Regulation of Small Ubiquitin-Like Modifier-1, Nuclear Receptor Coreceptor, Histone Deacetylase 3, and Peroxisome Proliferator-Activated Receptor-γ in Human Adipose Tissue

Background: This study investigated the regulation of peroxisome proliferator-activated receptor-gamma (PPAR gamma), the histone deacetylase 3 (HDAC3)-nuclear receptor coreceptor (NCoR) complex (a corepressor of transcription used by PPAR gamma), and small ubiquitin-like modifier-1 (SUMO-1) (a posttranslational modifier of PPAR gamma) in human adipose tissue and both adipocyte and macrophage cell lines. The objective was to determine whether there were alterations in the human adipose tissue gene expression levels of PPAR gamma, HDAC3, NCoR, and SUMO-1 associated either with obesity or with treatment of impaired glucose tolerance (IGT) subjects with insulin-sensitizing medications. Methods: We obtained subcutaneous adipose tissue biopsies from 86 subjects with a wide range of body mass index (BMI) and insulin sensitivity (S-I). Additionally, adipose tissue biopsies were obtained from a randomized subgroup of IGT subjects before and after 10 weeks of treatment with either pioglitazone or metformin. Results: The adipose mRNA levels of PPAR gamma, NCoR, HDAC3, and SUMO-1 correlated strongly with each other (P < 0.0001); however, SUMO-1, NCoR, and HDAC3 gene expression were not significantly associated with BMI or S-I. Pioglitazone increased SUMO-1 expression by 23% (P < 0.002) in adipose tissue and an adipocyte cell line (P < 0.05), but not in macrophages. Small interfering RNA (siRNA)-mediated knockdown of SUMO-1 decreased PPAR gamma, HDAC3, and NCoR in THP-1 cells and increased tumor necrosis factor-alpha (TNF-alpha) induction in response to lipopolysaccharide (LPS). Conclusions: These results suggest that the coordinate regulation of SUMO-1, PPAR gamma 1/2, HDAC3, and NCoR may be more tightly controlled in macrophages than in adipocytes in human adipose and that these modulators of PPAR gamma activity may be particularly important in the negative regulation of macrophage-mediated adipose inflammation by pioglitazone.