Plasma distribution of non-cholesterol sterols precursors of cholesterol synthesis and phytosterols depend on HDL concentration

Abstract Background Because several sterols are carried by serum lipoproteins that are pivotal in cholesterol metabolism and atherosclerosis this study aimed at investigating their lipoprotein distribution in individuals differing according to HDL-C plasma levels. Methods Healthy participants were selected with plasma HDL-C concentrations < 40 mg/dL (Low HDL, n = 12), above 40 mg/dL and below 60 mg/dL (Controls, n = 10), or above 60 mg/dL (High HDL, n = 15). Plasma lipoproteins were separated by sequential ultracentrifugation. [27-OHC]), noncholesterol sterols precursors of cholesterol synthesis (NCSPCS: desmosterol and lathosterol) and phytosterols (campesterol and sitosterol) were measured by GC-MS analysis. Diferences between groups were compared by Kruskall-walys and Dunn's post-test with correction by Bonferroni. Results The groups were similar in about BMI, age, gender distribution and blood glucose, total cholesterol and LDL-C. The High HDL group had lower concentrations of triglycerides and VLDL-C compared to others. Percentage distribution of plasma 24-OHC and 27-OHC in lipoproteins did not differ among investigated groups, but plasma concentration of 24-OHC was lower in High HDL than in Low HDL (27- OHC significance difference was borderline). NCSPCS and phytosterols predominate in LDL, which carries approximately 50% of these molecules. Approximately 30% of desmosterol and lathosterol are present in HDL, the High HDL group carrying higher percent of both sterols than the Low HDL and Control groups. Less than 20% of NCSPCS are transported in VLDL. Concentration of plasma campesterol and sitosterol did not differ among groups. However, LDL sitosterol percent distribution is lower in High HDL than in Low HDL and Controls. Campesterol and sitosterol percent distributions are higher in High HDL than in the Low HDL group. Conclusions Elevated NCSPCS in the High HDL group suggests HDL facilitates the export of these sterols from cells but not the export of the cholesterol metabolite 24-OHC which is lower in the High HDL than in the Low HDL group. Percent campesterol and sitosterol elevated in HDL suggests phytosterols absorbed in the enterocytes are incorporated mostly into the nascent HDL.