Protein array reveals differentially expressed proteins in subcutaneous adipose tissue in obesity

Many adipokines, inflammatory cytokines, and other proteins produced by adipose tissue have been shown to be involved in the development of obesity-related insulin resistance. Nevertheless, new factors that play an important role in these processes are still emerging. Therefore, we screened the level of 120 different proteins in biopsies of subcutaneous adipose tissue (ScAT) of lean and obese subjects.

All studied volunteers (12 obese with BMI >30 and 6 lean with BMI <25 kg/m(2)) were young, clinically healthy, and drug-naive males with normal glucose tolerance. The ScAT was obtained by a needle biopsy from the umbilical region. Protein levels were assessed in adipose tissue lysates using protein arrays; mRNA levels were determined with the aid of real-time reverse transcription-polymerase chain reaction (RT-PCR).

The obese subjects had higher fasting plasma glucose (although within the normal range) and insulin levels, increased high sensitivity C-reactive protein (hsCRP) in circulation, and decreased in vivo insulin action. Using the protein array technique, it was shown that of 120 proteins measured, 27 showed higher levels (leptin, HGF, EGF-R, FGF-6, IGF-1sR, Fas/Apo-1, ENA-78, PARC, lymphotactin, HCC-4, IL-10, IL-1a, IL-1R1, IL-1R4, IL-12p70, angiopoietin-2, Axl, Dtk, MIF, MIP-1a, -1b, -3b, MSP-a, osteoprotegerin, TECK, TIMP-1, -2) and only one (RANTES) showed a lower level in ScAT of obese subjects when compared with the lean controls (p < 0.05). The real-time RT-PCR confirmed the results of protein arrays for leptin, MIF, MIP-1a, TIMP-2, adiponectin, IL-6, and TNF-alpha but not for RANTES.

To our knowledge, this is the first protein array data on a very early dysregulation of ScAT protein levels in insulin-resistant obese, but apparently healthy, subjects with normal glucose tolerance.