Insulin resistance is a characteristic feature of Type II diabetes, of uncontrolled Type I diabetes, and is also associated with a number of heterogenous conditions. The major objective of this study is to elucidate biochemical mechanisms which may contribute to insulin resistance in insulinopenic (Type I) diabetes, using rats with streptozotin (STZ)- induced diabetes as a model. l.) Several lines of evidence suggest that processing (N-glycosylation) of the insulin receptor is altered in rats with severe STZ-diabetes, suggesting that processing of other proteins may also be affected. Possible post-translational modification of glucose transporters (GLUT) from liver, muscle and adipose tissue of STZ-diabetic and control rats will be examined by 2-D gel electrophoresis (2-D SDS- PAGE) followed by immunoblotting with site-specific antibodies; with or without antecedent glycosidase treatment. Since 2-D SDS-PAGE reveals several processing isoforms of specific GLUT, cell fractionation studies will test the hypothesis that certain processing isoforms of GLUT4 are preferentially translocated to the plasma membrane in response to insulin. N-linked glycosylation and Golgi processing of a model peptide 125-I-N- octanoyl-Asp-Thyr-Thr-N (OTP) will be studied in hepatocytes of control and diabetic rats, to assess a defect in ER or Golgi processing and/or vesicular transport associated with diabetes. 2.) Increased flux through the hexosamine synthetic pathway has been proposed as a mechanisms of glucose-induced, glucose transport insulin resistance. Products of this pathway.may alter the glycosylation/processing of glycoproteins. The rate limiting enzyme for glucose entry into this pathway is glutamine: fructose-6-P amido transferase (GFAT). The regulation of GFAT, products of the pathway and the biochemical mechanisms by which these products may cause insulin resistance will be studied in tissue culture systems and in isolated muscles. The methods developed in these studies will then be applied in vivo, to evaluate the possible role of this pathway in glucose- induced insulin resistance in muscle and adipose tissue of intact animals, i.e. control rats, controls infused with glucose and diabetic rats. In a pilot study, possible alterations in this pathway will be examined in a murine model of Type II diabetes.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK002001-37
Application #
2133637
Study Section
Metabolism Study Section (MET)
Project Start
1978-05-01
Project End
1997-12-31
Budget Start
1995-01-01
Budget End
1995-12-31
Support Year
37
Fiscal Year
1995
Total Cost
Indirect Cost
Name
Medical University of South Carolina
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
183710748
City
Charleston
State
SC
Country
United States
Zip Code
29425
Robinson, Katherine A; Hegyi, Krisztina; Hannun, Yusuf A et al. (2014) Go-6976 reverses hyperglycemia-induced insulin resistance independently of cPKC inhibition in adipocytes. PLoS One 9:e108963
Robinson, Katherine A; Brock, Jonathan W; Buse, Maria G (2013) Posttranslational regulation of thioredoxin-interacting protein. J Mol Endocrinol 50:59-71
Klein, Amanda L; Berkaw, Mary N; Buse, Maria G et al. (2009) O-linked N-acetylglucosamine modification of insulin receptor substrate-1 occurs in close proximity to multiple SH2 domain binding motifs. Mol Cell Proteomics 8:2733-45
Robinson, Katherine A; Buse, Maria G (2008) Mechanisms of high-glucose/insulin-mediated desensitization of acute insulin-stimulated glucose transport and Akt activation. Am J Physiol Endocrinol Metab 294:E870-81
Robinson, Katherine A; Ball, Lauren E; Buse, Maria G (2007) Reduction of O-GlcNAc protein modification does not prevent insulin resistance in 3T3-L1 adipocytes. Am J Physiol Endocrinol Metab 292:E884-90
Ball, Lauren E; Berkaw, Mary N; Buse, Maria G (2006) Identification of the major site of O-linked beta-N-acetylglucosamine modification in the C terminus of insulin receptor substrate-1. Mol Cell Proteomics 5:313-23
Buse, Maria G (2006) Hexosamines, insulin resistance, and the complications of diabetes: current status. Am J Physiol Endocrinol Metab 290:E1-E8
Greene, E L; Nelson, B A; Robinson, K A et al. (2001) alpha-Lipoic acid prevents the development of glucose-induced insulin resistance in 3T3-L1 adipocytes and accelerates the decline in immunoreactive insulin during cell incubation. Metabolism 50:1063-9
Gazdag, A C; Wetter, T J; Davidson, R T et al. (2000) Lower calorie intake enhances muscle insulin action and reduces hexosamine levels. Am J Physiol Regul Integr Comp Physiol 278:R504-12
Koh, G; Robinson, K A; Buse, M G (1994) Delayed processing of the insulin proreceptor by hepatocytes from diabetic rats. Biochem Biophys Res Commun 204:725-31

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