Insulin stimulates glucose uptake in muscle by mobilizing intracellular GLUT4 storage vesicles (GSVs), which fuse at the cell surface and insert GLUT4 glucose transporters into the sarcolemma. The differential targeting of GLUT4 in basal and insulin-stimulated cells determines insulin responsiveness. Insulin resistance results from impaired GSV regulation, and contributes to the pathogenesis of the metabolic syndrome and type 2 diabetes. Defects in both insulin signaling and vesicle trafficking may contribute to impaired GSV regulation. Signaling defects have been well studied, but trafficking defects are not characterized. Recent data suggest that GLUT4 trafficking defects may be an important contributor to insulin resistance in muscle. However, even normal GSV trafficking pathways are poorly defined. This proposal builds on recent work that, for the first time, defines a pool of insulin-regulated GSVs in molecular terms. These vesicles are retained intracellularly by TUG, which links GSVs to the Golgi matrix in unstimulated cells. Insulin causes TUG cleavage to release GSVs and to insert GLUT4 at the plasma membrane. Although GSV trafficking is controlled by insulin at multiple steps, data suggest that the TUG pathway is a major site of regulation, which is compromised in diet- induced insulin resistance in mice. Moreover, GSVs contain proteins other than GLUT4, notably IRAP, which may mediate distinct physiologic actions to control vascular tone and water homeostasis. Thus, impaired GSV trafficking may result not only in insulin resistance (with respect to glucose uptake) but also contribute to other abnormal physiology. Here, we propose to test the contribution of the TUG pathway in muscle to glucose homeostasis and to other aspects of physiology. Using transgenic mice, Aim 1 will test effects of disrupting TUG action in muscle on glucose uptake and turnover, energy expenditure, and other metabolic endpoints.
Aim 2 will study mice rendered insulin-resistant by a high-fat diet, and elucidate whether the trafficking and/or signaling defects that contribute to insulin resistance are bypassed by TUG disruption.
Aim 3 will study how disruption of TUG action affects water homeostasis and blood pressure. It is anticipated that, together, these studies will provide fundamental new insights that are highly significant for understanding glucose homeostasis, insulin resistance, and the metabolic syndrome. Public Health Significance: Type 2 diabetes and pre-diabetes are an enormous public health burden, estimated to affect >40% of adults in the United States. These metabolic abnormalities frequently occur as part of a constellation of abnormalities, including high blood pressure, which leads to substantial morbidity and mortality. The research proposed here will investigate how these abnormalities occur, and whether distinct features of this metabolic syndrome may have a shared pathophysiologic basis.

Public Health Relevance

This project will study how glucose metabolism is regulated in muscle, how this regulation becomes defective during the development of diabetes, and how the mechanisms that control glucose metabolism may also contribute to the regulation of blood pressure. The results will shed light on how insulin resistance develops and leads to type 2 diabetes and the metabolic syndrome, and will have importance for the prevention and treatment of diabetes and its complications.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK092661-02
Application #
8518317
Study Section
Special Emphasis Panel (ZRG1-EMNR-E (03))
Program Officer
Haft, Carol R
Project Start
2012-08-01
Project End
2014-07-31
Budget Start
2013-08-01
Budget End
2014-07-31
Support Year
2
Fiscal Year
2013
Total Cost
$241,009
Indirect Cost
$96,259
Name
Yale University
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
043207562
City
New Haven
State
CT
Country
United States
Zip Code
06520
Habtemichael, Estifanos N; Li, Don T; Alcázar-Román, Abel et al. (2018) Usp25m protease regulates ubiquitin-like processing of TUG proteins to control GLUT4 glucose transporter translocation in adipocytes. J Biol Chem 293:10466-10486
Xu, Yingke; Toomre, Derek K; Bogan, Jonathan S et al. (2017) Excess cholesterol inhibits glucose-stimulated fusion pore dynamics in insulin exocytosis. J Cell Mol Med 21:2950-2962
Quan, Nanhu; Sun, Wanqing; Wang, Lin et al. (2017) Sestrin2 prevents age-related intolerance to ischemia and reperfusion injury by modulating substrate metabolism. FASEB J 31:4153-4167
Tol, Marc J; Ottenhoff, Roelof; van Eijk, Marco et al. (2016) A PPAR?-Bnip3 Axis Couples Adipose Mitochondrial Fusion-Fission Balance to Systemic Insulin Sensitivity. Diabetes 65:2591-605
Xu, Yingke; Nan, Di; Fan, Jiannan et al. (2016) Optogenetic activation reveals distinct roles of PIP3 and Akt in adipocyte insulin action. J Cell Sci 129:2085-95
Habtemichael, Estifanos N; Alcázar-Román, Abel; Rubin, Bradley R et al. (2015) Coordinated Regulation of Vasopressin Inactivation and Glucose Uptake by Action of TUG Protein in Muscle. J Biol Chem 290:14454-61
Castorena, Carlos M; Arias, Edward B; Sharma, Naveen et al. (2015) Fiber type effects on contraction-stimulated glucose uptake and GLUT4 abundance in single fibers from rat skeletal muscle. Am J Physiol Endocrinol Metab 308:E223-30
Belman, Jonathan P; Bian, Rachel R; Habtemichael, Estifanos N et al. (2015) Acetylation of TUG protein promotes the accumulation of GLUT4 glucose transporters in an insulin-responsive intracellular compartment. J Biol Chem 290:4447-63
Bogan, Jonathan S (2014) Endocytic cycling of glucose transporters and insulin resistance due to immunosuppressive agents. J Clin Endocrinol Metab 99:3622-4
Cantley, Jennifer L; Vatner, Daniel F; Galbo, Thomas et al. (2014) Targeting steroid receptor coactivator 1 with antisense oligonucleotides increases insulin-stimulated skeletal muscle glucose uptake in chow-fed and high-fat-fed male rats. Am J Physiol Endocrinol Metab 307:E773-83

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