Role and regulation of adrenomedullin signalling during adipogenic conversion of mouse 3T3-L1 preadipocytes

Abstract

Dramatic downregulation of Adrenomedullin (AM) mRNA and peptide secretion during the induction of differentiation in 3T3-L1 preadipocytes has been reported. This observation led us to hypothesize that increased levels of AM may have inhibitory effect on 3T3-L1 preadipocyte differentiation. We, therefore, examined the effect of application of exogenous AM and its specific receptor antagonist AM22-52 on adipogenic differentiation in this cell line. We also examined mRNA regulation of CRLR, which in combination with RAMP-1, and RAMP-2 or RAMP-3 proteins, forms CGRP and AM receptors respectively. Here we report that AM stimulation on day 2 of differentiation dose dependently inhibits mRNA expression of adipocyte markers PPARgamma2, leptin, and adipsin on day 7 differentiated adipocytes, and, that this effect can be, at least partially, inhibited by pre-treatment with AM22-52. We further report on the expression of CRLR mRNA and protein, and RAMP-1 and RAMP-2 mRNA regulation during 3T3-L1 differentiation. We also report striking upregulation of RAMP-3 mRNA expression during the first day of induction of differentiation.