Dietary fat modulates serum paraoxonase 1 activity in rats

We examined the effects of dietary fats with specific fatty acid compositio ns, on serum paraoxonase (PON1) activity in rats. Male adult Sprague-Dawley rats were divided randomly into four dietary groups. One group received th e control diet [AlN 93M with soybean oil (5 g/100 g diet)], whereas the rem aining three groups received the modified control diet supplemented with (1 5 g/100 g diet) triolein, tripalmitin or fish oil, respectively. After 20 d , blood was obtained after overnight food deprivation and PON1 activity was determined. Serum lipids and lipid components of lipoproteins were also de termined. Serum PON1 activity [mu mol/(L.min)] was significantly (P < 0.05) higher in triolein (98 +/- 6) and lower in fish oil (41 +/- 4), compared w ith tripalmitin-fed rats (63 +/- 11). Serum PON1 activity in tripalmitin-fe d rats was comparable to that of controls (67 +/- 9). Serum PON1 activity c orrelated significantly with serum lecithin: cholesterol acyltransferase (L CAT) activity (r = 0.77, P < 0.001) and was transported in blood principall y in association with the denser subfraction of HDL, very high density lipo protein (VHDL; d > 1.15 kg/L). Serum PON1 activity correlated strongly with serum lipids as well as lipids of VLDL, HDL and its subfractions. Multiple linear regression analysis, however, showed a significant relationship of serum PON1 activity, principally with the phospholipids of VHDL (r = 0.47, P < 0.002). These data suggest that the modulation of serum PON1 activity b y dietary fat may be mediated vis. the effect of the specific fatty acids o n the synthesis and secretion of VHDL, the subfraction of HDL that transpor ts the majority of PON1 in the blood.