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Journal of Lipid Research, Vol. 49, 98-106, January 2008
Copyright © 2008 by American Society for Biochemistry and Molecular Biology

Conjugated linoleic acid fails to worsen insulin resistance but induces hepatic steatosis in the presence of leptin in ob/ob mice

Angela A. Wendel, Aparna Purushotham, Li-Fen Liu and Martha A. Belury¹

Department of Human Nutrition, Ohio State University, Columbus, OH 43210

Published, JLR Papers in Press, September 28, 2007.

¹ To whom correspondence should be addressed. e-mail: belury.1{at}osu.edu

Conjugated linoleic acid (CLA) induces insulin resistance preceded by rapid depletion of the adipokines leptin and adiponectin, increased inflammation, and hepatic steatosis in mice. To determine the role of leptin in CLA-mediated insulin resistance and hepatic steatosis, recombinant leptin was coadministered with dietary CLA in ob/ob mice to control leptin levels and to, in effect, negate the leptin depletion effect of CLA. In a 2 x 2 factorial design, 6 week old male ob/ob mice were fed either a control diet or a diet supplemented with CLA and received daily intraperitoneal injections of either leptin or vehicle for 4 weeks. In the absence of leptin, CLA significantly depleted adiponectin and induced insulin resistance, but it did not increase hepatic triglyceride concentrations or adipose inflammation, marked by interleukin-6 and tumor necrosis factor- mRNA expression. Insulin resistance, however, was accompanied by increased macrophage infiltration (F4/80 mRNA) in adipose tissue. In the presence of leptin, CLA depleted adiponectin but did not induce insulin resistance or macrophage infiltration. Despite this, CLA induced hepatic steatosis. In summary, CLA worsened insulin resistance without evidence of inflammation or hepatic steatosis in mice after 4 weeks. In the presence of leptin, CLA failed to worsen insulin resistance but induced hepatic steatosis in ob/ob mice.

Supplementary key words adipokine • lipodystrophy • inflammation

Abbreviations: CCL2, CC chemokine ligand 2; CLA, conjugated linoleic acid; CON, control diet; HOMA, homeostasis model assessment; IL-6, interleukin-6; ITT, insulin tolerance test; PPAR, peroxisome proliferator-activated receptor-; SREBP-1, sterol-regulatory element binding protein-1; TNF-, tumor necrosis factor-; WAT, epididymal white adipose tissue

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