Un approccio integrato della biologia dei sistemi per studiare il trasporto di ossigeno e il...
-
Upload
crs4-research-center-in-sardinia -
Category
Technology
-
view
389 -
download
1
description
Transcript of Un approccio integrato della biologia dei sistemi per studiare il trasporto di ossigeno e il...
Nicola LaiDepartment of Biomedical Engineering
Case Western Reserve University
Dicembre 21, 2011
A Systems Biology ApproachTo Study Metabolic Regulation
In Tissue/Organ SystemsIn Health And Disease States
Outline of PresentationIntroduction to Systems BiologyProjectsExperimental approaches to study energy metabolism at different whole body levels:
CellularTissue-OrganWhole Body
Integration of experimental data to computational model to study
O2 transport and metabolism in skeletal muscle (Diabetes)Fuel Homeostasis: Substrate Utilization (Cystic Fibrosis)
Relation between experimental and computational models for optimal design of experiments and to generate hypotheses
Systems Biology
Study of the interactions between the components of biological systems, and how these interactions give rise to the function and behavior of that system (e.g., the enzymes and metabolites in a metabolic pathway)
Organisms
Tissues
Organs
Cells
Proteins
Genes
Integrative Systems Biology
Approach
Discover Functional Properties of the
Biological Systems
Comprehensive data sets from distinct levels of biological systems;It is difficult to relate organ whole-organism function to cellular and sub-cellular function and structure properties;Integration of multi-scale data to build predictive mathematical models of the system;Investigate the behavior and relationships of all elements in a functioning biological system;
Systems Approach: Integration
Cellular Metabolism
All the chemical processes that make it possible for the cells to continue living
Cell
Metabolic Systems
Most metabolic pathways have been intensely studied;Little is known in quantitative terms about their control and integration with other pathways, as well as their interaction to regulate physiological variables (e.g., blood, glucose, muscle ATP) under normal and stress conditions;
Fell D. Understanding the Control of Metabolism, 1 997.
TitleSystems Biology Investigation of Muscle Exercise Metabolism in DiabetesGoalTo quantify the key factors responsible for metabolic and mitochondrial dysfunction in diabetes and elucidate the impact of exercise training on energy metabolism
AgencyNational Institute of Arthritis, Musculoskeletal & Skin Diseases
Ongoing Research Projects
TitleSystems Biology Approach to Growth Regulation in Cystic FibrosisGoal To investigate the patterns of energy homeostasis (energy utilization and imbalances) in control and cystic fibrosis (CF) mice using perturbations including pharmacologic treatment, genetic manipulations and altering energy balance by diet or exercise
AgencyInstitute of General Medical Sciences
Systems Biology Approach
1. Choose suitable biological model organism2. Characterize endocrine-metabolic components
of energy metabolism3. Generate plausible hypotheses explaining
differences between T2DM and control4. Develop predictive, quantitative multiscale
models of energy metabolism5. Perturb systematically system to validate and
refine model and to test hypotheses6. Generate new experimentally testable
hypotheses
Metabolic Characteristics in T2DM
Muscle metabolic functions decline with type 2 diabetes mellitus (T2DM)Metabolic dysfunction is accompanied by mitochondrial dysfunction and insulin resistance (IR)Mitochondrial dysfunction is related to IR, but the cause-and-effect relationship between them remains to be definedThe altered metabolic regulation under which insulin is less effective in inducing glucose utilization is not completely understood
Why study exercise metabolism
Muscle energy metabolism in healthy & disease state
Detect and prevent pathologies (e.g. Diabetes)Therapeutic intervention to ameliorate quality of life in elderly and subjects with metabolic disorders
Experimental Approach
Biological Systems
Acute Perturbation / Stimuli Chronic Stimuli / Conditions
-Training, Microgravity-Diseases(e.g. Diabetes, Myopathies)
-Exercise-Hypoxia, Hyperoxia-Drugs
System Outputs
-Physiological variables(e.g. Blood flow)-Metabolic variables(e.g. Substrates, Enzymes)
Whole body response to exercise
Stimulus Response
Physiological Process
Exercise Protocol
Time [min]
WR [watt]Range (80-200)
REST
WARM UP
ACTIVE
RECOVERY
PASSIVE
RECOVERY
Warm up (20)
CONSTANT
WORK RATE
0 50 100 150 200 250 300 350 400 450 5000
5
10
15
20
25
30
[second]
Cde
oxy [m
M]
Physiological responses to exercise
PulmonaryO2 Uptake
Cardiac Output
Muscle Oxygenation
Indirect Calorimetry
Bioimpedance Cardiography
NIR Spectroscopy
0 50 100 150 200 250 300 350 400 450 5000.00
0.25
0.50
0.75
1.00
1.25
1.50
[second]
VO
2 [L m
in-1]
0 50 100 150 200 250 300 350 400 450 5000.0
2.5
5.0
7.5
10.0
12.5
[second]
Q [L
min
-1]
Characterization of the physiological variable response to stimulus
Parameters
�A, Amplitude
�τ, Time Constant
�TD, Delay Time
Mathematical Model
t, Time [min]
YBL + A
YBL
TD
A
Rest Stimuli
+TD
+TD (1 )0
0 BL
( t TD t )/0 BL
t t Y( t ) Y
t t Y( t ) Y A e τ+ −
≤ =
> = + −
t0
Effect of time constant ( ττττ)on the physiological response
0 100 200 300 400 500 600 7000.3
0.6
0.9
1.2
1.5
1.8
[second]
VO
2 [L m
in-1]
τ=τ=τ=τ=30s
τ=τ=τ=τ=30s τ=τ=τ=τ=90s
VO2 Responses to Exercise in Human Subjects:Type II Diabetes Mellitus (T2DM) & Health (Control)
PAD
Regensteiner et al. 1998, Journal of Applied Physio logy
CONTROL T2DM
Impaired cardiac responses to exerciseAlteration O2 diffusion and/or utilization in skeletal muscle is also possible
Time [s] Time [s]
Dynamic response of pulmonary O2 uptake (VO2) in humans during exercise slower with CF than healthyVO2 response can be affected by pulmonary impairment but peripheral factors (O2 transport and metabolism) may also play a role
Control CF
Time [s] Time [s]
Hebestreit et al., 2005
VO2 Responses to Exercise in Human Subjects:Cystic Fibrosis (CF) & Health (Control)
Effect of Exercise on VO 2 responseto exercise in T2DM patients
Bradenburg et al., Diabetes Care 22, p1640–1646, 1999
T2DM τ=τ=τ=τ=72s
τ=τ=τ=τ=40s
Control
Linking Cell, Tissue/Organ systems & Whole Body
CellTissue/Organ Systems
Whole Body
Whole body & tissue-organ responses to exercise
PulmonaryO2 Uptake
PulmonaryO2 Uptake
-Blood O 2 Saturation-Tissue O 2Saturation-Muscle Blood Flow
-Blood O 2 Saturation-Tissue O 2Saturation-Muscle Blood Flow
LUNGSLUNGS
SKELETAL MUSCLESKELETAL MUSCLE
Cardiac OutputCardiac Output
HEARTHEART
Arterio/venous difference
Arterio/venous difference
Stimulus Response
Physiological Process
Measurements of Muscle Blood Flow (Q),Arterial and Venous O 2 concentrations
Cart,O2
Cven,O2
MEASUREMENTS
�Blood Samples: Arterial and venous O 2 concentration ( Cart,O2, Cven,O2
) by Oximeter �Tissue Biopsies: Metabolite concentrations by GS, M S�Muscle Blood Flow (Q) by thermo-dilution technique
CatheterRadial Artery
Catheter Femoral Vein
Muscle O2 Uptake
VO2m=Q (Cart,O2-Cven,O2
)
Cardio-respiratory & skeletal muscle responsesto exercise
VO2A , Alveolar Oxygen Uptake
Qleg, Muscle Blood Flow,Ca-Cv, Arterio-Venous diff.VO2leg, Muscle Oxygen Uptake
Grassi et al., JAP (1996) 80, p988-998
Linking Cell, Tissue/Organ systems & Whole Body
CellTissue/Organ Systems
Whole Body
Mitochondrial respiration responsesto different substrates
Stimulus Response
Water30°C
Water30°C
Electrode System
Buffer Solution
∆V
Substrates
Polarographic System
Oxygen consumption Rate
Magnetic mixer
Magnetic stir bar
Oxidative phosphorylation ratein healthy and disease states
Puchowicz et al., 377–385 , 2004
Functional defectsin dehydrogenase activities
The mitochondria of patient ‘C’Pyruvate oxidation is impaired
Defect in the pyruvate dehydrogenase complex
The mitochondria of patient ‘D’Glutamate and succinate oxidation are impaired
Defect in fumarase activity
Dynamic response of O 2 utilizationat different whole body levels
Cell
Skeletal Muscle
Whole Body
2.5 s
25÷30 s
30÷35 s
Biological Systems Time constant
Factors affecting bioenergetics function
CentralCardiovascular and respiratory systems
Ventilation;O2 Diffusion from Alveoli to pulmonary capillaryCardiac Output;
PeripheralSkeletal Muscle systems
O2 Diffusion from muscle capillary to myocytesMetabolic processes (Cytosol, mitochondria)
Linking Cell, Tissue/Organ systems & Whole Body
Cell
Tissue/Organ Systems
Whole Body
Cellular Energy metabolism
Multi-compartmental System Model
Species j reaction rate
Rc,j=Pc,j – Uc,j cytosol
Rm,j=Pm,j – Um,j mitochondria
InterstitialFluid
Capillary Blood
Cc,j | Rc,j
Pc,j Uc,j
Cm,j | Rm,j
Pm,j Um,j
Cytosol
Mitochondria
Cisf,j
Cb,jQ Ca,j Q Cv,j
Jb↔↔↔↔c,j
Jc↔↔↔↔m,j
Specie j
Ca,j: Arterial concentration
Cv,j: Venous concentration
Cb,j: Capillary blood concentration
Cisf,j: Interstitial fluid concentration
Cc,j: Cytosolic concentration
Cm,j: Mitochondrial concentration
Specie j transport rate
from blood to cytosol, Jb↔c,j
from cytosol to mitochondria, Jc↔m,j
Px,j =∑p βx,j,p φx,p
Ux,j = ∑u βx,j,u φx,u
φ Reaction flux
β Stoichiometric coefficient
Dynamic Mass Balance Equations
Blood (b): Vb
dCb, j
dt= Q C
a, j− C
b, j( )− Jb↔c, j
Cytosol (c): Vc
dCc, j
dt= β
c, j , pφ
c, p−
p∑ β
c, j ,uφ
c,uu∑ + J
b↔c , j− J
c↔ m, j
Mitochondria (m): Vm
dCm, j
dt= β
m, j , pφ
m, p−
p∑ β
m, j ,uφ
m,uu∑ + J
c↔ m, j
Q: Muscle blood flow
Cx,j: Species concentration in each domain (blood, cytosol or mitochondria)
Jb↔↔↔↔c,j : Transport fluxes between blood and cytosolic domain
Jc↔↔↔↔m,j : Transport fluxes between cytosolic and mitochondrial domain
φφφφp, φφφφu: Metabolic reaction fluxes: production or utilization
ββββp, ββββu: Stoichiometric coefficients.
Metabolic Reaction Fluxes
[ ][ ] [ ][ ]
[ ] [ ] [ ][ ] [ ] [ ] [ ][ ]1
max,f max,r
a b p q
a b a b p q p q
V A B V P Q
K K K K
A B A B P Q P Q
K K K K K K K K
φ−
=+ + + + + +
Ordered bi-bi Michaelis-Menten kinetics
max, f p qmax,r
a b eq
V K KV
K K K=
A B C D+ +�
Reaction
Haldane Relation
eq a b p qK , K , K , K , K
Metabolic Parameters
Inter-domain Transport Fluxes
, , , ,
,
, ,, ,
, , ,, ,
( ) px y j x y j x j y j
x y j
x j y jfx y j x y j
x y j x j x y j y j
J C C
J
C CJ T
M C M C
λ↔ ↔
↔
↔ ↔↔ ↔
= − = = − + +
PASSIVE
FACILITATED
Cytosol-Mitochondria (c↔m )
c↔m,p: CO2 and O2
c↔m,f: Pyr, FAC, Pi, CoA, H+, Cit, Mal
Blood-Cytosol (b↔c )
b↔c,p: Ala, Glr, CO 2, O2, H+
b↔c,f: Glc, Pyr, Lac, FFA
Transport Processes
Whole body model O 2 Transport betweenLungs & Skeletal muscle
Alveolar Space
Capillary
Tissue
Capillary
Tissue
Capillary
LUNGS
OTHER ORGANS organs
MUSCLE
VA(t), CIO2 CAO2
Q(t)
Qo
Qm(t)
CvenCart
Cven,m Cart,m
VO2p
VO2A
UO2m
VO2m
2
2 2 2
0
LbVO
O O O ,b
AA A I A A L
dCV V ( t )( C C ) J dv
dt↔= − − ∫&
2 2 2
2
2, , ,
,2
L L LO b O b O bA LO b
C C CQ D J
t v v↔
∂ ∂ ∂= − + +
∂ ∂ ∂
Dynamic balance of O 2 in Lungs
Lung Capillary Blood
2
2 2
,,
0
RbVRO c
R R RR O b O
dCV J dv M
dt↔= − +∫
Other Organs
2 2 2, ,( )A L A LO b L O O bJ PS P P↔ = −
2 2 2
2
2, , ,
0 ,2
R R RO b O b O bR RR O b
C C CQ D J
t v v↔
∂ ∂ ∂= − + +
∂ ∂ ∂
,0 R bv V< <
Alveoli
Tissue
Blood
0 Lbv V< <
2 2 2
2
20O O O
r
r r rr
C C CQ D ; v V
t v v
∂ ∂ ∂= − + < <
∂ ∂ ∂2 2 2, , ,( )R R R RO b R O b O cJ PS P P↔ = −
Arterial & Venous Systems O 2 Diffusion
Model Prediction of metabolic processesat cellular level: Cytosol and Mitochondria
Variations in Glycogen concentration
Under pathological conditions or with special diet, glycogen stores in skeletal muscle at rest can differ significantly
Response to Exercise
Li et al., AJPEM 298, p1198-1209, 2010
Model Prediction of metabolic processesat whole skeletal muscle
0
20
40
60
80
100
120
Model Simulation Exp.Data - Normoxia
Self Perfused (SP) Model Simulation Exp.Data - Normoxia
Pump Perfused (PP)
Q [m
L 10
0g-1
min
-1]
02468
1012141618
Model Prediction Exp.Data - Normoxia
Self Perfused (SP) Model Prediction Exp.Data - Normoxia
Pump Perfused (PP)
C
T A-V
[vol
%]
0 30 60 90 120 150 180 210 240 270 30002468
1012141618
Time [s]
Model Prediction Exp.Data - Normoxia
Self Perfused (SP) Model Prediction Exp.Data - Normoxia
Pump Perfused (PP)
VO
2 [m
LO2
100g
-1 m
in-1
]
MuscleBlood Flow
Arterio-Venous Difference
Muscle O 2Uptake
Effect of blood flow on VO 2m response to contraction
*Grassi et al., 2000JAP. 89: 1293-1301
Spires et al., 2011JAP. Submitted
Cart,O2
Cven,O2
CatheterRadial Artery
Catheter Femoral Vein
Model Prediction of metabolic processesat whole body level
-0.4
-0.3
-0.2
-0.1
0.0
0.1
0.2
∆∆ ∆∆StO
2m/S
tOw 2m
Model Simulation Experimental Data
-1 0 1 2 3 40.0
0.5
1.0
1.5
2.0
2.5
Time [min]
VO
2p [L
O2/
min
]
Model Simulation Experimental data
Oxygen Saturation
Oxygen Saturation
LUNGSLUNGS
MUSCLEMUSCLE
Cardiac Output
Cardiac Output
HEARTHEART
PulmonaryO2 Uptake
PulmonaryO2 Uptake
Dynamic responses of Muscle O2 saturation & Pulmonary O 2uptake to exercise
Factors affecting bioenergetics function
CentralCardiovascular and respiratory systems
Ventilation;O2 Diffusion from Alveoli to pulmonary capillaryCardiac Output;
PeripheralSkeletal Muscle systems
O2 Diffusion from muscle capillary to myocytesMetabolic processes (Cytosol, mitochondria)
Mathematical Modeling and Analysis: Hypotheses of cellular and physiological regulation
Hyp.1
Hyp.2
Hyp.3
Hyp.1: Impairment of cellular transport(e.g. facilitate diffusion)
Hyp.2: Activation/Inhibition of enzymatic reactions and/or metabolic pathway
Hyp.3: Impairment of substrate delivery(e.g., reduced blood flow)
Inputs:ExperimentalConditions
MathematicalModel
Outputs:Metabolic
Responses
Hypotheses
Cystic Fibrosis: Genetic Complex Disorder
Cystic Fibrosis is a complex, systemic, and multi-organ disorderAlthough CFTR gene is identified, many aspects of CF cannot be related directly to chloride channel defectAre pulmonary infection, inflammation, and growth retardation primary effects or secondary consequences?A Systems Approach is Needed !
Energy Homeostasis in CF
Insulin
Energy SupplyIntake of FAT, CHO, and proteinDigestion and absorption of nutrients
Energy UtilizationOxidation of FAT, CHO and ProteinLeaks: lower efficiency, cachexiaTotal energy expenditure
Energy BalanceBody composition
Hormonal and MetabolicCharacteristics of Tissues in CF
Skeletal MuscleLower work efficiency and inorganic phosphorus-to-phosphocreatine ratio during exerciseDysfunction of aerobic and anaerobic metabolism
LiverImpaired suppression of hepatic glucose production and non-oxidative glucose metabolism stimulated by insulinDe novo lipogenesis related to carbohydrate utilization
Adipose TissuePlasma palmitate 50% higher in human CF than control during insulin infusionImpaired suppression of adipose tissue lipolysis by insulin
System Model: Whole-Body & Organ-Tissues
Gas Exchange
Brain
Heart
SkeletalMuscle
Liver
Adipose
Others
GI
O2 CO2
InsulinGlucagon
Exercise
Organ system is connected via blood carrying substratesCarbohydrates and fat utilization during exerciseHormonal activation/inhibition of metabolic pathways
Multi-compartmental System Model
Species j reaction rate
Rc,j=Pc,j – Uc,j cytosol
Rm,j=Pm,j – Um,j mitochondria
InterstitialFluid
Capillary Blood
Cc,j | Rc,j
Pc,j Uc,j
Cm,j | Rm,j
Pm,j Um,j
Cytosol
Mitochondria
Cisf,j
Cb,jQ Ca,j Q Cv,j
Jb↔↔↔↔c,j
Jc↔↔↔↔m,j
Specie j
Ca,j: Arterial concentration
Cv,j: Venous concentration
Cb,j: Capillary blood concentration
Cisf,j: Interstitial fluid concentration
Cc,j: Cytosolic concentration
Cm,j: Mitochondrial concentration
Specie j transport rate
from blood to cytosol, Jb↔c,j
from cytosol to mitochondria, Jc↔m,j
Px,j =∑p βx,j,p φx,p
Ux,j = ∑u βx,j,u φx,u
φ Reaction flux
β Stoichiometric coefficient
Dynamic Mass Balance Equations
Blood (b): Vb
dCb, j
dt= Q C
a, j− C
b, j( )− Jb↔c, j
Cytosol (c): Vc
dCc, j
dt= β
c, j , pφ
c, p−
p∑ β
c, j ,uφ
c,uu∑ + J
b↔c , j− J
c↔ m, j
Mitochondria (m): Vm
dCm, j
dt= β
m, j , pφ
m, p−
p∑ β
m, j ,uφ
m,uu∑ + J
c↔ m, j
Q: Muscle blood flow
Cx,j: Species concentration in each domain (blood, cytosol or mitochondria)
Jb↔↔↔↔c,j : Transport fluxes between blood and cytosolic domain
Jc↔↔↔↔m,j : Transport fluxes between cytosolic and mitochondrial domain
φφφφp, φφφφu: Metabolic reaction fluxes: production or utilization
ββββp, ββββu: Stoichiometric coefficients.
Glucose
AlanineLactate Pyruvate
FAC
GLR
TG
DG
MG
MGDG
MG
GLR
GLR
MG
FA
FA
FA GLC
GAP1
G6P
PYR LAC
R5P
G3P1
GLY
F6P
NADH NAD+
NAD+ NADH
FAC
ACoA
CO2
FAC
VLDL-TG FFA
NADP+
NADPH
NADPH NADP+
FACDG
O2 H2O
NADH NAD+
ADP+Pi ATP
NADH
NAD+
NADH
NAD+
ATP
ADP+Pi
ATP
ADP
ATP
ADPPi
ATPADP+2Pi
NAD+NADH
ATP ADP+Pi
CoA
CoA
NAD+
NADH
ATP
ADP+Pi
CoA
CoA
CoA
G3P2
PYR
DG
GAP2
ALA
NADH
NAD+
NADH
NAD+
GLRATP ADP
Pi CoA
ATP
ADP+Pi
CO2
ATP ADP+Pi
CoA
Pi
CO2
O2
FAProteins
CO2CoA
ATGL
HSL
HSL
MGL
HSL ATP ADP
Glycerol
Metabolic Pathways in Adipose Tissue
Blood
Tissue
+ Epinephrine Insulin Work Rate
Tissue Specific Metabolic PathwaysPathways Brain Heart Muscle GI Liver
1. Glucose Utilization: GLC + ATP ⇒ G6P + ADP
2. G6P Breakdown: G6P + ATP ⇒ 2GA3P + ADP
3. GA3P Breakdown:GA3P + Pi + 2ADP + NAD+⇒ PYR + 2ATP + NADH
4. Gluconeogenesis-1: PYR + 3ATP + NADH ⇒ GAP + 3ADP + Pi + NAD+
5. Gluconeogenesis-2: 2GA3P ⇒ G6P + Pi
6. Gluconeogenesis-3: G6P ⇒ GLC + Pi
7. Glycogenesis: G6P + ATP ⇒ GLY + ADP + 2Pi
8. Glycogenolysis: GLY + Pi ⇒ G6P
9. Pyruvate Reduction: PYR + NADH ⇒ LAC + NAD
10. Lactate Oxidation: LAC + NAD ⇒ PYR + NADH
11. Glycerol Phosphorylation: GLR + ATP ⇒ G3P + ADP
12. GA3P Reduction: GA3P + NADH ⇒ G3P + NAD
13. Glycerol-3-P Oxidation: G3P + NAD ⇒ GA3P + NADH
14. Alanine Formation: PYR ⇒ ALA
15. Alanine Conversion: ALA ⇒ PYR
16. Pyruvate Oxidation: PYR + CoA + NAD ⇒ ACoA + NADH + CO2
17. Palmitate Oxidation: FA+8CoA+14NAD+2ATP ⇒ 8ACoA+14NADH+2ADP+2Pi
18. Palmitate Synthesis: 8ACoA + 7ATP + 14NADH ⇒ FA + 8CoA + 7ADP + 7Pi + 14NAD
19. Lypolysis: TG ⇒ 3FA + GLR
20. Triglyceride Production: 3FA + G3P + 6ATP ⇒ TG + 6ADP + 6Pi
21. TCA Cycle: ACoA + 4NAD + ADP + Pi ⇒ 4NADH + CoA + ATP +2CO2
22. Oxygen Consumption: 2NADH + 6ADP + 6Pi + O2 ⇒ 2NAD + 6ATP
23. Phosphocreatine Breakdown: PCR + ADP ⇒ CR + ATP
24. Phosphocreatine Synthesis: CR + ATP ⇒ PCR + ADP
25. ATP Hydrolysis: ATP ⇒ ADP + Pi + Energy
Skeletal Muscle/Adipose Tissue Interactions
ALALAC PYR
FAC
GLR
TG DG MG
MGDG MGGLR
GAP2
PYRLAC
G3P2
NADH
NAD+
NAD+ NADH
ACoA
CO2
VLDL-TG FFA
NAD+NADH
DG
O2 H2ONADH NAD+
ADP+Pi ATP
NADHNAD+
NAD+ NADH
ATPADP+Pi
CoA
CoA
NAD+
NADHATP
ADP+Pi
CoA
CoA
CoA
ALA
ADP+PiATP
CoA
Pi
CO2
O2
FA
Proteins
CO2CoA
ATGL
HSL HSL
MGL
HSL
ATP ADP
GLRLPL
MGGLR
Pi
G3P1
GAP1
NADH
NAD+
ATP
ADP+Pi
ATPADP+Pi
ADP+Pi
ATP
GLC
GLC
G6P
R5P
GLY
F6P
NADP+
NADH
ATP
ADP
ATP
ADP
Pi
ADP+2PiATP
CO2
NADH
NAD+
–
–
–
–
–
+
+
+
Blood
Tissue
GLC
ALALAC PYR
GLC
GAP
G6P
PYRLAC
G3P
ACoA
CO2
FFA
NADH
NADH
O2 H2ONADH NAD+
ADP+Pi ATP
NADH
NAD+
ATP
ADP+Pi
ATP
ADP
ATP
ADP
NAD+NADH
NAD
NAD+ ATP
ADP+Pi
CoA
PYR
ALA
GLRATPADP
ADPATP
CoA
CO2
FA
CO2
CoA
TG ATP ADP
GLR
TG O2Blood
Tissue
PCR CR
ADP ATP
ATP ADP
NAD+ NADH
NADHNAD+
GLYPi
ATPADP+2Pi
ADP
ATP
Pi
Experimental protocol and measurements
Exercise maximal test;
Exercise at moderate work rate (WR) equivalent to 50% of VO 2peak
Time [min]
WR [watt]
100
REST
WARM UP
50
CONSTANT
WORK RATE
60 minute
MEASUREMENTS
Blood
Hormones:Insulin;NorepinephrineEpinephrineGrowth Hormon (GH)
Substrates:Lactate
GlycerolGlucoseNonesterified Fatty Acid
TissueSubstrates:
Dialysate Glycerol
PROTOCOL
Koppo et al., 2010
Hormone responses to exercise
-10 0 10 20 30 40 50 60 70 800
5
10
15
20
25
30
35
Glucagon Model Simulation Experimental Data
Insulin Model Simulation Experimental Data
Hor
mon
e [p
m]
Time [min]
-10 0 10 20 30 40 50 60 70 80-50
0
50
100
150
200
250
300
350
400
450
Model simulation Experimental Data
Epi
neph
rine
[pm
]
Time [min]
Koppo et al., 2010
Glucose Homeostasis During Exercise
-10 0 10 20 30 40 50 60 70 800
200
400
600
800
1000
1200
1400
1600
1800
2000
Rat
e [µ
mol
/min
]Time [min]
Glucose Utilization Production
-10 0 10 20 30 40 50 60 70 800
1000
2000
3000
4000
5000
6000
Model Simulation Experimental Data
Glu
cose
[µm
mol
/min
]
Time [min]
Koppo et al., 2010
Plasma Metabolite Responses to Exercise
-10 0 10 20 30 40 50 60 70 800.6
0.8
1.0
1.2
1.4
Fat
ty A
cid,
FA
/FA
0 [-]
Time [min]
Model Simulation Experimental Data
-10 0 10 20 30 40 50 60 70 800.0
0.5
1.0
1.5
2.0
2.5
3.0
Lact
ate,
LA
C/L
AC
0 [-]
Time [min]
Model Simulation Experimental Data
Koppo et al., 2010
Glycerol Responses to Exercise
Plasma Adipose Tissue
-10 0 10 20 30 40 50 60 70 800.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Gly
cero
l, G
LC/G
LC0 [-
]
Time [min]
Model Simulation Experimental Data
-10 0 10 20 30 40 50 60 70 800.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Model Simulation Experimental Data
Gly
cero
l, G
LC/G
LC0 [-
]Time [min]
Koppo et al., 2010
Hypothesis: Fatty Acid Oxidation Impaired inSkeletal Muscle at High-intensity Exercise
Transport of long-chain fatty acid into mitochondria impaired via CPT-I inhibition Perfusion of adipose tissue inadequate to deliver fatty acid to skeletal muscleLipolysis inhibited via lactate or high catecholamine concentration
Effect of Adipose Tissue Blood Flowon Fatty Acid oxidation in skeletal muscle
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
50%30%
SMSMSMSMSM
SMAT
ATATATAT
AT
150%100%10%
Rat
e [m
mol
/min
]
Fatty Acid (FA) Release of Adipose Tissue (AT) FA Oxidation of Skeletal Muscle (SM)
Lipolysis FA Uptake
Rest
Exercise**Horizontal axis: ATBF/ATBF0 adipose tissue blood f low at steady-state moderate exercise relative to basal physiological v alue
Relation between experimental and computational models to optimal design experiments and generate hypotheses
Integrative Systems Biology Approach
AimSupport the iterative process in defining
alternative hypotheses, and designing optimum experiments
ImpactDesign of experimental protocols for specific
evaluation of disease and improved treatments based on simulations with experimentally validated mechanistic models
Conclusion
Physiological-based models of a complex system can
Integrate knowledge about componentsIncorporate interactions of system elementsFacilitate quantitative understanding of function
Hierarchical multilevel models provide means
For testing hypotheses For predicting critical experiments
Projects & Sponsors
Agency: NASA, National Aeronautics and Space AdministrationProject: Time Course of Metabolic Adaptation during Loading & Unloading
Agency: NSF, National Science Foundation
Project: Database-enabled tools for Regulatory Metabolic Networks
Agency: NIDDK, National Institute of Diabetes and Digestive & Kidney Diseases
Project: Systems Biology Approach to Growth Regulation in Cystic Fibrosis
Agency: Ministero degli Affari Esteri - International Environmental & Scientific Affairs Department of State.
Project: Central and peripheral factors contributing to the impaired oxidative metabolism in microgravity: experimental and theoretical approach
Agency: NIGMS - National Institute of General Medical SciencesProject: Center for Modeling Integrated Metabolic Systems