Sandro Mazzaferro

Il Trattamento dei Disturbi del Metabolismo Minerale nell’IRC

AGGIORNAMENTIIN NEFROLOGIA CLINICA

XIII IncontroTeramo, 11-12 ottobre 2013

Aula Convegni II Lotto

Aspetti fisiopatologici ed epidemiologici

(Manoppello – PE)

Disturbances of Mineral Metabolism in CRF involve … …

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A possible «rule of … … …»

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IONS

At least …

1. Serum CalciumIntra- vs Extra-cellular Concentrations

Blood streamCell

Ca++ = 100 nmol/l

Intracellular Ca++: ~10.000 fold lower!!

Ca++ = 1.10 mmol/l

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There must be some mechanism that lowers

intracellular Ca++!

Ca++ asSecond Messenger

Smajilovic S. Br J Pharma 2011

CaSR: its discovery has changed the status of Ca

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Ca++ = 100 nmol/l

Ca++ = 1.10 mmol/l

Ca++ asFirst Messenger

Ca derangements in CRF• Hypo-Calcemia and/or negative Ca

balance:– Anxiety, Paresthesias, Cramps, Tetany, Seizures,

Abdominal pain, Congestive heart failure, Calcifications, etc.

– High PTH, High turnover bone, Osteopenia• Hyper-Calcemia and/or positive Ca

balance:– Weakness, Nausea, Vomiting, Polyuria,

Polydipsia, Hypertension, Lethargy, Coma– Low PTH, Low turnover bone, Calcifications

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2. Serum PhosphateIntra- vs Extra-cellular Concentrations

Intracellular P is ~50 times HIGHER

Blood streamCell

Remember, intracellular Ca is 10.000 times LOWER!(1.0 mmol/l vs 0.0001 mmol/l)

There must be some mechanism that increases

intracellular P. (!?!)

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Pi = 1.5 mmol/lPi = 70 mmol/l

Pi Receptor?

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No Pi Receptor identified so far.

Derangements of Pi in CRF• Hypo-Phosphatemia and/or negative Pi

balance:– Low cardiac output, Arrhytmia, Hypotension,

Astenia, Confusion, Seizures, Coma– High insulin, Low PTH, Pseudofractures,

Osteomalacia• Hyper-Phosphatemia and/or positive Pi

balance:– Hypocalcemia, Hypotension, Excitability,– High PTH, High turnover, Calcification

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3. Serum H+Intra- vs Extra-cellular Concentrations

Blood streamCell

H+ = 40 nmol/l

In general intra- and extra- cellular H+ are quite similar

H+ = 40 nmol/l

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Please note that:pH 7.30 = 50 nmol/lpH 7.50 = 30 nmol/l

Derangements of H+ in CRF

• Acidosis and/or Acidemia:– Fatigue, tachipnea, sleepness, confusion,

coma– Osteopenia/Malacia

• Alkalosis and/or Alkalemia:– Anxiety, nausea, tremor, twitching, spasm,

numbness, dizziness, coma – Calcifications

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HORMONES

At least …

1. PTH hormone & fragments

1-115

1-90

1-84

1-84

7-84

PTH fragments are produced in the cytosol, and are influenced by Ca++ and CaSR!

Friedmann P AmJPhy-RP 2006

PTH-Type I•Expressed in:

– Kidney, – Osteoblasts– Smooth muscle,– Brain,– Fetal tissues,

•Binds:– NH-term PTH (1-84);– PTH-rP

PTH- Type II•Expressed in:

– Brain,– Endothelium– Smooth muscle,– GI tract endocrine

cells,– sperm

•Not in Obl or kidney•Binds:

– TIP39,– NH-term PTH (1-84)

PTH Receptors

D’Amour P. Clin Biochem 2012

Type I and Type

II Receptors

C-term

PTH

Receptor

Derangements of PTH in CRF

• Hypoparathyroidism:– Low Ca, high Pi, low AP – Low turnover bone, Ectopic calcification

• Hyperparathyroidism:– High Ca, high Pi, high AP– High turnover bone, Ectopic calcification

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2. Vitamin D Metabolites & Hormone

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Vitamin D Receptor: expressed in almost every tissue

Derangements of Vitamin D in CRF

• Hypovitaminosis D:– HypoCa, high PTH, high AP– Bone Resorption/Osteomalacia/Penia– Other (pleiotropic?)

• Hypervitaminosis D:– Hyper Ca, low-high PTH, low-high AP– Bone mineralization, low turnover– Ectopic Calcifications– Other (pleiotropic?)

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3. FGF23-Klotho

Why together?

• FGF23 null vs Klotho null transgenic mice

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FGF23 null vs Klotho null

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Phenotype FGF23-/-

Serum P High

1,25-D level High

Serum Ca High

Bone Mine-ralization

Defective

Ectopic Calcification

Present

Arterio- sclerosis

Present

Lifespan Short

Kl -/-

High

High

High

Defective

Present

Present

Short

FGF23 Receptors, FGF23 and Klotho

Razzaque MS Trends in Mol Med 2006

Klotho (local and circulating) is essential for activity and selectivity of FGF23

Blood

[ H +]

[ Ca++]

[ P++]

[1,25D]

[PTH]

From Kidney to Bone and viceversa

Klotho

FGF23

Mazzaferro S. et al Arch. Biochem. Biophys. (2010)

Possible differences between the two?

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FGF23 regulation

• Systemic factors:– Pi ( = );– 1,25D ( = )

• Local factors (bone derived):– DMP1 deletion = increased FGF23;– Phex inactivation = increased FG23;– MEPE administration = increased FGF23

(Transcriptional and post-transcriptional mechanisms)

?

Feed-back system!

Blood

[ 1,25D]

[ P++]

From Bone to Kidney

FGF23

MEPE-ASARM cleavage

DMP1

PHEX

ASARM

Klotho

FGF23

FGF23 synthesis is affected not only by serum Pi and 1,25D, but also by the metabolism of other bone proteins

Mazzaferro S. et al Arch. Biochem. Biophys. (2010)

Klotho

Klotho functions outside FGF23Organ Activity Effect

Kidney NaPi2a/2c inactivation Hypophosphatemia

Renal TRPV5/6 Activation Ca reabsorption

Renal ROMK1 Activation Potassium secretion

Na/K ATPase Activation Ca homeostasis

Parathyroids Na/K ATPase Activation PTH stimulation

Choroid Plexus

Na/K ATPase Activation Ca homeostasis

Sytemic NaPi3 Reduction Vascular Calcification inhibition

Insulin/IGF-1 inhibition Insulin resistance – Anti-age

Wnt suppression Anti-age

Endothelial NO Up-regulation

Endothelial dysfunction protection

PiCaK

PTH

VC

InsAge

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S-K

loth

o, p

g/m

l

FG

F23

, pg

/ml

N CKD 2 CKD 3 CKD 4CKD 2 CKD 3 CKD 4

* **

(*) p<0.005 vs Normal

$

N

§

($) p<0.001 vs N(§) p<0.006 vs N, CKD-2, CKD-3

Mazzaferro S et al. Soluble alpha Klotho in Chronic renal failure. ISN 2012

Derangements of FGF23/Klotho in CRF

Low Klotho/High FGF23 Human Syndromes

• Human Klotho inactivating gene mutation– HyperPi, HyperCa, High 1,25D, High FGF23,

Calcinosis. • FGF23 excess related syndromes

– Primary: ADHR, ARHR, XLH, TIO

[Rickets, Osteomalacia]– Secondary: Chronic Renal Failure

[CV disease and mortality]

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ORGANS

At least …

1. Intestine(Absorption, Secretion, Excretion of Ca, Pi, H)

Carriers Receptors Hormones

TRP-V5,6 Vit. D Receptor 1,25 D

NaPi-2a,b PTH Receptor II PTH

Ca Sensing Receptor FGF23/Klotho

Pi Receptor (?)

Intestinal Endocrine functions:- several GI hormones,- possibly a Phosphatonin

2. Kidney(Filtration, Reabsorption, Excretion of Ca, Pi, H)

Carriers Receptors Hormones

TRP-V5,6 Vit. D Receptor 1,25 D

NaPi-2a,b PTH Receptor I PTH

Ca Sensing Receptor FGF23/Klotho

Pi Receptor (?)

Renal Endocrine functions:- Renin, Epo, Calcitriol,- Klotho

3. Bone(Resorption, Deposition, Ca, Pi, H)

Carriers Receptors Hormones

TRP-V5,6 Vit. D Receptor 1,25 D

NaPi-2a,b PTH Receptor I PTH

Ca Sensing Receptor FGF23/Klotho

Pi Receptor (?)

Bone Endocrine functions:- FGF23- Osteocalcin

Bone cells lineage (modern view)Hematopoetic

stem cell

Pre-osteoclast

Macrophage

Osteoclast

Pre-osteoblast

Osteoblast

Runx2

Stromal cell

Lining cell

Osteocyte

Systemic Hormones:-PTH, 1,25D, Estrogens, etcCytokines:- ILs, PGs, TGFb, etc

OPG/RANK/RANKL

Myocyte

MRF4

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No-more inactive!

+ Remodeling = mineral metabolism

Growth & Modeling

Organic Matrix- Non Collagenous Proteins (11%)

1. GAGs: - Proteoglycans, Hyaluronan;

2. Glycoproteins:- ON, SIBLINGs (OPN; BSP; DMP1; SPP1; MEPE), OPG, SOST, RDG contaning proteins, Thrombospondin

3. Γ-Carboxylic Acid containing:- MGP, OC

4. Other Proteins:- Growth factors (BMPs, FGFs), Enzymes (AP, TRAP, PHEX, MMPs), Absorbed from circulation (Albumin, Fetuin)

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Non-collagenous bone protein contribute to Ca and Pi fluxes from and into bone

Normal

CKDStage -2

FGF23DMP1MEPE

La disfunzione della «ghiandola osso» inizia già nelle fasi precoci della CKD

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A possible «rule of … … …»

IONS

ORGANS

HORMONESSystemic (CV) involvement or CKD-MBD

Targets for Mineral Metabolism Control in CRF

PTH

1,25DFGF23/Klotho

Ca

P

H

Available drugs for CKD-MBD

1. Phosphate binders

2. Vitamin D and analogs

3. Calcimimetics

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(again … … … )

Epidemiologic aspects

(in Dialysis)

Aim of the study:To evaluate- Drug prescription policy,- Biochemical control of SH,with new available drugs (from 2006 to 2008)

1. Drug Prescription policy:(a.) PTH inhibitors

Calcitriol p.o.

Calcitriol i.v.

Paricalcitol i.v.

Cinacalcet p.o.

Any Vitamin D from 50.8% to 58.2% (p<.001)

~2ug/w ~3.5ug/w ~45mg/d

1. Drug Prescription policy:(b.) Phosphate Binders

Changes in P binders prescription policyAny

Ca Acetate

Ca Carbonate Sevelamer

Aluminum

Average doses of P binders

Ca Acetate Ca Carbonate Sevelamer Aluminum

~2g/day ~2g/day ~2g/day~4g/day

2. Biochemical control of SH

Mean (SD) Values of PTH, Ca, and P During the Survey.

Baseline Month 6Month

12Month

18P

value

PTH, pg/mL

310.3 (292.4)

287.8 (252.2)

286.4 (248.1)

279.5 (250.1) 0.0002

Ca, mg/dL

9.1 (0.8)

9.0 (1.0)

9.0 (0.7)

9.0(0.7) 0.383

P, mg/dL

5.0 (1.4)

4.9(1.3)

5.0 (1.3)

5.0 (1.4) 0.085

Ca=calcium, P=phosphate, PTH=parathyroid hormone.

Patients at target (K/DOQI)?

PTH

Ca P

All three

Conclusions

• CKD-MBD = complex metabolic derangement of renal failure, with significant systemic involvement and morbidity/mortality.

• Its therapeutic management is rather difficult, even with new drugs,

• The «rule of 3» seems cute, but insufficient to help manage it properly

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EVOLVE: Study Design

Screening Phase

Up to 30 Days

TitrationPhase(Visits Q2

Wks)

Follow up Phase(Visits Q8 Wks)

Follow-up period = ~ 2.5 yearsEnrollment = ~ 1.5 years

Day 1 Week 20 Week 52

Event-driven study that concludes when approximately 1,882 subjects have experienced a primary composite event

Placebo plus standard of care(n = 1,900)

Cinacalcet plus standard of care (n = 1,900)

Adapted from: Chertow GM, et al. Clin J Am Soc Nephrol. 2007;2:898-905.

All patients could receive vitamin D sterols and phosphate binders, as necessary, at the discretion of the physician.

Trial Population• Hemodialysis • iPTH 300 pg/mL• Ca 8.4 mg/dL• Ca x P 45 mg2/dL2

Primary Composite Endpoint (ITT) not met:Non-significant* 7% Reduction in the Risk of Death or Nonfatal Cardiovascular Events in Patients with SHPT

Pro

port

ion

Eve

nt-f

ree

0.0

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Time (months)

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60

Hazard ratio, 0.93 (95% CI, 0.85, 1.02)

Log-rank test, P = 0.11*

Subjects at risk:

19481935

18421804

17391693

16381579

15561476

14721384

13841312

13031224

12301160

11771109

11151053

1051996

989940

679650

399404

113114

CinacalcetPlacebo

Kaplan-Meier plot of the time to the primary composite endpoint (death, myocardial infarction, hospitalization for unstable angina, heart failure, or peripheral vascular event) in EVOLVE™.

Adapted from Chertow GM, et al. N Engl J Med. Epub 2012 Nov 3; DOI: 10.1056/NEJMoa1205624

* The trial did not meet its primary endpoint in the unadjusted intent-to-treat analysis

CKD-MBD Working Group ERA-EDTA

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