Altered regulation of adipogenesis with respect to disease processes
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Date
2017
Authors
Davies, Stephanie Jane
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Publisher
University College Cork
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Abstract
Dysregulation of adipose tissue metabolism is associated with multiple metabolic disorders. One such disease, known as Dunnigan-type familial partial lipodystrophy (FPLD2) is characterised by defective fat metabolism and storage. FPLD2 is caused by a specific subset of mutations in the LMNA gene. The mechanisms by which LMNA mutations lead to the adipose specific FPLD2 phenotype have yet to be determined. Previous work employed RNA-Seq analysis to assess the effects of wild-type (WT) and mutant (R482W) LMNA on the expression profile of differentiating 3T3-L1 mouse preadipocytes and identified over 200 transcripts whose expression was altered. Four of these genes namely ITM2A, IGFBP5, PTPRQ and WNT6 were selected for detailed investigation using the 3T3-L1 in-vitro adipogenesis model. Preliminary investigations carried out identified a complex endogenous IGFBP5 expression profile in 3T3-L1 differentiation, with IGFBP5 over-expression and knockdown leading to inhibited and enhanced differentiation, respectively. Investigation into the effects of LMNA over-expression on IGFBP5 yielded conflicting results and further analysis is required to elucidate the mechanisms regulating IGFBP5 expression in adipogenesis. In this thesis ITM2A is identified as a novel modulator of adipogenesis and results show that endogenous ITM2A expression is transiently down-regulated during induction of 3T3-L1 differentiation. ITM2A over-expression was seen to moderately inhibit differentiation of 3T3-L1 preadipocytes while shRNA mediated knockdown of ITM2A significantly enhanced 3T3-L1 differentiation. Investigation of PPARĪ³ levels indicate that this enhanced adipogenesis is mediated through the stabilization of the PPARĪ³ protein at specific time points during differentiation. The results demonstrate that ITM2A knockdown is sufficient to rescue the inhibitory effects of LMNA WT and R482W mutant over-expression on 3T3-L1 differentiation and indicate a novel therapeutic approach for FPLD2.
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Keywords
Adipogenesis , Lipodystrophy , FPLD2
Citation
Davies, S. J. 2017. Altered regulation of adipogenesis with respect to disease processes. PhD Thesis, University College Cork.