SYNOPSIS
Adiponectin, an adipocyte-derived biologically active molecule, is an abundant plasma protein and has various biological functions. Two types of adiponectin receptors (AdipoR1 and AdipoR2) have been cloned and found to be expressed ubiquitously. More recently, T-cadherin (CDH13) has been characterized as a novel adiponectin receptor on vascular endothelial cells and smooth muscle. In this study, we investigated the effects of adiponectin on gene expression during osteoblast differentiation using DNA microarray analysis and performed pathway analysis of the clusters including adiponectin receptors.
Osteoblastic differentiation of a murine pro-osteoblastic cell line MC3T3-E1 was induced by ascorbic acid and b-glycerophosphate with or without recombinant murine adiponectin. Three days after stimulation, gene expression profiles were obtained by DNA microarray analysis and used for hierarchical clustering with correlation centered similarity metrics. Functional cluster annotations for selected clusters were generated based on significant gene ontology terms, and the relationship among genes was visualized by pathway analysis.
Genes significantly upregulated by differentiation medium were related to osteoblast differentiation and cell growth. The genes included in cluster AdipoR1 were downregulated by differentiation medium, but those in cluster AdipoR2 were upregulated by the medium. The genes included in cluster CDH13 were also upregulated during osteoblastic differentiation.
Our study suggests that AdipoR2 and CDH13, rather than AdipoR1, may be involved in osteoblastic differentiation.

Key words: adiponectin receptor, CDH13, osteoblast, differentiation