Age-related changes of renin-angiotensin system genes in white adipose tissue of rats

The adipose tissue renin-angiotensin system has been implicated in the regulation of adipocyte growth and differentiation. We studied the influence of age, body weight, total body fat content, anatomical localization, and diet on the expression of angiotensinogen (AGT) and angiotensin II type 1 (AT(1))-receptor genes in white adipose tissue of normal and postnatal overfed rats. Relative gene expression was measured in epididymal adipose tissue and liver of control and postnatal overfed (PNO) rats at the age of 4, 8, and 12 weeks using real time RT-PCR. Body fat content was determined by carcass analysis. Body weight and body fat content were only significantly greater in PNO rats when compared to control rats at the age of 4 weeks. At the age of 12 weeks, AGT expression was significantly decreased in both tissues. Furthermore, expression of the AT,-receptor gene was significantly decreased in liver but not in adipose tissue at 12 weeks of age. Postnatal overfeeding did not influence the expression levels of either gene at any time-point in either liver or adipose tissue. At the age of 24 weeks, AGT expression was significantly greater in epididymal than in subcutaneous adipose tissue, whereas no site-specific differences could be found for the AT,-receptor. We conclude that age and depot-specific mechanisms are of more importance for the expression of AGT and AT(1)-receptor genes during the first 12 weeks of age than a short period of overfeeding.