title: Impairment of insulin-stimulated glucose transport and ERK activation by adipocyte-specific knockout of PKC-λ produces a phenotype characterized by diminished adiposity and enhanced insulin suppression of hepatic gluconeogenesis.
abstract: Tissue-specific knockout (KO) of atypical protein kinase C-λ (PKC-λ) impairs insulin-stimulated glucose transport in muscle (M) and lipid synthesis in liver (L), thereby producing insulin resistance in MλKO mice and insulin-hypersensitivity in LλKO mice. Here, we generated mice with KO of PKC-λ in adipocytes, i.e., AλKO mice. In isolated adipocytes of AλKO mice, insulin-stimulated aPKC activity and glucose transport were diminished, as were ERK levels and activity. Insulin-stimulated glucose transport and insulin activation of ERK in adipocytes of wild-type mice were similarly inhibited by acute inhibition of PKC-λ with a highly-specific chemical inhibitor. With impairments in glucose transport and ERK activation, AλKO mice had diminished adiposity and serum leptin levels. In addition, AλKO mice had normal glucose tolerance and insulin hypersensitivity owing to enhanced suppression of hepatic glucose output, which apparently reflected increases in Akt activity and FoxO1 phosphorylation, and subsequent decreases in expression of gluconeogenic phosphoenolpyruvate carboxykinase. We conclude that: PKC-λ is required for insulin-stimulated glucose transport and ERK signaling in mouse adipocytes; and diminution of these processes is attended by leanness and therefore hypoleptinemia. How these and perhaps other PKC-λ-dependent processes communicate to liver and improve insulin suppression of hepatic gluconeogenesis remains unclear.
authors.affiliation: James A Haley Veterans Medical Center; Tampa, FL USA ; Department of Internal Medicine; University of South Florida College of Medicine; Tampa, FL USA.
authors.forename: Mini P
authors.initials: MP
authors.lastname: Sajan
authors.affiliation: Departments of Internal Medicine and Cellular and Molecular Physiology; Howard Hughes Medical Institute; Yale University School of Medicine; New Haven, CT USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Jurzak
authors.affiliation: Departments of Internal Medicine and Cellular and Molecular Physiology; Howard Hughes Medical Institute; Yale University School of Medicine; New Haven, CT USA.
authors.forename: Varman T
authors.initials: VT
authors.lastname: Samuels
authors.affiliation: Departments of Internal Medicine and Cellular and Molecular Physiology; Howard Hughes Medical Institute; Yale University School of Medicine; New Haven, CT USA.
authors.forename: Gerald I
authors.initials: GI
authors.lastname: Shulman
authors.affiliation: Division of Nephrology; Department of Medicine; Hannover Medical School; Hannover, Germany ; Biotechnology Centre of Oslo; Oslo, Norway.
authors.forename: Ursula
authors.initials: U
authors.lastname: Braun
authors.affiliation: Division of Nephrology; Department of Medicine; Hannover Medical School; Hannover, Germany ; Biotechnology Centre of Oslo; Oslo, Norway.
authors.forename: Michael
authors.initials: M
authors.lastname: Leitges
authors.affiliation: James A Haley Veterans Medical Center; Tampa, FL USA ; Department of Internal Medicine; University of South Florida College of Medicine; Tampa, FL USA.
authors.forename: Robert V
authors.initials: RV
authors.lastname: Farese
keywords: ERK; PKC-λ; adipocyte; diabetes; glucose transport; insulin; liver