EXPRESSION OF OB GENE IN ADIPOSE-CELLS - REGULATION BY INSULIN

The product of the recently cloned mouse obese (ob) gene is likely to play an important role in a loop regulating the size of the adipose ti ssue mass, The hormonal regulation of the ob gene could affect adiposi ty. To investigate this point, the effect of insulin on ob gene expres sion was examined in cells of the 3T3-F442A preadipocyte clonal line. ob mRNA is absent from exponentially growing, undifferentiated cells a s well as from confluent preadipose cells, Terminal differentiation of preadipose to adipose cells leads to the expression of ob mRNA detect ed by a sensitive and quantitative ribonuclease protection assay, In a dipose cells, the level of ob mRNA is sensitive to insulin in the nano molar range of concentrations with an increase from an average of 1 co py to 5-10 copies/cell. The effect of insulin was fully reversible and takes place primarily at a transcriptional level, The ob mRNA shows a rapid turnover, with a half-life of approximately 2 h in the absence or presence of insulin, The level of secreted Ob protein is also regul ated by insulin, These results indicate that the ob gene is expressed in mature fat cells only and support the possibility that insulin is a n important regulator of ob gene expression.