Volume 87, Issue 5, May (2002), pp. 427-434 © The Author 2002
doi:10.1079/BJN2002570

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Dietary fat source regulates ob gene expression in white adipose tissue of rats under hyperphagic feeding

Víctor M. Rodríguez¹, Catalina Picó², María P. Portillo^1,*, M. Teresa Macarulla¹ and Andreu Palou^2
1Department of Nutrition and Food Science, University of País Vasco, Paseo de la Universidad 7, 01006 Vitoria, Spain
²Department of Biologia Fonamental i Ciènces de la Salut, Universitat de les Illes Balears, Carretera Valldemossa Km 7.5,
07071 Palma de Mallorca, Spain

 (Received 6 August 2001–Revised 2 January 2002–Accepted 19 January 2002)

This work was designed to investigate the effect of different lipid sources on ob gene expression and serum leptin levels in rats with two different feeding protocols: (1) free access to food; or (2) energy-controlled feeding. Male Wistar rats were fed diets containing 40 % energy as fat (olive oil, sunflower oil or beef tallow), for 4 weeks. In Expt 1 rats had free access to food, and in Expt 2 rats were fed a controlled amount of food (16 g/d, equivalent to 300 kJ/d). Insulin and leptin were determined by ELISA and ob mRNA by Northern blot. When rats had free access to food, ob mRNA levels were higher in animals fed either olive oil or sunflower oil than in those fed beef tallow. In marked contrast with feeding ad libitum, no differences were found among dietary fat groups in rats fed energy-controlled diets. When both feeding protocols were compared, free access to food induced an increased expression of ob mRNA in perirenal and/or epididymal adipose tissues from rats fed either olive oil or sunflower oil, but not from rats fed beef tallow. Dietary lipid type did not induce modifications in serum leptin concentrations. A tendency to higher serum leptin levels was observed more in rats with free access to food than in rats fed energy-controlled feeding. No differences were found in insulin levels. Dietary fat type importantly affects ob mRNA expression in rat white adipose tissue under hyperphagic conditions. Further study is needed in order to elucidate the mechanism underlying this effect.

Keywords:
gene: Leptin: Dietary fat: Adipose tissue