Diabetes and Exercise: Why Exercise Works When Insulin Does Not

Diabetes and Exercise:Why Exercise Works When Insulin Does NotLaurie J. GoodyearMetabolism SectionJoslin Diabetes CenterHarvard Medical School

Type 2 Diabetes is Reaching Epidemic Levels A major factor leading to increased rates of type 2diabetes is inactivity. Physical exercise is critical in the prevention of type2 diabetes.

Diabetes and Exercise:Why Exercise Works When Insulin Does Not Background on Diabetes Skeletal Muscle Glucose Transport Studies in Human Subjects “The Exercise Pill”

Basic Physiology: Glucose concentrations in theblood rise after a meal. Insulin is released fromthe pancreas, binding to insulin receptors ontissues throughout the body, resulting in glucoseentering the tissues.MuscleLiverPancreasFat

Type 1 Diabetes(juvenile-onset or insulin-dependent)Pancreas loses its ability to produce and secrete insulin.This is almost always caused by autoimmune attack anddestruction of the β cells.MuscleLiverPancreasFat

Type 2 diabetes(adult-onset or non-insulin dependent)Insulin is produced by the pancreas and levels in theblood are often normal or even high, but the tissuesdon’t respond - insulin resistance.MuscleLiverFatPancreas

Diabetes Complications Leading cause of blindness Leading cause of kidney failure Leading cause of amputations Major cause of heart attacks Major cause of strokes

Diabetes is Reaching Epidemic Levels2000 = 14.22010 = 17.523%9.414.150%26.532.924%84.5132.357%Zimmet et alWHO Data15.622.544%World2000 = 151 million2010 = 221 million2020 = 300 million1.01.333%

Type 2 Diabetes is Reaching Epidemic LevelsCumulative incidence (%)403020100Incidence of Diabetes (DPP)(Risk reduction31% by metforminPlacebo58% by lifestyle Metformin0 1 2 3 4Years from randomizationLifestyle

Diabetes and Exercise:Why Exercise Works When Insulin Does Not Background on Diabetes Skeletal Muscle Glucose Transport Studies in Human Subjects “The Exercise Pill”

Effect of Exercise on Blood Glucose Concentrationsin a Subject with Type 2 Diabetesglucose (mM)9876543210basalExercise at 70% VO 2 max5 10 20 45 75(minutes)

Type 2 DiabetesBlood VesselGlucoseExerciseMuscle

Blood VesselGlucoseInsulinMuscle

Type 2 DiabetesBlood VesselGlucoseXInsulinMuscle

Skeletal Muscle Glucose UptakeType 2 DiabetesExercise+Insulin What is the molecular basis for the ability ofexercise to increase glucose uptake in skeletalmuscle of patients with Type 2 diabetes?

Methods to Study Exercise and Muscle ContractionMuscle contractionsystem for culturedmyotubesContraction bydirect electricalstimulationContraction bysciatic and peronealnerve stimulationTreadmill running exercise(acute and chronic studies)Wheel running exercise(chronic studies)Human exercisewith biopsies

Glucose Transport System in Skeletal Muscleglucose glucose transport is the ratelimiting step in glucose utilization facilitated diffusion glucose transporter proteinsP GLUT1, GLUT4 expressed inskeletal muscleGLYCOGENGLYCOLYSIS exercise, insulin most potentphysiological stimuli

Under Basal Conditions GLUT4 isPrimarily Intracellularsurface membraneGLUT4-containing vesicle

Exercise Regulation of Glucose TransportExerciseGLUT4-containing vesicle

Exercise Regulation of Glucose TransportGlucoseExerciseGLUT4 Translocation

Insulin Regulation of Glucose TransportInsulinReceptorGlucoseExerciseGLUT4 Translocation

Insulin Stimulates GLUT4 Translocationin Skeletal MuscleIn vivo imaging of GLUT4-GFPt=0 t=30Mouse quadriceps muscleBar = 20 µm(Lauritzen HPMM, Diabetes, 2006)

Contraction Stimulates GLUT4 Translocationin Skeletal MuscleIn vivo imaging of GLUT4-GFPt=0 t=15Mouse quadriceps muscleBar = 20 µm

Are there distinct mechanisms for insulinandexercise-stimulated glucose transport?InsulinReceptorGlucoseExerciseGLUT4 Translocation

Contraction + Insulin have Additive Effectson Glucose Transport in Skeletal Muscle1210Glucose TransportArbitrary units86420basalmaximalcontractionmaximalinsulincontraction+ insulin

Exercise and Insulin Regulate GlucoseTransport via Distinct Signaling MechanismsInsulinReceptorGlucoseExerciseGLUT4 Translocation

What are the signaling mechanisms thatmediate glucose transport in skeletal muscle?InsulinReceptorGlucoseExercise??GLUT4 Translocation

Insulin Regulation of Glucose TransportInsulinReceptorGlucosePPPPPExercisePIRS-1Pp85-p110PI 3-KinaseAktGLUT4 Translocation

Exercise and Insulin Regulate GlucoseTransport via Distinct Signaling MechanismsInsulinReceptorGlucosePPPPPExercisePIRS-1Pp85-p110PI 3-KinaseAktGLUT4 Translocation

Exercise and Insulin Regulate GlucoseTransport via Distinct Signaling MechanismsInsulinReceptorGlucosePPPPPExercisePIRS-1Pp85-p110PI 3-KinaseAktGLUT4 Translocation?

Exercise and Insulin Regulate GlucoseTransport via Distinct Signaling MechanismsInsulinReceptorGlucosePPPPPExercisePIRS-1Pp85-p110PI 3-KinaseAktGLUT4 TranslocationAMPK

5’AMP-Activated Protein Kinase (AMPK)βαγα1, α2 (α2 predominant in skeletal muscle)β1, β2γ1, γ2, γ3• A member of metabolite-sensing protein kinase family• Activated under conditions of low energy state, exercise• Proposed to regulate numerous metabolic andtranscriptional processes in multiple cell types

5’AMP-Activated Protein Kinase (AMPK)Activating T-loop phosphorylation siteαAMPγβ

5’AMP-Activated Protein Kinase (AMPK)LKB1αAMP

What is the evidence that AMPK mediatesexercise-stimulated glucose transport?InsulinReceptorGlucosePPPPPExercisePIRS-1Pp85-p110PI 3-KinaseAktGLUT4 TranslocationAMPK

ACIAR and the Regulation of GlucoseTransport in Skeletal MuscleGlucoseInsulinReceptorAICARPPPPPPIRS-1Pp85-p110PI 3-KinaseAktGLUT4 TranslocationAMPK

NH2COCCH2NNCHNOHOHHOHHHCH2OOOOP--NH2COCCNNCHNOHOHHOHHHCH2OOOOP--HCZMPAMPAICAR(5-aminoimidazole-4-carboxamide-riboside)AICARZMPαβγAMPKKPAMPK ActivityAdenosine kinase

AICAR + Insulin have Additive Effects onGlucose Transport in Skeletal Muscle1210Glucose TransportArbitrary units86420basalmaximalAICARmaximalinsulinAICAR+ insulin

AICAR + Contraction do not have AdditiveEffects on Glucose Transport1210Glucose TransportArbitrary units86420basalmaximalAICARmaximalcontractionAICAR +contraction

ACIAR and Insulin Regulate GlucoseTransport via Distinct Signaling MechanismsGlucoseInsulinReceptorAICARPPPPPExercisePIRS-1Pp85-p110PI 3-KinaseAktGLUT4 TranslocationAMPK

SummarySkeletal Muscle Glucose Transport Exercise and insulin increase glucose transport in skeletal muscle, resulting in glucose clearance from the blood. Exercise and insulin increase glucose transport through the translocation of GLUT4 transporters to the cell surface and transverse tubules in skeletal muscle. There are distinct proximal signaling mechanisms for exercise- and insulin-stimulated GLUT4 translocation. AICAR increases AMPK activity and can increase glucose transport in skeletal muscle.

Diabetes and Exercise:Why Exercise Works When Insulin Does Not Background on Diabetes Skeletal Muscle Glucose Transport Studies in Human Subjects “The Exercise Pill”

What is the physiological relevance of thesefindings for patients with type 2 diabetes?

Skeletal Muscle from Patients with Type 2 DiabetesExercise+InsulinDoes exercise bypass defects in insulinaction in skeletal muscle by utilizingalternative signaling mechanisms leading toincreased GLUT4 translocation?

Skeletal Muscle Biopsy from Human Subjects

Are there defects in insulin- and exercisestimulatedGLUT4 translocation in patientswith type 2 diabetes?InsulinReceptorGlucoseExerciseGLUT4 Translocation

Insulin-stimulated GLUT4 Translocation isImpaired in Patients with Type 2 Diabetes100Arbitrary units7550250Basal Insulin Basal InsulinControlsType 2 DM

Exercise Causes Normal GLUT4 Translocationin Subjects with Type 2 Diabetes100Arbitrary units7550250Basal ExerciseControlsBasal ExerciseType 2 DM

Exercise and Insulin Regulate GlucoseTransport via Distinct Signaling MechanismsInsulinReceptorGlucosePPPPPExercisePIRS-1Pp85-p110PI 3-KinaseAktGLUT4 Translocation

ACIAR and Insulin Regulate GlucoseTransport via Distinct Signaling MechanismsInsulinReceptorGlucosePPPPPExercisePIRS-1Pp85-p110PI 3-KinaseAktGLUT4 TranslocationAMPK

Exercise Increases AMPKα2 Activity InControls and Subjects with Type 2 Diabetes2.0*(pmol/mg/min)1.51.00.5** ***Type 2 DMControls0.0Exercise 70% VO 2max020 45 30’Restminutes

Exercise Can Bypass Defects in Insulin Signaling andGLUT4 Translocation in People with Type 2 DiabetesInsulinReceptorGlucosePPPPPExercisePIRS-1Pp85-p110PI 3-KinaseAktGLUT4 TranslocationAMPK

Can we make a drug to activate AMPK leading toincreased glucose transport in skeletal muscle?InsulinReceptorGlucosePPPPPDrug?PIRS-1Pp85-p110PI 3-KinaseAktGLUT4 TranslocationAMPK

Can we make a drug to activate AMPK leading toincreased glucose transport in skeletal muscle?InsulinReceptorGlucosePPPPPMetforminPIRS-1Pp85-p110PI 3-KinaseAktGLUT4 TranslocationAMPK

Metformin- Single most prescribed oral antidiabetic drug in the U.S.- Cellular mechanism of action is unclear* Suppresses hepatic glucose production* Increases muscle glucose uptake* Inhibits Complex 1 of Respiratory Chain(Owen, Biochem J, 2000 and El-Mir, JBC, 2000)

AICAR and Metformin Share Metabolic EffectsAICARMetformin Inhibit Hepatic Glucose Production Stimulate Muscle Glucose Uptake Increase Lactic Acid Production

Does the mechanism of Metformin actioninvolve the regulation of AMPK?InsulinReceptorGlucosePPPPPMetformin?PIRS-1Pp85-p110PI 3-KinaseAktGLUT4 TranslocationAMPK

Effect of Metformin on AMPK Activity(rat epitrochlearis muscles)(pmol/mg/min)1.61.41.21.00.80.60.40.2*0.0ControlMetformin3hr

Effects of 4 and 10 Weeks of MetforminTreatment on AMPKα2 Activity(human vastus lateralis muscle)0.80*(pmol/mg/min)0.600.400.20*0.00Basal 4 Weeks 10 Weeks

Activation of AMPK IncreasesSkeletal Muscle Glucose TransportInsulinReceptorGlucosePPPPPPIRS-1Pp85-p110PI 3-KinaseAktGLUT4 TranslocationAMPK

SummaryStudies in Human Subjects Exercise and insulin increase GLUT4 translocation in human skeletal muscle. Insulin signaling and GLUT4 translocation are impairedin patients with type 2 diabetes. Exercise-stimulated AMPK activation and GLUT4 translocation are normal in patients with type 2 diabetes. Activation of AMPK can increase glucose transport in skeletal muscle, making AMPK a drug target for treatmentof type 2 diabetes. Metformin, the most widely used diabetes drug, works through stimulation of AMPK.

Multiple Signals MediateExercise-Stimulated Glucose TransportExerciseCa2 + AMP/ATP ROS mechanicalLKB1GLUT4 TranslocationcalmodulinCaMKsSNARK ?AMPKNRGaPKCsPPPPP PCBDTBC1D1RABGAPdomainPPPPP PCBDAS160RABGAPdomain

Diabetes and Exercise:Why Exercise Works When Insulin Does Not Background on Diabetes Skeletal Muscle Glucose Transport Studies in Human Subjects “The Exercise Pill”

News Headlines, August 2008“It’s the exercise pill: the pill that helps you burn offcalories just by sitting on the couch. It’s America’sdream.”Couch Mouse to Mr. Mighty byPills AlonePill may boost endurance without exercise

The Exercise Pill: AICAR

VolumeOctober 23, 2008 Number 17359:1842-1844The Exercise Pill — Too Good to Be True?Laurie J. Goodyear, Ph.D.

Effects of AICAR Treatment andChronic AMPK ActivationAcute Effects:Blood Vessel Increase glucose uptake(Hayashi, Winder, others, 1998) Lower blood glucose levels(Shulman, others, 1999)GlucoseAICARChronic Effects: Increase exercise endurance(Witters, 2007) (Evans, 2008) Increase in muscle glycogen(Winder, Holloszy, others, 1999) Increase in GLUT4,mitochondrial enzymes (Winder,Holloszy, others, 1999)

The Exercise Pill — Too Good to Be True? AICAR has a short half-life after intravenous infusionand poor bioavailability after oral ingestion. AICAR treatment causes lactic acidosis in humans. AMPK activation in the hypothalamus can stimulateappetite. Activating mutations of AMPK cause heart conductionabnormalities in humans (WPW syndrome).

Benefits of Regular Physical ExercisePulmonary functionIncrease lung capacityImprove sleepIncrease blood volumeImprove pancreaticfunctionImprove liver functionReduce fat storesPrevention of DiabetesIncrease glucose toleranceIncrease insulin sensitivityIncrease muscle glucose uptakeIncrease mitochondrial functionDecrease depression, anxietyDecrease Alzheimer'sDecrease strokeDecrease appetiteImprove cardiac functionImprove lipid profileLower blood pressureIncrease bone densityIncrease muscle strengthIncrease flexibilityDecrease Rates of CancerColon, breast, endometrial

Joslin DiabetesCenterLongwood Medical Area, Boston

Ho-Jin KohNobuharu FujiiHans LauritzenJeff AnFritz KramerEric TaylorCarol WitczakJonas TreebakTaro ToyodaHaiyan YuCarrie SharoffMichelle JungKanokwan VichaiwongJan Willem MiddelbeekNiels JessenSarah LessardJulie RipleyMichael HirshmanHiroyasu Esumi(NCCRCR Institute East)Jianxin Xie(Cell Signaling)Jørgen WojtaszewskiEric Richter(U. Copenhagen)Funding Support:NIH (NIAMS, NIDDK)American Physiological SocietyAmerican Diabetes Association