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Cdc2-like kinase 2 is an insulin-regulated suppressor of hepatic gluconeogenesis.

ABSTRACT: Dynamic regulation of insulin signaling and metabolic gene expression is critical to nutrient homeostasis; dysregulation of these pathways is widely implicated in insulin resistance and other disease states. Though the metabolic effects of insulin are well established, the components linking insulin signal transduction to a metabolic response are not as well understood. Here, we show that Cdc2-like kinase 2 (Clk2) is an insulin-regulated suppressor of hepatic gluconeogenesis and glucose output. Clk2 protein levels and kinase activity are induced as part of the hepatic refeeding response by the insulin/Akt pathway. Clk2 directly phosphorylates the SR domain on PGC-1alpha, resulting in repression of gluconeogenic gene expression and hepatic glucose output. In addition, Clk2 is downregulated in db/db mice, and reintroduction of Clk2 largely corrects glycemia. Thus, we have identified a role for and regulation of the Clk2 kinase as a component of hepatic insulin signaling and glucose metabolism.

SUBMITTER: Rodgers JT

PROVIDER: S-EPMC2807620 | biostudies-literature | 2010 Jan

REPOSITORIES: biostudies-literature

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Cdc2-like kinase 2 is an insulin-regulated suppressor of hepatic gluconeogenesis.

Rodgers Joseph T JT Haas Wilhelm W Gygi Steven P SP Puigserver Pere P

Cell metabolism 20100101 1

Dynamic regulation of insulin signaling and metabolic gene expression is critical to nutrient homeostasis; dysregulation of these pathways is widely implicated in insulin resistance and other disease states. Though the metabolic effects of insulin are well established, the components linking insulin signal transduction to a metabolic response are not as well understood. Here, we show that Cdc2-like kinase 2 (Clk2) is an insulin-regulated suppressor of hepatic gluconeogenesis and glucose output. ...[more]

PMID: 20074525

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Project description:BACKGROUNDWhile saturated fat intake leads to insulin resistance and nonalcoholic fatty liver, Mediterranean-like diets enriched in monounsaturated fatty acids (MUFA) may have beneficial effects. This study examined effects of MUFA on tissue-specific insulin sensitivity and energy metabolism.METHODSA randomized placebo-controlled cross-over study enrolled 16 glucose-tolerant volunteers to receive either oil (OIL, ~1.18 g/kg), rich in MUFA, or vehicle (VCL, water) on 2 occasions. Insulin sensitivity was assessed during preclamp and hyperinsulinemic-euglycemic clamp conditions. Ingestion of 2H2O/acetaminophen was combined with [6,6-2H2]glucose infusion and in vivo 13C/31P/1H/ex vivo 2H-magnet resonance spectroscopy to quantify hepatic glucose and energy fluxes.RESULTSOIL increased plasma triglycerides and oleic acid concentrations by 44% and 66% compared with VCL. Upon OIL intervention, preclamp hepatic and whole-body insulin sensitivity markedly decreased by 28% and 27%, respectively, along with 61% higher rates of hepatic gluconeogenesis and 32% lower rates of net glycogenolysis, while hepatic triglyceride and ATP concentrations did not differ from VCL. During insulin stimulation hepatic and whole-body insulin sensitivity were reduced by 21% and 25%, respectively, after OIL ingestion compared with that in controls.CONCLUSIONA single MUFA-load suffices to induce insulin resistance but affects neither hepatic triglycerides nor energy-rich phosphates. These data indicate that amount of ingested fat, rather than its composition, primarily determines the development of acute insulin resistance.TRIAL REGISTRATIONClinicalTrials.gov NCT01736202.FUNDINGGerman Diabetes Center, German Federal Ministry of Health, Ministry of Culture and Science of the state of North Rhine-Westphalia, German Federal Ministry of Education and Research, German Diabetes Association, German Center for Diabetes Research, Portugal Foundation for Science and Technology, European Regional Development Fund, and Rede Nacional de Ressonancia Magnética Nuclear.

Project description:ObjectiveHepatic insulin resistance, which leads to increased hepatic gluconeogenesis, is a major contributor to fasting hyperglycemia in type 2 diabetes mellitus (T2DM). However, the mechanism of impaired insulin-dependent suppression of hepatic gluconeogenesis remains elusive. Delta/Notch-like epidermal growth factor (EGF)-related receptor (DNER), ﬁrstly described as a neuron-specific Notch ligand, has been recently identiﬁed as a susceptibility gene for T2DM through genome-wide association studies. We herein investigated whether DNER regulates hepatic gluconeogenesis and whether this is mediated by enhanced insulin signaling.MethodsThe association between DNER, tribbles homolog 3 (TRB3) and Akt signaling was evaluated in C57BL/6J, ob/ob and db/db mice by western blot analysis. DNER loss-of-function and gain-of-function in hepatic gluconeogenesis were analyzed by western blot analysis, quantitative real-time PCR, glucose uptake and output assay in AML-12 cells and partially validated in primary mouse hepatocytes. Hepatic DNER knockdown mice were generated by tail vein injection of adenovirus to confirm the effects of DNER in vivo. The interaction between DNER and TRB3 was investigated by rescue experiments, cycloheximide chase analysis, co-immunoprecipitation and immunofluorescence. The potential insulin-stimulated phosphorylation sites of DNER were determined by co-immunoprecipitation, LC-MS/MS analysis and site-specific mutagenesis.ResultsHere we show that DNER enhanced hepatic insulin signaling in gluconeogenesis by inhibiting TRB3, an endogenous Akt inhibitor, through the ubiquitin-proteasome degradation pathway. In AML-12 hepatocytes, insulin-stimulated activation of Akt and suppression of gluconeogenesis are attenuated by DNER knockdown, but potentiated by DNER over-expression. In C57BL/6J mice, hepatic DNER knockdown is accompanied by impaired glucose and pyruvate tolerance. Furthermore, the in vitro effects of DNER knockdown or over-expression on both Akt activity and hepatic gluconeogenesis can be rescued by TRB3 knockdown or over-expression, respectively. In response to insulin stimulation, DNER interacted directly with insulin receptor and was phosphorylated at Tyr677. This site-specific phosphorylation is essential for DNER to upregulate Akt activity and then downregulate G6Pase and PEPCK expression, by interacting with TRB3 directly and inducing TRB3 proteasome-dependent degradation.ConclusionsTaken together, the crosstalk between insulin-Akt and DNER-TRB3 pathways represents a previously unrecognized mechanism by which insulin regulates hepatic gluconeogenesis.

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Cdc2-like kinase 2 is an insulin-regulated suppressor of hepatic gluconeogenesis.

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Cdc2-like kinase 2 is an insulin-regulated suppressor of hepatic gluconeogenesis.

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