Marini JC, Lee B, Garlick PJ. Ornithine restores ureagenesis capacity and mitigates hyperammonemia in Otc(spf-ash) mice.
J Nutr 2006;
136:1834-8. [PMID:
16772445 DOI:
10.1093/jn/136.7.1834]
[Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We showed that Otc(spf-ash) mice, a model of ornithine transcarbamylase deficiency, were able to sustain ureagenesis at the same rate as control mice, despite reduced enzyme activity, when a complete mixture of amino acids was provided. An unbalanced amino acid mixture, however, resulted in reduced ureagenesis and hyperammonemia. To study the effect of ornithine supplementation [316 micromol/(kg.h)] on urea and glutamine kinetics in conscious Otc(spf-ash) mice under a glycine-alanine load [6.06 mmol/(kg.h)], a multiple tracer infusion protocol ([(13)C(18)O]urea, [5-(15)N]glutamine, [2,3,3,4,4 D(5)]glutamine and [ring-D(5)] phenylalanine) was conducted. Ornithine supplementation increased ureagenesis [3.18 +/- 0.88 vs. 4.56 +/- 0.51 mmol/(kg.h), P < 0.001], reduced plasma ammonia concentration (1125 +/- 621 vs. 193 +/- 94 micromol/L, P < 0.001), and prevented acute hepatic enlargement (P < 0.006) in Otc(spf-ash) mice. Ornithine supplementation also increased [96 +/- 20 vs. 120 +/- 16 micromol/(kg.h), P < 0.001] the transfer of (15)N from glutamine to urea, to values observed in the control mice [123 +/- 17 micromol/(kg.h)]. De novo amido-N glutamine flux was higher [1.57 +/- 0.37 vs. 3.04 +/- 0.86 mmol/(kg.h); P < 0.001] in Otc(spf-ash) mice, but ornithine supplementation had no effect (P < 0.56). The flux of glutamine carbon skeleton was affected by both genotype (P < 0.0001) and by ornithine (P 0. 036). In conclusion, ornithine supplementation restored ureagenesis, mitigated hyperammonemia, prevented liver enlargement, and normalized the transfer of (15)N from glutamine to urea. These data strongly suggest that ornithine has the potential for the biochemical correction of OTCD in Otc(spf-ash) mice.
Collapse