Coordinated stimulation by triiodothyronine of fatty acid synthesis and isoproterenol-sensitive fatty acid release in two preadipocyte cell lines of lean or genetically obese mice.

The development and thyroid hormone sensitivity of fatty acid and triacylglycerol synthesis from 14C-acetate and of the isoproterenol-sensitive fatty acid release, were studied in two preadipocyte cell lines during the adipose differentiation: the Ob 17 and the HGFu cell lines cloned from the periepididymal adipose tissue of adult mice genetically obese and phenotypically lean respectively. Both parameters increased and peaked in the same time-period during the second week of culture after confluence. Both parameters were also amplified when T3 was added to the culture medium at confluence. The increment due to T3 was concentration dependent: it peaked at the physiological concentration of 1.5 nM and declined thereafter with the same pattern. This shows that some steps of two opposite pathways of lipid metabolism in differentiating preadipose cells can be stimulated by triiodothyronine in a similar manner and suggests a coordinated regulation. No significant difference could be detected between cells from lean or genetically obese mice.