Vitamin D and proteinuria: a critical review of molecular bases and clinical experience.

Proteinuria is the main predictor of chronic kidney disease progression. Drugs that block the renin-angiotensin-aldosterone (RAA) system reduce proteinuria and slow down the progression of the disease. However, their effect is suboptimal, and residual proteinuria persists as an important predictor of renal impairment. Vitamin D has pleiotropic effects that could have an impact on these parameters. In this study, we critically review the molecular and experimental bases that suggest an antiproteinuric effect of vitamin D receptor (VDR) activation and the available evidence on its antiproteinuric effect in clinical practice. In animal models, we have observed the antiproteinuric effect of VDR activation, which could be due to direct protective action on the podocyte or other pleiotropic effects that slow down RAA system activation, inflammation and fibrosis. Clinical trials have generally been conducted in patients with a vitamin D deficiency or insufficiency and the main trial (VITAL) did not demonstrate that paricalcitol improved the study's primary endpoint (decrease in the urine albumin to creatinine ratio). In this sense, the information available is insufficient to advise the use of native vitamin D or VDR activators as renoprotective antiproteinuric drugs beyond the experimental level. Two Spanish clinical trials and one Italian trial attempted to determine the effect of paricalcitol and vitamin D on residual proteinuria in various clinical circumstances (PALIFE, NEFROVID and PROCEED).

Vitamina D y proteinuria: revisión crítica de las bases moleculares y de la experiencia clínica / Vitamin D and proteinuria: a critical review of molecular bases and clinical experience

La proteinuria es el principal predictor de progresión de la enfermedad renal crónica. Los fármacos que bloquean el eje renina-angiotensina-aldosterona (RAA) reducen la proteinuria y retrasan la progresión de la enfermedad. Sin embargo, su efecto es subóptimo, y la proteinuria residual persiste como predictor relevante de deterioro renal. La vitamina D tiene efectos pleiotrópicos que podrían impactar en estos parámetros. En este trabajo revisamos críticamente las bases moleculares y experimentales que sugieren un efecto antiproteinúrico de la activación del receptor de vitamina D (VDR), así como la evidencia disponible sobre su efecto antiproteinúrico en la práctica clínica. En modelos animales se ha observado un efecto antiproteinúrico de la activación del VDR, que podría deberse a una acción protectora directa sobre el podocito u otros efectos pleiotrópicos que frenen la activación del sistema RAA, la inflamación y la fibrosis. Los ensayos clínicos se han realizado en general en pacientes con déficit o insuficiencia de vitamina D y el mayor de ellos (VITAL) no demostró que el paricalcitol mejorara el objetivo primario del estudio (descenso del cociente albúmina creatinina urinario). En este sentido, la información disponible es insuficiente para aconsejar el empleo de la vitamina D nativa o de activadores del VDR como fármacos antiproteinúricos renoprotectores más allá del ámbito experimental. Dos ensayos clínicos españoles y uno italiano intentan aclarar cuál es el efecto del paricalcitol y la vitamina D sobre la proteinuria residual en diversas circunstancias clínicas (PALIFE, NEFROVID y PROCEED) (AU)

Proteinuria is the main predictor of chronic kidney disease progression. Drugs that block the renin-angiotensin-aldosterone system (ARBs) reduce proteinuria and slow down the progression of the disease. However, their effect is suboptimal, and residual proteinuria persists as an important predictor of renal impairment. Vitamin D has pleiotropic effects that could have an impact on these parameters. In this study, we critically review the molecular and experimental bases that suggest an antiproteinuric effect of vitamin D receptor (VDR) activation and the available evidence on its antiproteinuric effect in clinical practice. In animal models, we have observed the antiproteinuric effect of VDR activation, which could be due to direct protective action on the podocyte or other pleiotropic effects that slow down RAA system activation, inflammation and fibrosis. Clinical trials have generally been conducted in patients with a vitamin D deficiency or insufficiency and the main trial (VITAL) did not demonstrate that paricalcitol improved the study's primary endpoint (decrease in the urine albumin to creatinine ratio). In this sense, the information available is insufficient to advise the use of native vitamin D or VDR activators as renoprotective antiproteinuric drugs beyond the experimental level. Two Spanish clinical trials and one Italian trial attempted to determine the effect of paricalcitol and vitamin D on residual proteinuria in various clinical circumstances (PALIFE, NEFROVID and PROCEED) (AU)

Acute kidney injury transcriptomics unveils a relationship between inflammation and ageing

There are no pathophysiolgical therapeutic approaches to acute kidney injury (AKI) and the mortality remains high. In addition chronic kidney disease (CKD) predisposes to AKI and AKI contributes to progression of CKD. Recently a transcriptomics approach unveiled a relationship between AKI, inflammation and the regulation of ageing. A transcriptomics analysis of experimental AKI revealed increased kidney expression of Fn14 and transmembrane chemokine CXCL16, as well as a decreased expression of the kidney-secreted anti-ageing hormone Klotho. Fn14 is the receptor for tumor necrosis factor-like weak inducer of apoptosis (TWEAK), a member of the TNF superfamily. In AKI kidneys there was a positive correlation between Fn14 and CXCL16 mRNA expression and an inverse correlation between Fn14 and Klotho mRNA. Tubular cells were the site of Fn14, CXCL16 and Klotho expression in vivo. Research on the relationships between these three molecules disclosed that TWEAK activation of Fn14 promoted inflammation through secretion of chemokines such as CXL16 in tubular cells in culture and in vivo. Furthermore, TWEAK activation of Fn14 decreased expression of Klotho mRNA and protein in culture and in vivo. Interestingly, both TWEAK activation of CXCL16 mRNA transcription and suppression of Klotho mRNA transcription were mediated by the NFκB transcription factor. In conclusion, TWEAK engagement of Fn14 is a central event promoting NFκB-mediated activation of inflammation pathways and suppression of anti-inflammatory/anti-ageing pathways. This information may influence future therapeutic approaches to AKI and inflammation/aging (AU)

No existen estrategias terapéuticas y fisiopatológicas para el fracaso renal agudo (FRA), por lo que los niveles de mortalidad continúan siendo elevados. Además, la enfermedad renal crónica (ERC) predispone a sufrir FRA y el FRA, a su vez, contribuye a que la ERC avance. Recientemente, una estrategia transcriptómica reveló una relación entre el FRA, la inflamación y la regulación del envejecimiento. Un análisis transcriptómico de modelos experimentales de FRA reveló un aumento de la expresión renal de Fn14 y la quimiocina transmembrana CXCL16, así como un descenso en la expresión de la hormona Klotho antienvejecimiento secretada por el riñón. Fn14 es el receptor de la citoquina tumor necrosis factor-like weak inducer of apoptosis (TWEAK), miembro de la superfamilia de factor de necrosis tumoral. En los riñones con FRA, existía una correlación positiva entre Fn14 y la expresión de ARNm de CXCL16 y una correlación inversa entre Fn14 y el ARNm de Klotho. El lugar donde se da la expresión in vivo de Fn14, CXCL16 y Klotho es las células tubulares. La investigación en las relaciones entre estas tres moléculas reveló que la activación de Fn14 por TWEAK provocó la inflamación mediante la secreción de quimiocinas como la CXCL16 en células tubulares, tanto en cultivo como in vivo. Además, la activación de Fn14 por TWEAK disminuyó la expresión de ARNm de Klotho y de proteína, en cultivo y in vivo. Curiosamente, tanto la activación TWEAK de la trascripción de ARNm de CXCL16 y la supresión de la trascripción de ARNm de Klotho estuvieron mediadas por el factor de transcripción NF-κB. Como conclusión, la unión de TWEAK y Fn14 es un elemento clave en promover de la activación mediada por NF-kB de las vías de inflamación y en la supresión de las vías antiinflamatorias y antienvejecimiento. Esta información puede influir en las futuras estrategias terapéuticas para el FRA y la inflamación/envejecimiento (AU)

Acute kidney injury transcriptomics unveils a relationship between inflammation and ageing.

There are no pathophysiolgical therapeutic approaches to acute kidney injury (AKI) and the mortality remains high. In addition chronic kidney disease (CKD) predisposes to AKI and AKI contributes to progression of CKD. Recently a transcriptomics approach unveiled a relationship between AKI, inflammation and the regulation of ageing. A transcriptomics analysis of experimental AKI revealed increased kidney expression of Fn14 and transmembrane chemokine CXCL16, as well as a decreased expression of the kidney-secreted anti-ageing hormone Klotho. Fn14 is the receptor for tumor necrosis factor-like weak inducer of apoptosis (TWEAK), a member of the TNF superfamily. In AKI kidneys there was a positive correlation between Fn14 and CXCL16 mRNA expression and an inverse correlation between Fn14 and Klotho mRNA. Tubular cells were the site of Fn14, CXCL16 and Klotho expression in vivo. Research on the relationships between these three molecules disclosed that TWEAK activation of Fn14 promoted inflammation through secretion of chemokines such as CXL16 in tubular cells in culture and in vivo. Furthermore, TWEAK activation of Fn14 decreased expression of Klotho mRNA and protein in culture and in vivo. Interestingly, both TWEAK activation of CXCL16 mRNA transcription and suppression of Klotho mRNA transcription were mediated by the NFκB transcription factor. In conclusion, TWEAK engagement of Fn14 is a central event promoting NFκB-mediated activation of inflammation pathways and suppression of anti-inflammatory/anti-ageing pathways. This information may influence future therapeutic approaches to AKI and inflammation/aging.