First-generation methods used to quantify HDL-cholesterol have been used for decades. Therefore, first-generation precipitatingreagents still in use, the chemical impact on HDL-particles functionality (structure/activity-relationship) is not well-documented. The study aim was to identify the most efficient precipitating-reagent for lipoprotein separation to be used in the HDL functionalevaluation. A cross-sectional design with convenience sampling was conducted. Plasma samples from 40 individuals, both genders, were evaluated. Biochemical analysis was performed after using different chemical precipitants (e.g. polyethylene glycol - PEG (P1), phosphotungstic-acid (P2), and dextran-sulfate/MgCl2 (P3)) to evaluate HDL-particle-size and PON1-activity. Parametric and non-parametric tests were performed using GraphPad-Prism 5.01 (USA). Differences were considered significant when a p-value < 0.05 were obtained. The PON1-activity comparison differed after NaCl stimulation (p < 0.001, paired t-test) and among chemical precipitant treatments. The PON1-activity differed after sample precipitation with P1 when compared to P2, and P3 (p < 0.05; ANOVA), before and after stratification for dyslipidemia group. The HDL particle-size comparison did not differ, but on the other hand, polydispersity differed after sample precipitation with P3 when compared to P1 or P2 (p < 0.05; ANOVA). Dextran- Sulfate/MgCl2 was a better chemical precipitant for PON1-activity, and PEG for HDL-particle-size, respectively. The HDL functional

INTRODUCTION: Obesity increases triglyceride levels and decreases high-density lipoprotein concentrations in plasma. Artificial emulsions resembling lipidic plasma lipoprotein structures have been used to evaluate low-density lipoprotein metabolism. In grade III obesity, low density lipoprotein metabolism is poorly understood. OBJECTIVE: To evaluate the kinetics with which a cholesterol-rich emulsion (called a low-density emulsion) binds to low-density lipoprotein receptors in a group of patients with grade III obesity by the fractional clearance rate. METHODS: A low-density emulsion was labeled with [14C]-cholesterol ester and [³H]-triglycerides and injected intravenously into ten normolipidemic non-diabetic patients with grade III obesity [body mass index higher than 40 kg/m²] and into ten non-obese healthy controls. Blood samples were collected over 24 hours to determine the plasma decay curve and to calculate the fractional clearance rate. RESULTS: There was no difference regarding plasma levels of total cholesterol or low-density lipoprotein cholesterol between the two groups. The fractional clearance rate of triglycerides was 0.086 ± 0.044 in the obese group and 0.122 ± 0.026 in the controls (p = 0.040), and the fractional clearance rate of cholesterol ester (h-1) was 0.052 ± 0.021 in the obese subjects and 0.058 ± 0.015 (p = 0.971) in the controls. CONCLUSION: Grade III obese subjects exhibited normal low-density lipoprotein removal from plasma as tested by the nanoemulsion method, but triglyceride removal was slower.