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This Article Full Text Full Text (PDF) All Versions of this Article: 295/5/R1376    most recent 90467.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Iemura-Inaba, C. Articles by Matsuoka, H. Search for Related Content PubMed PubMed Citation Articles by Iemura-Inaba, C. Articles by Matsuoka, H.

APPETITE, OBESITY, AND DIGESTION

Role of adrenomedullin system in lipid metabolism and its signaling mechanism in cultured adipocytes

Departments of ¹Hypertension and Cardiorenal Medicine, and ²Laboratory Medicine, Dokkyo Medical University, Mibu, Tochigi, Japan; and ³Department of Medicine and ⁴Research Institute, National Cardiovascular Center, Fujishirodai, Suita, Osaka, Japan

Submitted 2 June 2008 ; accepted in final form 4 August 2008

We investigated the levels of adrenomedullin (AM) system during the process of preadipocyte differentiation and its role in lipid metabolism and cellular signaling mechanism in differentiated adipocytes. We cultured rat preadipocytes and measured the following during the process of differentiation: two molecular forms of AM in the culture medium using a specific immunoradiometric assay and gene expression of AM and its receptor component using RT-PCR analysis. In differentiated adipocytes, we measured the effects of AM on the intracellular cAMP level, lipolysis, glucose incorporation, and the protein levels. Two molecular forms of AM were secreted into the medium, and the AM-mature/AM-total ratio was increased after 6 days of differentiation. Cultured rat preadipocytes highly expressed the genes of AM and its receptor components at day 1, and they increased at day 10. Administration of AM to preadipocytes increased the number of Oil Red O-positive adipocytes and spectrophotometric absorbance of Oil Red O. AM dose dependently increased cAMP level and lipolysis, and its effect was blocked by CGRP(8-37). Isoproterenol increased lipolysis, and AM had additive effects on isoproterenol-induced lipolysis. KT5720 and U0126 significantly inhibited the AM-induced lipolysis, whereas KT5720, but not U0126, significantly inhibited the isoproterenol-induced lipolysis. AM increased glucose incorporation and its effect was blocked by wortmannin. Western blot analysis revealed that AM increased phospho PKA, ERK, and Akt. These results indicate that AM and its receptor component are highly expressed in cultured adipocytes and may play a role in lipid metabolism via a different signaling pathway.

adipocyte; calcitonin receptor like receptor; receptor activity-modifying proteins; lipolysis