Lysozyme-rich milk mitigates effects of malnutrition in a pig model of malnutrition and infection

Abstract

Malnutrition remains a leading contributor to the morbidity and mortality of children under the age of 5 years and can weaken the immune system and increase the severity of concurrent infections. Livestock milk with the protective properties of human milk is a potential therapeutic to modulate intestinal microbiota and improve outcomes. The aim of this study was to develop an infection model of childhood malnutrition in the pig to investigate the clinical, intestinal and microbiota changes associated with malnutrition and enterotoxigenic Escherichia coli (ETEC) infection and to test the ability of goat milk and milk from genetically engineered goats expressing the antimicrobial human lysozyme (hLZ) milk to mitigate these effects. Pigs were weaned onto a protein-energy-restricted diet and after 3 weeks were supplemented daily with goat, hLZ or no milk for a further 2 weeks and then challenged with ETEC. The restricted diet enriched faecal microbiota in Proteobacteria as seen in stunted children. Before infection, hLZ milk supplementation improved barrier function and villous height to a greater extent than goat milk. Both goat and hLZ milk enriched for taxa (Ruminococcaceae) associated with weight gain. Post-ETEC infection, pigs supplemented with hLZ milk weighed more, had improved Z-scores, longer villi and showed more stable bacterial populations during ETEC challenge than both the goat and no milk groups. This model of childhood disease was developed to test the confounding effects of malnutrition and infection and demonstrated the potential use of hLZ goat milk to mitigate the impacts of malnutrition and infection.Undernutrition is one of the leading causes of morbidity in developing countries, and it is estimated that 45 % of deaths in children under 5 years of age are associated with malnutrition (1) . Since 1990, hunger and childhood mortality have declined by 50 %; however, in 2015, an estimated six million children under the age of 5 years died, and one-third of children in developing countries still show some degree of primary malnutrition, resulting from protein-energy deficiency (2,3) . Children are especially vulnerable to malnutrition owing to their rapid growth rate and high energy demand to permit cognitive development, skeletal growth, muscle development and fat deposition (4) . In addition, undernutrition can lead to a weakened immune system. This can result in persistent or chronic infection, which may lead to additional complications, including wasting from rapid weight loss, secondary infections, changes in intestinal architecture and long-term impacts on productivity (5) . Malnutrition is also associated with distinct changes in intestinal bacterial populations with the microbiota of malnourished children considered 'immature' and difficult to reverse (6) . Disruptions in the development of the intestinal architecture and microbiota often lead to recurring illness, from which the child may never fully recover (7) , with cognitive and motor deficits appearing by 5 years of age (8,9) . Thus, th...

Metabolomic changes in severe acute malnutrition suggest hepatic oxidative stress: a secondary analysis

“…Animals in this model consistently present with severe wasting; significant intestinal changes including decreased crypt depth, decreased thickness of the lamina propria, increased transcellular and paracellular permeability, and decreased weight and length of small intestine [23 , 24] . One notable discrepancy was that the malnourished piglets in this model did not exhibit hypoalbuminemia [23 , 24] , which is typically observed in children with SAM [13] .…”

“…Carbohydrates, amino acids, and lipids are digested and metabolized similarly in pigs and humans and the digestion products have similar effects on gastrointestinal development [21] . Several piglet models of SAM have been developed over the last decade [23] , [24] , [25] , [26] - 27] . Garas et al [23] developed, and subsequently replicated [24] , a model of SAM rooted in protein-energy malnutrition, in which severely malnourished piglets exhibited several clinical signs of SAM observed in humans, including alterations in intestinal morphology and function, hematology, and serum biochemistry.…”

“…Garas et al [23] developed, and subsequently replicated [24] , a model of SAM rooted in protein-energy malnutrition, in which severely malnourished piglets exhibited several clinical signs of SAM observed in humans, including alterations in intestinal morphology and function, hematology, and serum biochemistry. Animals in this model consistently present with severe wasting; significant intestinal changes including decreased crypt depth, decreased thickness of the lamina propria, increased transcellular and paracellular permeability, and decreased weight and length of small intestine [23 , 24] . One notable discrepancy was that the malnourished piglets in this model did not exhibit hypoalbuminemia [23 , 24] , which is typically observed in children with SAM [13] .…”

Impact of viral disease hypophagia on pig jejunal function and integrity

“…This suggests that under a calorie restricted state the passage of small ions is altered, but not the integrity of tight junctions. In contrast, protein-energy malnourishment in pigs (50% caloric restriction and protein deficient diet), did result in greater FD4 permeability [52,53]. These inconsistencies may be due to the specific nature of the malnutrition model.…”

“…These inconsistencies may be due to the specific nature of the malnutrition model. In studies where macromolecule permeability was increased [52,53], pigs were both energy restricted and fed protein deficient diets, whereas in studies where no change in macromolecule permeability was observed [51; the current study], pigs were energy restricted but fed diets that met their specific nutrient requirements and should not have been in a caloric deficit severe enough to become deficient in specific nutrients such as protein, which is used preferentially and disproportionately by the intestine for maintenance [54]. In support of this, we observed no difference in the phosphorylation (activation) of the energy sensing protein AMPK in the jejunum.…”