[No significant influence of serum amyloid A1 genotypes on serum lipids or HDL clearance]

Serum amyloid A1(SAA1), the major acute phase isotype of SAA protein family, consists of three common allelic variants(SAA1.1, SAA1.3 and SAA1.5) in the Japanese population. We have recently reported that subjects with the SAA1.5 allele have higher plasma SAA concentrations than those without it, a phenomenon probably due to the delayed catabolism of the isotype SAA1.5. Since SAA is present in high density lipoprotein(HDL), this study assessed whether SAA genotype influenced the serum lipid study by altering HDL metabolism. In a total of 279 healthy adults, no difference was noted in their total cholesterol, HDL-cholesterol or triglyceride concentrations among six genotype groups. Plasma clearance of human apolipoprotein AI(apoAI) was studied in mice by giving HDL reconstituted with each recombinant human SAA1 isotype. The apoAI clearance did not differ among each of the SAA1 isotype-conjugated HDLs. Moreover, the changes in content of SAA in HDL also did not alter the apoAI clearance. These results suggest that SAA1 may not play an active role in plasma HDL metabolism.