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