Release of PAI-1 by human preadipocytes and adipocytes independent of insulin and IGF-1.

The effect of insulin and insulin-like growth factor-1 (IGF-1) on plasminogen activator inhibitor-1 (PAI-1) release from primary cultures of human preadipocytes and adipocytes has been investigated. Initial experiments measuring basal PAI-1 release (ng/ml) indicated variability between individual cultures. Using a novel technique for adipocyte quantitation, additional experiments were performed to determine PAI-1 release per cell, indicating a significant reduction with differentiation. Insulin and IGF-1 over a range of concentrations had no effect on PAI-1 release, and RT-PCR of PAI-1 mRNA following treatment with insulin and IGF-1 also indicated similar expression between treatments. The cultures did exhibit insulin-stimulated glyceraldehyde-3-phosphate dehydrogenase (GAPDH) expression and leptin synthesis following differentiation to the adipocyte phenotype. This is the first report of PAI-1 secretion by primary cultures of human preadipocytes and adipocytes, indicating PAI-1 release independent of insulin and IGF-1 and implicating other factors in the elevated plasma PAI-1 observed with insulin resistance.