Effects of whey-milk proteins on Caco-2 and HT-29 intestinal cell lines

The objective of this study was to determine whether alpha-lactalbumin (alpha-LA) and beta-lactoglobulin (beta-LG) affect proliferation of intestinal cells. As a consequence of intake of milk, epithelial cells of the intestine may be subjected to small concentrations of undergraded milk proteins. The question was whether alpha-LA or beta-LG have growth promoting or inhibiting properties in the intestinal epithelial cell model systems, Caco-2 and HT-29. Cells were grown as recommended by ATCC. Native bovine alpha-LA, or 2 and 4% trypsin hydrolyzed alpha-LA were added to cultures of Caco-2 cells in dosages of 0 to 50 ng/mL. After 24 to 120 h of culture, cell proliferation assays were done. By using the XTT cell proliferation assay, by visually counting cells in selected microscope fields, and by counting trypsinized cell suspensions in a hemocytometer, alpha-LA consistently increased cell replication rate with a peak response at approximately 20 ng/mL. For example, the HTT assay showed 85% increased mitochondrial dehydrogenase activity in the 15 ng/ml treatment relative to control. Higher concentrations were either less effective or ineffective growth stimulators in both cell lines. At 2% alpha-LA hydrolysis, there was a slight stimulation (7%) and no effect at 4% hydrolysis. There was no response using bovine beta-LG as supplement. Variance from plating to plating was high, but percent changes from dose to dose within a plate were consistent over the replicates (C.V. < 5%). These data suggest that concentrations of alpha-LA that might escape digestion could alter the rate of proliferation or maturation of intestinal cells. We have not yet determined the mechanism for the alpha-LA effect. Published by Elsevier Science B.V.