DOCOSAHEXAENOIC ACID IN RED-BLOOD-CELLS OF PATIENTS WITH X-LINKED RETINITIS-PIGMENTOSA

Purpose. Abnormalities in the distribution of long-chain polyunsaturat ed fatty acids (LCPUFA) have been documented in plasma of patients wit h X-linked retinitis pigmentosa (XLRP). In this study, fatty acid prof iles of red blood cells (RBC) were used as an index for LCPUFA metabol ism in patients with XLRP because RBC lipids reflect membrane-associat ed fatty acids. Correlations between LCPUFA content and electroretinog raphic (ERG) function were assessed. Methods. Mean ages for the XLRP g roup (n = 18) and control group (n = 28) were 22 +/- 18 years and 24 /- 16 years, respectively. Electroretinographic assessment included th e International Society for the Clinical Electrophysiology of Vision s tandard protocol, Methyl esters of RBC fatty acids were analyzed by ca pillary column gas chromatography. Results. The content of the omega 3 fatty acid, docosahexaenoic acid (DHA), was 40% lower in the group wi th XLRP (23.1 +/- 5.9 mu g/ml RBC [mean +/- 1 SD]) than in normal subj ects (38.6 +/- 9.4 mu g/ml RBC, t = 6.24, P < 0.0001). Total omega 3 L CPUFA content in patients with XLRP was reduced by 30% from normal lev els compared to a 10% reduction in omega 6 LCPUFA levels. Elongation r eactions for omega 3, omega 6, saturated fatty acids, and monounsatura ted fatty acids were markedly lower for patients with XLRP than for no rmal subjects. Multiple regression analysis revealed that RBC-DHA was a significant determinant for amplitude and implicit time of cone ERG responses. Conclusions. The overwhelming majority of patients with XLR P have lower levels of DHA in RBCs compared to normally sighted contro l subjects, An analysis of fatty acid profiles suggests a metabolic de fect in fatty acid chain elongation mechanisms. The significant associ ation between DHA content and cone ERG response parameters is consiste nt with an effect of lipid abnormalities on membrane environment and p hysiology in retinal photoreceptors.