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Title Oxidized soybean oil alters the expression of PPAR gamma and target genes in 3T3-L1 cells
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Degree MS
Discipline/Department Nutrition
Degree Level thesis
University/Publisher Georgia State University
Abstract <strong>Background: </strong> The typical western diet contains foods with modest amounts of lipid oxidation products. Previous work by us and others have demonstrated that mildly oxidized lipids promote a gain in fat mass while highly oxidized lipids decrease fat mass in rodents and triglyceride (TAG) accumulation in 3T3-L1 cells. Adipocyte differentiation is regulated by a key nuclear transcription factor known as PPARγ. <strong>Objective:</strong> To investigate if the alterations in triglyceride accumulation in 3T3-L1 cells pretreated with oxidized soy oil are due to 1) a change in PPARg DNA interactions 2) changes in the expression of SREBP-1c, PPARg, and/or its target genes. <strong>Main Methods: </strong> Confluent 3T3-L1 cells were pretreated for 24hours with 0.01% soy oil (SO) which was either unheated (unheated SO) or heated for 3, (3h-SO), 6 (6h-SO), or 9hours (9h-SO). The effect of 24hour soy oil exposure was assessed at several time points throughout the differentiation process. Alterations in PPARg DNA interaction was assessed using a PPARγ transcription factor assay kit while alterations in the expression of genes upstream and downstream of PPARγ was determined by RT-PCR. Primary and secondary products of oxidation within the SO were determined by spectrophotometry. <strong>Results:</strong> The 6hr-SO contained the greatest concentration of peroxides whereas both the 6hr-SO and 9hr-SO contained a significantly higher concentration of conjugated dienes and aldehydes.Nuclear extracts from 3T3-L1 cells pretreated with 6h-SO demonstrated the greatest reduction in PPARγ DNA binding. Compared to the unheated SO and mildly oxidized 3h-SO, cells treated with the 6h-SO had a significant reduction in SREBP-1c, PPARg, LPL, and GLUT4 expression occurring early in the differentiation process. Variations in the gene expression of 6hr-SO pretreated cells persisted within partially differentiated and mature adipocytes. <strong>Conclusions: </strong>Pre-treatment of preadipocytes with soy oil heated for ³ 6h greatly decreases the activity of PPARγ in the nucleus and adipogenic gene expression . These changes seen in early differentiation seem to correlate the best with the phenotype of reduced triglyceride accumulation seen in mature adipocytes.
Subjects/Keywords PPAR gamma; oxidized lipids; gene expression; adipocyte differentiation; triglyceride accumulation; 3T3-L1 cells
Contributors Meera Penumetcha; Nalini Santanam; Barbara Hopkins
Country of Publication us
Record ID oai:scholarworks.gsu.edu:nutrition_theses-1039
Repository georgia-state
Date Retrieved
Date Indexed 2020-09-25
Created Date 2012-11-15 08:00:00

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