Discovering the biological and clinical implications of modulating glucocorticoid action using metabolomic profiling of human plasma samples

  • Mohammad Abdulrahman Alwashih

Student thesis: Doctoral Thesis

Abstract

Background: Glucocorticoid deficiency and excess are difficult to identify because of the non-specificity of their clinical and biochemical features which are also poorly correlated with levels of circulating steroids. The lack of reliable biomarkers for glucocorticoid action makes it challenging to determine precise therapeutic needs of patients with GC-deficient or excessive conditions such as congenital adrenal hyperplasia and Cushing's syndrome, respectively. Aim: To identify the main biomarkers indicative of changes in cortisol action in healthy individuals and those with different metabolic diseases. Study design and methodology: Plasma samples were collected from three separate studies. The first study was a randomised double-blind crossover design involving 8 men with type 2 diabetes given either placebo or metyrapone + mifepristone ('glucocorticoid blockade') for 12 hours. In the second study, 20 healthy men were given metyrapone with either low or high doses of insulin, plus such a dose of hydrocortisone as to achieve low, medium or high plasma cortisol levels. Finally, plasma samples were also obtained from 119 patients with CAH receiving standard clinical care. Liquid chromatography-mass spectrometry was then employed for the metabolomic profiling of all the plasma samples, and MzMatch software was used to identify the metabolites present. Multivariate and univariate analyses were employed to determine the most reliable metabolites as biomarkers for glucocorticoid action. Results: Branched chain amino acids, bile acids and their conjugates, and free fatty acids were the main metabolite groups that were significantly altered by at least two of the three interventions. Compared to placebo, bile acids and their conjugates were significantly (p < 0.05) elevated following glucocorticoid blockade, but subsequent insulin administration significantly lowered their levels. On the other hand, high glucocorticoid dose significantly (p < 0.05) increased the levels of chenodeoxyglycocholate in patients with conginetal adrenal hyperplasia, but no effects on bile acids were observed in similarly treated healthy men. Branched chain amino acids were significantly lowered in healthy men following high insulin dose, but were significantly (p < 0.05) increased upon high hydrocortisone infusion. High BCAs levels were associated with high body mass index , and high systolic and diastolic blood pressure in pateints with conginetal adrenal hyperplasia. In contrast, L-valine, was significantly elevated following glucocorticoid blockade in patients with type 2 diabetes. A number of saturated and unsaturated fatty acids were significantly (p < 0.05) elevated following hydrocortisone infusion in healthy men, but insulin reduced their levels significantly (p < 0.05). High glucocorticoid dose in patients with conginetal adrenal hyperplasia significantly increased C15:0, C16:0 and C20:0 while C16:1 reduced. In contrast, use of insulin following glucocorticoid blockade in patients with type 2 diabetes significantly (p < 0.05) reduced levels of C12:0, C18:0 and C18:3. Conclusion: These hypothesis-free metabolomics screening studies have identified metabolites in plasma which are differentially sensitive to glucocorticoid deficiency or excess and may be useful in clinical assessment of glucocorticoid therapy.
Date of Award30 Nov 2016
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SupervisorDavid Watson (Supervisor) & Ruangelie Edrada-Ebel (Supervisor)

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