Introduction

An elevated level of plasminogen activator inhibitor-1 (PAI-1) in plasma is a core feature of the metabolic syndrome. Plasma PAI-1 is elevated in obesity and might be responsible for some of the secondary effects of obesity as diabetes and cardiovascular diseases. PAI-1 has been shown to decrease during weight loss. However, the beneficial effects of healthy diets on PAI-1 levels may not solely depend on weight loss, but other factors may also play a role. For example better glycemic control has been observed in diabetic patients after a low glycemic index (GI) diet compared to a high GI diet. Still, the relevance of GI in preventing the metabolic syndrome is controversial.

Objectives

The main purpose of the present study was to investigate the effect of 10 weeks intake of a low glycemic index vs. a high glycemic index high-carbohydrate, low fat ad libitum diet on plasma PAI-1 activity and antigen levels in overweight women.

Methods

45 healthy overweight women (BMI 27.6 ± 0.2 kg/m2) were randomly assigned to a parallel 10 week intervention with a low GI (n=23) or high GI (n=22) diet. Fasting blood samples were obtained before and after the 10 weeks. To study the postprandial effect of LGI vs. HGI diets a subgroup of 29 subjects (LGI, n=14; HGI n=15) were assigned to participate in an additional 4-hour meal test on the last day of the intervention. A blood sample at the end of the meal test was obtained. PAI-1 antigen and activity were measured in plasma by IMUBIND PAI-1 ELISA and Spectrolyse PAI chromogenic assay, American Diagnostica, CT.

Results

PAI-1 activity in plasma decreased (P = 0.03) after the low GI diet, the decrease was significantly different (P = 0.01) from the change after a high GI diet. Changes in PAI-1 antigen levels were not significantly different between the groups. When the high GI group had a high GI breakfast, plasma PAI-1 activity was lowered (P = 0.01) after 4 hours and this reduction in activity was more pronounced (P = 0.03) than in the low GI group.

Conclusion

The present study demonstrates that a LGI diet decreases activity of fasting plasma PAI-1 and may therefore be useful for diminishing the adverse cardiovascular effects of obesity.