Correcting the Effects of −20 °C Storage and Aliquot Size on Erythrocyte Fatty Acid Content in the Women’s Health Initiative

ω-3 fatty acids and domain-specific cognitive aging: secondary analyses of data from WHISCA

OBJECTIVE

To test the hypothesis that higher levels of red blood cell (RBC) docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) have a protective association with domain-specific cognitive function in women aged 65 years and older.

METHODS

A total of 2,157 women with normal cognition enrolled in a clinical trial of postmenopausal hormone therapy were followed with annual cognitive testing for a median of 5.9 years. In this retrospective cohort study, we assessed the relationship between prerandomization RBC DHA + EPA levels and a) cognitive measures at baseline, and b) cognitive change over time. Endpoints were composite cognitive function and performance in 7 cognitive domains: fine motor speed, verbal memory, visual memory, spatial ability, verbal knowledge, verbal fluency, and working memory.

RESULTS

After adjustment for demographic, clinical, and behavioral characteristics, no significant (p < 0.01) cross-sectional cognitive differences were found between women in the high and low DHA + EPA tertiles at the time of the first annual cognitive battery. In addition, no significant (p < 0.01) differences were found between the high and low DHA + EPA tertiles in the rate of cognitive change over time.

CONCLUSIONS

We did not find an association between RBC DHA + EPA levels and age-associated cognitive decline in a cohort of older, dementia-free women.

EPA and DHA levels in whole blood decrease more rapidly when stored at -20 °C as compared with room temperature, 4 and -75 °C

High-throughput n-3 fatty acid profiling is enabled by collection techniques such as venous whole blood and fingertip prick (FTP) sampling, but the resulting increased sample numbers increases storage demand. Highly unsaturated fatty acids (HUFA) in erythrocytes are susceptible to oxidation, but this tendency is poorly characterized in venous and FTP whole blood. Presently, whole blood samples with low and high n-3 content collected with ethylenediaminetetraacetic acid were stored on chromatography paper with and without BHT pre-treatment for up to 180 days at different temperatures (room, 4, -20, -75 °C). Whole blood prepared with heparin and BHT and stored in cryovials was also examined. Eicosapentaenoic acid (EPA, 20:5n-3) + docosahexaenoic acid (DHA, 22:6n-3) is relatively stable when stored at -75 °C under various conditions but rapidly decreases in whole blood when stored at -20 °C. At -20 °C, BHT + heparin prepared whole blood can prevent decreases in cryovials up to 180 days but BHT only slows the decreases on chromatography paper. Surprisingly, whole blood stored at 4 °C and room temperature was less susceptible to decreases in EPA + DHA as compared with -20 °C storage. Assessments of n-3 blood biomarkers indicate the % n-3 HUFA in total HUFA was more stable as compared with the sum of the relative % of EPA + DHA. In conclusion, FTP and venous whole blood for fatty acid analysis should be stored at -75 °C whenever possible. In the absence of -75 °C storage conditions, BHT should be added and 4 °C or room temperature appear to be better alternatives to -20 °C.

The association between n-3 polyunsaturated fatty acid levels in erythrocytes and the risk of rheumatoid arthritis in Korean women

BACKGROUND

Rheumatoid arthritis (RA) is one of the most common autoimmune diseases that result in chronic inflammation of the joints. n-3 polyunsaturated fatty acids (PUFAs) have been suggested to play a role in the pathogenesis and clinical course of RA. The purpose of the present study was to investigate whether erythrocyte levels of n-3 PUFA are associated with an increased risk of RA and whether this could potentially serve as an indicator of RA disease activity in Korean women.

METHODS

A total of 100 female RA patients and 100 healthy women were enrolled into this study. Erythrocyte fatty acid composition and RA disease activity were evaluated in all patients.

RESULTS

Erythrocyte levels of α-linolenic acid (ALA; 18:3n3), eicosapentaenoic acid (EPA; 20:5n3), and the omega-3 index [EPA + docosahexaenoic acid (DHA)] were significantly lower in RA patients than in healthy controls. Multivariable-adjusted regression analysis showed that the levels of ALA, EPA, and the ratio of EPA to arachidonic acid were negatively associated with the risk of RA after adjusting for body weight and smoking status. Additionally, the concentration of prostaglandin E2 was significantly decreased with increased levels of erythrocyte DHA among RA patients.

CONCLUSIONS

Erythrocyte levels of EPA and ALA were negatively associated with the risk of RA in Korean women, which may be related to eicosanoid metabolism.