*Article* **Effects of Elaidic Acid on HDL Cholesterol Uptake Capacity**

**Takuya Iino 1,2, Ryuji Toh 3,\*, Manabu Nagao 3, Masakazu Shinohara 4,5, Amane Harada 2, Katsuhiro Murakami 2, Yasuhiro Irino 2, Makoto Nishimori 1, Sachiko Yoshikawa 1, Yutaro Seto 1, Tatsuro Ishida <sup>1</sup> and Ken-ichi Hirata 1,3**


**Abstract:** Recently we established a cell-free assay to evaluate "cholesterol uptake capacity (CUC)" as a novel concept for high-density lipoprotein (HDL) functionality and demonstrated the feasibility of CUC for coronary risk stratification, although its regulatory mechanism remains unclear. HDL fluidity affects cholesterol efflux, and trans fatty acids (TFA) reduce lipid membrane fluidity when incorporated into phospholipids (PL). This study aimed to clarify the effect of TFA in HDL-PL on CUC. Serum was collected from 264 patients after coronary angiography or percutaneous coronary intervention to measure CUC and elaidic acid levels in HDL-PL, and in vitro analysis using reconstituted HDL (rHDL) was used to determine the HDL-PL mechanism affecting CUC. CUC was positively associated with HDL-PL levels but negatively associated with the proportion of elaidic acid in HDL-PL (elaidic acid in HDL-PL/HDL-PL ratio). Increased elaidic acid-phosphatidylcholine (PC) content in rHDL exhibited no change in particle size or CUC compared to rHDL containing oleic acid in PC. Recombinant human lecithin-cholesterol acyltransferase (LCAT) enhanced CUC, and LCAT-dependent enhancement of CUC and LCAT-dependent cholesterol esterification were suppressed in rHDL containing elaidic acid in PC. Therefore, CUC is affected by HDL-PL concentration, HDL-PL acyl group composition, and LCAT-dependent cholesterol esterification. Elaidic acid precipitated an inhibition of cholesterol uptake and maturation of HDL; therefore, modulation of HDL-PL acyl groups could improve CUC.

**Keywords:** high-density lipoprotein (HDL); cholesterol uptake capacity (CUC); phospholipids (PL); trans-fatty acids (TFA); elaidic acid; lecithin-cholesterol acyltransferase (LCAT)
