The peroxisome proliferator activated receptor gamma (PPARgamma) is a transcription factor that plays a pivotal role in adipogenesis and adipocyte gene regulation. The overall goal of this proposal is to define the molecular mechanisms by which differences in PPARg activity, caused by different human PPARg mutations, impact on lipid, glucose, energy metabolism, cardiovascular function, and longevity. Human genetic studies have identified several natural PPARgamma variants (Pro12Ala, Pro115Gln, Pro495Leu and Val290Met) that affect both ligand-dependent (AF-2) and -independent (AF-1) activation functions of the receptor and that span a wide spectrum of PPARgamma activity. Unfortunately, human studies that address the relationship between differences in PPARgamma activity and the above complex traits have produced unequivocal answers, because known confounders, such as age, gender, genetic background and environmental factors such as diet, and exercise, obscure the in vivo effects of genetic variants that affect such complex traits. Therefore, we propose to study the impact of these mutations in mouse models where genetic and environmental factors can be well-controlled permitting careful analysis of gene-gene and gene-environment interactions.
The specific aims of this proposal are: (1) to generate mouse models on two distinct genetic backgrounds for the human PPARgamma Pro12Ala, Pro115Gln and Pro495Leu mutations, thus spanning a wide range of activity for this transcription factor; (2) to assess the impact of these muations on: i/lipid, glucose, and energy metabolism, ii/ cardiovascular function; and iii/ longevity; and (3) to determine the molecular changes induced by these mutations with the goal to identify the regulatory pathways that underpin the pleiotropic physiological effects of PPARgamma. Particular attention will be given to the impact of various dietary and exercise regimens on PPARgamma activity. The comprehensive nature and scientific breadth covered by this research requires a multidisciplinary approach, a condition that is met by the collaboration of specialists in cardiovascular and metabolic facets of mouse physiology and molecular genetics. Understanding the physiological and molecular impact of these PPARg muations may ultimately not only give us a better knowledge of fundamental PPARg activity, but may also point the way to the discovery of improved PPARgamma therapeutics.
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