<i>Ex vivo</i> intestinal studies on calcium and phosphate transport in growing goats fed a reduced nitrogen diet

Muscher, A. S.; Wilkens, Mirja R.; Mrochen, Nina; Schröder, Bernd; Breves, Gerhard; Huber, Korinna

doi:10.1017/s0007114511005976

Cited by 12 publications

(12 citation statements)

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“…A reduction of dietary N led to decreased expression of the apical Ca channel TRPV6 revealed by two-way ANOVA and in combination with a reduced dietary Ca supply led to significantly decreased expression compared with solitary Ca reduction, whereas the latter stimulated TRPV6 expression in all the intestinal segments. These findings were in accordance with results from studies with young goats fed a simultaneous N-and Ca-reduced diet, showing reduced TRPV6 expression in mid-jejunum (11) , and adult goats on a Ca-restricted diet having increased expression levels of TRPV6 (12) . Expression of the intracellular CaBP D9K diminished in all the intestinal segments due to the reduced dietary N content.…”

Section: Discussionsupporting

confidence: 91%

“…In former studies by Muscher et al (11) , a simultaneous dietary N and Ca reduction led to an increase in intestinal Ca absorption in the mid-jejunum of young goats. This may have been due to a lower body weight gain, and therefore lower Ca requirement of goats, in the control group in this former study, which was then stimulated by reducing the amounts of Ca and N.…”

Section: Discussionmentioning

confidence: 91%

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Modulation of intestinal calcium and phosphate transport in young goats fed a nitrogen- and/or calcium-reduced diet

Elfers¹,

Wilkens²,

Breves³

et al. 2015

Br J Nutr

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Feeding ruminants a reduced N diet is a common approach to reduce N output based on rumino-hepatic circulation. However, a reduction in N intake caused massive changes in Ca and inorganic phosphate (P i ) homoeostasis in goats. Although a single dietary Ca reduction stimulated intestinal Ca absorption in a calcitriol-dependent manner, a concomitant reduction of Ca and N supply led to a decrease in calcitriol, and therefore a modulation of intestinal Ca and P i absorption. The aim of this study was to examine the potential effects of dietary N or Ca reduction separately on intestinal Ca and P i transport in young goats. Animals were allocated to a control, N-reduced, Ca-reduced or combined N-and Ca-reduced diet for about 6 − 8 weeks, whereby N content was reduced by 25 % compared with recommendations. In Ussing chamber experiments, intestinal Ca flux rates significantly decreased in goats fed a reduced N diet, whereas P i flux rates were unaffected. In contrast, a dietary Ca reduction stimulated Ca flux rates and decreased P i flux rates. The combined dietary N and Ca reduction withdrew the stimulating effect of dietary Ca reduction on Ca flux rates. The expression of Ca-transporting proteins decreased with a reduced N diet too, whereas P i -transporting proteins were unaffected. In conclusion, a dietary N reduction decreased intestinal Ca transport by diminishing Ca-transporting proteins, which became clear during simultaneous N and Ca reduction. Therefore, N supply in young ruminant nutrition is of special concern for intestinal Ca transport.Key words: Flux rates of calcium and phosphate: Goats: Na + -dependent P i transporter IIb: Transient receptor potential vanilloid channel type 6: Ussing chambersFeeding ruminants a N-reduced diet is preferable for economic and environmental reasons. Dietary crude protein (CP) concentrations of 11 − 12 % were recommended to meet the requirements of growing goats (1) . A reduced dietary N supply was associated with a significant reduction in urinary N excretion (2) due to increased expression of renal urea transporters, and thus greater renal urea re-absorption (3) in goats. In addition, the urea transporting capacity of the ruminal epithelium was increased due to dietary N reduction (4) . By possessing such efficient recycling mechanisms, ruminants such as goats are able to maintain rumen microbes' N supply, and therefore a sufficient synthesis of microbial protein as the most important source for host protein, provided that energy supply to the rumen flora is also adequate for microbial protein synthesis.As monogastric species do not have the similar potential to utilise N efficiently, a low-protein diet changes metabolic pathways seriously. A reduction of dietary protein leads to changes in Ca and inorganic phosphate (P i ) homoeostasis in monogastric animals and humans, including decrease in intestinal Ca absorption, reduced urinary Ca excretion and diminished plasma calcitriol and insulin-like growth factor 1 (IGF1) concentrations (5)(6)(7)(8) .Despite the N-rec...

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Section: Discussionsupporting

confidence: 91%

Section: Discussionmentioning

confidence: 91%

Modulation of intestinal calcium and phosphate transport in young goats fed a nitrogen- and/or calcium-reduced diet

Elfers¹,

Wilkens²,

Breves³

et al. 2015

Br J Nutr

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“…Own previous studies have shown that dietary N reduction affected overall Ca homeostasis in young goats leading to a decrease in plasma calcitriol concentrations and intestinal transcellular Ca absorption [ 5 , 6 ]. Additionally, though a single dietary Ca reduction stimulated intestinal Ca absorption in young and adult goats [ 5 , 7 ]; a concomitant reduction in N supply eliminated this stimulating effect in young goats [ 5 , 8 ]. Diminished transcellular Ca absorption in goats fed an N reduction or an N and Ca reduction was associated with reduced plasma calcitriol concentrations as the main regulator of transcellular Ca transport in the small intestine [ 5 ].…”

Section: Introductionmentioning

confidence: 99%

Expression of Tight Junction Proteins and Cadherin 17 in the Small Intestine of Young Goats Offered a Reduced N and/or Ca Diet

et al. 2016

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Diets fed to ruminants should contain nitrogen (N) as low as possible to reduce feed costs and environmental pollution. Though possessing effective N-recycling mechanisms to maintain the N supply for rumen microbial protein synthesis and hence protein supply for the host, an N reduction caused substantial changes in calcium (Ca) and phosphate homeostasis in young goats including decreased intestinal transepithelial Ca absorption as reported for monogastric species. In contrast to the transcellular component of transepithelial Ca transport, the paracellular route has not been investigated in young goats. Therefore, the aim of the present study was to characterise the effects of dietary N and/or Ca reduction on paracellular transport mechanisms in young goats. Electrophysiological properties of intestinal epithelia were investigated by Ussing chamber experiments. The expression of tight junction (TJ) and adherens junction (AJ) proteins in intestinal epithelia were examined on mRNA level by qPCR and on protein level by western blot analysis. Dietary N reduction led to a segment specific increase in tissue conductances in the proximal jejunum which might be linked to concomitantly decreased expression of cadherin 17 mRNA. Expression of occludin (OCLN) and zonula occludens protein 1 was increased in mid jejunal epithelia of N reduced fed goats on mRNA and partly on protein level. Reduced dietary Ca supply resulted in a segment specific increase in claudin 2 and claudin 12 expression and decreased the expression of OCLN which might have been mediated at least in part by calcitriol. These data show that dietary N as well as Ca reduction affected expression of TJ and AJ proteins in a segment specific manner in young goats and may thus be involved in modulation of paracellular Ca permeability.

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“…Muscher et al have also recently suggested a post-transcriptional regulation of TRPV6 in goats fed a reduced nitrogen and calcium diet. 23 Because there was an inverse relationship between intestinal calcium and iron absorption, 24 the enhanced intestinal iron absorption that was commonly observed in b-thalassemic mice, 12 presumably because of the thalassemia-induced upregulation of DMT1 transcription (Figure 2(A)), could partly explain the decrease in the duodenal calcium transport. The cellular mechanism of the iron hyperabsorption-induced suppression of intestinal calcium absorption remains elusive; however, the elevated intracellular iron concentration has been known to increase reactive oxygen species, which can reduce the PMCA activity.…”

Section: Discussionmentioning

confidence: 99%

1,25‐Dihydroxyvitamin D₃‐induced intestinal calcium transport is impaired in β‐globin knockout thalassemic mice

Charoenphandhu

Kraidith

Teerapornpuntakit

et al. 2013

Cell Biochemistry & Function

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Besides being a common haematological disorder caused by a reduction in β-globin production, β-thalassemia has been reported to impair body calcium homeostasis, leading to massive bone loss and increased fracture risk. Here, we demonstrated that heterozygous β-globin knockout thalassemic mice had a lower rate of duodenal calcium absorption compared with the wild-type littermates, whereas the epithelial electrical parameters, including transepithelial resistance, were not affected, suggesting no change in the epithelial integrity and permeability. Daily subcutaneous injection of 1 µg kg(-1) 1,25-dihydroxyvitamin D3 [1,25(OH)2 D3 ] for 3 days enhanced the duodenal calcium absorption in wild-type, but not in thalassemic mice. Although β-thalassemia increased the mRNA level of divalent metal transporter-1, an iron transporter in the duodenum, it had no effect on the transcripts of ferroportin-1 or the principal calcium transporters. In conclusion, β-thalassemia impaired the 1,25(OH)2 D3 -dependent intestinal calcium absorption at the post-transcriptional level, which, in turn, contributed to the dysregulation of body calcium metabolism and β-thalassemia-induced osteopenia.

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Ex vivo intestinal studies on calcium and phosphate transport in growing goats fed a reduced nitrogen diet

Cited by 12 publications

References 37 publications

Modulation of intestinal calcium and phosphate transport in young goats fed a nitrogen- and/or calcium-reduced diet

Modulation of intestinal calcium and phosphate transport in young goats fed a nitrogen- and/or calcium-reduced diet

Expression of Tight Junction Proteins and Cadherin 17 in the Small Intestine of Young Goats Offered a Reduced N and/or Ca Diet

1,25‐Dihydroxyvitamin D₃‐induced intestinal calcium transport is impaired in β‐globin knockout thalassemic mice

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Ex vivo intestinal studies on calcium and phosphate transport in growing goats fed a reduced nitrogen diet

Cited by 12 publications

References 37 publications

Modulation of intestinal calcium and phosphate transport in young goats fed a nitrogen- and/or calcium-reduced diet

Modulation of intestinal calcium and phosphate transport in young goats fed a nitrogen- and/or calcium-reduced diet

Expression of Tight Junction Proteins and Cadherin 17 in the Small Intestine of Young Goats Offered a Reduced N and/or Ca Diet

1,25‐Dihydroxyvitamin D3‐induced intestinal calcium transport is impaired in β‐globin knockout thalassemic mice

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1,25‐Dihydroxyvitamin D₃‐induced intestinal calcium transport is impaired in β‐globin knockout thalassemic mice