Neuronatin: A New Inflammation Gene Expressed on the Aortic Endothelium of Diabetic Mice

Abstract

OBJECTIVE—Identification of arterial genes and pathways altered in obesity and diabetes.

RESEARCH DESIGN AND METHODS—Aortic gene expression profiles of obese and diabetic db/db, high-fat diet–fed C57BL/6J, and control mice were obtained using mouse Affymetrix arrays. Neuronatin (Nnat) was selected for further analysis. To determine the function of Nnat, a recombinant adenovirus (Ad-Nnat) was used to overexpress the Nnat gene in primary endothelial cells and in the mouse aorta in vivo.

RESULTS—Nnat, a gene of unknown vascular function, was upregulated in the aortas of db/db and high-fat diet–fed mice. Nnat gene expression was increased in db/db mouse aorta endothelial cells. Nnat protein was localized to aortic endothelium and was selectively increased in the endothelium of db/db mice. Infection of primary human aortic endothelial cells (HAECs) with Ad-Nnat increased expression of a panel of nuclear factor-κB (NF-κB)-regulated genes, including inflammatory cytokines, chemokines, and cell adhesion molecules. Infection of mouse carotid arteries in vivo with the Ad-Nnat increased expression of vascular cell adhesion molecule 1 protein. Nnat activation of NF-κB and inflammatory gene expression in HAECs was mediated through pathways distinct from tumor necrosis factor-α. Nnat expression stimulated p38, Jun NH₂-terminal kinase, extracellular signal–related kinase, and AKT kinase phosphorylation. Phosphatidylinositol 3-kinase and p38 inhibitors prevented Nnat-mediated activation of NF-κB–induced gene expression.

CONCLUSIONS—Nnat expression is increased in endothelial cells of obese and diabetic mouse blood vessels. The effects of Nnat on inflammatory pathways in vitro and in vivo suggest a pathophysiological role of this new gene in diabetic vascular diseases.