1. ^*Institut National de la Santé et de la Recherche Médicale U145, Nice, France;
2. ^†Unité de Recherches sur les Obésités, Institut National de la Santé et de la Recherche Médicale U586, Institut Louis Bugnard, Centre Hospitalier Universitaire de Toulouse, Université Paul Sabatier, Toulouse, France;
3. ^‡Hope Heart Program, Benaroya Research Institute at Virginia Mason, Seattle, Washington.
4. ^§These authors contributed equally to this work.
5. ^¶Current address: INSERM U540, Metabolism and Cancer Laboratory, Montpellier, France.
6. Current address: INSERM U597, Nice, France.

Correspondence: Emmanuel Van Obberghen Institut National de la Santé et de la Recherche Médicale U145, IFR 50, Avenue de Valombrose, 06107 Nice Cedex 2, France. E-mail: vanobbeg@unice.fr

^*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 5 October 2005; Accepted 13 July 2006.

Abstract

Objective: To explore the regulation of secreted protein acidic and rich in cysteine (SPARC) expression and its role in adipose tissue.

Research Methods and Procedures: We studied the regulation of SPARC expression in transgenic mice expressing the human 3 and 2 adrenergic receptors on a murine 3 adrenergic receptor null background that became obese under a high-fat diet mainly as a result of adipose tissue hyperplasia. Furthermore, we analyzed its expression in human adipose tissue and its regulation during adipocyte differentiation.

Results: SPARC protein in adipose tissue was increased in obese transgenic mice compared with control mice, indicating that SPARC expression was associated with adipose tissue hyperplasia. Both SPARC mRNA and protein were detected in human adipose tissue. Comparing adipocytes and vascular stroma, we found that SPARC expression was mainly associated with the adipocyte fraction. Consistent with this, SPARC transcript increased during differentiation of human primary preadipocytes. 3T3-L1 preadipocytes showed an increase in SPARC expression in differentiated cells but with biphasic expression during the process. After induction in committed cells, SPARC mRNA and protein levels declined as differentiation began and returned to elevated levels in fully differentiated adipocytes.

Discussion: SPARC expression correlated with adipose tissue hyperplasia and adipogenesis. Therefore, SPARC seems to play a role in adipose tissue physiology as it is involved in growth and differentiation.