Paul M. Yen, M.D.Laboratory of Hormonal RegulationCardiovascular and Metabolic Diseases ProgramDuke-NUS Graduate Medical Schoolpaul.yen@duke-nus.edu.sg

Thyroid hormone and lipid metabolism: New answers to old questions

10th AOTA CongressOctober 22, 2012

Metabolic Syndrome

Obesity: A Recent Metamorphosis During Evolution

Obesity Trends Among U.S. Adults1988

(*BMI ≥30, or ~ 30 lbs. overweight for 5’ 4” person)

No Data <10% 10%–14

Obesity Trends Among U.S. Adults 2008

(*BMI ≥30, or ~ 30 lbs. overweight for 5’ 4” person)

No Data <10% 10%–14 15%–19% 20%–24% 25%–29% ≥30%

Obesity: An Epidemic in Asia

Prevalence of obesity by NCEP ATP III definition (BMI> 30) and the Asian adapted definition (BMI >25)

Population Prevalence by ATP III Prevalence by Asian

Japan M: 16.8% F:22.3% M: 21.6 F: 31.3%South Korea M: 16%; F: 10.7% M: 29%; F: 16% China All: 10.1% All: 26.3% Singapore M: 13.1%; F: 11% M: 20.9%; F: 15.5% Taiwan M: 11.2%; F: 18.6% M: 23.8%; F: 17.7% Hong Kong M: 15.3%; F: 18.8% M: 20.2%; F: 23.6% Philippines M: 14.3%; F: 14.1% M: 18.6%; F: 19.9%

Asia Pac J Clin Nutr 16:362-367 (2007)

Doi Stroke 40:1187-1194 (2009)

What role could TH have in metabolic syndrome?

Metabolic effects of thyroid hormone

• Increases metabolic rate, O2 consumption, ATP hydrolysis leading to heat production and weight loss.

•Decreases serum cholesterol and triglycerides.

•Stimulates fatty acid mobilization and beta oxidation.

•Increases insulin-mediated glucose uptake, glycogenolysis, and gluconeogenesis.

•Potentiates sympathetic effects on heart and vascular system.

Metabolic effects of thyroid hormone

• Increases metabolic rate, O2 consumption, ATP hydrolysis leading to heat production and weight loss.

d-thyroxine as a treatment for hypercholesterolemia

TriiodothyronineTiratricol Triiododothyroacetic acid (TRIAC)

FDA recall Still available on internet

Ingredients: L-Tyrosine, Bovine Thyroid Powder,Bovine Adrenal Powder, Guglipid, Nori, Piper Longum Extract,Ginger Extract

Ingredients:

Thyroid Tissue, Adrenal Tissue, Pituitary Tissue, Thymus Tissue, Spleen Tissue, Kelp.

Ingredients include:

Kelp extractIodine supplement

Herbal Supplements

Thyroid Extracts

Metabolic effects of thyroid hormone

• Increases metabolic rate, O2 consumption, ATP hydrolysis leading to heat production and weight loss.

•Decreases serum cholesterol and triglycerides.

Serum lipids in hypothyroidism

• Hypothyroidism is the most common cause of secondary hyperlipidemia

• Increased serum cholesterol and triglycerides

• Increased LDL>VLDL>HDL; HDL can be increased, unchanged, or decreased; LDL/HDL ratio is increased

How does thyroid hormone improve dyslipidemia?

How does thyroid hormone improve dyslipidemia?

• Increased LDLr expression reduces cholesterol due to increased LDL clearance

• Increased LDLr expression reduces TG due to increased LDL and VLDL clearance

How does thyroid hormone improve dyslipidemia?

• Increased LDLr expression reduces cholesterol due to increased LDL clearance

• Increased LDLr expression reduces TG due to increased LDL and VLDL clearance

• Inhibition of SREBP1 leads to decreased hepatic fatty acid synthesis and VLDL secretion

How does thyroid hormone improve dyslipidemia?

• Increased LDLr expression reduces cholesterol due to increased LDL clearance

• Increased LDLr expression reduces TG due to increased LDL and VLDL clearance

• Inhibition of SREBP1 leads to decreased hepatic fatty acid synthesis and VLDL secretion

• Increased reverse cholesterol transport. Increased HDL receptor (SRBP1), cholesterol 7α-hydroxylase (CYP7A1), and ABCG.

Sites of TH action in lipid metabolism

Liberopoulos and Elisaf, Hormones 2002

Sites of TH action in lipid metabolism

Liberopoulos and Elisaf, Hormones 2002

Sites of TH action in lipid metabolism

Liberopoulos and Elisaf, Hormones 2002

Thyroid hormone analogs: Magic bullets for hypercholesterolemia?

Strategies for TH Analogs

Potential therapies for hypercholesterolemia and obesity

1) Tissue-specific uptake

2) Tissue-specific metabolism and activation (e.g., liver)

3) TR isoform-specific binding

Thyroid hormone receptor isoforms

Effects of KB-141 on Serum Cholesterol, Heart Rate, Body weight, and serum Lp(a)

level

Grover et al. PNAS 2003

GC-1 Effects on Reverse Cholesterol Pathway and Bile Clearance

Johanssen et al. PNAS 2005

Cholesterol Lowering Effects of GC-1

Grey, control

Green, GC-1 Blue, atorvastatin (Lipitor)

Baxter et al. TEMS 2005

Effects of Eprotirome (KB2115) on serum levels of cholesterol, lipoproteins, and triglycerides

N Engl J Med 2010;362:906-16

Changes in serum LDL cholesterol concentration and body weight in patients treated with DITPA

Ladenson P W et al. JCEM 2010;95:1349-1354

DITPA (solid lines) and placebo (dashed)

Change in cardiac index from baseline over 24 weeks of treatment

Goldman S et al. Circulation 2009;119:3093-3100

Summary

Isoform-specific and tissue-specific TH analogs may be novel and useful therapiesfor obesity, hyperlipidemia, and hyperglycemia of metabolic syndrome.

Metabolic effects of thyroid hormone

• Increases metabolic rate, O2 consumption, ATP hydrolysis leading to heat production and weight loss.

•Decreases serum cholesterol and triglycerides.

•Stimulates fatty acid mobilization and beta oxidation.

Non-alcoholic fatty liver disease (NAFLD), is a common feature of metabolic syndrome and a silent world-wide epidemic.

NAFLD is a spectrum of disorders characterized by fat accumulation and injury in the liver.

NAFLD Incidence

• Estimated to occur in 30% American adult population

• Occurs in 60-80% patients with obesity and/or diabetes

• NASH with liver injury occurs in 2-5% of cases

• Occurs in 2.5% of pediatric population

• Rate is increasing worldwide

NAFLD is a spectrum of liver disorders

Types

1) Fat accumulation in the liver (Steatosis)

2) Fat accumulation and inflammation (Non-alchololic hepatosteatosis (NASH))

3) NASH and fibrosis (Scar tissue in liver)

4) Cirrhosis

5) Hepatocellular carcinoma

Non-Alcoholic Fatty Liver Disease(NAFLD)

Fatty liver (Steatosis)

Steatohepatitis - inflammation - fibrosis

Cirrhosis

Normal liver

Liver Damage

Sat FA

2nd Hit

Apoptosis

Hepatocyte Mass and Fibrosis

Fatty Liver

Mechanism for NAFLD

Oxidative stressToxinsInflammatory moleculesInfection

Thyroid hormone and hepatic lipid catabolism

• Hepatic lipid catabolism involves:1. uptake of free fatty acids (FFA) from circulation and storage2. release of FFA from intra-hepatic lipid droplet stores3. shuttling of free fats into mitochondria followed by β-oxidation

• Thyroid hormone (T3) is known to increase hepatic lipid catabolism by increasing free fatty acid uptake from adipose tissue and mitochondrial shuttling through Cpt1α.

• However little is known about the T3 effects on lipid droplet turnover.

• Hypothyroidism is linked to increase incidence of fatty liver disease characterized by lipid droplet deposition in liver. Pagadala MR et al., Dig Dis Sci. 2012 57:528-34

Mechanisms of hepatic lipid droplet turnover

Singh R et al. Nature 458:1131-5 (2009)

Can T3 stimulate autophagy?

Model of autophagy

www.cellsignal.com

T3 responsiveness in TR-expressing human hepatocytes (HepG2 cells)

0

1

2

3

4

5

6

7

8

9

10

LC3-B Pepck Cpt1αFold

cha

nge

in e

xpre

ssio

n af

ter 7

2hrs

control

(+) T3

*

*

*

T3 induces autophagy in HepG2 cells

(LC3II Western blotting and immunostaining)

DAPI / LC3-II Punctation

Thyroid hormone (T3) promotes autophagosome and lysosome formation in hepatoma cells

LC3-II/Bodipy staining shows increased induction of “lipophagy” by T3

Con

trol

T3 t

reat

ed

DAPI/LC3-II BODIPY 493/503

TH structural analog GC-1 induces autophagy in TR-expressing HepG2 cells

Actin

LC3-II

LC3-I

T3C GC1

T3 induces hepatic autophagy in vivo and is TR-dependent

T3 induces hepatic “lipophagy”in vivo

Control T3-treated

Autophagy mediates T3-induced hepatic β-oxidation in vivo

Major findings in liver metabolomics: Increased acylcarnitines after T3 treatment and

decreased b-oxidation in NDAD mice

Middle-chain hepatic acylcarnitines are affected by different TH status (hypo vs. hyper)

Long-chain hepatic acylcarnitines are affected by both TH status and NCoR DAD mutation

0

1

2

3

4

5

6

Dio1 Dio2 Dio3

MCT8

OATP1B

3

NCoR

SMRT

SRC-1DO

RFo

ld c

han

ge

in g

ene

exp

ress

ion

NCD

MCD

* * * * * *

Dio1 Dio2 Dio3 MCT8OATP1B3 THRβ NCoR SMRT SRC-1 DOR TRα1 RXRα

NCD 1 1 1 1 1 1 1 1 1 1 1 1

MCD 0.445 3.41 0.51 0.5 0.35 0.57 0.5 0.62 0.58 0.49 0.64 0.88

*p<0.05, Each bar represents the mean of the respective individual ratios ± SEM from unpaired t-test, (n = 4 rats from each group).

T3 signaling may be impaired in fatty liver condition *

* * ** * *

T3 blocks apoptosis and induces autophagy due to lipotoxicity in HepG2 cells

T3 blocks apoptosis and induces autophagy due to lipotoxicity in HepG2 cells

Summary

1. T3 induces autophagy in cultured hepatocytes and liver in vivo.

2. T3 effects on autophagy and b-oxidation of fatty acids facilitates their clearance and consumption leading to decreased hepatosteatosis

3. T3-mediated autophagy protects hepatocytes from apoptosis induced by fatty acids.

Conclusions

TH or TH analogs may be useful therapies for obesity, hypercholesterolemia, and NAFLD in patients with metabolic syndrome.

Drugs that promote hepatic autophagy may be useful treatments for NAFLD.

In certain disorders, some tissues may have intracellular deficiency of TH, and tissue-specific or isoform-specific analogs may be potential therapies in these conditions (e.g., liver, heart, brain). Serum TSH only measures pituitary response to TH.

Collaborators

Laboratory of Hormonal Regulation CVMD

Rohit SinhaChui Sun Yap

Sherwin Xie

Zhou Jin

Brijesh SinhaBenjamin FarahDarius AuAlvin Tan

Lab of Ceramides and Metabolic Disorders CVMD

Scott SummersMonawarul SiddiqueBenjamin Bikman

Dept Anatomy NUS

Bay Boon Huat

Stedman Center, Duke University

Christopher Newgard

Endocrinology and Metabolism Division, Duke

Marc Feinglos

Brittany Bohinc

Diabetes Center, University of Pennsylvania

Mitchell Lazar

Seo-Hee You

Thanks !!!

Yen Lab

Thank you!