Effects of thermized donkey milk with lysozyme activity on altered gut barrier in mice exposed to water-avoidance stress

摘要

Nutrition plays a crucial role in human gut healththrough the improvement of gut barrier functionality.Donkey milk represents an interesting source of naturalantimicrobial factors such as lysozyme. Recently,anti-inflammatory properties of donkey milk lysozymeactivity were described in a mouse model of ileitis. Thecurrent increase of donkey milk consumption highlightsthe necessity to propose a healthy milk compliant withmicrobiological standards. This study aims to define aheat treatment of donkey milk, retaining its high lysozymeactivity, and to evaluate its beneficial effects ona gut barrier impairment model due to chronic stressin mice. To perform this experiment, samples of rawdonkey milk were collected in 15 distinct French farms.Microbiological analysis and lysozyme content and activitywere evaluated for each sample. Then, severalheat treatments were carried out to define a time andtemperature combination that allowed for both a reductionin the number of total micro-organisms, increasingthe shelf-life of the product, and preservation of lysozymeactivity. The beneficial effect of heated donkeymilk on the gut barrier of mice was evaluated and comparedwith raw donkey milk. We found that samples ofraw donkey milk showed low total mesophilic microbialcounts, and no pathogens were detected. Among thedifferent heat-treatment procedures tested, a 2-min,72°C combination was determined to be the most optimaltime and temperature combination to preservelysozyme activity and increase the shelf-life of donkeymilk. Oral administration of this heat-treated donkeymilk in mice counteracted chronic stress-induced intestinaldamage, illustrated by gut hyper-permeability andlow-grade inflammation, similar to raw donkey milk.We have demonstrated for the first time that oral interventionwith donkey milk, optimally heat-treated toretain enzymatic lysozyme activity, improves intestinalbarrier damage linked to psychological stress in mice.