Contribution of mesothelial cells in the expression of inflammatory-related factors in omental adipose tissue of obese subjects.
OBJECTIVE
The objective of this study was to determine the contribution of mesothelial cells, present in human omental adipose tissue (OAT) but not in the subcutaneous depot (SAT), on the expression of inflammation-related factors.


METHODS
Comparison of the expression profiles of inflammation-related genes in mesothelial cells with those in the adipocyte-enriched (AEF) and stromal vascular fractions (SVF) and localization of interleukin-18 (IL-18) expression in adipose depots.


METHODS
Eleven obese Caucasian female subjects undergoing gastric bypass surgery (body mass index: 43.6+/-1.3 kg/m(2); age: 41.6+/-2.3 years).


METHODS
The expression profiles of cytokine and chemokine-related genes in mesothelial cells and in cell fractions prepared from OAT were assessed by the microarray technique. The differential expression of IL-18 was confirmed by real-time PCR and the protein was localized in adipose depots by immunohistochemistry.


RESULTS
Microarray data analysis demonstrated that, of the 16 cytokine and chemokine-related genes that were upregulated in mesothelial cells compared with the AEF, IL-18 was the cytokine with the highest differential expression. IL-18 expression was similar in mesothelial cells and the SVF. In both SAT and OAT, IL-18 was immunolocalized in neutrophils and mast cells, but not in macrophages nor adipocytes. This cytokine was also detected in mesothelial cells in OAT. This additional source of expression may explain the higher IL-18 expression levels in OAT than SAT (+5.9-fold).


CONCLUSIONS
By their capacity to express inflammatory-related factors, and in particular the proinflammatory cytokine IL-18 in OAT, mesothelial cells appear as a new player in the process of low-grade inflammation associated with obesity.
Darimont
C
C
Nestlé Research Center, Department of Nutrition and Health, Lausanne, Switzerland. christian.darimont@rdls.nestle.com
Avanti
O
O
Blancher
F
F
Wagniere
S
S
Mansourian
R
R
Zbinden
I
I
Leone-Vautravers
P
P
Fuerholz
A
A
Giusti
V
V
Macé
K
K
D000273:Adipose Tissue / Q000166:cytology / Q000378:metabolism*; D000328:Adult; D004847:Epithelial Cells / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007249:Inflammation / Q000235:genetics; D020382:Interleukin-18 / Q000235:genetics / Q000378:metabolism*; D046228:Microarray Analysis; D009765:Obesity / Q000235:genetics / Q000378:metabolism*; D009852:Omentum / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050507:Subcutaneous Fat, Abdominal / Q000378:metabolism*
D020382:Interleukin-18