Lithocholic acid: a new emergent protector of intestinal calcium absorption under oxidant conditions (original) (raw)

Ursodeoxycholic and deoxycholic acids: A good and a bad bile acid for intestinal calcium absorption

Archives of biochemistry and biophysics, 2013

The aim of this study was to investigate the effect of ursodeoxycholic acid (UDCA) on intestinal Ca(2+) absorption and to find out whether the inhibition of this process caused by NaDOC could be prevented by UDCA. Chicks were employed and divided into four groups: (a) controls, (b) treated with 10mM NaDOC, (c) treated with 60 μg UDCA/100g of b.w., and (d) treated with 10mM NaDOC and 60 μg UDCA/100g of b.w. UDCA enhanced intestinal Ca(2+) absorption, which was time and dose-dependent. UDCA avoided the inhibition of intestinal Ca(2+) absorption caused by NaDOC. Both bile acids altered protein and gene expression of molecules involved in the transcellular pathway of intestinal Ca(2+) absorption, but in the opposite way. UDCA aborted the oxidative stress produced by NaDOC in the intestine. UDCA and UDCA plus NaDOC increased vitamin D receptor protein expression. In conclusion, UDCA is a beneficial bile acid for intestinal Ca(2+) absorption. Contrarily, NaDOC inhibits the intestinal cati...

Glycocholic acid and butyrate synergistically increase vitamin D-induced calcium uptake in Caco-2 intestinal epithelial cell monolayers

Bone Reports, 2020

Background: Roux-en-Y gastric bypass (RYGB) substantially decreases intestinal calcium absorption and may eventually lead to bone resorption. This is likely a consequence of bile diversion from the alimentary limb, as the presence of bile seems necessary for vitamin D-mediated calcium uptake. We recently suggested that the mediating mechanism may be a down-regulation of the vitamin D co-activator heat-shock protein (Hsp)90β. Recent evidence suggests that vitamin D may have effects on both active and passive calcium absorption. Aim: To identify mechanisms in vitro that may be responsible for the decreased calcium absorption after RYGB. We hypothesized that bile, alone or in concert with nutritional compounds, could be of importance. Material & methods: Caco-2 cells were grown confluent on semi-permeable membranes in a double-chamber setup to mimic small intestinal mucosa. The effect of bile acids chenodeoxycholic, lithocholic, glycocholic and taurocholic acid, with and without the addition of the fatty-acid butyrate, were tested for their effects on Hsp90β expression and active and passive calcium-flux monitored using radioactive 45 Ca. Results: We initially found that whole human bile, but only together with the fatty acid butyrate, potently induced Hsp90β expression. In line with this, a single bile acid, e.g. glycocholic acid (GCA), in combination with butyrate, increased Hsp90β expression (40 ± 13% vs. GCA, butyrate or vehicle alone; p < 0,001; n = 14-25). Further, this combination together with vitamin D increased the passive gradient-driven flux of calcium, compared to stimulation with vitamin D alone or in combination with either GCA or butyrate (880 ± 217% vs. vitamin D and GCA or butyrate, or vitamin D only; p = 0,01-0.006; n = 5-11). Surprisingly, this combination had no effect on active calcium transport in the absence of calcium gradient. Conclusion: The combination of GCA and butyrate increased gradient-driven calcium uptake up to 9-fold in Caco-2 intestinal epithelial cells, but had no effect on active calcium absorption. This effect was mediated via the vitamin D receptor co-activator Hsp90β.

Oxidative stress, antioxidants and intestinal calcium absorption

World Journal of Gastroenterology, 2017

The disequilibrium between the production of reactive oxygen (ROS) and nitrogen (RNS) species and their elimination by protective mechanisms leads to oxidative stress. Mitochondria are the main source of ROS as by-products of electron transport chain. Most of the time the intestine responds adequately against the oxidative stress, but with aging or under conditions that exacerbate the ROS and/or RNS production, the defenses are not enough and contribute to developing intestinal pathologies. The endogenous antioxidant defense system in gut includes glutathione (GSH) and GSH-dependent enzymes as major components. When the ROS and/or RNS production is exacerbated, oxidative stress occurs and the intestinal Ca 2+ absorption is inhibited. GSH depleting drugs such as DLbuthionine-S,R-sulfoximine, menadione and sodium deoxycholate inhibit the Ca 2+ transport from lumen to blood by alteration in the protein expression and/or activity of molecules involved in the Ca 2+ transcellular and paracellular pathways through mechanisms of oxidative stress, apoptosis and/or autophagy. Quercetin, melatonin, lithocholic and ursodeoxycholic acids block the effect of those drugs in experimental animals by their antioxidant, anti-apoptotic and/or anti-autophagic properties. Therefore, they may become drugs of choice for treatment of deteriorated intestinal Ca 2+ absorption under oxidant conditions such as aging, diabetes, gut inflammation and other intestinal disorders.

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

British Journal of Nutrition, 2012

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...

Lithocholic acid derivatives act as selective vitamin D receptor modulators without inducing hypercalcemia

Journal of Lipid Research, 2008

1a,25-Dihydroxyvitamin D 3 [1,25(OH) 2 D 3 ], a vitamin D receptor (VDR) ligand, regulates calcium homeostasis and also exhibits noncalcemic actions on immunity and cell differentiation. In addition to disorders of bone and calcium metabolism, VDR ligands are potential therapeutic agents in the treatment of immune disorders, microbial infections, and malignancies. Hypercalcemia, the major adverse effect of vitamin D 3 derivatives, limits their clinical application. The secondary bile acid lithocholic acid (LCA) is an additional physiological ligand for VDR, and its synthetic derivative, LCA acetate, is a potent VDR agonist. In this study, we found that an additional derivative, LCA propionate, is a more selective VDR activator than LCA acetate. LCA acetate and LCA propionate induced the expression of the calcium channel transient receptor potential vanilloid type 6 (TRPV6) as effectively as that of 1a,25-dihydroxyvitamin D 3 24-hydroxylase (CYP24A1), whereas 1,25(OH) 2 D 3 was more effective on TRPV6 than on CYP24A1 in intestinal cells. In vivo experiments showed that LCA acetate and LCA propionate effectively induced tissue VDR activation without causing hypercalcemia. These bile acid derivatives have the ability to function as selective VDR modulators.

Lithocholic acid attenuates cAMP-dependent Cl-secretion in human colonic epithelial T84 cells

American Journal of Physiology - Cell Physiology, 2016

Bile acids (BAs) play a complex role in colonic fluid secretion. We showed that dihydroxy BAs, but not the monohydroxy BA lithocholic acid (LCA), stimulate Cl− secretion in human colonic T84 cells (Ao M, Sarathy J, Domingue J, Alrefai WA, Rao MC. Am J Physiol Cell Physiol 305: C447–C456, 2013). In this study, we explored the effect of LCA on the action of other secretagogues in T84 cells. While LCA (50 μM, 15 min) drastically (>90%) inhibited FSK-stimulated short-circuit current ( Isc), it did not alter carbachol-stimulated Isc. LCA did not alter basal Isc, transepithelial resistance, cell viability, or cytotoxicity. LCA's inhibitory effect was dose dependent, acted faster from the apical membrane, rapid, and not immediately reversible. LCA also prevented the Isc stimulated by the cAMP-dependent secretagogues 8-bromo-cAMP, lubiprostone, or chenodeoxycholic acid (CDCA). The LCA inhibitory effect was BA specific, since CDCA, cholic acid, or taurodeoxycholic acid did not alter F...

Glutathione depleting drugs, antioxidants and intestinal calcium absorption

World Journal of Gastroenterology, 2018

Glutathione (GSH) is a tripeptide that constitutes one of the main intracellular reducing compounds. The normal content of GSH in the intestine is essential to optimize the intestinal Ca 2+ absorption. The use of GSH depleting drugs such as DL-buthionine-S,R-sulfoximine, menadione or vitamin K3, sodium deoxycholate or diets enriched in fructose, which induce several features of the metabolic syndrome, produce inhibition of the intestinal Ca 2+ absorption. The GSH depleting drugs switch the redox state towards an oxidant condition provoking oxidative/nitrosative stress and inflammation, which lead to apoptosis and/or autophagy of the enterocytes. Either the transcellular Ca 2+ transport or the paracellular Ca 2+ route are altered by GSH depleting drugs. The gene and/or protein expression of transporters involved in the transcellular Ca 2+ pathway are decreased. The flavonoids quercetin and naringin highly abrogate the inhibition of intestinal Ca 2+ absorption, not only by restoration of the GSH levels in the intestine but also by their anti-apoptotic properties. Ursodeoxycholic acid, melatonin and glutamine also block the inhibition of Ca 2+ transport caused by GSH depleting drugs. The use of any of these antioxidants to ameliorate the intestinal Ca 2+ absorption under oxidant conditions associated with different pathologies in humans requires more investigation with regards to the safety, pharmacokinetics and pharmacodynamics of them.

Regulation of intestinal calcium absorption by luminal calcium content: Role of intestinal alkaline phosphatase

Molecular Nutrition & Food Research, 2014

Intestinal alkaline phosphatase is a brush border enzyme that is stimulated by calcium. Inhibition of intestinal alkaline phosphatase increases intestinal calcium absorption. We hypothesized that intestinal alkaline phosphatase acts as a minute-to-minute regulatory mechanism of calcium entry. The aim of this study was to evaluate the mechanism by which intestinal luminal calcium controls intestinal calcium absorption. Methods and results: We performed kinetic studies with purified intestinal alkaline phosphatase and everted duodenal sacs and showed that intestinal alkaline phosphatase modifies the luminal pH as a function of enzyme concentration and calcium luminal content. A decrease in pH occurred simultaneously with a decrease in calcium absorption. The inhibition of intestinal alkaline phosphatase by L-phenylalanine caused an increase in calcium absorption. This effect was also confirmed in calcium uptake experiments with isolated duodenal cells. Conclusion: Changes in luminal pH arising from intestinal alkaline phosphatase activity induced by luminal calcium concentration modulate intestinal calcium absorption.

Bile acids inhibit Na+/H+ exchanger and Cl−/HCO3 − exchanger activities via cellular energy breakdown and Ca2+ overload in human colonic crypts

Pflügers Archiv - European Journal of Physiology, 2014

Bile acids play important physiological role in the solubilisation and absorption of dietary lipids. However, under pathophysiological conditions, such as short bowel syndrome, they can reach the colon in high concentrations inducing diarrhea. In this study our aim was to characterise the cellular pathomechanism of bile-induced diarrhea using human samples. Colonic crypts were isolated from biopsies of patients (controls with negative colonoscopic findings) and of cholecystectomised/ileumresected patients with or without diarrhoea. In vitro measurement of the transporter activities revealed impaired Na+/H+ exchanger (NHE) and Cl-/HCO3-exchanger (CBE) activities in cholecystectomised/ileum-resected patients suffering from diarrhea, compared to control patients. Acute treatment of colonic crypts with 0.3mM chenodeoxycholate caused dose-dependent intracellular acidosis; moreover, the activities of acid/base transporters (NHE and CBE) were strongly impaired. This concentration of chenodeoxycholate did not cause morphological changes in colonic epithelial cells, although significantly reduced the intracellular ATP level, decreased Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation mitochondrial transmembrane potential and caused sustained intracellular Ca2+ elevation. We also showed that chenodeoxycholate induced Ca2+ release from the endoplasmic reticulum and extracellular Ca2+ influx contributing to the Ca2+ elevation. Importantly, our results suggest that the chenodeoxycholate induced inhibition of NHE activities was ATP-dependent, whereas the inhibition of CBE activity was mediated by the sustained Ca2+ elevation. We suggest that bile acids inhibit the function of ion transporters via cellular energy breakdown and Ca2+ overload in human colonic epithelial cells, which can reduce fluid and electrolyte absorption in the colon and promote the development of diarrhea.

The secondary bile acids, ursodeoxycholic acid and lithocholic acid, protect against intestinal inflammation by inhibition of epithelial apoptosis

Physiological Reports, 2020

Increased epithelial permeability is a key feature of IBD pathogenesis and it has been proposed that agents which promote barrier function may be of therapeutic benefit. We have previously reported the secondary bile acid, ursodeoxycholic acid (UDCA), to be protective in a mouse model of colonic inflammation and that its bacterial metabolism is required for its beneficial effects. The current study aimed to compare the effects of UDCA, LCA, and a non-metabolizable analog of UDCA, 6-methyl-UDCA (6-MUDCA), on colonic barrier function and mucosal inflammation in a mouse model of colonic inflammation. Bile acids were administered daily to C57Bl6 mice by intraperitoneal injection. Colonic inflammation, induced by addition of DSS (2.5%) to the drinking water, was measured as disease activity index (DAI) and histological score. Epithelial permeability and apoptosis were assessed by measuring FITC-dextran uptake and caspase-3 cleavage, respectively. Cecal bile acids were measured by HPLC-MS/MS. UDCA and LCA, but not 6-MUDCA, were protective against DSS-induced increases in epithelial permeability and colonic inflammation. Furthermore, UDCA and LCA inhibited colonic epithelial caspase-3 cleavage both in DSS-treated mice and in an in vitro model of cytokine-induced epithelial injury. HPLC-MS/MS analysis revealed UDCA administration to increase colonic LCA levels, whereas LCA administration did not alter UDCA levels. UDCA, and its primary metabolite, LCA, protect against intestinal inflammation in vivo, at least in part, by inhibition of epithelial apoptosis and promotion of barrier function. These data suggest that clinical trials of UDCA in IBD patients are warranted.