Effects of habitual chitosan intake on bone mass, bone-related metabolic markers and duodenum CaBP D9K mRNA in ovariectomized SHRSP rats

• Published in: Journal of Nutritional Science and Vitaminology 2002, Vol.48(5), pp.371-378
• Main Authors: Yang, C.Y. (Waseda Univ., Tokyo (Japan)), Oh, T.W, Nakajima, D, Maeda, A, Naka, T, Kim ,C.S, Igawa, S, Ohta, F
• Format: Article
• Language: English
• Subjects: Analysis of Variance; Animals; Anticholesteremic Agents - administration & dosage; Anticholesteremic Agents - adverse effects; Anticholesteremic Agents - blood; Anticholesteremic Agents - urine; Antioxidants - therapeutic use; Ascorbic Acid - therapeutic use; Biological and medical sciences; Biomarkers - analysis; Bone Density - drug effects; bone loss; BONES; CaBP D9K mRNA; Chitin - administration & dosage; Chitin - adverse effects; Chitin - analogs & derivatives; Chitin - blood; Chitin - urine; CHITOSAN; dietary chitosan; Diseases of the osteoarticular system; Duodenum - drug effects; Female; INTESTINES; Medical sciences; MESSENGER RNA; Osteoporosis - blood; Osteoporosis - chemically induced; Osteoporosis - prevention & control; Osteoporosis - urine; Osteoporosis. Osteomalacia. Paget disease; OVARIECTOMY; OVX rats; PROTEINS; RATS; Rats, Inbred SHR; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - drug effects; S100 Calcium Binding Protein G - drug effects; serum 1,25(OH)2D3; Time Factors
• ISSN: 0301-4800; 1881-7742
• DOI: 10.3177/jnsv.48.371

We have demonstrated that the habitual intake of chitosan can decrease bone mass in ovariectomized (OVX) SHRSP rats fed a low-Ca diet (0.1%). In the present study, we examined both the etiology of bone loss induced by dietary chitosan and the preventive effect of vitamin C supplementation. Rats were OVX and maintained on one of the following diets for 6 wk: 10% cellulose (CE), 10% chitosan (CH) or 10% chitosan with sodium ascorbate (CHVC). CH caused a significant reduction in bone mineral density (BMD) and stiffness in femurs and the fourth lumbar vertebrae (L4). There was no significant difference in intestinal Ca absorption between CH and CE, whereas CH intake significantly reduced intestinal P absorption. The bone loss in CH rats was accompanied with an increase in urinary Ca excretion and a decrease in serum Ca as well as a significant increment in serum PTH and 1, 25(OH)2D3. The vitamin D receptor and calcium binding protein D9K mRNAs were also significantly increased in the duodenum of CH rats. Vitamin C supplementation to CH caused an increase in the Ca and P contents of femurs as well as BMD of the L4, with a decrease in urinary Ca excretion. These results indicate that dietary chitosan with low Ca intake possibly induces the loss of bone mass by enhancing urinary Ca excretion rather than by inhibiting Ca absorption, and that vitamin C supplementation could prevent bone loss caused by chitosan through the increment of retained Ca followed by suppression of urinary Ca excretion.