Fractionated Dairy Cow Milk β‐Casein Modulates Jejunal Alkaline Phosphatase Activity Kinetics in Neonatal Piglets Liquid Formulas

Bioactive peptides originating from β‐casein have been shown to be resistant to enzymatic digestion in the gastrointestinal tract and to induce immunological responses. Intestinal alkaline phosphatase (IAP) is a critical anti‐inflammatory mediator, because it possesses the ability to catalyze the hydrolytic dephosphorylation of endotoxin lipopolysaccharides (LPS), the key ligands to toll‐like receptors (e.g., TLR4), and other emblematic members of pathogen‐associated‐molecular patterns (PAMPs) such as ATP, thus preventing gut dysbiosis and disorders. This study was conducted to test the hypothesis that immunomodulatory activities possessed by β‐casein would be secondary and mediated through β‐casein modulating IAP functionality. Three formulas were formulated with a control formula containing whey protein as the sole source of protein, and two testing formulas containing total casein to whey protein ratio (%) of 40:60, but differing in β‐casein at 3.51 and 4.36% (on air‐dry basis), respectively; and contents of all other dietary nutrients including metabolizable energy, total crude protein, minerals and vitamins were formulated to be equal among the three formulas. A total of 24 colostrum‐suckled 3‐day‐old piglets were randomly assigned to each formula, housed individually in metabolic crates, and fed their assigned formulas for 18 days according to a randomized block design. At the end of the study, piglets were euthanized and the proximal jejunal tissue samples were taken. The IAP kinetic experiments were conducted with the homogenized porcine jejunal samples (about 25 μg protein each incubation) and 16 gradient concentrations of P ‐nitrophenyl phosphate (pNPP), ranging 0 – 6 mM in incubation media at pH 7.4 and 37 °C. The kinetics (parameter estimates ± SE, P < 0.05) of the jejunal IAP activities of hydrolyzing pNPP were obtained, including V max values (umol/mg protein·min, n = 64) of 0.067 ± 0.003, 0.071 ± 0.004, and 0.068 ± 0.004; and K m values (mM, n = 64) of 0.186 ± 0.037, 0.129 ± 0.035, and 0.474 ± 0.087 in the control, the 3.51%‐ β‐casein, and the 4.36% ‐β‐casein formulas, respectively. Pooled t‐test showed that the jejunal V max was higher ( P < 0.05) in the 3.51%‐ beta‐casein group than in the control and the 4.36 %‐beta‐casein groups by about 4–6% while the jejunal V max values were not different ( P > 0.05) between the control and the 4.36%–beta‐casein groups. Whereas the K m value was lower ( P < 0.05) in the 3.51%–β‐casein group than in the control and the 4.36%‐β‐casein groups by 44% and 2.7‐fold, respectively while the K m value was lower ( P < 0.05) in the control than in the 4.36%–beta‐casein group by 1.6‐fold. Our results show that dietary β‐casein affects the jejunal IAP functionality especially the jejunal IAP enzyme affinity in a dose‐dependent manner, thus indirectly inducing secondary gut local and systemic immunological responses in the neonate. Support or Funding Information NSERC Discovery Program of Canada and Metagen Enzyme Corporation