Effects of Habitual Chitosan Intake on Bone Mass, Bone-Related Metabolic Markers and Duodenum CaBP D9K mRNA in Ovariectomized SHRSP Rats.

Abstract

SummaryWe 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 ef fect 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 ascor bate (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 intes tinal 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 ex cretion 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 de crease in urinary Ca excretion. These results indicate that dietary chitosan with low Ca in take 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. Key Words dietary chitosan, OVX rats, bone loss, serum 1,25(OH)2D3, CaBP D9K mRNA Chitosan, a polymer of glucosamine and a type of water insoluble dietary fiber, is prepared by the deacety lation of chitin, which constitutes the exoskeletons of arthropods such as crabs, shrimp, lobsters and insects (1). Chitosan has been shown to have a hypocholes terolemic effect in humans and animals (2-5), and also an inhibitory effect on intestinal fat digestion and ab sorption in rats (6). It has also been reported to be of low toxicity (7), and has come to be widely used as a food supplement to lower blood cholesterol and prevent weight gain. However, in spite of a number of nutri tional advantages, chitosan may serve as a chelator of several minerals and hence impair their bioavailabili ties. Deuchi et al. discovered that decreased intestinal absorption of calcium (Ca) and bone mineral contents of femurs were induced in male rats when fed diets con taining 5% chitosan for 2 wk (8). Moreover, Wada et al., in an experiment using 47Ca, observed that there was no discriminatory difference in fecal Ca excretion in rats fed chitosan or cellulose, but a significant increase in urinary Ca excretion with chitosan intake (9). These studies suggested that dietary chitosan might influence calcium and bone metabolism through inhibiting Ca absorption and/or by accelerating its urinary excretion.The decrease in net Ca retention as a consequence of habitual intake of chitosan with a low-Ca diet may en hance the risk of osteopenia or osteoporosi...

NTP Technical Report on the Toxicity Study of Chitosan (CASRN 9012-76-4) Administered in Feed to Sprague Dawley [Crl:CD(SD)] Rats

“…In addition to the increased 1,25 (OH)2 vitamin D levels, significant decreases in serum phosphorus were also seen in male and female rats. Although intestinal absorption of phosphorus was not measured in this study, chitosan has been observed by others to cause a significant reduction in intestinal phosphorus absorption 64 . Low phosphorus concentrations stimulate 1,25 (OH)2 vitamin D production by the kidney, therefore the increased levels of 1,25 (OH)2 vitamin D observed in this study may be the result of the low phosphorus levels.…”

“…Also, standard osteoporosis studies using rat models commonly utilize ovariectomized animals, which mimics the conditions of menopause and generally increases rates of bone remodeling and bone loss. Ovariectomized SHRSP rats fed 10% chitosan alongside a low calcium diet exhibited decreased bone mineral density and increased femur stiffness 64 . Following ovariectomy, bone loss in the femurs, specifically the femoral neck, is still not observed until a minimum of 30 days postprocedure 75 .…”

Chitosan as an Underrated Polymer in Modern Tissue Engineering

“…When tested at chitosan to fat 1:40, the ratio often used as a dietary supplement, higher tap density chitosan showed an improved fat-binding capacity at around a two-fold increase. Interestingly, 2100 kDa high density (HD1P) could maintain the highest oil entrapment, ranging between 0.77 and 27.50 g oil/g chitosan depending on the interaction ratios [100].…”

Dietary Fiber and Availability of Nutrients: A Case Study on Yoghurt as a Food Model

“…On the other hand, dietary fiber may influence the availability of minerals, such as calcium, magnesium [154] and iron [155]. Animal studies have found that dietary chitosan possibly arrests the absorption of calcium [156,157].…”