Emerging Issue in Toxicology: Metabolic Syndrome · The Metabolic Syndrome Industrial Toxicology...

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Jack R. HarkemaJuly 25, 2012

Emerging Issue in Toxicology:The Metabolic Syndrome

Emerging Issue in Toxicology:The Metabolic Syndrome

Industrial Toxicology and Pathology Short Course 2012

Outline

• Obesity and Chronic Diseases

• The Metabolic Syndrome (MetS)

• Animal Models for MetS Research

• High Fructose Diets and MetS

• Intersection of Health and Environment: Metabolic Syndrome and Air Pollution

Increased Prevalence of Obesity

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The Weight of the Nation

The Metabolic Syndrome

• Cluster of Risk Factors for CVD and Diabetes: Central Obesity; Dyslipidemia; Hyperglycemia; Hypertension; Insulin Resistance

• Dr. Gerald Reaves, Stanford University, 1988 Banting Lecture

• Syndrome X, Insulin Resistance Syndrome, CardioMetabolic Syndrome

• Increased risk of heart attack (2X), stroke (2X), and diabetes (5X)

• 20‐25% of world population

Prevalence of the MetS Across Age Groups and Gender in Various Countries

Cornier M et al. Endocrine Reviews 2008;29:777‐822

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Pathophysiology of MetS

Underlying Factor: Insulin Resistance (IR)


Pathophysiology : Inflammatory Enhancement of IR


Insulin Resistance in Obesity as the Underlying Cause for the Metabolic Syndrome

Gallagher EJ et al. Mount Sinai Journal of Medicine. 2010; 77: 511‐523

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Pathophysiology : Adipose Tissue Remodeling, Inflammation and Insulin Resistance

Sun K et al. J Clin Invest. 2011; 121(6):2094‐101

Pathophysiology : Obesity, Lipotoxicity and NAFLD

Cusi K. Gastroenterology 2012; 142: 711‐725

Pathophysiology : Obesity, Lipotoxicity and NAFLD

Cusi K. Gastroenterology 2012; 142: 711‐725

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Proposed mechanisms that link insulin resistance/hyperinsulinemia to hypertension in

fructose‐fed rats

Tran LT. et al. Mol Cell Biochem (2009) 332:145‐159

Animal Models for MetS Research

• Insects (e.g., dragonflies)

• Mice (genetic, diet‐induced)

• Rats (genetic, diet‐induced)

• Nonhuman Primates (diet‐induced)

• Horses (diet‐induced)

• Minipigs

Rodent Models for MetS Research

• Genetic Models of Obesity + T2DM

– ob/ob (C57BL/6‐ob/ob) Mice

– db/db (C57BL/KsJ‐db/db) Mice

– Zucker Diabetic Fatty Rats (fa/fa)

– Otsuka Long‐Evans Tokushima Fatty Rats

– Goto‐Kakizaki Rats

• Genetic models develop obesity and non‐insulin dependent diabetes, but MetS is a much broader constellation of pathophysiolic changes

Panchal SK and Brown L. J Biomed Biotechnol. 2011; 2011: 351982.

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Leptin/Leptin Receptor Deficiency

• Very rare mutations in humans

• ob/ob Mice

– Reduced BP

– Do not develop dyslipidemia


Lipoprotein Profiles in Different Mouse Models of Metabolic Syndrome

Kennedy et al, Disease Models & Mechanisms (2010); 3:156–165

Diet‐Induced Obesity and Health

Bray et al. Am J Clin Nutr 2004; 79: 537–543 Dekker M J et al. Am J Physiol Endocrinol Metab 2010;299:E685‐E694

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Diet‐Induced Metabolic Syndrome in Rodents

• High Fructose

• High Sucrose

• High Fat

• High Carbohydrate + High Fat

• Obesity‐Resistant Rat Strain

• High‐Fat + High‐Carbohydrate Diet‐Fed Spontaneously Hypertensive Rats (SHR)


High‐Carbohydrate, High‐Fat Diet‐induced Metabolic Syndrome


Percentage of change in the various metabolic parameters in SDR‐F and SHR‐S rat models

Mor Oron‐Herman et al, American Journal of Hypertension (2008); 21:1018–1022.

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Fructose‐Fed Rhesus Monkeys: NHP Model of Insulin Resistance, Metabolic Syndrome, T2DM

• Stanhope and Havel, UCD/CNPRC, Davis, CA

• Rhesus monkeys on HFrD for 12 months

• 30% fructose diet (Kool‐Aid; 75g/day)

• IR, cental obesity, dyslipidemia, and inflammation in 6 months (rapid onset)

• Subset developed T2 DM

• Efficient model for studying pathogenesis, prevention and treatment

Bremer et al. Clin Trans Sci 2011; 4:243‐252

Fructose and Glucose Metabolism

Fructose‐Fed Rhesus Monkeys with MetS


Weight Gain & Increased Adiposity Insulin Resistance

(GTT)

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Fructose‐Fed Rhesus Monkeys with T2DM


Fructose‐Fed Rhesus Monkeys: Adipokines


Fructose‐Fed Rhesus Monkeys: Proinflammatory Markers


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Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin.

Knowler WC et al. N Engl J Med. 2002; 346(6): 393‐403

Metformin protects against the development of fructose‐induced steatosis in mice

Spruss A et al. Lab Invest. 2012; 92:1020‐1032

Air Pollution and Metabolic Syndrome

RD83479701

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Our Center ObjectiveExplore and elucidate one of the most

prevalent and important globalhealth-environment interfaces:

Air Pollution and the CardioMetabolic Syndrome

National Public Health Burden Associated with Exposure to Ambient PM2.5 and Ozone

Fann et al. Risk Analysis. 32: 81-95, 2012

Brook R D et al. Circulation 2010;121:2331-2378

Copyright © American Heart Association

Increase in mortality per 10g/m3 increase in PM2.5 or PM10

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Health Effects of Air Pollution

• Particle pollution associated with increasing the risk of new cases of chronic diseases (e.g., CVD; diabetes)

• Heavy highway traffic connected to higher risks for heart attack, allergies, and premature births.

• Growing evidence suggests breathing pollution from heavy traffic may cause new cases of asthma in children.

Long‐term Exposure to Ambient Fine Particulate Pollution Induces IR in C57BL/6 Mice

Xu X et al. Toxicol Sci. 2011; 124(1): 88‐98

PM2.5 Exposure:6h/day; 5 days/wk;10 months; mean concentration: 94.4 µg/m3 (7x ambient)

Brook RD et al. Circulation 2010;121:2331-2378

Biological pathways linking fine particulate matter exposure with cardiovascular diseases

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Our Current Research Questions

Q1. What multipollutant atmospheres in the Great Lakes Region

adversely affect human health?

Q2. Does diabetes, obesity, or unhealthy diets make people more susceptible to the health effects of air pollution?

Proposed PathogenesisCARDIOVASCULAR EVENTS

DIABETESATHEROSCLEROSIS

Insulin resistanceand Obesity

Elevated Blood PressureVascular Dysfunction

Alterations of Lipids in the BloodImpaired HDL function

CARDIOMETABOLIC SYNDROME

Inflammation, Oxidative Stress, Autonomic Nervous System Imbalance

Air PollutionOzone, PM

Lifestyle FactorsHigh fat or sugar diets; Genetics

Center Projects

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Human and Animal Exposures to Multi-pollutant Atmospheres

To provide insights into the health effects of PM, O3, and their

coexposures in a multipollutant context.

Project 1: Short-Term Human Studies

Cardio-metabolic Effects of Exposure to Differing Mixtures and Concentrations of Coarse and Fine

Concentrated Ambient Particles in Obese and Lean Adults

Robert Brook, MD1, Elif Oral, MD1

Marianna Kaplan, MD1 and Jesus Araujo, MD2

1The University of Michigan, Ann Arbor, MI2University of California, Los Angeles, CA

*BMI and/or age-adjusted (per 10 g/m3 of 5-day PM2.5 average)

OUTCOME β* 95% CI p

SDNN (msec)[HEART RATE VARIABILITY]

‐13.1 ‐25.3 to ‐0.9 0.035

†HOMA‐IR[METABOLIC INSULIN SENSITIVITY]

0.7 0.1 to 1.3 0.023† Homeostasis model assessment of insulin resistance : [glucose (mg/dL) x insulin (µU•ml-1)]/405

(Lower values denote better metabolic insulin sensitivity)

PROJECT 1: PRELIMARY DATA Reduced insulin sensitivity in human subjects

with 5-day ambient PM2.5 exposure

Autonomic imbalance may be the mechanism linking PM to insulin resistance

SDNN was inversely associated with HOMA-IR (β=-0.13 per 10 msec HRV change, p=0.035).

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Project 2: Short-Term Animal Studies

Cardiometabolic, Autonomic, and Airway Toxicity of Acute Exposures to PM2.5

from Multipollutant Atmospheres in the Great Lakes Region

Jack Harkema, DVM, PhD1, Greg Fink, PhD1

James Wagner, PhD1, Masako Morishita2, Tim Dvonch2, Cathie Spino2, and Bhramar Mukherjee2

1Michigan State University, East Lansing, MI2The University of Michigan, Ann Arbor, MI

Project 2: Animal Toxicology Studies

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7:00 7:30 8:00 8:30 9:00 9:30 10:00 10:30 11:00 11:30 12:00 12:30 13:00 13:30 14:00 14:30

PM

2.5 c

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Unidentified

Cement/Lime

Coal

Metal

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Motor/Diesel

Refinery

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PM

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Unidentified

Cement/Lime

Coal

Metal

Sludge

Motor/Diesel

Refinery

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CAPs ± O3

ND

HFrD

High Fructose Diet

• Fructose has same chemical formula as glucose (C6H12 O6), but with different stereochemistry.

• Metabolism of fructose differs from glucose, and is insulin independent.

• In 8 wks, rats develop hyperglycemia, insulin resistance, dyslipidemia, high blood pressure, and hepatic steatosis.

Normal Diet (Teklad 22/5)

60% FructoseDiet

(TD.89247)

Protein (% by weight)

22.0 % 18.3%

Carbohydrate 40.6 % 60.4%

Fat 5.5 % 5.2%

Kcal/g 3.0 3.6

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Air Pollutants

DietAir *CAPs

(PM2.5)O3

(0.5 ppm)O3 &CAPs

Mixture

Normal (ND)

8 rats 8 8 8

High Fructose (HFrD)

8 8 8 8

• Male rats on diet for 8 wks prior to and during exposure• Daily 8h-exposures for two weeks (5 & 4 days/wk; 9 total exposure days)* ~400 g/m3 Concentrated Ambient Fine Particles (CAPs)• Animal necropsies one day after last exposure

Study 1: Dearborn Study Design

Urban/Industrial Exposure Site

Cardiovascular Telemetry (BP, ECG)

• 8 rats with implanted telemeters in each exposure chamber

• 30-second recordings every 5 minutes during daily 8-hour exposures

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Chamber Concentrations

AirPollutant

Average Daily Concentrations

(Mean ± Standard Deviation)

Ozone (O3) 0.50 ± .03 ppm

CAPs(PM2.5) 444 ± 196 g/m3

O3 & CAPsMixture

O3: 0.49 ± .04 ppm

CAPs: 356 ± 261 g/m3

Summary of Current Findings• High fructose diet produced facets of the CMS in rats

(e.g., hypertension, insulin resistance, hyperglycemia, and hepatic steatosis).

• Acute exposures to O3, CAPs, or CAPs+O3 caused reductions in BP and HR that were markedly enhanced in HFrD-fed rats.

• Enhanced BP and HR responses in HFrD-fed rats suggest a diet-induced dysfunction in the autonomic nervous system.

• CAPs+O3 caused a greater decrease in BP and HR in the first few days of exposure, but a quicker adaptive response with repeated exposures.

• Preliminary data suggests that TRP ion channel(s) may mediate ozone-induced drop in BP.

M T W T F S S M T W T

Ch

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Week 1Days of Exposure


Effect of 8h Ozone on HRin Rats fed Normal or HFr Diets

(Compared to Filtered Air Exposure )

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Daily Effect of Ozone Exposure on Blood PressureIn Rats Fed Normal or High Fructose Diets

Days of Exposure


Ch

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Mea

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mm

Hg

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-10

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Normal Diet High Fructose Diet

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Week 1 Week 2

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Days of Exposure

Effect of 8h Ozone on BPin Rats fed Normal or HFr Diets

(Compared to Filtered Air Exposure)


Ch

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pm

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Effect of 8h CAP on HRin Rats fed Normal or HFr Diets


Days of Exposure


Ch

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ea

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ria

l P

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ure

(m

m H

g)

-20

-10

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10Normal Diet High Fructose Diet

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Week 1 Week 2

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Days of Exposure

Effect of 8h CAP on BPin Rats fed Normal or HFr Diets


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How do air pollutants cause a drop in HR and BP?

• Trigeminocardiac reflex (TCR) causes bradycardia (increased parasympathetic activity) and is the most powerful autonomic reflex in the body.

• Irritants induce stimulation of airway sensory nerves and transient receptor potential channels (TRPs; e.g., TRPA1)

• Does O3 and/or CAPs cause a drop in HR and BP through TCR and/or TRPs?

• What are the mechanism(s) underlying HFrD enhancement of the exposure-induced bradycardia and hypotension?

Hazari MS et al. Environ Health Perspect, 2011,

119:951

Ozone TempHoffmann et al. Environ Health Perspect,

2012, 120:241

neu

tro

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ils/m

m b

asal

lam

ina

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Normal Chow 60% High Fructose

Air controlCAPsO3CAPs/O3

*#*#

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Exposure-induced nasal airway Inflammation and epithelial remodeling

epit

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cell

s/m

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asal

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Normal Chow 60% High Fructose

Air controlCAPsO3CAPs/O3

*#&+*

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Project 3: Long-term Animal Studies

Long-term Metabolic Consequences of Exposures to Multipollutant Atmospheres

in the Great Lakes Region

Sanjay Rajagopalan, MD and Qinghua Sun, MD

The Ohio State University, Columbus, OH

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Project 3: Aim 1

• To assess effects of multi-pollutant CAP (regional vs. near-roadway) on glucose and insulin homeostasis, inflammation and insulin signaling pathways.

• To identify inflammatory chemokine mediators.

• To investigate temporal response of multi-pollutant CAP and CMS effects.

Hypothesis: Near-roadway CAP exposure promotes development of obesity and insulin resistance.

Design: C57Bl/6 model fed normal chow or high-fat chow and exposed to FA/CAP for 12 or 18 weeks. KKAy mice exposed to CAP over 8-10 weeks

KKAy Mice = Heterozygous for the yellow spontaneous mutation (Ay). Progressively develop insulin resistance, obesity over 6-12 weeks

Effect of Regional CAP Exposure in a Model of Genetic Type II DM

(KKAy Mouse Model)

EXPOSURE CONCENTRATIONS (Columbus Regional:12/28/2011-02/28/2012)

Ambient FA CAPS

8.27 g/m3 1.51 g/m3 102.9 g/m3

Enrichment Factor = 12.22

4-5 wk-old KKAy mice exposed to FA or CAP (normal diet)

Regional CAP Exposure and Insulin Resistance Measures in Genetic Type II DM (KKAy Model)

*P<0.05, **P<0.01, ***P<0.001 vsrespective FA group.

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5‐wks exposure

Effects of Regional CAP Exposure on Metabolic Indices

5 weeks exposure 8 weeks exposure

Short term CAP exposure has profound effects on metabolism and reduces oxygen consumption, VCO2 production and thermogenesis

Regional CAP exposure F4/80+ CD11c+ Adipose Tissue Macrophages (ATMs) in Type II Diabetic Mice

FA PM

5WK

8WK

F4/80

5-weeks of CAP exposure sufficient to induce VAT infiltration by ATMs. Analysis is on stomal vascular fraction (SVF) of epididymal fat

Williams and Schwartz. J Clin Invest. 2011;121(6):2152–2155.

Thaler and Schwartz. Endocrinology 2010;151:4109‐4115

Thaler et al.J Clin Invest. 2012 Jan 3;122(1):153‐62.

Recent studies have suggest that high-fat diet (HFD) induces hypothalamic inflammation (arcuate nucleus) rapidly (24 h)

─ Hypothalamic inflammation and ER stress regulates peripheral inflammation

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TNF

MA

C1

IL6

SO

CS3

HM

GB

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1.5

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Rel

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e m

RN

A (

fold

FA

)Regional CAP Exposure Increases

Inflammation in Hypothalamus within 5 weeks

Prior studies have demonstrated that hypothalamic inflammation occurs within 1 week in response to HFD

feeding in the arcuate nucleus (Thaler et al. 2012)

Diverse Stimuli in(Air Pollution, High Fat Feeding)

Rapid Hypothalamic Inflammation

Autonomic Imbalance/ Vagal Anti-Inflammatory Reflux

Peripheral Inflammation

Type II Diabetes

Working hypothesis

• Metabolic syndrome is a growing global problem and currently affecting 25% of our population.

• A variety of animal models are used in MetS research.

• Recognition of the strengths and limitations of the individual animal models is needed for proper selection and interpretation of results.

• Environmental air pollution may enhance the magnitude and onset of facets of the metabolic syndrome and associated chronic diseases.

• More studies are needed to understand how toxicants (or pharmaceuticals) may adversely affect those suffering from metabolic syndrome and associated chronic diseases (e.g., CVD, diabetes).

Summary & Conclusions

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• MSU: Drs. Katy Allen, Jim Wagner, and Greg Fink

• MSU: Ryan Lewandowski, Lori Bramble, Ian Hotchkiss, Vanessa Hoang, Dennis Shubitowski, Daven Jackson-Humbles, Hannah Garver

• UM: Drs. Robert Brook, Tim Dvonch and Masako Morishita

• OSU: Drs. Qinghua Sun and Sanjay Rajagopalan

• MSU: Drs. P.S. MohanKumar and Sheba Mohankumar (neuroendocrine)

• MSU: Drs. Anna Kopec and Tim Zacharewski (liver global gene expression)

• MSU: Dr. Linda Mansfield (gut microbiome)

• MSU: Drs. Ping Zhang and Xin Shi (bone marrow)

• SCPC: Drs. John Froines (UCLA), Michael Kleinman (UCI) Costantinos Sioutas (USC), Andre Nel (UCLA), Jesus Araujo (UCLA) and Ning Li (UCLA)

• EPRI: Dr. Annette Rohr

• Grant Support: EPA; NIEHS; EPRI; HEI; MSU Foundation; MSU Respiratory Research Initiative

Acknowledgments

Questions?

Emerging Issue in Toxicology: Metabolic Syndrome · The Metabolic Syndrome Industrial Toxicology...

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