Gene expression profiling in subcutaneous, visceral, and epigastric adipose tissues of patients with extreme obesity

OBJECTIVE: The goal of the present study was to identify differences in gene expression between SAT, VAT, and EAT depots in Class III severely obese individuals. DESIGN: Human subcutaneous (SAT) and visceral (VAT) adipose tissues exhibit differential gene expression profiles. There is little information, however, about the other proximal white adipose tissue, epigastric (EAT) in terms of its function and contribution to metabolism. SUBJECTS AND METHODS: Using RNA from adipose biospecimens obtained from Class III severely obese patients undergoing open Roux-en-Y gastric bypass surgery, we compared gene expression profiles between SAT, VAT, and EAT, using microarrays validated by real time quantitative PCR. RESULTS: The three depots were found to share 1,907 genes. VAT had the greatest number of genes [66] expressed exclusively in this depot, followed by SAT [23], and then EAT [14]. Moreover, VAT shared more genes with EAT [65] than with SAT [38]. Further analyses using ratios of SAT/EAT, VAT/EAT, and SAT/VAT, identified specific as well as overlapping networks and pathways of genes representing dermatological diseases, inflammation, cell cycle and growth, cancer, and development. Targeted analysis of genes playing a role in adipose tissue development and function, revealed that Peroxisome proliferator-activated receptor Gamma Coactivator 1-alpha (PGC1-α) that regulates the precursor of the hormone Irisin (FNCD5), were abundantly expressed in all three fat depots, along with fibroblast growth factors (FGF) FGF1, FGF7, and FGF10, whereas, FGF19 and FGF21 were undetectable. CONCLUSIONS: These data indicate that EAT has more in common with VAT suggesting similar metabolic potential. The human epigastric adipose depot could play a significant functional role in metabolic diseases and should be further investigated.