Emerging concepts on the FGF23 regulation and activity.

Fibroblast growth factor 23 (FGF23) discovery has provided new insights into the regulation of Pi and Ca homeostasis. It is secreted by osteoblasts and osteocytes, and acts mainly in the kidney, parathyroid, heart, and bone. The aim of this review is to highlight the current knowledge on the factors modulating the synthesis of FGF23, the canonical and non-canonical signaling pathways of the hormone, the role of FGF23 in different pathophysiological conditions, and the anti-FGF23 therapy. This is a narrative review based on the search of PubMed database in the range of years 2000-2023 using the keywords local and systemic regulators of FGF23 synthesis, FGF23 receptors, canonical and non-canonical pathways, pathophysiological conditions and FGF23, and anti-FGF23 therapy, focusing the data on the molecular mechanisms. The regulation of FGF23 synthesis is complex and multifactorial. It is regulated by local factors and systemic regulators mainly involved in bone mineralization. The excessive FGF23 production is associated with different congenital diseases and with diseases occurring with a secondary high FGF23 production such as in chronic disease kidney and tumor-induced osteomalacia (TIO). The anti-FGF23 therapy appears to be useful to treat chromosome X-linked hypophosphatemia and TIO, but there are doubts about the handle of excessive FGF23 production in CKD. FGF23 biochemistry and pathophysiology are generating a plethora of knowledge to reduce FGF23 bioactivity at many levels that might be useful for future therapeutics of diseases associated with high-serum FGF23 levels.

The combined treatment of insulin and naringin improves bone properties in rats with type 1 diabetes mellitus.

We have studied the effects of individual and combined treatment of insulin (I) and naringin (NAR) on the bone structure and biomechanical properties of femurs from streptozotocin (STZ)-induced diabetic rats. Male Wistar rats were divided into five groups: (1) controls, (2) STZ-induced diabetic rats, (3) STZ-induced diabetic rats treated with I, (4) STZ-induced diabetic rats treated with NAR, and (5) STZ-induced diabetic rats treated with I + NAR. Bone mineral density (BMD), bone histomorphometry, biomechanical testing, and bone biomarker expressions were accomplished in femur of all animals, as well as serum biochemical analyses. The combined treatment of I + NAR increased the body weight and the femur BMD from STZ-induced diabetic rats. The bone biomechanical properties and the bone morphology of the femurs from STZ-induced diabetic rats were also improved by the combined treatment. The increased number of osteoclasts in STZ-induced diabetic rats was partially prevented by I, NAR, or I + NAR. NAR or I + NAR completely blocked the decrease in the number of osteocalcin (+) cells in the femur from STZ-induced diabetic rats. RUNX family transcription factor 2 immunostaining was much lower in STZ-induced diabetic rats than in control animals; the combination of I + NAR totally blocked this effect. The combined treatment not only ameliorated bone quality and function, but also normalized the variables related to glucose metabolism. Therefore, the combination of I + NAR might be a better therapeutic strategy than the individual I or NAR administration to reduce bone complications in diabetic patients.

[Melatonin reverses oxidative damage in the submandibular gland of rats treated with Cyclophosphamide]. / Melatonina revierte el daño oxidativo en glándula submandibular de ratas tratadas con Ciclofosfamida.

Objetive: Cyclophosphamide (Cf) produces oxidative damage in rat submandibular gland (GSM). In the present work we evaluated the antioxidant protective effect of melatonin (MLT) in GSM of rats treated with Cf. Methods: 40 adult male Wistar rats were divided into 5 groups (G): G1: control; G2: Control+Ethanol: treated with 1% ethanol for 10 consecutive days. On days 11 and 12 they received a dose of saline; G3: Cf: treated with 1% ethanol for 12 days, days 11 and 12 they received an intraperitoneal (i.p.) dose of Cf 50 mg/Kg/kg of saline. ) of Cf 50 mg/kg bw; G4: Cf + MLT: MLT (5 mg/kg bw, intraperitoneal, dissolved in 1% ethanol) was administered daily, days 11 and 12 received Cf same as G3; G5: MLT: treated 12 consecutive days with MLT (same dose as G4). After 12 hours of fasting, animals were anesthetized to obtain both submandibular glands, then they were sacrificed. Uric acid (UA), lipid peroxides (LPs), aqueous peroxides (APs) and superoxide dismutase (SOD) activity were measured in submandibular gland homogenate. Statistical analysis: we used ANOVA and Bonferroni test pos hoc, considering significant p<0.05. Results: Cf treatment decreased AU concentration and SOD activity (AU, mg/mg prot., G1: 2.50±0.68; G2: 2.18±0.13; G3: 0.54±0.09* G4: 1.95±0.24#, G5: 2.64±0.47, *p<0.01 G3 vs G1, G2, G4; #p<0.01 G4 vs G3 and G5; SOD, U/mg prot, G1: 4.57±0.95, G2: 4.79±0.94, G3: 2.18±0.53*, G4: 5.13±1.10, G5: 5.09±0.39, *p< 0.01 G3 vs G1, G2, G4 and G5). MLT treatment prevented these effects. In addition, Cf increased PL and PA formation. Conclusion: MLT improved the redox status in GSM of Cf-treated rats. MLT could prevent oxidative processes in GSM produced by Cf.

Objetivo: Ciclofosfamida (Cf) produce daño oxidativo en glándula submandibular (GSM) de ratas. En el presente trabajo se evaluó el efecto protector antioxidante de melatonina (MLT) en GSM de ratas tratadas con Cf. Método: Se utilizaron 40 ratas Wistar machos adultas divididas en 5 grupos (G): G1: control; G2: Control+Etanol: tratados con etanol al 1% durante 10 días consecutivos. Los días 11 y 12 recibieron una dosis de solución salina; G3: Cf: tratados con etanol al 1% durante 12 días, días 11 y 12 recibieron una dosis intraperitoneal (i.p.) de Cf de 50 mg/Kg de pc; G4: Cf + MLT: se administró diariamente MLT (5 mg/Kg pc, intraperitoneal, disuelta en etanol al 1%), días 11 y 12 recibieron Cf igual que G3; G5: MLT: tratamiento 12 días consecutivos con MLT (igual dosis de G4). Los animales fueron anestesiados, extirpándose ambas GSM y sacrificados, previo ayuno 12 hs. Se midió la concentración de ácido úrico (AU), peróxidos lipídicos (PL) y acuosos (PA) y actividad de superóxido dismutasa (SOD) en homogenato de GSM. Análisis estadístico: ANOVA y test de bonferroni, considerando significativo p<0,05. Resultados: El tratamiento con Cf disminuyó la concentración de AU y la actividad de SOD (AU, mg/mg prot., G1: 2,50±0,68; G2: 2,18±0,13; G3: 0,54±0,09* G4: 1,95±0,24#, G5: 2,64±0,47, *p< 0,01 G3 vs G1, G2, G4; #p< 0,01 G4 vs G3 y G5; SOD, U/mg prot., G1: 4,57±0.95, G2: 4,79±0,94, G3: 2,18±0,53*, G4: 5,13±1,10, G5: 5,09±0,39, *p< 0,01 G3 vs G1, G2, G4 y G5). El tratamiento con MLT previno esos efectos. Además, Cf aumentó la formación PL y PA. Conclusión: MLT mejoró el estado redox en GSM de ratas tratadas con Cf. MLT podría prevenir los procesos oxidativos en GSM producidos por Cf.

Pharmacoinformatics studies of coenzyme Q10 and potassium polyacrylate on angiotensin-converting enzyme associated with hypertension.

Coenzyme Q10's (CoQ10) favorable impact on cardiovascular diseases risk factors like hypertension and atherosclerosis is linked to the antioxidant action of CoQ10 in these conditions. This study showed the possible effects of CoQ10, potassium polyacrylate (PCK), and valsartan, a reference drug, on the angiotensin-converting enzyme (ACE), a crucial component of the renin-angiotensin system. The Glide tool on Maestro 11.1 was used to calculate the respective binding affinity and binding energy of these compounds towards ACE. The Schrödinger suite was used to run molecular dynamic simulations for 100 ns. The pkCSM tool was used to forecast the pharmacokinetic characteristics and toxicological effects. The SwissADME server was used to estimate the drug-like properties of these compounds. Based on their corresponding scoring values and the negative values of the binding free energies, molecular docking analysis of CoQ10 and PCK revealed that both exhibited favorable binding affinities towards the ACE, with CoQ10 having the highest binding scores. The results showed that both CoQ10 and PCK and the reference drug, valsartan, have some amino acids in common (at the pocket site of ACE) as the key residues for binding to ACE. Both CoQ10 and PCK demonstrated drug-like qualities and were not harmful, according to the predicted pharmacokinetics and toxicology studies. The results of this study suggest that because of its inhibitory interactions with ACE, CoQ10 in particular could be useful in regulating and reducing hypertension.Communicated by Ramaswamy H. Sarma.

Naringin prevents diabetic nephropathy in rats through blockage of oxidative stress and attenuation of the mitochondrial dysfunction.

We have studied the effects of naringin (NAR), a flavonoid from citric fruits, on morphology, ultrastructure and function of the kidney in streptozotocin (STZ)-induced diabetic rats. Two groups of animals were used: (1) control rats and (2) STZ rats (60 mg STZ/kg b.w.). At 3 days after induction, one group of STZ-treated rats received 40 mg NAR/kg b.w. daily. NAR blocked completely alterations in the biochemical renal markers in STZ rats except the increase in serum urea that was partially avoided by the flavonoid. NAR ameliorated the kidney morphological lesions from STZ rats. STZ treatment induced round and smaller mitochondria, which was avoided by NAR. Citrate synthase, isocitrate and malate dehydrogenases, enzyme activities of the Krebs cycle, were decreased in STZ rats. NAR abolished this decrease in the latter proteins. NAR also prevented a decrease in the ATP synthase activity of the mitochondria from renal cortex by about 49% in STZ rats, returning the enzyme activity to control values. The nephroprotection caused by NAR is mediated through counteraction of oxidative stress in mitochondria of proximal tubules. NAR might be a therapeutic strategy to reduce the complication of diabetic nephropathy in type 1 diabetic patients.

Naringin prevents bone damage in the experimental metabolic syndrome induced by a fructose-rich diet.

We analyzed the effect of naringin (NAR), a flavonoid from citric fruits, on bone quality and biomechanical properties, as well as the redox state of bone marrow in rats fed a fructose-rich diet (FRD), an experimental model to mimic human metabolic syndrome. NAR blocked the increase in the number of osteoclasts and adipocytes and the decrease in the number of osteocytes and osteocalcin (+) cells caused by FRD. Trabecular number was significantly higher in the FRD+NAR group. FRD induced a decrease in the femoral trabecular and cortical bone mineral density, which was blocked by NAR. The fracture and ultimate loads were also decreased in the FRD and FRD+NAR groups. NAR increased the number of nodes to terminal trabecula, the number of nodes to node trabecula, the number of nodes, and the number of nodes with 2 terminals and decreased the Dist (mean size of branches) value. FRD decreased bone marrow catalase activity, an effect that was prevented by NAR. In conclusion, FRD has detrimental effects on the long bones, which are associated with oxidative stress in the bone marrow. Most of these changes are prevented by NAR through its antioxidant properties and promotion of bone formation. Novelty: Fructose-rich diets have detrimental effects on long bones, which are associated with oxidative stress in the bone marrow. Most of these changes are prevented by naringin through its antioxidant properties and promotion of bone formation.

Analysis of the Molecular Mechanisms by Flavonoids with Potential Use for Osteoporosis Prevention or Therapy.

BACKGROUND: Osteoporosis is the most common skeletal disorder worldwide. Flavonoids have the potential to alleviate bone alterations in osteoporotic patients with the advantage of being safer and less expensive than conventional therapies. OBJECTIVE: The main objective is to analyze the molecular mechanisms triggered in bone by different subclasses of flavonoids. In addition, this review provides an up-to-date overview of the cellular and molecular aspects of osteoporotic bones versus healthy bones, and a brief description of some epidemiological studies indicating that flavonoids could be useful for osteoporosis treatment. METHODS: The PubMed database was searched in 2001- 2021 using the keywords osteoporosis, flavonoids, and their subclasses such as flavones, flavonols, flavanols, isoflavones, flavanones and anthocyanins, focusing the data on the molecular mechanisms triggered in bone. RESULTS: Although flavonoids comprise many compounds that differ in structure, their effects on bone loss in postmenopausal women or in ovariectomized-induced osteoporotic animals are quite similar. Most of them increase bone mineral density and bone strength, which occur through an enhancement of osteoblastogenesis and osteoclast apoptosis, a decrease in osteoclastogenesis, as well as an increase in neovascularization on the site of the osteoporotic fracture. CONCLUSION: Several molecules of signaling pathways are involved in the effect of flavonoids on osteoporotic bone. Whether all flavonoids have a common mechanism or they act as ligands of estrogen receptors remains to be established. More clinical trials are necessary to know better their safety, efficacy, delivery and bioavailability in humans, as well as comparative studies with conventional therapies.

Interacción del microbioma intestinal y el hueso / Interaction between the intestinal microbiome and bone

El "microbioma" no solo está constituido por los microbios, sino por todos los componen-tes que viven en el mismo hábitat conforman-do un nicho ecológico. Es decir, está conformado por los microorganismos (bacterias, hongos, protozoos, etc.), todo el espectro de moléculas producidas por ellos tales como sus componentes estructurales (ácidos nucleicos, proteínas, lípidos y glúcidos), meta-bolitos, toxinas, etc., y las moléculas producidas por el huésped. El microbioma intestinal (MI) ha emergido como un factor que tiene un gran efecto sobre la cantidad, calidad y fuerza del hueso. Las investigaciones revelan que la homeostasis ósea está ligada al micro-bioma saludable, mientras que la disbiosis (alteración en la biodiversidad microbiana) puede exacerbar la actividad osteoclástica y promover la osteoporosis. Los mecanismos potenciales involucrados en la interacción del microbioma intestinal y el hueso son la influencia del metabolismo del huésped, el mantenimiento de la integridad intestinal y regulación de la absorción de nutrientes, la regulación del eje intestino-sistema inmune y la modulación del sistema endocrino. Es decir que hay múltiples vías por las cuales el MI influye sobre el hueso, pero estos y otros mecanismos deben profundizarse más aún. También es necesario que se identifiquen y caractericen mejor los microorganismos que están asociados a las enfermedades óseas. El conocimiento de estos aspectos podría ser útil para el desarrollo de herramientas terapéuticas basadas en el MI que puedan mejorar la eficacia de los distintos tratamientos existentes. (AU)

The microbiome is not only constituted by microbes, but by all the components that live in the same habitat forming an ecological niche. It is conformed by the microorganisms ( bacteria, fungi, protozoa, etc), the entire spectrum of molecules produced by them (nucleic acids, proteins, lipid and carbohydrates, metabolites, toxins, etc) and the molecules produced by the host. The intestinal microbiome (IM) has emerged as a factor with great effects on the quantity, quality and strength of bone. The investigations reveal that bone homeostasis is linked to the healthy microbiome, while the dysbiosis (alteration in the microbial biodiversity) can exacerbate the osteoclastic activity and promote osteoporosis. The potential mechanisms involved in the interaction between IM and bone are the influence of the host metabolism, the maintenance of the intestinal integrity and regulation of the nutrient absorption, the regulation of the intestine/ immune system axis and the modulation of the endocrine system. That is, there are multiple ways through which IM influences on bone, but these and other mechanisms need to be further studied. It is also necessary to identify and characterize the microorganisms associated with the bone diseases. Knowledge of these aspects could be useful to develop therapeutical tools based on the IM that could improve the efficacy of the current treatments. (AU)

New Perspectives in the Pharmacological Potential of Naringin in Medicine.

BACKGROUND: Naringin (NAR) is a flavonoid enriched in several medicinal plants and fruits. An increasing interest in this molecule has emerged because it has the potential to contribute to alleviating many health problems. OBJECTIVE: This review briefly describes the NAR pharmacokinetics and it mainly focuses on the in vitro and in vivo animal studies showing NAR beneficial effects on cardiovascular, metabolic, neurological and pulmonary disorders and cancer. The anabolic effects of NAR on different models of bone and dental diseases are also analyzed. In addition, the evidence of the NAR action on the gastrointestinal tract is reported as well as its influence on the microbiota composition and activity. Finally, current research on NAR formulations and clinical applications are discussed. METHODS: The PubMed database was searched until 2019, using the keywords NAR, naringenin, cardiovascular and metabolic disorders, neurological and pulmonary disorders, cancer, bone and dental diseases, gastrointestinal tract, microbiota, NAR formulations, clinical trials. RESULTS: The number of studies related to the bioavailability and pharmacokinetics of NAR is limited. Positive effects of NAR have been reported on cardiovascular diseases, Type 2 Diabetes Mellitus (T2DM), metabolic syndrome, pulmonary disorders, neurodegenerative diseases, cancer, and gastrointestinal pathologies. The current NAR formulations seem to improve its bioavailability, which would allow its clinical applications. CONCLUSION: NAR is endowed with broad biological effects that could improve human health. Since a scarce number of clinical studies have been performed, the NAR use requires more investigation in order to know better their safety, efficacy, delivery, and bioavailability in humans.

Role of mitochondria in the differential action of sodium deoxycholate and ursodeoxycholic acid on rat duodenum.

Sodium deoxycholate (NaDOC) inhibits the intestinal Ca2+ absorption and ursodeoxycholic acid (UDCA) stimulates it. The aim of this study was to determine whether NaDOC and UDCA produce differential effects on the redox state of duodenal mitochondria altering the Krebs cycle and the electron transport chain (ETC) functioning, which could lead to perturbations in the mitochondrial dynamics and biogenesis. Rat intestinal mitochondria were isolated from untreated and treated animals with either NaDOC, UDCA, or both. Krebs cycle enzymes, ETC components, ATP synthase, and mitochondrial dynamics and biogenesis markers were determined. NaDOC decreased isocitrate dehydrogenase (ICDH) and malate dehydrogenase activities affecting the ETC and ATP synthesis. NaDOC also induced oxidative stress and increased the superoxide dismutase activity and impaired the mitochondrial biogenesis and functionality. UDCA increased the activities of ICDH and complex II of ETC. The combination of both bile acids conserved the functional activities of Krebs cycle enzymes, ETC components, oxidative phosphorylation, and mitochondrial biogenesis. In conclusion, the inhibitory effect of NaDOC on intestinal Ca2+ absorption is mediated by mitochondrial dysfunction, which is avoided by UDCA. The stimulatory effect of UDCA alone is associated with amelioration of mitochondrial functioning. This knowledge could improve treatment of diseases that affect the intestinal Ca2+ absorption.

Glutathione depleting drugs, antioxidants and intestinal calcium absorption.

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 Ca2+ 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 Ca2+ 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 Ca2+ transport or the paracellular Ca2+ route are altered by GSH depleting drugs. The gene and/or protein expression of transporters involved in the transcellular Ca2+ pathway are decreased. The flavonoids quercetin and naringin highly abrogate the inhibition of intestinal Ca2+ 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 Ca2+ transport caused by GSH depleting drugs. The use of any of these antioxidants to ameliorate the intestinal Ca2+ absorption under oxidant conditions associated with different pathologies in humans requires more investigation with regards to the safety, pharmacokinetics and pharmacodynamics of them.

Molecular Mechanisms Triggered by Bile Acids on Intestinal Ca2+ Absorption.

BACKGROUND: Bile acids (BAs) are among the main components of bile. Lately, they are also considered important signaling molecules, not only by regulating their own synthesis, but also having a role in several metabolic diseases. OBJECTIVE: In this review we focus on the effect of sodium deoxycholate (NaDOC), ursodeoxycholic (UDCA) and litocholic (LCA) acids and their combination upon the intestinal Ca2+ absorption. To make clear the actions of those BAs on this physiological process, an overview of current information about the mechanisms by which the intestinal Ca2+ occurs is described. METHODS: The PubMed database was searched until 2017, using the keywords bile acids, NaDOC, UDCA and LCA and redox state, apoptosis, autophagy and intestinal Ca2+ absorption. RESULTS: The modulation of redox state, apoptosis and autophagy are mechanisms that are involved in the action of BAs on intestinal Ca2+ absorption. Although the mechanisms are still not completely understood, we provide the latest knowledge regarding the effect of BAs on intestinal Ca2+ absorption. CONCLUSION: The response of the intestine to absorb Ca2+ is affected by BAs, but it is different according to the type and dose of BA. When there is a single administration, NaDOC has an inhibitory effect, UDCA is an stimulator whereas LCA does not have any influence. However, the combination of BAs modifies the response. Either UDCA or LCA protects the intestine against the oxidative injury caused by NaDOC by blocking the oxidative/nitrosative stress, apoptosis and autophagy.

Lithocholic acid: a new emergent protector of intestinal calcium absorption under oxidant conditions.

LCA and 1,25(OH)2D3 are vitamin D receptor ligands with different binding affinity. The secosteroid stimulates intestinal Ca2+ absorption. Whether LCA alters this process remains unknown. The aim of our work was to determine the effect of LCA on intestinal Ca2+ absorption in the absence or presence of NaDOC, bile acid that inhibits the cation transport. The data show that LCA by itself did not alter intestinal Ca2+ absorption, but prevented the inhibitory effect of NaDOC. The concomitant administration of LCA avoided the reduction of intestinal alkaline phosphatase activity caused by NaDOC. In addition, LCA blocked a decrease caused by NaDOC on gene and protein expression of molecules involved in the transcellular pathway of intestinal Ca2+ absorption. The oxidative stress and apoptosis triggered by NaDOC were abrogated by LCA co-treatment. In conclusion, LCA placed in the intestinal lumen protects intestinal Ca2+ absorption against the inhibitory effects caused by NaDOC. LCA avoids the reduction of the transcellular Ca2+ movement, apparently by blocking the oxidative stress and apoptosis triggered by NaDOC, normalizing the gene and protein expression of molecules involved in Ca2+ movement. Therefore, LCA might become a possible treatment to improve intestinal calcium absorption under oxidant conditions.

Ursodeoxycholic and deoxycholic acids: Differential effects on intestinal Ca(2+) uptake, apoptosis and autophagy of rat intestine.

The aim of this work was to study the effect of sodium deoxycholate (NaDOC) and ursodeoxycholic acid (UDCA) on Ca(2+) uptake by enterocytes and the underlying mechanisms. Rats were divided into four groups: a) controls, b) treated with NaDOC, c) treated with UDCA d) treated with NaDOC and UDCA. Ca(2+) uptake was studied in enterocytes with different degrees of maturation. Apoptosis, autophagy and NO content and iNOS protein expression were evaluated. NaDOC decreased and UDCA increased Ca(2+) uptake only in mature enterocytes. The enhancement of protein expression of Fas, FasL, caspase-8 and caspase-3 activity by NaDOC indicates triggering of the apoptotic extrinsic pathway, which was blocked by UDCA. NO content and iNOS protein expression were enhanced by NaDOC, and avoided by UDCA. The increment of acidic vesicular organelles and LC3 II produced by NaDOC was also prevented by UDCA. In conclusion, the inhibitory effects of NaDOC on intestinal Ca(2+) absorption occur by decreasing the Ca(2+) uptake by mature enterocytes. NaDOC triggers apoptosis and autophagy, in part as a result of nitrosative stress. In contrast, UDCA increases the Ca(2+) uptake by mature enterocytes, and in combination with NaDOC acts as an antiapoptotic and antiautophagic agent normalizing the transcellular Ca(2+) pathway.

La diabetes mellitus experimental produce aumento en la expresión de iNOS y altera la vía paracelular de la absorción intestinal de calcio / Experimental diabetes mellitus produces increased iNOS expression and alters the paracellular pathway of intestinal calcium absorption

Previamente hemos demostrado que la diabetes mellitus tipo 1 experimental (D.m.1) inducida por estreptozotocina (STZ) produce estrés oxidativo intestinal en las primeras etapas de la enfermedad, lo que conduce a la inhibición de la absorción intestinal de Ca+2, alterando la vía transcelular del transporte del catión. El objetivo de este trabajo fue estudiar la vía paracelular del transporte del Ca+2 y analizar si la D.m.1 induce estrés nitrosativo a nivel duodenal. Se utilizaron ratas Wistar machos a las que se inyectaron 60 mg STZ/kg de peso corporal; se sacrificaron a los 30 días postratamiento. Se determinó la expresión génica y proteica de claudina 2 y 12, proteínas involucradas en el transporte paracelular del Ca+2. En la mucosa duodenal se determinó el contenido de óxido nítrico (NO) y la expresión proteica de óxido nítrico sintasa inducible (iNOS). Los resultados revelaron que la expresión génica de claudina 2 en las ratas diabéticas fue más del doble en comparación con la de los controles, mientras que la expresión génica de claudina 12 fue similar en ambos grupos. La expresión proteica de claudina 2 y 12 aumentó en las ratas diabéticas. El contenido de NO fue similar en ambos grupos; sin embargo, la expresión proteica de iNOS fue mayor en las ratas diabéticas en comparación con la de las ratas controles. En conclusión, la D.m.1 experimental se acompaña de estrés oxidativo y de aumento en la expresión proteica de iNOS, alterándose la vía paracelular de absorción de Ca+2 como un mecanismo compensatorio. (AU)

We have previously shown that experimental type 1 diabetes mellitus (D.m.1) produced by streptozotocin (STZ) in rats causes intestinal oxidative stress in the early stages of the disease, which leads to the inhibition of intestinal Ca2+ absorption, altering the transcellular Ca2+ pathway. The aim of this work was to study the paracellular Ca2+ pathway and analyze if D.m.1 induces duodenal nitrosative stress. The animals were assigned to two groups: 1) control rats, and 2) STZ-induced diabetic rats (60 mg/kg b.w.). Rats were sacrificed 30 days after induction of diabetes. The gene and protein expression of claudin 2 and 12, proteins involved in paracellular Ca2+ pathway, was determined as well as the nitric oxide (NO) content and protein expression of iNOS in rat duodenum mucosa. The results revealed that claudin 2 expression was more that double in diabetic rats compared to control rats at 30 days, while the gene expression of claudin 12 was similar in both groups. The protein expression of claudin 2 and 12 increased in the diabetic rats. NO content was similar in both groups, but the iNOS protein expression was enhanced in diabetic rats. To conclude, the experimental type I D.m.1 is accompanied by duodenal oxidative stress, increase iNOS protein expression and alteration of the paracellular Ca2+ pathway as a compensatory mechanism. (AU)

Dietary and pharmacological compounds altering intestinal calcium absorption in humans and animals.

The intestine is the only gate for the entry of Ca to the body in humans and mammals. The entrance of Ca occurs via paracellular and intracellular pathways. All steps of the latter pathway are regulated by calcitriol and by other hormones. Dietary and pharmacological compounds also modulate the intestinal Ca absorption process. Among them, dietary Ca and P are known to alter the lipid and protein composition of the brush-border and basolateral membranes and, consequently, Ca transport. Ca intakes are below the requirements recommended by health professionals in most countries, triggering important health problems. Chronic low Ca intake has been related to illness conditions such as osteoporosis, hypertension, renal lithiasis and incidences of human cancer. Carbohydrates, mainly lactose, and prebiotics have been described as positive modulators of intestinal Ca absorption. Apparently, high meat proteins increase intestinal Ca absorption while the effect of dietary lipids remains unclear. Pharmacological compounds such as menadione, dl-butionine-S,R-sulfoximine and ursodeoxycholic acid also modify intestinal Ca absorption as a consequence of altering the redox state of the epithelial cells. The paracellular pathway of intestinal Ca absorption is poorly known and is under present study in some laboratories. Another field that needs to be explored more intensively is the influence of the gene × diet interaction on intestinal Ca absorption. Health professionals should be aware of this knowledge in order to develop nutritional or medical strategies to stimulate the efficiency of intestinal Ca absorption and to prevent diseases.

Time dependent changes in the intestinal Ca²âº absorption in rats with type I diabetes mellitus are associated with alterations in the intestinal redox state.

The aim was to determine the intestinal Ca²âº absorption in type I diabetic rats after different times of STZ induction, as well as the gene and protein expression of molecules involved in both the transcellular and paracellular Ca²âº pathways. The redox state and the antioxidant enzymes of the enterocytes were also evaluated in duodenum from either diabetic or insulin-treated diabetic rats as compared to control rats. Male Wistar rats (150-200 g) were divided into two groups: 1) controls and 2) STZ-induced diabetic rats (60 mg/kg b.w.). A group of diabetic rats received insulin for five days. The insulin was adjusted daily to maintain a normal blood glucose level. Five 5 d after STZ injection, there was a reduction in the intestinal Ca²âº absorption, which was maintained for 30 d and disappeared at 60 d. Similar changes occurred in the GSH and (˙)O(2)(-) levels. The protein expression of molecules involved in the transcellular pathway increased at 5 and 30 d returning to control values at 60 d. Their mRNA levels declined considerably at 60 d. The gene and protein expression of claudin 2 was upregulated at 30 d. Catalase activity increased at 5 and 30 d normalizing at 60 d. To conclude, type I D.m. inhibits the intestinal Ca²âº absorption, which is transient leading to a time dependent adaptation and returning the absorptive process to normal values. The inhibition is accompanied by oxidative stress. When insulin is administered, the duodenal redox state returns to control values and the intestinal Ca²âº absorption normalizes.

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

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 cation absorption through triggering oxidative stress. The use of UDCA in patients with cholestasis would be benefited because of the protective effect on the intestinal Ca(2+) absorption, avoiding the inhibition caused by hydrophobic bile acids and neutralizing the oxidative stress.

Sodium deoxycholate inhibits chick duodenal calcium absorption through oxidative stress and apoptosis.

High concentrations of sodium deoxycholate (NaDOC) produce toxic effects. This study explores the effect of a single high concentration of NaDOC on the intestinal Ca(2+) absorption and the underlying mechanisms. Chicks were divided into two groups: 1) controls and 2) treated with different concentrations of NaDOC in the duodenal loop for variable times. Intestinal Ca(2+) absorption was measured as well as the gene and protein expressions of molecules involved in the Ca(2+) transcellular pathway. NaDOC inhibited the intestinal Ca(2+) absorption, which was concentration dependent. Ca(2+)-ATPase mRNA decreased by the bile salt and the same occurred with the protein expression of Ca(2+)-ATPase, calbindin D(28k) and Na(+)/Ca(2+) exchanger. NaDOC produced oxidative stress as judged by ROS generation, mitochondrial swelling and glutathione depletion. Furthermore, the antioxidant quercetin blocked the inhibitory effect of NaDOC on the intestinal Ca(2+) absorption. Apoptosis was also triggered by the bile salt, as indicated by the TUNEL staining and the cytochrome c release from the mitochondria. As a compensatory mechanism, enzyme activities of the antioxidant system were all increased. In conclusion, a single high concentration of NaDOC inhibits intestinal Ca(2+) absorption through downregulation of proteins involved in the transcellular pathway, as a consequence of oxidative stress and mitochondria mediated apoptosis.

Mecanismos moleculares desencadenados por el deoxicolato de sodio en intestino: implicancias en la absorción intestinal de calcio / Molecular mechanisms triggered by sodium deoxycholate in intestine: implications in intestinal calcium absorption

Altas concentraciones de deoxicolato de sodio (DXCS) producen efectos tóxicos en el intestino. Este estudio explora el efecto de concentraciones fisiológicas altas de DXCS sobre la absorción intestinal de Ca2+ y los mecanismos moleculares involucrados. Para ello, se usaron pollos de 4 semanas de edad, los cuales se dividieron en dos grupos: controles y tratados con DXCS en la luz intestinal, a diferentes tiempos y concentraciones. La absorción intestinal de Ca2+ se midió por la técnica del asa intestinal ligada in situ. Se estudió la expresión de genes y de proteínas involucradas en la vía transcelular de la absorción del catión. El contenido de glutatión (GSH) y la actividad de enzimas del sistema antioxidante se evaluaron por espectrofotometría. La producción de ROS se determinó por espectrometría de resonancia de espín y los cambios en la permeabilidad de la membrana interna itocondrial mediante la técnica de swelling. La apoptosis se estudió a través de la localización subcelular de citocromo c por Western blot y la fragmentación del ADN por la técnica de TUNEL. DXCS inhibió la absorción intestinal de Ca+2, efecto que fue dependiente de la concentración de la sal biliar. La expresión del ARNm de la Ca+2- ATPasa disminuyó por el tratamiento con la sal biliar y lo mismo ocurrió con la expresión de las proteínas involucradas en el proceso de absorción del catión: Ca+2- ATPasa, intercambiador Na+/Ca+2 y calbindina D28k. DXCS produjo estrés oxidativo, a juzgar por la generación de ROS, la depleción de glutatión y el swelling mitocondrial. Además, la presencia del antioxidante quercetina en el medio de incubación bloqueó el efecto inhibitorio del DXCS sobre la absorción intestinal de Ca+2.

SUMMARY: High concentrations of sodium deoxycholate (NaDOC) produce toxic effects. This study explores the effect of a single high concentration of NaDOC on the intestinal Ca2+ absorption and the underlying mechanisms. Chicks were divided into two groups: 1) controls, 2) treated with different concentrations of NaDOC in the duodenal loop for variable times. Intestinal Ca2+ absorption was measured as well as the gene and protein expression of molecules involved in the Ca2+ transcellular pathway. Glutathione (GSH) content and the activity of antioxidant enzymes were assessed by spectrophotometry. ROS was determined by spin resonance spectrometry and permeability changes of the internal mitochondrial membrane by the swelling technique. Apoptosis was studied by cytochrome localization through Western blot and DNA fragmentation (TUNEL procedure). NaDOC inhibited the intestinal Ca2+ absorption, which was dose dependent. Ca2+- ATPase mRNA decreased by the ile salt and the same occurred with the protein expression of Ca2+-ATPase, calbindin D28k and Na+/Ca2+ exchanger. NaDOC produced oxidative stress as judged by ROS generation, mitochondrial swelling and glutathione depletion. Furthermore, the antioxidant quercetin blocked the inhibitory effect of NaDOC on the intestinal Ca2+ bsorption. Apoptosis was also triggered by the bile salt, as indicated by the TUNEL staining and the cytochrome crelease from the mitochondria. As a compensatory mechanism, enzyme activities of the antioxidant system were all increased, but the cellular redox state was not normalized. In conclusion, a single high dose of NaDOC inhibits intestinal Ca2+.