Upregulation of the klotho gene expression by thyroid hormone and during adipose differentiation in 3T3-L1 adipocytes.

A defect in the klotho gene expression in mice leads to a syndrome resembling human aging. The klotho gene encodes a single membrane protein whose extracellular domain carries homology to beta-glucosidases. However, either its function or regulatory mechanism of the gene expression still remains unknown. In the present study, we investigated the klotho gene expression in 3T3-L1 adipocytes using quantitative reverse transcription-polymerase chain reaction. Both membrane and secreted forms of the klotho gene were expressed in 3T3-L1 preadipocytes. Accompanied with adipose differentiation, not the secreted form but the membrane form was gradually increased. In 3T3-L1 adipocytes, triiodothyronine significantly increased the expression levels of membrane form of the klotho gene. These results suggest that the expression of membrane and secreted forms of klotho transcripts are regulated by different mechanisms and that the klotho gene product may play a role in adipose differentiation.