Dietary calcium and vitamin D2 supplementation with enhanced Lentinula edodes improves osteoporosis-like symptoms and induces duodenal and renal active calcium transport gene expression in mice

초록

The two main sources of vitamin D-3 are de novo synthesis induced by exposure to ultraviolet (UV) light from the sun, and diet. Vitamin D-3 deficiency causes rickets or osteoporosis. Oak mushrooms (Lentinula edodes) that are exposed to UV radiation contain enhanced vitamin D-2 and have much higher calcium content than unmodified (non-irradiated) mushrooms. Such modified edible mushrooms have been proposed as a natural alternative source of dietary vitamin D. In the current study, we have examined whether modified oak mushrooms could improve or prevent osteoporosis-like symptoms in mice fed with low calcium and vitamin D-3-deficient diet. Four-week-old male mice were fed low calcium, vitamin D-3-deficient diets supplemented with 5, 10, or 20% unmodified, calcium-enhanced, or calcium plus vitamin D-2-enhanced oak mushrooms for 4 weeks. To assess the effects of the supplemented diets, we evaluated femur density and length, bone histology, the expression of active calcium transport genes, and serum calcium levels. Mice fed with low calcium and vitamin D-3-deficient diet developed osteoporosis-like symptoms within 4 weeks. Femur density and tibia thickness were significantly higher in mice fed calcium plus vitamin D-2-enhanced mushrooms, and the expression of duodenal and renal calcium transport genes was significantly induced. These results indicate that in mice, vitamin D-2 and/or calcium derived from irradiated oak mushrooms may improve bone mineralization through a direct effect on the bone, and by inducing the expression of calcium-absorbing genes in the duodenum and kidney.

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