Full Papers

Metabolism and Metabolic Studies

Trans-10, cis-12-conjugated linoleic acid reduces the hepatic triacylglycerol content and the leptin mRNA level in adipose tissue in obese Zucker fa/fa rats

Oddrun A. Gudbrandsen^a1 c1, Enrique Rodríguez^a2, Hege Wergedahl^a1, Sverre Mørk^a3, Janne E. Reseland^a4, Jon Skorve^a1, Andreu Palou^a2 and Rolf K. Berge^a1

^a1 Institute of Medicine, Haukeland University Hospital, University of Bergen, N-5021 Bergen, Norway

^a2 Laboratory of Molecular Biology, Nutrition and Biotechnology (Nutrigenomics), University of the Balearic Islands (UIB), CIBER Fisiopatología Obesidad y Nutrición (CB06/03), Instituto de Salud Carlos III, 07122 Palma de Mallorca, Spain

^a3 Department of Pathology, Gade Institute, Haukeland University Hospital, University of Bergen, N-5021 Bergen, Norway

^a4 Department of Nutrition, Faculty of Medicine, Institute of Basic Medical Sciences, University of Oslo, POB 1046, N-0316 Oslo, Norway

Abstract

Conjugated linoleic acid (CLA) isomers have been reported to reduce body weight and beneficially affect glucose metabolism in animals, but the results are inconsistent and seem to depend on animal model and type of CLA isomer. In the present study, feeding male Zucker fa/fa rats diets supplemented with 1 % trans-10, cis-12-CLA for 10 d reduced the liver TAG content without improving the overall adiposity, and enhanced hepatic mitochondrial and peroxisomal β-oxidation. The increased carnitine palmitoyltransferase (CPT)-I activity and mRNA level as well as the increased n-3:n-6 PUFA ratio in liver suggest that trans-10, cis-12-CLA increased the hepatic β-oxidation by stimulation of PPARα. The reduced hepatic TAG content may be partly due to lower activity of stearoyl-CoA desaturase, as the ratios of 18 : 1n-9:18 : 0 and 16 : 1n-7:16 : 0 were reduced in liver. Trans-10, cis-12-CLA increased the CPT-I mRNA in retroperitoneal white adipose tissue (WAT), and increased uncoupling protein-2 mRNA in epididymal and inguinal WAT depots. Leptin mRNA level was decreased in all examined WAT depots, implying reduced insulin sensitivity. The resistin mRNA level was increased in all WAT depots, whereas adiponectin mRNA was reduced in inguinal and retroperitoneal WAT. The present results suggest that dietary supplementation with trans-10, cis-12-CLA may increase the catabolism of lipids in liver and adipose tissue. Moreover, we provide new data suggesting that trans-10, cis-12-CLA modulates the expression of resistin and adiponectin inversely in adipose tissue. Hence, the present results suggest that trans-10, cis-12-CLA may have some beneficial effects on lipid metabolism and adiposity but possibly reduces insulin sensitivity.

(Received May 25 2008)

(Revised January 05 2009)

(Accepted January 09 2009)

(Online publication March 19 2009)

Key Words:

• Conjugated linoleic acid;
• Hepatic steatosis;
• β-Oxidation;
• Obese Zucker rats

Correspondence:

^c1 Corresponding author: Dr Oddrun A. Gudbrandsen, fax +47 55973115, email oddrun.gudbrandsen@med.uib.no

Footnotes

Abbreviations: CLA, conjugated linoleic acid; CPT, carnitine palmitoyltransferase; eWAT, epididymal white adipose tissue; HMG, 3-hydroxy-3-methylglutaryl; iWAT, inguinal white adipose tissue; L-CPT, liver carnitine palmitoyltransferase; rWAT, retroperitoneal white adipose tissue; Tris, 2-amino-2-hydroxymethyl-propane-1, 3-diol; UCP, uncoupling protein; WAT, white adipose tissue