Faecal steroid excretion in humans is affected by calcium supplementation and shows gender-specific differences

Bile acids as metabolic regulators: an update

PURPOSE OF REVIEW

This review aims to provide a concise update on recent advances in understanding of the bile acid metabolism and signaling in health and diseases.

RECENT FINDINGS

CYP2C70 has been identified as the murine cytochrome p450 enzyme that mediates the synthesis of muricholic acids to account for the major different bile acid composition between human and mice. Several studies have linked nutrient sensing bile acid signaling to the regulation of hepatic autophagy-lysosome activity, an integral pathway of the cellular adaptive response to starvation. Distinct bile acid-mediated signaling mechanisms have been shown to contribute to the complex metabolic changes post bariatric surgery, suggesting that pharmacological manipulation of the enterohepatic bile acid signaling could be a potential nonsurgical alternative to weight loss surgery.

SUMMARY

Basic and clinical studies have continued to discover novel roles of the enterohepatic bile acid signaling in regulation of key metabolic pathways. Such knowledge forms the molecular basis needed for developing safe and effective bile acid-based therapeutics for treating metabolic and inflammatory diseases.

Combining ASBT inhibitor and FGF15 treatments enhances therapeutic efficacy against cholangiopathy in female but not male Cyp2c70 KO mice

Therapeutic reduction of hydrophobic bile acids exposure is considered beneficial in cholestasis. The Cyp2c70 KO mice lack hydrophilic muricholic acids and have a human-like hydrophobic bile acid pool resulting in hepatobiliary injury. This study investigates if combining an apical sodium-dependent bile acid transporter inhibitor GSK2330672 (GSK) and fibroblast growth factor-15 (FGF15) overexpression, via simultaneous inhibition of bile acid synthesis and gut bile acid uptake, achieves enhanced therapeutic efficacy in alleviating hepatobiliary injury in Cyp2c70 KO mice. The effects of GSK, adeno-associated virus (AAV)-FGF15, and the combined treatment on bile acid metabolism and cholangiopathy were compared in Cyp2c70 KO mice. In female Cyp2c70 KO mice with more severe cholangiopathy than male Cyp2c70 KO mice, the combined treatment was more effective in reversing portal inflammation, ductular reaction, and fibrosis than AAV-FGF15, while GSK was largely ineffective. The combined treatment reduced bile acid pool by ∼80% compared to ∼50% reduction by GSK or AAV-FGF15, and enriched tauro-conjugated ursodeoxycholic acid in the bile. Interestingly, the male Cyp2c70 KO mice treated with AAV-FGF15 or GSK showed attenuated cholangiopathy and portal fibrosis but the combined treatment was ineffective despite reducing bile acid pool. Both male and female Cyp2c70 KO mice showed impaired gut barrier integrity. AAV-FGF15 and the combined treatment, but not GSK, reduced gut exposure to lithocholic acid and improved gut barrier function. In conclusion, the combined treatment improved therapeutic efficacy against cholangiopathy than either single treatment in the female but not male Cyp2c70 KO mice by reducing bile acid pool size and hydrophobicity.

Role of calcium on lipid digestion and serum lipids: a review

Calcium is an essential nutrient for humans that can be taken as supplement or in a food matrix (e.g. dairy products). It is suggested that dietary calcium may have a beneficial effect on cardiovascular risk but the mechanism is not clear. In this review, the main mechanisms of the possible cholesterol-lowering effect of calcium, i.e. interaction with fatty acids and bile acids, are described and clinical evidences are presented. The observations from interventional studies of the possible cholesterol-lowering effect in terms of the main related mechanisms are variable and do not seem to fulfill all the related aspects. It seems that the interplay of calcium in blood lipid metabolism might be due to its complex and multiple roles in the lipid digestion in the small intestine. The interactions between calcium and, fatty acids and bile may lead to impaired mixed micelle formation and solubilization, which is crucial in the lipid absorption and metabolism. In addition, the calcium source and its surrounding matrix will have an influence over the physiological outcome. This research is important for the delivery and formulation of calcium, particularly with the move toward plant-based diets.

Influence of Age, Sex, and Diet on the Human Fecal Metabolome Investigated by 1H NMR Spectroscopy

The human fecal metabolome is increasingly studied to explore the impact of diet and lifestyle on health and the gut microbiome. However, systematic differences and confounding factors related to age, sex, and diet remain largely unknown. In this study, absolute concentrations of fecal metabolites from 205 healthy Danes (105 males and 100 females, 49 ± 31 years old) were quantified using ¹H NMR spectroscopy and the newly developed SigMa software. The largest systemic variation was found to be highly related to age. Fecal concentrations of short-chain fatty acids (SCFA) were higher in the 18 years old group, while amino acids (AA) were higher in the elderly. Sex-related metabolic differences were weak but significant and mainly related to changes in SCFA. The concentrations of butyric, valeric, propionic, and isovaleric acids were found to be higher in males compared to females. Sex differences were associated with a stronger, possibly masking, effect from differential intake of macronutrients. Dietary fat intake decreased levels of SCFA and AA of both sexes, while carbohydrate intake showed weak correlations with valeric and isovaleric acids in females. This study highlights some possible demographic confounders linked to diet, disease, lifestyle, and microbiota that have to be taken into account when analyzing fecal metabolome data.

Effect of Calcium Fortified Foods on Health Outcomes: A Systematic Review and Meta-Analysis

Calcium supplementation and fortification are strategies widely used to prevent adverse outcome in population with low-calcium intake which is highly frequent in low-income settings. We aimed to determine the effectiveness and cost-effectiveness of calcium fortified foods on calcium intake and related health, or economic outcomes. We performed a systematic review and meta-analysis involving participants of any age or gender, drawn from the general population. We searched PubMed, Agricola, EMBASE, CINAHL, Global Health, EconLit, the FAO website and Google until June 2019, without language restrictions. Pair of reviewers independently selected, extracted data and assessed the risk of bias of included studies using Covidence software. Disagreements were resolved by consensus. We performed meta-analyses using RevMan 5.4 and subgroup analyses by study design, age group, and fortification levels. We included 20 studies of which 15 were randomized controlled trials (RCTs), three were non-randomised studies and two were economic evaluations. Most RCTs had high risk of bias on randomization or blinding. Most represented groups were women and children from 1 to 72 months, most common intervention vehicles were milk and bakery products with a fortification levels between 96 and 1200 mg per 100 g of food. Calcium intake increased in the intervention groups between 460 mg (children) and 1200 mg (postmenopausal women). Most marked effects were seen in children. Compared to controls, height increased 0.83 cm (95% CI 0.00; 1.65), plasma parathyroid hormone decreased -1.51 pmol/L, (-2.37; -0.65), urine:calcium creatinine ratio decreased -0.05, (-0.07; -0.03), femoral neck and hip bone mineral density increased 0.02 g/cm2 (0.01; 0.04) and 0.03 g/cm2 (0.00; 0.06), respectively. The largest cost savings (43%) reported from calcium fortification programs came from prevented hip fractures in older women from Germany. Our study highlights that calcium fortification leads to a higher calcium intake, small benefits in children's height and bone health and also important evidence gaps for other outcomes and populations that could be solved with high quality experimental or quasi-experimental studies in relevant groups, especially as some evidence of calcium supplementation show controversial results on the bone health benefit on older adults.

Clostridium scindens ATCC 35704: Integration of Nutritional Requirements, the Complete Genome Sequence, and Global Transcriptional Responses to Bile Acids

In the human gut, Clostridium scindens ATCC 35704 is a predominant bacterium and one of the major bile acid 7α-dehydroxylating anaerobes. While this organism is well-studied relative to bile acid metabolism, little is known about the basic nutrition and physiology of C. scindens ATCC 35704. To determine the amino acid and vitamin requirements of C. scindens, the leave-one-out (one amino acid group or vitamin) technique was used to eliminate the nonessential amino acids and vitamins. With this approach, the amino acid tryptophan and three vitamins (riboflavin, pantothenate, and pyridoxal) were found to be required for the growth of C. scindens In the newly developed defined medium, C. scindens fermented glucose mainly to ethanol, acetate, formate, and H_2. The genome of C. scindens ATCC 35704 was completed through PacBio sequencing. Pathway analysis of the genome sequence coupled with transcriptome sequencing (RNA-Seq) under defined culture conditions revealed consistency with the growth requirements and end products of glucose metabolism. Induction with bile acids revealed complex and differential responses to cholic acid and deoxycholic acid, including the expression of potentially novel bile acid-inducible genes involved in cholic acid metabolism. Responses to toxic deoxycholic acid included expression of genes predicted to be involved in DNA repair, oxidative stress, cell wall maintenance/metabolism, chaperone synthesis, and downregulation of one-third of the genome. These analyses provide valuable insight into the overall biology of C. scindens which may be important in treatment of disease associated with increased colonic secondary bile acids.IMPORTANCE C. scindens is one of a few identified gut bacterial species capable of converting host cholic acid into disease-associated secondary bile acids such as deoxycholic acid. The current work represents an important advance in understanding the nutritional requirements and response to bile acids of the medically important human gut bacterium, C. scindens ATCC 35704. A defined medium has been developed which will further the understanding of bile acid metabolism in the context of growth substrates, cofactors, and other metabolites in the vertebrate gut. Analysis of the complete genome supports the nutritional requirements reported here. Genome-wide transcriptomic analysis of gene expression in the presence of cholic acid and deoxycholic acid provides a unique insight into the complex response of C. scindens ATCC 35704 to primary and secondary bile acids. Also revealed are genes with the potential to function in bile acid transport and metabolism.

Bile Acid 7α-Dehydroxylating Gut Bacteria Secrete Antibiotics that Inhibit Clostridium difficile: Role of Secondary Bile Acids

Clostridium scindens biotransforms primary bile acids into secondary bile acids, and is correlated with inhibition of Clostridium difficile growth in vivo. The aim of the current study was to determine how C. scindens regulates C. difficile growth in vitro and if these interactions might relate to the regulation of gut microbiome structure in vivo. The bile acid 7α-dehydroxylating gut bacteria, C. scindens and C. sordellii, were found to secrete the tryptophan-derived antibiotics, 1-acetyl-β-carboline and turbomycin A, respectively. Both antibiotics inhibited growth of C. difficile and other gut bacteria. The secondary bile acids, deoxycholic acid and lithocholic acid, but not cholic acid, enhanced the inhibitory activity of these antibiotics. These antibiotics appear to inhibit cell division of C. difficile. The results help explain how endogenously synthesized antibiotics and secondary bile acids may regulate C. difficile growth and the structure of the gut microbiome in health and disease.

Calcium and Phosphate Metabolism, Blood Lipids and Intestinal Sterols in Human Intervention Studies Using Different Sources of Phosphate as Supplements-Pooled Results and Literature Search

Phosphates are associated with negative physiological effects. The objectives of this publication were to compare differential effects of supplementation with calcium phosphate or phosphate alone in healthy humans. Four adult human studies were conducted with pentacalcium hydroxy-trisphosphate supplementation (CaP; 90 subjects) and their data were pooled for assessment. For literature search; PubMed and ISI Web of Knowledge were used and 21 items were assigned to three main topics. The pooled study results show that following CaP supplementation, faecal calcium and phosphorus and urinary calcium were increased, blood lipids were positively modulated, and faecal bile acids were increased, as compared with placebo. The literature search reveals that following calcium phosphate supplementation, urinary calcium was increased. Following solely phosphate supplementation, urinary phosphorus was increased and urinary calcium was decreased. Postprandial calcium concentrations were increased following calcium phosphate supplementation. Postprandial phosphate concentrations were increased following solely phosphate supplementation. Calcium phosphate supplementation resulted in rather positively modulated blood lipids and gut-related parameters. The presented results show the relevance to distinguish between calcium phosphate and solely phosphate supplementations, and the importance of a balanced calcium and phosphorus intake.

Metabolism of Oxo-Bile Acids and Characterization of Recombinant 12α-Hydroxysteroid Dehydrogenases from Bile Acid 7α-Dehydroxylating Human Gut Bacteria

Bile acids are important cholesterol-derived nutrient signaling hormones, synthesized in the liver, that act as detergents to solubilize dietary lipids. Bile acid 7α-dehydroxylating gut bacteria generate the toxic bile acids deoxycholic acid and lithocholic acid from host bile acids. The ability of these bacteria to remove the 7-hydroxyl group is partially dependent on 7α-hydroxysteroid dehydrogenase (HSDH) activity, which reduces 7-oxo-bile acids generated by other gut bacteria. 3α-HSDH has an important enzymatic activity in the bile acid 7α-dehydroxylation pathway. 12α-HSDH activity has been reported for the low-activity bile acid 7α-dehydroxylating bacterium Clostridium leptum; however, this activity has not been reported for high-activity bile acid 7α-dehydroxylating bacteria, such as Clostridium scindens, Clostridium hylemonae, and Clostridium hiranonis Here, we demonstrate that these strains express bile acid 12α-HSDH. The recombinant enzymes were characterized from each species and shown to preferentially reduce 12-oxolithocholic acid to deoxycholic acid, with low activity against 12-oxochenodeoxycholic acid and reduced activity when bile acids were conjugated to taurine or glycine. Phylogenetic analysis suggests that 12α-HSDH is widespread among Firmicutes, Actinobacteria in the Coriobacteriaceae family, and human gut ArchaeaIMPORTANCE 12α-HSDH activity has been established in the medically important bile acid 7α-dehydroxylating bacteria C. scindens, C. hiranonis, and C. hylemonae Experiments with recombinant 12α-HSDHs from these strains are consistent with culture-based experiments that show a robust preference for 12-oxolithocholic acid over 12-oxochenodeoxycholic acid. Phylogenetic analysis identified novel members of the gut microbiome encoding 12α-HSDH. Future reengineering of 12α-HSDH enzymes to preferentially oxidize cholic acid may provide a means to industrially produce the therapeutic bile acid ursodeoxycholic acid. In addition, a cholic acid-specific 12α-HSDH expressed in the gut may be useful for the reduction in deoxycholic acid concentration, a bile acid implicated in cancers of the gastrointestinal (GI) tract.

Targeted Synthesis and Characterization of a Gene Cluster Encoding NAD(P)H-Dependent 3α-, 3β-, and 12α-Hydroxysteroid Dehydrogenases from Eggerthella CAG:298, a Gut Metagenomic Sequence

Gut metagenomic sequences provide a rich source of microbial genes, the majority of which are annotated by homology or unknown. Genes and gene pathways that encode enzymes catalyzing biotransformation of host bile acids are important to identify in gut metagenomic sequences due to the importance of bile acids in gut microbiome structure and host physiology. Hydroxysteroid dehydrogenases (HSDHs) are pyridine nucleotide-dependent enzymes with stereospecificity and regiospecificity for bile acid and steroid hydroxyl groups. HSDHs have been identified in several protein families, including medium-chain and short-chain dehydrogenase/reductase families as well as the aldo-keto reductase family. These protein families are large and contain diverse functionalities, making prediction of HSDH-encoding genes difficult and necessitating biochemical characterization. We located a gene cluster in Eggerthella sp. CAG:298 predicted to encode three HSDHs (CDD59473, CDD59474, and CDD59475) and synthesized the genes for heterologous expression in Escherichia coli We then screened bile acid substrates against the purified recombinant enzymes. CDD59475 is a novel 12α-HSDH, and we determined that CDD59474 (3α-HSDH) and CDD59473 (3β-HSDH) constitute novel enzymes in an iso-bile acid pathway. Phylogenetic analysis of these HSDHs with other gut bacterial HSDHs and closest homologues in the database revealed predictable clustering of HSDHs by function and identified several likely HSDH sequences from bacteria isolated or sequenced from diverse mammalian and avian gut samples.IMPORTANCE Bacterial HSDHs have the potential to significantly alter the physicochemical properties of bile acids, with implications for increased/decreased toxicity for gut bacteria and the host. The generation of oxo-bile acids is known to inhibit host enzymes involved in glucocorticoid metabolism and may alter signaling through nuclear receptors such as farnesoid X receptor and G-protein-coupled receptor TGR5. Biochemical or similar approaches are required to fill in many gaps in our ability to link a particular enzymatic function with a nucleic acid or amino acid sequence. In this regard, we have identified a novel 12α-HSDH and a novel set of genes encoding an iso-bile acid pathway (3α-HSDH and 3β-HSDH) involved in epimerization and detoxification of harmful secondary bile acids.

High phosphorus intake and gut-related parameters - results of a randomized placebo-controlled human intervention study

Background

In recent years, high phosphate intakes were discussed critically. In the small intestine, a part of the ingested phosphate and calcium precipitates to amorphous calcium phosphate (ACP), which in turn can precipitate other intestinal substances, thus leading to a beneficial modulation of the intestinal environment. Therefore, we analysed faecal samples obtained from a human intervention study regarding gut-related parameters.

Methods

Sixty-two healthy subjects (men, n = 30; women, n = 32) completed the double-blind, placebo-controlled and parallel designed study (mean age: 29 ± 7 years; mean BMI: 24 ± 3 kg/m²). Supplements were monosodium phosphate and calcium carbonate. During the first 2 weeks, all groups consumed a placebo sherbet powder, and afterwards a sherbet powder for 8 weeks according to the intervention group: P1000/Ca0 (1000 mg/d phosphorus), P1000/Ca500 (1000 mg/d phosphorus and 500 mg/d calcium) and P1000/Ca1000 (1000 mg/d phosphorus and 1000 mg/d calcium). After the placebo period and after 8 weeks of intervention faecal collections took place. We determined in faeces: short-chain fatty acids (SCFA) and fat as well as the composition of the microbiome (subgroup) and cyto- and genotoxicity of faecal water (FW). By questionnaire evaluation we examined tolerability of the used phosphorus supplement.

Results

Faecal fat concentrations did not change significantly due to the interventions. Concentrations of faecal total SCFA and acetate were significantly higher after 8 weeks of P1000/Ca500 supplementation compared to the P1000/Ca0 supplementation. In men, faecal total SCFA and acetate concentrations were significantly higher after 8 weeks in the P1000/Ca1000 group compared to the P1000/Ca0 one. None of the interventions markedly affected cyto- and genotoxic activity of FW. Men of the P1000/Ca1000 intervention had a significantly different gut microbial community compared to the men of the P1000/Ca0 and P1000/Ca500 ones. The genus Clostridium XVIII was significantly more abundant in men of the P1000/Ca1000 intervention group compared to the other groups. Supplementations did not cause increased intestinal distress.

Conclusions

The used high phosphorus diet did not influence cyto- and genotoxicity of FW and the concentrations of faecal fat independent of calcium intake. Our study provides first hints for a potential phosphorus-induced modulation of the gut community and the faecal total SCFA content.

Trial registration

The trial is registered at ClinicalTrials.gov as NCT02095392.

Electronic supplementary material

The online version of this article (10.1186/s12937-018-0331-4) contains supplementary material, which is available to authorized users.

Deoxycholic acid mediates non-canonical EGFR-MAPK activation through the induction of calcium signaling in colon cancer cells

Obesity and a western diet have been linked to high levels of bile acids and the development of colon cancer. Specifically, increased levels of the bile acid deoxycholic acid (DCA), an established tumor promoter, has been shown to correlate with increased development of colorectal adenomas and progression to carcinoma. Herein we investigate the mechanism by which DCA leads to EGFR-MAPK activation, a candidate mechanism by which DCA may promote colorectal tumorigenesis. DCA treated colon cancer cells exhibited strong and prolonged activation of ERK1/2 when compared to EGF treatment alone. We also showed that DCA treatment prevents EGFR degradation as opposed to the canonical EGFR recycling observed with EGF treatment. Moreover, the combination of DCA and EGF treatment displayed synergistic activity, suggesting DCA activates MAPK signaling in a non-canonical manner. Further evaluation showed that DCA treatment increased intracellular calcium levels and CAMKII phosphorylation, and that blocking calcium with BAPTA-AM abrogated MAPK activation induced by DCA, but not by EGF. Finally we showed that DCA-induced CAMKII leads to MAPK activation through the recruitment of c-Src. Taken together, we demonstrated that DCA regulates MAPK activation through calcium signaling, an alternative mechanism not previously recognized in human colon cancer cells. Importantly, this mechanism allows for EGFR to escape degradation and thus achieve a constitutively active state, which may explain its tumor promoting effects.

Mechanisms of calcium intake in lowering serum cholesterol levels

Cardiovascular diseases (CVDs), a group of disorders of the heart and blood vessels, are the leading cause of death globally. An estimated 17.1 million people die of CVDs each year, more than 40% of whom die from coronary heart disease (CHD). Hypercholesterolemia is a major risk factor for increasing CHD morbidity and mortality, and serum cholesterol level is a key predictor of CHD development. A number of studies have demonstrated that calcium supplement can lower serum cholesterol levels, which means that calcium might play an important role in preventing the development of CVDs, especially CHD. In this paper, the mechanisms of calcium intake in lowering serum cholesterol levels are summarized, including increasing the excretion of bile acids, interfering with cholesterol absorption, inhibiting the absorption of saturated fatty acids, promoting energy metabolism, regulating plasma 1,25(OH)₂D levels, affecting blood insulin sensibility and controlling appetite.

Could the beneficial effects of dietary calcium on obesity and diabetes control be mediated by changes in intestinal microbiota and integrity?

Evidence from animal and human studies has associated gut microbiota, increased translocation of lipopolysaccharide (LPS) and reduced intestinal integrity (II) with the inflammatory state that occurs in obesity and type 2 diabetes mellitus (T2DM). Consumption of Ca may favour body weight reduction and glycaemic control, but its influence on II and gut microbiota is not well understood. Considering the impact of metabolic diseases on public health and the role of Ca on the pathophysiology of these diseases, this review critically discusses possible mechanisms by which high-Ca diets could affect gut microbiota and II. Published studies from 1993 to 2015 about this topic were searched and selected from Medline/PubMed, Scielo and Lilacs databases. High-Ca diets seem to favour the growth of lactobacilli, maintain II (especially in the colon), reduce translocation of LPS and regulate tight-junction gene expression. We conclude that dietary Ca might interfere with gut microbiota and II modulations and it can partly explain the effect of Ca on obesity and T2DM control. However, further research is required to define the supplementation period, the dose and the type of Ca supplement (milk or salt) required for more effective results. As Ca interacts with other components of the diet, these interactions must also be considered in future studies. We believe that more complex mechanisms involving extraintestinal disorders (hormones, cytokines and other biomarkers) also need to be studied.

Effect of calcium phosphate and vitamin D₃ supplementation on bone remodelling and metabolism of calcium, phosphorus, magnesium and iron

BACKGROUND

The aim of the present study was to determine the effect of calcium phosphate and/or vitamin D₃ on bone and mineral metabolism.

METHODS

Sixty omnivorous healthy subjects participated in the double-blind, placebo-controlled parallel designed study. Supplements were tricalcium phosphate (CaP) and cholecalciferol (vitamin D₃). At the beginning of the study (baseline), all subjects documented their normal nutritional habits in a dietary record for three successive days. After baseline, subjects were allocated to three intervention groups: CaP (additional 1 g calcium/d), vitamin D₃ (additional 10 μg/d) and CaP + vitamin D₃. In the first two weeks, all groups consumed placebo bread, and afterwards, for eight weeks, the test bread according to the intervention group. In the last week of each study period (baseline, placebo, after four and eight weeks of intervention), a faecal (three days) and a urine (24 h) collection and a fasting blood sampling took place. Calcium, phosphorus, magnesium and iron were determined in faeces, urine and blood. Bone formation and resorption markers were analysed in blood and urine.

RESULTS

After four and eight weeks, CaP and CaP + vitamin D₃ supplementations increased faecal excretion of calcium and phosphorus significantly compared to placebo. Due to the vitamin D₃ supplementations (vitamin D₃, CaP + vitamin D₃), the plasma 25-(OH)D concentration significantly increased after eight weeks compared to placebo. The additional application of CaP led to a significant increase of the 25-(OH)D concentration already after four weeks. Bone resorption and bone formation markers were not influenced by any intervention.

CONCLUSIONS

Supplementation with daily 10 μg vitamin D₃ significantly increases plasma 25-(OH)D concentration. The combination with daily 1 g calcium (as CaP) has a further increasing effect on the 25-(OH)D concentration. Both CaP alone and in combination with vitamin D₃ have no beneficial effect on bone remodelling markers and on the metabolism of calcium, phosphorus, magnesium and iron.

TRIAL REGISTRATION

NCT01297023.

Effect of supplementary calcium phosphate on plasma gastrointestinal hormones in a double-blind, placebo-controlled, cross-over human study

Gastrointestinal hormones and Ca are associated with bone metabolism. The objective of the present human study was to determine the effect of calcium phosphate on the postprandial circulation of gastrointestinal hormones. A total of ten men participated in the present double-blind, placebo-controlled, cross-over study. The participants were divided into two groups. Of these, one group consumed bread enriched with 1 g Ca (pentacalcium hydroxy-triphosphate, CaP) daily for 3 weeks. The other group consumed placebo bread. After 2 weeks of washout, the intervention was changed between the groups for another 3 weeks. The subjects consumed a defined diet at the beginning (single administration) and at the end (repeated administration) of the intervention periods, and blood samples were drawn at 0, 30, 60, 120, 180 and 240 min. Between 0 and 30 min, the participants consumed a test meal, with or without CaP. The concentrations of gastrointestinal hormones (glucose-dependent insulinotropic polypeptide, glucagon-like peptide (GLP) 1 and GLP2), insulin and glucose were determined. The AUC of GLP1 (total and active) and GLP2 increased significantly after the repeated CaP administrations compared with that after placebo administration. The AUC of insulin and glucose showed no differences between the CaP and placebo administrations. CaP affects the postprandial plasma concentrations of gastrointestinal hormones through the modulation of the intestinal environment, e.g. bile acids and microbiota.

Postprandial effects of calcium phosphate supplementation on plasma concentration-double-blind, placebo-controlled cross-over human study

Background

The aim of the present study was to examine the postprandial calcium and phosphate concentrations after supplementation with pentacalcium hydroxy-triphosphate (CaP).

Methods

Ten men participated in this double-blind, placebo-controlled, cross-over study. The participants were divided into two groups. One group consumed bread enriched with CaP (plus 1 g calcium/d) and the other group a placebo product for three weeks. After a two week wash-out, the intervention was switched between the groups for another three weeks. Blood samples were drawn at the beginning (single administration) and at the end (repeated administration) of the intervention periods at 0, 30, 60, 120, 180 and 240 min. Between 0 and 30 min, a test meal, with or without CaP was consumed. The plasma concentrations of calcium and phosphate were examined. One participant dropped out due to personal reasons.

Results

CaP supplementation resulted in a significantly higher plasma calcium concentration after 240 min compared to placebo. After repeated CaP administration, the AUC for the increment in plasma calcium concentration was significantly higher compared to placebo.

After single and repeated CaP supplementation, plasma phosphate concentration significantly decreased after 30, 60, 120 and 180 min compared to 0 min. The placebo administration resulted in significant decreases after 30, 60 and 120 min compared to 0 min.

Conclusion

Our results show that CaP contributes to an adequate calcium supply, but without increasing the plasma concentration of phosphate.

Trial registration

http://www.clinicaltrials.gov; NCT01296997

A combination of calcium phosphate and probiotics beneficially influences intestinal lactobacilli and cholesterol metabolism in humans

BACKGROUND & AIMS

The study focuses on the influence of a probiotic supplement alone and in combination with a calcium supplement on faecal lactobacilli colonisation and beneficial health effects such as a lowering of blood cholesterol.

METHODS

Thirty-two men and women participated in the double-blind, placebo-controlled, cross-over study. All participants consumed a probiotic drink containing 10(10)CFU/d Lactobacillus paracasei (LPC37) for four weeks. In addition, one group consumed bread enriched with pentacalcium hydroxy-triphosphate (CaP; 1g Ca/d) and the other group had bread without CaP. After a two-week washout and a two-week placebo period, the intervention was switched for further four weeks.

RESULTS

After intervention with LPC37+CaP, total cholesterol and LDL-cholesterol concentration in plasma decreased significantly compared to LPC37 and placebo. The faecal concentration of L. paracasei and that of all lactobacilli increased significantly after LPC37+CaP and LPC37 compared to placebo. Moreover, secondary bile acids in faeces increased significantly after LPC37+CaP intervention compared to placebo.

CONCLUSIONS

CaP modulates the colonisation of LPC37 in the human gut under combinatory supplementation of CaP and LPC37. The combined supplementation also decreases plasma LDL-cholesterol and the LDL/HDL ratio in healthy, moderately hypercholesterolemic men and women, which could be also due to the CaP supplementation.

CLINICAL TRIAL REGISTRATION NUMBER

NCT01033461.