^*Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil.

Correspondence: Fabio B. Lima Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, 1524 Prof Lineu Prestes Ave., 05508–900, Sao Paulo, SP, Brazil. E-mail: fabio@icb.usp.br

^*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 29 November 2006; Revised  0000; Accepted 6 February 2007.

Abstract

Objective: Salt restriction has been reported to increase white adipose tissue (WAT) mass in rodents. The objective of this study was to investigate the effect of different sodium content diets on the lipogenic and lipolytic activities of WAT.

Research Methods and Procedures: Male Wistar rats were fed on normal-sodium (NS; 0.5% Na⁺), high-sodium (HS; 3.12% Na⁺), or low-sodium (LS; 0.06% Na⁺) diets for 3, 6, and 9 weeks after weaning. Blood pressure (BP) was measured using a computerized tail-cuff system. At the end of each period, rats were killed and blood samples were collected for leptin determinations. The WAT from abdominal and inguinal subcutaneous (SC), periepididymal (PE) and retroperitoneal (RP) depots was weighed and processed for adipocyte isolation, rate measurement of lipolysis and d-[ U-¹⁴C] -glucose incorporation into lipids, glucose-6-phosphate dehydrogenase (G6PDH) and malic enzyme activity evaluation, and determination of G6PDH and leptin mRNA expression.

Results: After 6 weeks, HS diet significantly increased BP; SC, PE, and RP WAT masses; PE adipocyte size; plasma leptin concentration; G6PDH activity in SC WAT; and PE depots and malic activity only in SC WAT. The leptin levels correlated positively with WAT masses and adipocyte size. An increase in the basal and isoproterenol-stimulated lipolysis and in the ability to incorporate glucose into lipids was observed in isolated adipocytes from HS rats.

Discussion: HS diet induced higher adiposity characterized by high plasma leptin concentration and adipocyte hypertrophy, probably due to an increased lipogenic capacity of WAT.