Low Ca Diet Research Articles

Claudin-14 regulates renal Ca++transport in response to CaSR signalling via a novel microRNA pathway

The paracellular claudin channel of the thick ascending limb (TAL) of Henle is critical for Ca(++) reabsorption in the kidney. Genome-wide association studies (GWASs) have identified claudin-14 associated with hypercalciuric nephrolithiasis. Here, we show that claudin-14 promoter activity and transcript are exclusively localized in the TAL. Under normal dietary condition, claudin-14 proteins are suppressed by two microRNA molecules (miR-9 and miR-374). Both microRNAs directly target the 3'-UTR of claudin-14 mRNA; induce its mRNA decay and translational repression in a synergistic manner. Through physical interaction, claudin-14 blocks the paracellular cation channel made of claudin-16 and -19, critical for Ca(++) reabsorption in the TAL. The transcript and protein levels of claudin-14 are upregulated by high Ca(++) diet, while downregulated by low Ca(++) diet. Claudin-14 knockout animals develop hypermagnesaemia, hypomagnesiuria, and hypocalciuria under high Ca(++) dietary condition. MiR-9 and miR-374 transcript levels are regulated by extracellular Ca(++) in a reciprocal manner as claudin-14. The Ca(++) sensing receptor (CaSR) acts upstream of the microRNA-claudin-14 axis. Together, these data have established a key regulatory role for claudin-14 in renal Ca(++) homeostasis.

The Influence of Dietary Calcium and Phosphorus Imbalance on Intestinal NaPi-IIb and Calbindin mRNA Expression and Tibia Parameters of Broilers.

A 2×2 factorial experiment was conducted to study the effect of dietary calcium and non-phytate phosphorus (nPP) imbalance on calbindin and NaPi-IIb mRNA levels in the small intestine and tibia parameters of broiler chicks. One hundred and forty four 1-d-old Arbor Acres male broiler chicks were divided into four treatments consisted of six replicates with six chicks each. The two dietary calcium levels were 1.10% and 0.60%, and two dietary nPP levels were 0.50% and 0.27%. Results showed that a high Ca/nPP ratio diet (4.07:1) significantly depressed feed intake and weight gain of broilers (p<0.05), but a lower Ca:nPP ratio (1.2:1) had no influence (p>0.05). Low-Ca with low-P diet resulted in low tibia minerals and tibia breaking strength of broilers, and all the tibia parameters were further decreased when the dietary ratio of Ca to P was relative higher. Low dietary Ca or P up-regulated the calbindin and NaPi-IIb mRNA expression levels. Low Ca with normal P diet up-regulated duodenal calbindin mRNA expression level to the greatest extent. Low P with a normal Ca diet significantly enhanced NaPi-IIb mRNA expression level to the highest extent. These results suggest that the calbindin and NaPi-IIb mRNA expression were enhanced by the imbalance between dietary Ca and nPP, and their expression were not only influenced by Ca or nPP level, but also the ratio of Ca:nPP.

Mineral Utilization in Rams Fed Ration Supplemented with Different Levels of Chromium, Calcium, and Cation-Anion Balances

Chromium (Cr) is an essential mineral for ruminants. Its metabolism and interactions with other minerals has not been widely known. This experiment was designed to evaluate the utilization of minerals and growth of Garut ram fed ration supplemented with Cr and different Dietary Cation Anion Balance (DCAB) and Ca level. Dietary treatments, namely: R0 (Ration with DCAB+14); R1 (Ration with DCAB+14 + Cr 3ppm,); R2 (Ration with DCAB 0 + Ca); R3 (Ration with DCAB 0 + Cr 3 ppm + Ca), were allocated in twenty four of 1.5-2 years old Garut rams in a randomized block design. The results showed that Cr supplementation in rations containing different levels of Ca did not affect feed intake, body weight gain, and dry matter digestibility, but reduced the absorption of Cr and Ca of the low Ca diet. Supplementation of Cr had no effect on Cr, Ca, Zn, and Mg status in blood and semen of the rams. Level of Cr intake had negative correlation with Ca absorption and positive correlation with blood Cr levels. There is a positive relationship between level of Ca intake with Ca and Mg absorption and blood Ca and Zn levels. Intake of Cr and Ca was not related to the semen Cr and Ca levels.

Upregulation of Hepatic 11β-Hydroxysteroid Dehydrogenase-1 Expression in Calcium-Deficient Rats

Background: Many epidemiologic studies have reported a link between calcium (Ca) deficiency and metabolic syndrome. In this study, we examine Ca deficiency in rats and whether changes in glucocorticoid metabolism are induced. Methods: Twelve-week-old female Wistar rats were weaned onto a very-low-Ca diet (low-Ca group) or a control diet (control group) for 2 weeks. Quantitative real-time PCR was used to assess mRNA for 11β-hydroxysteroid dehydrogenase-1 (11β-HSD1), 11β-HSD2, phosphoenolpyruvate carboxykinase, peroxisome proliferator-activated receptor-α, and glucocorticoid receptor in the liver. Concentrations of adiponectin, leptin, corticosterone, intact parathyroid hormone, asymmetrical dimethylarginine and insulin in fasting serum were determined using a rat-specific enzyme-linked immunosorbent assay. Glucose concentrations were measured using a glucose oxidase system. Serum ionized Ca levels were measured with an automatic ion-selective electrode analyzer. Serum nitrite/nitrate levels were measured using a colorimetric assay kit. Results: After 2 weeks, no differences in serum glucose, corticosterone or insulin levels were observed. The low-Ca group rats showed higher homeostasis model assessment insulin resistance, lower adiponectin and higher intact parathyroid hormone levels. Serum nitrite/nitrate and asymmetrical dimethylarginine were significantly higher in the low-Ca group than in the control group. The expression of hepatic 11β-HSD1 mRNA was upregulated, while hepatic phosphoenolpyruvate carboxykinase expression was downregulated in the low-Ca group. Glucocorticoid receptor, peroxisome proliferator-activated receptor-α and 11β-HSD2 expression levels showed a similar tendency. Conclusion: A low-Ca diet alters glucocorticoid metabolism, which leads to hepatic upregulation of 11β-HSD1, and is possibly a key mechanism inducing the metabolic complications of Ca deficiency.

Improvement of calcium balance byFructus Ligustri Lucidiextract in mature female rats was associated with the induction of serum parathyroid hormone levels

Fructus Ligustri Lucidi (FLL) is a commonly prescribed herb in many kidney-tonifying Traditional Chinese Medicinal formulae for the treatment of osteoporosis. The present study aimed to identify the active fractions in FLL and to characterise its effects on Ca balance, calciotropic hormone levels as well as bone properties in mature female rats fed diets containing different levels of Ca. In the present study, 4-month-old Sprague-Dawley female rats were treated with either FLL ethanol extract (EE), ethyl acetate-soluble fraction of EE (EAF), water-soluble fraction of EE (WF) or their vehicle for 12 weeks on a medium-Ca diet (MCD, 0·6 % Ca, 0·65 % P). Then, the Sprague-Dawley female rats treated with WF or its vehicle for 12 weeks were fed diets containing different levels of dietary Ca (low-Ca diet (LCD), 0·1 % Ca, 0·65 % P; MCD; high-Ca diet (HCD), 1·2 % Ca, 0·65 % P). The results demonstrated that WF from EE but not EAF exerted a prominent effect on Ca balance by inhibiting urinary and faecal Ca excretion. WF significantly increased Ca balance in rats fed MCD or HCD with an associated increase in serum parathyroid hormone (PTH) levels. WF did not alter bone mineral density or bone mineral content of the tibia in all the rats fed with different levels of dietary Ca. In conclusion, WF was responsible for the positive actions of FLL on Ca absorption and balance. The regulation of Ca balance by WF might involve its action in stimulating PTH production in the mature female rats.

Luminal calcium concentration controls intestinal calcium absorption by modification of intestinal alkaline phosphatase activity

Intestinal alkaline phosphatase (IAP) is a brush-border phosphomonoesterase. Its location suggests an involvement in the uptake of nutrients, but its role has not yet been defined. IAP expression parallels that of other proteins involved in Ca absorption under vitamin D stimulation. Experiments carried out in vitro with purified IAP have demonstrated an interaction between Ca and IAP. The gut is prepared to face different levels of Ca intake over time, but high Ca intake in a situation of a low-Ca diet over time would cause excessive entry of Ca into the enterocytes. The presence of a mechanism to block Ca entry and to avoid possible adverse effects is thus predictable. Thus, in the present study, Sprague-Dawley rats were fed with different amounts of Ca in the diet (0.2, 1 and 2 g%), and the percentage of Ca absorption (%Ca) in the presence and absence of L-phenylalanine (Phe) was calculated. The presence of Phe caused a significant increase in %Ca (52.3 (SEM 6.5) % in the presence of Phe v. 31.1 (sem 8.9) % in the absence of Phe, regardless of the amount of Ca intake; paired t test, P = 0.02). When data were analysed with respect to Ca intake, a significant difference was found only in the group with low Ca intake (paired t test, P = 0.03). Additionally, IAP activity increased significantly (ANOVA, P < 0.05) as Ca concentrations increased in the duodenal lumen. The present study provides in vivo evidence that luminal Ca concentration increases the activity of IAP and simultaneously decreases %Ca, acting as a minute-to-minute regulatory mechanism of Ca entry.

Effects of phytase B on laying performance, eggshell quality and on phosphorus and calcium balance in laying hens fed phosphorus-deficient maize-soybean meal diets

A study was conducted to evaluate the effects of dietary supplementation of phytase B (product of the Aspergillus niger phyB gene expressed in Trichoderma reesei) on feed intake, laying performance, eggshell quality, and on phosphorus and calcium balance in laying hens. Seventy-two, 40 weeks old Hy Line Brown hens were fed for 14 weeks the following four phosphorus-deficient (0.12% nonphytate phosphorus, NPP), maize-soybean meal-based diets: (1) calcium-deficient (2.8% Ca) control diet; (2) diet 1 + phytase B at the activity of 2.5&amp;nbsp;acid phosphatase units (AcPU/kg); (3) control diet (3.8% Ca); (4) diet 3 + phytase B at the activity of 2.5 AcPU/ kg. Each dietary treatment was fed to 18 cages of hens, 1 hen/cage kept in individual cages. Hens fed the NPP- and Ca-deficient diets consumed more feed (P &amp;lt; 0.01) and excreted less calcium (P &amp;lt; 0.01) than those receiving P-deficient diets with the standard calcium level. There were no effects of calcium level on feed utilization, egg mass, egg weight, and eggshell breaking strength. Egg production, although numerically higher in hens fed low Ca diets with no enzyme added, failed to be significantly different due to the low number of hens investigated and therefore the measurement should be considered as preliminary and supplementary. Phytase B increased mean egg weight by about 7% in layers fed the NPP- and Ca-deficient diet (Ca &amp;times; phytase B interaction, P &amp;lt; 0.05), increased shell breaking strength, particularly at the standard calcium level, significantly enhanced amounts of calcium retained by layers and amounts of&amp;nbsp; phosphorus retained by hens fed the Ca-deficient diets. Additionally, phytase B improved Ca retention at both dietary Ca levels and phosphorus retention in hens fed the Ca-deficient diets. Results of the study indicate that the efficacy of phytase B in NPP-deficient diets is strongly influenced by the dietary calcium level and the enzyme may modulate egg weight, eggshell quality, phosphorus and calcium retention in laying hens fed low-NPP, maize-soybean meal-based diets.

Increased strontium uptake in trabecular bone of ovariectomized calcium-deficient rats treated with strontium ranelate or strontium chloride

Based on clinical trials showing the efficacy to reduce vertebral and non-vertebral fractures, strontium ranelate (SrR) has been approved in several countries for the treatment of postmenopausal osteoporosis. Hence, it is of special clinical interest to elucidate how the Sr uptake is influenced by dietary Ca deficiency as well as by the formula of Sr administration, SrR versus strontium chloride (SrCl(2)). Three-month-old ovariectomized rats were treated for 90 days with doses of 25 mg kg(-1) d(-1) and 150 mg kg(-1) d(-1) of SrR or SrCl(2) at low (0.1% Ca) or normal (1.19% Ca) Ca diet. Vertebral bone tissue was analysed by confocal synchrotron-radiation-induced micro X-ray fluorescence and by backscattered electron imaging. Principal component analysis and k-means clustering of the acquired elemental maps of Ca and Sr revealed that the newly formed bone exhibited the highest Sr fractions and that low Ca diet increased the Sr uptake by a factor of three to four. Furthermore, Sr uptake in bone of the SrCl(2)-treated animals was generally lower compared with SrR. The study clearly shows that inadequate nutritional calcium intake significantly increases uptake of Sr in serum as well as in trabecular bone matrix. This indicates that nutritional calcium intake as well as serum Ca levels are important regulators of any Sr treatment.

The protective effect of supplemental calcium on colonic permeability depends on a calcium phosphate-induced increase in luminal buffering capacity

An increased intestinal permeability is associated with several diseases. Previously, we have shown that dietary Ca decreases colonic permeability in rats. This might be explained by a calcium-phosphate-induced increase in luminal buffering capacity, which protects against an acidic pH due to microbial fermentation. Therefore, we investigated whether dietary phosphate is a co-player in the effect of Ca on permeability. Rats were fed a humanised low-Ca diet, or a similar diet supplemented with Ca and containing either high, medium or low phosphate concentrations. Chromium-EDTA was added as an inert dietary intestinal permeability marker. After dietary adaptation, short-chain fructo-oligosaccharides (scFOS) were added to all diets to stimulate fermentation, acidify the colonic contents and induce an increase in permeability. Dietary Ca prevented the scFOS-induced increase in intestinal permeability in rats fed medium- and high-phosphate diets but not in those fed the low-phosphate diet. This was associated with higher faecal water cytotoxicity and higher caecal lactate levels in the latter group. Moreover, food intake and body weight during scFOS supplementation were adversely affected by the low-phosphate diet. Importantly, luminal buffering capacity was higher in rats fed the medium- and high-phosphate diets compared with those fed the low-phosphate diet. The protective effect of dietary Ca on intestinal permeability is impaired if dietary phosphate is low. This is associated with a calcium phosphate-induced increase in luminal buffering capacity. Dragging phosphate into the colon and thereby increasing the colonic phosphate concentration is at least part of the mechanism behind the protective effect of Ca on intestinal permeability.

Association of renal failure with poor response to PTH treatment in osteoporosis

Association of renal failure with poor response to PTH treatment in osteoporosis

Dietary Ca concentration to minimize the risk of hypocalcaemia in dairy cows is affected by the dietary cation–anion difference

The objective of this study was to determine whether dietary Ca concentration affects the ability to maintain Ca homeostasis in non-lactating non-pregnant dairy cows fed diets differing in dietary cation–anion difference (DCAD). Eight non-lactating non-pregnant multiparous Holstein cows (594 ± 80.3 kg body weight; 34.5 ± 11.4 month old) were fed diets Low or High in DCAD (−64 vs. 82 mequiv./kg dry matter, respectively) in combinations with Low or High dietary Ca concentration (3.0 vs. 9.1 g/kg of dry matter, respectively) in a duplicated 4 × 4 Latin square design with 14-d periods. On d 14 of each period, cows were subjected to an EDTA challenge that consists of an intra-jugular infusion of EDTA solution to decrease blood Ca concentration. In this protocol, the time required to recover to 90% of the pre-challenge blood Ca concentration was determined as recovery time. During the EDTA challenge, mean blood bicarbonate concentration was lower for cows fed Low-DCAD diets although mean blood pH was not affected by treatment, indicating that cows fed Low-DCAD diets had mild compensated metabolic acidosis. Feeding High-Ca diet shortened the recovery time (106 vs. 134 min; P=0.04) when DCAD was low, while Low-Ca diet shortened the recovery time (125 vs. 159 min; P=0.02) when DCAD was high. These results suggest that the optimum dietary Ca concentration to minimize the risk of hypocalcaemia in dairy cows is likely different depending on the DCAD value.

Animal models for bone and joint disease. Low calcium diet-induced rat model of osteoporosis

Amount of daily calcium (Ca) intake have direct impact on bone metabolism, because of an important mineral component of bone. Two months rearing with less than 0.3% Ca diet clarified effectiveness for a rat model of osteoporosis, resulted in a significant decrease in BMD and bone strength. Besides low Ca diet associated with ovariectomy also induced significant decrease in BMC and BMD in such a short-term. Otherwise precaution for assessment as to an experimental objective ought to be deliberated depend on which part of bone should be evaluated and how long rats should be reared.

Effects of a Low Calcium Diet and Oxalate Intake on Calcium Deposits in Soft Tissues and Bone Metabolism in Ovariectomized Rats

It is controversial whether low calcium intake, commonly associated with osteoporosis, results in calcium accumulation in soft tissues. This study was conducted to investigate the effects of low calcium (Ca) and oxalate (ox) intake on soft-tissue Ca deposits and bone metabolism in ovariectomized (ovx) rats. Eight week old female Sprague-Dawley rats were ovariectomized and divided into four groups. The rats were fed experimental diets containing low (0.1%, w/w) or normal (0.5%, w/w) Ca with or without sodium oxalate (1%, w/w); Sham/NCa, Ovx/NCa, Ovx/LCa, Ovx/NCa-ox, Ovx/LCa-ox for 6 weeks. All ovx rats showed a remarkable increase in body and tissue weight, glutamic oxaloacetic transaminase, glutamic pyruvic transaminase, blood urea nitrogen, alkaline phosphatase, and decreases in weight, ash, and Ca contents, as well as bone breaking force compared to those in sham rats. Serum Ca concentration was not significantly affected by dietary Ca levels or ox intake. Kidney Ca, ox acid content, and microscopic Ca deposition increased remarkably in the Ovx/LCa-ox group compared to those in the other groups. Ca content in the spleen and aorta also increased significantly, but the weight contents, Ca, bone breaking force, and Ca and oxalic acid in feces decreased significantly in the Ovx/LCa-ox group. Serum parathyroid hormone levels were not significantly different among the groups. These results indicate that low Ca intake decreased bone mineral content and increased Ca deposits in soft tissues, which was aggravated by ox intake in ovx rats. Thus, high ox intake may result in a kidney disorder in patients with osteoporosis who eat a low Ca diet.

Eats roots and leaves. Can edible horticultural crops address dietary calcium, magnesium and potassium deficiencies?

Human individuals require at least 20 inorganic elements ('minerals') for normal functioning. However, much of the world's population is probably deficient in one or more essential minerals and at increased risk of physiological disorders. Addressing these 'hidden hungers' is a challenge for the nutrition and agriculture sectors. Mineral deficiencies among populations are typically identified from dietary surveys because (1) minerals are acquired primarily from dietary sources and (2) (bio)assays of mineral status can be unreliable. While dietary surveys are likely to under-report energy intakes, surveys show that 9% of all UK and US adults consume Ca and Mg, and 14% of adults consume K, at quantities below the UK lower reference nutrient intake, and are therefore at risk of deficiency. Low dietary Ca, Mg and K intakes can be caused by energy-malnourishment and by cultural and economic factors driving dietary conservatism. For example, cereal grains routinely displace vegetables and fruits in the diet. Cereal grains have low concentrations of several minerals, notably Ca, as a consequence of their physiology. Low grain mineral concentrations are compounded when cereal crops are grown in soils of low mineral phytoavailability and when grain is processed. In this paper, the impact of increased vegetable consumption and horticultural biofortification, i.e. enhancing crop mineral content through breeding and agronomy, on intakes of the major minerals Ca, Mg and K is assessed. Despite low energy intake from horticultural crops generally, increased vegetable consumption and biofortification would significantly improve dietary intakes of Ca, Mg and K.

Manganese Supplementation Reduces the Blood Cholesterol Levels in Ca-Deficient Ovariectomized Rats

Manganese (Mn) is an essential element for normal development and bodily functions in humans. In the present study, we examined whether Mn supplementation can alter the serum lipid parameters and liver function in Ca-deficient ovariectomized (OVX) rats. Sixty female Sprague-Dawley rats (6weeks) were divided into five groups and bred for 12weeks: sham-operated control group (Sham), OVX Ca deficiency group (OLCa) with Ca-deficient diet (0.1% Ca modified AIN-93N diet), OVX Ca deficiency and Mn supplementation group (OLCaMn), OVX with adequate Ca group (OACa; 0.5% Ca AIN-93N diet), and OVX with adequate Ca and Mn supplementation group (OACaMn). A low Ca diet increased the liver weight and serum levels of GOT, GPT, total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol in OVX rats. Mn supplementation decreased these parameters in Ca-deficient OVX rat. The results of our study suggest Mn supplementation results in reductions of the blood cholesterol levels, which show an increase due to Ca deficiency in OVX rats.

The effects of a 30-month dietary intervention on bone mineral density: The Postmenopausal Health Study

Low dietary Ca intake and vitamin D insufficiency have been implicated as part of the aetiology leading to osteoporosis. The aim of the present study was to examine the effects of a 30-month dietary intervention that combined supplementation of dairy products fortified with Ca and vitamin D3 and lifestyle and nutrition counselling sessions on bone mineral density (BMD) of postmenopausal women. Sixty-six postmenopausal women (aged 55-65 years) were randomised into a dietary group (DG; n 35), receiving daily and for the first 12 months 1200 mg Ca and 7.5 microg vitamin D3, while for the next 18 months of intervention 1200 mg Ca and 22.5 microg vitamin D3 through fortified dairy products, and a control group (CG; n 31) receiving neither counselling nor dairy products. The DG was found to have more favourable changes in arms (P < 0.001), total spine (P = 0.001) and total body BMD (P < 0.001) compared with the CG. Furthermore, a significant increase was observed for the DG in lumbar spine BMD (0.056; 95 % CI 0.009, 0.103), which was not found to differentiate significantly compared with the change observed in the CG (P = 0.075). In conclusion, the present study showed that intakes of vitamin D of about 22.5 microg/d and of Ca close to the recommended level of 1200 mg from fortified dairy foods for 30 months, with compliance ensured by lifestyle and nutrition counselling sessions, can induce favourable changes in arms, total spine and total body BMD of postmenopausal women.

Effect of the supplementation of dietary rich phytoestrogens in altering the vitamin D levels in diet induced osteoporotic rat model

Plant-derived estrogen-like compounds such as isoflavones (IF) especially daidzein and genistein are said to be preserving the bone in the osteoporotic conditions. However, it is not known whether a combination of IF and calcium (Ca) supplementation attenuates losses in bone mass and prevents the loss of vitamin D (VD). The present study addresses the role of phytoestrogens (PE) and Ca supplementation in low Ca and low VD diet induced osteoporosis (OSP). Cowpea (CP) which has high amount of the IF was selected to study its effect on diet induced osteoporotic conditions. Female weanling WNIN rats (total of 68) were divided into five groups and fed for five weeks on semisynthetic diet with low Ca (0.15%) and low VD (0.1 IU/day/rat) in combination with low (10 mg/kg) or high (25 mg/kg) concentrations of PEs derived from CPIF. The study groups are: (I) normal Ca(0.47%) and normal VD (25 IU/day/rat), (II) low Ca + low VD, (III) low Ca + low VD + low CPIF (10 mg/kg diet), (IV) low Ca + low VD + high CPIF (25 mg/kg diet) and (V) low Ca + low VD + 17-(-estradiol (3.2 mg/kg diet). After the development of OSP the group II was subgrouped into: (SG I) continued on low Ca + VD, (SG II) low CPIF, (SG III) high CPIF, (SG IV) 17-β-estradiol and (SG V) normal Ca and VD. Serum 25-VD levels were in the range of 14–38 ng/ml in groups I, III, IV and V, where as the values were very low in the group II (5.8 ng/ml). These were partially reversed upon supplementation of CPIF. The results correlated with altered Ca levels, body weight, bone mineral density and content and other related biochemical parameters. The paper further explains the possibility of protective and therapeutic role of VD in the presence of CPIF in osteoporotic health manifestations.

Adaptation of bone and calcium metabolism to low dietary calcium (Ca) stress is affected by genetic background in mice

We tested the hypothesis that Gene × Diet interactions influence adaptation of Ca and bone metabolism to low Ca intake using inbred mice. Male C57BL/6J (B6), DBA/2J (DBA), and PWK/PhJ (PWK) mice were fed diets containing adequate (0.5%) or low (0.25%) Ca levels from weaning until 3 mo (n=6–12 per group) when 45Ca absorption (Ca Abs) was assessed after an overnight fast (n=6 per group), serum was harvested for vitamin D metabolite levels, and femura were fixed for DEXA analysis of bone mineral density (BMD). Significant differences between the lines on the 0.5% Ca diet were observed for body weight (B6&gt;DBA&gt;PWK), BMD (DBA&gt;B6&gt;PWK), serum 25 hydroxyvitamin D (B6&gt;DBA&gt;PWK), serum 1,25 dihydroxyvitamin D (1,25 D; DBA&gt;B6=PWK), and Ca Abs (B6&gt;DBA=PWK). Ca restriction reduced BMD only in DBA mice (10.6% lower) and this was partly explained by their inability to increase serum 1,25 D and Ca Abs; low Ca diet increased serum 1,25 D and Ca Abs by 70% and 60%, respectively in B6 mice and by 97% and 11%, respectively in PWK mice. These data suggest there are genetic factors influencing basal levels of vitamin D and calcium metabolism in inbred mouse lines as well as the adaptation of Ca metabolism to dietary Ca restriction in DBA mice. Future forward genetic approaches will be necessary to identify the genetic variation responsible for these physiological differences. Supported by NIH Award DK054111 and funds from Purdue University

The effect of dietary calcium on 1,25(OH) 2D 3 synthesis and sparing of serum 25(OH)D 3 levels

Vitamin D depletion in rats causes osteopenia in at least three skeletal sites. However it is unclear whether modulation of dietary calcium intake impacts on the relationship between the level of serum 25-hydroxyvitamin D (25D) and bone loss. Nine-month-old female Sprague–Dawley rats ( n = 5–6/group) were pair-fed a semi-synthetic diet containing either 0 or 20 IU vitamin D3/day with either low (0.1%) or high (1%) dietary Ca for 6 months. At 15 months of age, fasting bloods were collected for biochemical analyses. Serum 25D levels were lowest in the animals fed 0 IU vitamin D and 0.1% Ca. The animals fed 1% Ca had significantly higher serum 25D levels when compared to animals fed 0.1% Ca ( P < 0.05). The major determinants of serum 25D were dietary vitamin D and dietary calcium (Multiple R = 0.75, P < 0.05). Animals fed 0.1% Ca had higher renal CYP27B1 mRNA expression and 12–18-fold increased levels of serum 1,25D. Hence, the reported effects of low calcium diets on bone loss may be, in part, due to the subsequent effects of 25D metabolism leading to reduction in vitamin D status. Such an interaction has significant implications, given the recent evidence for local synthesis of active vitamin D in bone tissue.

The interactive effect of phytase and coccidia on the gross lesions as well as the absorption capacity of intestine in broilers fed with diets low in calcium and available phosphorous

In an experiment with 2 × 2 factorial design, the influence of dietary phytase on the intestinal lesions as well as the absorption capacity of intestine for d-xylose in broiler chickens provided with a diet low in calcium (Ca) and available phosphorus (aP) and challenged with Eimeria oocysts, was evaluated. Four groups of 20 1-day-old male broiler were provided with diets low in total Ca and aP (8 and 3 g/kg instead of 10 and 5 g/kg of Ca and aP in the diet, respectively). On day 10, 10 chicks from each group were randomly kept in individual raised floor wire cages to adopt environmental conditions. The experimental groups were as follows, Group 1: received no Eimeria oocysts (negative control), Group 2: received oocysts of mixed Eimeria species on day 15 to create an experimental coccidiosis (positive control), Group 3: negative control received phytase enzyme in their diet, from the first day of life, and Group 4: positive control received phytase enzyme in the diet. On day 20, after 12 h fasting, the d-xylose absorption test was performed and immediately after that, the intestinal lesion scoring was carried out. The results showed that coccidiosis in Groups 2 and 4 produced progressive lesions in intestinal tract and reduced the concentration of plasma d-xylose in Group 2 when compared to Groups 1 and 3. Dietary phytase had no influence on the concentration of plasma d-xylose in un-infected birds. The enzyme had no influence on the intestinal lesions caused by coccidiosis as well. However, it increased the plasma d-xylose concentration of Group 4 to the level that it was comparable with Groups 1 and 3, at 45 and 90 min post-ingestion of the solution. It was concluded that the addition of phytase enzyme to the low Ca and aP diet, increased indirectly the absorption capacity of intestine for d-xylose in infected chickens most probably through the improvement of mechanisms involved in the absorption and transport of d-xylose.