Magnesium-Chelating peptides from Miichthys miiuy scales enhance osteogenic and osteoprotective potential in vitro and in vivo

Magnesium deficiency is an underrecognized contributor to osteoporosis, yet conventional magnesium supplements often exhibit limited efficacy due to poor stability and bioavailability. Here, we developed magnesium-chelating peptides from Miichthys miiuy scale (MMSP-Mg) hydrolysates and systematically characterized its stability and osteoprotective activity. MMSP-Mg showed excellent physicochemical stability, retaining more than 80% of its magnesium content over a wide pH range (2–10), temperatures (0–60 °C), and after simulated gastrointestinal digestion. In MC3T3-E1 preosteoblasts, MMSP-Mg significantly promoted osteogenic differentiation, increasing alkaline phosphatase (ALP) activity by 2.05-fold, enhancing mineralized nodule formation by 2.14-fold, and upregulating the osteogenic markers COL1A1 (2.04-fold), Runx2 (1.64-fold), Osterix (1.96-fold), and Osteopontin (OPN; 2.12-fold). In osteoporotic mice, oral administration of MMSP-Mg improved bone metabolism, reducing serum tartrate-resistant acid phosphatase (TRAP) from 19.24 ± 8.63 to 13.71 ± 1.34 U/L and increasing serum phosphorus from 1.03 ± 0.43 to 1.42 ± 0.14 mmol/L, accompanied by marked restoration of femoral microarchitecture on micro-computed tomography. Further purification of MMSP identified two key bioactive peptides, QLGPMGPR and MAPGKDGLR, each exhibiting > 70% magnesium-binding capacity and significantly enhancing ALP activity, with these effects further strengthened upon Mg 2+ -chelation. Collectively, these results demonstrate that MMSP-Mg is a highly stable, peptide-based magnesium supplement with robust osteogenic and osteoprotective potential.