Signaling cross-talk between hypoxia and glucose via hypoxia-inducible factor 1 and glucose response elements

Abstract

The substrates oxygen and glucose are important for the appropriate regulation of metabolism, angiogenesis, tumorigenesis and embryonic development. The knowledge about an interaction between these two signals is limited. We demonstrated that the regulation of glucagon receptor, insulin receptor and L-type pyruvate kinase (L-PK) gene expression in liver is dependent upon a cross-talk between oxygen and glucose. The periportal to perivenous drop in O2 tension was proposed to be an endocrine key regulator for the zonated gene expression in liver. In primary rat hepatocyte cultures, the expression of the glucagon receptor and the L-PK mRNA was maximally induced by glucose under arterial pO2 whereas the insulin receptor was maximally induced under perivenous pO2. It was demonstrated for the L-PK gene that the modulation by O2 of the glucose-dependent induction occured at the glucose-responsive element (Glc(PK)RE) in the L-PK gene promoter. The reduction of the glucose-dependent induction of the L-PK gene expression under venous pO2 appeared to be mediated via an interference between hypoxia-inducible factor 1 (HIF-1) and the glucose-responsive transcription factors at the Glc(PK)RE. The glucose response element (GlcRE) also functioned as a hypoxia response element and, vice versa, a hypoxia-responsive element was functioning as a GlcRE. Thus, our findings implicate that the cross-talk between oxygen and glucose might have a fundamental role in the regulation of several physiological and pathophysiological processes.