Characterisation of the androgen dependent phenotype

Rodie, Martina Elizabeth (2017) Characterisation of the androgen dependent phenotype. PhD thesis, University of Glasgow.

Abstract

The effects of androgens reach far and wide and can be physiological as well as pathological. They are not limited to males and involve almost every system in the human body. Their influence on reproductive development and behaviours is well studied, but more recently, attention has turned to the wider reaching consequences of androgen exposure. Disorders of sex development (DSD) are rare conditions in which individuals may be deficient in, or resistant to, the effects of androgens. The long-term health and quality of life for these individuals is not well reported, but where there are reports, there are descriptions of increased depressive like behaviours, anxiety and poor social functioning. Lack of androgens has been linked to poorer neurocognitive outcomes in some studies and there is a concern that more aggressive hormone replacement should be considered in early life for those individuals lacking in androgens. These disorders can be difficult to study for many reasons. Firstly, they are rare conditions. Secondly, adults with DSD do not tend to visit hospital regularly and can therefore be challenging to engage in research. Thirdly, studying the effects of early life exposure to steroid hormones and relating these to later life behaviours is incredibly complex.
Animal models have been used for many years to study the hormonal environment. For my first study, I used a model of rodent neonatal androgen blockade by treating pups with the anti-androgen flutamide for the first five days of life. The animals were studied again in adolescence (6 weeks of age) and early adulthood (10 weeks of age). There were no significant differences found in testosterone, dihydrotestosterone and androstenedione levels in either age group, demonstrating that the androgen blockade was transient. The anogenital index (AGI) was significantly shorter in the treated animals when compared to controls at 6 weeks of age and 10 weeks of age. Phallus length was significantly shorter in treated males when compared to the healthy males at 6 weeks of age and at 10 weeks of age. Phallus weight was significantly lower in the treated animals at 10 weeks of age when compared to the healthy animals. This work demonstrated that my rodent model of neonatal androgen blockade was an effective one.
My next study used the same rodent model and aimed to link the perinatal hormonal environment with in vivo brain chemistry using a painless, non-invasive technique known as Magnetic Resonance Spectroscopy. Using a mixed effects model, I analysed the effects of sex, gender, treatment with flutamide and age on the metabolite pattern of the rodent brain. Ɣ-aminobutyric acid (GABA), glucose, glutamine, glutamate, phosphocholine and myo-inositol all changed over time. The combined peaks of glutamate and glutamine also demonstrated a significant change over time. GABA, glutamate, phosphocholine and myo-inositol showed significant sex differences as did the combined peaks of glycerophosphocholine and phosphocholine, N-acetylaspartate (NAA) and N-acetylaspartylglutamate (NAAG) and glutamate and glutamine. Aspartate, GABA and myo-inositol were all significantly changed by treatment of the animals with flutamide and GABA and myo-inositol levels in treated males were similar to control females at both 6 and 10 weeks.
My final study using the rodent model of androgen blockade looked at the histological changes in the brain. Brains were sectioned and stained for neuronal cell counts and microglial cell counts, and PCR for the Androgen Receptor (AR) was performed. I demonstrated significant, sexually dimorphic changes in neuronal cell counts, microglial cell counts and androgen receptor expression in two clearly defined areas in the rodent brain. In summary, my rodent work demonstrated a link between the neonatal hormonal environment and the sexually dimorphic chemistry and histology of the in vivo brain, and supports the hypothesis that the microglial cell plays a critical role in brain masculinisation.
To include a translational aspect to this thesis I extended my work to a population of undermasculinised boys, who were attending hospital for an hCG stimulation test as part of their investigations for 46 XY DSD. The hCG stimulation test is a valuable method for assessing androgen production but there is a need to explore its utility in assessing androgen responsiveness and long-term prognosis. I aimed to assess the effects of the hCG test on the in vivo brain chemistry using MRS, and the peripheral transcriptome using microarray. I reliably demonstrated metabolites in the brains of healthy male infants, healthy female infants and affected male infants. Healthy male infants had significantly lower levels of N-acetylaspartate than affected males in the hypothalamus and lower levels of the phosphocholines in the frontal cortex. In my transcriptomic study of DSD patients, I demonstrated the existence of an androgen responsive group of small RNAs that are measurable in peripheral mononuclear blood cells, and that change over the short duration of an hCG stimulation test, raising the prospect of combining the biochemical assessment of testosterone production with an objective molecular assessment of androgen sufficiency.
In summary, in this thesis I have successfully linked the early hormonal environment with later life in vivo brain chemistry, confirmed by histological studies. I have also identified a novel marker, which could potentially be used as an assessment of androgen sufficiency in the future.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: androgens, disorders of sex development, sexual dimorphism of the brain, peripheral transcriptome.
• Subjects: R Medicine > RJ Pediatrics > RJ101 Child Health. Child health services
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Medicine, Dentistry & Nursing
• Funder's Name: Yorkhill Children's Charity
• Supervisor's Name: Ahmed, Professor S. Faisal
• Date of Award: 2017
• Embargo Date: 3 November 2018
• Depositing User: Dr Martina Rodie
• Unique ID: glathesis:2017-8540
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 06 Nov 2017 16:31
• Last Modified: 16 Nov 2017 12:42
• URI: https://theses.gla.ac.uk/id/eprint/8540

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