Source: UNIVERSITY OF CALIFORNIA, DAVIS submitted to
UNCOVERING THE MOLECULAR BASIS OF OBESITY AND TYPE 2 DIABETES USING ADVANCED GENETIC AND CELLULAR APPROACHES
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
REVISED
Funding Source
Reporting Frequency
Annual
Accession No.
0215673
Grant No.
(N/A)
Project No.
CA-D-NTR-7836-H
Proposal No.
(N/A)
Multistate No.
(N/A)
Program Code
(N/A)
Project Start Date
Oct 1, 2012
Project End Date
Sep 30, 2017
Grant Year
(N/A)
Project Director
Haj, F. G.
Recipient Organization
UNIVERSITY OF CALIFORNIA, DAVIS
410 MRAK HALL
DAVIS,CA 95616-8671
Performing Department
Nutrition
Non Technical Summary
Our research implicates enzymes called protein tyrosine phosphatases in the regulation of glucose metabolism and energy balance, and further establishes these enzymes as potential therapeutic targets for metabolic regulation. In addition, our research has made a significant impact on the field and has been the subject of several reviews and commentaries with a number of our papers having excellent citation record.
Animal Health Component
50%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
3053840101020%
3053840102020%
3057010103020%
3057010104020%
3057010106020%
Goals / Objectives
The objective of the research is to investigate the molecular basis of obesity and diabetes with the ultimate goal of developing therapies for these diseases. We are interested in the function of tyrosine phosphorylation in cellular signaling and how dysregulation of these pathways leads to disease. Gene knockout approach. To determine the physiological role of phosphatases in vivo we use the powerful gene knockout (KO) Cre-LoxP approach to generate mice with whole-body and/or tissue-specific deletion. Briefly, mice are generated with the cDNA encoding the PTP of interest flanked with Lox-P sites. This allows excision of the phosphatase in the presence of an enzyme, Cre recombinase (Cre) that binds to these sites. Whole body or tissue-specific deletion could be achieved by using the appropriate Cre transgenic mice for breeding. We addressed the physiological role of hepatic Shp2 using liver specific deletion approach (Matsuo etal., JBC, 2010; Nagata etal., Endocrinology, 2012). We demonstrated that liver Shp2 KO mice gained less weight and exhibited increased energy expenditure compared with control mice. In addition, hepatic Shp2 deficiency led to decreased liver steatosis, enhanced insulin-induced suppression of hepatic glucose production, and prevented the development of insulin resistance following high fat feeding. Our studies identified hepatic Shp2 as a novel regulator of systemic energy balance under conditions of high fat feeding. To investigate the role of PTP1B in individual insulin-responsive tissues, we generated transgenic mice expressing PTP1B in muscle or liver. In additional studies, we show that PTP1B and the related TCPTP play an important role in regulating endoplasmic reticulum stress (Bettaieb etal., JBC, 2011; Bettaieb etal., PLoS One, 2012). Cellular approaches. Animal studies are complemented by biochemical and cellular imaging approaches. We demonstrate that endoplasmic reticulum-anchored PTP1B plays a dynamic role in signaling at regions of cell-cell contact and identify plasma membrane proximal sub-regions of the ER as important sites for regulating signaling (Nievergall etal, Journal of Cell Biology, 2010; Haj etal, PLoS One, 2012).
Project Methods
The objective of the research is to investigate the molecular basis of obesity and diabetes with the ultimate goal of developing therapies for these diseases. We are interested in the function of tyrosine phosphorylation in cellular signaling and how dysregulation of these pathways leads to disease. To that end, we utilize a number of multidisciplinary approaches. We use gene knockout to generate genetically-engineered mice with deletion of the phosphatase of interest. This enables us to determine the physiological role of phosphatases in energy balance and metabolism. In addition, we utilize advanced quantitative cellular imaging to dissect the spatial-temporal interactions of PTPs with their partners at the cellular level. These multidisciplinary approaches allow the efficient assessment of metabolic regulation by PTPs and should aid in identifying targets for therapeutic intervention. The findings from our research are constantly being shared and disseminated to communities of interest through variety of mechanisms. I constantly discuss ongoing research efforts and new findings with Cooperative Extension Specialists who are members of the Department of Nutrition. They in turn communicate this to the public. In addition, I disseminate these findings myself by giving seminars and presentations to members and volunteers of the Sacramento/Valley American Diabetes Association. In addition, I presented our novel findings in a number of national and international seminars in 2011 listed below: 9th International Conference on Protein Phosphatases, Tokyo, Japan; School of Medicine, University of Tokyo, Tokyo, Japan; Department of Microbiology, Yokohama City University, Yokohama, Japan; EMBO conference on protein phosphatases, Vienna, Austria; Department of Biology, University of Copenhagen, Copenhagen, Denmark; Frontiers of Science, Engineering and Medicine Symposium, Kuwait Institute for Scientific Research, Kuwait City, Kuwait; Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan; Taiwan Society for Biochemistry and Molecular Biology, Taipei, Taiwan; Department of Biological Sciences, National University of Singapore, Singapore; Duke-National University of Singapore Graduate Medical School, Singapore; Division of Endocrinology, Diabetes and Metabolism, University of Miami, Miami, Florida; School of Medicine, University of Miami, Miami, Florida; Pre-Obesity Society Symposium, Orlando, Florida.

Progress 01/01/12 to 12/31/12

Outputs
OUTPUTS: Research findings from my laboratory and their translational relevance and implications are constantly and readily disseminated to California citizens through various outlets. Our research is supported in part by funds from the Center for Health and Nutrition Research (CHNR) hence our research focus and findings are updated on the CHNR website and communicated to relevant interested groups. In addition, our findings are described and constantly updated on the Nutrition Department and the Haj lab websites. More recently, I worked with a student of mine (Mitra Jamshidin), who contributes to a Blog about healthy living, to write a section regarding new advances on the contribution of brown adipose tissue to metabolic regulation and targeting this organ to prevent/treat obesity. Furthermore, I actively work with different charitable organizations in Sacramento and North California to raise awareness about metabolic diseases and update lay audiences on recent research advances, namely Juvenile Diabetes Research Foundation (for type 1 diabetes) and American Diabetes Association (for type 2 diabetes). In addition to giving presentations and seminars at these organizations, I served as Board Member for the Sacramento Diabetes Association. Major tasks included organizing fund raising event and planning a yearly event during August that is dedicated to the public. We provided the attendee of that event with free tests of blood glucose concentrations and informed them of the best approaches to prevent and treat obesity and diabetes including life style changes and nutritional interventions. Finally, studies from my laboratory identified phosphatases as targets for the treatment of obesity and type 2 diabetes and a number of companies are pursuing the generation of PTP-selective inhibitors (some of which are at already stage 2 clinical trials). This was covered in a TV documentary by a local station (KVIE) and the interview was posted on the Haj lab website. As a result of this, and other presentations, I occasionally get emails from concerned citizens who are suffering from obesity or Type 2 diabetes. I respond promptly to their questions and inform them about the potential of these inhibitors and the timeline for their development. I presented our novel findings in a number of national and international seminars: 1- Cancer Center, University of California Davis, Sacramento, CA 2- Department of Orthopedics, University of California Davis, Sacramento, CA 3- Protein phosphatases conference, Silvertree, CO 4- Obesity and weight management conference, Philadelphia, PA 5- Phosphatases in human disease, Melbourne, Australia 6- Garvan Institute, Sydney, Australia 7- Royal Society physiology conference, London, UK 8- International phosphatase conference, Tokyo, Japan 9- Department of Disease Control and Homeostasis, Kanazawa University, Kanazawa, Japan 10- Department of Disease Control, National Center for Global Health and Medicine, Tokyo, Japan PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
The objective of research in the laboratory is to investigate the molecular basis of obesity and diabetes with the ultimate goal of developing therapies for these chronic diseases. We are interested in the role of tyrosyl phosphorylation in cellular signaling and how dysregulation of this pathway leads to disease. We addressed the physiological role of hepatic Shp2 using liver-specific deletion (Matsuo etal., JBC and Nagata etal., Endocrinology). We demonstrated that liver-specific Shp2 KO mice gained less weight and exhibited increased energy expenditure compared with control mice. In addition, hepatic Shp2 deficiency led to decreased liver steatosis, enhanced insulin-induced suppression of hepatic glucose production, and prevented the development of insulin resistance following high fat feeding. Collectively, these studies identified hepatic Shp2 as a novel regulator of systemic energy balance under conditions of high fat feeding. The pancreas is a major regulator of insulin and glucose homeostasis so we determined the role of PTP1B in pancreas function. We generated mice with pancreas-specific PTP1B deletion and showed significant attenuation of insulin secretion upon PTP1B deletion. We uncovered a novel mechanism whereby PTP1B regulates pancreatic beta cell-cell communication through modifying Eph kinase phosphorylation. In addition, we demonstrated that PTP1B plays an important role in regulating endoplasmic reticulum stress in the pancreas (Bettaieb etal., JBC). Further studies using combined biochemical and mass spectroscopy approaches identified new physiological targets for PTP1B including PERK (Bettaieb etal., PLoS One). In collaboration with Bruce Hammock's laboratory (UCD) we demonstrated that soluble epoxide hydrolase plays an important role in regulating systemic glucose homeostasis (Luria etal., PNAS) and rapidly reduces pain-related behavior (Inceoglu etal., PNAS). Metabolic studies with Peter Havel's laboratory (UCD) revealed that leptin administration normalized fasting plasma glucose in obese type 2 diabetic UCD-T2DM rats (Cummings etal., PNAS), and identified molecular mechanisms that mediate the beneficial metabolic effects of ileal interposition surgery (Cummings etal., Endocrinology). In addition, with Patricia Oteiza's laboratory (UCD) we demonstrated that (-)-Epicatechin prevents TNFalpha-induced activation of signaling cascades leading to inflammation and insulin resistance (Prieto etal., ABB). Cellular approaches. We utilize biochemical and quantitative cellular imaging approaches to dissect the interaction of PTPs with their substrates. We showed that endoplasmic reticulum (ER)-anchored PTP1B plays a dynamic role in regulating signaling at regions of cell-cell contact and identify plasma membrane proximal sub-regions of the ER as important sites for regulating cellular signaling (Haj etal., PLoS One). Collectively, our research implicates tyrosyl phosphorylation in the regulation of glucose metabolism and energy balance in vivo, and further establishes this signaling mechanism as potential therapeutic target for metabolic regulation.

Publications

  • Marcela Vazquez-Prieto, Ahmed Bettaieb, Fawaz Haj, Cesar Fraga, Patricia Oteiza. (-)-Epicatechin prevents TNFalpha-induced activation of signaling cascades involved in inflammation and insulin sensitivity in 3T3 adipocytes. Archives of Biochemistry and Biophysics, March 8. 2012
  • Ahmed Bettaieb, Kosuke Matsuo, Izumi Matsuo, Shuo Wang, Ramzi Melhem, Antonis Koromilas and Fawaz Haj . Protein tyrosine phosphatase 1B deficiency potentiates PERK/eIF2alphasignaling in brown adipocytes. PLoS One. 2012;7(4):e34412 2012
  • Naoto Nagata, Kosuke Matsuo, Ahmed Bettaieb, Jesse Bakke, Izumi Matsuo, James Graham, Alexey Tomilov, Natalia Tomilova, Yannan Xi, Siming Liu, Susan Gray, Dae Young Jung, Jon Ramsey, Jason Kim, Gino Cortopassi, Peter Havel and Fawaz Haj . Hepatic Src homology phosphatase 2 regulates energy balance in mice. Endocrinology, Jul;153(7):3158-69 2012
  • Fawaz Haj , Ola Sabet, Ali Kinkhabwala, Sabine Wimmer, Vassilis Roukos, Claude Antony, Benajmin Neel and Philippe Bastiaens . Regulation of signaling at regions of cell-cell contact by endoplasmic reticulum-bound protein-tyrosine phosphatase 1B. PLoS One, 7(5):e36633 2012
  • Bethany Cummings, Ahmed Bettaieb, James Graham, Kimber Stanhope, Mark Kowala, Fawaz Haj, Michael Chouinard and Peter Havel. Vertical Sleeve Gastrectomy Improves Glucose and Lipid Metabolism and Delays Diabetes Onset in UCD-T2DM Rats. Endocrinology, Aug;153(8):3620-32. 2012
  • Bora Inceoglu, Karen Wagner, Jun Yang, Ahmed Bettaieb*, Nils Schebb, Sung Hee Hwang, Christophe Morisseau, Fawaz Haj and Bruce Hammock . Acute augmentation of epoxygenated fatty acid levels rapidly reduces pain-related behavior in a rat model of type I diabetes. Proceedings of the National Academy of Sciences, Jul 10;109(28):11390-5. 2012
  • Bethany Cummings, Ahmed Bettaieb, James Graham, Kimber Stanhope, Cecilia Giulivi, Frederik Hansen, Jacob Jelsing, Niels Vrang, Mark Kowala, Michael Chouinard, Fawaz Haj, and Peter Havel. Bile acid mediated decreases of endoplasmic reticulum stress: a novel contributor to the metabolic benefits of ileal interposition surgery. Disease Molecular Mechanisms. 2012


Progress 01/01/11 to 12/31/11

Outputs
OUTPUTS: The main objective of our research is to uncover the molecular basis of obesity and type 2 diabetes. These diseases are reaching epidemic proportion in California and the United States. Studies from our group and others, led to the identification of PTPs as potential targets for the treatment of these diseases. Our research efforts are already leading to the development of new knowledge and technologies that will ultimately resolve significant health related problems and will be beneficial for residents in California. Our findings are constantly being shared and disseminated to communities of interest through variety of mechanisms. I constantly discuss ongoing research efforts and new findings with Cooperative Extension Specialists who are members of the Department of Nutrition. They in turn communicate this to the public. In addition, I disseminate these findings myself by giving seminars and presentations to members and volunteers of the American Diabetes Association. In addition, I presented our novel findings in a number of national and international seminars: (1) 9th International Conference on Protein Phosphatases, Tokyo, Japan (2) School of Medicine, University of Tokyo, Tokyo, Japan (3) Department of Microbiology, Yokohama City University, Yokohama, Japan (4) EMBO conference on protein phosphatases, Vienna, Austria (5) Department of Biology, University of Copenhagen, Copenhagen, Denmark (6) Frontiers of Science, Engineering and Medicine Symposium, Kuwait Institute for Scientific Research, Kuwait City, Kuwait (7) Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan (8) Taiwan Society for Biochemistry and Molecular Biology, Taipei, Taiwan (9) Department of Biological Sciences, National University of Singapore, Singapore (10) Duke-National University of Singapore Graduate Medical School, Singapore (11) Division of Endocrinology, Diabetes and Metabolism, University of Miami, Miami, Florida (12) School of Medicine, University of Miami, Miami, Florida (13) Pre-Obesity Society Symposium, Orlando, Florida PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
Objective: investigate molecular basis of obesity & diabetes, ultimate goal of developing therapies. We are interested in the function of tyrosyl phosphorylation in cellular signaling(CS) & how dysregulation of pathways leads to disease, & use a number of multidisciplinary approaches. 1)Gene knockout approach. Research aims to dissect the metabolic function of three PTPs: protein-tyrosine phosphatase 1B (PTP1B), T cell protein-tyrosine phosphatase (TCPTP) and Src homology phosphatase 2 (Shp2). To determine the physiological role of these PTPs in vivo we use the powerful gene knockout(KO) Cre-LoxP approach to generate mice w/ whole-body &/or tissue-specific deletion. Briefly mice are generated w/ the cDNA encoding the PTP of interest flanked w/ Lox-P sites. This allows excision of phosphatase in the presence of an enzyme, Cre recombinase (Cre) that binds to these sites. Whole body or tissue-specific deletion could be achieved by using the appropriate Cre transgenic mice for breeding. We addressed the physiological role of hepatic Shp2 using liver specific deletion approach. Demonstrated liver Shp2 KO mice gained less weight & exhibited increased energy expenditure compared w/ control mice. Hepatic Shp2 deficiency led to decreased liver steatosis, enhanced insulin-induced suppression of hepatic glucose production & prevented development of insulin resistance following high fat feeding. Our studies ID'd hepatic Shp2 as a novel regulator of systemic energy balance under high fat feeding condition. Determined role of PTP1B in pancreas function, generated mice w/ pancreas-specific PTP1B deletion & showed significant attenuation of insulin secretion upon PTP1B deletion. Uncovered a novel mechanism whereby PTP1B regulates pancreatic beta cell-cell communication through modifying Eph kinase phosphorylation. Demonstrated PTP1B plays important role in regulating endoplasmic reticulum (ER) stress. Combined biochemical & mass spectroscopy approaches ID'd new physiological targets for PTP1B including pyruvate kinase M2. Demonstrated metabolic actions of PTP1B & its regulation of energy balance in vivo are mediated at least in part through PKM2. W/the Hammock lab, demonstrated that soluble epoxide hydrolase plays a role in regulating systemic glucose homeostasis & rapidly reduces pain-related behavior. Studies w/ Havel lab revealed leptin administration normalized fasting plasma glucose in obese type2 diabetic UCD-T2DM rats & ID'd molecular mechanisms that mediate beneficial metabolic effects of ileal interposition surgery. W/the Oteiza lab, demonstrated that (-)-Epicatechin prevents TNFalpha-induced activation of signaling cascades leading to inflammation & insulin resistance. 2)Cellular approaches (biochemical and cellular imaging.) We showed that (ER)-anchored PTP1B plays a dynamic role in regulating signaling at regions of cell-cell contact & identify plasma membrane proximal sub-regions of ER as important sites for regulating CS. Collective research implicates tyrosyl phosphorylation in the regulation of glucose metabolism & energy balance in vivo & further establishes this signaling mechanism a potential therapeutic target for metabolic regulation.

Publications

  • Ayala Luria, Ahmed Bettaieb, Yannan Xi, Guang-Jong Shieh, Hsin-Chen Liu, Hiromi Inoue, Hsing-Ju Tsai, John Imig, Fawaz Haj and Bruce Hammock. Soluble epoxide hydrolase deficiency alters pancreatic islet size and improves glucose homeostasis in a model of insulin resistance. Proceedings of the National Academy of Sciences, May 31;108(22):9038-43 2011
  • Bethany Cummings, Ahmed Bettaieb, James Graham, Kimber Stanhope, Riva Dill, Gregory Morton, Fawaz Haj and Peter Havel . Subcutaneous administration of leptin normalizes fasting plasma glucose in obese type 2 diabetic UCD-T2DM rats. Proceedings of the National Academy of Sciences, August 30;108(35):14670-5. 2011
  • Ahmed Bettaieb, Kosuke Matsuo, Shuo Wang, Izumi Matsuo, Ramzi Melhem, Antonis Koromilas and Fawaz Haj . Protein tyrosine phosphatase 1B deficiency potentiates brown adipocyte response to endoplasmic reticulum stress. PLoS One, 2012. In Press
  • Marcela Vazquez Prieto, Ahmed Bettaieb, Fawaz Haj, Cesar Fraga, Patricia Oteiza. (-)-Epicatechin prevents TNFalpha-induced activation of signaling cascades leading to inflammation and insulin resistance in 3T3 adipocytes. Submitted to Archives of Biochemistry and Biophysics, 2012. In Press


Progress 01/01/10 to 12/31/10

Outputs
OUTPUTS: The main objective of our research is to uncover the molecular basis of obesity and type 2 diabetes. These diseases are reaching epidemic proportion in California and the United States. Studies from our group and others, led to the identification of PTPs as targets for the treatment of these diseases. Our research efforts are already leading to the development of new knowledge and technologies that will ultimately resolve significant health related problems and will be beneficial for residents in California. Our research using state-of-the-art gene knockout technology showed that the inhibition of a single molecule (protein-tyrosine phosphates, Shp2) in the liver leads to improved insulin sensitivity and energy balance. These findings have direct implications for the treatment of obesity and type 2 diabetes. These findings are constantly being shared and disseminated to communities of interest through variety of mechanisms. I constantly discuss ongoing research efforts and new findings with Cooperative Extension Specialists who are members of the Department of Nutrition. They in turn communicate this to the public. In addition, I disseminate these findings myself by giving seminars and presentations to members and volunteers of the Sacaramento/Valley American Diabetes Association. In addition, I presented our novel findings in a number of national and international seminars listed below: Department of Oncology, Lady Davis Institute for Research, McGill University, Montreal, Canada Meeting on Shc and aging, Les Diablerets, Switzerland Department of Growth Control, FMI for Biomedical Research, Basel, Switzerland Protein Phosphatase Conference, Steamboat, CO Program in Integrative Cell Signaling and Neurobiology of Metabolism, Yale University, CT PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
Objective - The SH2 domain-containing protein-tyrosine phosphatase Shp2 has been implicated in a variety of growth factor signaling pathways, but its physiological function in some peripheral insulin-responsive tissues remains unknown. Materials/Methods - To address the metabolic role of Shp2 in adipose tissue, we generated mice with adipose-specific Shp2 deletion using Adiponectin (Adipoq)-Cre transgenic mice. We then analyzed insulin sensitivity, glucose tolerance and body mass in adipose-specific Shp2-deficient and control mice on regular chow and high fat diet (HFD). Results - Shp2 protein expression was elevated in various adipose depots of control mice on a HFD compared with those on chow. Adipoq-Cre mice enabled efficient and specific deletion of Shp2 in adipose tissue. However, adipose Shp2 deletion did not significantly alter body mass in mice on chow or a HFD. In addition, mice with adipose Shp2 deletion exhibited comparable insulin sensitivity and glucose tolerance compared with controls. Consistent with this observation, basal and insulin-stimulated Erk and Akt phosphorylation were comparable in Shp2-deficient and control mice. Conclusions - Our findings indicate that adipose-specific Shp2 deletion does not significantly alter systemic insulin sensitivity and glucose homeostasis. Studies on the role of endoplasmic reticulum bound phosphatases in stress signaling: Protein-tyrosine phosphatase 1B (PTP1B) and T cell protein-tyrosine phosphatase (TCPTP) are closely related intracellular phosphatases implicated in the control of glucose homeostasis. PTP1B and TCPTP can function coordinately to regulate protein tyrosine kinase signaling and PTP1B has been implicated previously in the regulation of endoplasmic reticulum (ER) stress. In this study we assessed the roles of PTP1B and TCPTP in regulating ER stress in the endocrine pancreas. PTP1B and TCPTP expression was determined in pancreata from chow and high fat fed mice and the impact of PTP1B and TCPTP over- or under-expression on palmitate- or tunicamycin-induced ER stress signaling assessed in MIN6 insulinoma beta cells. PTP1B expression was increased and TCPTP expression decreased in pancreata of mice fed a high fat diet, as well as in MIN6 cells treated with palmitate. PTP1B over-expression or TCPTP knockdown in MIN6 cells mitigated palmitate- or tunicamycin-induced PERK/eIF2 alpha ER stress signaling, while PTP1B deficiency enhanced ER stress. Moreover, PTP1B deficiency increased ER stress-induced cell death while TCPTP deficiency protected MIN6 cells from ER stress-induced death. ER stress coincided with the inhibition of Src family kinases (SFKs) which was exacerbated by PTP1B over-expression and largely prevented by TCPTP knockdown. Pharmacological inhibition of SFKs ameliorated the protective effect of TCPTP deficiency on ER stress-induced cell death. These results demonstrate that PTP1B and TCPTP play non-redundant roles in modulating ER stress in pancreatic beta cells and suggest that changes in PTP1B and TCPTP expression may serve as an adaptive response for the mitigation of chronic ER stress.

Publications

  • Kosuke Matsuo, Mirela Delibegovic, Izumi Matsuo, Naoto Nagata, Siming Liu, Ahmed Bettaieb, Yannan Xi, Kazu Araki, Wentien Yang, Barbara Kahn, Benjamin Neel and Fawaz Haj (2010). Altered glucose homeostasis in mice with liver-specific deletion of Src Homology Phosphatase 2. Journal of Biological Chemistry. Dec 17, 285(51):39750-8.
  • Eva Nievergall, Peter Janes, Carolin Stegmayer, Mary Vail, Fawaz Haj, Shyh Wei Teng, Benajmin Neel, Philippe Bastiaens and Martin Lackman (2010). Protein-Tyrosine Phosphatase 1B regulates Eph receptor phosphorylation and traffic. Journal of Cell Biology. Dec 13; 191(6):1189-203.
  • Ahmed Bettaieb, Siming Liu, Yannan Xi, Naoto Nagata, Kosuke Matsuo, Izumi Matsuo, Samah Chahed, Jesse Bakke, Heike Keilhack, Tony Tiganis and Fawaz Haj . Differential regulation of endoplasmic reticulum stress by protein tyrosine phsophatase 1B and T cell protein tyrosine phosphatase. In press, Journal of Biological Chemistry. 2011
  • Kosuke Matsuo, Ahmed Bettaieb, Naoto Nagata, Izumi Matsuo and Fawaz Haj . Role of protein tyrosine phosphatase 1B in brown adipocyte differentiation. In press, PLoS One. 2011
  • Ahmed Bettaieb, Kosuke Matsuo, Izumi Matsuo and Fawaz Haj . Adipose-specific Src Homology Phosphatase 2 deficiency does not significantly alter systemic glucose homeostasis. In press, Metabolism. 2011


Progress 01/01/09 to 12/31/09

Outputs
OUTPUTS: The main objective of our research is to uncover the molecular basis of obesity and type 2 diabetes. These diseases are reaching epidemic proportion in California and the United States. Studies from our group and others, led to the identification of protein-tyrosine phosphatases (PTPs) as targets for the treatment of these diseases. Our research efforts are already leading to the development of new knowledge and technologies that will ultimately resolve significant health related problems and will be beneficial for residents in California. I continuously strive to inform the public of our discoveries and their relevance to prevention and treatment of disease. I was featured in a TV documentary by KVIE that aims to raise awareness for type 2 diabetes. In addition, I work closely with the American Diabetes Association and organize diabetes conferences (August 2009) for the public to raise awareness for diabetes and metabolic diseases. Moreover, some of our research involves studying the role of PTPs in breast cancer so I present our findings at American Cancer Society events and help to inform the public of this disease and aid in their fund raising efforts. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
Diabetes is one of the most prevalent metabolic diseases that is characterized by hyperinsulinemia, insulin resistance, and defect(s) in islet secretory function. Type 1 (insulin-dependent) diabetes is due to insulin deficiency following the autoimmune destruction of pancreatic beta-cells. Restoration of beta-cell function, the cure for type 1 diabetes, could be achieved through a thorough understanding of islet signaling, growth and cell-cell communication. Tyrosine phosphorylation plays a critical role in regulating signaling and is tightly controlled by the opposing actions of protein-tyrosine kinases and protein-tyrosine phosphatases (PTPs). We previously demonstrated a role for protein-tyrosine phosphatase 1B (PTP1B) in regulating beta-cell homeostasis and showed that PTP1B deficiency can partially compensate for beta-cell failure in insulin receptor substrate 2 Knockout (KO) mice. In addition, insulin signaling is suggested to play a role in beta-cell function and mass, thus it is important to understand the precise role of PTP1B (a regulator of insulin signaling) in islet function. Moreover, we recently showed the expression of PTP1B in primary islets and revealed that it is increased in mouse models with disrupted insulin signaling in beta-cells and abnormal glucose tolerance. Collectively, these studies indicate that PTP1B is a regulator of islet function but its precise role in pancreatic endocrine function remains to be fully elucidated. To conclusively assess the physiological role of PTP1B in pancreatic islets, we created pancreas-specific PTP1B knockouts (panc-PTP1BKO) using mice expressing Cre recombinase on the Pdx-1 promoter. This provides us with a unique tool to study the direct consequences of PTP1B loss in the endocrine pancreas. Equally important are the identification of the underlying molecular mechanisms and dissection of PTP1B interaction with its physiological substrates in pancreatic beta-cells. These studies provided novel insights into the physiological role of PTP1B in the pancreas and modulating islet function. Our research efforts will aid in generating surrogate cells for replacement cell therapy for type 1 diabetes and modulating insulin secretion for treatment of type 2 diabetes.

Publications

  • No publications reported this period


Progress 01/01/08 to 12/31/08

Outputs
OUTPUTS: The main objective of our research is to uncover the molecular basis of obesity and type 2 diabetes. These diseases are reaching epidemic proportion in California and the United States. Studies from our group and others, led to the identification of PTPs as targets for the treatment of these diseases. Our research efforts are already leading to the development of new knowledge and technologies that will ultimately resolve significant health related problems and will be beneficial for residents in California. Our research using state-of-the-art gene knockout technology showed that the inhibition of a single molecule (protein-tyrosine phosphates, Shp2) in the liver leads to improved insulin sensitivity and energy balance. These findings have direct implications for the treatment of obesity and type 2 diabetes. These findings are constantly being shared and disseminated to communities of interest through a variety of mechanisms. I constantly discuss ongoing research efforts and new findings with Cooperative Extension Specialists who are members of the Department of Nutrition. They in turn communicate this to the public. In addition, I disseminate these findings myself by giving seminars and presentations (workshops are planned for the future) to members and volunteers of the Sacaramento/Valley American Diabetes Association. In addition, these findings will be reported soon (April 10, 2009) in a TV documentary by KVIE to raise awareness to diabetes. I was actively involved on this documentary and they interviewed me and members of my research team at UC Davis. Furthermore, Dr. Lucia Kaiser and I will be present at the viewing of this documentary and will talk to those present about the implications of our findings. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
The role of hepatic protein-tyrosine phosphatase, Shp2 in the regulation of glucose homeostasis was addressed through its acute and chronic deletion using adenoviral and tissue-specific knockout (KO) approaches, respectively. Acute deletion was used in addition to standard tissue-specific Cre approach to test whether the immediate effects of Shp2 deletion are similar to those that occur after potential adaptations to absent Shp2 expression. Acute liver-specific Shp2 deletion was achieved through adenovirus-mediated injection of Shp2 fl/fl mice. Adenovirus expressing Cre recombinase (Ad-Cre) or LacZ (Ad-LacZ) were injected in the tail vein of male Shp2 fl/fl mice. While the Ad-LacZ administration did not result in alteration of Shp2 protein levels, Ad-Cre resulted in its reduction. The effects of hepatic Shp2 deletion on glucose homeostasis were determined using glucose tolerance tests (GTTs) and insulin tolerance tests (ITTs). These studies were performed on the same group of mice before and after virus injection (i.e. Shp2 deletion). This is particularly useful since it enables one to compare the response of the same mice before and after Shp2 deletion. These studies show that mice with hepatic Shp2 deletion are more responsive to insulin and have improved glucose tolerance. In addition, these studies were performed on two independent cohorts of mice with similar results. It is important to note that these mice did not exhibit significant weight differences indicating that the observed metabolic phenotype is independent of weight. Further dissection of the metabolic phenotype of these mice was achieved through assessing their fed and fasted metabolic variables such as glucose, insulin, free fatty acids and leptin. Mice with hepatic Shp2 deletion had significantly less insulin at the fed state with a similar trend in glucose and free fatty acids (although that did not reach statistical significance) consistent with the metabolic phenotype. Interestingly, these mice also exhibited significantly decreased fed leptin levels suggesting that hepatic Shp2 plays a role in leptin homeostasis. Metabolic changes in hepatic function caused by deletion of Shp2 were accompanied by alterations in insulin-regulated gene expression. Using RT-PCR we detected significant reduction in the gluconeogenic genes phosphoenolpyruvate carboxykinase (PEPCK) (the rate-limiting step in gluconeogenesis) and glucose-6-phosphatase (G6P). In addition, significant reduction was also detected in the lipogenic genes sterol regulatory element binding protein-1c (SREBP-1c) and fatty acid synthase (FAS). These findings are consistent with the increased insulin sensitivity of these mice. The insulin signaling pathway underlying the phenotypic changes in mice with hepatic Shp2 deletion was investigated. Basal and insulin-stimulated tyrosine phosphorylation of IRS1 and IRS2 was increased in mice with liver-specific Shp2 deletion. Moreover, basal IRS1- and IRS2-associated PI3 kinase activity was elevated after Shp2 deletion. Consistent with these observations, downstream signaling was increased after Shp2 deletion.

Publications

  • Improved Insulin Sensitivity in Mice with Liver-Specific Deletion of Src Homology Phosphatase 2. Kosuke Matsuo, Mirela Delibegovic, Izumi Matsuo, Siming Liu, Kazushi Araki, Wentian Yang, Barbara Kahn, Benjamin Neel, and Fawaz Haj*. Submitted to Journal of Biological Chemistry. 2009 (Submitted)
  • Hepatic Src Homology Phosphatase 2 Regulates Energy Balance and Metabolism. Kosuke Matsuo, Izumi Matsuo, Siming Liu, Heike Keilhack and Fawaz Haj*. In preparation for submission to Diabetes. 2009 (In Preparation)