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

Abstract

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.

Cellularity Description of Adipose Depots in Domesticated Animals

“…Figure 3 depicts what happens to these parameters with an increase in the number of small adipocytes (hyperplasia) or an increase in the size of large adipocytes (hypertrophy). This is a simulated example (as described by Alfonso [86]), which shows that the hypothesis of hyperplasia (an increase in the number of adipocytes) can be tested on the basis of the differences occurring in the percentage of small adipocytes and the hypothesis of hypertrophy (an increase in the diameter of large adipocytes) can be tested on the basis of the differences occurring in the second mode. The effect of both processes combined is also shown, since both changes in adipocyte number and changes in adipocyte size are known to take place simultaneously [87].…”