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.

[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.

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)

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.

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.

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.

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+.

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.(AU)

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+.(AU)