FGF23 (and Klotho): what’s new? Brief introduction to...
Transcript of FGF23 (and Klotho): what’s new? Brief introduction to...
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FGF23 (and Klotho): what’s new?
Justine Bacchetta, MD, PhD
Reference Center for Rare Renal Diseases
Long Beach, CA, 2017
Brief introduction to FGF23
1-25 vitamin D
FGF23 PTH
Phosphorus Calcium
Stimulating effect / Inhibiting effect
Calcium and phosphate metabolism
Bacchetta, EMC 2015
Introduction to FGF23
• FGF23 synthezised by osteocytes
• FGF-R: tyrosine kinase receptor– FGFR-1/2/3/4
• Klotho: cofactor– Anti-aging protein– Tissue-specific expression – Kidney and parathyroid gland
Unakawa, Nature 2006; Bonewald JBMR 2010
FGF23: phosphorylation pathways
• Klotho-dependent and Klotho-independent activation of the
phosphorylation pathways
• Erk 1/2 and Akt pathway
• Calcineurin-NFAT pathway
Faul, JCI 2011
FGF23: phosphorylation pathways
• Klotho-dependent and Klotho-independent activation of the
phosphorylation pathways
• Erk 1/2 and Akt pathway
• Calcineurin-NFAT pathway
Faul, JCI 2011
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Proximal tubule Parathyroid
PTH inhibition
1α hydroxylase
stimulation
Hypophosphatemia, PTH and 1-25 OH2 vitamin D inhibition
FGF23: 3 main ‘historical’ actions
Prie, Kidney Int 2009
Npt inhibition 2a-2c
1α hydroxylase inhibition
24 hydroxylase stimulation
FGF23
Saito, J Biol Chem 2003
Andrukhova, EMBO 2014
Kidney
Silver, PN 2010
Olauson Plos One 2013
Parathyroid
Bacchetta, JBMR 2012
Chonchol, JASN 2015 & JASN 2016
Immune system
Cartilage
Kawai, JBC 2012 Dentoalveolar complex
Chu, Anat Rec 2010
FGF23: an endocrine FGF with off-target effects
Bone
Wang JBMR 2008, Wesseling-Perry JCEM
2009, Allard CTI 2015
Faul, JCI 2011
Heart &
Cardiomyocytes
Hippocampal cells
and CNS
Hensel, J Neurochem 2016
Other targets?
New insights: FGF23 physiology in bone
FGF23 as an inhibitor of bone mineralization
• Model of genetic hyperphosphatemia (GALNT 3 mutation)
• Low intact FGF23 levels
• High C-terminal FGF23 levels
• Familial tumoral calcinosis
Masi CTI 2015
FGF23 as an inhibitor of bone mineralization
• Comparison of mineralization in vitro in preosteoblastic cells from a patient with
GALNT3 mutation (low intact FGF23 levels) and from controls
• Higher capability to form mineralization
Masi CTI 2015
Patient
LOW
FGF23
Control
NORMAL
FGF23
Biphasic effects of FGF23 on osteoclast biology
Allard, Calcified Tissue International 2015
Inhibition of osteoclast
differentiation
An expression of FGF-R1
An activation of Erk and Akt
Effects driven through FGF-R
A moderate albeit significant
stimulation of resorption
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Klotho expression in long bones regulates FGF23 production
during renal failure
Kaludjerovic FASEB 2017
• Murine model: targeted deletion of Klotho
in long bones
• Two main results
• Long bones from these mice did not
increase FGF23 expression after adenine
diet or 5/6th nephrectomy
• FGF23-treated bone cells required Klotho
to increase FGF23 expression and induce
Erk phosphorylation
New insights: FGF23 physiology in the
central nervous system
Impact of FGF23 on neuronal morphology and synaptic density
• In vitro model of primary murine hippocampal cultures
• Incubation with FGF23 ± α-Klotho
• Enhanced number of primary neurites
• And reduced arborization
=> Resulting in a less complex neuronal morphology
Hensel J Neurochemist 2016
New insights: FGF23 and adipose tissue
And the fat lady sings about phosphate and calcium…
Wagner Kidney International 2017
Towards new endocrine regulations…
Rutkowski, Kidney International 2017; editorial comment by Wagner Kidney International 2017
• High adiponectin levels
• Suppressed Klotho renal
expression
• Decreased FGF23 levels
• Caused renal loss of
calcium
New insights: FGF23 and (pediatric) CKD
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Faul et al, J Clin Invest 2011
Gutierrez et al, N Eng J Med 2008
Fliser, JASN 2007; Isakova JAMA 2011
Wolf, Kidney International 2012 Pereira, Bone 2010
The paradigm: both FGF23 and Klotho are deregulated early
in CKD
Bacchetta, J Clin Endocrinol Metab 2010
FGF23 in pediatric CKD
Cohort of 227 followed in a pediatric
nephrology unit
Normal renal function and CKD (pre-dialysis)
GFR: inulin clearance
Influence of GFR, age, solid organ
transplantation and BMI on FGF23 levels
A likely influence of corticosteroids on FGF23
loevels
An association between FGF23 and uric acid
An association between FGF23 and IGF1
Bacchetta, Pediatr Nephrol 2012
• Similar results of an open label prospective study in Pediatric Endocrinology,
Birmingham, Alabama
– 23 children with GH deficiency
– Clinical trial: C terminal FGF23 before and one year after rhGH
– Increased FGF23, TmP/GFR and phosphorus after rhGH
– The increase of FGF23 remained significant after adjustment on age and phosphorus
Gardner et al, J Pediatr Endocrinol Metab 2011
Recombinant growth hormone increases FGF23 levels
Portale, clin J Am Soc Nephrol 2014
FGF23 increases early in pediatric CKD
Data from the CKID cohort
N=464 children ages 1–16 years with predialysis CKD
Portale, clin J Am Soc Nephrol 2016
FGF23 as a risk factor of CKD progression
Data from the CKID cohort
N=419 children ages 1–16 years with predialysis CKD
New insights: FGF23 and infections in CKD
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FGF23 as an inhibitor of extra-renal 1-alpha hydroxylase in
monocytes
Bacchetta, JBMR 2012
Vehicle
IL-15
1,2
5(O
H) 2
D1
,25
(OH
) 2D
1,2
5(O
H) 2
D
25OHD
25OHD
25OHD
1,25(OH)2D
1,25(OH)2D
IL-15+
FGF23
1,25(OH)2D
*
0.00
0.20
0.40
0.60
0.80
1.00
1.20
CYP27B1 CYP24A1 VDR LL37 TNF
Fold
change in m
RN
A r
ela
tive t
o v
ehic
le-t
reate
d c
ells
** ***
FGF23: 100 ng/mL, 24 hours
Controls = PBS
6 hours = black
24 hours = grey
Data obtained in monocytes from healthy donors, but similar data obtained in PD cells from pediatric patients undergoing
chronic PD
High FGF23 (and low 25-D) as risk factors for clinical
infections in the HEMO-study
Chonchol, JASN 2015 and further confirmed JASN 2016
New insights: FGF23 and cardiovascular
disease in CKD
FGF23 and left ventricular hypertrophy
• Increased FGF 23 levels and left
ventricular hypertrophy
– Epidemiological prospective
– CRIC cohort, 3070 CKD adults
Faul et al, J Clin Invest 2011
• Increased FGF 23 levels at baseline
and increased risk for onset of LVH
– RR= 2.4
• Rat cardiomyocytes + FGF23
– Hypertrophy, dose-dependent
– Reactivation fetal genes
– Increased markers for LVH
FGF23 and cardiomyocytes: a Klotho-independent effect
Faul et al, J Clin Invest 2011
• Klotho is not expressed in CM, but FGF-R1 and 4 are
• Signaling pathways
– Through FGF-R signaling
– Through PLCγ and NFAT
– No activation of Akt
• Intramyocardial and intravenous injection of
FGF23 induces ventricular hypertrophy in mice
– Wild type
– Klotho deficient mice: high FGF23 and LVH
FGF23 and LVH in pediatric CKD
Leifheit-Nestler, Nephrol Dial Transplant 2016
German autopsy study
17 dialysis, 17 KTx, 24 controls
67% LVH in patients
Induction of cardiac FGF23-FGFR4
expression as well as a decreased
Klotho expression is associated with
LVH
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LVH depends on FGF23 but also on Klotho levels: loss of
Klotho in CKD breaks one’s heart!
Xie JASN 2015 / Fu & Liu JASN 2015
Heterozygous Klotho deficient mice
Klotho-deficient CKD mice display aggravated
cardiac fibrosis as compared to WT-CKD mice
Transgenic expression of soluble Klotho improves
cardiomyopathy in Klotho-deficient CKD mice
Anti FGF23 antibodies: can they be
relevant in CKD?
Antibodies against FGF23 improve
hyperparathyroidism…
Shalhoub JCI 2012
Early decreased PTH levels
But increased phosphate, calcium and 1-25 D
levels
But they also increase mortality…
Shalhoub JCI 2012
FGF23 and cardiomyocytes: a potential therapeutic target
Faul et al, J Clin Invest 2011
• FGFR inhibitors in a rat model of CKD (5/6th nephrectomy)
– Decreased LVH
– No modification of blood pressure
From prevention to treatment…
FGFR blockade can improve LVH in animal models
Di Marco NDT 2014
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So… should we trash anti FGF23
antibodies?
Wolf et al, JASN 2010
FGF23 and human diseases
Hypophosphatemic ricketsThe revolution in 2014: KRN23 in patients, short-term
Carpenter JCI 2014
• Adults with XLH
• 38 patients receiving KRN23 or placebo, IV or sc
• Single dose
Hypophosphatemic ricketsThe revolution in 2015: KRN23 in patients, ‘long-term’
Imel JCEM 2015
• Adults with XLH
• 28 patients receiving KRN23: 0.05 to 0.6 mg/kg every 28 days (SC)
• Then extension study 22 patients receiving 0.1 to 1 mg/kg every 28
days (SC)
International pediatric trials are ongoing
Conclusion
Scialla, Kidney International 2013
Back in the real life of a CKD patient…
Phosphate is a/the vascular toxin/silent killer
Shroff, Pediatric Nephrology 2013
Vascular calcifications
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Phosphate and longevity
Kuro-O Mech Ageing Dev 2010
Klotho -/-
mice
Rhinoceros
Elephant
Centenarian
human
Guinea pig
Gerbil
Dialysis patient
Conversion mg/dL: 0.323 mmol/L
FGF23, Klotho and CKD in 2017
• Both low Klotho and high FGF23
levels are delerious in CKD for LVH
• Both low 25-D and high FGF23 levels
are deleterious in CKD for infections
• FGF23 has become a therapeutic
target in genetic hypophosphatemic
diseases: the ongoing revolution!
• However FGF23 antibodies have
proved to be deleterious in CKD
• A potential role for drugs modulating
FGF-R and for recombinant Klotho in
the future?
• Clinical practice: target phosphate