrial-generated ROS down regulates insulin signaling via activation of the p38MAPK stress response pathway. Mol Cell Endocrinol 2016; 419:1-11. [PMID: 26454089 DOI: 10.1016/j.mce.2015.09.013] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Revised: 08/18/2015] [Accepted: 09/14/2015] [Indexed: 01/09/2023]
Abstract
Impairment of insulin signaling and hepatic insulin resistance has been attributed to ROS-mediated activation of p38MAPK stress response signaling. Our research focused on whether (a) ROS generated by mitochondrial electron transport chain complex I (ETC-CI) dysfunction, via the use of Rotenone, inactivates insulin signaling; and (b) the p38MAPK pathway is involved in the ROS-induced impairment of insulin signaling. Our results show that in primary mouse hepatocytes the CI inhibitor, Rotenone, (a) induces IRS-1 Ser(307) phosphorylation that is blocked by the anti-oxidant NAC or by the p38MAPK inhibitors, SB203580 and SB202190; (b) inhibits insulin-stimulated AKT-Ser(473) and GSK3β-Ser(9) phosphorylations, in a manner that is not responsive to reversal by the anti-oxidant NAC or by the p38MAPK inhibitors, SB203580 and SB202190. We conclude that rotenone-induced insulin resistance involves a p38MAPK-dependent mechanism for the inhibition of the proximal end of insulin signaling (IRS1), and a p38MAPK-independent mechanism for the inhibition of the distal end (AKT and GSK3β). Our study suggests that ROS generated by inhibition of ETC CI, promotes hepatic insulin resistance partly via activation of the p38MAPK stress-response pathway.
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Affiliation(s)
- Rabab Al-Lahham
- Department of Biochemistry and Molecular Biology, The University of Texas Medical Branch, Galveston, TX, 77555, USA
| | - James H Deford
- Department of Biochemistry and Molecular Biology, The University of Texas Medical Branch, Galveston, TX, 77555, USA
| | - John Papaconstantinou
- Department of Biochemistry and Molecular Biology, The University of Texas Medical Branch, Galveston, TX, 77555, USA.
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14
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Fu Q, Olson P, Rasmussen D, Keith B, Williamson M, Zhang KK, Xie L. A short-term transition from a high-fat diet to a normal-fat diet before pregnancy exacerbates female mouse offspring obesity. Int J Obes (Lond) 2015; 40:564-72. [PMID: 26607040 DOI: 10.1038/ijo.2015.236] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Revised: 10/19/2015] [Accepted: 11/01/2015] [Indexed: 12/17/2022]
Abstract
BACKGROUND/OBJECTIVES Recent findings have highlighted the detrimental influence of maternal overnutrition and obesity on fetal development and early life development. However, there are no evidence-based guidelines regarding the optimal strategy for dietary intervention before pregnancy. SUBJECTS/METHODS We used a murine model to study whether switching from a high-fat (HF) diet to a normal-fat (NF) diet (H1N group) 1 week before pregnancy could lead to in utero reprogramming of female offspring obesity; comparator groups were offspring given a consistent maternal HF group or NF group until weaning. After weaning, all female offspring were given the HF diet for either 9 or 12 weeks before being killed humanely. RESULTS H1N treatment did not result in maternal weight loss before pregnancy. NF offsprings were neither obese nor glucose intolerant during the entire experimental period. H1N offsprings were most obese after the 12-week postweaning HF diet and displayed glucose intolerance earlier than HF offsprings. Our mechanistic study showed reduced adipocyte insulin receptor substrate 1 (IRS1) and hepatic IRS2 expression and increased adipocyte p-Ser(636/639) and p-Ser(612) of H1N or HF offspring compared with that in the NF offspring. Among all groups, the H1N offspring had lowest level of IRS1 and the highest levels of p-Ser(636/639) and p-Ser(612) in gonadal adipocyte. In addition, the H1N offspring further reduced the expression of Glut4 and Glut2, vs those of the HF offspring, which was lower compared with the NF offspring. There were also enhanced expression of genes inhibiting glycogenesis and decreased hepatic glycogen in H1N vs HF or NF offspring. Furthermore, we showed extremely higher expression of lipogenesis and adipogenesis genes in gonadal adipocytes of H1N offspring compared with all other groups. CONCLUSIONS Our results suggest that a transition from an HF diet to an NF diet shortly before pregnancy, without resulting in maternal weight loss, is not necessarily beneficial and may have deleterious effects on offspring.
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Affiliation(s)
- Q Fu
- Department of Basic Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND, USA.,Department of Oncology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.,Department of Nutrition and Food Science, Texas A&M University, College Station, TX, USA
| | - P Olson
- Department of Basic Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND, USA
| | - D Rasmussen
- Department of Basic Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND, USA
| | - B Keith
- Department of Basic Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND, USA
| | - M Williamson
- Department of Basic Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND, USA
| | - K K Zhang
- Department of Pathology, University of North Dakota, Grand Forks, ND, USA
| | - L Xie
- Department of Basic Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND, USA.,Department of Nutrition and Food Science, Texas A&M University, College Station, TX, USA
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15
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Duodenal-jejunal exclusion improves insulin resistance in type 2 diabetic rats by upregulating the hepatic insulin signaling pathway. Nutrition 2015; 31:733-9. [DOI: 10.1016/j.nut.2014.10.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2014] [Revised: 09/14/2014] [Accepted: 10/22/2014] [Indexed: 12/19/2022]
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16
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Silencing of ANGPTL 3 (angiopoietin-like protein 3) in human hepatocytes results in decreased expression of gluconeogenic genes and reduced triacylglycerol-rich VLDL secretion upon insulin stimulation. Biosci Rep 2014; 34:e00160. [PMID: 25495645 PMCID: PMC4266921 DOI: 10.1042/bsr20140115] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Homozygosity of loss-of-function mutations in ANGPTL3 (angiopoietin-like protein 3)-gene results in FHBL2 (familial combined hypolipidaemia, OMIM #605019) characterized by the reduction of all major plasma lipoprotein classes, which includes VLDL (very-low-density lipoprotein), LDL (low-density lipoprotein), HDL (high-density lipoprotein) and low circulating NEFAs (non-esterified fatty acids), glucose and insulin levels. Thus complete lack of ANGPTL3 in humans not only affects lipid metabolism, but also affects whole-body insulin and glucose balance. We used wild-type and ANGPTL3-silenced IHHs (human immortalized hepatocytes) to investigate the effect of ANGPTL3 silencing on hepatocyte-specific VLDL secretion and glucose uptake. We demonstrate that both insulin and PPARγ (peroxisome-proliferator-activated receptor γ) agonist rosiglitazone down-regulate the secretion of ANGPTL3 and TAG (triacylglycerol)-enriched VLDL1-type particles in a dose-dependent manner. Silencing of ANGPTL3 improved glucose uptake in hepatocytes by 20–50% and influenced down-regulation of gluconeogenic genes, suggesting that silencing of ANGPTL3 improves insulin sensitivity. We further show that ANGPTL3-silenced cells display a more pronounced shift from the secretion of TAG-enriched VLDL1-type particles to secretion of lipid poor VLDL2-type particles during insulin stimulation. These data suggest liver-specific mechanisms involved in the reported insulin-sensitive phenotype of ANGPTL3-deficient humans, featuring lower plasma insulin and glucose levels. We show that silencing of ANGPTL3 in human hepatocytes in addition to reducing secretion of TAG-enriched VLDL upon insulin stimulation enhances glucose uptake and improves insulin response. Thus, our data provide insight into the lower insulin and glucose levels observed in humans with ANGPTL3 loss-of-function mutation.
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17
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Zhang Q, Tan Y, Zhang N, Yao F. Polydatin supplementation ameliorates diet-induced development of insulin resistance and hepatic steatosis in rats. Mol Med Rep 2014; 11:603-10. [PMID: 25333896 DOI: 10.3892/mmr.2014.2708] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Accepted: 09/04/2014] [Indexed: 11/05/2022] Open
Abstract
The pathophysiology of non-alcoholic fatty liver disease remains to be elucidated, and the currently available treatments are not entirely effective. Polydatin, a stilbenoid compound derived from the rhizome of Polygonum cuspidatum, has previously been demonstrated to possess hepatoprotective effects. The present study aimed to determine the effects of polydatin supplementation on hepatic fat accumulation and injury in rats fed a high-fat diet. In addition, the mechanisms underlying the protective effects of polydatin were examined. Male Sprague Dawley rats were randomly divided into four groups and received one of four treatment regimes for 12 weeks: Control diet, control diet supplemented with polydatin, high-fat diet, or high-fat diet supplemented with polydatin. Polydatin was supplemented in the drinking water at a concentration of 0.3% (wt/vol). The results of the present study showed that long-term high-fat feeding resulted in fatty liver in rats, which was manifested by excessive hepatic neutral fat accumulation and elevated plasma alanine aminotransferase and aspartate aminotransferase levels. Polydatin supplementation alleviated the hepatic pathological changes, and attenuated the insulin resistance, as shown by an improved homeostasis model assessment of basal insulin resistance values and a glucose tolerance test. Polydatin supplementation also corrected abnormal leptin and adiponectin levels. Specifically, polydatin supplementation enhanced insulin sensitivity in the liver, as shown by improved insulin receptor substrate 2 expression levels and Akt phosphorylation in the rat liver, following high-fat diet feeding. The results of the present study suggest that polydatin protects rats against high-fat feeding-induced insulin resistance and hepatic steatosis. Polydatin may be an effective hepatoprotective agent and a potential candidate for the prevention of fatty liver disease and insulin resistance.
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Affiliation(s)
- Qi Zhang
- Department of Physiology, Basic Medical College, Shaanxi University of Chinese Medicine, Xianyang, Shaanxi 712046, P.R. China
| | - Yingying Tan
- Department of Physiology, Basic Medical College, Shaanxi University of Chinese Medicine, Xianyang, Shaanxi 712046, P.R. China
| | - Nan Zhang
- Department of Physiology, Basic Medical College, Shaanxi University of Chinese Medicine, Xianyang, Shaanxi 712046, P.R. China
| | - Fanrong Yao
- Department of Pharmacology and Toxicology, Brody School of Medicine, East Carolina University, Greenville, NC 27834, USA
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18
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F0 maternal BPA exposure induced glucose intolerance of F2 generation through DNA methylation change in Gck. Toxicol Lett 2014; 228:192-9. [DOI: 10.1016/j.toxlet.2014.04.012] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2014] [Revised: 04/14/2014] [Accepted: 04/17/2014] [Indexed: 01/03/2023]
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19
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Microbiota and nonalcoholic steatohepatitis. Semin Immunopathol 2013; 36:115-32. [PMID: 24337650 DOI: 10.1007/s00281-013-0404-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2013] [Accepted: 10/15/2013] [Indexed: 02/07/2023]
Abstract
The recent rise in obesity-related diseases, such as nonalcoholic fatty liver disease and its strong association with microbiota, has elicited interest in the underlying mechanisms of these pathologies. Experimental models have highlighted several mechanisms connecting microbiota to the development of liver dysfunction in nonalcoholic steatohepatitis (NASH) such as increased energy harvesting from the diet, small intestine bacterial overgrowth, modulation of the intestinal barrier by glucagon-like peptide-2 secretions, activation of innate immunity through the lipopolysaccharide-CD14 axis caused by obesity-induced leptin, periodontitis, and sterile inflammation. The manipulation of microbiota through probiotics, prebiotics, antibiotics, and periodontitis treatment yields encouraging results for the treatment of obesity, diabetes, and NASH, but data in humans is scarce.
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20
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Roncero I, Alvarez E, Acosta C, Sanz C, Barrio P, Hurtado-Carneiro V, Burks D, Blázquez E. Insulin-receptor substrate-2 (irs-2) is required for maintaining glucokinase and glucokinase regulatory protein expression in mouse liver. PLoS One 2013; 8:e58797. [PMID: 23560040 PMCID: PMC3613347 DOI: 10.1371/journal.pone.0058797] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Accepted: 02/06/2013] [Indexed: 12/02/2022] Open
Abstract
Insulin receptor substrate (IRS) proteins play important roles in hepatic nutrient homeostasis. Since glucokinase (GK) and glucokinase regulatory protein (GKRP) function as key glucose sensors, we have investigated the expression of GK and GKRP in liver of Irs-2 deficient mice and Irs2(−/−) mice where Irs2 was reintroduced specifically into pancreatic β-cells [RIP-Irs-2/IRS-2(−/−)]. We observed that liver GK activity was significantly lower (p<0.0001) in IRS-2(−/−) mice. However, in RIP-Irs-2/IRS-2(−/−) mice, GK activity was similar to the values observed in wild-type animals. GK activity in hypothalamus was not altered in IRS-2(−/−) mice. GK and GKRP mRNA levels in liver of IRS-2(−/−) were significantly lower, whereas in RIP-Irs-2/IRS-2(−/−) mice, both GK and GKRP mRNAs levels were comparable to wild-type animals. At the protein level, the liver content of GK was reduced in IRS-2(−/−) mice as compared with controls, although GKRP levels were similar between these experimental models. Both GK and GKRP levels were lower in RIP-Irs-2/IRS-2(−/−) mice. These results suggest that IRS-2 signalling is important for maintaining the activity of liver GK. Moreover, the differences between liver and brain GK may be explained by the fact that expression of hepatic, but not brain, GK is controlled by insulin. GK activity was restored by the β-cell compensation in the RIP-Irs-2/IRS-2 mice. Interestingly, GK and GKRP protein expression remained low in RIP-Irs-2/IRS-2(−/−) mice, perhaps reflecting different mRNA half-lives or alterations in the process of translation and post-translational regulation.
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Affiliation(s)
- Isabel Roncero
- The Center for Biomedical Research in Diabetes and Associated Metabolic Disorders (CIBERDEM), Madrid, Spain
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad Complutense de Madrid-Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid, Spain
| | - Elvira Alvarez
- The Center for Biomedical Research in Diabetes and Associated Metabolic Disorders (CIBERDEM), Madrid, Spain
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad Complutense de Madrid-Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid, Spain
| | - Carlos Acosta
- The Center for Biomedical Research in Diabetes and Associated Metabolic Disorders (CIBERDEM), Madrid, Spain
- Centro de Investigación Príncipe Felipe, Valencia, Spain
| | - Carmen Sanz
- The Center for Biomedical Research in Diabetes and Associated Metabolic Disorders (CIBERDEM), Madrid, Spain
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad Complutense de Madrid-Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid, Spain
- Departamento de Biología Celular, Facultad de Medicina, Universidad Complutense de Madrid, Madrid, Spain
| | - Pedro Barrio
- The Center for Biomedical Research in Diabetes and Associated Metabolic Disorders (CIBERDEM), Madrid, Spain
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad Complutense de Madrid-Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid, Spain
| | - Veronica Hurtado-Carneiro
- The Center for Biomedical Research in Diabetes and Associated Metabolic Disorders (CIBERDEM), Madrid, Spain
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad Complutense de Madrid-Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid, Spain
| | - Deborah Burks
- The Center for Biomedical Research in Diabetes and Associated Metabolic Disorders (CIBERDEM), Madrid, Spain
- Centro de Investigación Príncipe Felipe, Valencia, Spain
| | - Enrique Blázquez
- The Center for Biomedical Research in Diabetes and Associated Metabolic Disorders (CIBERDEM), Madrid, Spain
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad Complutense de Madrid-Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid, Spain
- * E-mail:
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21
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Tian J, Jiang Y. Insulin upregulates the expression of zinc finger and BTB domain-containing 7A in HepG2 cells. Mol Med Rep 2012; 6:1379-84. [PMID: 23027183 DOI: 10.3892/mmr.2012.1113] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Accepted: 09/10/2012] [Indexed: 11/06/2022] Open
Abstract
Zinc finger and BTB domain-containing 7A (Zbtb7A) is a proto-oncogene overexpressed in numerous cancers. In this study, we explored the mechanism of insulin-induced Zbtb7A expression. Real-time PCR and western blotting were used to detect Zbtb7A expression. Zbtb7A promoter activity was monitored by Luciferase reporter assay. It was shown that insulin elevates the mRNA and protein levels of the Zbtb7A gene in HepG2 cells. Using chemical inhibitors of insulin downstream pathways, we demonstrated that the insulin-induced Zbtb7A gene expression was completely blocked by LY294002, a PI3K/AKT inhibitor, and partially attenuated by the MAPK inhibitor PD98059. Transfection of HepG2 cells with a 1 kb Zbtb7A promoter-luciferase reporter construct revealed a dose-dependent activation of the Zbtb7A promoter by insulin, while mutation of the Sp1 binding site within the Zbtb7A promoter resulted in the failure of insulin-induced promoter activation, suggesting that insulin increases Zbtb7A expression through transcriptional regulation mediated by Sp1 in HepG2 cells.
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Affiliation(s)
- Jing Tian
- School of Life Sciences, Tsinghua University, Beijing 100084, P.R. China
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22
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Rosuvastatin may Modulate Insulin Signaling and Inhibit Atherogenesis Beyond its Plasma Cholesterol-Lowering Effect in Insulin-Resistant Mice. Cardiovasc Drugs Ther 2012; 26:375-82. [DOI: 10.1007/s10557-012-6406-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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23
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Talbot K, Wang HY, Kazi H, Han LY, Bakshi KP, Stucky A, Fuino RL, Kawaguchi KR, Samoyedny AJ, Wilson RS, Arvanitakis Z, Schneider JA, Wolf BA, Bennett DA, Trojanowski JQ, Arnold SE. Demonstrated brain insulin resistance in Alzheimer's disease patients is associated with IGF-1 resistance, IRS-1 dysregulation, and cognitive decline. J Clin Invest 2012; 122:1316-38. [PMID: 22476197 DOI: 10.1172/jci59903] [Citation(s) in RCA: 1287] [Impact Index Per Article: 107.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
While a potential causal factor in Alzheimer's disease (AD), brain insulin resistance has not been demonstrated directly in that disorder. We provide such a demonstration here by showing that the hippocampal formation (HF) and, to a lesser degree, the cerebellar cortex in AD cases without diabetes exhibit markedly reduced responses to insulin signaling in the IR→IRS-1→PI3K signaling pathway with greatly reduced responses to IGF-1 in the IGF-1R→IRS-2→PI3K signaling pathway. Reduced insulin responses were maximal at the level of IRS-1 and were consistently associated with basal elevations in IRS-1 phosphorylated at serine 616 (IRS-1 pS⁶¹⁶) and IRS-1 pS⁶³⁶/⁶³⁹. In the HF, these candidate biomarkers of brain insulin resistance increased commonly and progressively from normal cases to mild cognitively impaired cases to AD cases regardless of diabetes or APOE ε4 status. Levels of IRS-1 pS⁶¹⁶ and IRS-1 pS⁶³⁶/⁶³⁹ and their activated kinases correlated positively with those of oligomeric Aβ plaques and were negatively associated with episodic and working memory, even after adjusting for Aβ plaques, neurofibrillary tangles, and APOE ε4. Brain insulin resistance thus appears to be an early and common feature of AD, a phenomenon accompanied by IGF-1 resistance and closely associated with IRS-1 dysfunction potentially triggered by Aβ oligomers and yet promoting cognitive decline independent of classic AD pathology.
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Affiliation(s)
- Konrad Talbot
- Department of Psychiatry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-3403, USA.
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Fatani S, Itua I, Clark P, Wong C, Naderali EK. The effects of diet-induced obesity on hepatocyte insulin signaling pathways and induction of non-alcoholic liver damage. Int J Gen Med 2011; 4:211-9. [PMID: 21475632 PMCID: PMC3068881 DOI: 10.2147/ijgm.s17376] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2011] [Indexed: 12/12/2022] Open
Abstract
The prevalence of diet-induced obesity is increasing amongst adults and children worldwide, predisposing millions of people to an array of health problems that include metabolic syndrome, non-alcoholic fatty liver disease and non-alcoholic steatohepatitis. In this study we used experimental animals to investigate the effects of dietary obesity on markers of hepatic insulin signaling as well as structural changes in hepatocytes. Adult male Wistar rats were randomized and assigned to either a control group or a test group. Controls were fed standard laboratory pelleted diet (chow-fed), while the test group had free access to a highly-palatable diet (HPD). After eight weeks, the HPD-fed animals were subdivided into three subgroups and their diets altered as follows: HPD-to-chow, HPD with the addition of fenofibrate given by oral gavage for a further seven weeks, or HPD with vehicle (1% carboxymethylcellulose at 1 mL/kg body weight) given by oral gavage for a further seven weeks, respectively. Untreated diet-fed animals had significantly higher body weight, liver weight, and all measured metabolic profiles compared with chow-fed and treated diet-fed groups. Expression of kinases IRβ, IRS-1, AKt, eNOS, Shc and ERK1/2 were unaffected by obesity, while IRS-2 and P I3 kinase levels were significantly reduced in untreated HPD animals. Compared with chow-fed animals, steatosis and steatohepatitis were almost doubled in animals from untreated HPD, while removal of HPD and fenofibrate-treatment reduced steatosis by 40% and 80% respectively. These data suggest that diet-induced obesity affects intracellular insulin signaling mechanisms, namely IRS-2 and PI 3-kinase, leading to hepatic insulin resistance. Moreover, diet-induced obesity induces fatty liver, an effect which can be reversed by either removal of the source of obesity or treatment with fenofibrate, a peroxisome proliferator-activated receptor alpha agonist.
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Affiliation(s)
- Sameer Fatani
- Obesity Biology Unit, School of Clinical Sciences, University of Liverpool, Liverpool, UK
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Wu N, Lu Y, He B, Zhang Y, Lin J, Zhao S, Zhang W, Li Y, Han P. Taurine prevents free fatty acid-induced hepatic insulin resistance in association with inhibiting JNK1 activation and improving insulin signaling in vivo. Diabetes Res Clin Pract 2010; 90:288-96. [PMID: 20855122 DOI: 10.1016/j.diabres.2010.08.020] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2010] [Revised: 08/09/2010] [Accepted: 08/19/2010] [Indexed: 10/19/2022]
Abstract
We infused the 48 h intralipid plus heparin (IH) to normal rats to elevate plasma free fatty acids (FFAs). Co-infusion of taurine was designed for the purpose of studying the effects of taurine on insulin sensitivity, oxidative stress, c-Jun NH-terminal kinase (JNK)1 activity and insulin signaling in livers of prolonged IH-infused rats. Cannulated rats were infused for 48 h intravenously with either saline or IH, with or without taurine. Hyperinsulinemic-euglycemic clamps with [6-3H] glucose infusion were performed to assess hepatic insulin sensitivity. IH infusion increased plasma 8-isoprostaglandin and hepatic malondialdehyde (MDA). IH also increased JNK1 activity and insulin receptor substrate 1/2 (IRS-1/2) serine phosphorylation, reduced insulin-stimulated IRS-1/2 tyrosine phosphorylation and Akt serine 473 phosphorylation, and induced hepatic insulin resistance. Taurine co-infusion with IH prevented the rise in 8-isoprostaglandin and MDA, inhibited the activation of JNK1, and improved insulin signaling and insulin resistance in liver. The present study has demonstrated that taurine, as an antioxidant, prevented hepatic oxidative stress and ameliorated hepatic insulin resistance. And this effect may be associated with the inhibition of JNK1 activation and the improvement of insulin signaling. This study suggests the therapeutic value of taurine in protecting from hepatic insulin resistance caused by elevated FFAs.
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Affiliation(s)
- Na Wu
- Department of Endocrinology, Shengjing Hospital of China Medical University, Shenyang 110004, China
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Ginkgo biloba extract enhances glucose tolerance in hyperinsulinism-induced hepatic cells. J Nat Med 2010; 65:50-6. [DOI: 10.1007/s11418-010-0456-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2010] [Accepted: 07/20/2010] [Indexed: 11/25/2022]
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Kim B, Feldman EL. Insulin receptor substrate (IRS)-2, not IRS-1, protects human neuroblastoma cells against apoptosis. Apoptosis 2009; 14:665-73. [PMID: 19259821 DOI: 10.1007/s10495-009-0331-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Insulin receptor substrates (IRS)-1 and -2 are major substrates of insulin and type I insulin-like growth factor (IGF-I) receptor (IGF-IR) signaling. In this study, SH-EP human neuroblastoma cells are used as a model system to examine the differential roles of IRS-1 and IRS-2 on glucose-mediated apoptosis. In the presence of high glucose, IRS-1 underwent caspase-mediated degradation, followed by focal adhesion kinase (FAK) and Akt degradation and apoptosis. IRS-2 expression blocked all these changes whereas IRS-1 overexpression had no effect. In parallel, IRS-2, but not IRS-1, overexpression enhanced IGF-I-mediated Akt activation without affecting extracellular regulated kinase signaling. While IRS-1 was readily degraded by caspases, hyperglycemia-mediated IRS-2 degradation was unaffected by caspase inhibitors but blocked by proteasome and calpain inhibitors. Our data suggest that the differential degradation of IRS-1 and IRS-2 contributes to their distinct modes of action and the increased neuroprotective effects of IRS-2 in this report are due, in part, to its resistance to caspase-mediated degradation.
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Affiliation(s)
- Bhumsoo Kim
- Department of Neurology, University of Michigan, 5371 BSRB, 109 Zina Pitcher Place, Ann Arbor, MI 48109-2200, USA.
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The Irs1 branch of the insulin signaling cascade plays a dominant role in hepatic nutrient homeostasis. Mol Cell Biol 2009; 29:5070-83. [PMID: 19596788 DOI: 10.1128/mcb.00138-09] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We used a Cre-loxP approach to generate mice with varied expression of hepatic Irs1 and Irs2 to establish the contribution of each protein to hepatic nutrient homeostasis. While nutrient-sensitive transcripts were expressed nearly normally in liver lacking Irs2 (LKO2 mice), these transcripts were significantly dysregulated in liver lacking Irs1 (LKO1 mice) or Irs1 and Irs2 together (DKO mice). Similarly, a set of key gluconeogenic and lipogenic genes was regulated nearly normally by feeding in liver retaining a single Irs1 allele without Irs2 (DKO/1 mice) but was poorly regulated in liver retaining one Irs2 allele without Irs1 (DKO/2 mice). DKO/2 mice, but not DKO/1 mice, also showed impaired glucose tolerance and insulin sensitivity-though both Irs1 and Irs2 were required to suppress hepatic glucose production during hyperinsulinemic-euglycemic clamp. In contrast, either hepatic Irs1 or Irs2 mediated suppression of HGP by intracerebroventricular insulin infusion. After 12 weeks on a high-fat diet, postprandial tyrosine phosphorylation of Irs1 increased in livers of control and LKO2 mice, whereas tyrosine phosphorylation of Irs2 decreased in control and LKO1 mice. Moreover, LKO1 mice -- but not LKO2 mice -- that were fed a high-fat diet developed postprandial hyperglycemia. We conclude that Irs1 is the principal mediator of hepatic insulin action that maintains glucose homeostasis.
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Abstract
An understanding of the mechanisms that govern pancreatic endocrine cell ontogeny may offer strategies for their somatic replacement in diabetic patients. During embryogenesis, transcription factor FoxO1 is expressed in pancreatic progenitor cells. Subsequently, it becomes restricted to beta cells and to a rare population of insulin-negative juxtaductal cells (FoxO1+ Ins(-)). It is unclear whether FoxO1+ Ins(-) cells give rise to endocrine cells. To address this question, we first evaluated FoxO1's role in pancreas development using gain- and loss-of-function alleles in mice. Premature FoxO1 activation in pancreatic progenitors promoted alpha-cell formation but curtailed exocrine development. Conversely, FoxO1 ablation in pancreatic progenitor cells, but not in committed endocrine progenitors or terminally differentiated beta cells, selectively increased juxtaductal beta cells. As these data indicate an involvement of FoxO1 in pancreatic lineage determination, FoxO1+ Ins(-) cells were clonally isolated and assayed for their capacity to undergo endocrine differentiation. Upon FoxO1 activation, FoxO1+ Ins(-) cultures converted into glucagon-producing cells. We conclude that FoxO1+ Ins(-) juxtaductal cells represent a hitherto-unrecognized pancreatic cell population with in vitro capability of endocrine differentiation.
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Wan XD, Yang WB, Xia YZ, Wang JF, Lu T, Wang XM. Disruption of glucose homeostasis and induction of insulin resistance by elevated free fatty acids in human L02 hepatocytes. J Endocrinol Invest 2009; 32:454-9. [PMID: 19494713 DOI: 10.1007/bf03346485] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Free fatty acids (FFA) have been implicated as an important causative link between obesity, insulin resistance, and Type 2 diabetes. However, the underlying mechanisms especially for FFA-mediated hepatic insulin resistance are not fully elucidated. Here, we investigated the impaired sites in insulin signaling pathways and mechanisms of insulin resistance induced by elevated FFA in L02 hepatocytes. L02 cells were cultured in Dulbecco's modified eagle medium containing various concentrations of palmitic acid (PA) for 24 h followed by 10(-7) mol/l insulin stimulation. In some experiments, cells were pre-treated with enzymatic inhibitor Wortmannin (10(-6) mol/l). Glucose levels in medium, cytosolic glycogen contents, and phosphoenolpyruvate carboxykinase (PEPCK) activity were measured. Protein level of insulin receptor substrate (IRS)-2 and phosphorylated Akt were detected by Western blot analysis. L02 cells treated with high levels of PA exhibited increased glucose levels, whereas hepatic glycogen contents were decreased in a dose-dependent manner as compared to the control cells. There was a significant attenuation of IRS- 2 protein expression in the cells cultured with PA, and Wortmannin intervention exhibited different IRS-2 protein level with or without PA treatment. In accordance with the reduced IRS-2 level, the insulin-stimulated phosphorylation of Akt was diminished in the PA-treated cells. Basal PEPCK activity and insulin- regulated PEPCK activity were overstimulated in the cells incubated with PA. These data indicate high levels of FFA can disrupt glucose homeostasis, inflict some defects in insulin signaling, and induce insulin resistance in L02 cells.
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Affiliation(s)
- X-D Wan
- Department of Biochemistry and Molecular Biology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, P. R. China
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Malaguarnera M, Di Rosa M, Nicoletti F, Malaguarnera L. Molecular mechanisms involved in NAFLD progression. J Mol Med (Berl) 2009; 87:679-95. [PMID: 19352614 DOI: 10.1007/s00109-009-0464-1] [Citation(s) in RCA: 208] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2008] [Revised: 02/26/2009] [Accepted: 03/18/2009] [Indexed: 02/06/2023]
Abstract
Non-alcoholic fatty liver disease (NAFLD) is an emerging metabolic-related disorder characterized by fatty infiltration of the liver in the absence of alcohol consumption. NAFLD ranges from simple steatosis to non-alcoholic steatohepatitis (NASH), which might progress to end-stage liver disease. This progression is related to the insulin resistance, which is strongly linked to the metabolic syndrome consisting of central obesity, diabetes mellitus, and hypertension. Earlier, the increased concentration of intracellular fatty acids within hepatocytes leads to steatosis. Subsequently, multifactorial complex interactions between nutritional factors, lifestyle, and genetic determinants promote necrosis, inflammation, fibrosis, and hepatocellular damage. Up to now, many studies have revealed the mechanism associated with insulin resistance, whereas the mechanisms related to the molecular components have been incompletely characterized. This review aims to assess the potential molecular mediators initiating and supporting the progression of NASH to establish precocious diagnosis and to plan more specific treatment for this disease.
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Ruddock MW, Stein A, Landaker E, Park J, Cooksey RC, McClain D, Patti ME. Saturated fatty acids inhibit hepatic insulin action by modulating insulin receptor expression and post-receptor signalling. J Biochem 2008; 144:599-607. [PMID: 18713797 DOI: 10.1093/jb/mvn105] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Free fatty acids (FFAs) are proposed to play a pathogenic role in both peripheral and hepatic insulin resistance. We have examined the effect of saturated FFA on insulin signalling (100 nM) in two hepatocyte cell lines. Fao hepatoma cells were treated with physiological concentrations of sodium palmitate (0.25 mM) (16:0) for 0.25-48 h. Palmitate decreased insulin receptor (IR) protein and mRNA expression in a dose- and time-dependent manner (35% decrease at 12 h). Palmitate also reduced insulin-stimulated IR and IRS-2 tyrosine phosphorylation, IRS-2-associated PI 3-kinase activity, and phosphorylation of Akt, p70 S6 kinase, GSK-3 and FOXO1A. Palmitate also inhibited insulin action in hepatocytes derived from wild-type IR (+/+) mice, but was ineffective in IR-deficient (-/-) cells. The effects of palmitate were reversed by triacsin C, an inhibitor of fatty acyl CoA synthases, indicating that palmitoyl CoA ester formation is critical. Neither the non-metabolized bromopalmitate alone nor the medium chain fatty acid octanoate (8:0) produced similar effects. However, the CPT-1 inhibitor (+/-)-etomoxir and bromopalmitate (in molar excess) reversed the effects of palmitate. Thus, the inhibition of insulin signalling by palmitate in hepatoma cells is dependent upon oxidation of fatty acyl-CoA species and requires intact insulin receptor expression.
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Affiliation(s)
- Mark W Ruddock
- Research Division, Cellular & Molecular Physiology, Joslin Diabetes Centre, and Harvard Medical School, 1 Joslin Place, Boston, MA 02215, USA.
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González-Rodriguez A, Nevado C, Escrivá F, Sesti G, Rondinone CM, Benito M, Valverde AM. PTP1B deficiency increases glucose uptake in neonatal hepatocytes: involvement of IRA/GLUT2 complexes. Am J Physiol Gastrointest Liver Physiol 2008; 295:G338-47. [PMID: 18535291 DOI: 10.1152/ajpgi.00514.2007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The contribution of the liver to glucose utilization is essential to maintain glucose homeostasis. Previous data from protein tyrosine phosphatase (PTP) 1B-deficient mice demonstrated that the liver is a major site for PTP1B action in the periphery. In this study, we have investigated the consequences of PTP1B deficiency in glucose uptake in hepatocytes from neonatal and adult mice. The lack of PTP1B increased basal glucose uptake in hepatocytes from neonatal (3-5 days old) but not adult (10-12 wk old) mice. This occurs without changes in hexokinase, glucokinase, and glucose 6-phosphatase enzymatic activities. By contrast, the glucose transporter GLUT2 was upregulated at the protein level in neonatal hepatocytes and livers from PTP1B-deficient neonates. These results were accompanied by a significant increase in the net free intrahepatic glucose levels in the livers of PTP1B(-/-) neonates. The association between GLUT2 and insulin receptor (IR) A isoform was increased in PTP1B(-/-) neonatal hepatocytes compared with the wild-type. Indeed, PTP1B deficiency in neonatal hepatocytes shifted the ratio of isoforms A and B of the IR by increasing the amount of IRA and decreasing IRB. Moreover, overexpression of IRA in PTP1B(-/-) neonatal hepatocytes increased the amount of IRA/GLUT2 complexes. Conversely, hepatocytes from adult mice only expressed IRB. Since IRA plays a direct role in the regulation of glucose uptake in neonatal hepatocytes through its specific association with GLUT2, we propose the increase in IRA/GLUT2 complexes due to PTP1B deficiency as the molecular mechanism of the increased glucose uptake in the neonatal stage.
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Affiliation(s)
- Agueda González-Rodriguez
- Instituto de Investigaciones Biomédicas Alberto Sols, C/ Arturo Pérez Duperier 4, 28029 Madrid, Spain
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Long-term consumption of saponins derived from Platycodi radix (22 years old) enhances hepatic insulin sensitivity and glucose-stimulated insulin secretion in 90 % pancreatectomized diabetic rats fed a high-fat diet. Br J Nutr 2008; 101:358-66. [PMID: 18577298 DOI: 10.1017/s000711450801218x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Crude saponins derived from Chinese Platycodi radix have been reported to prevent increases in body weight and liver TAG in mice fed a high-fat diet. We investigated the effects of an extract (PR) taken from Korean Platycodi radix, which is cultivated for 22 years in the ground (Jangsaeng doraji), and its saponins (PRS) on insulin resistance and glucose-stimulated insulin secretion in 90 % pancreatectomized diabetic rats fed high-fat diets. Four groups were orally supplemented with 2 g PR, 0.2 g PRS, 20 mg rosiglitazone (positive control) or 0.5 g cellulose (negative control) per kg body weight on a daily basis for 8 weeks. We found that PRS lowered body weight, visceral fat mass and serum leptin levels in pancreatectomized rats in comparison to the control. PR enhanced first- and second-phase insulin secretion while PRS stimulated only first-phase insulin secretion. Glucose infusion rates to maintain euglycaemia at hyperinsulinaemic states decreased in a descending order of rosiglitazone, PRS, PR and control, but they increased hepatic glucose output in the same order. This reduction was associated with the storage of decreased TAG and increased glycogen, which was a result of enhanced tyrosine phosphorylation of anti-insulin receptor substrate-2 and serine473 phosphporylation of protein kinase B (PKB, Akt). Improved hepatic insulin signalling led to decreased phosphoenolpyruvate carboxykinase expression and reduced hepatic glucose output accordingly. In conclusion, PRS principally improves glucose homeostasis by enhancing hepatic insulin sensitivity as a consequence of reducing fat storage and stimulating insulin signalling in diabetic rats. In addition, PR contains components that promote glucose-stimulated insulin secretion.
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Koschorreck M, Gilles ED. Mathematical modeling and analysis of insulin clearance in vivo. BMC SYSTEMS BIOLOGY 2008; 2:43. [PMID: 18477391 PMCID: PMC2430945 DOI: 10.1186/1752-0509-2-43] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/24/2007] [Accepted: 05/13/2008] [Indexed: 01/13/2023]
Abstract
BACKGROUND Analyzing the dynamics of insulin concentration in the blood is necessary for a comprehensive understanding of the effects of insulin in vivo. Insulin removal from the blood has been addressed in many studies. The results are highly variable with respect to insulin clearance and the relative contributions of hepatic and renal insulin degradation. RESULTS We present a dynamic mathematical model of insulin concentration in the blood and of insulin receptor activation in hepatocytes. The model describes renal and hepatic insulin degradation, pancreatic insulin secretion and nonspecific insulin binding in the liver. Hepatic insulin receptor activation by insulin binding, receptor internalization and autophosphorylation is explicitly included in the model. We present a detailed mathematical analysis of insulin degradation and insulin clearance. Stationary model analysis shows that degradation rates, relative contributions of the different tissues to total insulin degradation and insulin clearance highly depend on the insulin concentration. CONCLUSION This study provides a detailed dynamic model of insulin concentration in the blood and of insulin receptor activation in hepatocytes. Experimental data sets from literature are used for the model validation. We show that essential dynamic and stationary characteristics of insulin degradation are nonlinear and depend on the actual insulin concentration.
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Affiliation(s)
- Markus Koschorreck
- Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstr, 1, 39106 Magdeburg, Germany.
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Ezzat VA, Duncan ER, Wheatcroft SB, Kearney MT. The role of IGF-I and its binding proteins in the development of type 2 diabetes and cardiovascular disease. Diabetes Obes Metab 2008; 10:198-211. [PMID: 18269635 DOI: 10.1111/j.1463-1326.2007.00709.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Patients with insulin resistance and type 2 diabetes have an excessive risk of cardiovascular disease (CVD); this increased risk is not fully explained by traditional risk factors such as hypertension and dyslipidaemias. There is now compelling evidence to suggest that abnormalities of insulin-like growth factor-I (IGF-I) and one of its binding proteins, insulin-like growth factor-binding protein-1 (IGFBP-1), occur in insulin-resistant states and may be significant factors in the pathophysiology of CVD. We reviewed articles and relevant bibliographies following a systematic search of MEDLINE for English language articles between 1966 and the present, using an initial search strategy combining the MeSH terms: IGF, diabetes and CVD. Our aim was first to review the role of IGF-I in vascular homeostasis and to explore the mechanisms by which it may exert its effects. We also present an overview of the physiology of the IGF-binding proteins, and finally, we sought to summarize the evidence to date describing the changes in the insulin/IGF-I/IGFBP-1 axis that occur in type 2 diabetes and CVD; in particular, we have focused on the potential vasculoprotective effects of both IGF-I and IGFBP-1. We conclude that this system represents an interesting and novel therapeutic target in the prevention of CVD in type 2 diabetes.
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Affiliation(s)
- Vivienne A Ezzat
- Cardiovascular Division, The James Black Centre, Kings College London, Denmark Hill Campus, London, UK
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Dongiovanni P, Valenti L, Ludovica Fracanzani A, Gatti S, Cairo G, Fargion S. Iron depletion by deferoxamine up-regulates glucose uptake and insulin signaling in hepatoma cells and in rat liver. THE AMERICAN JOURNAL OF PATHOLOGY 2008; 172:738-47. [PMID: 18245813 DOI: 10.2353/ajpath.2008.070097] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Iron depletion improves insulin resistance in patients with nonalcoholic fatty liver disease and diabetes and also stabilizes the hypoxia-inducible factor (HIF)-1, resulting in increased glucose uptake in vitro. This study investigated the effect of iron depletion by deferoxamine on insulin signaling and glucose uptake in HepG2 hepatocytes and in rat liver. In HepG2 cells, deferoxamine stabilized HIF-1alpha and induced the constitutive glucose transporter Glut1 and the insulin receptor. Up-regulation of insulin receptor by deferoxamine was mimicked by the intracellular iron chelator deferasirox and the hypoxia inducer CoCl2 and required the HIF-1 obligate partner ARNT/HIF-1beta. Iron depletion increased insulin receptor activity, whereas iron supplementation had the opposite effect. Deferoxamine consistently increased the phosphorylation status of Akt/PKB and its targets FoxO1 and Gsk3beta, which mediate the effect of insulin on gluconeogenesis and glycogen synthesis, and up-regulated genes involved in glucose uptake and utilization. Iron depletion of Sprague-Dawley rats increased HIF-1alpha expression, improved glucose clearance, and was associated with up-regulation of insulin receptor and Akt/PKB levels and of glucose transport in hepatic tissue. Conversely, gluconeogenic genes were not affected. In rats with fatty liver because of a high-calorie and high-fat diet, glucose clearance was increased by iron depletion and decreased by iron supplementation. Thus, iron depletion by deferoxamine up-regulates glucose uptake, and increases insulin receptor activity and signaling in hepatocytes in vitro and in vivo.
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Affiliation(s)
- Paola Dongiovanni
- Department of Internal Medicine, Ospedale Maggiore Policlinico Mangiagalli Regina Elena Istituto Ricovero e Cura a Carattere Scientifico, Milano, Italy
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Koschorreck M, Conzelmann H, Ebert S, Ederer M, Gilles ED. Reduced modeling of signal transduction - a modular approach. BMC Bioinformatics 2007; 8:336. [PMID: 17854494 PMCID: PMC2216040 DOI: 10.1186/1471-2105-8-336] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2007] [Accepted: 09/13/2007] [Indexed: 12/18/2022] Open
Abstract
Background Combinatorial complexity is a challenging problem in detailed and mechanistic mathematical modeling of signal transduction. This subject has been discussed intensively and a lot of progress has been made within the last few years. A software tool (BioNetGen) was developed which allows an automatic rule-based set-up of mechanistic model equations. In many cases these models can be reduced by an exact domain-oriented lumping technique. However, the resulting models can still consist of a very large number of differential equations. Results We introduce a new reduction technique, which allows building modularized and highly reduced models. Compared to existing approaches further reduction of signal transduction networks is possible. The method also provides a new modularization criterion, which allows to dissect the model into smaller modules that are called layers and can be modeled independently. Hallmarks of the approach are conservation relations within each layer and connection of layers by signal flows instead of mass flows. The reduced model can be formulated directly without previous generation of detailed model equations. It can be understood and interpreted intuitively, as model variables are macroscopic quantities that are converted by rates following simple kinetics. The proposed technique is applicable without using complex mathematical tools and even without detailed knowledge of the mathematical background. However, we provide a detailed mathematical analysis to show performance and limitations of the method. For physiologically relevant parameter domains the transient as well as the stationary errors caused by the reduction are negligible. Conclusion The new layer based reduced modeling method allows building modularized and strongly reduced models of signal transduction networks. Reduced model equations can be directly formulated and are intuitively interpretable. Additionally, the method provides very good approximations especially for macroscopic variables. It can be combined with existing reduction methods without any difficulties.
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Affiliation(s)
- Markus Koschorreck
- Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstr. 1, 39106 Magdeburg, Germany
| | - Holger Conzelmann
- Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstr. 1, 39106 Magdeburg, Germany
| | - Sybille Ebert
- Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstr. 1, 39106 Magdeburg, Germany
| | - Michael Ederer
- Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstr. 1, 39106 Magdeburg, Germany
| | - Ernst Dieter Gilles
- Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstr. 1, 39106 Magdeburg, Germany
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Reddy RC, Hao Y, Lee SH, Gangireddy SR, Owyang C, DiMagno MJ. Pioglitazone reverses insulin resistance and impaired CCK-stimulated pancreatic secretion in eNOS(-/-) mice: therapy for exocrine pancreatic disorders? Am J Physiol Gastrointest Liver Physiol 2007; 293:G112-20. [PMID: 17510194 DOI: 10.1152/ajpgi.00442.2006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
In mice, eNOS (endothelial nitric oxide synthase) maintains in vivo pancreatic secretory responses to carbachol or cholecystokinin octapeptide (CCK-8), maintains insulin sensitivity, and modulates pancreatic microvascular blood flow (PMBF). eNOS(-/-) mice are insulin resistant, and their exocrine pancreatic secretion is impaired. We hypothesized that the reduced exocrine pancreatic secretion in eNOS(-/-) mice is due to insulin resistance or impaired PMBF. To test this hypothesis, we gave eNOS(-/-) and wild-type (WT) mice pioglitazone (20 or 50 mg.kg(-1).day(-1)), an insulin-sensitizing peroxisome proliferator-activated receptor-gamma (PPAR-gamma) activator, and measured pancreatic protein secretion evoked by CCK-8 (160 pmol.kg(-1).h(-1), a maximal stimulus). We also measured insulin resistance, serum glucose, C-peptide, insulin, pancreatic RNA digestive enzyme expression, and PMBF (microsphere technique). In WT mice, pioglitazone did not increase CCK-8-stimulated protein output over baseline. In eNOS(-/-) mice, however, pioglitazone substantially increased the low CCK-8-stimulated protein output that is characteristic of these mutant mice (P < 0.005). Pioglitazone abolished the CCK-8-evoked hyperinsulinemia (P < 0.005) and increased insulin sensitivity of eNOS(-/-) mice (P < 0.05), the latter based on hyperinsulinemic-euglycemic clamp studies. Pioglitazone had no effect on PMBF or pancreas mRNA expression of insulin or digestive enzymes. We conclude that in hyperinsulinemic eNOS(-/-) mice, a nonobese model of insulin resistance relevant to diabetes mellitus and possibly chronic pancreatitis, reduced pancreatic secretion is caused, at least in part, by insulin resistance. Insulin-sensitizing PPAR-gamma agonists such as pioglitazone may thus simultaneously correct endocrine and exocrine pancreatic disorders.
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Affiliation(s)
- Raju C Reddy
- Department of Internal Medicine, Division of Gastroenterology and Hepatology, University of Michigan School of Medicine, 1150 W. Medical Center Drive, 6520 MSRB 1, Ann Arbor, MI 48109, USA
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Holzman JL, Liu L, Duke BJ, Kemendy AE, Eaton DC. Transactivation of the IGF-1R by aldosterone. Am J Physiol Renal Physiol 2007; 292:F1219-28. [PMID: 17190911 DOI: 10.1152/ajprenal.00214.2006] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Activation of epithelial sodium channels (ENaC) by aldosterone, insulin, or insulin-like growth factor-1 (IGF-1) in renal epithelial cells (including the Xenopus laevis renal cell line A6) appears to share some common signaling elements subsequent to the initial insulin or IGF-1 receptor activation. Previously, the convergence point for insulin or IGF-1 and aldosterone signaling was assumed to be downstream of the receptor at the level of phosphatidylinositol 3-kinase (PI3-K); however, this study shows aldosterone directly transactivates the IGF-1 receptor (IGF-1R). In A6 cells, 10-min exposure to aldosterone increased the phosphorylation of the IGF-1 receptor, insulin receptor substrate-1 (IRS-1), and Akt (PKB). Furthermore, aldosterone activated PI3-K and phosphorylation of the most downstream element, Akt, was blocked by the specific PI3-K inhibitor LY-294002. Transactivation requires aldosterone binding to the mineralocorticoid/glucocorticoid receptor and does not require transcription.
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Affiliation(s)
- Jennifer L Holzman
- Emory Univ. School of Medicine, Dept. of Medicine, Renal Div., 1639 Pierce Dr., Rm. 3327, Atlanta, GA 30322, USA.
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41
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Cho Y, Ariga M, Uchijima Y, Kimura K, Rho JY, Furuhata Y, Hakuno F, Yamanouchi K, Nishihara M, Takahashi SI. The novel roles of liver for compensation of insulin resistance in human growth hormone transgenic rats. Endocrinology 2006; 147:5374-84. [PMID: 16916956 DOI: 10.1210/en.2006-0518] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Chronic excess of GH is known to cause hyperinsulinemia and insulin resistance. We developed human GH transgenic (TG) rats, which were characterized by high plasma levels of human GH and IGF-I. These TG rats showed higher levels of plasma insulin, compared with control littermates, whereas plasma glucose concentrations were normal. Insulin-dependent glucose uptake into adipocytes and muscle was impaired, suggesting that these rats developed insulin resistance. In contrast, insulin-independent glucose uptake into hepatocytes from TG rats was significantly increased, and glycogen and lipid levels in livers of TG rats were remarkably high. Because the role of liver in GH-induced insulin resistance is poorly understood, we studied insulin signaling at early stages and insulin action in liver and primary cultures of hepatocytes prepared from TG rats. There was no difference in insulin receptor kinase activity induced by insulin between TG and control rats; however, insulin-dependent insulin receptor substrate-2 tyrosine phosphorylation, glycogen synthase activation, and expression of enzymes that induce lipid synthesis were potentiated in hepatocytes of TG rats. These results suggest that impairment of insulin-dependent glucose uptake by GH excess in adipose tissue and muscle is compensated by up-regulation of glucose uptake in liver and that potentiation of insulin signaling through insulin receptor substrate-2 in liver experiencing GH excess causes an increase in glycogen and lipid synthesis from incorporated glucose, resulting in accumulation of glycogen and lipids in liver. This novel mechanism explains normalization of plasma glucose levels at least in part in a GH excess model.
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Affiliation(s)
- Yoshitake Cho
- Department of Animal Sciences , Graduate School of Agriculture and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
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42
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Villarreal RS, Alvarez SE, Ayub MJ, Ciuffo GM. Angiotensin II modulates tyr-phosphorylation of IRS-4, an insulin receptor substrate, in rat liver membranes. Mol Cell Biochem 2006; 293:35-46. [PMID: 16933034 DOI: 10.1007/s11010-006-2492-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2004] [Accepted: 08/26/2005] [Indexed: 12/22/2022]
Abstract
Angiotensin II (Ang II), a major regulator of blood pressure, is also involved in the control of cellular proliferation and hypertrophy and might exhibit additional actions in vivo by modulating the signaling of other hormones. As hypertension and Insulin (Ins) resistance often coexist and are risk factors for cardiovascular diseases, Ang II and Insulin signaling cross-talk may have an important role in hypertension development. The effect of Ins on protein tyrosine phosphorylation was assayed in rat liver membrane preparations, a rich source of Ins receptors. Following stimulation, Ins (10(-7) M) induced tyr-phosphorylation of different proteins. Insulin consistently induced tyr-phosphorylation of a 160 kDa protein (pp160) with maximum effect between 1 and 3 min. The pp160 protein was identified by anti-IRS-4 but not by anti-IRS-1 antibody. Pre-stimulation with Ang II (10(-7) M) diminishes tyr-phosphorylation level of pp160/IRS-4 in a dose-dependent manner. Okadaic acid, the PP1A and PP2A Ser/Thr phosphatase inhibitor, increases pp160 phosphorylation induced by Ins and prevents the inhibitory effect of Ang II pre-stimulation. Genistein, a tyrosine kinase inhibitor, diminishes tyr-phosphorylation level of IRS-4. PI3K inhibitors Wortmanin and LY294002, both increase tyr-phosphorylation of IRS-4, either in the presence of Ins alone or combined with Ang II. These results suggest that Ins and Ang II modulate IRS-4 tyr-phosphorylation in a PI3K-dependent manner. In summary, we showed that Ins induces tyr-phosphorylation of IRS-4, an effect modulated by Ang II. Assays performed in the presence of different inhibitors points toward a PI3K involvement in this signaling pathway.
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Affiliation(s)
- Rodrigo S Villarreal
- Bioquímica Avanzada, Departamento Bioquímica y Ciencias Biológicas, Facultad de Química, Bioquímica y Farmacia, Universidad Nacional de San Luis, Ejército de los Andes, 950-5700 San Luis, Argentina
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43
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Matsumoto M, Han S, Kitamura T, Accili D. Dual role of transcription factor FoxO1 in controlling hepatic insulin sensitivity and lipid metabolism. J Clin Invest 2006; 116:2464-72. [PMID: 16906224 PMCID: PMC1533874 DOI: 10.1172/jci27047] [Citation(s) in RCA: 214] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2005] [Accepted: 06/16/2006] [Indexed: 12/12/2022] Open
Abstract
Hepatic insulin resistance affects both carbohydrate and lipid metabolism. It has been proposed that insulin controls these 2 metabolic branches through distinct signaling pathways. FoxO transcription factors are considered effectors of the pathway regulating hepatic glucose production. Here we show that adenoviral delivery of constitutively nuclear forkhead box O1 (FoxO1) to mouse liver results in steatosis arising from increased triglyceride accumulation and decreased fatty acid oxidation. FoxO1 gain of function paradoxically increased insulin sensitivity by promoting Akt phosphorylation, while FoxO1 inhibition via siRNA decreased it. We show that FoxO1 regulation of Akt phosphorylation does not require DNA binding and is associated with repression of the pseudokinase tribble 3 (Trb3), a modulator of Akt activity. This unexpected dual role of FoxO1 in promoting insulin sensitivity and lipid synthesis in addition to glucose production has the potential to explain the peculiar admixture of insulin resistance and sensitivity that is commonly observed in the metabolic syndrome.
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Affiliation(s)
- Michihiro Matsumoto
- Department of Medicine, Columbia University Medical Center, New York, New York 10032, USA
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44
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Riojas RA, Kikani CK, Wang C, Mao X, Zhou L, Langlais PR, Hu D, Roberts JL, Dong LQ, Liu F. Fine tuning PDK1 activity by phosphorylation at Ser163. J Biol Chem 2006; 281:21588-21593. [PMID: 16751192 DOI: 10.1074/jbc.m600393200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
3-Phosphoinositide-dependent protein kinase-1 (PDK1) mediates phosphorylation and activation of members of the AGC protein kinase family and plays an essential role in insulin signaling and action. However, whether and how PDK1 activity is regulated in cells remains largely uncharacterized. In the present study, we show that PDK1 undergoes insulin-stimulated and phosphatidylinositol 3-kinase-dependent phosphorylation at Ser244 in the activation loop and at a novel site: Ser163 in the hinge region between the two lobes of the kinase domain. Sequence alignment studies revealed that the residue corresponding to Ser163 of PDK1 in all other AGC kinases is glutamate, suggesting that a negative charge at this site may be important for PDK1 function. Replacing Ser163 with a negatively charged residue, glutamate, led to a 2-fold increase in PDK1 activity. Molecular modeling studies suggested that phosphorylated Ser163 may form additional hydrogen bonds with Tyr149 and Gln223. In support of this, mutation of Tyr149 to Ala is sufficient to reduce PDK1 activity. Taken together, our results suggest that PDK1 phosphorylation of Ser163 may provide a mechanism to fine-tune PDK1 activity and function in cells.
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Affiliation(s)
- Ramon A Riojas
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas 78229
| | - Chintan K Kikani
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas 78229
| | - Changhua Wang
- Department of Pharmacology, University of Texas Health Science Center, San Antonio, Texas 78229
| | - Xuming Mao
- Department of Pharmacology, University of Texas Health Science Center, San Antonio, Texas 78229
| | - Lijun Zhou
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas 78229
| | - Paul R Langlais
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas 78229
| | - Derong Hu
- Department of Pharmacology, University of Texas Health Science Center, San Antonio, Texas 78229
| | - James L Roberts
- Department of Pharmacology, University of Texas Health Science Center, San Antonio, Texas 78229; Barshop Center for Longevity and Aging Studies, University of Texas Health Science Center, San Antonio, Texas 78229
| | - Lily Q Dong
- Department of Pharmacology, University of Texas Health Science Center, San Antonio, Texas 78229; Barshop Center for Longevity and Aging Studies, University of Texas Health Science Center, San Antonio, Texas 78229; Departments of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio, Texas 78229
| | - Feng Liu
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas 78229; Department of Pharmacology, University of Texas Health Science Center, San Antonio, Texas 78229; Barshop Center for Longevity and Aging Studies, University of Texas Health Science Center, San Antonio, Texas 78229.
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45
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Mao X, Kikani CK, Riojas RA, Langlais P, Wang L, Ramos FJ, Fang Q, Christ-Roberts CY, Hong JY, Kim RY, Liu F, Dong LQ. APPL1 binds to adiponectin receptors and mediates adiponectin signalling and function. Nat Cell Biol 2006; 8:516-23. [PMID: 16622416 DOI: 10.1038/ncb1404] [Citation(s) in RCA: 505] [Impact Index Per Article: 28.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2005] [Accepted: 03/17/2006] [Indexed: 02/06/2023]
Abstract
Adiponectin, also known as Acrp30, is an adipose tissue-derived hormone with anti-atherogenic, anti-diabetic and insulin sensitizing properties. Two seven-transmembrane domain-containing proteins, AdipoR1 and AdipoR2, have recently been identified as adiponectin receptors, yet signalling events downstream of these receptors remain poorly defined. By using the cytoplasmic domain of AdipoR1 as bait, we screened a yeast two-hybrid cDNA library derived from human fetal brain. This screening led to the identification of a phosphotyrosine binding domain and a pleckstrin homology domain-containing adaptor protein, APPL1 (adaptor protein containing pleckstrin homology domain, phosphotyrosine binding (PTB) domain and leucine zipper motif). APPL1 interacts with adiponectin receptors in mammalian cells and the interaction is stimulated by adiponectin. Overexpression of APPL1 increases, and suppression of APPL1 level reduces, adiponectin signalling and adiponectin-mediated downstream events (such as lipid oxidation, glucose uptake and the membrane translocation of glucose transport 4 (GLUT4)). Adiponectin stimulates the interaction between APPL1 and Rab5 (a small GTPase) interaction, leading to increased GLUT4 membrane translocation. APPL1 also acts as a critical regulator of the crosstalk between adiponectin signalling and insulin signalling pathways. These results demonstrate a key function for APPL1 in adiponectin signalling and provide a molecular mechanism for the insulin sensitizing function of adiponectin.
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Affiliation(s)
- Xuming Mao
- Department of Pharmacology, University of Texas Health Science Center, San Antonio, TX 78229-3900, USA
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Simmgen M, Knauf C, Lopez M, Choudhury AI, Charalambous M, Cantley J, Bedford DC, Claret M, Iglesias MA, Heffron H, Cani PD, Vidal-Puig A, Burcelin R, Withers DJ. Liver-specific deletion of insulin receptor substrate 2 does not impair hepatic glucose and lipid metabolism in mice. Diabetologia 2006; 49:552-61. [PMID: 16404553 DOI: 10.1007/s00125-005-0084-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2005] [Accepted: 09/25/2005] [Indexed: 10/25/2022]
Abstract
AIMS/HYPOTHESIS Hepatic insulin resistance is thought to be a critical component in the pathogenesis of type 2 diabetes but the role of intrinsic insulin signalling pathways in the regulation of hepatic metabolism remains controversial. Global gene targeting in mice and in vitro studies have suggested that IRS2 mediates the physiological effects of insulin in the liver. Reduced hepatic production of IRS2 is found in many cases of insulin resistance. To investigate the role of IRS2 in regulating liver function in vivo, we generated mice that specifically lack Irs2 in the liver (LivIrs2KO). MATERIALS AND METHODS Hepatic insulin signalling events were examined in LivIrs2KO mice by western blotting. Glucose homeostasis and insulin sensitivity were assessed by glucose tolerance tests and hyperinsulinaemic-euglycaemic clamp studies. The effects of high-fat feeding upon glucose homeostasis were also determined. Liver function tests were performed and expression of key metabolic genes in the liver was determined by RT-PCR. RESULTS Proximal insulin signalling events and forkhead box O1 and A2 function were normal in the liver of LivIrs2KO mice, which displayed minimal abnormalities in glucose and lipid homeostasis, hepatic gene expression and liver function. In addition, hepatic lipid homeostasis and the metabolic response to a high-fat diet did not differ between LivIrs2KO and control mice. CONCLUSIONS/INTERPRETATION Our findings suggest that liver IRS2 signalling, surprisingly, is not required for the long-term maintenance of glucose and lipid homeostasis, and that extra-hepatic IRS2-dependent mechanisms are involved in the regulation of these processes.
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Affiliation(s)
- M Simmgen
- Centre for Diabetes and Endocrinology, Rayne Institute, University College London, University Street, London, UK
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47
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Desbois-Mouthon C, Wendum D, Cadoret A, Rey C, Leneuve P, Blaise A, Housset C, Tronche F, Le Bouc Y, Holzenberger M. Hepatocyte proliferation during liver regeneration is impaired in mice with liver-specific IGF-1R knockout. FASEB J 2006; 20:773-5. [PMID: 16484330 DOI: 10.1096/fj.05-4704fje] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Recent evidence indicates that growth hormone (GH) is involved in liver regeneration. To test whether insulin-like growth factor I (IGF-I) mediates this effect, we studied liver regeneration induced by partial hepatectomy in liver-specific IGF type 1 receptor knockout (LIGFREKO) mice. The absence of IGF-1R caused a significant decrease in hepatocyte proliferation in males (-52%), but not in females, as assessed by Ki67 immunohistochemistry. Cyclin D1 and cyclin A protein levels in the livers of LIGFREKO males were only half those in controls, indicating that cyclin induction during liver regeneration is dependent on IGF-1R signaling. Analyzing the signaling cascade initiated by IGF-1R, we observed a lack of IRS-1 induction in LIGFREKO livers. In contrast, the induction of IRS-2 synthesis was similar in LIGFREKO and control groups, suggesting the existence of differential regulation of IRS synthesis during liver regeneration. Regenerating livers from LIGFREKO animals also showed significantly less activated ERKs than controls. Our findings demonstrate that IGF-1R makes a significant contribution to liver regeneration. Using the LIGFREKO model, we provide new evidence that IGF-1R/IRS-1/ERK signaling may be the intracellular pathway controlling the cell cycle via cyclin D1 and cyclin A in the regenerating liver.
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48
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Rakatzi I, Stosik M, Gromke T, Siddle K, Eckel J. Differential phosphorylation of IRS-1 and IRS-2 by insulin and IGF-I receptors. Arch Physiol Biochem 2006; 112:37-47. [PMID: 16754202 DOI: 10.1080/13813450500500332] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The specific contribution of insulin and IGF-I receptors to IRS-protein activation remains elusive. We studied the signalling properties of AspB10-insulin, an analog with enhanced affinity for the IGF-I receptor, in comparison to native insulin using primary human skeletal muscle cells. In myoblasts regular insulin and AspB10-insulin were equipotent in stimulating the IRS cascade, whereas this analog induced a significantly higher Shc phosphorylation. Phosphorylation of IRS-1 in response to insulin was inhibited equally by blocking either the insulin or the IGF-I receptor. IRS-1 activation by AspB10-insulin was only inhibited by blocking the IGF-I receptor. IRS-2 phosphorylation induced by both insulin and AspB10-insulin was nearly insensitive to blocking the insulin receptor, being predominantly mediated by the IGF-I receptor. We conclude that in myoblasts IRS-2, but not IRS-1, functions as preferred substrate for the IGF-I receptor. These data suggest a specific role for IRS-2 in growth and differentiation of human skeletal muscle.
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Affiliation(s)
- Irini Rakatzi
- Institute of Clinical Biochemistry and Pathobiochemistry, German Diabetes Center, Düsseldorf, Germany
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49
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Dong X, Park S, Lin X, Copps K, Yi X, White MF. Irs1 and Irs2 signaling is essential for hepatic glucose homeostasis and systemic growth. J Clin Invest 2005; 116:101-14. [PMID: 16374520 PMCID: PMC1319221 DOI: 10.1172/jci25735] [Citation(s) in RCA: 153] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2005] [Accepted: 10/25/2005] [Indexed: 02/06/2023] Open
Abstract
Insulin receptor substrates, including Irs1 and Irs2, integrate insulin and IGF receptor signals with heterologous pathways to coordinate growth and metabolism. Since Irs2 is thought to be especially important in hepatic nutrient homeostasis, we deleted Irs2 [corrected] from hepatocytes of WT mice (called LKO) or genetically insulin-resistant Irs1-/- mice (called LKO::Irs1-/-). Viable LKO::Irs1-/- mice were 70% smaller than WT or LKO mice, and 40% smaller than Irs1-/- mice. Hepatic insulin receptors were functional in all the mice, but insulin signaling via the Akt-FoxO1 pathway was reduced in Irs1-/- and LKO liver, and undetected in LKO::Irs1-/- liver; however, Gsk3beta phosphorylation (Ser9) and hepatic glycogen stores were nearly normal in all of the mice. LKO and Irs1-/- mice developed insulin resistance and glucose intolerance that never progressed to diabetes, whereas LKO::Irs1-/- mice developed hyperglycemia and hyperinsulinemia immediately after birth. Regardless, few hepatic genes changed expression significantly in Irs1-/- or LKO mice, whereas hundreds of genes changed in LKO::Irs1-/- mice--including elevated levels of Pck1, G6pc, Ppargc1, Pparg, and Igfbp1. Thus, signals delivered by Irs1 or Irs2 regulate hepatic gene expression that coordinates glucose homeostasis and systemic growth.
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Affiliation(s)
- Xiaocheng Dong
- Howard Hughes Medical Institute, Division of Endocrinology, Children's Hospital Boston, Harvard Medical School, Boston, Massachusetts 02115, USA
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50
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Nakagawa Y, Shimano H, Yoshikawa T, Ide T, Tamura M, Furusawa M, Yamamoto T, Inoue N, Matsuzaka T, Takahashi A, Hasty AH, Suzuki H, Sone H, Toyoshima H, Yahagi N, Yamada N. TFE3 transcriptionally activates hepatic IRS-2, participates in insulin signaling and ameliorates diabetes. Nat Med 2005; 12:107-13. [PMID: 16327801 DOI: 10.1038/nm1334] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2005] [Accepted: 10/27/2005] [Indexed: 11/08/2022]
Abstract
Using an expression cloning strategy, we have identified TFE3, a basic helix-loop-helix protein, as a transactivator of metabolic genes that are regulated through an E-box in their promoters. Adenovirus-mediated expression of TFE3 in hepatocytes in culture and in vivo strongly activated expression of IRS-2 and Akt and enhanced phosphorylation of insulin-signaling kinases such as Akt, glycogen synthase kinase 3beta and p70S6 kinase. TFE3 also induced hexokinase II (HK2) and insulin-induced gene 1 (INSIG1). These changes led to metabolic consequences, such as activation of glycogen and protein synthesis, but not lipogenesis, in liver. Collectively, plasma glucose levels were markedly reduced both in normal mice and in different mouse models of diabetes, including streptozotocin-treated, db/db and KK mice. Promoter analyses showed that IRS2, HK2 and INSIG1 are direct targets of TFE3. Activation of insulin signals in both insulin depletion and resistance suggests that TFE3 could be a therapeutic target for diabetes.
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MESH Headings
- Adenoviridae/genetics
- Adenoviridae/metabolism
- Animals
- Basic Helix-Loop-Helix Leucine Zipper Transcription Factors/metabolism
- Basic Helix-Loop-Helix Leucine Zipper Transcription Factors/physiology
- Blood Glucose/metabolism
- Blotting, Northern
- Cells, Cultured
- Chromatin Immunoprecipitation
- Cloning, Molecular
- Diabetes Mellitus/therapy
- Diabetes Mellitus, Experimental
- Dose-Response Relationship, Drug
- Glycogen/metabolism
- Glycogen Synthase Kinase 3/metabolism
- Glycogen Synthase Kinase 3 beta
- Green Fluorescent Proteins/metabolism
- Hepatocytes/metabolism
- Hexokinase/metabolism
- Humans
- Immunoblotting
- Immunoprecipitation
- Insulin/metabolism
- Insulin Receptor Substrate Proteins
- Intracellular Signaling Peptides and Proteins
- Male
- Membrane Proteins/metabolism
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Models, Biological
- Phosphoproteins/metabolism
- Phosphorylation
- Plasmids/metabolism
- Promoter Regions, Genetic
- Protein Structure, Tertiary
- Proto-Oncogene Proteins c-akt/metabolism
- Rats
- Ribosomal Protein S6 Kinases, 70-kDa/metabolism
- Signal Transduction
- Streptozocin/pharmacology
- Time Factors
- Transcriptional Activation
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Affiliation(s)
- Yoshimi Nakagawa
- Department of Internal Medicine, Metabolism and Endocrinology, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, Japan, 305-8575
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