Increased plasma concentrations of lipoprotein(a) during a low-fat, high-carbohydrate diet are associated with increased plasma concentrations of apolipoprotein C-III bound to apolipoprotein

Background: Low-fat, high-carbohydrate (LFHC) diets have been shown to increase plasma concentrations of lipoprotein(a) [Lp(a)] and of triacylglycerol- rich lipoproteins (TRLs). Objective:WetestedwhetherincreasesinplasmaLp(a)inducedby an LFHC diet are related to changes in TRLs. Design: Healthy men (study 1; n 140) consumed for 4 wk each a high-fat,low-carbohydratediet(HFLC;40%fat,45%carbohydrate) and an LFHC diet (20% fat, 65% carbohydrate). Plasma lipids; lipoproteins; apolipoprotein (apo) B, A-I, and C-III; and Lp(a) were measuredattheendofeachdiet.Inasecondgroupofmenfollowing a similar dietary protocol (study 2; n 33), we isolated apo(a)containing particles by immunoaffinity chromatography and determined the concentrations of apo C-III in ultracentrifugally isolated subfractions of apo B–containing lipoproteins. Results: In study 1, plasma concentrations of Lp(a) (P 0.001), triacylglycerol (P 0.001), apo B (P 0.005), apo C-III (P 0.005), and apo C-III in apo B–containing lipoproteins (non-HDL apoC-III)(P0.001)weresignificantlyhigherwiththeLFHCdiet than with the HFLC diet. Stepwise multiple linear regression analysisshowedthattheassociationofchangesinLp(a)withchangesin non-HDLapoC-IIIwasindependentofchangesinbodymassindex, apo B, LDL cholesterol, and HDL cholesterol. Plasma lipid and lipoprotein changes were similar in study 2, and we found that both total apo C-III and the apo C-III content of apo(a)-containing particles were increased in a TRL fraction consisting predominantly of large VLDL particles [TRL-apo(a)]. Conclusions: The increase in plasma Lp(a) with an LFHC diet is significantly associated with an increase in non-HDL apo C-III. Enrichment of TRL-apo(a) with apo C-III may contribute to this dietaryeffectonLp(a)concentrations. AmJClinNutr2007;85: 1527–32.