2. Se: A brief history
• Originally studied for
toxicity
• Shown to be essential in
1957
• Present DRI of 55ug/d
3. Se as an Antioxidant: A Rush to
Judgement?
• Exudative diathesis in chickens – indicative of tissue damage:
•Free Radicals?
4. Se as an Antioxidant
Glutathione Peroxidase: the first known Selenoprotein
Selenocysteine at active site
Reaction:
2GSH + H2O2 → GS–SG + 2H2O
5. Se as an Antioxidant
Reaction of GPX fit within hypothesized scheme of antioxidant
protection
6. Se as an Antioxidant
• Selenium deficiency = signs of oxidative stress
• First selenoprotein = activity to reduce hydrogen peroxides
• Subsequent selenoproteins = have same reactive site:
(selenocysteine)
Selenium = Powerful Antioxidant
Need to fortify low and deficient popuulations
7. Selenium: A trace mineral with
antioxidant properties, selenium may
be useful in preventing arthritis and
other conditions, including age-related
blindness, cancers, cardiovascular
disease, cataracts and kidney
disease. You’ll get selenium from
whole-grain wheat products and
shellfish, such
as oysters and crab. A recent study raised the
possibility that taking selenium supplements might
increase the risk of developing diabetes, so talk to
your doctor before taking extra selenium. Getting
more selenium in your diet appears safe.
8. Selenium as an Antioxidant:
Current Thinking
• Other ideas as to GPX function:
• Cell signaling
• Se storage protein
• No protein positively associated with Se-
deficiency diseases
• No positive health benefits in Westernized
nations that have fortified
10. Selenium variation in
foods from different
geographical
areas and/or different
suppliers (Finley et
al. 1996)
Food Se (mg/100g)Food Se (mg/100g)
Corn masa mix, Maseca 4.7±0.6
Corn masa mix, Masa Harina 49.8±0.8
Flour white all-purpose, Gold Medal 15.9±0.9
Flour, white all-purpose, Pillsbury 39.9±1.3
Ground beef - North Dakota 33.6±0.7
Ground beef - SW Missouri 6.0±1.2
11. Selenium in pasta
USDA Nutrient Database
Food Selenium/serving
Spaghetti 20.2 µg Se
Whole-wheat spaghetti 23.7 µg Se
Macaroni 20.2 µg
Average selenium content of pasta analyzed
at Grand Forks Human Nutrition Center
20.5 µg/serving
12. Selenium in pasta
Italian pasta
Brand ug Se/100g
Venecia, angel hair 6.7±0.1
Davinci, fusilli 7.1±0.2
Venecia, linguini 5.7±1.0
Avg Italian brands 6.2
American pasta
Brand ug Se/100g
Market Pantry, spaghetti 139±7.0
Creamette, shells 102±11
Leonardo, shells 100±10
Avg American brands 57.4
13. Se Distribution in U.S. Soils
= Low Se
::::::::
:::: = Variable Se
::::::::
::::
… = Se toxicity
Kubota and
Allaway, 1972
Volcanic soils, low pH = Se deficient/low bioavailability
Jurrasic Shale = high Se
Weathering = Se released to soil
14. Meeting Se DRI with Se-enriched
Beef Amount of Se supplied by a 100g serving of
beef
0
50
100
150
200
250
Se,ug
Men Women U.S. avg ND grass-fed SD feedlot-fed
DRI 100 g Beef
15. Se Accumulation in Plants
• Wheat = Accumulates Se in direct relationship
to amount in soil
•Total conc. 0.01 -15 pp
• Se Accumulator = Accumulates Se well
beyond availability from soil
• Broccoli = up to 1500 ppm;
• Astragalus = up to 10,000 ppm
17. Selenium from broccoli does not activate rat
TR mRNA (A) or accumulate in muscle (B)
as readily as other food forms of Se.
0.0
0.5
1.0
1.5
0 0.5 1 1.5 2
Dietary Selenium (ug/g)
C
0 0.5 1 1.5 2
C1
C2
C3
C4
1
1.5
2
2.5
3
3.5
4
0 0.5 1 1.5 2
Dietary Selenium (ug/g)
BA
18. 250 kDa
98 kDa
64 kDa
50 kDa
30 kDa
16 kDa
6 kDa
MW Meat Broc Meat BrocMeat Broc Meat Broc
Liver Kidney Testis Plasma
Incorporation of 75Se from broccoli
or meat into selenoproteins
Selenium from meat incorporates into
selenoproteins
But Se from broccoli does not
22. Broccoli Extract SF
(mM)
Se
(mM)
0 SM 239 2 c 1.3 0.2 a
100 SM 157 3 b 35.4 1.3 b
1000 SM 41 3 a 354.0 5.6 c
Selenium fertilization decreases
sulforaphane content of broccoli
Robbins, Banuelos, Finley and Keck, 2004
23. Selenium fertilization alters
phenolic acid profile in broccoli
0 ppm Se
1000 ppm Se
1,2'-disinapoyl-2-
feruloyl gentiobiose
(11), 1-sinapoyl-2-
feruloyl gentiobiose
(8), 1,2,2'-trisinapoyl
gentiobiose (10) and
1,2-disinapoyl
gentiobiose (7), 1,2-
diferuloylgentiobiose
(9), and 3-O-caffeoyl-
quinic (neochlorogenic
acid) (2).
28. Consensus ARE Sequence (GST-A2)
5’-GTGACAAAGCA-3’
(-57) 5’-ATGACAAAGCA-3’(-46)
TR Promoter
Putative Antioxidant Response Element (ARE)
in TR Promoter
29. Effect of Sulforaphane on TR or QR
Transcription (luciferase promoter
construct)
0
10
20
30
40
50
Firefly/renillaratio
5.0 uM SF
2.0 uM SF
0.5 uM SF
0 uM SF
TR
30. Effect of Sulforaphane on TR or QR
Transcription (luciferase promoter
construct)
0
2
4
6
8
10
12
14
16
firefly/renillaratio
5.0 uM SF
2.0 uM SF
0.5 uM SF
0 uM SF
0
10
20
30
40
50
Firefly/renillaratio
5.0 uM SF
2.0 uM SF
0.5 uM SF
0 uM SF
TR
QR
31. Broccoli Extract SF
(mM)
Se
(mM)
0 SM 239 2 c 1.3 0.2 a
100 SM 157 3 b 35.4 1.3 b
1000 SM 41 3 a 354.0 5.6 c
Selenium fertilization decreases
sulforaphane content of broccoli
Robbins, Banuelos, Finley and Keck, 2004
32. ANOVA
Treatment P value
Effect of selenite 0.0009
Effect of SF 0.29
Interaction Se*SF 0.33
0
20
40
60
80
100
120GSH-PxActivity
mU/mgprot./min
C SF Se SF+Se
GPx activity in Hepa 1c1c7 cells
33. Se and SF synergistically
upregulate thioredoxin reductase
activity
0
10
20
30
40
50
60
TRActivity(mU/mgprot./min)
A
B B
C
Control 2uM Sel 2uM SF 2uM Se and
2uM SF
34. ANOVA
Treatment P value
Effect of selenite 0.69
Effect of SF <0.0001
Interaction Se*SF 0.14
0
100
200
300
400
500
600
QRActivity
nmolDPIP/mgprot./min
C SF Se SF+Se
Quinone reductase in Hepa 1c1c7 cells
36. Summary
• TR is transcriptionally regulated by an
ARE
• Transcriptional regulation increases TR
activity beyond the max induced by Se
• Sf from broccoli regulates TR activity
• Sf + Se = additive induction of TR
• Se antagonizes Sf accumulation in
broccoli and vice versa
37. Summary – Lessons learned
1. The real story is often more complex than
the theory
38. Summary – Lessons learned
1. The real story is often more complex than
the theory
2. Understanding nutritional chemistry is
essential
39. Summary – Lessons learned
1. The real story is often more complex than
the theory
2. Understanding nutritional chemistry is
essential
3. Understanding the soil/plant interaction is
essential
40. Summary – Lessons learned
1. The real story is often more complex than
the theory
2. Understanding nutritional chemistry is
essential
3. Understanding the soil/plant interaction is
essential
4. Enrichment of one nutrient may result in
unexpected interactions, both in the plant
and the animal that consumes it
41. Collaborators and partners
• Cindy Davis, NCI
• Joel Caton, NDSU
• Mark Roberge, UND
• Korry Hintze, NDSU
• Anna Keck, U. Ill.
• Allan Hovland, SD
• Phil Whanger, OSU
• Gary Banuelos,
USDA
• Mike Grusak, USDA
• Karl Wald, GFHNRC
• Eliz. Jeffery, U. Ill.
• Yi Feng, U. Louis.
