Background and aim: Concentrations in blood of plasminogen activator inhibitor type 1 (PAI-1) and circulating free (non-esterified) fatty acids (FFA) are increased in diabetes and may accelerate atherosclerosis. We have shown that FFA increase expression of PAI-1 by activation of a transcription factor that binds to the repeated sequence 5'-TG(G/C) 1-2CTG-3'. This study was designed to determine whether FFA chain length, saturation, or both affect agonist properties and whether agonist properties are mediated by activated, thioesterified FFA (fatty acyl-CoA).

Methods and results: Human hepatoma cells were exposed to selected FFA associated with bovine serum albumin (BSA). Triacsin C (5 microM) was used to inhibit production of fatty acyl-CoA. PAI-1 was assayed by enzyme linked immunosorbent assay. Maximal induction of PAI-1 was similar with medium and long chain FFA (fold induction of PAI-1 accumulated in conditioned media compared with control: C10 = 1.8 +/- 0.1, C12 = 2.0 +/- 0.1, C14 = 2.0 +/- 0.2, C16 = 1.4 +/- 0.1, C18 = 1.6 +/- 0.1, C20 = 1.32 +/- 0.1, p < 0.005 for each compared with control). Increased unsaturation did not alter the agonist properties of FFA (fold induction with C16: 0 = 1.4 +/- 0.1, C16: 1 = 1.4 +/- 0.1; C18: 0 = 1.6 +/- 0.1, C18: 1 = 1.5 +/- 0.1, C18: 2 = 1.6 +/- 0.1, C18: 3 = 1.4 +/- 0.1 and C20: 4 = 1.3 +/- 0.1, C20: 5 = 1.4 +/- 0.1, n = 6). However, maximal effects were seen with lower concentrations of longer chain FFA. Triacsin C consistently attenuated effects of FFA.

Conclusions: Longer chain FFA exhibit maximal effects at lower concentrations. Augmented expression of PAI-1 is mediated by the fatty acyl-CoA derivative. These criteria identify targets for therapy designed to normalize expression of PAI-1 and retard progression of atherosclerosis in subjects with elevated concentrations of FFA in blood including those with insulin resistance.