C. Olichonberthe et al., INSULIN-RECEPTOR DEPHOSPHORYLATION BY PHOSPHOTYROSINE PHOSPHATASES OBTAINED FROM INSULIN-RESISTANT OBESE MICE, Diabetologia, 37(1), 1994, pp. 56-60
Citations number
23
Categorie Soggetti
Endocrynology & Metabolism","Medicine, General & Internal
To study the possible involvement of phosphotyrosine phosphatases in i
nsulin resistance, the ability of cytosolic and membrane preparations
to dephosphorylate insulin receptors was examined in lean and goldthio
glucose-treated insulin-resistant and obese mice. Preparations were ob
tained from liver, heart, diaphragm and hindleg muscle and their phosp
hotyrosine phosphatase activities were measured using an immunoenzymat
ic assay with phosphorylated insulin receptors as substrate. Liver cyt
osolic and particulate phosphotyrosine phosphatases were more potent t
han preparations from other tissues and were able to almost completely
dephosphorylate the insulin receptor in a dose- and time-dependent ma
nner. No change was observed in cytosolic and membrane-associated phos
photyrosine phosphatases in liver, diaphragm, and heart of obese mice
compared with lean mice. In contrast, cytosolic, but not membrane-asso
ciated, phosphotyrosine phosphatase activity was decreased in hindleg
muscles of obese mice. These results suggest that the regulation of ph
osphotyrosine phosphatases is tissue-specific. In addition, alteration
s in total phosphotyrosine phosphatase activity do not appear to play
an important role in insulin resistance in all tissues of obese mice,
although specific changes cannot be excluded.