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Peroxisome proliferator-activated receptor gamma (PPARgamma) is a member of the PPAR subfamily of nuclear hormone receptors. In rodents and humans, expression of PPARgamma is predominantly found in adipose tissue where it regulates adipocyte differentiation and the expression of multiple adipocyte genes. The primary aim of this work was to clone the porcine PPARgamma cDNA and examine the regulation of gene expression in porcine subcutaneous adipose tissue. The porcine PPARgamma gene encodes a 1.8-kb mRNA transcript and shares 99, 96 and 97% amino acid sequence identity to the human, mouse and cow PPARgamma molecules, respectively. Both isoforms of PPARgamma (gamma1 and gamma2) are highly expressed in porcine adipose tissue. The gamma2 isoform is expressed in low abundance in porcine spleen, whereas the gamma1 isoform is highly expressed in spleen and lung and at a low abundance in several other tissues. Western blot analysis confirmed a high level of PPARgamma protein expression in porcine adipose tissue compared to other tissues. Both caloric restriction and fasting significantly reduced PPARgamma2 but not gamma1 mRNA and PPARgamma protein abundance in subcutaneous adipose tissue compared to ad-libitum fed controls. We provide the first evidence that PPARgamma is abundantly expressed in porcine subcutaneous adipose tissue, and that expression is regulated by caloric intake. Thus, PPARgamma may play an important role in adipogenesis and hormone action in porcine adipocytes.

The postnatal increase in skeletal alpha-actin (Sk-alpha-Act) synthesis in pigs is due, in part, to increased transcription. To characterize the factors responsible for its transcriptional regulation, we have cloned and determined the nucleotide sequence of a 5.2-kb HindIII genomic DNA fragment which contains the complete coding region of Sk-alpha-Act distributed over seven exons, plus 1.9 kb of 5' flanking region and 0.5 kb of 3' flanking sequence. The major transcription start point (tsp) of Sk-alpha-Act was determined to be 840 bp 5' to the ATG start codon by primer extension and RNase protection analysis. To demonstrate that the Sk-alpha-Act promoter was functional, L6 myoblasts, C2C12 myoblasts and HeLa cells were transfected with a construct (pPSKAFL-CAT) linking the 5' Sk-alpha-Act promoter to the chloramphenicol acetyltransferase reporter gene (cat). Cell lysates from L6 myoblasts, L6 myotubes, C2C12 myoblasts, C2C12 myotubes, and HeLa cells were analyzed for CAT activity. CAT activity was detected only in C2C12 myotubes. Thus, the porcine Sk-alpha-Act promoter is regulated in a developmental and cell-type specific manner.