A Systems Biology ApproachTo Study Metabolic Regulation   In Tissue/Organ Systems In Health And Disease States            ...
Outline of PresentationIntroduction to Systems BiologyProjectsExperimental approaches to study                      energy...
Systems BiologyStudy of the interactions between the components ofbiological systems, and how these interactions giverise ...
Systems Approach: IntegrationComprehensive data sets from distinct levels ofbiological systems;It is difficult to relate o...
Cellular MetabolismAll the chemical processes that make it possible forthe cells to continue living Cell
Metabolic SystemsMost metabolic pathways have beenintensely studied;Little is known in quantitative terms abouttheir contr...
Ongoing Research ProjectsTitleSystems Biology Investigation of Muscle Exercise Metabolism in DiabetesGoalTo quantify the k...
Systems Biology Approach1. Choose suitable biological model organism2. Characterize endocrine-metabolic components   of en...
Metabolic Characteristics in T2DM  Muscle metabolic functions decline with type 2  diabetes mellitus (T2DM)  Metabolic    ...
Why study exercise metabolismMuscle energy metabolism in healthy & diseasestateDetect and prevent pathologies (e.g. Diabet...
Experimental Approach                               -ExerciseAcute Perturbation / Stimuli   -Hypoxia, HyperoxiaChronic Sti...
Whole body response to exercise Stimulus                   Response            Physiological              Process
Exercise Protocol  WR [watt]Range (80-200)Warm up (20)                                               Time                 ...
Physiological responses to exercise                                                                                       ...
Characterization of the physiological        variable response to stimulusMathematical Modelt ≤ t0 +TD Y( t ) = YBLt > t0 ...
τ                           Effect of time constant (τ)                         on the physiological response             ...
VO2 Responses to Exercise in Human Subjects:      Type II Diabetes Mellitus (T2DM) & Health (Control)                     ...
VO2 Responses to Exercise in Human Subjects:              Cystic Fibrosis (CF) & Health (Control)                      Con...
Effect of Exercise on VO2 response                to exercise in T2DM patients                          Control           ...
Linking Cell, Tissue/Organ systems & Whole BodyWhole Body                                       Cell             Tissue/Or...
Whole body & tissue-organ responses to exerciseStimulus                     Response                                      ...
Measurements of Muscle Blood Flow (Q),        Arterial and Venous O2 concentrations                           Catheter    ...
Cardio-respiratory & skeletal muscle responses                      to exercise                            VO2A , Alveolar...
Linking Cell, Tissue/Organ systems & Whole BodyWhole Body                                       Cell             Tissue/Or...
Mitochondrial respiration responses        to different substrates         Stimulus                                  Respo...
Oxidative phosphorylation rate                 in healthy and disease statesFunctional defectsin dehydrogenase activitiesT...
Dynamic response of O2 utilization       at different whole body levels  Biological Systems      Time constant     Cell   ...
Factors affecting bioenergetics function  Central      Cardiovascular and respiratory systems            Ventilation;     ...
Linking Cell, Tissue/Organ systems & Whole Body                                    Whole Body             Tissue/Organ Sys...
Cellular Energy metabolism
Multi-compartmental System Model                                           Capillary Blood                                ...
Dynamic Mass Balance Equations                                               (            )                              d...
Metabolic Reaction FluxesReactionA+ B            C+DOrdered bi-bi Michaelis-Menten kinetics           Vmax,f [ A][ B ] Vma...
Inter-domain Transport FluxesTransport ProcessesBlood-Cytosol (b↔c )                  Cytosol-Mitochondria (c↔m )b↔c,p: Al...
Whole body model O2 Transport between                      Lungs & Skeletal muscle                                        ...
Model Prediction of metabolic processes       at cellular level: Cytosol and Mitochondria  Response to Exercise  Variation...
Model Prediction of metabolic processes            at whole skeletal muscle                                               ...
Model Prediction of metabolic processes                                        at whole body level                      0....
Factors affecting bioenergetics function  Central      Cardiovascular and respiratory systems            Ventilation;     ...
Mathematical Modeling and Analysis: Hypotheses of cellular and physiological regulation  Inputs:                          ...
Cystic Fibrosis: Genetic Complex Disorder    Cystic Fibrosis is a complex, systemic,    and multi-organ disorder    Althou...
Energy Homeostasis in CFEnergy Supply Intake of FAT, CHO, and protein Digestion and absorption of nutrientsEnergy Utilizat...
Hormonal and Metabolic        Characteristics of Tissues in CFSkeletal Muscle  Lower work efficiency and inorganic phospho...
System Model: Whole-Body & Organ-Tissues                                    Gas Exchange                                  ...
Multi-compartmental System Model                                           Capillary Blood                                ...
Dynamic Mass Balance Equations                                               (            )                              d...
Metabolic Pathways in Adipose Tissue     Lactate       Pyruvate                   Alanine                                 ...
Tissue Specific Metabolic Pathways                                         Pathways                                 Brain ...
Skeletal Muscle/Adipose Tissue Interactions                                                                               ...
Experimental protocol and measurements WR                    PROTOCOL                         MEASUREMENTS [watt]         ...
Hormone responses to exercise                     450                                                                   35...
Glucose Homeostasis During Exercise                       6000                                                            ...
Plasma Metabolite Responses to Exercise                           1.4                                                     ...
Glycerol Responses to Exercise                                            Plasma                                          ...
Hypothesis: Fatty Acid Oxidation Impaired in Skeletal Muscle at High-intensity Exercise  Transport of long-chain fatty aci...
Effect of Adipose Tissue Blood Flow     on Fatty Acid oxidation in skeletal muscle                            1.0         ...
Relation between experimental and computational models to   optimal design experiments and generate hypotheses
Integrative Systems Biology Approach  Aim  Support the iterative process in defining   alternative hypotheses, and designi...
ConclusionPhysiological-based models of a complex system can       Integrate knowledge about components       Incorporate ...
Projects & SponsorsAgency: NASA, National Aeronautics and Space AdministrationProject: Time Course of Metabolic Adaptation...
Upcoming SlideShare
Loading in …5
×

Un approccio integrato della biologia dei sistemi per studiare il trasporto di ossigeno e il metabolismo ossidativo del sistema muscolo-scheletrico in condizioni fisiologiche e patofisiologiche

669 views
519 views

Published on

Nicola Lai
@CRS4 Seminar Series 2011

Published in: Technology, Health & Medicine
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
669
On SlideShare
0
From Embeds
0
Number of Embeds
3
Actions
Shares
0
Downloads
4
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

Un approccio integrato della biologia dei sistemi per studiare il trasporto di ossigeno e il metabolismo ossidativo del sistema muscolo-scheletrico in condizioni fisiologiche e patofisiologiche

  1. 1. A Systems Biology ApproachTo Study Metabolic Regulation In Tissue/Organ Systems In Health And Disease States Nicola Lai Department of Biomedical Engineering Case Western Reserve University Dicembre 21, 2011
  2. 2. Outline of PresentationIntroduction to Systems BiologyProjectsExperimental approaches to study energymetabolism at different whole body levels: Cellular Tissue-Organ Whole BodyIntegration of experimental data to computationalmodel to study O2 transport and metabolism in skeletal muscle (Diabetes) Fuel Homeostasis: Substrate Utilization (Cystic Fibrosis)Relation between experimental and computationalmodels for optimal design of experiments and togenerate hypotheses
  3. 3. Systems BiologyStudy of the interactions between the components ofbiological systems, and how these interactions giverise to the function and behavior of that system (e.g.,the enzymes and metabolites in a metabolic pathway) Organisms Organs Tissues Integrative Discover Functional Systems Biology Properties of the Cells Approach Biological Systems Proteins Genes
  4. 4. Systems Approach: IntegrationComprehensive data sets from distinct levels ofbiological systems;It is difficult to relate organ whole-organismfunction to cellular and sub-cellular function andstructure properties;Integration of multi-scale data to build predictivemathematical models of the system;Investigate the behavior and relationships of allelements in a functioning biological system;
  5. 5. Cellular MetabolismAll the chemical processes that make it possible forthe cells to continue living Cell
  6. 6. Metabolic SystemsMost metabolic pathways have beenintensely studied;Little is known in quantitative terms abouttheir control and integration with otherpathways, as well as their interaction toregulate physiological variables (e.g., blood,glucose, muscle ATP) under normal andstress conditions; Fell D. Understanding the Control of Metabolism, 1997.
  7. 7. Ongoing Research ProjectsTitleSystems Biology Investigation of Muscle Exercise Metabolism in DiabetesGoalTo quantify the key factors responsible for metabolic and mitochondrialdysfunction in diabetes and elucidate the impact of exercise training onenergy metabolism Agency National Institute of Arthritis, Musculoskeletal & Skin DiseasesTitleSystems Biology Approach to Growth Regulation in Cystic FibrosisGoalTo investigate the patterns of energy homeostasis (energy utilization andimbalances) in control and cystic fibrosis (CF) mice using perturbationsincluding pharmacologic treatment, genetic manipulations and alteringenergy balance by diet or exercise Agency Institute of General Medical Sciences
  8. 8. Systems Biology Approach1. 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
  9. 9. 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 defined The altered metabolic regulation under which insulin is less effective in inducing glucose utilization is not completely understood
  10. 10. Why study exercise metabolismMuscle energy metabolism in healthy & diseasestateDetect and prevent pathologies (e.g. Diabetes)Therapeutic intervention to ameliorate quality oflife in elderly and subjects with metabolicdisorders
  11. 11. Experimental Approach -ExerciseAcute Perturbation / Stimuli -Hypoxia, HyperoxiaChronic Stimuli / Conditions -Drugs -Training, Microgravity -Diseases (e.g. Diabetes, Myopathies) Biological Systems -Physiological variables (e.g. Blood flow) -Metabolic variables (e.g. Substrates, Enzymes) System Outputs
  12. 12. Whole body response to exercise Stimulus Response Physiological Process
  13. 13. Exercise Protocol WR [watt]Range (80-200)Warm up (20) Time [min] NT E E IV ERY T UP A T T A VE RY S RES M NS K R TI VE AS OV AR CO OR AC CO P C W RE RE W
  14. 14. Physiological responses to exercise 1.50 Indirect Calorimetry 1.25 Pulmonary 1.00 VO2 [L min ] O2 Uptake -1 0.75 0.50 Bioimpedance Cardiography 0.25 Cardiac 0.00 0 50 100 150 200 250 300 350 400 450 500 Output [second] 30 12.5 25 NIR 10.0 Spectroscopy 20 7.5Cdeoxy [mM] Q [L min ] Muscle -1 15 Oxygenation 5.0 10 2.5 5 0 0.0 0 50 100 150 200 250 300 350 400 450 500 0 50 100 150 200 250 300 350 400 450 500 [second] [second]
  15. 15. Characterization of the physiological variable response to stimulusMathematical Modelt ≤ t0 +TD Y( t ) = YBLt > t0 +TD Y( t ) = YBL + A (1 − e( t0 +TD − t )/ τ ) Rest StimuliParameters YBL + A A, Amplitude τ, Time Constant A TD, Delay Time YBL TD t0 t, Time [min]
  16. 16. τ Effect of time constant (τ) on the physiological response 1.8 τ=30s τ= 1.5 τ=30s τ= τ=90s τ=VO2 [L min ] 1.2-1 0.9 0.6 0.3 0 100 200 300 400 500 600 700 [second]
  17. 17. VO2 Responses to Exercise in Human Subjects: Type II Diabetes Mellitus (T2DM) & Health (Control) T2DM CONTROL Time [s] PAD Time [s] Impaired cardiac responses to exercise Alteration O2 diffusion and/or utilization in skeletal muscle is also possibleRegensteiner et al. 1998, Journal of Applied Physiology
  18. 18. VO2 Responses to Exercise in Human Subjects: Cystic Fibrosis (CF) & Health (Control) Control CF Time [s] Time [s] Dynamic response of pulmonary O2 uptake (VO2) in humans during exercise slower with CF than healthy VO2 response can be affected by pulmonary impairment but peripheral factors (O2 transport and metabolism) may also play a roleHebestreit et al., 2005
  19. 19. Effect of Exercise on VO2 response to exercise in T2DM patients Control τ=40s τ= T2DM τ=72s τ=Bradenburg et al., Diabetes Care 22, p1640–1646, 1999
  20. 20. Linking Cell, Tissue/Organ systems & Whole BodyWhole Body Cell Tissue/Organ Systems
  21. 21. Whole body & tissue-organ responses to exerciseStimulus Response LUNGS LUNGS Pulmonary Pulmonary Physiological O2 Uptake O2 Uptake Process HEART HEART Cardiac Output Cardiac Output Arterio/venous Arterio/venous difference difference SKELETAL MUSCLE SKELETAL MUSCLE -Blood O2 Saturation -Blood O2 Saturation -Tissue O2 -Tissue O2 Saturation Saturation -Muscle Blood Flow -Muscle Blood Flow
  22. 22. Measurements of Muscle Blood Flow (Q), Arterial and Venous O2 concentrations Catheter Radial Artery Cart,O 2 Catheter Femoral Vein Cven,O 2 Muscle O2 Uptake VO2m=Q (Cart,O2-Cven,O2)MEASUREMENTS Blood Samples: Arterial and venous O2 concentration (Cart,O2, Cven,O2) by Oximeter Tissue Biopsies: Metabolite concentrations by GS, MS Muscle Blood Flow (Q) by thermo-dilution technique
  23. 23. Cardio-respiratory & skeletal muscle responses to exercise VO2A , Alveolar Oxygen Uptake Qleg, Muscle Blood Flow, Ca-Cv, Arterio-Venous diff. VO2leg, Muscle Oxygen UptakeGrassi et al., JAP (1996) 80, p988-998
  24. 24. Linking Cell, Tissue/Organ systems & Whole BodyWhole Body Cell Tissue/Organ Systems
  25. 25. Mitochondrial respiration responses to different substrates Stimulus Response Substrates BufferPolarographic Solution System Water Water 30°C 30°C Oxygen ∆V consumption Rate Magnetic Electrode System stir bar Magnetic mixer
  26. 26. Oxidative phosphorylation rate in healthy and disease statesFunctional defectsin dehydrogenase activitiesThe mitochondria of patient ‘C’Pyruvate oxidation is impairedDefect in the pyruvate dehydrogenasecomplexThe mitochondria of patient ‘D’Glutamate and succinate oxidation areimpairedDefect in fumarase activityPuchowicz et al., 377–385 , 2004
  27. 27. Dynamic response of O2 utilization at different whole body levels Biological Systems Time constant Cell 2.5 sSkeletal Muscle 25÷30 s Whole Body 30÷35 s
  28. 28. Factors affecting bioenergetics function Central Cardiovascular and respiratory systems Ventilation; O2 Diffusion from Alveoli to pulmonary capillary Cardiac Output; Peripheral Skeletal Muscle systems O2 Diffusion from muscle capillary to myocytes Metabolic processes (Cytosol, mitochondria)
  29. 29. Linking Cell, Tissue/Organ systems & Whole Body Whole Body Tissue/Organ Systems Cell
  30. 30. Cellular Energy metabolism
  31. 31. Multi-compartmental System Model Capillary Blood Q Ca,j Q Cv,j Cb,j Interstitial Fluid Jb↔c,j Cisf,j ↔Specie j Specie j transport rateCa,j: Arterial concentration Cc,j | Rc,j from blood to cytosol, Jb↔c,jCv,j: Venous concentration from cytosol to mitochondria, Jc↔m,j Pc,j Uc,jCb,j: Capillary blood concentration Cytosol Jc↔m,j ↔ Species j reaction rateCisf,j: Interstitial fluid concentration Rc,j=Pc,j – Uc,j cytosolCc,j: Cytosolic concentration Cm,j | Rm,j Rm,j=Pm,j – Um,j mitochondriaCm,j: Mitochondrial concentration Pm,j Um,j Mitochondria Px,j =∑p βx,j,p φx,p φ Reaction flux Ux,j = ∑u βx,j,u φx,u β Stoichiometric coefficient
  32. 32. Dynamic Mass Balance Equations ( ) dCb, j Blood (b): Vb = Q Ca, j − Cb, j − J b↔ c, j dt dCc, j Cytosol (c): Vc = ∑ β c, j, pφ c, p − ∑ β c, j,uφ c,u + J b↔ c, j − J c ↔ m, j dt p u dCm, j Mitochondria (m): Vm = ∑ β m, j, pφ m, p − ∑ β m, j,uφ m,u + J c ↔ m, j dt p uQ: Muscle blood flowCx,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 ↔φp, φu: Metabolic reaction fluxes: production or utilizationβp, βu: Stoichiometric coefficients.
  33. 33. Metabolic Reaction FluxesReactionA+ B C+DOrdered bi-bi Michaelis-Menten kinetics Vmax,f [ A][ B ] Vmax,r [ P ][Q] − K a Kb K p Kqφ= [ A] [ B ] [ A][ B ] [ P] [Q] [ P][Q] 1+ + + + + + K a Kb K a Kb K p K q K p K qHaldane Relation Metabolic Parameters Vmax, f K p K qVmax,r = K eq , K a , Kb , K p , K q K a K b K eq
  34. 34. Inter-domain Transport FluxesTransport ProcessesBlood-Cytosol (b↔c ) Cytosol-Mitochondria (c↔m )b↔c,p: Ala, Glr, CO2, O2, H+ c↔m,p: CO2 and O2b↔c,f: Glc, Pyr, Lac, FFA c↔m,f: Pyr, FAC, Pi, CoA, H+, Cit, Mal PASSIVE Jxp↔y, j = λx↔y, j (Cx, j −Cy, j )       Jx↔y, j =  FACILITATED  J f = T  Cx, j Cy, j  −  x↔y, j x↔y, j  Mx↔y, j + Cx, j Mx↔y,, j + Cy, j      
  35. 35. Whole body model O2 Transport between Lungs & Skeletal muscle Dynamic balance of O2 in Lungs Alveoli LUNGS V dCAO2 LbVA(t), C IO2 Alveolar Space VO2p CAO2 VA = VA( t )( CI O2 − CAO2 ) − ∫ JA ↔ LO2 ,b dv & dt 0 Capillary VO2A Cven Cart Lung Capillary Blood Q(t) ∂CLO2 ,b ∂CLO2 ,b ∂ 2 CLO2 ,b OTHER ORGANS organs = −Q +D + JA ↔ LO2 ,b 0 < v < VLb ∂t ∂v ∂v 2 Tissue Qo Capillary Other Organs Tissue VRb dCRO2 ,c =− ∫J R ↔ RO2 ,b dv + MRO2 MUSCLE Qm(t) VR Tissue UO2m dt 0 Cven,m Cart,m Blood 0 < v < VR ,b Capillary VO2m ∂CRO2 ,b ∂CRO2 ,b ∂ CRO2 ,b 2 = −Q0 + DR + JR ↔ RO2 ,b ∂t ∂v ∂v 2 Arterial & Venous Systems O2 Diffusion ∂CrO2 ∂CrO2 ∂ 2 CrO2 JR ↔ RO ,b = PS R ( PRO2 ,b − PRO2 ,c ) = −Q + Dr ; 0 < v < Vr 2 ∂t ∂v ∂v 2 JA ↔ LO2 ,b = PS L ( PAO2 − PLO2 ,b )
  36. 36. Model Prediction of metabolic processes at cellular level: Cytosol and Mitochondria Response to Exercise Variations in Glycogen concentration Under pathological conditions or with special diet, glycogen stores in skeletal muscle at rest can differ significantlyLi et al., AJPEM 298, p1198-1209, 2010
  37. 37. Model Prediction of metabolic processes at whole skeletal muscle 120 Muscle Q [mL 100g min ] Effect of blood flow -1 100 Blood Flow 80 Model Simulation on VO2m response -1 Exp.Data - Normoxia 60 40 Self Perfused (SP) Model Simulation to contraction Exp.Data - Normoxia 20 Pump Perfused (PP) Catheter 0 Radial Artery 18Arterio-Venous 16 Cart,O2 14 Difference VO 2 [mLO 2 100g min ] CA-V [vol %] 12 Model Prediction 10 Exp.Data - Normoxia 8 Self Perfused (SP) 6 Model Prediction Catheter 4 Exp.Data - Normoxia Femoral Vein T 2 Pump Perfused (PP) 0 Cven,O2 -1 18 Muscle O2 16 14 Uptake -1 12 Model Prediction 10 Exp.Data - Normoxia 8 Self Perfused (SP) 6 Model Prediction 4 Exp.Data - Normoxia *Grassi et al., 2000 2 Pump Perfused (PP) JAP. 89: 1293-1301 0 0 30 60 90 120 150 180 210 240 270 300 Spires et al., 2011 Time [s] JAP. Submitted
  38. 38. Model Prediction of metabolic processes at whole body level 0.2 Dynamic responses of Muscle 0.1 O2 saturation & Pulmonary O2 uptake to exercise 0.0 LUNGS LUNGS∆StO2m/StO2mw -0.1 Pulmonary Pulmonary -0.2 O2 Uptake O2 Uptake -0.3 Model Simulation Experimental Data -0.4 HEART HEART 2.5 Cardiac Cardiac 2.0 Output Output VO2p [L O2/min] 1.5 1.0 MUSCLE MUSCLE 0.5 Model Simulation Experimental data Oxygen Oxygen 0.0 Saturation Saturation -1 0 1 2 3 4 Time [min]
  39. 39. Factors affecting bioenergetics function Central Cardiovascular and respiratory systems Ventilation; O2 Diffusion from Alveoli to pulmonary capillary Cardiac Output; Peripheral Skeletal Muscle systems O2 Diffusion from muscle capillary to myocytes Metabolic processes (Cytosol, mitochondria)
  40. 40. Mathematical Modeling and Analysis: Hypotheses of cellular and physiological regulation Inputs: Outputs: MathematicalExperimental Metabolic Model Conditions Responses Hyp.1 Hypotheses Hyp.2 Hyp.1: Impairment of cellular transport (e.g. facilitate diffusion) Hyp.2: Activation/Inhibition of enzymatic Hyp.3 reactions and/or metabolic pathway Hyp.3: Impairment of substrate delivery (e.g., reduced blood flow)
  41. 41. Cystic Fibrosis: Genetic Complex Disorder Cystic Fibrosis is a complex, systemic, and multi-organ disorder Although CFTR gene is identified, many aspects of CF cannot be related directly to chloride channel defect Are pulmonary infection, inflammation, and growth retardation primary effects or secondary consequences? A Systems Approach is Needed !
  42. 42. Energy Homeostasis in CFEnergy Supply Intake of FAT, CHO, and protein Digestion and absorption of nutrientsEnergy Utilization Oxidation of FAT, CHO and Protein Leaks: lower efficiency, cachexia Total energy expenditureEnergy Balance Body composition Insulin
  43. 43. Hormonal and Metabolic Characteristics of Tissues in CFSkeletal Muscle Lower work efficiency and inorganic phosphorus-to- phosphocreatine ratio during exercise Dysfunction of aerobic and anaerobic metabolismLiver Impaired suppression of hepatic glucose production and non-oxidative glucose metabolism stimulated by insulin De novo lipogenesis related to carbohydrate utilizationAdipose Tissue Plasma palmitate 50% higher in human CF than control during insulin infusion Impaired suppression of adipose tissue lipolysis by insulin
  44. 44. System Model: Whole-Body & Organ-Tissues Gas Exchange O2 CO2 Brain Heart Exercise Skeletal Muscle Liver Insulin GlucagonOrgan system is connected via GIblood carrying substrates AdiposeCarbohydrates and fat utilizationduring exercise OthersHormonal activation/inhibition ofmetabolic pathways
  45. 45. Multi-compartmental System Model Capillary Blood Q Ca,j Q Cv,j Cb,j Interstitial Fluid Jb↔c,j Cisf,j ↔Specie j Specie j transport rateCa,j: Arterial concentration Cc,j | Rc,j from blood to cytosol, Jb↔c,jCv,j: Venous concentration from cytosol to mitochondria, Jc↔m,j Pc,j Uc,jCb,j: Capillary blood concentration Cytosol Jc↔m,j ↔ Species j reaction rateCisf,j: Interstitial fluid concentration Rc,j=Pc,j – Uc,j cytosolCc,j: Cytosolic concentration Cm,j | Rm,j Rm,j=Pm,j – Um,j mitochondriaCm,j: Mitochondrial concentration Pm,j Um,j Mitochondria Px,j =∑p βx,j,p φx,p φ Reaction flux Ux,j = ∑u βx,j,u φx,u β Stoichiometric coefficient
  46. 46. Dynamic Mass Balance Equations ( ) dCb, j Blood (b): Vb = Q Ca, j − Cb, j − J b↔ c, j dt dCc, j Cytosol (c): Vc = ∑ β c, j, pφ c, p − ∑ β c, j,uφ c,u + J b↔ c, j − J c ↔ m, j dt p u dCm, j Mitochondria (m): Vm = ∑ β m, j, pφ m, p − ∑ β m, j,uφ m,u + J c ↔ m, j dt p uQ: Muscle blood flowCx,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 ↔φp, φu: Metabolic reaction fluxes: production or utilizationβp, βu: Stoichiometric coefficients.
  47. 47. Metabolic Pathways in Adipose Tissue Lactate Pyruvate Alanine CO2 CO2 CoA LAC PYR ALA NADH CoA CO2 PYR ATP NADH NAD+ NADH NAD+ ATP CoA NADP+ NADPH ADP+Pi ADP+Pi NAD+ NADH ATP Proteins FA ACoA NADH NAD+ GAP2 NAD+ ADP+Pi ATP NADH NADH ADP+Pi CoA NAD+ CoA NAD+ GAP1 G3P1 FAC ATP GLR G3P2 ADP NADH NAD+ ADP+Pi FAC ATP ADP FAC CoA Pi CoA ATP Pi CoA DG TG DG F6P R5P GLR CO2 DG MG FAC NADPH ADP+2Pi ATP FAATGL MG NADP+ HSL DG GLY G6P ADP+Pi ATP GLR Pi ADP O2 H2O HSL NADH NAD+ FA MG ATP MG GLR GLC ATP ADP MGL HSL Tissue FA Glucose O2 FFA Blood VLDL-TG Glycerol + Epinephrine Insulin Work Rate
  48. 48. Tissue Specific Metabolic Pathways Pathways Brain Heart Muscle GI Liver1. Glucose Utilization: GLC + ATP ⇒ G6P + ADP2. G6P Breakdown: G6P + ATP ⇒ 2GA3P + ADP3. GA3P Breakdown:GA3P + Pi + 2ADP + NAD+⇒ PYR + 2ATP + NADH4. Gluconeogenesis-1: PYR + 3ATP + NADH ⇒ GAP + 3ADP + Pi + NAD+5. Gluconeogenesis-2: 2GA3P ⇒ G6P + Pi6. Gluconeogenesis-3: G6P ⇒ GLC + Pi7. Glycogenesis: G6P + ATP ⇒ GLY + ADP + 2Pi8. Glycogenolysis: GLY + Pi ⇒ G6P9. Pyruvate Reduction: PYR + NADH ⇒ LAC + NAD10. Lactate Oxidation: LAC + NAD ⇒ PYR + NADH11. Glycerol Phosphorylation: GLR + ATP ⇒ G3P + ADP12. GA3P Reduction: GA3P + NADH ⇒ G3P + NAD13. Glycerol-3-P Oxidation: G3P + NAD ⇒ GA3P + NADH14. Alanine Formation: PYR ⇒ ALA15. Alanine Conversion: ALA ⇒ PYR16. Pyruvate Oxidation: PYR + CoA + NAD ⇒ ACoA + NADH + CO217. Palmitate Oxidation: FA+8CoA+14NAD+2ATP ⇒ 8ACoA+14NADH+2ADP+2Pi18. Palmitate Synthesis: 8ACoA + 7ATP + 14NADH ⇒ FA + 8CoA + 7ADP + 7Pi + 14NAD19. Lypolysis: TG ⇒ 3FA + GLR20. Triglyceride Production: 3FA + G3P + 6ATP ⇒ TG + 6ADP + 6Pi21. TCA Cycle: ACoA + 4NAD + ADP + Pi ⇒ 4NADH + CoA + ATP +2CO222. Oxygen Consumption: 2NADH + 6ADP + 6Pi + O2 ⇒ 2NAD + 6ATP23. Phosphocreatine Breakdown: PCR + ADP ⇒ CR + ATP24. Phosphocreatine Synthesis: CR + ATP ⇒ PCR + ADP25. ATP Hydrolysis: ATP ⇒ ADP + Pi + Energy
  49. 49. Skeletal Muscle/Adipose Tissue Interactions CO2 LPL LAC PYR ALA GLR VLDL-TG FFA NAD+ NADH + Proteins CO2 LAC PYR ALA NADH CoA CoA – ATP ATP CO2 ATP NADH NAD+ ADP+Pi ADP+Pi – NAD+ ADP+Pi NAD+ CoA NADH – ADP GAP1 NADH GAP2 NADH NAD+ NADH ACoA NADH NAD+ CoA NAD+ NAD+ ATP ATP ADP+Pi F6P R5P G3P1 G3P2 FAC FA CO2 CoA NADH ADP+Pi ATP + GLR NADP+ CoA MGL + Pi ATGL HSL CoA Pi G6P GLY HSL HSL ADP+Pi DG TG DG MG ADP ATP ADP+2Pi – – ATP MG DG GLR MG GLR MG ATP GLC ADP+Pi ATP Pi O2 H2 O ATP ADP NADH NAD+ Tissue Blood GLC O2 LAC PYR ALA GLR FFA CO2 NAD+ NADH CO2 LAC PYR ALA NADH CoA NAD+ NADH CO2 PYR NAD+ ATP NADH ATP ATP ADP NAD NADH CoA ATP ADP+Pi ADP NAD+ ADP+Pi GLR FA ACoA NAD+ NADH CoA GAP G3P ATP ADP ATP ADP ADP PCR CR Pi ATP ADP ADP+2Pi ATP ATP GLY G6P TG ATP ADP Pi ADP ATP ADP+Pi ATP GLC O2 H2 O Tissue NADH NAD+ Blood GLC TG O2
  50. 50. Experimental protocol and measurements WR PROTOCOL MEASUREMENTS [watt] Blood 100 Hormones: Insulin; Norepinephrine 60 minute 50 Epinephrine Growth Hormon (GH) Substrates: Lactate T Glycerol T UP ES M T AN TE Time Glucose R NS RA AR W CO RK [min] Nonesterified Fatty Acid WO Tissue Exercise maximal test; Substrates: Exercise at moderate work rate (WR) Dialysate Glycerol equivalent to 50% of VO2peakKoppo et al., 2010
  51. 51. Hormone responses to exercise 450 35 400 Model simulation 30 350 Experimental Data 300 25 Epinephrine [pm] Hormone [pm] 250 20 200 15 Glucagon 150 Model Simulation 100 10 Experimental Data Insulin 50 Model Simulation 5 0 Experimental Data -50 0 -10 0 10 20 30 40 50 60 70 80 -10 0 10 20 30 40 50 60 70 80 Time [min] Time [min]Koppo et al., 2010
  52. 52. Glucose Homeostasis During Exercise 6000 2000 1800 5000 Glucose 1600 Utilization Rate [µmol/min] Production Glucose [µmmol/min] 1400 4000 1200 3000 1000 800 2000 Model Simulation 600 Experimental Data 400 1000 200 0 0 -10 0 10 20 30 40 50 60 70 80 -10 0 10 20 30 40 50 60 70 80 Time [min] Time [min]Koppo et al., 2010
  53. 53. Plasma Metabolite Responses to Exercise 1.4 3.0 Model Simulation Experimental Data 2.5 1.2 Lactate, LAC/LAC0 [-] Fatty Acid, FA/FA0 [-] 2.0 1.0 1.5 1.0 0.8 0.5 Model Simulation Experimental Data 0.6 0.0 -10 0 10 20 30 40 50 60 70 80 -10 0 10 20 30 40 50 60 70 80 Time [min] Time [min]Koppo et al., 2010
  54. 54. Glycerol Responses to Exercise Plasma Adipose Tissue 3.5 3.5 3.0 3.0 Model Simulation Glycerol, GLC/GLC0 [-] Glycerol, GLC/GLC0 [-] 2.5 2.5 Experimental Data 2.0 2.0 1.5 1.5 1.0 1.0 Model Simulation 0.5 Experimental Data 0.5 0.0 0.0 -10 0 10 20 30 40 50 60 70 80 -10 0 10 20 30 40 50 60 70 80 Time [min] Time [min]Koppo et al., 2010
  55. 55. Hypothesis: Fatty Acid Oxidation Impaired in Skeletal 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 muscle Lipolysis inhibited via lactate or high catecholamine concentration
  56. 56. Effect of Adipose Tissue Blood Flow on Fatty Acid oxidation in skeletal muscle 1.0 Fatty Acid (FA) Release of Adipose Tissue (AT) 0.9 FA Oxidation of Skeletal Muscle (SM) Lipolysis 0.8 FA Uptake 0.7 SM SM SM SM SM Rate [mmol/min] AT AT AT AT 0.6 0.5 0.4 AT 0.3 0.2 AT SM 0.1 0.0 Rest 10% 30% 50% 100% 150% Exercise**Horizontal axis: ATBF/ATBF0 adipose tissue blood flow at steady-statemoderate exercise relative to basal physiological value
  57. 57. Relation between experimental and computational models to optimal design experiments and generate hypotheses
  58. 58. Integrative Systems Biology Approach Aim Support the iterative process in defining alternative hypotheses, and designing optimum experiments Impact Design of experimental protocols for specific evaluation of disease and improved treatments based on simulations with experimentally validated mechanistic models
  59. 59. ConclusionPhysiological-based models of a complex system can Integrate knowledge about components Incorporate interactions of system elements Facilitate quantitative understanding of functionHierarchical multilevel models provide means For testing hypotheses For predicting critical experiments
  60. 60. Projects & SponsorsAgency: NASA, National Aeronautics and Space AdministrationProject: Time Course of Metabolic Adaptation during Loading & UnloadingAgency: NSF, National Science FoundationProject: Database-enabled tools for Regulatory Metabolic NetworksAgency: NIDDK, National Institute of Diabetes and Digestive & Kidney DiseasesProject: Systems Biology Approach to Growth Regulation in Cystic FibrosisAgency: 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 approachAgency: NIGMS - National Institute of General Medical SciencesProject: Center for Modeling Integrated Metabolic Systems

×