Effects of sodium butyrate on 1,25-dihydroxyvitamin D3 receptor activity in primary chick kidney cells

Polydextrose Enhances Calcium Absorption and Bone Retention in Ovariectomized Rats

Purpose. To evaluate the effect of polydextrose (PDX) on Ca bioavailability and prevention of loss of bone mass. Methods. Twenty-four two-month-old ovariectomized rats were fed three isocaloric diets only varied in fiber source and content up to 60 days (FOS group, a commercial mixture of short- and long-chain fructooligosaccharide, OVX group fed AIN 93 diet, and PDX group). A SHAM group was included as control. Apparent Ca absorption percentage (%ABS), changes in total skeleton bone mineral content (tsBMC) and bone mineral density (BMD) and femur BMD, % Bone Volume, Ca and organic femur content, caecal weight, and pH were evaluated. Results. %ABS and caecum weight of PDX and FOS were higher, and caecum pH was lower compared to OVX and SHAM. PDX reached a higher pH and lower caecum weight than FOS possibly because PDX is not completely fermented in the colon. Changes in tsBMC and femur BMD in FOS and PDX were significant lower than SHAM but significantly higher than OVX. % Bone Volume and femur % of Ca in PDX were significantly higher than OVX and FOS but lower than SHAM. Conclusions. PDX increased Ca absorption and prevented bone loss in OVX rats.

Inulin and oligofructose and mineral metabolism: the evidence from animal trials

Nondigestible oligosaccharides have been shown to increase the absorption of several minerals (calcium, magnesium, in some cases phosphorus) and trace elements (mainly copper, iron, zinc). Inulin-type fructans including oligofructose and fructooligosaccharides derived from sucrose by enzymatic transfructosylation are the best investigated food ingredients in this respect. The stimulation of absorption was more pronounced when the demand for calcium was high, i.e., in animals in the rapid growing stage and in animals with impaired calcium absorption because of either ovariectomy or gastrectomy. Even a small stimulation of calcium absorption increased the mineral accumulation in the skeleton because of its persisting effect over months. Inulin-type fructans stimulated mineral absorption and bone mineral accretion when combined with probiotic lactobacilli and in the presence of antibiotics. Direct comparison of different inulin-type fructans revealed a more pronounced effect by inulin or a mixture of long-chain inulin and oligofructose than by oligofructose alone. Mechanisms on how inulin-type fructans mediate this effect include acidification of the intestinal lumen by short-chain fatty acids increasing solubility of minerals in the gut, enlargement of the absorption surface, increased expression of calcium-binding proteins mainly in the large intestine, modulated expression of bone-relevant cytokines, suppression of bone resorption, increased bioavailability of phytoestrogens, and, via stimulation of beneficial commensal microorganisms, increase of calcium uptake by enterocytes. Under certain conditions, inulin-type fructans may improve mineral absorption by their impact on the amelioration of gut health including stabilization of the intestinal flora and reduction of inflammation. The abundance of reports indicate that inulin-type fructans are promising substances that could help to improve the supply with available calcium in human nutrition and by this contribute to bone health.

Inulin, oligofructose and mineral metabolism — experimental data and mechanism

Numerous investigations performed in animal models in the past 10 years have shown repeatedly that non-digestible oligosaccharides (NDO), such as inulin, oligofructose or transgalacto-oligosaccharides (TOS), stimulate mineral absorption, mainly calcium and magnesium. Long-term beneficial effects on bone health have been indicated by accumulation of bone mineral content in growing rats or prevention of bone loss in ovariectomized rats. However, bone mineral content or density are not necessarily associated with bone quality. In recent studies both oligofructose and calcium prevented loss of trabecular bone area induced by oestrogen deficiency, this, however, occurred at different trabecular shapes. The effects of NDO on mineral metabolism may be based on the enhancement of passive and active mineral transport across the intestinal epithelium, mediated by an increase in certain metabolites of the intestinal flora and a reduction of pH. The possible impact of short-chain fatty acids, butyrate in particular, and of polyamines on the stimulation of mineral absorption capacity, and the interaction of oligofructose and antibiotics is discussed.

Inulin and fructo-oligosaccharides differ in their ability to enhance the density of cancellous and cortical bone in the axial and peripheral skeleton of growing rats

Although dietary fructans improve calcium absorption and bone mineral content (BMC) in rats, their effect on calcium bioavailability and bone density may vary with their degree of polymerization. Therefore, for a 3-month period, growing rats received either a control diet or a diet enriched with either oligofructose (OLF) or inulin. At sacrifice, body weight, lean body mass and appendicular bone length were similar in the 3 groups. Rats fed fructans had a similar increase in cecal wall weight (30%), but the relative increase in cecal levels of calbinding-9 K was 2 in the OLF group and 4 in the inulin group. Further, the significant decrease in serum levels of type I collagen C-telopeptide was greater in the inulin group (30%) than in the OLF group (16%). The increase in whole-body bone mineral content (BMC) as measured by DXA was greater in the inulin group than in the OLF group but DXA detected an increase in the BMC of excised femurs only in the inulin group. In contrast, pQCT conducted ex vivo detected a significant increase in the area and mineral density (BMD) of the cancellous bone of both the proximal tibia and vertebra in rats fed fructans and the effect of inulin was greater (P < 0.01) than that of OLF (P < 0.05). Further, inulin but not OLF significantly enhanced the BMD of the cortical bone in both appendicular and peripheral sites (P < 0.01) as well as the polar stress/strain index of femurs (P < 0.01). These observations suggest that, although both inulin and OLF both have a positive effect on BMD, the greatest effect of inulin is related to the higher capacity of this fructan to reduce bone resorption. The different anti-resorptive capacity of the 2 fructans might be related to their different impact on calcium absorption and bioavailability since the increase in cecal amounts of calbindin-9 K, a protein known to play an important role in calcium absorption, was greater in rat fed inulin than in rats fed OLF. Although cecal wall hyperplasia may be of concern, it remains to establish whether the positive effect of fructans observed on calcium absorption in humans is also associated with a positive effect on bone mass and/or mineral density.

Synergistic growth inhibition of prostate cancer cells by 1 alpha,25 Dihydroxyvitamin D(3) and its 19-nor-hexafluoride analogs in combination with either sodium butyrate or trichostatin A

Prostate cancer is a major cause of male cancer death. In vitro and in vivo data support a role for 1 alpha,25 Dihydroxyvitamin D(3) (1 alpha,25(OH)(2)D(3)) in regulating the growth and differentiation of the normal prostate gland yet prostate cancer cells appear significantly less sensitive to this action. Vitamin D(3) receptor (VDR) content or mutational status do not correlate clearly with the antiproliferative effects of 1 alpha,25(OH)(2)D(3) and therefore it is unclear why prostate cancer cell lines are significantly less sensitive to this action. We hypothesized that the antiproliferative responses of prostate cancer cells to 1 alpha,25(OH)(2)D(3) are suppressed by a process involving histone deacetylation. Sodium butyrate (NaB) and trichostatin A (TSA) are inhibitors of histone deacetylase (HDAC) activity. Low doses of NaB or TSA (300 microM and 15 nM respectively), which alone were relatively inactive, synergized with 1 alpha,25(OH)(2)D(3) in liquid and semi-solid agar to inhibit the growth of LNCaP, PC-3 and DU-145 prostate cancer cells. Still greater synergy was observed between vitamin D(3) hexafluoride analogs and either NaB or TSA. The mechanism appeared to involve neither the cyclin-dependent kinase inhibitor, p21((waf1/cip1)) nor cell cycle arrest, but rather induction of apoptosis. These data suggest that cells dysregulate the normal pro-apoptotic signals of 1 alpha,25(OH)(2)D(3) during prostate cancer development by a mechanism involving histone deacetylation. Combination therapy with potent vitamin D(3) analogs and clinically approved HDAC inhibitors may overcome this lesion and improve the treatment of both androgen-dependent and independent prostate cancer.

Dietary fructooligosaccharides change the concentration of calbindin-D9k differently in the mucosa of the small and large intestine of rats

Previously, we confirmed that dietary fructooligosaccharides (FOS) increase calcium absorption in rats. In this study, we examined the influence of FOS feeding on the concentration of calbindin-D9k of several intestinal segments in rats. Rats in the control group were fed a diet without FOS. Rats in the other two groups were fed the diet containing FOS at either 50 or 100 g/kg for 10 d and subjected to a calcium absorption study. On the final day of feeding, the rats were killed and the entire intestine was removed. The intestinal mucosa was collected from four segments, i.e., the proximal and distal segments of the small intestine, the cecum and the colorectum, respectively. The apparent absorption of calcium increased dose dependently (r = 0.9256, P < 0.0001). Significant positive correlations between apparent calcium absorption and the relative amounts of calbindin in both large intestinal segments were observed (cecum, r = 0.8956, P = 0.0011; colorectum, r = 0.8828, P = 0.0016). Also, significant negative correlations between apparent calcium absorption and the relative amounts of calbindin-D9k in both small intestinal segments were observed (proximal, r = -0.7149, P = 0. 0304; distal, r = -0.8740, P = 0.0021). In conclusion, FOS feeding increases levels of calbindin-D9k in the large intestine, but decreases those in the small intestine. Moreover, these results suggest that part of the stimulatory effect of fructooligosaccharides relates to the transcellular route of calcium absorption in the large intestine of rats.

Ontogeny of calbindin-D28K and calretinin in developing chick kidney

The ontogeny of two calcium-binding proteins (calbindin-D28k and calretinin) was studied by immunohistochemical techniques in developing chick kidney. This study showed the presence of calbindin on the 5th incubation day and calretinin on the 7th incubation day in mesonephric distal and connecting tubules, and in the medial wall of the Wolffian duct. At later stages, immunostaining for these two proteins, in particular for calretinin, was also demonstrated in some metanephric proximal tubules. Glomeruli and Bowman's capsules were negative both in the mesonephros and metanephros. The presence of calretinin in the developing kidney has thus been demonstrated for the first time. The early expression of calbindin and calretinin in mesonephric distal tubules suggests their role in regulating the final excretion of calcium. The different patterns of immunoreactivity of the walls of the Wolffian duct can be correlated with their different histogenetic and histological features.

The human and dog 5-HT1D receptors can both activate and inhibit adenylate cyclase in transfected cells

The cloned human serotonin 1D (5-HT1D) receptor has been shown to inhibit adenylate cyclase while the corresponding cloned dog receptor has been characterized by its enhancement of cAMP accumulation. To resolve this apparent discrepancy, the human 5-HT1D receptor has been cloned and expressed in Chinese hamster ovary (CHO) cells and the corresponding dog receptor expressed in mutant Y1 adrenal (Y1 Kin-8) cells. It is shown that both receptors when activated by sumatriptan depress forskolin induced adenosine 3'5'-cyclic monophosphate (cAMP) accumulation by a pertussis toxin sensitive mechanism, presumably involving Gi (the adenylate cyclase inhibitory GTP transducing protein). In the absence of forskolin, the dog receptor enhances cAMP accumulation, thus activating Gs (the adenylate cyclase stimulatory GTP transducing protein). When its overriding action on Gi is blocked by pertussis toxin pretreatment, the human receptor also enhances cAMP accumulation. Thus both 5-HT1D receptors activate markedly Gi and to a lesser extent Gs and can exert opposite effects on the same effector system, adenylate cyclase.