The effect of the ingestion of beta-carotene with medium-chain triglycerides (MCT) or long-chain triglycerides (LCT) on the bioavailability and the provitamin A activity of beta-carotene was investigated in humans. Sixteen healthy young men ingested, on two different days, a test meal containing 120 mg beta-carotene incorporated into 40 g LCT (LCT meal) or 40 g MCT (MCT meal). This meal was followed 6 h later by a beta-carotene-free meal containing 40 g LCT. Chylomicron beta-carotene, retinyl palmitate and triglycerides were measured every hour for 12.5 h after the first meal. No significant increase in chylomicron triglycerides was detected for the 6 h after the MCT meal intake, whereas a significant increase in chylomicron triglycerides was observed after the LCT meal intake. The chylomicron beta-carotene and retinyl palmitate responses to the MCT meal (0-6 h area under the curves, AUC) were significantly (P< 0.05) lower [AUC = 68.1 +/- 26.8 and 43. 4 +/- 10.4 nmol/(L.h), for beta-carotene and retinyl palmitate, respectively] than those obtained after the LCT meal [301.4 +/- 64.0 and 166.0 +/- 29.0 nmol/(L.h), respectively]. The chylomicron beta-carotene and retinyl palmitate responses obtained after the beta-carotene-free meal (6-12.5 h AUC) were also significantly lower when the first meal provided MCT rather than LCT. The chylomicron (retinyl palmitate/beta-carotene) ratios were constant during the postprandial periods, whatever the meal ingested. We conclude that the chylomicron beta-carotene response is markedly diminished when beta-carotene is absorbed with MCT instead of LCT. This phenomenon is apparently due to the lack of secretion of chylomicrons in response to MCT; however, a lower intestinal absorption of beta-carotene or a higher transport of beta-carotene via the portal way in the presence of MCT cannot be ruled out. Finally, the data obtained show that MCT do not affect the rate of intestinal conversion of beta-carotene into vitamin A.

No abstract

We aimed to provide basic data on the processing of vitamin A and E in the human gastrointestinal tract and to assess whether the size of emulsion fat globules affects the bioavailability of these vitamins. Eight healthy men received intragastrically two lipid formulas differing in their fat-globule median diameter (0.7 vs. 10. 1 microm. Formulas provided 28 mg vitamin A as retinyl palmitate and 440 mg vitamin E as all-rac alpha-tocopherol. Vitamins were measured in gastric and duodenal aspirates, as well as in chylomicrons, during the postprandial period. The gastric emptying rate of lipids and vitamin A and E was similar. The free retinol/total vitamin A ratio was not significantly modified in the stomach, whereas it was dramatically increased in the duodenum. The proportion of ingested lipid and vitamins was very similar in the duodenal content. The chylomicron response of lipids and vitamins was not significantly different between the two emulsions. Our main conclusions are as follows: 1) there is no significant metabolism of vitamin A and E in the human stomach, 2) the enzyme(s) present in the duodenal lumen is significantly involved in the hydrolysis of retinyl esters, and 3) the size of emulsion fat globules has no major effect on the overall absorption of vitamin A and E.

The effect of ageing on vitamin E bioavailability in humans was assessed by comparing chylomicron and plasma alpha-tocopherol postprandial concentrations after a dose of vitamin E (432 or 937 IU as d1-alpha-tocopherol acetate), in eight young (20-30 years old) and eight healthy elderly men (64-72 years old). The fasting plasma alpha-tocopherol concentration was significantly higher in the elderly (33 +/- 2 mumol L-1) than in the young (22 +/- 2 mumol L-1). In both groups, the plasma and chylomicron alpha-tocopherol postprandial concentrations were significantly, approximately twofold, higher after the 937-IU meal than after the 432-IU meal. For both test meals, the chylomicron alpha-tocopherol areas under the curve were significantly lower in the elderly than in the young subjects: 98.9 +/- 16.5 (young group) vs. 55.3 +/- 7.8 (elderly group) mumol L-1 h for the 937-IU test meal and 60.4 +/- 14.1 (young group) vs. 26.0 +/- 7.6 (elderly group) mumol L-1 h for the 432-IU test meal, whereas the plasma alpha-tocopherol area under the curve was significantly higher in elderly than in young subjects: 337.56 +/- 16.11 (937-IU test meal) vs. 159.81 +/- 35.55 (432-IU test meal) mumol L-1 h in the young group and 709.55 +/- 69.33 (937-IU test meal) vs. 436.39 +/- 41.08 (432-IU test meal) mumol L-1 h in the elderly group. We concluded that (a) the amount of vitamin E appearing in plasma is proportional to the dose ingested (up to 937 IU); (b) the intestinal absorption of vitamin E is not increased, even possibly decreased, in the elderly; and (c) the amount of vitamin E transported by non-chylomicron lipoproteins is apparently higher in the elderly. This suggests that vitamin E postprandial transport is affected by ageing, mainly as the consequence of age-related modifications of lipoprotein metabolism.

Human milk is recommended for feeding preterm infants. The current pilot study aims to determine whether breast-milk lipidome had any impact on the early growth-pattern of preterm infants fed their own mother’s milk. A prospective-monocentric-observational birth-cohort was established, enrolling 138 preterm infants, who received their own mother’s breast-milk throughout hospital stay. All infants were ranked according to the change in weight Z-score between birth and hospital discharge. Then, we selected infants who experienced “slower” (n = 15, −1.54 ± 0.42 Z-score) or “faster” (n = 11, −0.48 ± 0.19 Z-score) growth; as expected, although groups did not differ regarding gestational age, birth weight Z-score was lower in the “faster-growth” group (0.56 ± 0.72 vs. −1.59 ± 0.96). Liquid chromatography–mass spectrometry lipidomic signatures combined with multivariate analyses made it possible to identify breast-milk lipid species that allowed clear-cut discrimination between groups. Validation of the selected biomarkers was performed using multidimensional statistical, false-discovery-rate and ROC (Receiver Operating Characteristic) tools. Breast-milk associated with faster growth contained more medium-chain saturated fatty acid and sphingomyelin, dihomo-γ-linolenic acid (DGLA)-containing phosphethanolamine, and less oleic acid-containing triglyceride and DGLA-oxylipin. The ability of such biomarkers to predict early-growth was validated in presence of confounding clinical factors but remains to be ascertained in larger cohort studies.

No abstract

To assess the global effect of preterm birth on fetal metabolism and maternal-fetal nutrient transfer, we used a mass spectrometric-based chemical phenotyping approach on cord blood obtained at the time of birth. We sampled umbilical venous, umbilical arterial, and maternal blood from mothers delivering very-low birth weight (VLBW, with a median gestational age and weight of 29 weeks, and 1210 g, respectively) premature or full-term (FT) neonates. In VLBW group, we observed a significant elevation in the levels and maternal-fetal gradients of butyryl-, isovaleryl-, hexanoyl- and octanoyl-carnitines, suggesting enhanced short- and medium chain fatty acid β-oxidation in human preterm feto-placental unit. The significant decrease in glutamine-glutamate in preterm arterial cord blood beside lower levels of amino acid precursors of Krebs cycle suggest increased glutamine utilization in the fast growing tissues of preterm fetus with a deregulation in placental glutamate-glutamine shuttling. Enhanced glutathione utilization is likely to account for the decrease in precursor amino acids (serine, betaine, glutamate and methionine) in arterial cord blood. An increase in both the circulating levels and maternal-fetal gradients of several polyamines in their acetylated form (diacetylspermine and acetylputrescine) suggests an enhanced polyamine metabolic cycling in extreme prematurity. Our metabolomics study allowed the identification of alterations in fetal energy, antioxidant defense, and polyamines and purines flux as a signature of premature birth.

BackgroundAdequate foetal growth is primarily determined by nutrient availability, which is dependent on placental nutrient transport and foetal metabolism. We have used 1H nuclear magnetic resonance (NMR) spectroscopy to probe the metabolic adaptations associated with premature birth.MethodologyThe metabolic profile in 1H NMR spectra of plasma taken immediately after birth from umbilical vein, umbilical artery and maternal blood were recorded for mothers delivering very-low-birth-weight (VLBW) or normo-ponderal full-term (FT) neonates.Principal FindingsClear distinctions between maternal and cord plasma of all samples were observed by principal component analysis (PCA). Levels of amino acids, glucose, and albumin-lysyl in cord plasma exceeded those in maternal plasma, whereas lipoproteins (notably low-density lipoprotein (LDL) and very low-density lipoprotein (VLDL) and lipid levels were lower in cord plasma from both VLBW and FT neonates. The metabolic signature of mothers delivering VLBW infants included decreased levels of acetate and increased levels of lipids, pyruvate, glutamine, valine and threonine. Decreased levels of lipoproteins glucose, pyruvate and albumin-lysyl and increased levels of glutamine were characteristic of cord blood (both arterial and venous) from VLBW infants, along with a decrease in levels of several amino acids in arterial cord blood.ConclusionThese results show that, because of its characteristics and simple non-invasive mode of collection, cord plasma is particularly suited for metabolomic analysis even in VLBW infants and provides new insights into the materno-foetal nutrient exchange in preterm infants.