Comparison of the adipoconversion of preadipocytes derived from lean and obese Zucker rats in serum-free cultures

Serum-free cultures of preadipocytes derived from lean and obese Zucker rats were established to compare their adipoconversion in strictly controlled culture conditions.

Preadipocytes were isolated from the epididymal adipose tissue of 4- and/or 8-week-old homozygous lean (Fa/Fa) and obese (fa/fa) Zucker rats and cultured in serum-free medium containing insulin, transferrin and triidothyronine.

Adipoconversion of lean- and obese-derived preadipocytes was assessed by morphological observations as well as determination of glycerol-3-phosphate dehydrogenase (GPDH) and lipoprotein lipase (LPL) activities.

In serum-free culture conditions, no significant difference was found between lean- and obese-derived cells obtained from 4-week-old rats. In both groups, an extensive differentiation took place and lipid accumulation as well as GPDH activity were similar. By contrast, a differential adipoconversion was observed with cells derived from older rats: obese-derived cells differentiated poorly, as assessed by the reduced lipid accumulation and low GPDH activity. Positive oil red O staining and detection of LPL mRNA and activity in obese-derived cultures indicated the preadipose nature of these cells. Replacement of insulin by insulin-like growth factor 1 as well as addition of glucocorticoids into the serum-free medium did not reduce the difference of adipoconversion levels observed between lean and obese cells.

Taken together, these results suggest that the differences in adipoconversion observed between preadipocytes derived from lean and obese adult Zucker rats result from differences in their stage of commitment to differentiation. The similar adipoconversion displayed by preadipocytes derived from younger rats suggests that presence of the fa gene does not affect fat storage capacity under serum-free conditions.