Emulsion and protein degradation in the elderly: Qualitative insights from a study coupling a dynamic in vitro digestion model with proteomic analyses

Abstract

World ageing is a growing world concern to which dietary solutions may offer effective measures to tackle malnutrition and support a high quality of life. This study applied a dynamic in vitro model mimicking adult or elderly gastro-duodenal digestion, coupled with proteomic analyses to interrogate the differences in the breakdown of an enteral nutrition formula as well as purified α-lactalbumin (α-lac), β-lactoglobulin (β-lg) and lactoferrin (LF). First, the importance of gastric lipase and various age-related differences in gastro-intestinal conditions (e.g. gastric pH profiles) is shown. Droplet sizing and fluorescent microscopy substantiate emulsion coalescence is favored under adult conditions while flocculation is dominant under elderly conditions. SDS-PAGE analyses of digesta also substantiate differences between adults and seniors in terms of protein breakdown. LC-MS proteomic analyses reveal that digesta samples differ in the incidence of amino acids therein. Comparing proteomic data to databases of known bioactive peptides reveals that β-lg and α-lac may generate more bioactive peptides under adult conditions contrary to LF, which was found to be a better source for bioactive peptides under elderly gut conditions. In addition, proteomic data was mined using PeptideRanker, a bioinformatic tool, in an attempt to identify novel peptide candidates. These efforts generated lists of potentially novel bioactive peptides with a bioactivity probability exceeding 0.6 and in some cases even having a bioactivity probability exceeding 0.9. This study brings forward new information regarding lipids and proteins digestive fate of enteral formula and whey proteins in the elderly gut that stimulate the need for further investigations.