Long-term fatty acid stability in human serum cholesteryl ester, triglyceride, and phospholipid fractions

Abstract

Fatty acid profiles of biological specimens from epidemiological/clinical studies can serve as biomarkers to assess potential relationships between diet and chronic disease risk. However, data are limited regarding fatty acid stability in archived specimens following long-term storage, a variable that could affect result validity. Our objective was to determine the effect of prolonged storage at -80 degrees C on the fatty acid profiles of serum cholesteryl ester (CE), triglyceride (TG), and phospholipid (PL) fractions. This was accomplished by determining the fatty acid profile of frozen, archived, previously unthawed serum samples from 22 subjects who participated in a controlled feeding trial. Initial analysis was performed after trial completion and the repeat analysis after 8-10 years of storage using GC. No significant differences were observed among the majority of fatty acids regardless of lipid fraction. Reliability coefficients were high for the fatty acid classes (saturated fatty acid : 0.70, MUFA : 0.90, PUFA : 0.80). When differences were identified, they were limited to low abundance fatty acids (<or=1.5 mol%). These differences were quantitatively small and likely attributable to technical improvements in GC methodology rather than sample degradation. Thus, our data demonstrate that storage at -80 degrees C up to 10 years does not significantly influence serum CE, TG, or PL fatty acid profiles.