Fetuin-A influences vascular cell growth and production of proinflammatory and angiogenic proteins by human perivascular fat cells.
OBJECTIVE
Fetuin-A (alpha2-Heremans-Schmid glycoprotein), a liver-derived circulating glycoprotein, contributes to lipid disorders, diabetes and cardiovascular diseases. In a previous study we found that perivascular fat cells (PVFCs) have a higher angiogenic potential than other fat cell types. The aim was to examine whether fetuin-A influences PVFC and vascular cell growth and the expression and secretion of proinflammatory and angiogenic proteins, and whether TLR4-independent pathways are involved.


METHODS
Mono- and co-cultures of human PVFCs and endothelial cells were treated with fetuin-A and/or palmitate for 6-72 h. Proteins were quantified by ELISA and Luminex, mRNA expression by real-time PCR, and cell growth by BrDU-ELISA. Some PVFCs were preincubated with a nuclear factor κB NFκBp65 inhibitor, or the toll-like receptor 4 (TLR4) inhibitor CLI-095, or phosphoinositide 3-kinase (PI3K)/Akt inhibitors and/or stimulated with insulin. Intracellular forkhead box protein O1 (FoxO1), NFκBp65 and inhibitor of κB kinase β (IKKβ) localisation was visualised by immunostaining.


RESULTS
PVFCs expressed and secreted IL-6, IL-8, plasminogen activator inhibitor 1 (PAI-1), basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF)-BB, monocyte chemotactic protein-1 (MCP-1), vascular endothelial growth factor (VEGF), placental growth factor (PLGF) and hepatocyte growth factor (HGF). Fetuin-A upregulated IL-6 and IL-8, and this was potentiated by palmitate and blocked by CLI-095. Immunostaining and electrophoretic mobility shift assay (EMSA) showed partial NFκBp65 activation. MCP-1 was upregulated and blocked by CLI-095, but not by palmitate. However, HGF was downregulated, which was slightly potentiated by palmitate. This effect persisted after TLR4 pathway blockade. Stimulation of insulin-PI3K-Akt signalling by insulin resulted in nuclear FoxO1 extrusion and HGF upregulation. Fetuin-A counteracted these insulin effects.


CONCLUSIONS
Fetuin-A and/or palmitate influence the expression of proinflammatory and angiogenic proteins only partially via TLR4 signalling. HGF downregulation seems to be mediated by interference with the insulin-dependent receptor tyrosine kinase pathway. Fetuin-A may also influence angiogenic and proinflammatory proteins involved in atherosclerosis.
Department of Internal Medicine, Division of Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, University Hospital Tübingen, Otfried-Müller Str. 10, 72076, Tübingen, Germany, dorothea.axel@med.uni-tuebingen.de.
Dorothea I
DI
Siegel-Axel
Susanne
S
Ullrich
Norbert
N
Stefan
Kilian
K
Rittig
Felicia
F
Gerst
Christian
C
Klingler
Ulrike
U
Schmidt
Birgit
B
Schreiner
Elko
E
Randrianarisoa
Hans-Eberhard
HE
Schaller
Ulrich A
UA
Stock
Cora
C
Weigert
Alfred
A
Königsrainer
Hans-Ulrich
HU
Häring
D000273:Adipose Tissue / Q000166:cytology* / Q000378:metabolism; D042501:Angiogenic Proteins / Q000378:metabolism*; D050197:Atherosclerosis / Q000378:metabolism; D001808:Blood Vessels / Q000166:cytology* / Q000378:metabolism; D049109:Cell Proliferation; D018920:Coculture Techniques; D006023:Glycoproteins / Q000378:metabolism; D017228:Hepatocyte Growth Factor / Q000378:metabolism; D006801:Humans; D007249:Inflammation; D008070:Lipopolysaccharides / Q000737:chemistry; D009389:Neovascularization, Pathologic; D010168:Palmitates / Q000737:chemistry; D015398:Signal Transduction; D051197:Toll-Like Receptor 4 / Q000378:metabolism; D060749:alpha-2-HS-Glycoprotein / Q000502:physiology*
C556354:AHSG protein, human; D042501:Angiogenic Proteins; D006023:Glycoproteins; C066855:HGF protein, human; D008070:Lipopolysaccharides; D010168:Palmitates; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D060749:alpha-2-HS-Glycoprotein; D017228:Hepatocyte Growth Factor