The influence of oral lipid loads on acylation stimulating protein (ASP) in healthy volunteers

Abstract

OBJECTIVES: To examine the hypothesis that a sustained rise in plasma acylation stimulating protein (ASP, C3a desarg) accompanies the elevation in triacylglycerol that follows the ingestion of an oral fat load.

DESIGN: Following an overnight fast, blood samples were obtained from healthy volunteers while fasting and 15 min, 1, 2, 4, 6 and 8 h following ingestion of: (i) a liquid meal, rich in dairy fat (eight subjects) and (ii) a semi-liquid meal, with higher total fat content and rich in polyunsaturated fat (six subjects).

SUBJECTS AND METHODS: Four male and four female volunteers (age range: 22–51 y; body mass index (BMI): 17.9–26.9 kg/m²) received the first meal. Six subjects (age range: 32–60 y; BMI: 18.0–28.4 kg/m²), including three from the first study, received the second meal using the same protocol. ASP and C5a were measured by radioimmunoassay (RIA) and the complement proteins C3, factor B and C5 by radial immunodiffusion or nephelometry. Tumour necrosis factor (TNF)-α was measured by enhanced ELISA, and plasma cholesterol and triacylglycerol by an automated enzymatic method. The presence of chylomicrons was assessed in post-prandial plasma samples taken after the second meal.

RESULTS: There was no significant change in mean ASP concentration in either group at any time point, following ingestion of either meal. However, there was a significant positive linear trend in ASP following the second fat challenge (ANOVA; P<0.05). There was also no change in complement proteins, plasma cholesterol or TNF-α. Plasma triacylglycerol rose significantly after the first and second meals (P<0.05 and P<0.001 at 2 h post-prandially); the mean maximum rise above the fasting level was 58±41% and 89±38% respectively (mean±s.d.). Chylomicrons were detected in samples taken from each subject after the second meal. Analysis of individual ASP data showed a sustained rise in one subject after the first meal and two subjects after the second meal. Substantial variation in ASP concentration was observed in samples taken in the first 2 h post-prandially.

CONCLUSION: There was no significant change in ASP nor other complement proteins for either group of subjects following ingestion of the lipid loads. Individual data showed substantial variation in post-prandial ASP, but multiple plasma sampling did not define the basis for this variation.