Abstract
OBJECTIVES: Our prior work demonstrated that dietary iron excess in early life results in iron overload in both liver and hippocampus in pre-weanling piglets. Herein, we aimed to identify metabolic processes altered by iron overload in liver and hippocampus. METHODS: Liver and hippocampal tissues collected from 21-day old nursing piglets receiving high (HI; 50 mg iron/d [Formula: see text] kg body weight), n = 5) or no oral iron supplementation (NI, n = 5) from birth to PD 21 were analyzed for non-targeted metabolomics, using gas chromatography mass spectrometry. Based on profiled changes in hippocampal metabolites, we further analyzed xanthine oxidase (XO), a rate limiting enzyme for purine degradation, for its mRNA, protein and enzyme activity by RT-qPCR, western blot, and ELISA. RESULTS: 108 and 126 metabolites were identified in hippocampus and liver, respectively. In comparison with NI, HI altered abundance of 15 metabolites in hippocampus (P < 0.05, q < 0.2). Myo-inositol and N-acetylaspartic acid, two abundant metabolites in the CNS with broad implications in neuronal function and myelination, were decreased in response to hippocampal iron overload. Seven metabolites involved in purine and pyrimidine metabolism (e.g., hypoxanthine, xanthine and beta-alanine) in hippocampus were modulated in a coordinated pattern by HI, implicating a shift from purine salvage towards degradation, governed by XO. In support of these findings, up-regulation of XO mRNA expression (2.3-fold, P < 0.05) and activity (fold/stats? ) was found in hippocampus but not in liver (P > 0.05). Despite overt iron loading, the hepatic metabolome remained stable (q > 0.2). CONCLUSIONS: Our findings suggest that iron overload increases hippocampal purine degradation via enhanced XO expression and activity, deleteriously altering tissue redox balance and ROS production. Purine salvage contributes to ATP production in the CNS, where a global shift from purine salvage to degradation due to HI may compromise energetics in the developing hippocampus. FUNDING SOURCES: UC Davis; NIFA.