Diabetes, Vol 40, Issue 12 1620-1629, Copyright © 1991 by American Diabetes Association

ARTICLES

Differential effects of diabetes on adipocyte and liver phosphotyrosine and phosphoserine phosphatase activities

N Begum, KE Sussman and B Draznin
Department of Medicine, Veterans Administration Medical Center, Denver, Colorado.

We examined the activities of particulate and cytosolic phosphotyrosine phosphatase (PTPase) and phosphoserine phosphatase (PSPase) in adipocytes and livers of diabetic rats. PTPase activity was assessed with [32P]tyrosine-phosphorylated insulin receptor (IR), whereas PSPase activity was assayed with [32P]serine-phosphorylated glycogen synthase. Diabetes increased adipocyte particulate PTPase activity and enhanced IR dephosphorylation by 75% on the 2nd, 93% on the 14th, and 108% on the 30th day. In contrast, cytosolic PTPase activity decreased by 78% on the 14th and 45% on the 30th day (no change on the 2nd day). Similar changes were observed with PSPase (increased activity in particulate and decreased in cytosolic). Insulin therapy for 14 or 30 days restored PTPase and PSPase activities in both fractions. Vanadate, despite rapid normalization of glycemia, restored these activities only after 30 days of therapy. Diabetes-related changes in liver PTPase activity were observed on the 14th day only. At this time, it was increased in both particulate and cytosolic fractions. There was spontaneous normalization of the liver PTPase activity at 30 days of diabetes. In contrast, liver cytosolic PSPase activity was significantly inhibited and not normalized by the 30th day of disease without therapy. In summary, diabetes appears to induce tissue-specific changes in PTPase and PSPase activities resulting in significant alterations in dephosphorylation of IR and glycogen synthase. Moreover, there appears to be a differential regulation of PTPase and PSPase activities in diabetes, particularly in the liver.
CiteULike    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				A. Khan, M. Safdar, M. M. Ali Khan, K. N. Khattak, and R. A. Anderson Cinnamon Improves Glucose and Lipids of People With Type 2 Diabetes Diabetes Care, December 1, 2003; 26(12): 3215 - 3218. [Abstract] [Full Text] [PDF]

				L. Marti, A. Abella, C. Carpene, M. Palacin, X. Testar, and A. Zorzano Combined Treatment With Benzylamine and Low Dosages of Vanadate Enhances Glucose Tolerance and Reduces Hyperglycemia in Streptozotocin-Induced Diabetic Rats Diabetes, September 1, 2001; 50(9): 2061 - 2068. [Abstract] [Full Text] [PDF]

				K. J. Jarvill-Taylor, R. A. Anderson, and D. J. Graves A Hydroxychalcone Derived from Cinnamon Functions as a Mimetic for Insulin in 3T3-L1 Adipocytes J. Am. Coll. Nutr., August 1, 2001; 20(4): 327 - 336. [Abstract] [Full Text] [PDF]

				S. Tang, H. Le-Tien, B. J. Goldstein, P. Shin, R. Lai, and I. G. Fantus Decreased In Situ Insulin Receptor Dephosphorylation in Hyperglycemia-Induced Insulin Resistance in Rat Adipocytes Diabetes, January 1, 2001; 50(1): 83 - 90. [Abstract] [Full Text]

				L. D. Klaman, O. Boss, O. D. Peroni, J. K. Kim, J. L. Martino, J. M. Zabolotny, N. Moghal, M. Lubkin, Y.-B. Kim, A. H. Sharpe, et al. Increased Energy Expenditure, Decreased Adiposity, and Tissue-Specific Insulin Sensitivity in Protein-Tyrosine Phosphatase 1B-Deficient Mice Mol. Cell. Biol., August 1, 2000; 20(15): 5479 - 5489. [Abstract] [Full Text]

				L. Ragolia, B. Cherpalis, M. Srinivasan, and N. Begum Role of Serine/Threonine Protein Phosphatases in Insulin Regulation of Na+/K+-ATPase Activity in Cultured Rat Skeletal Muscle Cells J. Biol. Chem., September 19, 1997; 272(38): 23653 - 23658. [Abstract] [Full Text] [PDF]

				H. Maegawa, R. Ide, M. Hasegawa, S. Ugi, K. Egawa, M. Iwanishi, R. Kikkawa, Y. Shigeta, and A. Kashiwagi Thiazolidine Derivatives Ameliorate High Glucose-induced Insulin Resistance via the Normalization of Protein-tyrosine Phosphatase Activities J. Biol. Chem., March 31, 1995; 270(13): 7724 - 7730. [Abstract] [Full Text] [PDF]