Development Of Cushings Syndrome In CorticotropinReleasing Factor Transgenic Mice

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Development Of Cushings 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
  Cushings Syndrome in Corticotropin-Releasing
  Factor Transgenic Mice. Endocrinology 130
  3378-3386.
• http//access.barry.edu2138/cgi/reprint/130/6/337
  8.pdf

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CONTENTS

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

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BACKGROUND

• Cushings Syndrome (1932)
• Harvey William Cushing
• Cushings Syndrome affects more women than men
• Characteristic type of obesity of the face, neck,
  and trunk

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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

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CUSHINGS 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 cushings syndrome is caused
  by exposure to high levels of ACTH

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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

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SIGNS/SYMPTOMS
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SIGNS/SYMPTOMS
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DIAGNOSIS

• Biochemical laboratory test
• Dexamethasone suppression test (DST)
• ACTH stimulation test

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TREATMENTS

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

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POSSIBLE SIDE EFFECTS

• Mild nausea
• Vomiting
• Abdominal cramps
• Diarrhea or constipation
• Dizziness or drowsiness
• Dry mouth
• Nasal stufness
• Headache

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• Development Of Cushings 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
  Cushings Syndrome in Corticotropin-Releasing
  factor Transgenic Mice. Endocrinology 130
  3378-3386.

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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 Cushings
  Syndrome

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Objective

• To examine the endocrine and behavioral effects
  of chronic CRF excess that leads to Cushings
  Syndrome
• To develop a transgenic mouse model that
  overexpress CRF of chronic pituitary-adrenal
  activation

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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

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Generation of MT-CRF Mice With Cushings 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 Cushings Syndrome with decreased
  linear growth, bilateral hair loss, and increased
  fat accumulation
• The non-transgenic control littermate on the
  right shows no signs of Cushings Syndrome

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Generation of MT-CRF Mice With Cushings Syndrome
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Generation of MT-CRF Mice With Cushings 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

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Generation of MT-CRF Mice With Cushings Syndrome
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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

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ACTH and Corticosterone Levels in CRF Transgenic
Mice
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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

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CRF gene expression in peripheral tissues of
MT-CRF transgenic mice
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CRF gene expression in peripheral tissues of
MT-CRF transgenic mice
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CRF gene expression in peripheral tissues of
MT-CRF transgenic mice
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CRF in transgenic mouse brains using a rat CRF
cRNA probe
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CRF in transgenic mouse brains using a rat CRF
cRNA probe
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CRF in transgenic mouse brains using a rat CRF
cRNA probe
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• 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

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Transgene-specific oligonucleotide in transgenic
mouse brain
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Transgene-specific oligonucleotide in transgenic
mouse brain
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Conclusion

• Cushings 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

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References

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