Evaluation du métabolisme osseux et minéral René Rizzoli

Lausanne, 13 mars 2008
Evaluation du métabolisme
osseux et minéral
René Rizzoli
Service des maladies osseuses
[Centre collaborateur de l’OMS pour la prévention de
l’ostéoporose]
Département de réhabilitation et gériatrie
Hôpitaux universitaires et Faculté de médecine de Genève
Mme W. 74 ans
Fatigue, Pouteau-Colles, pas d’autre fracture
Taille 163 (- 3 cm)
Pas d’autre plainte, sinon un épisode de
colique néphrétique à l’âge de 68 ans
Mme W. 74 ans
Fatigue, Pouteau-Colles, pas d’autre fracture
Taille 163 (- 3 cm)
Pas d’autre plainte, sinon un épisode de colique
néphrétique à l’âge de 68 ans
FSC normale
Calcium
2.60 (2.20-2.60)
Phosphate 0.82 (0.80-1-35)
Créatinine 90
Calcium: its role
Calcium
Bone
Extraskeletal
• Skeletal rigidity
(hydroxyapatite)
• Calcium store
• Enzymes
• Muscles
• Nerves
• Secretion
• Cell signalling
Calcium homeostasis
The regulation of calcium homeostasis
is aimed at maintaining
extracellular ionized calcium concentration
as constant as possible,
in a very narrow range.
Calcium in the body
Cells:
Extracellular fluid:
10 g
1g
Bone and teeth: 1200 g
Circulating calcium
Protein-bound
mostly albumin
1.0 mmol/l
40%
Ionized
1.2 mmol/l
50%
Complexed
(citrate,
bicarbonate,
phosphate,etc)
10%
Total calcium: 2.4 mmol/l
Protein-Corrected Plasma Calcium (mM)
= Ca / [prot/160 + 0.55]
Albumine-Corrected Plasma Calcium (mM)
= Ca + [0.02 x (40-Albumine)]
Mme W. 74 ans
Fatigue, Pouteau-Colles, pas d’autre fracture
Taille 163 (- 3 cm)
Pas d’autre plainte, sinon un épisode de colique
néphrétique à l’âge de 68 ans
FSC normale
Calcium
2.60 (2.20-2.60) (albumine 36 -> Ca 2.68)
Phosphate 0.82 (0.80-1-35)
Créatinine 90
Daily calcium fluxes controlling
calcium homeostasis
Diet
Cells
1000 mg
Accretion
Absorption
300 mg
400 mg
Extracellular
fluid
Loss
Resorption
200 mg
Filtered
Faeces
800 mg
10000 mg
300 mg
Reabsorbed
9800 mg
Urinary excretion: 200 mg
Daily calcium fluxes controlling
calcium homeostasis
Diet
Cells
PTH
1000 mg Calcitriol
+
+
Accretion
Absorption
300 mg
400 mg
Extracellular
fluid
Loss
Resorption
200 mg
Filtered
Faeces
800 mg
10000 mg
PTH
+
+ 300 mg +
PTH
Reabsorbed
9800 mg
Urinary excretion: 200 mg
Calcitriol
Phosphate in the body
• Skeleton : structural constituent
(hydroxyapatite)
85% 15%
• Cells
- cell metabolism and
energy regulator
- signal transduction
• ECF
- acid–base homeostasis
Total body store = 800 g
Daily Phosphate Fluxes Controling
Phosphate Homeostasis (mg / day)
Diet
(1200)
Soft Tissues
Absorption
(950)
Secretion
(150)
Accretion
(250)
Extracellular fluid
Filtered load
(4'300)
Faeces
(400)
Urine
(800)
Resorption
(250)
Reabsorption
(3'600)
Daily Phosphate Fluxes Controling
Phosphate Homeostasis (mg / day)
Diet
(1200)
Calcitriol
PTH
Soft Tissues
+
+
Absorption
(950)
Secretion
(150)
+
InsulinAccretion
(250)
Extracellular fluid
Resorption
(250)
+
Filtered load
(4'300)
Faeces
(400)
Reabsorption
(3'600)
-
+
PTH
Calcitriol
IGF-1
Low Pi diet
Urine
(800)
PTH
High Ca++
Evaluation of calcium-phosphate metabolism
Example:
•Variable
Plasma Calcium
•Mechanism
Intestinal Absorption
Bone Turnover
Renal Tubular Reabsorption
•Controler
PTH
Calcitriol
Other Hormones and cytokines
Intestinal Calcium Absorption
Lumen
ECF
Channels
(Vit D ±)
= Transcellular
= Paracellular
Rate-Limiting Step:
Ca++
Calbindin D 9k
(Vit. D +++)
Absorption Depends on:
- Chemical Form
- pH
- Sojourn Time
Ca-ATPase
(Vit. D ++)
Intestinal Calcium Absorption:
Methods of Measurement
1. Metabolic Balance (with nonabsorbable marker)
Net Absorption = Dietary Intake - Fecal Excretion
2. Absorption of Isotopic Minerals
(Single or Double, Radioactive or Stable)
3. Segmental Intestinal Absorption (Segmental Perfusion)
4. Indirect Assessment
- Urinary Calcium Excretion
Before and After an Acute Oral Calcium Load
(Pak ’s Test)
- 24-Hour Urinary Calcium Excretion
Calcium Absorption Test (Pak’s Test)
Breakfast with
1000 mg Calcium
Time (min) 0
120
Collect
Urine
Miction
Dosage
240
Discard
360
Collect
Calcium/
Creatinine
Calcium/
Creatinine
(Phosphate,cAMP)
(Phosphate,cAMP)
n: Increase Calcium/Creatinine < 0.5
Serum
(optional)
Calcium,Phosphate,
Creatinine,PTH
Calcium,Phosphate,
Creatinine,PTH
Evaluation of Main Calcium Fluxes
Fasting Urinary Calcium/Creatinine
->
( > 0.5 mmol/mmol)
Net Bone Resorption
24 h Urinary Calcium Excretion ( > 7.5 mmol/d in Men,
> 6.25 mmol/d in Women)
->
Net Intestinal Calcium Absorption
(and/or Net Bone Resorption)
Urinary Pi > 32 mmol/d
-> Dairy Products Origin
Urinary Sodium > 200 mmol/d -> High Salt Intake Origin
Evaluation of calcium-phosphate metabolism
Example:
•Variable
Plasma Calcium
•Mechanism
Intestinal Absorption
Bone Turnover
Renal Tubular Reabsorption
•Controler
PTH
Calcitriol
Other Hormones and cytokines
Bone Remodeling
1. Maintenance of Mechanical Strength
(Replacement of Fatigued Bone,
Prevention of Excessive Aging)
2. Supply of Bone Marrow with Growth Factors
3. Mineral Homeostasis (Calcium Release)
Sex Hormone
Deficiency
->
Increased
Remodelling
Manolagas et al., NEJM, 1995
Remodelling cycle
in adult human bone
Remodelling
completed
Resting stage
~200
days
Resorption
20 days
Reversal phase
Formation 150 days
Morphometry on iliac crest
structural parameters
PRIMARY
MEASUREMENTS
T.Ar.
B.Ar.
B.Pm
.
1,2,3.. N.Bf.
Ct.Ar.
1
Vd.Ar.
Ct.Wi
3
2
DERIVED
PARAMETERS
BV/TV, Tb.Th., Th.N.
N.Bf./B.Ar., Por,....
INDICATIONS TO TRANSILIAC BONE BIOPSY
•Suspected Osteomalacia
•Characterization of Renal Osteodystrophy
•Suspected Hereditary Bone Disease
•Osteoporosis in Young Individuals
Adapted from Eriksen et al. 1994
hrpQCT ->
« Virtual Bone Biopsy »
•82 µm
•2.6 min
•< 5µSv
Biochemical markers of bone turnover
Formation markers
Resorption markers
• S-Osteocalcin
• U-Hydroxyproline
• S-Bone specific alkaline
phosphatase
• U-Hydroxylysine
• S-Procollagen type-1
• U-Deoxypyridinoline
N-propeptide
• S-Procollagen type-1
C-propeptide
• U-Pyridinoline
• S-Bone sialoprotein
• S-Acid phosphatase
• S-Tartrate-resistant acid
phosphatase
• S-/U-Type-1 collagen
telopeptides (CTX, NTX)
Potential Uses of Markers of
Bone Remodeling
-Identify patients who need treatment
• Correlate with bone loss
• Correlate with fracture risk
-Help in selecting therapeutic agent
-Early indicator of response to treatment
-Evaluate patients who are not responding to
conventional treatment
Hip Fracture Risk
Odds-ratio
5
4
3
2
1
Low hip
BMD
high
U-CTX
Garnero et al.,
al., 1996
Low BMD
+
high CTX
Variability and Temporal
Patterns of Change
Bone Mineral Density Bone Turnover
Δ
Δ
0
0
1- 2 yrs.
Delmas P., 2000
Precision Error
3 -6 months
Collagen
Type I collagen epitopes and Cathepsin K cleavage sites
NTX
ICTP
CK
a2 (I) JYDGKGVG
CTX
CK
CK
CK
GPP-SAGFDFSFLPQPPQ EKAHDGGR a 1
N
C
CK
Deoxypyridinoline
Pyridinolines
CK
Garnero et al., JBC, 1998
Sassi et al., Bone, 2000
Mean Urinary NTX
from Start of FIT Through FLEX (Per Protocol)
70
60
Start of FLEX
25
15
5
–5
–15
25%
0
12
24
36
48
60
50
Premenopausal
Range
NTX (pmol/µmol creatinine)
-- ALN / Placebo
-- ALN / ALN (Pooled 5 mg and 10 mg35groups)Mean Percent Change
40
30
20
10
F 0 F 1 F 2 F 3 F 4 FL 0 FL 1 FL 2 FL 3 FL 4 FL 5
F = FIT, FL = FLEX
Year
Black et al., JAMA 2006
Different Effects of Bisphosphonates and
Estrogen Therapy on Free and Peptide-Bound
Bone Cross-links Excretion
(Garnero et al., J. Bone Min. Res. 10:641-649,1995)
Cross-links:
Total
Peptide-Bound
Free
Bisphosphonates
Decr.
Decr.
No change
Estrogen
Decr.
Decr.
Decr.
Effects hPTH(1-34) on bone Turnover
Urine
N-telopeptide
Neer et al 2001
% Change (±
(±SE)
Median % Change (±SE)
Bone-Specific
Alkaline Phosphatase
140
120
100
80
60
40
20
0
-20
Placebo
PTH 20
PTH 40
0
6
12
18
24
500
400
300
200
100
0
Placebo
PTH 20
PTH 40
01 3 6
12
18
Months
24
Biochemical Markers of Bone
Turnover
Influenced by:
25
• Individual Variation
• Assay Variation & Performance
20
Mean / SEM
PreMP
Early MP
15
DPyd/Cerat
• Pre-analytical Conditions
-Sample Storage
-Diurnal Variation
-Food Intake
Late MP
10
5
0
-5
-10
-15
-20
17
20
23
2
5
8
11
14
17
Time (Hours)
• Renal Function
A.Schlemmer et al. J Bone Miner Res 1994;9:1883
Myeloid
Progenitor
Osteoclast
Precursor
Active Osteoclast
RANK
RANKL
OPG
Osteoblast / Stromal Cell
OPG =Osteoprotegerin
RANKL = RANK Ligand
RANK =Receptor Activator of Nuclear Factor-kB
TRAIL = TNF-related Apoptosis-Inducing Ligand
TRAIL
Myeloid
Progenitor
Osteoclast
Precursor
Active Osteoclast
RANK
RANKL
OPG
Osteoblast / Stromal Cell
TRAIL
Myeloid
Progenitor
Osteoclast
Precursor
CSF-1
RANK
RANKL
1,25D
PGE2
PTH
IL-11
Active Osteoclast
OPG
TRAIL
TGFß
Estrogen
Osteoblast / Stromal Cell
Evaluation of calcium-phosphate metabolism
Example:
•Variable
Plasma Calcium
•Mechanism
Intestinal Absorption
Bone Resorption
Renal Tubular Reabsorption
•Controler
PTH
Calcitriol
Other Hormones and cytokines
Renal calcium handling
Filtered
10000 mg/day
65%
+
–
ECF
contraction
/expansion
ECF: extracellular fluid
8%
• Acidosis ––
• Pi depletion
––
• PTH
25
%
–
Loop diuretics
+
• PTHrP
+
• Thiazides +
• Alkalosis
+
200 mg/day
Renal Tubular Reabsorption of
Calcium or Phosphate
U Ca Excretion
TRCaI
Plasma Calcium
U Pi Excretion
TmPi / GFR
Plasma Phosphate
Renal Tubular Reabsorption of
Calcium or Phosphate
U Ca Excretion
U Pi Excretion
PTH
TRCaI
Plasma Calcium
PTH
TmPi / GFR
Plasma Phosphate
U/P Ca / U/P creatinine
Tubular Reabsorption of Calcium Index
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
1.4 1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4
TRCa I / plasma Ca
Ca-Creat. in plasma and urine -> FECa -> Nomogram -> TRCaI
0.0
1.8
0.4
1.6
0.6
1.4
0.8
99
0.
1.2
5
9
1
.
0
0
0.
90
5
.
0
0
1.0
0
0. 0
8
.
1
0 70
0.
0 0. 0
2
0.8
0. 30 0.6 0
.
5
0 40 0.
0. 50
40
.
0
0.6
0.
0
0
3
6
0.
0.
70
200.4
.
.
0
0
0
8
10
.
0.
0
0
9
0.
0.0 0
0
1.
5.0
4.0
3.0
P
1.0
1.2
1.0
1.8
5.0
2.0
n
io
et
cr
ex
1.6
l
na
4.0
2.0
tio
1.4
ac
3.0
Fr
Plasma Pi
0.2
TR
2.0
2.0
0.0
Renal threshold Pi (TmPi/GFR)
1.0
0.0
Evaluation of calcium-phosphate metabolism
Example:
•Variable
Plasma Calcium
•Mechanism
Intestinal Absorption
Bone Turnover
Renal Tubular Reabsorption
•Controler
PTH
Calcitriol
Other Hormones and cytokines
Mme W. 74 ans
Fatigue, Pouteau-Colles, pas d’autre fracture
Taille 163 (- 3 cm)
Pas d’autre plainte, sinon un épisode de colique
néphrétique à l’âge de 68 ans
FSC normale
Calcium
2.60 (2.20-2.60) (albumine 36 -> Ca 2.68)
Phosphate 0.82 (0.80-1-35)
Créatinine 90
PTH
9.5 (1.0-6.5)
Secretion of parathyroid hormone
Parathyroid cell
PTH (1–84)
Ca++
++
Ca++
1
Ca
++
++
Calcium sensor
84
PTHsynthesis and secretion
PTH
Human Parathyroid Hormone
1-34 and 1-84
1
H2N-
Ser
10
Val
Ser
Glu
Ile
Gln
Leu
Met
His
Asn
Leu
20
Gly
Glu
Val
Arg
Glu
Met
Ser
Asn
Leu
His
Lys
Arg
Lys
Lys
Leu
Gln
Asp
Val
His
Asn
Phe
Trp
Leu
30
40
50
60
70
80
- COOH
Parathyroid hormone
Cleavage Site: 33-34 + 36-37
in Liver and Kidney
1
Epitope:
84
Half-Life:
•N-terminal
< 4 min
•C-terminal
>90 min
•Mid-molecule
4 min
•Intact
•Intact «bioactive»
2-
7-
PTH
4
2
7.0
1
1.0
°
°
3
°
6
°
2.25
2.60
Plasma Calcium
°
5
°
JCEM 90:6370-2,2005
Bioactive
Intact
Magnesium deficiency
Magnesium deficiency
PTH secretion and/or action
Hypocalcemia
Parathyroid hormone/parathyroid
hormone-related protein
1 13
Chromosome
PTH (9.6 kD)
11
12
84
PTH-rP (16 kD)
homology: 62%
141
Effects of parathyroid hormone-related
protein in malignancy
Parathyroid
gland
cAMP
PTH
PTH-rP
Tumor
1,25(OH)
D
2
2 3
Tubular
Formation
reabsorption
Ca - Pi Absorption
Ca - Pi
Resorption
Hypercalcemia
+
Low PTH
+
High cyclic AMP
=
PTHrP
Vitamin D metabolism
UV light
Skin
Diet
80%
20%
(cholecalciferol)
25OHD3
1,25(OH)
D
2 3
Target organs
Vitamin D
+
• PTH
• Hypocalcemia
• Hypophosphatemia
• IGF-1
Circulating forms of vitamin D
Half-life
• Vitamin D
• 25OH D 3
4 – 5 days
Circulating
levels
1 – 5 nmol/l
10 – 20 days 20 – 100 nmol/l*
• 1,25(OH)2D3 5 – 18 hours 50 – 150 pmol/l
*Reflects vitamin D supply and status
(1991)
2002
id
Id
T-Score
< - 2.5
Id
Id
id