Klotho : clinical aspects
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KLOTHO: CLINICAL ASPECTS Pr Dominique Prié, Université Paris Descartes, Faculté de Médecine, Institut Necker-Enfants Malades INSERM Service des Explorations Fonctionnelles Hôpital Necker-Enfants Malades, Paris, France THE DIFFERENT FORMS OF KLOTHO 1014 amino acids, short transmembrane and cytoplasmic segment Circulating Klotho FGF-23 FGF-23 KL1 KL2 FGFR membrane form of Klotho FRS2α Shedding (ADAMs 10, 17?) PLCγ ERK IP3 PKC AKT βcatenine Alternative splicing KL1? HOW KLOTHO COULD MODIFY CLINICAL PRACTICE? 1- Is Klotho important for the diagnosis? 2- Can Klotho be a biomarker? Can Klotho predict a risk? does this lead to a change of caring or treatment? • Variants in Klotho gene • mRNA expression in specific tissues • Protein expression in specific tissues • Protein level in blood 3- Is Klotho a surrogate or an independent biomarker? 4- Can Klotho be a therapeutic target? • Can over or down expression of Klotho improve the prognosis of a disorder or lower adverse outcomes? • How can we modify Klotho expression? EXPRESSION OF KLOTHO Kuro-o, Nature 1997, 390:45 KIDNEY: proximal + distal tubule Parathyroid gland Ben-Dov, JCI 2007; 117, 12: 4003 Hu Faseb J 2010 The tissue-specific expression of Klotho is controlled by the methylation of Klotho promoter (Azuma FASEB J. 2012) IS KLOTHO EXPRESSED IN THE ARTERY WALL? Healthy human (Lim Circulation. 2012;125:2243-2255) Specificity of the antibody? MICE Specific disruption of Klotho gene in smooth muscle cell of artery wall: No phenotype Lindberg (2013). PLoS ONE 8: e60658. Jimbo. Intern. J. Hypertension Volume 2014 DOES KLOTHO HAVE EFFECTS INDEPENDENT OF FGF23 ? FGF23 -/- = Klotho -/- = Double KO (Nakatani Faseb J 2009) Serum phosphate, tissue calcifications are similar Injection of Klotho in FGF23 -/- mice increases urinary phosphate excretion and lowers serum phosphate concentration (Hu Faseb J 2010) Klotho modifies channels and ion transporters activity in the absence of FGF23 (enzymatic effets?) Inhibe la voie WNT/β-catenine & IGF1 (liaison Klotho-β-catenine) FACTORS THAT MODIFY KLOTHO EXPRESSION Stimulating factors: • Calcitriol. • EPO: rat CKD model (Sugiura Am J Nephrol 2010;32:137) • Exercice Inhibiting factors: • FGF23 lowers Klotho mRNA expression in the kidney - FGF23 transgenic mice (Marsell, Nephrol. Dial. Transplant. 2008, 23: 827), - Hyp mice (Farrow. Journal of Endocrinology. 2010, 207: 67) no change of FGF23 signaling • Angiotensin II via AT1 (Yoon. Nephrol Dial Transplant 2011 26: 800) • TGFβ1 (Zhou. J Am Soc Nephrol 24: 771, 2013) • Methylation of Klotho promoter (renal insufficiency) RENAL EXPRESSION OF KLOTHO DURING CKD mRNA expression of the membrane form of Klotho in the kidney Protein expression in the kidney Patients on dialysis Koh BBRC 2001,280:1015 Sakan.2014. PLoS ONE 9(1): e86301. Akimoto et al. BMC Nephrology 2012, 13:155 PLASMA KLOTHO CONCENTRATION IN CKD Yamazaki BBRC 2010, 513 Scholze. 2014. J Clin Endocrinol Metab Pavik. Nephrol Dial Transplant (2012) Seiler. Kidney Intern 2012 KLOTHO AND SURVIVAL Klotho -/- in mice increases mortality Overexpression of Klotho in mice extends life span (Kurosu Science. 2005; 309: 1829) Specific renal Klotho deletion does not increase mortality nor alter growth (Olauson J Am Soc Nephrol 23:2012) KLOTHO AND SURVIVAL Variants in Klotho gene in healthy humans have been inconstantly associated with life expectancy. Association between survival and plasma Klotho concentration in 804 subjects > 65 ans follow up 6 years. independent predictor of all-cause mortality (Semba J Gerontol A Biol Sci Med Sci 2011) VARIANTS IN KLOTHO GENE, VITAMIN D, MORTALITY ON DIALYSIS Treatment VitD+ Treatment VitD- Friedman. 2009, J Bone Miner Res;24:1847 KLOTHO AND RENAL SURVIVAL Overexpression of Klotho slows down renal function degradation in various animal models of kidney disease. Very few data in human IgA nephropathy (Ko. Kidney Blood Press Res 2012;36:191) KLOTHO GENE VARIANTS AND CARDIOVASCULAR DISEASE Arking. Am. J. Hum. Genet. 72:1154, 2003 Rhee. Metabolism Clinical and Experimental 55 (2006) 1344 SIBS II = African-American Lack of association of Klotho gene variants with valvular and vascular calcification in Caucasians: a candidate gene study of the Framingham Offspring Cohort. Tangri. Nephrol Dial Transplant (2011) 26: 3998 CIRCULATING KLOTHO AND CARDIOVASCULAR DISEASE IN NON-CKD SUBJECTS Semba. J Am Geriatr Soc. 59:1596, 2011 Navarro-González. Heart 2014;100:34 CIRCULATING KLOTHO AND ATHEROSCLEROSIS Jeong AIDS RESEARCH AND HUMAN RETROVIRUSES Vol 29, 2013 CIRCULATING KLOTHO ARTERIAL COMPLIANCE, EXERCISE 69 healthy, postmenopausal women (50–76 years old) Matsubara. Am J Physiol Heart Circ Physiol 306: H348, 2014 CIRCULATING KLOTHO DEATH AND CARDIOVASCULAR EVENTS IN CKD STAGES 2-4 444 patients with CKD stages 2–4 atherosclerotic events/death decompensated heart failure/death Seiler. Clin J Am Soc Nephrol 9 2014 EFFECTS OF KLOTHO ON HEART Xie (2012). Nat Commun 3: 1238. CIRCULATING KLOTHO AND CARDIAC HYPERTROPHY 100 cardiology inpatients Shibata. 2013. PLoS ONE 8(9): e73184 KLOTHO AND CANCER • Increase in KL1 mRNA expression is associated with poor survival in ovarian cancer • Full length Klotho protein is expressed in normal breast, and its expression decreases in breast cancer • Klotho gene expression is decreased in various types of cancer (breast, gastric, colorectal, lung cancers, cervical carcinoma, pancreatic adenocarcinoma, hepatocellular carcinoma) due to methylation of Klotho promoter. It might hallmark cancer “aggressiveness” J. Usuda. Lung Cancer 74 (2011) 332 Small cell lung cancer J. Usuda. Lung Cancer.2010 large cell neuroendocrine carcinoma immunohistochemical expression of Klotho is cytoplasmic CONCLUSIONS 1- Klotho genomic variant analysis: contradictory results, no clinical application to date 2- Assessment of mRNA expression or Klotho promoter methylation in tumors: may be interesting in cancers to predict prognosis. The consequences on the treatment remain to be determined 3- Klotho protein expression in tissues: requires antibodies with unquestionable specificity. Interesting results to determine cancer prognosis 4- Measurement of circulating Klotho in blood and/or in urine: • need an improvement of the assay sensitivity in the lower concentrations • might be important to select patients with increased risks (death, vascular stiffness or calcification) independently of the renal function 5- Klotho as a therapeutic target: • Many encouraging data in animals but almost no data in human • ARA and calcitriol are already largely used as treatment in particular in CKD. Promote physical exercise. Future: injection of recombinant Klotho
