Dietary stearic acid and palmitic acid do not differently affect ABCA1-mediated cholesterol efflux capacity in healthy men and postmenopausal women: A randomized controlled trial

Abstract

The saturated fatty acid stearic acid (C18:0) lowers HDL cholesterol compared with palmitic acid (C16:0). However, the ability of HDL particles to promote cholesterol efflux from macrophages (cholesterol efflux capacity; CEC) may better predict coronary heart disease (CHD) risk than HDL cholesterol concentrations. We examined effects of exchanging dietary palmitic acid for stearic acid on ATP-binding cassette transporter A1 (ABCA1)-mediated CEC, and other conventional and emerging cardiometabolic risk makers. In a double-blind, randomized, crossover study with two 4-week isocaloric intervention periods, 34 healthy men and postmenopausal women (61.5±5.7 years, BMI: 25.4±2.5kg/m2) followed diets rich in palmitic acids or stearic acids. Difference in intakes was 6% of daily energy. ABCA1-mediated CEC was measured from J774 macrophages to apolipoprotein (apo)B-depleted serum. Compared with the palmitic-acid diet, the stearic-acid diet lowered serum LDL cholesterol (-0.14mmol/L; p=0.010), HDL cholesterol (-0.09mmol/L; p=<0.001), and apoA1 (-0.05g/L; p<0.001). ABCA1-mediated CEC did not differ between diets (p=0.280). Cholesteryl ester transfer protein (CETP) mass was higher on stearic acid (0.11mg/L; p=0.003), but CETP activity was comparable. ApoB100 did not differ, but triacylglycerol concentrations tended to be higher on stearic acid (p=0.100). Glucose concentrations were comparable. Effects on insulin and C-peptide were sex-dependent. In women, the stearic-acid diet increased insulin concentrations (1.57 μU/mL; p=0.002), while in men, C-peptide concentrations were lower (-0.15ng/mL; p=0.037). Interleukin 6 (0.15pg/mL; p=0.039) and tumor necrosis factor alpha (0.18pg/mL; p=0.005), but not high-sensitivity C-reactive protein, were higher on stearic acid. Soluble intracellular adhesion molecule (9ng/mL; p=0.033), but not soluble vascular cell adhesion molecule and endothelial-selectin concentrations decreased after stearic-acid consumption. As expected, stearic-acid intake lowered LDL cholesterol, HDL cholesterol, and apoA1. Insulin sensitivity in women and low-grade inflammation might be unfavorably affected by stearic-acid intake. However, palmitic-acid and stearic-acid intakes did not differently affect ABCA1-mediated CEC. This trial was registered at clinicaltrials.gov as NCT02835651.