Changes of plasma lipoprotein(a) during and after normal pregnancy in Caucasians.

OBJECTIVE: Elevated plasma concentrations of lipoprotein(a) are associated with an increased risk for development of atherosclerosis. High lipoprotein(a) concentrations may also be associated with pregnancy-induced hypertension and pre-eclampsia, but reference data on the course of lipoprotein(a) during uneventful pregnancies are limited and questionable. METHODS: We studied plasma lipoprotein(a) concentrations in 19 healthy nulliparous Caucasian women during and after uncomplicated pregnancy. Blood was sampled every 4 weeks during pregnancy from 9 weeks onwards, during labor and at 2-4 weeks and 3-5 months after delivery. An apolipoprotein(a) (apo(a)) isoform-independent enzyme-linked immunosorbent assay (ELISA) was used to measure lipoprotein(a). Multilevel analysis was used to describe the data. RESULTS: Lipoprotein(a) increased until 35 weeks, subsequently decreased slightly until delivery, and fell to values below early pregnancy concentrations thereafter. The curve is defined by the formula lipoprotein(a) (mg/l) = exp [4.789 + (0.05215 x GA) + (-0.0007371 x GA2)] where GA = gestational age in weeks. CONCLUSIONS: We constructed a curve for plasma lipoprotein(a) which may serve as the standard reference for changes in pregnancy. Its formula is helpful in predicting changes of gestational age-dependent changes of lipoprotein(a) in normal pregnancy.

A single food bolus stimulates albumin synthesis in growing piglets.

BACKGROUND: A stable isotope tracer method to quantify the synthesis of proteins of hepatic origin in response to feeding is described. The response of albumin synthesis on one mixed meal in a piglet model was investigated and the intragastric and intravenous administration modes of 13C-valine were compared. METHODS: The fasting and postprandial fractional synthesis rates (FSRs) of albumin in 15 piglets were measured while infusion rates of 13C-valine were changed in anticipation of the increased appearance of the tracee after a single liquid food bolus (30 mL/kg infant formula). 13C-valine enrichments in albumin hydrolysates at regular time intervals were determined with gas chromatography-combustion isotope ratio mass spectrometry. RESULTS: The intravenous mode (n = 8) showed constant plasma alpha-ketoisovalerate tracer-to-tracee ratios (coefficient of variation range: 1-8%), and a 27% increase in albumin FSR after the food bolus (mean FSR +/- standard error [SE]: fasting 14.4% +/- 1.6% vs. postprandial 18.3% +/- 2.2% per day; P < 0.005). In the intragastric mode (n = 7), albumin FSR calculated from the mean precursor values increased 32% after feeding (fasting 14.6% +/- 1.5% vs. postprandial 19.3% +/- 1.6% per day; P = 0.005), despite absence of constant alpha-ketoisovalerate enrichment (coefficient of variation range: 15-31%). The FSRs were not significantly different between both infusion modes. CONCLUSIONS: A mixed food bolus increases albumin FSR in growing piglets by approximately 30%, irrespective of the tracer administration route. The concept of anticipated precursor steady state is applicable to study changes of hepatic protein synthesis after a single meal. The intragastric mode of tracer administration can be applied as a less invasive method to measure tissue specific protein synthesis in children.