Polyunsaturated fatty acid levels of serum and red blood cells in apparently healthy Japanese subjects living in an Urban Area

Aim: We assessed levels of polyunsaturated fatty acid (PUFA) in serum and red blood cells (RBCs) among groups stratified by generation and its clinical significance in Japanese subjects living in an urban area. Methods: We enrolled 200 apparently healthy Japanese (126 males, mean age: 50.3±9.2 years) living in an urban area. Levels of PUFA, including eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), arachidonic acid (AA), and dihomo-gamma-linolenic acid (DGLA) in serum and RBCs were measured for each generation (G1 <35y, G2 35y-<45y, G3 45y-<55y, G4 55y-<65y, G5 ≥65y). Results: No significant differences in EPA, DHA, AA, or EPA/AA were observed between males and females. After dividing into generations, stepwise increases in EPA and DHA, but not DGLA or AA, were observed in serum (all p<0.0001). EPA/AA ratios were stepwisely increased in serum (mean: G1:0.26, G2:0.29, G3:0.43, G4:0.58, G5:0.68, p<0.0001) and RBCs (mean: G1:0.10, G2:0.09, G3:0.15, G4:0.20, G5:0.23, p<0.0001). Positive correlations of EPA (r = 0.83), DHA (r = 0.55), DGLA (r = 0.54), AA (r = 0.29), and EPA/AA (r = 0.91) were demonstrated between serum and RBCs. In addition, a significant positive correlation between EPA/AA ratios and insulin sensitivity as well as a negative correlation between those ratios and insulin resistance were observed in subjects with metabolic syndrome. Conclusion: Low levels of EPA/AA, which were associated with insulin resistance, were demonstrated in young Japanese adults living in an urban area.