Role of Adipocyte Number in Obesity
Adipocyte differentiation involves exit from the cell cycle, a process regulated by cell cycle inhibitors such as the cyclin-dependent kinase inhibitors (CDKIs) p27 and p21. The lack of p27 or p21 results in an increase in adipose tissue in adult mice, starting from about 45 days of age. Adult mice show a two-fold increase in adipose number. This suggests that CDKIs have an important role in the establishment of adipocyte number in mice. To determine whether or not CDKIs regulate adipocyte number before significant changes in adipose mass, adipose development and adipose differentiation factors in p27, p21 knockout (p21KO, p27KO) mice, and wild type-mice (WT) were compared. Female p27KO, p21KO, and WT mice were sacrificed at 30 days of age; fat pads and other organs were collected and weighted. RNA and DNA from fat pads were extracted. Quantitative PCR analysis was used to study the level of differentiation in p27KO and p21KO adipose tissue compared with the WT. Results suggest that adipocyte hyperplastic changes have not occurred at this time (30 days of age). This indicates no significant difference in adipose tissue in single knockout mice when compared with the WT. This finding suggests that the overall difference in adipose tissue and hyperplasia occurs at a later stage. Further research must be done at earlier stages of adipocyte development to determine were in time adipose tissue starts to differ on the single KOs, since at 30 days of ages some difference is already reported.
University of Puerto Rico at Bayamón
Dr. Paul S. Cooke
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