Metformin decreases angiogenesis via NF-kappaB and Erk1/2/Erk5 pathways by increasing the antiangiogenic thrombospondin-1.
OBJECTIVE
Polycystic ovary syndrome (PCOS) is associated with insulin resistance (IR), obesity, and cardiovascular complications. Thrombospondin-1 (TSP-1) is a novel antiangiogenic adipokine highly expressed in obese insulin-resistant subjects. We sought to assess TSP-1 levels in adipose tissue (AT) from PCOS women and matched controls. The effects of metformin treatment on circulating TSP-1 levels in PCOS subjects, the effects of serum from normal and PCOS women on in vitro migration and angiogenesis before and after metformin treatment, and ex vivo regulation of AT TSP-1 by D-glucose were also studied.


RESULTS
Serum TSP-1 (ELISA), subcutaneous and omental AT TSP-1 mRNA (reverse transcriptase-polymerase chain reaction), and protein (western blotting) were significantly lower in PCOS women (P < 0.05). Corresponding plasminogen activator inhibitor-1 (PAI-1) and PAI-1 activity were significantly higher (P < 0.01). After 6 months of metformin treatment, there was a significant increase in serum TSP-1 (P < 0.05) and a corresponding decrease in PAI-1 and PAI-1 activity (P < 0.01). In vitro migration and angiogenesis were significantly increased in serum from PCOS women (P < 0.01); these effects were significantly attenuated by metformin treatment (P < 0.01) through the regulation of TSP-1 levels via nuclear factor-kappaB (NF-kappaB), extracellular regulated-signal kinase 1/2 (Erk1/2) and Erk5 pathways. Importantly, changes in the intima media thickness were predictive of changes in serum TSP-1 (P = 0.049). In AT explants, glucose significantly decreased TSP-1 protein production and secretion into conditioned media (ELISA) (P < 0.05, P < 0.001).


CONCLUSIONS
TSP-1 levels are lower in PCOS women. Metformin treatment increases serum TSP-1 in these women. Our findings provide novel insights into the relationship between obesity, IR, and angiogenesis.
Endocrinology and Metabolism Group, Clinical Sciences Research Institute, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK.
Bee K
BK
Tan
Raghu
R
Adya
Jing
J
Chen
Syed
S
Farhatullah
Dennis
D
Heutling
Dan
D
Mitchell
Hendrik
H
Lehnert
Harpal S
HS
Randeva
D000328:Adult; D016022:Case-Control Studies; D002465:Cell Movement / Q000187:drug effects; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000378:metabolism; D015536:Down-Regulation; D042783:Endothelial Cells / Q000187:drug effects* / Q000201:enzymology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005260:Female; D005947:Glucose / Q000378:metabolism; D006801:Humans; D007004:Hypoglycemic Agents / Q000627:therapeutic use*; D007333:Insulin Resistance; D008687:Metformin / Q000627:therapeutic use*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D048054:Mitogen-Activated Protein Kinase 7 / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism*; D018919:Neovascularization, Physiologic / Q000187:drug effects*; D009765:Obesity / Q000201:enzymology / Q000503:physiopathology; D017395:Plasminogen Activator Inhibitor 1 / Q000097:blood; D011085:Polycystic Ovary Syndrome / Q000188:drug therapy* / Q000201:enzymology / Q000503:physiopathology; D012333:RNA, Messenger / Q000378:metabolism; D050151:Subcutaneous Fat / Q000187:drug effects* / Q000378:metabolism; D019700:Thrombospondin 1 / Q000097:blood / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D015854:Up-Regulation
D017077:Culture Media, Conditioned; D007004:Hypoglycemic Agents; D016328:NF-kappa B; D017395:Plasminogen Activator Inhibitor 1; D012333:RNA, Messenger; C051321:SERPINE1 protein, human; D019700:Thrombospondin 1; D008687:Metformin; D048049:Extracellular Signal-Regulated MAP Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048054:Mitogen-Activated Protein Kinase 7; D005947:Glucose