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J Biol Chem. 2014 Jan 24;289(4):2396-404. doi: 10.1074/jbc.M113.511766. Epub 2013 Dec 5.

Apolipoprotein A-IV reduces hepatic gluconeogenesis through nuclear receptor NR1D1.

Author information

1
From the Cincinnati Obesity Research Center, Metabolic Diseases Institute, University of Cincinnati, Cincinnati, Ohio 45237 and.

Abstract

We showed recently that apoA-IV improves glucose homeostasis by enhancing pancreatic insulin secretion in the presence of elevated levels of glucose. Therefore, examined whether apolipoprotein A-IV (apoA-IV) also regulates glucose metabolism through the suppression of hepatic gluconeogenesis. The ability of apoA-IV to lower gluconeogenic gene expression and glucose production was measured in apoA-IV(-/-) and wild-type mice and primary mouse hepatocytes. The transcriptional regulation of Glc-6-Pase and phosphoenolpyruvate carboxykinase (PEPCK) by apoA-IV was determined by luciferase activity assay. Using bacterial two-hybrid library screening, NR1D1 was identified as a putative apoA-IV-binding protein. The colocalization and interaction between apoA-IV and NR1D1 were confirmed by immunofluorescence, in situ proximity ligation assay, and coimmunoprecipitation. Enhanced recruitment of NR1D1 and activity by apoA-IV to Glc-6-Pase promoter was verified with ChIP and a luciferase assay. Down-regulation of apoA-IV on gluconeogenic genes is mediated through NR1D1, as illustrated in cells with NR1D1 knockdown by siRNA. We found that apoA-IV suppresses the expression of PEPCK and Glc-6-Pase in hepatocytes; decreases hepatic glucose production; binds and activates nuclear receptor NR1D1 and stimulates NR1D1 expression; in cells lacking NR1D1, fails to inhibit PEPCK and Glc-6-Pase gene expression; and stimulates higher hepatic glucose production and higher gluconeogenic gene expression in apoA-IV(-/-) mice. We conclude that apoA-IV inhibits hepatic gluconeogenesis by decreasing Glc-6-Pase and PEPCK gene expression through NR1D1. This novel regulatory pathway connects an influx of energy as fat from the gut (and subsequent apoA-IV secretion) with inhibition of hepatic glucose production.

KEYWORDS:

Apolipoprotein A-IV; Apolipoproteins; Diabetes; Gluconeogenesis; NR1D1; Nuclear Receptors; Phosphoenolpyruvate Carboxykinase

PMID:
24311788
PMCID:
PMC3900982
DOI:
10.1074/jbc.M113.511766
[Indexed for MEDLINE]
Free PMC Article

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