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Selenoproteins in the Bovine Mammary Gland. Regulation of mRNA and Protein Expression

Bruzelius, Katharina LU (2007)
Abstract (Swedish)
Popular Abstract in Swedish

Selen är ett essentiellt näringsämne som behövs för att upprätthålla flera viktiga funktioner i kroppen, huvudsakligen genom en speciell grupp proteiner som heter selenoproteiner. Det finns minst 25 stycken olika selenoproteiner i människan och flera av dem skyddar kroppen mot oxidation medan vissa andra sköter regleringen av sköldkörtelhormoner. Många selenoproteiners egenskaper är fortfarande dock helt eller delvis okända. Även om selen är giftigt i allt för höga doser har selenbrist kopplats till flera sjukdomar, bland annat en hjärtsjukdom i Kina, men också till ökad risk för vissa sorters cancer och försämrat immunförsvar. Flera selenbristsjukdomar finns även hos boskap. Seleninnehållet i... (More)
Popular Abstract in Swedish

Selen är ett essentiellt näringsämne som behövs för att upprätthålla flera viktiga funktioner i kroppen, huvudsakligen genom en speciell grupp proteiner som heter selenoproteiner. Det finns minst 25 stycken olika selenoproteiner i människan och flera av dem skyddar kroppen mot oxidation medan vissa andra sköter regleringen av sköldkörtelhormoner. Många selenoproteiners egenskaper är fortfarande dock helt eller delvis okända. Även om selen är giftigt i allt för höga doser har selenbrist kopplats till flera sjukdomar, bland annat en hjärtsjukdom i Kina, men också till ökad risk för vissa sorters cancer och försämrat immunförsvar. Flera selenbristsjukdomar finns även hos boskap. Seleninnehållet i livsmedel och foder beror på hur mycket selen som finns i jorden där maten odlas eller föds upp. Jordmånen i Sverige är relativt fattig på selen och det genomsnittliga intaget hos vuxna är något lägre än rekommenderat. Runt en femtedel av selenintaget hos vuxna kommer från mjölkprodukter, och andelen är ännu högre hos barn.



Syftet med den här studien var att undersöka vilka selenoproteiner som finns i juvervävnad hos kor och i en juvercellinje, MAC-T, samt att undersöka hur olika faktorer påverkar genuttryck och proteinuttryck. Den här informationen kan sedan användas för att få en bättre förståelse för hur selen och andra komponenter i maten, samt hormoner påverkar selenoproteiner i juver- och bröstvävnad och vad det har för inverkan på vävnadens fysiologi och även på mjölkproduktionen.



mRNA, som är budbäraren mellan gener och proteintillverkning, hittades i juvervävnad från kor för glutationperoxidas (GPx) 1, 3 och 4, selenoprotein P och tioredoxin reduktas 1 (TrxR 1). Alla förutom GPx 3 hittades även i juvercellinjen MAC-T, vilket är intressant eftersom GPx 3 är det enda selenoprotein som hittills har hittats i mjölk. Mätningar visade också att mRNA-uttryck och aktivitet av vissa selenoproteiner påverkas av selenstatus, medan andra inte berörs. Effekter av retinsyra, även kallad vitamin A-syra, samt hormonerna insulin, hydrokortison och prolaktin på genuttryck och enzymaktivitet i MAC-T celler studerades också. Behandling med retinsyra ökade genuttrycket av GPx 1 och TrxR 1, insulin minskade uttrycket av selenoprotein P och, i kombination med hydrokortison, ökade uttrycket av GPx 1. Produktionen av övriga selenoproteiner i denna cellinje studerades genom att odla cellerna med radioaktivt 75Se, och därefter separera de olika proteinerna genom tvådimensionell gelelektrofores för att sedan detektera de radioaktiva proteinerna. Detta visade att MAC-T celler tillverkar ett stort antal selenoproteiner och att det vanligaste var GPx 1. Även retinsyras effekt på andra proteiner som tillverkas i MAC-T celler undersöktes och då framkom att retinsyra minskade halterna av flera proteiner som förknippas med cancer och två proteiner som har kopplats till utveckling av bröstkörteln och till mjölkproduktion.



Sammanfattningsvis visade den här studien att ett antal selenoproteiner tillverkas i juvervävnad och juverceller från kor. Den visade också att uttryck av vissa av dessa selenoproteiner påverkas av selenstatus, retinsyra och olika hormoner. (Less)
Abstract
Selenium is a micronutrient that is essential for many important life processes due to the action of the specific selenoproteins containing one or more of the 21st amino acid, selenocysteine. Twenty-five selenoprotein genes have been found in the human genome but the function of many of them is not yet known. Some of the characterised selenoproteins have, however, antioxidant properties. Selenium deficiency or low selenium status has been linked to various diseases in humans such as certain types of cancer, and a number of selenium deficiency symptoms are known in farm animals. When the concentration of selenium in the soil is low, as it is in Sweden, selenium supplements are often added to cow's feed to increase the levels of selenium in... (More)
Selenium is a micronutrient that is essential for many important life processes due to the action of the specific selenoproteins containing one or more of the 21st amino acid, selenocysteine. Twenty-five selenoprotein genes have been found in the human genome but the function of many of them is not yet known. Some of the characterised selenoproteins have, however, antioxidant properties. Selenium deficiency or low selenium status has been linked to various diseases in humans such as certain types of cancer, and a number of selenium deficiency symptoms are known in farm animals. When the concentration of selenium in the soil is low, as it is in Sweden, selenium supplements are often added to cow's feed to increase the levels of selenium in cow tissues which also leads to higher levels in milk. In the Swedish diet, cow's milk accounts for about one fifth of the selenium intake of adults.



The general aims of the present study were to investigate which selenoproteins are found in bovine mammary cells and tissue, to find out how mRNA and protein expression are regulated, and to explore the possible role of selenoproteins in milk formation and mammary gland physiology. Biomarkers of selenium status and mechanisms of action of selenium supplements in cancer prevention were also reviewed.



Messenger RNA (mRNA) was demonstrated for selenoprotein P, thioredoxin reductase 1 and for glutathione peroxidase (GPx) 1, 3 and 4 in bovine mammary tissue, and all but GPx 3 were also found to be expressed in the bovine mammary cell line MAC-T. It was also found that selenium status is an important regulator of selenoprotein activity and expression in bovine mammary tissue and cells, but that other factors are also involved. The effect of the vitamin A metabolite retinoic acid (RA) and the lactogenic hormones prolactin, insulin and hydrocortisone on mRNA expression of selenoproteins in MAC-T cells was also investigated. RA was found to increase the expression of GPx 1 and thioredoxin reductase 1. It was also found that insulin decreased the expression of selenoprotein P, and a combination of insulin and hydrocortisone increased the expression of GPx 1. The selenoproteome of MAC-T cells was studied by labelling with radioactive 75Se and examination by 2D electrophoresis, autoradiography and MALDI-TOF. MAC-T cells were shown to express a number of selenoproteins, the cytosolic GPx 1 being the most abundant. The effects of RA on the selenoprotein levels in the cell line were also studied. The concentration of 75Se in total cell protein was reduced in cells cultured with RA compared with control cells, and the opposite was seen in extracellular proteins. RA treatment of MAC-T cells also led to changes in the levels of several non-selenoproteins in the cells, for example, decreased levels of proteins associated with cancer, such as heat shock proteins 70:8 and 27:1, and keratin 8. Other proteins decreased in the MAC-T cells by RA may be associated with mammary gland development and milk formation.



In summary, this study shows that a number of selenoproteins could be detected in bovine mammary tissue and cells. It was also demonstrated that the expression of these proteins can be affected by selenium status, retinoic acid and hormones. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Professor Sunde, Roger, College of Agricultural & Life Sciences, University of Wisconsin-Madison, USA
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Livsmedelsteknik, Food and drink technology, metabolism, Biokemi, Metabolism, Biochemistry, Naturvetenskap, milk, Natural science, cancer, prolactin, insulin, hydrocortisone, retinoic acid, MAC-T, northern blot, two-dimensional electrophoresis, bovine mammary gland, selenium, selenoprotein
pages
169 pages
publisher
Pure and Applied Biochemistry, Lund University
defense location
Lecture hall C, at the Centre for Chemistry and Chemical Engineering, Getingevägen 60, Lund University Faculty of Engineering.
defense date
2007-09-07 13:15
ISBN
978-91-7422-167-1
language
English
LU publication?
yes
id
38826e65-8ec3-414d-940b-4d1c2df407bf (old id 548908)
date added to LUP
2007-10-09 09:49:12
date last changed
2016-09-19 08:45:15
@phdthesis{38826e65-8ec3-414d-940b-4d1c2df407bf,
  abstract     = {Selenium is a micronutrient that is essential for many important life processes due to the action of the specific selenoproteins containing one or more of the 21st amino acid, selenocysteine. Twenty-five selenoprotein genes have been found in the human genome but the function of many of them is not yet known. Some of the characterised selenoproteins have, however, antioxidant properties. Selenium deficiency or low selenium status has been linked to various diseases in humans such as certain types of cancer, and a number of selenium deficiency symptoms are known in farm animals. When the concentration of selenium in the soil is low, as it is in Sweden, selenium supplements are often added to cow's feed to increase the levels of selenium in cow tissues which also leads to higher levels in milk. In the Swedish diet, cow's milk accounts for about one fifth of the selenium intake of adults.<br/><br>
<br/><br>
The general aims of the present study were to investigate which selenoproteins are found in bovine mammary cells and tissue, to find out how mRNA and protein expression are regulated, and to explore the possible role of selenoproteins in milk formation and mammary gland physiology. Biomarkers of selenium status and mechanisms of action of selenium supplements in cancer prevention were also reviewed.<br/><br>
<br/><br>
Messenger RNA (mRNA) was demonstrated for selenoprotein P, thioredoxin reductase 1 and for glutathione peroxidase (GPx) 1, 3 and 4 in bovine mammary tissue, and all but GPx 3 were also found to be expressed in the bovine mammary cell line MAC-T. It was also found that selenium status is an important regulator of selenoprotein activity and expression in bovine mammary tissue and cells, but that other factors are also involved. The effect of the vitamin A metabolite retinoic acid (RA) and the lactogenic hormones prolactin, insulin and hydrocortisone on mRNA expression of selenoproteins in MAC-T cells was also investigated. RA was found to increase the expression of GPx 1 and thioredoxin reductase 1. It was also found that insulin decreased the expression of selenoprotein P, and a combination of insulin and hydrocortisone increased the expression of GPx 1. The selenoproteome of MAC-T cells was studied by labelling with radioactive 75Se and examination by 2D electrophoresis, autoradiography and MALDI-TOF. MAC-T cells were shown to express a number of selenoproteins, the cytosolic GPx 1 being the most abundant. The effects of RA on the selenoprotein levels in the cell line were also studied. The concentration of 75Se in total cell protein was reduced in cells cultured with RA compared with control cells, and the opposite was seen in extracellular proteins. RA treatment of MAC-T cells also led to changes in the levels of several non-selenoproteins in the cells, for example, decreased levels of proteins associated with cancer, such as heat shock proteins 70:8 and 27:1, and keratin 8. Other proteins decreased in the MAC-T cells by RA may be associated with mammary gland development and milk formation.<br/><br>
<br/><br>
In summary, this study shows that a number of selenoproteins could be detected in bovine mammary tissue and cells. It was also demonstrated that the expression of these proteins can be affected by selenium status, retinoic acid and hormones.},
  author       = {Bruzelius, Katharina},
  isbn         = {978-91-7422-167-1},
  keyword      = {Livsmedelsteknik,Food and drink technology,metabolism,Biokemi,Metabolism,Biochemistry,Naturvetenskap,milk,Natural science,cancer,prolactin,insulin,hydrocortisone,retinoic acid,MAC-T,northern blot,two-dimensional electrophoresis,bovine mammary gland,selenium,selenoprotein},
  language     = {eng},
  pages        = {169},
  publisher    = {Pure and Applied Biochemistry, Lund University},
  school       = {Lund University},
  title        = {Selenoproteins in the Bovine Mammary Gland. Regulation of mRNA and Protein Expression},
  year         = {2007},
}