1. ^*Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland
2. ^†Department of Emergency and Organ Transplantation, Section of Internal Medicine, Endocrinology and Metabolic Diseases, University of Lausanne, Lausanne, Switzerland
3. ^‡Section of Surgery and Liver Transplantation University Medical School, Bari, Italy
4. ^§Department of Internal Medicine, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland
5. ^¶Nestlé Research Center, Lausanne, Switzerland

Correspondence: Susanna Cotecchia Department of Pharmacology and Toxicology, Faculty of Biology and Medicine, University of Lausanne, Rue du Bugnon 27, CH-1005 Lausanne, Switzerland. E-mail: Susanna.Cotecchia@unil.ch

^*The costs of publication of this article were defrayed, in part, by the payment of page charges. This article must, therefore, be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Received 21 March 2006; Revised  0000; Accepted 29 January 2007.

Abstract

Objective: Atrial natriuretic peptide (ANP) is a secretory hormone displaying diuretic, natriuretic, and vasorelaxant activities. Recently, its lipolytic activity has been reported. Since the expression of ANP in adipose tissue has not been documented, we used real-time reverse transcriptase polymerase chain reaction (RT-PCR) to investigate the expression of ANP in human adipose tissue and preadipocytes.

Research Methods and Procedures: RNA was extracted from the human adipose tissue of severely obese premenopausal women as well as from human preadipocytes. For human preadipocytes, two cell systems were investigated: the human preadipose immortalized (Chub-S7) cells, a well-characterized human preadipose cell line, and primary preadipocytes derived from the stromal vascular fraction of the human adipose tissue. We measured the mRNA of ANP, of corin (a transmembrane serine protease involved in the conversion of pro-ANP to ANP) and of uncoupling protein 2 (UCP2; a control gene known to be ubiquitously expressed). The expression of ANP was also investigated using immunofluorescence and radioimmunoassay in Chub-S7 cells and human primary preadipocytes in culture.

Results: Our results indicate that ANP and corin are expressed at the mRNA level in human adipose tissue and preadipocytes. Immunofluorescence experiments demonstrated that pro-ANP was expressed in Chub-S7 cells. In addition, ANP secretion could be measured in Chub-S7 cells and human primary preadipocytes in culture. Rosiglitazone, a selective peroxisome proliferator-activated receptor type (PPAR-) agonist promoting adipocyte differentiation, was found to modulate both ANP expression and secretion in preadipocytes.

Discussion: Our findings suggest the existence of an autocrine/paracrine system for ANP in the human adipose tissue whose implications in lipolysis and cardiovascular function need to be further explored.