Preparation and anti-osteoporotic activities in vivo of phosphorylated peptides from Antarctic krill (Euphausia superba)

Antarctic krill (Euphausia superba) protein serves as a novel sustainable protein source for human. Krill protein isolate was phosphorylated by the dry-heating method with sodium pyrophosphate. Phosphorylated peptides from Antarctic krill (PP-AKP) were obtained from phosphorylated protein through tryptic hydrolysis. Two types of phosphate bonds were introduced by phosphorylation, i.e. PO and PO bonds. The anti-osteoporotic activities of PP-AKP at two doses (400 and 800 mg/kg body weight) were investigated with an osteoporotic rat model, which was established with bilateral ovariectomy surgery. Different doses of PP-AKP were given intraperitoneal injections to rats once a day with alendronate as a positive control. Phosphorylated peptides from Antarctic krill dose-dependently preserved bone mineral density in osteoporotic rats by increasing the degree of bone mineralization. Both trabecular and cortical bone strength in osteoporotic rats was significantly improved with PP-AKP treatment. The mechanism by which PP-AKP augmented bone mineral density and bone strength was relation to the reduction in osteoclast-mediated bone remodeling, as was supported by the decrease in bone resorption markers. Phosphorylated peptides from Antarctic krill could be developed as functional food or nutritional supplements.