Tilapia Protein Hydrolysate Enhances Transepithelial Calcium Transport in Caco2 cells

Abstract

Background: Potent calcium uptake is essential for calcium balance and normal health. Prolonged low intake of calcium is associated with osteoporosis, dental changes, cataracts, and alterations in the brain. However, calcium is difficult to be directly absorbed from the food due to the insoluble calcium salt precipitation that occurs in the intestinal environment. Methods: Tilapia protein hydrolysate (TPH) was prepared by alcalase digestion. The Calcium-binding activity was measured using calcium colorimetric assay, the absorption at 612 nm. The interaction between TPH and calcium was examined by spectroscopic analysis, ultraviolet absorption and fluorescence measurement. TPH-calcium-binding stability in the human digestion system was evaluated by in vitro pepsin-pancreatin hydrolysis simulating human gastric and intestinal digestion. The effects of food components on TPH-calcium-binding activity was also analyzed. The enhancement of transepithelial calcium transport by TPH was determined by in vitro Caco2 epithelial cell-like monolayer. Results: TPH produced from Nile tilapia (Oreochromis niloticus) exhibited calcium-binding activity. It was the peptides in the hydrolysate that contributed to calcium-binding since the spectroscopic changes induced by calcium were characteristic of peptide bonds and tryptophan residues. The calcium binding of TPH was compatible with food matrices. Most food components including saccharides, amino acids and vitamins showed positive or no effects on calcium-binding. The calcium-binding of TPH was also stable in the simulated gastrointestinal digestion system. Pepsin and pancreatin did not considerably change the calcium-binding activity of TPH. Of note, TPH reduced precipitation of calcium by oxalate and phytate, the two most anti-nutritional factors present in green leafy vegetables. Finally, we showed that TPH significantly promoted transepithelial calcium transport in the Caco-2 cell permeability model. Conclusions: Tilapia protein hydrolysate produced by alcalase digestion possessed calcium-binding activity and prevent precipitation of calcium by a mineral chelating agent as well as enhanced transepithelial calcium transport in Caco2 cell. The result implicated the potential of TPH as a functional food ingredient for promoting calcium absorption. Keywords: Tilapia protein hydrolysate; Calcium binding peptides; Calcium absorption