study population c .553G polymorphisms APOA 5 gene increases atherogenic LDL levels hypertriglyceridemic patients -1131 TT variant SNP apoA 5 concentrations c .553G variants brachial-ankle pulse wave velocity atherogenic LDL levels APOA 5 variants c .553G -1131 CC variant 599 hypertriglyceridemic patients atherogenic LDL cholesterol levels hypertriglyceridemic patients Hypertriglyceridemia LDL particle size APOA 5 HDL cholesterol levels