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Glucokinase links Krüppel-like factor 6 to the regulation of hepatic insulin sensitivity in nonalcoholic fatty liver disease

Lookup NU author(s): Dr Gillian Patman, Laura Pascoe, Dr Luca Miele, Douglas Hui, Professor Alastair BurtORCiD, Professor Chris Day, Professor Loranne Agius, Professor Mark Walker, Professor Helen ReevesORCiD

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Abstract

The polymorphism, KLF6-IVS1-27A, in the Krüppel-like factor 6 (KLF6) transcription factor gene enhances its splicing into antagonistic isoforms and is associated with delayed histological progression of nonalcoholic fatty liver disease (NAFLD). To explore a potential role for KLF6 in the development of insulin resistance, central to NAFLD pathogenesis, we genotyped KLF6-IVS1-27 in healthy subjects and assayed fasting plasma glucose (FPG) and insulin sensitivities. Furthermore, we quantified messenger RNA (mRNA) expression of KLF6 and glucokinase (GCK), as an important mediator of insulin sensitivity, in human livers and in liver tissues derived from a murine Klf6 knockdown model (DeltaKlf6). Klf6 overexpression studies in a mouse hepatocyte line were utilized to mechanistically link KLF6 with Gck promoter activity. KLF6-IVS1-27Gwt (i.e., less KLF6 splicing) was associated with stepwise increases in FPG and insulin and reduced hepatic insulin sensitivity. KLF6 binds to the liver-specific Gck promoter and activates a GCK promoter-reporter, identifying GCK as a KLF6 direct transcriptional target. Accordingly, in DeltaKlf6 hepatocytes Gck expression was reduced and stable transfection of Klf6 led to up-regulation of Gck. GCK and KLF6 mRNAs correlate directly in human NAFLD tissues and immunohistochemistry studies confirm falling levels of both KLF6 and GCK in fat-laden hepatocytes. In contrast to full-length KLF6, splice variant KLF6-SV1 increases in NAFLD hepatocytes and inversely correlates with glucokinase regulatory protein, which negatively regulates GCK activity. Conclusion: KLF6 regulation of GCK contributes to the development of hepatic insulin resistance. The KLF6-IVS1-27A polymorphism, which generates more KLF6-SV1, combats this, lowering hepatic insulin resistance and blood glucose.

Publication metadata

Author(s): Bechmann LP, Gastaldelli A, Vetter D, Patman GL, Pascoe L, Hannivoort RA, Lee UE, Fiel I, Muñoz U, Ciociaro D, Buzzigoli E, Miele L, Hui KY, Bugianesi E, Burt AD, Day CP, Mari A, Agius L, Walker M, Friedman SL, Reeves HL

Publication type: Article

Publication status: Published

Journal: Hepatology

Year: 2012

Volume: 55

Issue: 4

Pages: 1083-1093

Print publication date: 01/04/2012

ISSN (print): 0270-9139

ISSN (electronic): 1527-3350

Publisher: John Wiley & Sons, Inc.

URL: http://dx.doi.org/10.1002/hep.24793

DOI: 10.1002/hep.24793

PubMed id: 22095588

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