Expression of Angiotensin II Receptors Type 1 and Type 2 in Human Preadipose Cells During Differentiation

Abstract

Human adipose tissue expresses all the components necessary for the production of angiotensin peptides. Although local effects of angiotensin II on cells from adipose tissue are beginning to be recognised, the expression of angiotensin receptors on human preadipocytes and adipocytes is still controversial. This study addresses the issue by monitoring the mRNA levels as well as the protein production of angiotensin II receptors of type 1 and 2 (AT₁ and AT₂) during differentiation of primary human preadipocytes in culture and in mature adipocytes. mRNA levels of the two receptor types are inversely correlated during adipose conversion. AT₁ receptor mRNA is greatly diminished within 12 days after induction of differentiation, while AT₂ receptor mRNA is elevated. mRNA levels of mature adipocytes confirm this trend. The regulation is not seen as strongly on the protein level. The amount of AT₂ receptor protein is increased, correlating well with the rise in specific glycerol-3-phosphate dehydrogenase activity of the cells, but the AT₁ receptor protein does not vary during the whole differentiation period. As the functional role of AT₂ receptors in adipose tissue is not known to date, further studies have to show if the AT₁-mediated inhibitory actions on adipose conversion are downregulated in differentiating cells through decreased AT₁/AT₂ receptor ratio.

Key words

Adipose Tissue - Renin-Angiotensin System - AT₁ - AT₂ - Western Blot - RT-PCR

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