¹Faculty of Pharmaceutical Sciences, and Heart Institute of the Medical School Hospital (INCOR-HCFMUSP), University of São Paulo (USP), São Paulo, Brazil

Correspondence: Dr RC Maranhão, Laboratório de Lípides, Instituto do Coração do Hospital das Clínicas da FMUSP, Av. Enéas de Carvalho Aguiar, 44-CEP, 05403-000 São Paulo-SP, Brasil. E-mail: ramarans@usp.br

Received 19 September 2003; Revised 23 June 2004; Accepted 23 June 2004; Published online 31 August 2004.

Abstract

OBJECTIVE: To investigate whether increasing body mass index (BMI) produces increasingly intense disturbances in the metabolism of chylomicrons, the lipoproteins that carry the dietary lipids absorbed by the intestine in the circulation.

SUBJECTS: Four groups of 10 normolipidemic nondiabetic women at the normal (BMI<25 kg/m²), preobese (BMI 25–30), obese (BMI 30–40) and morbid obese (BMI>40).

METHODS: Chylomicron metabolism was studied using the method of triglyceride-rich emulsions that mimic chylomicrons. The chylomicron-like emulsion doubly labeled with ³H-triolein (TO) and ¹⁴C-cholesteryl-oleate (CO) was intravenously injected to calculate the plasma fractional clearance rates (FCR, in min^-1) by a compartmental analysis model. FCR-TO mirrors both the lipolysis from lipoprotein lipase that the emulsion suffers while still in the circulation, and the triglycerides portion that is not broken down and is removed from the plasma together with the remnant particles. Lipolysis index is calculated subtracting CO from TO areas under the curve.

RESULTS: FCR-TO did not differ among the four groups. The lipolysis index was positively correlated with BMI (r=0.310; P=0.05). On the other hand, FCR-CO progressively diminished from the normal to the morbid obese group (0.0690.01; 0.0640.01; 0.0310.003; 0.0290.005 min^-1, respectively, P=0.003) and there was a negative correlation between FCR-CO and BMI (r=-0.388; P=0.01).

CONCLUSION: In obesity, the capacity to break down chylomicron triglycerides by lipoprotein lipase in vivo increases, but the ability of the organism to remove the resulting chylomicron remnants particles progressively diminishes as the BMI rises. Remnant accumulation most likely predisposes to coronary artery disease development.