Dairy Milk Components Differentially Affect Gastrointestinal Health Markers in C57Bl/6 Mice
Authors: Price Tara R. , Baskaran Sangeetha A. , Moncada Kristin , Minamoto Yasushi , Klemashevich Cory , Jayaraman Arul , Suchodolski Jan S. , Walzem Rosemary L. 
Published: November 2023

Impaired gastrointestinal health is thought to play a causative role in chronic systemic inflammation leading to disease. The effects of individual protein sources, namely isolated soy protein (ISP), dried whole milk powder (DWMP), milk fat globule membrane (MFGM) or milk protein concentrate (MPC), on intestinal health was studied using 3 cohorts of C57BL/6J mice (n=5/diet group in each cohort) following 13 weeks of test diet feeding. Isocaloric and isonitrogenous diets provided 20% energy as protein, 50% as carbohydrate and 30% energy as fat. MFGM‐fed mice were heaviest (p<0.005); however, growth rates (avg. daily weight gain), feed efficiency and overall gut motility were similar. Global indicators of gut health including FITC‐dextran assessed permeability, plasma endotoxin and plasma cytokines IFN‐γ, IL‐1β, IL‐6, IL‐12p70, MIP‐2 and eotaxin were similar among treatments. Plasma TNF‐α was increased in MPC‐fed mice (p<0.01) over ISP (40‐fold) and DWMP (10‐fold), albeit intestinal gene expression of TNF‐α in MPC‐fed mice (n=5) was 1/3 of that in ISP‐fed mice and reduced compared to all diet groups (p<0.01). IgA concentrations were increased in MFGM‐fed mice (287 μg/mL) over all diet groups (DWMP = 213 μg/mL, MPC = 199 μg/mL, ISP = 162 μg/mL; p<0.0001). Plasma IL‐10 was similar among groups (n=15/diet, p<0.4). Cecal concentrations of acetate, proprionate, isobutyrate, isovalerate, and valerate were similar. Butyrate (μg/g cecal content) was lowest in MPC‐fed mice (p<0.001) but this difference did not persist when expressed as % of total SCFAs; butyrate comprised 16.7% in all diet groups. Acetate:butyrate was lowest in DWMP (5.20), and less (p<0.04) than MPC (9.46), but similar to that of MFGM (6.92) and ISP (5.78). Morphological analysis of intestines, alkaline phosphatase and myeloperoxidase activities and inflammatory gene expressions were measured in a subset of mice (n=5). Villus height in distal small intestine was shortest in ISP‐fed mice (237 μm), greatest in MFGM‐fed mice (305 μm; p<0.000, 28% increase) and 268 μm in DWMP and 280 μm in MPC. Expression of inflammatory marker genes TLR5, NFκB, MyD88, and apoA1 were similar in distal small intestine from all diet groups while TLR4 expression was increased 2‐fold in MFGM compared to ISP (p<0.06, n=5). Myeloperoxidase activity, a marker of neutrophil infiltration, increased >370% in distal colons of ISP‐fed mice (36.3 μU/mL, n=5) compared to dairy‐fed mice (8.76 μU/mL, n = 5; p<0.006). Intestinal alkaline phosphatase did not differ between diet groups (p<0.07). Within the context of a US Dietary Guidelines macronutrient distribution, protein source appears to differentially affect intestinal health markers in C57Bl/6 mice; dairy protein components have distinct nutritional functionalities. Funding provided by National Dairy Council project #1120 administered by Dairy Research Institute.Support or Funding InformationFunding provided by National Dairy Council project #1120 administered by Dairy Research Institute.