Dietary selenomethionine exposure alters aerobic metabolism and methionine catabolism in adult zebrafish SETAC 2012 Jith K. Thomas*, Steve Wiseman, John P. Giesy and David M. Janz *Toxicology Graduate Program, University of Saskatchewan, Saskatoon, SK, Canada

Point Sources - Mining, Coal based power production Non point Sources- Agriculture, Urban runoff Introduction Plants & Microbes SeMet Modified from USGS Formation of Organoselenium Se IV & Se VI Se IV- Selenite Se VI - Selenate SeMet - Selenomethionine 4 Essential but toxic at elevated concentrations Direct toxicity? Nickel et al., 2009

IntroductionQuestion Does chronic dietary SeMet exposure alter repeat swimming performance, metabolic rate and energy metabolism in adult zebrafish?

Adult Zebrafish Control3 μg Se/g10 μg Se/g30 μg Se/g Nutrafin fish food spiked with Se in the form of L-SeMetNutrafin fish food Whole body Se concentration Bioenergetics (whole body triglycerides and glycogen) Transcript abundance of energy metabolism enzymes Whole body lactate Swimming performance and oxygen consumption Bioenergetics (whole body triglycerides and glycogen) Whole body lactate No Swim Swim Repeat Swim Experimental Design Fed 90 days (5% body mass/day)

Results & Discussion Nominal DietFood (μg Se/g)Water (μg Se/L)Fish (μg Se/g) Control1.29 ± ± ± μg Se/g 3.44 ± 0.09 * 0.32 ± ± μg Se/g 9.82 ± 0.24 * 0.51 ± ± μg Se/g ± 1.02 * 1.07 ± 0.09 * ± 1.72 * ICP-MS Total Se Analysis One way ANOVA followed by Holm-Sidak post hoc test. Data are mean ± S.E.M. *, Significantly different from the control group (p< 0.05).

Results & Discussion Measured Se (μg/g)Total Length (mm)Mass (g)Condition Factor ± ± ± ± ± ± ± ± ± 0.07 * ± ± ± 0.04 * Condition factor = [ body mass (g)/ length (mm)³ ] x 100,000 Morphometric Analysis One way ANOVA followed by Holm-Sidak post hoc test. Data are mean ± S.E.M. *, Significantly different from the control group (p< 0.05).

Swim Performance  Adopted Critical Swimming Speed (U crit ) test  Used Loligo Systems model mini swim tunnel respirometer U crit = U i + [U ii (T i /T ii )]  U crit represented as body length per second (BL/s)

Results & Discussion Swim Performance U crit – Critical Swimming Speed Two way ANOVA followed by Holm-Sidak post hoc test (Factors: Dietary Se treatment factor and swim challenge factor) BL/s – Body Length per second

Results & Discussion Oxygen Consumption Repeated Measures ANOVA followed by Holm-Sidak post hoc test

Results & Discussion Cost of Transport Repeated Measures ANOVA followed by Holm-Sidak post hoc test 9.8 μg/g

Results & Discussion Metabolic Capacities One way ANOVA followed by Holm-Sidak post hoc test SMR –Standard Metabolic RateAMR – Active Metabolic Rate F-AS – Factorial Aerobic Scope

Results & Discussion Whole Body Triglycerides Two way ANOVA followed by Holm-Sidak post hoc test (Factors: Dietary Se treatment factor and swim status factor)

Results & Discussion Transcript Abundance of HOAD and MAT 1A in Liver One way ANOVA followed by Holm-Sidak post hoc test. HOAD – β-hydroxyacyl coenzyme A dehydrogenase MAT 1A – Methionine adenosyltransferase 1 alpha

Results & Discussion Whole Body Glycogen Two way ANOVA followed by Holm-Sidak post hoc test (Factors: Dietary Se treatment factor and swim status factor)

Results & Discussion Whole Body Lactate Two way ANOVA followed by Holm-Sidak post hoc test (Factors: Dietary Se treatment factor and swim status factor)

Results & Discussion Dietary SeMet Reduced Swimming Performance (U crit ) Impaired aerobic metabolism Greater Triglycerides Accumulation Down-regulation of HOAD and MAT 1A transcript abundance Impaired aerobic metabolism Impaired Methionine Catabolism Down-regulation of MAT 1A transcript abundance

Conclusions  Environmentally relevant dietary SeMet exposure can reduce swimming performance and alter aerobic metabolism in fish and such effects could impact fitness survivability of wild fish inhabiting in selenium contaminated aquatic ecosystems  SeMet-induced down-regulation of HOAD and MAT 1A transcript abundance could be related to greater accumulation of triglycerides  Greater condition factor of fish fed greater concentrations of SeMet suggesting that condition factor is not a good determinant of assessing overall fish health after dietary SeMet exposure

Acknowledgements Committee MembersDr B. Blakley Dr S. Niyogi Dr P. Krone Dr M. Pietrock Dr M. Drew Project Related HelpJ. Hammel B. Sarauer