Correction for adipocyte size and number in the analysis of differences in gene expression in fat tissues.

In gene expression studies of candidate genes related to fat deposition, accounting for differences in cell number using reference genes could be not sufficient when cell transcriptional levels are related to cell size, or the tissues are constituted by different types of cells where candidate genes could be differentially expressed. In these situations, mixed model can be applied giving the possibility to take into account the effects of adipocyte size and number on gene expression. The inclusion in the models of analysis of adipocyte size and number, previously estimated taking into account the possible bimodality of size distribution, reduces the rate of false positives in the expression of candidate genes, although, as expected, more powerful designs are needed to detect true differences. The analysis of cellularity of adipose tissue is recommended to infer differences in the expression of genes related to fat deposition.