Rosiglitazone inhibits the insulin-mediated increase in PAI-1 secretion in human abdominal subcutaneous adipocytes.
OBJECTIVE
The aim of this study was to investigate the effect of insulin and an insulin-sensitizing agent, rosiglitazone (RSG), on the production of plasminogen-activator inhibitor-1 (PAI-1) in isolated subcutaneous abdominal adipocytes. Human tissue-type plasminogen activator (t-PA) was also measured to assess changes in overall thrombotic risk.


METHODS
The mean depot-specific expression of PAI-1 and t-PA mRNA (n = 42) in subcutaneous abdominal (n = 21), omental (n = 10) and thigh (n = 11) adipose tissue depots was examined. Furthermore, subcutaneous adipocytes were treated with insulin, RSG and insulin in combination with RSG (10-8 m) for 48 h. Conditioned media were collected and enzyme-linked immunosorbent assays performed for PAI-1 and t-PA (n = 12) antigen. PAI-1 and t-PA mRNA levels were also assessed.


RESULTS
PAI-1 mRNA levels were significantly higher in subcutaneous and omental abdominal tissue than in thigh fat (p = 0.037 and p = 0.014). No change in t-PA mRNA expression between the adipose tissue depots was observed. Insulin stimulated PAI-1 protein secretion in a concentration-dependent manner in adipocytes (control: 68.3 +/- 1.2 ng/ml (s.e.m.); 10 nm insulin: 73.7 +/- 3.8 ng/ml upward arrow; 100 nm insulin: 86.8 +/- 4.1 ng/ml upward arrow **; 1000 nm insulin: 102.0 +/- 4.8 ng/ml upward arrow ***; **p < 0.01, ***p < 0.001). In contrast, insulin + RSG (10-8 m) reduced PAI-1 production relative to insulin alone (***p < 0.001), whilst RSG alone reduced PAI-1 protein secretion in a concentration-dependent manner (RSG at 10-10 m: 50.4 +/- 2.87 ng/ml downward arrow ***; RSG at 10-5 m: 30.3 +/- 2.0 ng/ml downward arrow ***; p < 0.001). No difference was observed between control and treatments for t-PA secretion (range 7-11 ng/ml).


CONCLUSIONS
Insulin stimulated PAI-1 secretion, whilst RSG reduced both PAI-1 secretion alone and in combination with insulin. These data suggest that adipose tissue may contribute significantly to the elevated circulating PAI-1 in obesity. Therefore, RSG's effects on PAI-1 production in adipose tissue may contribute to the fall in circulating PAI-1 levels observed in patients receiving RSG therapy.
Harte
A L
AL
Division of Medical Sciences, Department of Medicine, University of Birmingham and Heartlands Hospital, Edgbaston, Birmingham, UK.
McTernan
P G
PG
McTernan
C L
CL
Smith
S A
SA
Barnett
A H
AH
Kumar
S
S
D017667:Adipocytes / Q000187:drug effects* / Q000378:metabolism; D000273:Adipose Tissue / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D000328:Adult; D002478:Cells, Cultured; D046508:Culture Techniques; D004305:Dose-Response Relationship, Drug; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D017395:Plasminogen Activator Inhibitor 1 / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000077154:Rosiglitazone; D045162:Thiazolidinediones / Q000494:pharmacology*; D010959:Tissue Plasminogen Activator / Q000096:biosynthesis / Q000235:genetics
D007004:Hypoglycemic Agents; D007328:Insulin; D017395:Plasminogen Activator Inhibitor 1; D012333:RNA, Messenger; D045162:Thiazolidinediones; D000077154:Rosiglitazone; D010959:Tissue Plasminogen Activator