ABSTRACT: 2,4-dinitrotoluene (2,4-DNT), a nitroaromatic used in industrial and explosive manufacturing processes, is known to contaminate artillery ranges, demilitarization areas and munitions manufacturing facilities. Previous transcriptomic and lipidomic studies identified energy metabolism as a principle biochemical process affected by 2,4-DNT where up-stream effects on PPAR? signaling were hypothesized as themolecular initiating event for these effects. Here, the validity of this hypothetical adverse outcome pathway (AOP) was assessed by testing the hypothesis that 2,4-DNT-induced perturbations in PPAR? signaling and resultant downstream deficits in energy metabolism, especially from lipids, would result in organism-level impacts on exercise endurance. PPAR? knock-out (-/-) and wild-type (WT) mice were exposed for 14 days to vehicle or 2,4-DNT at a dose (134 mg/kg/day) that did not exhibit overt systemic toxicity. Mice performed an exercise challenge (forced swim) 1 day after the last dose. 2,4-DNT decreased swim times in WT and PPAR? (-/-) mice, but the effect was significantly less in PPAR? (-/-) mice indicating the critical of PPAR? in mediating 2,4-DNT-induced energy metabolism deficits. 2,4-DNT caused down-regulation of transcripts involved in fatty acid metabolism, gluconeogenesis, triacylglycerol catabolism, and the pentose phosphate pathway, and 2,4-DNT treated wild-type mice had decreased serum trigylcerides and increased serum glucose versus 2,4-DNT treated PPAR? (-/-) mice. Our results support the hypothesis that 2,4-DNT perturbs PPAR? signaling as a molecular initiating event therefore impacting energy metabolism, especially lipid metabolism, producing reduced exercise endurance in mice. RNA was isolated from liver tissue of vehicle or 2,4-DNT treated wild-type or PPAR? (-/-) mice (n=6) and RT-PCR performed to analyze genes involved in fatty acid metabolism
