Effects of soy isoflavone consumption on bone structure and milk mineral concentration in a rat model of lactation-associated bone loss

Low protein intake during reproduction compromises the recovery of lactation-induced bone loss in female mouse dams without affecting skeletal muscles

Lactation-induced bone loss occurs due to high calcium requirements for fetal growth but skeletal recovery is normally achieved promptly postweaning. Dietary protein is vital for fetus and mother but the effects of protein undernutrition on the maternal skeleton and skeletal muscles are largely unknown. We used mouse dams fed with normal (N, 20%) or low (L, 8%) protein diet during gestation and lactation and maintained on the same diets (NN, LL) or switched from low to normal (LN) during a 28 d skeletal restoration period post lactation. Skeletal muscle morphology and neuromuscular junction integrity was not different between any of the groups. However, dams fed the low protein diet showed extensive bone loss by the end of lactation, followed by full skeletal recovery in NN dams, partial recovery in LN and poor bone recovery in LL dams. Primary osteoblasts from low protein diet fed mice showed decreased in vitro bone formation and decreased osteogenic marker gene expression; promoter methylation analysis by pyrosequencing showed no differences in Bmpr1a, Ptch1, Sirt1, Osx, and Igf1r osteoregulators, while miR-26a, -34a, and -125b expression was found altered in low protein fed mice. Therefore, normal protein diet is indispensable for maternal musculoskeletal health during the reproductive period.

Prevention of retinoic acid-induced osteoporosis in mice by isoflavone-enriched soy protein

BACKGROUND

A novel soy protein aggregate enriched with isoflavones (SPA-IS), a mixture of soy protein and isoflavones (Mix), isoflavones (IS), and the soy protein were obtained to investigate the preventive effects on osteoporosis induced by retinoic acid in Kunming mice.

RESULTS

The serum osteocalcin levels in the Mix and SPA-IS groups decreased compared with the model group (mice showing retinoic acid-induced osteoporosis) (P < 0.05). The trabecular analysis results showed an increased preventive effect of the SPA-IS group over the Mix group, the IS group, and the soy protein group. The results of both left tibial maximum load and the 4th lumbar structural strength differ between the IS and the SPA-IS groups.

CONCLUSION

The SPA-IS exhibited obvious oestrogenic activities on retinoic acid-induced osteoporosis in Kunming mice compared to Mix, IS, and soy protein. The results suggest that there is a potential use for SPA-IS in the treatment of osteoporosis induced by intake of retinoic acid. The improvement of bone indicators might be attributed to the formation of aggregate particles and the improvement of IS solubility.