Dexamethasone-induced insulin resistance in 3T3-L1 adipocytes is due to inhibition of glucose transport rather than insulin signal transduction

Hideyuki Sakoda, Takehide Ogihara, Motonobu Anai, Makoto Funaki, Kouichi Inukai, Hideki Katagiri, Yasushi Fukushima, Yukiko Onishi, Hiraku Ono, Midori Fujishiro, Masatoshi Kikuchi, Yoshitomo Oka, Tomoichiro Asano

Research output: Contribution to journalArticlepeer-review

166 Citations (Scopus)

Abstract

Glucocorticoids reportedly induce insulin resistance. In this study, we investigated the mechanism of glucocorticoid-induced insulin resistance using 3T3-L1 adipocytes in which treatment with dexamethasone has been shown to impair the insulin-induced increase in glucose uptake. In 3T3-L1 adipocytes treated with dexamethasone, the GLUT1 protein expression level was decreased by 30%, which possibly caused decreased basal glucose uptake. On the other hand, dexamethasone treatment did not alter the amount of GLUT4 protein in total cell lysates but decreased the insulin-stimulated GLUT4 translocation to the plasma membrane, which possibly caused decreased insulin-stimulated glucose uptake. Dexamethasone did not alter tyrosine phosphorylation of insulin receptors, and it significantly decreased protein expression and tyrosine phosphorylation of insulin receptor substrate (IRS)-1. Interestingly, however, protein expression and tyrosine phosphorylation of IRS-2 were increased. To investigate whether the reduced IRS-1 content is involved in insulin resistance, IRS-1 was overexpressed in dexamethasone-treated 3T3-L1 adipocytes using an adenovirus transfection system. Despite protein expression and phosphorylation levels of IRS-1 being normalized, insulin-induced 2-deoxy-D-[3H]glucose uptake impaired by dexamethasone showed no significant improvement. Subsequently, we examined the effect of dexamethasone on the glucose uptake increase induced by overexpression of GLUT2-tagged p110α, constitutively active Akt (myristoylated Akt), oxidative stress (30 mU glucose oxidase for 2 h), 2 mmol/l 5-aminoimidazole-4-carboxamide ribonucleoside for 30 min, and osmotic shock (600 mmol/l sorbitol for 30 min). Dexamethasone treatment clearly inhibited the increases in glucose uptake produced by these agents. Thus, in conclusion, the GLUT1 decrease may be involved in the dexamethasone-induced decrease in basal glucose transport activity, and the mechanism of dexamethasone-induced insulin resistance in glucose transport activity (rather than the inhibition of phosphatidylinositol 3-kinase activation resulting from a decreased IRS-1 content) is likely to underlie impaired glucose transporter regulation.

Original languageEnglish
Pages (from-to)1700-1708
Number of pages9
JournalDiabetes
Volume49
Issue number10
DOIs
Publication statusPublished - 2000
Externally publishedYes

ASJC Scopus subject areas

  • Internal Medicine
  • Endocrinology, Diabetes and Metabolism

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