Inflammation is associated with a decrease of lipogenic factors in omental fat in women

Obesity is characterized by systemic low-grade inflammation in which adipose tissue, especially the omental depot, is thought to play a key role. We have previously shown that inflammation impairs 3T3-L1 preadipocyte cell line differentiation. To explore whether this interaction also takes place in vivo, the expression of several genes related to inflammation and adipocyte differentiation was assessed in human samples. Paired adipose tissue biopsies (from omental and subcutaneous depots) were obtained from 24 women: 6 lean normoglycemic and 18 obese volunteers with different glycemic states (normoglycemic, glucose-intolerant, or type 2 diabetic). The expression levels of CD14, IL-18, leptin, adiponectin, sterol regulatory element binding transcription factor 1 (SREBP1), peroxisome proliferator-activated receptor gamma (PPAR gamma), pre-B-cell colony enhancing factor 1 (PBEF1) (or visfatin), glycerol-3-phosphate dehydrogenase 1 (soluble) (GPD1), lipoprotein lipase (LPL), fatty acid binding protein 4, adipocyte (FABP4), and hypoxia-inducible factor 1 alpha were determined by quantitative real-time PCR. CD14 and IL-18 were overexpressed in omental adipose tissue compared with the subcutaneous depot, irrespective of the subject's obesity or diabetes status. A significant decrease of LPL, GPD1, and leptin expression was observed in omental tissue, and an inverse correlation between expression of CD14 and IL-18 and that of PPAR gamma, LPL, and FABP4 was observed. The underexpression of omental lipogenic markers was more accentuated in the presence of glucose intolerance. Furthermore, adiponectin and SREBP1 expression was also significantly decreased in omental tissue of type 2 diabetic patients. PBEF1 and HIF1 alpha expression remained comparable in all samples. Therefore, in humans, inflammation is increased in the omental depot, as evidenced by CD14 and IL-18 expression. In this localization, the inflammatory state is associated with a decreased expression of lipogenic markers, which is more pronounced in diabetic subjects.