Mechanisms for Cardiac Dysfunction in the Metabolic Syndrome E. Dale Abel MD, Ph.D., University of Utah [email protected]

No Disclosures

Metabolic Syndrome

Metabolic Syndrome

Obesity Facts • 2nd leading “preventable” cause of death (close behind tobacco use), est 300,000/yr • Cardiovascular disease, cancer, diabetes, OSA, arthritis, depression • Mortality most strongly associated with cardiovascular disease • Cost (in 1995 dollars) ~ $99.2 billion $51.6 billion direct / $47.6 billion indirect • 5.7% of total health care costs in 1995

Prevalence of Obesity in the United States

The Numbers Continue to Increase!

CDC: Centers for Disease Control and Prevention

An Evolutionary Biologists View of the Type 2 Diabetes and Obesity Epidemic

Dec 11th, 2003 The Economist

Cardiovascular Disease In Obesity and Diabetes • Major Cause of Mortality and Morbidity • Pathophysiology is Complex and Includes: • Increased Atherosclerosis and Coronary Artery Disease • Increased Hypertension, Hypercoagulability • Increased Heart Failure • Obesity Predisposes to Diabetes. Hyperglycemia has Deleterious Consequences in the Heart

Diabetes and Long-term Survival Following Acute MI

1,525 diabetics 396 non-diabetics

Mukamal KJ et al. Diabetes care, 2001

Obesity and the risk of heart failure. Kenechiah et al, NEJM 2002;347:305 Obese

Based on BMI at time of enrollment. Mean age at enrollment was 53 years. Of the patients who had an echo near the time of CHF dx, most had a reduced EF.

Overweight

Normal

Diabetes (and Obesity) are Independent Predictors of Heart Failure Independent of Underlying Coronary Artery Disease and Hypertension

The Heart in Obesity, Diabetes and Insulin Resistance

• The Myocardium is at Risk • Increased Risk of Heart Failure • Particularly in the Context of Ischemia and Hypertrophy • What are the Mechanisms?

A Pathophysiological Conundrum

Dyslipidemia

Inflammation and Oxidative Stress

Heart Disease Hyperglycemia

Hypercoagulability

Hypertension Insulin Resistance or Deficiency

Coronary Artery Disease Heart Failure LVH

The Obesity Insulin Resistance Diabetes Continuum

Saltiel A, Cell. 2000

Myocardial Substrate Utilization

Glucose

FFA

*

* Regulated Transport

Glucose Glycolysis

‡

*

Cytosol

F-Acyl-CoA

Nucleus

Acetyl-CoA MCD‡

Pyruvate

12

ACC

PPAR-alpha Target Genes

1: PPAR-α

Malonyl-CoA ‡ CPT1&2

Pyruvate PDK4

‡

Acetyl-CoA PDH

Citrate

‡: PPAR-α Targets

F-Acyl-CoA

ß-Oxidation ‡ Oxaloacetate Citrate TCA Cycle NAD, FAD ADP ATP Citrate Synthase

NADH, FADH2

Mitochondria ‡

UCP3

Electron Transport Chain

2: RXR

Cr ADP

PCr

ATP ADP

Oxidative Metabolism of 1 Molecule of Palmitate Yields Approximately 108 Molecules of ATP Palmitate

Beta-Oxidation

Mitochondrion

Cytosol 8 Acetyl CoA 7 FADH2 7 NADH 24 NADH 8 FADH2

TCA Cycle

8 ATP

6 ATP 16 CO2

16 O2 Respiratory chain

102 ATP 123 H2O

Oxidative Metabolism of 1 Glucose Molecule Yields Approximately 30 Molecules of ATP

Cytosol

2 ATP (net)

Glycolysis

Glucose

2 NADH

2 Pyruvate

GlycerolP Mitochondrion shuttle 2 FADH2 2 NADH 6 NADH 2 FADH2

TCA Cycle

2 ATP

1.5 ATP 6 CO2

6 O2 Respiratory chain

26 ATP 12 H2O

Metabolic Changes in the Heart in Obesity and Diabetes • Decreased Glucose Utilization • Increased FA Utilization • Increased Myocardial Oxygen Consumption • Impaired Insulin Action - Signaling Defects or Insulin Deficiency

Evidence from Human and Animal Studies

Characteristics of Study Cohort Body Mass Index 50

Serum Insulin 15

*

*

mU/ml

Kg/m2

40 30 20

10

5

10 0

Lean

Obese

0

Lean

Obese

Peterson L et al - Circulation 2004;109:2191-96

Cardiac Structure/Function LV Mass 200

Cardiac Output 6

*

L/min

Grams

150 100

4 3 2

50 0

*

5

1

Lean

Obese

0

Lean

Obese

Peterson L et al - Circulation 2004;109:2191-96

Cardiac Bioenergetics MVO2

Cardiac Work

4

0.5

J.g-1.min-1

0.3 0.2

3 2 1

0.1 0

0

Lean

Obese

Cardiac Efficiency

Lean

Obese

30

*

25 20

%

J.g-1.min-1

0.4

*

15 10 5 0

Lean

Obese

Peterson L et al Circulation 2004;109:2191-96

Fatty Acid Utilization

Peterson L et al Circulation 2004;109:2191-96

Animal Models of Type II Diabetes The Jackson Laboratory 4 or 8 week-old male db/db

4 or 8 week-old male ob/ob

(C57BL/KsJ-db/db) mice & homozygous normal lean (C57BL/KsJ) litter mates

(C57BL/J6-ob/ob) mice & homozygous normal lean (C57BL/J6) litter mates

LV Dilatation in 8-week-old ob/ob Mice

Control

Ob/ob

Ob/Ob Mice

Decreased Ejection Fraction Increased LV Mass LV Dilatation Increased dP/dT

Substrate Metabolism in the Hearts of ob/ob and db/db Mice at 8-10 weeks of age

Perfusion conditions: 11mM Glucose, 1mM Palmitate, 1nM Insulin Mazumder et al.,Diabetes, 2004; Buchanan et al. Endocrinology, 2005

What is Wrong with Using too Much Fat in the Heart?

Fatty Acid Utilization

Peterson L et al Circulation 2004;109:2191-96

Cardiac Performance and Myocardial Oxygen Consumption in the Hearts of ob/ob and db/db Mice at 8-10 weeks of age

Perfusion conditions: 11mM Glucose, 1mM Palmitate, 1nM Insulin

Mazumder et al.,Diabetes, 2004; Buchanan et al. Endocrinology, 2005

futile/ uncoupled proton cycling

proton cycling coupled to ATP synthesis H+

H+

H+

H+

H+

+ I

ΔΨm

II

Q

FADH2

e

-

III

e-

H+

H+

C

H+ e-

-

H+

H+

e-

e-

IV

FAD NADH

H2O

Respiratory Chain Flux O2

NAD

H+

beta-Oxidation, TCA Flux

ADP + Pi Proton Leak

H+

(uncoupling)

Intermembrane space

H+

F0

ATP

O2

•-

superoxide

H+

F1

Pi H+

Pi PC

ADP ATP

H+ ADP

ANT

ATP

matrix H+ Mitochondrial Inner Membrane

Mitochondrial ATP Production in Glucose and Palmitate Perfused db/db Mouse Hearts ATP/O

nmol.min-1.mgdw-1

ATP 45

3

† *

40

* †

2.5

35 2

30 1.5

25 20

Glucose

1

Palmitate

db/db WT

Glucose

Palmitate

Boudina et al, Diabetes, 2007

Increased ROS Production in db/db Mitochondria

µmol/min/mg mito protein

Mitochondrial H2O2 Generation 1.2

*

0.8

0.4

0

WT

db/db

Genotype Boudina et al, Diabetes, 2005

Fatty Acid Induced and Superoxide Mediated Mitochondrial Uncoupling Contributes to Impaired Myocardial Energetics in Diabetes and Obesity

Mechanistic Observations Human Studies --Using NMR spectroscopy individuals with type 2 diabetes were recently shown to have reduced myocardial high energy phosphate content that was inversely associated with circulating levels of FFA (Scheuermann-Freestone M et al. Circulation 107:3040, 2003), suggesting mitochondrial dysfunction

ROS-Mediated Mitochondrial Uncoupling Limits Mitochondrial ATP Generation, which Limits Cardiac Energetic Reserves

Bugger H, Abel ED, Clinical Science-114(3):195-210, 2008

In Addition to Mitochondrial Uncoupling, Mitochondrial Dysfunction Also Develops in the Heart in Obesity and Diabetes

Ultrastructural Changes in db/db Mouse Hearts

Wildtype

db/db Boudina et al, Diabetes, 2007

Transcriptional Profile in db/db hearts

Boudina S et al, Diabetes, 2007

Reduced Content of Mitochondrial OXPHOS Proteins in ob/ob Mouse Hearts Complex III

Complex I

Complex II

Complex V

UCP3

Boudina et al, Circulation 2005

Increased Beta-Oxidation Reduced OXPHOS Capacity

Increased Delivery Of Reducing Equivalents to the Electron Transport Chain

Increased ROS Activation of Mitochondrial Uncoupling Proteins Reduced Mitochondrial Energy Metabolism

FAO Delivery of Reducing Equivalents

OXPHOS

proton cycling coupled to ATP synthesis futile/ uncoupled proton cycling H+ H+ H+

+

H+ H+

H+

H+

H+

H+

H+

Respiratory Chain Flux

ΔΨm

H2O O2

Reducing Equivalents

H+

ATP

superoxide

TH

H2O

•-

2GSH NADPH

GPX

GR

GSSH

NADP

H2O

NO

ONOO-

Fe2+ NADPH + NAD

ADP + Pi

aconitase damage

PRX III H2O2

F1

H+

•OH-

oxidative damage

Mitochondrial Inner Membrane Intermembrane space

MnSOD

(uncoupling) NADP + NADH

H+

O2

Proton Leak

H+

F0

matrix

-

High Fat Feeding, Mitochondrial Dysfunction and Myocardial Lipid Accumulation

Myocardial Lipid Accumulation in the Metabolic Syndrome --Using MR spectroscopy a strong association between obesity and increased myocardial triglyceride accumulation was described. Indeed myocardial TG content was positively associated with LVH and inversely associated with LV function (Szczepaniak et al. Magnetic Resonance in Medicine 49:417, 2003).

From: McGavock: Circulation, Volume 116(10).September 4, 2007.1170-1175

From: McGavock: Circulation, Volume 116(10).September 4, 2007.1170-1175

From: McGavock: Circulation, Volume 116(10).September 4, 2007.1170-1175

From: McGavock: Circulation, Volume 116(10).September 4, 2007.1170-1175

High-Fat Feeding in Rats Leads to Myocardial Lipid Accumulation and Altered Mitochondrial Morphology

Myocardial Triglyceride (TG)

Ouwens DM et al, Diabetologia, 2005

Lipid Uptake is Increased In Part Because of Increased Plasma Membrane Expression of CD36

Ouwens DM et al, Diabetologia, 2007

High Fat Feeding Causes Cardiac Dysfunction

Fractional shortening (%)

50.8 ± 1.3

56.3 ± 2.4*

47.1 ± 1.7*,**

Lumen diameter (S) (mm)

3.41 ± 0.10

3.32 ± 0.25

4.07 ± 0.12*,**

Ouwens DM et al, Diabetologia, 2007

FAO Delivery of Reducing Equivalents

OXPHOS

Why is Mitochondrial OXPHOS Reduced?

Myocardial Insulin Resistance

Mechanistic Observations Human Studies • Using euglycemic clamps and PET scanning (under physiological levels of insulin), the hearts of individuals with type 2 diabetes demonstrates reduced insulin stimulated glucose uptake that was equivalently decreased in subjects with and without CAD. And a positive correlation was observed between myocardial glucose uptake and LV ejection fraction (Iozzo P et al. Diabetes 51:3020, 2002).

High Fat Feeding Leads to Myocardial Insulin Resistance

Ouwens DM et al, Diabetologia, 2007

Ouwens DM et al, Diabetologia, 2005

Wildtype

ob/ob

p-Akt t-Akt Insulin: - + - + - + - +

Densitometry (Arbitrary Units)

Insulin-Stimulated Activation of Akt is Impaired in ob/ob mouse hearts pAkt/Akt 6 5

* †

4 3 2 1 0

WT

ob/ob

Genotype Insulin 0 Insulin 1nM Mazumder et al.,Diabetes, 2004

Consequences of Impaired Insulin Signaling in the Heart Mice with Genetic Deletion of Insulin Receptors in Cardiomyocytes -CIRKO

Insulin Signaling and the Regulation of Mitochondrial Biology in the Heart

Myocardial Insulin Resistance Promotes Oxidative Stress

Insulin Signaling and Myocardial Ischemia

Serum Troponin 120

*

100

ng/ml

80 60 40 20 0 Sham

5

2

Duration of Isoproterenol (Days) WT CIRKO McQueen et al. J. Molecular and Cellular Cardiol, 2005

Insulin Resistant Mouse Hearts Exhibit Increased Myocyte Loss, Cardiac Fibrosis and Functional Deterioration When Exposed to Stressors that Induce Cardiac Hypertrophy

Histology after 5 days of Isoproterenol Infusion McQueen et al. J. Molecular and Cellular Cardiol, 2005

Reduced Capillary Density in ISO Treated CIRKO Hearts WT Sham

WT-ISO E Capillary Density 0.4

cm-1

0.3

CIRKO Sham

CIRKO-ISO

Wildtype

0.2

CIRKO

* †

0.1

0

0

5

Duration of Isoproterenol Treatment (days)

McQueen et al. J. Molecular and Cellular Cardiol, 2005

Insulin Signaling Contributes to the Maintenance of Vascular Integrity in the Ischemic Heart and may Promote Collateral Blood Flow

Insulin Signaling and Pathological Cardiac Hypertrophy

Aortic Banding in CIRKO Mice WT Sham

CIRKO Sham

IVS LV PW

WT MTAB

CIRKO MTAB

Hu P., et al. AJP, 2003

Insulin Regulates the Metabolic Response of the Heart to Cardiac Hypertrophy by Maintaining Glucose Utilization

Can Lack of Insulin Explain Everything?

Transgenic Overexpression of Acyl CoA Synthetase Increases Myocardial Fatty Acid Uptake and Alters Mitochondrial Dynamics and Function

Metabolic Changes in the Heart in Diabetes and Obesity • • • •

Decreased Glucose Utilization Increased FA Utilization Increased Myocardial Oxygen Consumption Impaired Insulin Action - Signaling Defects or Insulin Deficiency • Mitochondrial Uncoupling • Increased Oxidative Stress • Decreased OXPHOS Capacity

Our Mitochondrial-Centric View

Model for Synergistic Effects of Insulin Resistance and FA Excess ln Precipitating Mitochondrial Dysfunction in Hearts Fatty acids

Insulin signaling

ROS I

O2

ATP

I II

O2

II

III

F0

IV

UCP

ANT

H2O ADP ATP

Metabolic Basis for Cardiac Dysfunction in Diabetes and Obesity Increased Fatty Acid Delivery MITOCHONDRIA Increased FFA Flux Decreased Glucose Utilization Increased Mitochondrial ROS Increased Mitochondrial Uncoupling Progressive Mitochondrial Dysfunction Reduced Myocardial Reserve Increased Susceptibility to Injury

Insulin Resistance

Abnormal Calcium Homeostasis and Cardiac Dysfunction in Insulin Resistant States

Bugger H, Abel ED, Clinical Science-114(3):195-210, 2008

Boudina S, Abel ED, Circulation, 2007

Therapeutic - Challenges • What is the consequence of therapeutic strategies that increase myocardial insulin sensitivity? • What is the consequence of reducing myocardial oxidative stress on the cardiac phenotypes of diabetes? • What is the role of reducing myocardial TG accumulation? • Which therapeutics normalize the balance of myocardial substrate utilization? • What is the role of normalizing myocardial mitochondrial function?

The Lab Summer 2007

Acknowledgements C Ronald Kahn - Joslin Diabetes Center Jean Schaffer - Washington University