The inhibitory effect of trans-10,cis-12 conjugated linoleic acid on sterol regulatory element binding protein-1 activation in bovine mammary epithelial cells involved reduced proteasomal degradation of insulin-induced gene-1

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dc.contributor.authorChen, Liangen
dc.contributor.authorLengi, Andrea J.en
dc.contributor.authorCorl, Benjamin A.en
dc.contributor.departmentDairy Scienceen
dc.date.accessioned2021-07-29T17:54:15Zen
dc.date.available2021-07-29T17:54:15Zen
dc.date.issued2021-07-15en
dc.date.updated2021-07-29T17:54:13Zen
dc.description.abstractTrans 10,cis-12 conjugated linoleic acid (t10,c12 CLA) is well recognized as a key CLA isomer responsible for the reduction in milk fat synthesis that leads to milk fat depression in dairy cows. Sterol regulatory element binding protein-1 (SREBP1) is a key transcription factor in bovine mammary gland coordinating transcription of the genes for fatty acid synthesis. SREBP1 activation requires the removal of insulin-induced gene-1 (Insig1) that serves as a repressor of SREBP1 in the endoplasmic reticulum (ER). We hypothesized that t10,c12 CLA reduced SREBP1 activation by delaying Insig1 degradation. In the present study, we used undifferentiated bovine mammary epithelial cells (MAC-T cells) and treated them with t10,c12 CLA for 6 h. We found that SREBP1 protein expression declined over 56% when cells were treated with 60 µM or greater concentration of t10,c12 CLA. Such inhibitory effects were also observed in the mRNA expression of SREBP1-regulated genes including SREBP1, fatty acid synthetase, stearoyl-CoA desaturase, and Insig1. Compared with no CLA group, 60 µM or higher concentration of t10,c12 CLA increased Insig1 protein expression over 2-fold in cells transfected with FLAG-tagged Insig1. This stimulatory effect was not specific to t10,c12 CLA but also other polyunsaturated fatty acids including cis-9,trans-11 CLA and linoleic acid. Oleic acid had no effect on Insig1 protein expression, whereas palmitic acid decreased Insig1 protein expression. Further investigation revealed that increased abundance of FLAG-Insig1 with t10,c12 CLA was due to the inhibition of the proteasomal degradation of Insig1. The t10,c12 CLA delayed the Insig1 decay when protein synthesis was blocked. Immunoprecipitation also confirmed that the interaction between ubiquitin-like domain-containing protein 8 and Insig1, the key step of removing Insig1 from ER and freeing SREBP1 for proteolytic processing, was inhibited by t10,c12 CLA, but not palmitic acid. These findings suggested that t10,c12 CLA played a role in regulating SREBP1 activation by reducing proteasomal degradation of Insig1. We concluded that stabilized Insig1 retained SREBP1 in the ER from activation, thus reducing lipogenic gene transcription.en
dc.description.versionAccepted versionen
dc.format.mimetypeapplication/pdfen
dc.identifier.doihttps://doi.org/10.3168/jds.2021-20544en
dc.identifier.eissn1525-3198en
dc.identifier.issn0022-0302en
dc.identifier.orcidCorl, Benjamin [0000-0002-6495-3279]en
dc.identifier.otherS0022-0302(21)00748-7 (PII)en
dc.identifier.pmid34275626 (pubmed)en
dc.identifier.urihttp://hdl.handle.net/10919/104442en
dc.language.isoenen
dc.publisherAmerican Dairy Science Associationen
dc.relation.urihttps://www.ncbi.nlm.nih.gov/pubmed/34275626en
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectconjugated linoleic aciden
dc.subjectinsulin-induced gene-1en
dc.subjectsterol regulatory element binding protein-1 activationen
dc.subjectDairy & Animal Scienceen
dc.subject0702 Animal Productionen
dc.subject0908 Food Sciencesen
dc.titleThe inhibitory effect of trans-10,cis-12 conjugated linoleic acid on sterol regulatory element binding protein-1 activation in bovine mammary epithelial cells involved reduced proteasomal degradation of insulin-induced gene-1en
dc.title.serialJournal of Dairy Scienceen
dc.typeArticle - Refereeden
dc.type.dcmitypeTexten
dc.type.otherJournal Articleen
dcterms.dateAccepted2021-05-31en
pubs.organisational-group/Virginia Techen
pubs.organisational-group/Virginia Tech/Agriculture & Life Sciencesen
pubs.organisational-group/Virginia Tech/Agriculture & Life Sciences/Dairy Scienceen
pubs.organisational-group/Virginia Tech/All T&R Facultyen
pubs.organisational-group/Virginia Tech/Agriculture & Life Sciences/CALS T&R Facultyen

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