Dietary selenomethionine exposure alters aerobic
metabolism and methionine catabolism in adult zebrafish
Jith K. Thomas*, Steve Wiseman, John P. Giesy and David M. Janz
*Toxicology Graduate Program, University of Saskatchewan,
Saskatoon, SK, Canada
SETAC 2012
Introduction
Essential but toxic at elevated concentrations
Point Sources - Mining, Coal based power production
Non point Sources- Agriculture, Urban runoff
Se IV
&
Se VI
Formation of Organoselenium
Plants &
Microbes
Nickel et al., 2009
Direct toxicity?
1
2
3
4
SeMet
Se IV- Selenite
Se VI - Selenate
SeMet - Selenomethionine
Modified from USGS
Introduction
Question
Does chronic dietary SeMet exposure alter repeat swimming
performance, metabolic rate and energy metabolism in adult
zebrafish?
Experimental Design
Adult Zebrafish
Control
3 μg Se/g
Nutrafin fish food
10 μg Se/g
30 μg Se/g
Nutrafin fish food spiked with Se in the form of L-SeMet
Fed 90 days (5% body mass/day)
No Swim
• Whole body Se concentration
Swim
Repeat Swim
• Swimming performance and oxygen
consumption
• Bioenergetics (whole body triglycerides
and glycogen)
• Transcript abundance of energy
metabolism enzymes
• Whole body lactate
• Bioenergetics (whole body triglycerides
and glycogen)
• Whole body lactate
Results & Discussion
ICP-MS Total Se Analysis
Nominal Diet
Food (μg Se/g)
Water (μg Se/L)
Fish (μg Se/g)
Control
1.29 ± 0.01
0.27 ± 0.08
1.62 ± 0.06
3 μg Se/g
3.44 ± 0.09*
0.32 ± 0.02
4.03 ± 1.00
10 μg Se/g
9.82 ± 0.24*
0.51 ± 0.02
7.57 ± 2.58
30 μg Se/g
27.46 ± 1.02*
1.07 ± 0.09*
11.15 ± 1.72*
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
Morphometric Analysis
Condition factor = [ body mass (g)/ length (mm)³ ] x 100,000
Measured Se (μg/g)
Total Length (mm)
Mass (g)
Condition Factor
1.3
38.07 ± 0.3
0.50 ± 0.02
0.90 ± 0.03
3.4
36.67 ± 0.6
0.49 ± 0.03
0.99 ± 0.03
9.8
37.52 ± 0.5
0.56 ±0.03
1.07 ± 0.07*
27.5
36.43 ± 0.6
0.55 ± 0.02
1.14 ± 0.04*
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
 Used Loligo Systems model mini swim tunnel respirometer
 Adopted Critical Swimming Speed (Ucrit) test
 Ucrit represented as body length per second (BL/s)
Ucrit = Ui + [Uii (Ti/Tii)]
Results & Discussion
Swim Performance
18
Swim
16
a
b
b
14
Ucrit (BL/s)
Repeat Swim
b
12
10
8
6
4
2
0
1.3
3.4
9.8
27.5
Dietary Se Concentration (g/g)
Ucrit – Critical Swimming Speed
BL/s – Body Length per second
Two way ANOVA followed by Holm-Sidak post hoc test (Factors: Dietary Se
treatment factor and swim challenge factor)
Results & Discussion
Oxygen Consumption
3500
1.3 g/g
3.4 g/g
9.8 g/g
27.5 g/g
MO2 (mg O2/kg/h)
3000
*
2500
*
2000
*
1500
*
1000
*
500
0.0
0.1
0.2
0.3
0.4
0.5
0.6
Swimming Speed (m/s)
Repeated Measures ANOVA followed by Holm-Sidak post hoc test
Results & Discussion
Cost of Transport
40
*
1.3g/g
3.4 g/g
9.8 g/g
μg/g
9.4
27.5 g/g
COT (J/kg/m)
35
30
*
25
*
*
20
15
10
0.1
0.2
0.3
0.4
0.5
0.6
Swimming Speed (m/s)
Repeated Measures ANOVA followed by Holm-Sidak post hoc test
Results & Discussion
Metabolic Capacities
3000
8
1.3 g/g
3.4 g/g
9.8 g/g
2000
6
27.5 g/g
* *
1500
4
1000
500
* * *
F-AS (AMR/SMR)
MO2 (mg O2/kg/h)
2500
2
0
0
SMR
SMR –Standard Metabolic Rate
AMR
AMR – Active Metabolic Rate
F-AS
F-AS – Factorial Aerobic Scope
One way ANOVA followed by Holm-Sidak post hoc test
Results & Discussion
Whole Body Triglycerides
16
b
No Swim
Triglycerides (mg/g)
14
12
Swim
a
10
8
b
Repeat Swim
a
6
4
2
0
1.3
3.4
9.8
27.5
Dietary Se Concentration (g/g)
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
1.5
1.0
0.5
*
*
9.8
27.5
0.0
MAT 1A Transcript Abundance
(Fold-change from Control)
HOAD Transcript Abundance
(Fold-change from Control)
1.5
1.0
0.5
*
*
0.0
1.3
3.4
Dietary Se Concentration (g/g)
HOAD – β-hydroxyacyl coenzyme A
dehydrogenase
1.3
3.4
9.8
27.5
Dietary Se Concentration (g/g)
MAT 1A – Methionine adenosyltransferase
1 alpha
One way ANOVA followed by Holm-Sidak post hoc test.
Results & Discussion
Whole Body Glycogen
6
No Swim
5
Swim
a
Glycogen (mg/g)
Repeat Swim
a
4
3
a
a
a
a
a a
2
b
b
b
b
1
0
1.3
3.4
9.8
27.5
Dietary Se Concentration (g/g)
Two way ANOVA followed by Holm-Sidak post hoc test (Factors: Dietary Se
treatment factor and swim status factor)
Results & Discussion
Whole Body Lactate
70
No Swim
Lactate (moles/g)
60
*
Repeat Swim
Swim
b
@
@
50
b
b
@
40
a
30
20
a
a
a
a
b
a
a
a
10
0
1.3
3.4
9.8
27.5
Dietary Se Concentration (g/g)
Two way ANOVA followed by Holm-Sidak post hoc test (Factors: Dietary Se
treatment factor and swim status factor)
Results & Discussion
Reduced Swimming Performance (Ucrit)
Greater Triglycerides Accumulation
• Impaired aerobic metabolism
• Down-regulation of HOAD and MAT
1A transcript abundance
• Impaired aerobic metabolism
Dietary SeMet
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 Members
Dr B. Blakley
Dr S. Niyogi
Dr P. Krone
Dr M. Pietrock
Dr M. Drew
Project Related Help
J. Hammel
B. Sarauer
THANK YOU