REGULATION OF CHOLESTEROL METABOLISM BY TSH

1. REGULATION OF CHOLESTEROL METABOLISM BY TSH JIAJUN ZHAO Department of Endocrinology and Metabolism, Provincial Hospital affiliated to Shandong University Institute of Endocrinology, Shandong Academy of Clinical Medicine jjzhao@memdail.com.cn

2. knowledge on TSH Background TSH (thyrotropin，thyroid stimulating hormone): A kind of glycoprotein from adenohypophysis Usually think, thyroid is the only effector of TSH

3. TSH receptors locating the thyrocyte membranes Background knowledge on TSH

4. Distribution of TSHR on extrathyroidal tissues Intraorbital tissue TSHR mRNA and TSH binding site are found in orbital fibroblasts and preadipocyte，which may relate with thyroid associated ophthalmopathy Adipose tissue First to be found，now have found that fountional TSHR could be expressed in human adipocyte and preadipocyte, can regulate the growth、 differentiation and endocrine function of adipocyte Immune System TSHR is selected expressed in peripheral immune system cells、bone marrow cell population and Lymph node T cells, and involved in the interaction of the immune-nervous-endocrine system TSHR Bone tissue and bone cells TSH plays a role in the process ofbone remodeling, bone formation and resorption through binding with TSHR expressed in osteoblasts, osteoclast precursors Others kidney、testis、cardiac muscle、red cell、nerve cell、etc。 Paschke R, J Mol Med. 1995 . Endo TJ Biol Chem. 1995 Mengistu M, J Endocrinol Invest. 1994 Balzan S, Biomed Pharmacother. 2007 Abe E, Cell. 2003 Crisanti P, Endocrinology. 2001

5. Background Secondary hypercholesterolemia • Hypercholesterolemia: • leading to atherosclerosis and increase cardiovascular event risk • hypothyroidism: • a very important reason for secondary hypercholesterolemia Iervasi, G., et al. Arch Intern Med, 2007. 167(14): 1526-32.

6. Thyroid hormone deficiency contributing to Hypercholesterolemia in hypothyroidism Overt hypothyroidism subclinical hypothyroidism thyroid hormones↓ TSH ↑ thyroid hormones normal Traditional theory Cholesterol ↑

7. Thyroid hormone deficiency contributing to Hypercholesterolemia in hypothyroidism Overt hypothyroidism subclinical hypothyroidism thyroid hormones normal thyroid hormones ↓ TSH ↑ Traditional theory It can not be explained by the traditional theory X Cholesterol ↑

8. Thyroid hormone deficiency contributing to Hypercholesterolemia in hypothyroidism Overt hypothyroidis subclinical hypothyroidism thyroid hormones normal thyroid hormones ↓ TSH ↑ Traditional theory ？ X Cholesterol ↑

9. An association of a high TSH level with the elevation of cholesterol GayJ.Canaris et al. ARCH INTERN MED 2000; VOL160

10. atherosclerosis 1.1-2.6 Myocardial infarction 1.3-4.0 3.5 3 2.5 2 1.5 1 0.5 0 Follow-up study of Whickham’ study ( 20 years） OR Even mildly elevated TSH : Testing the elevated serum total cholesterol and an increase inatherosclerosis and cardiovascular event risk in clinic euthyroid subclinical hypothyroidism S Razvi , et al. J Clin Endocrinol Metab, 2010.95: 1734–1740

11. The high TSH level is associated with the increased cholesterol levels Asvold BO’ Study Cholesterol (mmol/L) Asvold BO, et al. Eur J Endocrinol. 2007.

12. A cross-sectional study in euthyroid Chinese subjects: Investigating the relationship between serum TSH levels and lipid profiles 4848subjects for a routine health check-upin Shandong Provincial Hospital in China 1139subjects were excluded: • with abnormal thyroid function • taking thyroid medications • with chronic liver or renal diseases • with any diseases or taking any medicine that might affect thyroid status and lipid metabolism • pregnant women 3709 subjects for preliminary data analysis 45 subjectswhose absolute value of residual standard deviation is less than 3 with regression analysis of two variables by one factor. 3664 euthyroid subjects for final evaluation ZHAO JJ et al JCEM 2012

13. The action of TSH on TC levels consisting of both direct effects and indirect effects via thyroid hormones gender 0.3595 TT3 FT3 age -0.2652 0.1422 0.3061 -0.0298 0.0598 TSH 0.1196 FPG TC 0.0873 0.1127 - 0.2256 0.1041 BMI 0.3974 TT4 FT4 Smoking status . PATH ANALYSIS (Values represent path coefficients)

14. A significant linear trend toward higher logTC (P=0.021) levels with increasing serum TSH levels within the reference range Logistic regression model Compared with subjects in the lower part o the reference range (TSH level, 0.27–0.61 mIU/liter), the hypercholesterolemia risk is high in the upper category (TSH level, 4.61–5.5mIU/liter)

15. The association between TSH and logTC: stronger among the olders than the youngers 0.15 0.1 coefficient 0.05 0 12-29 30-39 40-49 50-59 60-69 70-93 Categories of age (yr) Partial correlations of TSH with log transformation of TC according to categories of age

16. A retrospective study in Shandong Province in China:Euthyroid non-smokers with newly diagnosed asymptomatic coronary heart disease Atotalof921subjectswithnewlydiagnosedasymptomaticCHD subjects were excluded: • Without information on vital status or with missing data on serum TSH or thyroxine levels (n=66) • Taking medications that might affect FT4 or TSH levels or lipid profiles (n=68) • Having neurologic diseases,hepatic disorders, renal disorders, or euthyroid sick syndrome (abnormal low serum FT3 but normal FT4 and TSH) (n=98) • smokers including both present and past to baccousers (n=168) • pregnant women theremaining521nonsmokers Dysfunction of thyroid. 406euthyroidsubjects(187males,219females

17. Correlation analysis of thyroid function and serum lipid parameters in euthyroidic patients Positive and linear association between TSH level and logTC value

18. Effects of TSH on serum lipid levels Suggestions: TSH per se play the action effect on cholesterol independent of thyroid hormones in CHD

19. Increase in the prevalence rate of hypertriglyceridemia following serum TSH level elevation in the patients with coronary heart disease Evenafteradjustingforconfoundingfactors,suchassex,age,smokingstatus,fastingplasmaglucoselevelsand thyroid hormones,asignificantpositiveimpactofTSHontheserumtotalcholesterollevel is also revealed ZHAO JJ et al. Nutr Metab (Lond). 2012

20. Therapy issues highlighted in the areas of subclinical hypothyroidism in clinic: yes or not ? Guide to subclinical hypothyroidism therapy if TSH < 10 μIU/mL suggestions: observation （ Col, N.F., et al. 2004JAMA） The patients with elevated serum TSH levels (<10 μIU/mL) in subclinical hypothyroidism :up to 75%！ Most patients do not be received the active timely treatment !

21. Lacking: Direct convincing evidence Between TSH and cholesterol ? Therapy issues highlighted in the areas of subclinical hypothyroidism in clinic: yes or not ? Increase In atherosclerosis Influence the treatment strategy on subclinical hypothyroidism Question TSH elevation Cholesterol increased

22. Effect of TSH on liver ? TSH ? Liver Thyroid cholesterol

23. Liver is the most important organ for cholesterol metabolism

24. cholesterol Synthesis Cholesterol Conversion to bile acids maintaining cholesterol metabolism homeostasis balance

25. The fact is really exists: Presence of TSHR in hepatocytes Confirmation: mRNA and proteins of TSHR Zhao JJ et al J Cell Mol Med ,2009

26. The fact is really exists: TSHR in hepatocytes TSHR proteins locating on the membrane of hepatocytes

27. TSHR is functional TSH AC • a: L-02 cells； • b: CHO（negative control） • c: human primary normal cells； • d：NBL mouse cells C: control；FOR: AC agonist； GLU: glocugan TSH binding with the TSHR plays its biological rolemainly through adenylyl cyclase (AC) pathway to increased intracellular cAMP accumulation

28. HMG-COA reductase a rate-limiting enzyme in cholesterol synthetize Liver is the major organ for cholesterol synthesis HMG-CoA reductase(HMGCR) is the rate-limited enzyme in cholesterol synthesis the liver expresses HMGCR with the highest abundance

29. Experimental Design Confirm the TSH effects in Rat hypothyroidism model In order to exclude the effect of negative feedback, artificial control the endogenous TSH level, we establish hypothyroidism model through surgical removal of the rat thyroid gland.

30. TSH increases HMGCR mRNA, protein and activity

31. Cholesterol contents wereincreased by TSHin vivo TSH TC TSH -- S M L + + + + T4

32. Mechanism of the increased cholesterol contents by TSH in hepatocytes TSH directly up-regulates hepatic HMGCR activity resulting in elevated serum TC via TSHR/cAMP/pCREB signaling pathway ZHAO,JJ et al HEPATOLOGY 2010

33. cholesterol inicrease by TSH cholesterol conversion to bile acids maintaining cholesterol metabolism homeostasis Imbalance ??? ???

34. TSH decreases cholesterol conversion Decrease in CYP7A1 proten (green) Decrease in Bile acid contents

35. The contents of bile acids are increased in TSHR-KO mice TSHR-KO Wild type Elevated CYP7A1 activity Increased bile acid contents

36. Conclusions • TSH can affect cholesterol metabolism including synthesisand conversion in liver • TheTSHlevel,evenwithinthenormalrange, ispositivelyandlinearlycorrelatedwith serum totalcholesterol level • TSH increases the cholesterol level driving from TSH up-regulating HMGCR activity leading to an increase in cholesterol synthesis • TSH down-regulating the CYP7A1 activity resulting in a decrease in cholesterol conversion, both contributing together to thecholesterol elevation.