Resistin is more abundant in liver than adipose tissue and is not up-regulated by lipopolysaccharide.
BACKGROUND
Resistin is an adipokine correlated with inflammatory markers and is predictive for cardiovascular diseases. There is evidence that serum resistin levels are elevated in obese patients; however, the role of resistin in insulin resistance and type 2 diabetes remains controversial.


OBJECTIVE
We addressed the question of whether inflammation may induce expression of resistin in organs involved in regulation of total body energy metabolism, such as liver and adipose tissue (AT).


METHODS
Human liver tissue, sc AT, and omentum were cultured in the absence/presence of lipopolysaccharide (LPS). The resistin and cytokine mRNA and protein expression levels were determined by real-time PCR, ELISA, and Multiplex Technology, respectively. The localization of resistin in human liver was analyzed by immunohistochemistry.


RESULTS
Resistin gene and protein expression was significantly higher in liver than in AT. Exposure of human AT and liver tissue in culture to LPS did not alter resistin concentration; however, concentrations of IL-1beta, IL-6, and TNFalpha were significantly increased in these tissues. In liver, resistin colocalizes with markers for Kupffer cells, for a subset of endothelial and fibroblast-like cells.


CONCLUSIONS
High level of resistin gene and protein expression in liver compared to AT implies that resistin should not be considered only as an adipokine in humans. LPS-induced inflammation does not affect resistin protein synthesis in human liver and AT. This suggests that elevated serum resistin levels are not indicative for inflammation of AT or liver in a manner similar to known inflammatory markers such as IL-1beta, IL-6, or TNFalpha.
Szalowska
Ewa
E
Department of Medical Biomics, University of Groningen, University Medical Centre Groningen, Antonius Deusinglaan 1, Groningen, The Netherlands. e.szalowska@med.umcg.nl
Elferink
Marieke G L
MG
Hoek
Annemiek
A
Groothuis
Geny M M
GM
Vonk
Roel J
RJ
D000273:Adipose Tissue / Q000378:metabolism*; D000293:Adolescent; D000328:Adult; D002097:C-Reactive Protein / Q000235:genetics; D016207:Cytokines / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D007150:Immunohistochemistry; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008099:Liver / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009852:Omentum / Q000378:metabolism; D052243:Resistin / Q000032:analysis / Q000235:genetics*; D015854:Up-Regulation
D016207:Cytokines; D008070:Lipopolysaccharides; C499624:RETN protein, human; D052243:Resistin; D002097:C-Reactive Protein