Arginine supplementation modulates pig plasma lipids, but not hepatic fatty acids, depending on dietary protein level with or without leucine
This study was conducted with a swine model to determine the safety of long-term dietary supplementation with l-arginine–HCl or l-arginine free base. Beginning at 30 days of age, pigs were fed a corn- and soybean meal-based diet (31.5 g/kg body weight/day) supplemented with 0, 1.21, 1.81 or 2.42 % l-arginine–HCl (Experiment 1) or with 0, 1, 1.5 or 2 % l-arginine (Experiment 2). The supplemental doses of 0, 1, 1.5, and 2 % l-arginine provided pigs with 0, 315, 473, and 630 mg l-arginine/kg body weight/day, respectively, which were equivalent to 0, 286, 430, and 573 mg l-arginine/kg body weight/day, respectively, in humans. At 121 days of age (91 days after initiation of supplementation), blood samples were obtained from the jugular vein of pigs at 1 and 4 h after feeding for hematological and clinical chemistry tests. Dietary supplementation with l-arginine increased plasma concentrations of arginine, ornithine, proline, albumin and reticulocytes, while reducing plasma concentrations of ammonia, free fatty acids, triglyceride, cholesterol, and neutrophils. l-Arginine supplementation enhanced protein gain and reduced white-fat deposition in the body. Other variables in standard hematology and clinical chemistry tests, serum concentrations of insulin, growth hormone and insulin-like growth factor-I did not differ among all the groups of pigs. These results indicate that dietary supplementation with l-arginine (up to 630 mg/kg body weight/day) is safe in pigs for at least 91 days. Our findings help guide clinical studies to determine the safety of long-term oral administration of l-arginine to humans.