Abstract
Bioactive milk peptides are reported to illicit a range of physiological benefits and have been proposed as potential functional food ingredients. The objective of this study was to characterize the anti-inflammatory properties of sodium caseinate (NaCAS), its enzyme hydrolysate (EH) and peptide-enriched fractions (5 kDa retentate [R], 1 kDaR and 1 kDa permeate [P]), both in vitro using a Caco-2 cell line, and also ex vivo using a porcine colonic tissue explant system. Caco-2 cells were stimulated with tumour necrosis factor alpha (TNFα) and co-treated with casein hydrolysates for 24 h. Following this, interleukin (IL)-8 concentrations in the supernatant were measured using enzyme-linked immunosorbent assay. Porcine colonic tissue was stimulated with lipopolysaccharide and co-treated with casein hydrolysates for 3 h. The expression of a panel of inflammatory cytokines was measured using qPCR. While dexamethasone reduced the IL-8 concentration by 41.6%, the 1 kDaR and 1 kDaP fractions reduced IL-8 by 68.7% and 66.1%, respectively, relative to TNFα-stimulated Caco-2 cells (P < 0.05). In the ex vivo system, only the 1 kDaR fraction elicited a decrease inIL1-α,IL1-β,IL-8,TGF-β andIL-10 expression (P < 0.05). This study provides evidence that the bioactive peptides present in the 1 kDaR fraction of the NaCAS hydrolysate possess anti-inflammatory properties in vitro and ex vivo. Further in vivo analysis of the anti-inflammatory properties of the 1 kDaR is proposed.
Highlights
Milk is an emulsion of milk fat globules within a waterbased fluid of dissolved carbohydrates, minerals and suspended protein particles
Milk bioactives generated from either sodium caseinate (NaCAS) or whey protein are of interest because they are low in lactose and have potential as an alternative milk source for lactose intolerant individuals (Sindayikengera 2006)
Hydrolysates to suppress IL-8 in the tumour necrosis factor alpha (TNFa)-stimulated Caco-2 cell system was an initial strong indicator of the anti-inflammatory activity of these hydrolysates, with both the 1 kDa retentate (1 kDaR) and 1 kDa permeate (1 kDaP) suppressing IL-8 secretion relative to NaCAS, NaCAS enzyme hydrolysate (EH), 5 kDa retentate (5 kDaR), and dexamenthasone. This observation was further supported by the fact that the hydrolysate fractions, in particular the 5 kDaR and 1 kDaR maintained their anti-inflammatory properties in the ex vivo colonic system, reducing the expression of a panel of pro-inflammatory cytokines IL1-a, IL1-b, IL-8, IL-10, TNFa and TGF-b in LPS-challenged porcine colonic tissues
Summary
Milk is an emulsion of milk fat globules within a waterbased fluid of dissolved carbohydrates, minerals and suspended protein particles. The digestion/hydrolysis of milk proteins can yield physiologically important bioactive peptides that have a wide range of biological activities which have been researched extensively in an effort to isolate bioactive ingredients suitable for functional foods These bioactive peptides can be released in vivo by digestion in the gastrointestinal tract or in vitro by fermentation or enzymatic hydrolysis from parent milk proteins (Phelan and Kerins 2011). Milk bioactives generated from either sodium caseinate (NaCAS) or whey protein are of interest because they are low in lactose and have potential as an alternative milk source for lactose intolerant individuals (Sindayikengera 2006)
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