Dietary selenomethionine exposure alters aerobic metabolism and methionine catabolism in adult zebrafish
SETAC 2012SETAC 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
1
2
3
Introduction
Plants & Microbes
SeMet
Modified from USGS
Formation of OrganoseleniumSe IV
&Se VI
Se IV- Selenite
Se VI - Selenate
SeMet - Selenomethionine
4
Essential but toxic at elevated concentrations
Direct toxicity?
Nickel et al., 2009
Introduction
Question
Does chronic dietary SeMet exposure alter repeat swimming performance, metabolic rate and energy metabolism in adult zebrafish?
Adult Zebrafish
Control 3 μg Se/g 10 μg Se/g 30 μg Se/gNutrafin 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 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*
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
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*
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 (Ucrit) test
Used Loligo Systems model mini swim tunnel respirometer
Ucrit = Ui + [Uii (Ti/Tii)]
Ucrit represented as body length per second (BL/s)
Ucr
it (
BL
/s)
0
2
4
6
8
10
12
14
16
18
3.4 9.8 27.5
ba
b
b
1.3
Dietary Se Concentration (g/g)
Repeat SwimSwim
Results & Discussion Swim Performance
Ucrit – 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
Swimming Speed (m/s)
0.0 0.1 0.2 0.3 0.4 0.5 0.6
MO
2 (m
g O
2/kg
/h)
500
1000
1500
2000
2500
3000
3500
1.3 g/g3.4 g/g9.8 g/g27.5 g/g
*
*
*
*
*
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
Swimming Speed (m/s)
0.1 0.2 0.3 0.4 0.5 0.6
CO
T (
J/kg
/m)
10
15
20
25
30
35
40
1.3g/g3.4 g/g9.4 g/g27.5 g/g
*
* * *
9.8 μg/g
F-A
S (
AM
R/S
MR
)
0
2
4
6
8
MO
2 (m
g O
2/kg
/h)
0
500
1000
1500
2000
2500
3000
SMR AMR F-AS
***
* *
1.3 g/g
27.5 g/g
9.8 g/g
3.4 g/g
Results & Discussion Metabolic Capacities
One way ANOVA followed by Holm-Sidak post hoc test
SMR –Standard Metabolic Rate AMR – Active Metabolic Rate F-AS – Factorial Aerobic Scope
Tri
gly
ceri
de
s (
mg
/g)
0
2
4
6
8
10
12
14
16
a
b
a
b
1.3 3.4 9.8 27.5
Dietary Se Concentration (g/g)
No Swim
Swim
Repeat Swim
Results & Discussion Whole Body Triglycerides
Two way ANOVA followed by Holm-Sidak post hoc test (Factors: Dietary Se treatment factor and swim status factor)
HO
AD
Tra
nsc
rip
t A
bu
nd
ance
(Fo
ld-c
han
ge
fro
m C
on
tro
l)
0.0
0.5
1.0
1.5
1.3 3.4 9.8 27.5
*
Dietary Se Concentration (g/g)
*
MA
T 1
A T
ran
scri
pt
Ab
un
dan
ce(F
old
-ch
ang
e fr
om
Co
ntr
ol)
0.0
0.5
1.0
1.5
* *
1.3 3.4 9.8 27.5
Dietary Se Concentration (g/g)
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 Adehydrogenase
MAT 1A – Methionine adenosyltransferase 1 alpha
Gly
cog
en (
mg
/g)
0
1
2
3
4
5
6No Swim
Swim
Repeat Swim
1.3 3.4 9.8 27.5
Dietary Se Concentration (g/g)
a a
aa a
a
a
a
bb
bb
Results & Discussion Whole Body Glycogen
Two way ANOVA followed by Holm-Sidak post hoc test (Factors: Dietary Se treatment factor and swim status factor)
0
10
20
30
40
50
60
70
bb
aaa
a
a
a
aa
b
b@
@
*
1.3 3.4 9.8 27.5
Dietary Se Concentration (g/g)
Lac
tate
(
mo
les/
g) @
Repeat SwimNo Swim Swim
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 (Ucrit)
• 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 Members Dr B. BlakleyDr S. NiyogiDr P. KroneDr M. PietrockDr M. Drew
Project Related Help J. Hammel B. Sarauer