Transport of phytanic acid on lipoproteins in Refsum disease

Patients with Refsum disease accumulate significant quantities of phytanic acid in adipose and neural tissue. The accumulation can be reversed by foll owing a diet low in phytanic acid, yet the mechanism of transport of this f atty acid is obscure. We investigated the distribution of phytanic acid in different lipoprotein subfractions in II patients with Refsum disease and 9 unaffected siblings. Plasma phytanic acid was distributed on VLDL (16.2% /- 12.2%), IDL (1.77% +/- 1.64%), LDL (34.8% +/- 12.6%) and HDL (14.3% +/- 7.87%). No correlations with any parameter were seen with total phytanic ac id content. Weak nonsignificant correlations were found with the fractional distribution of phytanic acid and VLDL triglyceride (r = 0.35; p = 0.12) a nd plasma HDL-cholesterol (r = 0.32; p = 0.16) and with LDL:HDL cholesterol ratio (r = 0.33; p = 0.14). Significant correlation of the fractional dist ribution of phytanic acid on lipoprotein particles was noted with the ratio of apolipoprotein B:apolipoprotein Al-containing particles (r = 0.46; p = 0.03) and apolipoprotein B:apolipoprotein Al in HDL, (r = 0.53; p = 0.01). This suggests that the import-export balance for phytanic acid in plasma is related to forward and reverse cholesterol transport on lipoprotein partic les, and only weakly to plasma cholesterol and triglycerides. These ratios of apolipoprotein particles may play a significant role in determining the rate of phytanic acid elimination in patients with Refsum disease.