Abstract
Purpose:
Recent studies on VLC-PUFAs (C24-36) have revealed their specific presence and importance in retina. Mouse model and human clinical studies indicate that deficiency of VLC-PUFAs in the retina may be a factor in macular pathology and dysfunction in inherited retinal disease and AMD. Unlike LC-PUFAs such as DHA, AA and EPA, VLC-PUFAs are not present in normal human diet, but must be synthesized in vivo from LC-PUFAs. The n3/n6 LC-PUFA ratios, biomarkers of oxidative stress, could therefore influence these ratios in VLC PUFAs of the human retina. In this study, we examined whether levels and n3/n6 ratios of LC-PUFAs in serum, RBC and orbital fat reflect the levels and n3/n6 ratios of VLC-PUFAs in human retina.
Methods:
Human donor eyes were collected from the Utah Lions Eye Bank, and 4 mm peripheral retinal punches were used for VLC PUFA analysis. Fatty acid methyl esters were extracted using a standardized method and analyzed by GC-MS (electron ionization mode). Two methods (A and B) were adopted, method A was used to analyze the LC-PUFAs while method B was used to analyze C24- C36 VLC-PUFAs.
Results:
The n3/n6 LC-PUFA ratios in serum and RBC positively correlate with the n3/n6 ratios of VLC-PUFAs in human retina. EPA/AA ratios in serum, RBC and orbital fat positively correlate (r=0.92, 0.95 and 0.72) with the VLC-PUFA levels in retina, where as DHA/AA ratios do not correlate. The n3 precursors (18:3, 20:5, 22:5) and n6 precursors (20:4) in RBC are positively associated with retinal n3 and n6 VLC-PUFA levels, respectively.
Conclusions:
EPA and AA, but not DHA act as plausible precursors for synthesis of retinal VLC-PUFAs, and LC-PUFAs in serum and RBC can serve as biomarkers to predict the levels and n3/n6 ratios of VLC-PUFAs in human retina. These findings indicate that diet plays an important role in determining levels and composition of VLC-PUFAs in the human retina.
Keywords: 583 lipids •
592 metabolism •
618 nutritional factors