Obesity is rapidly becoming a major problem in the United States and throughout the world. Polygenic models of obesity are most similar to human obesity because few humans are genetically obese due to a mutation in a single gene. Numerous studies have selected mice for body size and growth rate as models for selection of agriculturally important species. One series of selection experiments produced lines of mice having differing epididymal fat (EF) masses but similar body weights. These mice may be used as a model for adipose deposition without confounding the effects of body weight. One method of studying these mice is to examine gene expression. Expression of thousands of genes can be investigated at one time using microarrays. We used microarrays and real-time RT-PCR to compare gene expression between the high epididymal (HE) and low fat (LF) lines of mice, which have dissimilar EF mass but similar body weights. Microarray analysis identified 19 genes with differential expression between the HE and LF lines of mice with 5 of these genes differentially expressed in both liver and EF tissues. We found differential regulation of genes known to play a role in glucose uptake and lipid metabolism. In addition, we identified a differentially expressed gene, <I>solute carrier family 22 member 4</I>, located within the confidence interval of a quantitative trait loci associated with EF mass, making it a positional candidate. Furthermore, we identified a linked group of three genes (<I>Sortilin 1</I>, <I>guanine nucleotide binding protein alpha inhibiting 3</I>, and <I>selenium-binding protein 2</I>) on <I>Mus musculus</I> chromosome 3 (MMU3), which may represent a genomic ?hot spot? for genes associated with EF mass. In this study, differential expression of several genes not previously associated with obesity or adipose deposition were identified and may represent new targets for further research. Another aspect of obesity currently being investigated is anti-obesity compounds. One such compound is <I>trans</I>-10, <I>cis</I>-12-conjugated linoleic acid (CLA). CLA has been reported to reduce body weight and adipose mass in many species. Numerous studies have reported an increase in size, cytoplasmic vacuolization, and fatty acid synthesis in liver of CLA fed mice. The livers of CLA fed mice gain mass due to lipid accumulation; however, the precise molecular mechanisms are unknown. To elucidate these mechanisms, we examined the fatty acid composition, histology, and gene expression profile of liver from a polygenic obese line of mice fed CLA. Using a Periodic acid-Schiff stain, histological evidence suggests that glycogen content is unchanged in the liver of the CLA fed mouse implying that hepatic cytoplasmic vacuolization is due to increased lipid content. Microarray analysis identified 1393 genes differentially expressed at a nominal P-value of 0.01. Following Bonferroni correction and excluding lowly expressed transcripts, 198 genes were identified as being differentially expressed with 17 genes having ≥2 fold change. Real-time RT-PCR showed up regulation of <I>acylglycerol-3-phosphate O-acyltransferase 2</I> and <I>diacylglycerol O-acyltransferase 2</I> in CLA fed mice, both necessary for triglyceride biosynthesis. Expression of <I>B-cell leukemia/lymphoma 6</I>, a nuclear transcriptional repressor, and <I>signal transducer and activator of transcription 5B</I>, a transcription factor, were shown to be greater in the liver of CLA fed mice. Both genes are associated with immunoregulation. Comparing real-time RT-PCR to microarray data suggest a Bonferroni correction to microarray data is necessary in order to eliminate false positive data. Further verification of microarray results is needed to validate microarray data after a Bonferroni correction.
| Identifer | oai:union.ndltd.org:NCSU/oai:NCSU:etd-08072007-120016 |
| Date | 17 August 2007 |
| Creators | Ceddia, Ryan Patrick |
| Contributors | Melissa S. Ashwell, Eugene J. Eisen, Christopher M. Ashwell, Jack Odle |
| Publisher | NCSU |
| Source Sets | North Carolina State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://www.lib.ncsu.edu/theses/available/etd-08072007-120016/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dis sertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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