β-Lactoglobulin as a Molecular Carrier of Linoleate: Characterization and Effects on Intestinal Epithelial Cells in Vitro

Abstract

The dairy protein β-lactoglobulin (βlg) is known to bind hydrophobic ligands such as fatty acids. In the present work, we investigated the biological activity in vitro of linoleate once complexed to bovine βlg. Binding of linoleate (C18:2) to bovine βlg was achieved by heating at 60 °C for 30 min at pH 7.4, resulting in a linoleate/βlg molar binding stoichiometry of 1.1, 2.1, and 3.4. Two types of binding sites were determined by ITC titrations. Binding of linoleate induced the formation of covalent dimers and trimers of βlg. The LD50 on Caco-2 cells after 24 h was 58 μM linoleate. However, cell viability was unaffected when 200 μM linoleate was presented to the Caco-2 cells as part of the βlg complex. The Caco-2 cells did not increase mRNA transcript levels of long chain fatty acid transport genes, FATP4 and FABPpm, or increase levels of the cAMP signal, in response to the presence of 50 μM linoleate alone or as part of the βlg complex. Therefore, it is proposed that βlg can act as a molecular carrier and alter the bioaccessibility of linoleate/linoleic acid.

β-Lactoglobulin-linoleate complexes: In vitro digestion and the role of protein in fatty acid uptake

“…However, uptake and bioavailability of FA may be altered depending on the food matrix (Kushibiki et al, 2001, Mu, 2008, Singh et al, 2009. We observed that linoleate, the salt form of LA, bound to βlg was less bioaccessible compared to free linoleate (Le Maux et al, 2012). After uptake in enterocyte cells, FA are bound to proteins for their intracellular trafficking and thioesterification (Niot et al, 2009).…”

“…Linoleate/βlg complexes were prepared by mixing a solution of βlg and sodium linoleate adapted from Lišková et al (2011) and described by Le Maux et al (2012). Under these conditions complexes with 1, 2 and 3 linoleate bound to βlg are formed.…”

“…Previously, the salt of the essential long-chain fatty acid (LCFA) linoleic acid (LA,cis,18:2) was shown to bind βlg (Le Maux et al, 2012). LA represents 1-3 % (w/w) of the FA in milk fat (Jensen, 2002).…”

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“…According to the literature, human milk is totally free from β-lactoglobulin and it is reported in whey protein of sheep's, goat's and mare's milk [24]. The percentage of beta lactoglobulin is reported in cow (18.4-20.1%), sheep (59.24 -77.7%) and goat (43.54-63.8%).…”

“…Most of the beneficial effect related to peptides formation through the hydrolysis of whey proteins. These whey peptides is one of the major peptides that are responsible for inhibiting angiotensin converting enzyme, which induces bloodpressure regulating effects [24].…”