In vivo postprandial bioavailability of interesterified-lipids in sodium-caseinate or chitosan based O/W emulsions.

Recent studies have shown that it should be possible to control lipid bioavailability through food structural approaches. Nevertheless, the gastrointestinal-tract physiological conditions must also be considered. To get a better understanding of this phenomenon, we evaluated the effect of emulsification, as well as the use of sodium caseinate or chitosan, on the postprandial bioavailability of interesterified-lipids in O/W emulsions after oral gastric feeding Sprague-Dawley rats. We verified that emulsification may increase lipid absorption, as determined after feeding sodium-caseinate emulsions. However, this result could not be generalised. Interesterified-lipids that were emulsified with chitosan were equally absorbed as those contained in non-emulsified interesterified-lipids/distilled-water blends.

The effect of interesterification on the bioavailability of fatty acids in structured lipids.

Fatty acid (FA) profile is a critical factor in the nutritional properties of fats, but, stereochemistry may also play a fundamental role in the rate and extent to which FAs are absorbed and become available. To better understand this phenomenon, we evaluated the bioavailability of FAs in linseed-oil and palm-stearin blends compared to their interesterified mix, using a sn-1,3 stereospecific lipase, to determine if there was any difference in terms of FA availability when using this technology. Test meals were fed through an intragastric feeding tube on Sprague-Dawley male rats after 18 h fasting. Postprandial blood samples were collected after meal or physiological serum (control) administration and the FA profile of plasma lipids was determined. Results showed that modification of the melting profile through interesterification, without altering the bioavailability determined by sn-2 stereochemistry, could delay lipid absorption at the beginning, but had no effect on total lipid absorption.

Molecular mechanism of product storage and release in mucin secretion. II. The role of extracellular Ca++.

Mucin-containing granules, produced by mammalian goblet cells in vitro, undergo massive post-exocytotic swelling (23). Their swelling kinetics are similar to the swelling of condensed artificial polymer gels (22). Earlier, we proposed that mucins are condensed in the secretory granule and expand by swelling during or after exocytosis (21). The swelling of mucus is affected by ionic influences, as it is governed by a Donnan equilibrium process (21). However, the effect of cations on the swelling of newly released mucins had not yet been investigated. Calcium has been found in high concentration inside secretory granules of mucin-secreting cells (18, 9, 25), and is also elevated in the mucus of cystic fibrosis patients (17). The present experiments were designed to study the effect of extracellular Ca++ concentration on the swelling kinetics of the newly released secretory product of respiratory goblet cells in vitro. The data show that extracellular Ca++, in concentrations similar to those found in the mucus of cystic fibrosis patients (2 to 4 mM) can produce a four-fold decrease in the diffusivity of the newly released mucin polymer network, resulting in a slow rate of swelling, and a mucus that remains thick for long periods of time. The present findings are in agreement with the Donnan equilibrium hypothesis for the regulation of mucus swelling and rheology (21), and bear important implications for the pathophysiology of cystic fibrosis.