Use of Intralipid for kinetic analysis of HDL apoC-III: evidence for a homogeneous kinetic pool of apoC-III in plasma

Abstract

Apolipoprotein C-III (apoC-III) is an important regulator of lipoprotein metabolism. Radioisotope and stable isotope kinetic studies show differing results in relation to the kinetics of apoC-III in HDL. Kinetic analysis of HDL apoC-III may be difficult because of its low concentration, as well as the presence of other apoproteins at higher concentration, in the HDL fraction. We used IntralipidT (IL), known to preferentially extract apoC proteins from plasma, as a means of extracting apoC-III from HDL before apoprotein separation by isoelectric focusing gel electrophoresis for the measurement of tracer enrichment. Protein purity was assessed by an isoleucine-to-leucine (Ile/Leu) ratio, as apoC-III contains no isoleucine. We compared apoC-III kinetics in 14 men using a bolus infusion of deuterated leucine. The Ile/ Leu ratio for IL-extracted HDL (IL-HDL) apoC-III (3.0 6 0.7%) was not different from that of VLDL apoC-III (2.6 6 0.6%) but was significantly lower than that of untreated HDL apoC-III (9.0 6 2.9%) (P , 0.001). The isotopic enrichment curves and fractional catabolic rates (FCRs) for IL-HDL apoC-III were not different from those of VLDL apoC-III. In contrast, HDL apoC-III had significantly lower isotopic enrichments and FCRs than IL-HDL apoC-III (P , 0.001).In conclusion, this simple IL method can be used to isolate apoC

Complexities of plasma apolipoprotein C-III metabolism

“…teins ( 24 ). Because VLDL is cleared much more rapidly from plasma than HDL, these results and conclusions suggest that apoC-III transfers or exchanges between apoB-and apoA-I-containing lipoproteins (and perhaps also between different apoB-containing subspecies), but avoids being catabolized when these lipoproteins are cleared from the circulation.…”

The challenges for molecular nutrition research 4: the “nutritional systems biology level”

“…These examples include the kinetic analysis and even multicompartment models of lipoprotein metabolism [7,21], or even computational models to analyse human energy metabolism during semi-starvation and in cancer cachexia [9,10]. Examples to describe mammalian nutrient metabolism in quantitative kinetic models have been put forward for folate and most recently for glutathione [22,23].…”

Dose-Dependent Effect of Rosuvastatin on VLDL–Apolipoprotein C-III Kinetics in the Metabolic Syndrome

“…The isotopic enrichment is determined as the tracer-to-tracee ratio of monitored selected ions at a mass to charge (m/z) ratio of 212/209. The average coefficient of variation of apoC-III tracer measurement, including processes associated with isolation of apoC-III from plasma through to the measurement of isotopic enrichment, is 5.4% (5).…”

“…ApoC-III is highly associated with hypertriglyceridemia and is a powerful independent predictor of cardiovascular disease risk (4). In circulation, apoC-III is associated with TRL and HDL, exchanging rapidly between these particles (5). In normolipidemic subjects, the majority of plasma apoC-III is bound to HDL, while in hypertriglyceridemic subjects, the majority is bound to TRL (4).…”