title: Overexpression of the dual-specificity phosphatase MKP-4/DUSP-9 protects against stress-induced insulin resistance.
abstract: Insulin resistance, a hallmark of type 2 diabetes and obesity, is associated with increased activity of MAP and stress-activated protein (SAP) kinases, which results in decreased insulin signaling. Our goal was to investigate the role of MAP kinase phosphatase-4 (MKP-4) in modulating this process. We found that MKP-4 expression is up-regulated during adipocyte and myocyte differentiation in vitro and up-regulated during fasting in white adipose tissue in vivo. Overexpression of MKP-4 in 3T3-L1 cells inhibited ERK and JNK phosphorylation and, to a lesser extent, p38MAPK phosphorylation. As a result, the phosphorylation of IRS-1 serine 307 induced by anisomycin was abolished, leading to a sensitization of insulin signaling with recovery of insulin-stimulated IRS-1 tyrosine phosphorylation, IRS-1 docking with phosphatidylinositol 3-kinase, and Akt phosphorylation. MKP-4 also reversed the effect of TNF-alpha to inhibit insulin signaling; alter IL-6, Glut1 and Glut4 expression; and inhibit insulin-stimulated glucose uptake in 3T3-L1 adipocytes. Overexpression of MKP-4 in the liver of ob/ob mice decreased ERK and JNK phosphorylation, leading to a reduction in fed and fasted glycemia, improved glucose intolerance, decreased expression of gluconeogenic and lipogenic genes, and reduced hepatic steatosis. Thus, MKP-4 has a protective effect against the development of insulin resistance through its ability to dephosphorylate and inactivate crucial mediators of stress-induced insulin resistance, such as ERK and JNK, and increasing MKP-4 activity might provide a therapy for insulin-resistant disorders.
authors.affiliation: Joslin Diabetes Center, Harvard Medical School, Boston, MA 02215, USA.
authors.forename: Brice
authors.initials: B
authors.lastname: Emanuelli
authors.forename: Delphine
authors.initials: D
authors.lastname: Eberlé
authors.forename: Ryo
authors.initials: R
authors.lastname: Suzuki
authors.forename: C Ronald
authors.initials: CR
authors.lastname: Kahn
mesh_terms: D017667:Adipocytes / Q000166:cytology; D000818:Animals; D002454:Cell Differentiation / Q000235:genetics; D002460:Cell Line; D054637:Dual-Specificity Phosphatases / Q000235:genetics / Q000502:physiology*; D005786:Gene Expression Regulation; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D007333:Insulin Resistance; D051379:Mice; D032342:Muscle Cells / Q000166:cytology; D010766:Phosphorylation; D015398:Signal Transduction
chemical_list: D007328:Insulin; D054637:Dual-Specificity Phosphatases; C484491:Dusp9 protein, mouse