High expression of complement components in omental adipose tissue in obese men.
OBJECTIVE
Accumulation of visceral fat is recognized as a predictor of obesity-related metabolic disturbances. Factors that are predominantly expressed in this depot could mediate the link between visceral obesity and associated diseases.


METHODS
Paired subcutaneous and omental adipose tissue biopsies were obtained from 10 obese men. Gene expression was analyzed by DNA microarrays in triplicate and by real-time polymerase chain reaction. Serum C3 and C4 were analyzed by radial immunodiffusion assays in 91 subjects representing a cross section of the general population. Body composition was measured by computerized tomography.


RESULTS
Complement components C2, C3, C4, C7, and Factor B had higher expression in omental compared with subcutaneous adipose tissue ( approximately 2-, 4-, 17-, 10-, and 7-fold, respectively). In addition, adipsin, which belongs to the alternative pathway, and the classical pathway components C1QB, C1R, and C1S were expressed in both depots. Analysis of tissue distribution showed high expression of C2, C3, and C4 in omental adipose tissue, and only liver had higher expression of these genes. Serum C3 levels correlated with both visceral and subcutaneous adipose tissue in both men (r = 0.65 and p < 0.001 and r = 0.52 and p < 0.001, respectively) and women (r = 0.34 and p = 0.023 and r = 0.49 and p < 0.001, respectively), whereas C4 levels correlated with only visceral fat in men (r = 0.36, p = 0.015) and with both depots in women (visceral: r = 0.58, p < 0.001; and subcutaneous: r = 0.51, p < 0.001).


CONCLUSIONS
Recent studies show that the metabolic syndrome is associated with chronically elevated levels of several immune markers, some of which may have metabolic effects. The high expression of complement genes in intra-abdominal adipose tissue might suggest that the complement system is involved in the development of visceral adiposity and/or contributes to the metabolic complications associated with increased visceral fat mass.
Gabrielsson
Britt G
BG
Research Centre for Endocrinology and Metabolism, Sahlgrenska University Hospital, Göteborg University, Göteborg, Sweden.
Johansson
Jenny M
JM
Lönn
Malin
M
Jernås
Margareta
M
Olbers
Torsten
T
Peltonen
Markku
M
Larsson
Ingrid
I
Lönn
Lars
L
Sjöström
Lars
L
Carlsson
Björn
B
Carlsson
Lena M S
LM
D000273:Adipose Tissue / Q000737:chemistry*; D000328:Adult; D015922:Complement C1q / Q000235:genetics; D015923:Complement C1r / Q000235:genetics; D003173:Complement C1s / Q000235:genetics; D003175:Complement C2 / Q000235:genetics; D003176:Complement C3 / Q000235:genetics; D003181:Complement C4 / Q000235:genetics; D003184:Complement C7 / Q000235:genetics; D011415:Complement Factor B / Q000235:genetics; D011416:Complement Factor D; D003165:Complement System Proteins / Q000235:genetics*; D015870:Gene Expression; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D009852:Omentum; D016133:Polymerase Chain Reaction; D012697:Serine Endopeptidases / Q000235:genetics
D003175:Complement C2; D003176:Complement C3; D003181:Complement C4; D003184:Complement C7; D015922:Complement C1q; D003165:Complement System Proteins; D012697:Serine Endopeptidases; D015923:Complement C1r; D003173:Complement C1s; C493488:CFD protein, human; D011416:Complement Factor D; D011415:Complement Factor B