Dataset Information

Carbohydrate-responsive element-binding protein (ChREBP) is a negative regulator of ARNT/HIF-1beta gene expression in pancreatic islet beta-cells.

ABSTRACT:

Objective

Carbohydrate-responsive element-binding protein (ChREBP) is a transcription factor that has been shown to regulate carbohydrate metabolism in the liver and pancreatic beta-cells in response to elevated glucose concentrations. Because few genes have been identified so far as bona fide ChREBP-target genes, we have performed a genome-wide analysis of the ChREBP transcriptome in pancreatic beta-cells.

Research design and methods

Chromatin immunoprecipitation and high-density oligonucleotide tiling arrays (ChIP-chip; Agilent Technologies) using MIN6 pancreatic beta-cell extracts were performed together with transcriptional and other analysis using standard techniques.

Results

One of the genes identified by ChIP-chip and linked to glucose sensing and insulin secretion was aryl hydrocarbon receptor nuclear translocator (ARNT)/hypoxia-inducible factor-1beta (HIF-1beta), a transcription factor implicated in altered gene expression and pancreatic-islet dysfunction in type 2 diabetes. We first confirmed that elevated glucose concentrations decreased ARNT/HIF-1beta levels in INS-1 (832/13) cells and primary mouse islets. Demonstrating a role for ChREBP in ARNT gene regulation, ChREBP silencing increased ARNT mRNA levels in INS-1 (832/13) cells, and ChREBP overexpression decreased ARNT mRNA in INS-1 (832/13) cells and primary mouse islets. We demonstrated that ChREBP and Max-like protein X (MLX) bind on the ARNT/HIF-1beta promoter on the proximal region that also confers the negative glucose responsiveness.

Conclusions

These results demonstrate that ChREBP acts as a novel repressor of the ARNT/HIF-1beta gene and might contribute to beta-cell dysfunction induced by glucotoxicity.

SUBMITTER: Noordeen NA

PROVIDER: S-EPMC2797916 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:ObjectiveCarbohydrate response element binding protein (ChREBP) is a transcription factor that responds to glucose and activates genes involved in the glycolytic and lipogenic pathways. Recent studies have linked adipose ChREBP to insulin sensitivity in mice. However, while ChREBP is most highly expressed in the liver, the effect of hepatic ChREBP on insulin sensitivity remains unknown. To clarify the importance of hepatic ChREBP on glucose homeostasis, we have generated a knockout mouse model that lacks this protein specifically in the liver (Liver-ChREBP KO).MethodsUsing Liver-ChREBP KO mice, we investigated whether hepatic ChREBP deletion influences insulin sensitivity, glucose homeostasis and the development of hepatic steatosis utilizing various dietary stressors. Furthermore, we determined gene expression changes in response to fasted and fed states in liver, white, and brown adipose tissues.ResultsLiver-ChREBP KO mice had impaired insulin sensitivity as indicated by reduced glucose infusion to maintain euglycemia during hyperinsulinemic-euglycemic clamps on both chow (25% lower) and high-fat diet (33% lower) (p < 0.05). This corresponded with attenuated suppression of hepatic glucose production. Although Liver-ChREBP KO mice were protected against carbohydrate-induced hepatic steatosis, they displayed worsened glucose tolerance. Liver-ChREBP KO mice did not show the expected gene expression changes in liver in response to fasted and fed states. Interestingly, hepatic ChREBP deletion also resulted in gene expression changes in white and brown adipose tissues, suggesting inter-tissue communication. This included an almost complete abolition of BAT ChREBPβ induction in the fed state (0.15-fold) (p = 0.015) along with reduced lipogenic genes. In contrast, WAT showed inappropriate increases in lipogenic genes in the fasted state along with increased PEPCK1 in both fasted (3.4-fold) and fed (5.1-fold) states (p < 0.0001).ConclusionsOverall, hepatic ChREBP is protective in regards to hepatic insulin sensitivity and whole body glucose homeostasis. Hepatic ChREBP action can influence other peripheral tissues and is likely essential in coordinating the body's response to different feeding states.