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Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions

Dietary Supplementation of L-Arginine and Conjugated Linoleic Acid Reduces Retroperitoneal Fat Mass and Increases Lean Body Mass in Rats^1,2

³ Intercollegiate Faculty of Nutrition and Department of Animal Science, Texas A&M University, College Station, TX 77843; and ⁴ National Institute of Animal Science, Rural Development Administration, Suwon 441-350, South Korea

We hypothesized that L-arginine and conjugated linoleic acid (CLA) would have additive effects in decreasing adiposity. Sprague Dawley rats were assigned to the following dietary groups (n = 6/group; 5 wk total): 1) control (2.55% L-alanine plus 1.5% canola oil); 2) arginine (1.25% L-arginine plus 1.5% canola oil); 3) CLA (2.55% L-alanine plus 1.5% CLA); and 4) arginine plus CLA (1.25% L-arginine plus 1.5% CLA). Supplemental amino acids were provided in drinking water and CLA was incorporated into the food pellets. Daily weight gain, food intake, arginine intake, and final body and eviscerated body weights were greater in rats fed supplemental CLA then in rats fed canola oil. The retroperitoneal adipose tissue:body weight ratio was less in rats fed supplemental CLA than in rats fed canola oil, but epididymal adipose tissue, liver, and soleus and extensor digitorum longus muscle weights were unaffected by arginine or CLA. CLA decreased epididymal adipose tissue concentrations of palmitoleic, oleic, and cis-vaccenic acid. CLA and arginine increased palmitate oxidation to CO₂ in epididymal adipose tissue in vitro relative to control rats. Glucose and palmitate incorporation into total lipids in epididymal adipose tissue was lower in rats fed supplemental arginine than in alanine-fed rats. Arginine increased plasma glycerol relative to alanine-fed rats and CLA and arginine independently decreased most serum essential amino acids and alanine, glutamate, glutamine, and ornithine. We conclude that CLA and arginine modulated adipose tissue metabolism by separate, but not additive, effects. Also, CLA and arginine may have depressed muscle protein turnover.

^* To whom correspondence should be addressed. E-mail: sbsmith{at}tamu.edu.

Manuscript received 13 November 2008. Initial review completed 26 December 2008. Revision accepted 27 April 2009.

Published online 13 May 2009.