Calcium ions enclosed in casein phosphopeptide aggregates are directly involved in the mineral uptake by differentiated HT-29 cells

Casein phosphopeptides (CPPs) display the ability to form aggregates with calcium and promote the mineral uptake in models of intestinal cells. The present study aimed to clarify which fraction of calcium, CPPs – bound or free, is directly involved. A commercial preparation of calcium enriched CPPs was employed. The free intracellular calcium was monitored at the single cell level by fura-2 fluorescence. Results showed that calcium enriched CPPs formed aggregates and promoted mineral uptake by the cells at a stable level regardless of the amount of extracellular calcium, indicating that the fraction of calcium bound to CPPs was responsible of the bioactivity. The decalcified CPPs bind free calcium available in solution, form aggregates and promote the mineral uptake by the cells, but are dependent on extracellular calcium.