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Development Of Cushing’s Syndrome In Corticotropin-Releasing Factor Transgenic Mice

Development Of Cushing’s Syndrome In Corticotropin-Releasing Factor Transgenic Mice. Stenzel-Poore, M.P., V.A. Cameron, J. Vaughan, P.E. Sawchenko, and W. Vale. 1992. Development of Cushing’s Syndrome in Corticotropin-Releasing Factor Transgenic Mice. Endocrinology 130: 3378-3386.

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Development Of Cushing’s Syndrome In Corticotropin-Releasing Factor Transgenic Mice

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  1. Development Of Cushing’s Syndrome In Corticotropin-Releasing Factor Transgenic Mice Stenzel-Poore, M.P., V.A. Cameron, J. Vaughan, P.E. Sawchenko, and W. Vale. 1992. Development of Cushing’s Syndrome in Corticotropin-Releasing Factor Transgenic Mice. Endocrinology 130: 3378-3386. http://access.barry.edu:2138/cgi/reprint/130/6/3378.pdf

  2. CONTENTS • Background • Hypothalamic/pituitary axis in health • What happens when axis is perturbed • Cushing’s Syndrome (Definition) • Signs/Symptoms • Diagnosis • Treatments Primary Source Article -Objective -Data • Conclusion • References

  3. BACKGROUND • Cushing’s Syndrome (1932) • Harvey William Cushing • Cushing’s Syndrome affects more women than men • Characteristic type of obesity of the face, neck, and trunk

  4. The adrenal cortex is under the control of the pituitary gland • IN HEALTH • Releasing hormone from the hypothalamus. • ACTH production from the anterior pituitary. • Glucocorticoids from the adrenal cortex

  5. CUSHING’S SYNDROME • The hypothalamic/pituitary axis is disturbed • Hormonal disorder caused by chronic glucocorticoid excess • Disorder in which the body tissue is exposed to excess levels of the hormone cortisol • Most common type of cushing’s syndrome is caused by exposure to high levels of ACTH

  6. SIGNS/SYMPTOMS • Facial obesity (“Moon Face”) • Fatty swellings (“Buffalo Hump”) • Weight gain w/ rounding of the face • Increased fat in the neck • Bruising of the skin • Muscle weakness • Osteoporosis • High blood sugar • Diabetes • High blood pressure

  7. SIGNS/SYMPTOMS

  8. SIGNS/SYMPTOMS

  9. DIAGNOSIS • Biochemical laboratory test • Dexamethasone suppression test (DST) • ACTH stimulation test

  10. TREATMENTS • Bromocriptine Mesylate • 5 mg capsule • Dopamine agonist • Known to be the original drug to treat this disorder • Decreases ACTH & cortisol levels

  11. POSSIBLE SIDE EFFECTS • Mild nausea • Vomiting • Abdominal cramps • Diarrhea or constipation • Dizziness or drowsiness • Dry mouth • Nasal stufness • Headache

  12. Development Of Cushing’s Syndrome In Corticotropin-Releasing Factor Transgenic Mice. Stenzel-Poore, M.P., V.A. Cameron, J. Vaughan, P.E. Sawchenko, and W. Vale. 1992. Development of Cushing’s Syndrome in Corticotropin-Releasing factor Transgenic Mice. Endocrinology 130: 3378-3386.

  13. What Is CRF? • Corticotropin-Releasing Factor (CRF) is a 41-residue hypothalamic peptide • CRF is synthesized in the hypothalamus and regulates adrenocorticotropic hormone (ACTH) secretion & glucocorticoid production from the posterior pituitary • CRF plays a major role in behavioral responses to stress and acts as a neurotransmitter in extra-hypothalamic systems • The overproduction of CRF leads to disorders such as depression, anorexia nervosa, and Cushing’s Syndrome

  14. Objective • To examine the endocrine and behavioral effects of chronic CRF excess that leads to Cushing’s Syndrome • To develop a transgenic mouse model that overexpress CRF of chronic pituitary-adrenal activation

  15. Rationale • CRF transgenic animals display endocrine abnormalities such as high plasma levels of ACTH & constant elevated levels of circulating glucocorticoid in the hypothalamic-pituitary adrenal (HPA) axis • The founder animals with high levels of circulating CRF show truncal obesity with large adipose deposits, muscle wasting, bilateral symmetric hair loss, and abnormal transparent skin

  16. Generation of MT-CRF Mice With Cushing’s Syndrome • The transgenic male animal on the left expresses high levels of CRF with elevated ACTH release and increase corticosterone production and shows features of Cushing’s Syndrome with decreased linear growth, bilateral hair loss, and increased fat accumulation • The non-transgenic control littermate on the right shows no signs of Cushing’s Syndrome

  17. Generation of MT-CRF Mice With Cushing’s Syndrome

  18. Generation of MT-CRF Mice With Cushing’s Syndrome • Murine Metallothionein-1 (m MT-1) gene promoter was used to avoid feedback regulation of the CRF transgene expression • Metallothionein-CRF (MT-CRF) gene extends from the Asp718 site in the 5’ untranslated region to the EcoRI site in the 3’ untranslated region

  19. Generation of MT-CRF Mice With Cushing’s Syndrome

  20. ACTH and Corticosterone Levels in CRF Transgenic Mice • Basal levels of ACTH and Corticosterone were measured in serum obtained from offspring derived from a single family • ACTH values were 5-fold greater than control nontransgenic animals. This increase can stimulate the secretion of corticosterone from the adrenal glands • In transgenic offspring, corticosterone levels were 10-fold greater than the baseline control

  21. ACTH and Corticosterone Levels in CRF Transgenic Mice

  22. CRF gene expression in peripheral tissues of MT-CRF transgenic mice • Stenzel-Poore and colleagues were able to determine the tissue distribution of the CRF gene expression because the transgenic animals displayed high plasma ACTH levels without an increase in plasma CRF

  23. CRF gene expression in peripheral tissues of MT-CRF transgenic mice

  24. CRF gene expression in peripheral tissues of MT-CRF transgenic mice

  25. CRF gene expression in peripheral tissues of MT-CRF transgenic mice

  26. CRF in transgenic mouse brains using a rat CRF cRNA probe

  27. CRF in transgenic mouse brains using a rat CRF cRNA probe

  28. CRF in transgenic mouse brains using a rat CRF cRNA probe

  29. A transgene-specific oligonucleotide probe was used to verify the expression of the CRF transgene in regions where high levels of CRF expression were observed • This transgene-specific oligonucleotide probe exposed a hybridization pattern that was similar to the rat gene CRF probe • In other words, the regions of heightened expression were due to the transgene

  30. Transgene-specific oligonucleotide in transgenic mouse brain

  31. Transgene-specific oligonucleotide in transgenic mouse brain

  32. Conclusion • Cushing’s Syndrome is due to chronic glucocorticoid excess and exposure to high levels of ACTH • CRF is released in the hypothalamus as a neuromodulator, regulates ACTH secretion, and plays a major role in stress responses

  33. References • Stenzel-Poore, M.P., V.A. Cameron, J. Vaughan, P.E. sawchenko, and W. Vale. 1992. Development of Cushing’s Syndrome in Corticotropin-Releasing Factor transgenic Mice. Endocrinology 130: 3378-3386. • Orth, D.N. 1992. Cushing’s Syndrome. Medical Progress 332: 791-803. • Shaw, G. Spring 2003. Lecture Notes. Endocrinology.

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