Doctoral Dissertations

Date of Award

8-2012

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Comparative and Experimental Medicine

Major Professor

Michael B. Zemel

Committee Members

Karla Matteson, Jason Collier, Joseph Bartges

Abstract

Epigenetic modifications serve as a means of intermediate gene expression control and nutritional inputs may modify methylation patterns in regulatory regions of genes. Therefore, we proposed that specific nutrient availability of folate affects adipocyte development and metabolism through impacting the one-carbon cycle and subsequent DNA methylation patterns. Accordingly, we sought to determine if the methylation level of CpG islands could be influenced in adipocytes and if so, how this might affect gene signaling in mature adipocytes. We treated adipocytes with 0 to 0.9 millimolar [mM] folate, the methyl donor S-adenosylmethionine (SAMe) and the methylation inhibitor, 5-aza-2-deoxycitidine (2-DC) both during adipocyte differentiation and the maturation process. Lipogenesis was measured by accumulation of oil red O and lipolysis was quantified by a glycerol release assay. Methylated regions of adipocyte genomic DNA was evaluated using a methylation-specific antibody and hybridized against a Nimblegen whole genome CpG island array to identify targets for expression analysis RNA was obtained and genes involved in adipocyte differentiation, one-carbon metabolism, lipogenesis and lipolysis were quantified using RT-PCR. We found that low folate levels or inhibition by 2-DC decreased CpG methylation, thus increasing gene expression. Surprisingly SAMe performed similarly and decreased global CpG methylation. Low folate increased lipid accretion and subsequent lipolysis. Exposure to folate during the critical differentiation process had a greater impact on lipogenesis and lipolysis than exposure during the maturation.

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