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Fulltext Orbital Signaling in Graves' Orbitopathy

Draman MS, Zhang L, Dayan C, Ludgate M

Front Endocrinol (Lausanne), 2021;12:739994.
PMID: 34899596 DOI: 10.3389/fendo.2021.739994

Graves' orbitopathy (GO) is a complex and poorly understood disease in which extensive remodeling of orbital tissue is dominated by adipogenesis and hyaluronan production. The resulting proptosis is disfiguring and underpins the majority of GO signs and symptoms. While there is strong evidence for the thyrotropin receptor (TSHR) being a thyroid/orbit shared autoantigen, the insulin-like growth factor 1 receptor (IGF1R) is also likely to play a key role in the disease. The pathogenesis of GO has been investigated extensively in the last decade with further understanding of some aspects of the disease. This is mainly derived by using in vitro and ex vivo analysis of the orbital tissues. Here, we have summarized the features of GO pathogenesis involving target autoantigens and their signaling pathways.
Fulltext Role of Hyaluronan in Human Adipogenesis: Evidence from in-Vitro and in-Vivo Studies

Wilson N, Steadman R, Muller I, Draman M, Rees DA, Taylor P, et al.

Int J Mol Sci, 2019 May 31;20(11).
PMID: 31151314 DOI: 10.3390/ijms20112675

Hyaluronan (HA), an extra-cellular matrix glycosaminoglycan, may play a role in mesenchymal stem cell differentiation to fat but results using murine models and cell lines are conflicting. Our previous data, illustrating decreased HA production during human adipogenesis, suggested an inhibitory role. We have investigated the role of HA in adipogenesis and fat accumulation using human primary subcutaneous preadipocyte/fibroblasts (PFs, n = 12) and subjects of varying body mass index (BMI). The impact of HA on peroxisome proliferator-activated receptor gamma (PPARγ) expression was analysed following siRNA knockdown or HA synthase (HAS)1 and HAS2 overexpression. PFs were cultured in complete or adipogenic medium (ADM) with/without 4-methylumbelliferone (4-MU = HA synthesis inhibitor). Adipogenesis was evaluated using oil red O (ORO), counting adipogenic foci, and measurement of a terminal differentiation marker. Modulating HA production by HAS2 knockdown or overexpression increased (16%, p < 0.04) or decreased (30%, p = 0.01) PPARγ transcripts respectively. The inhibition of HA by 4-MU significantly enhanced ADM-induced adipogenesis with 1.52 ± 0.18- (ORO), 4.09 ± 0.63- (foci) and 2.6 ± 0.21-(marker)-fold increases compared with the controls, also increased PPARγ protein expression (40%, (p < 0.04)). In human subjects, circulating HA correlated negatively with BMI and triglycerides (r = -0.396 (p = 0.002), r = -0.269 (p = 0.038), respectively), confirming an inhibitory role of HA in human adipogenesis. Thus, enhancing HA action may provide a therapeutic target in obesity.
Prostaglandin F2-Alpha Eye Drops (Bimatoprost) in Graves' Orbitopathy: A Randomized Controlled Double-Masked Crossover Trial (BIMA Trial)

Draman MS, Morris DS, Evans S, Haridas A, Pell J, Greenwood R, et al.

Thyroid, 2019 04;29(4):563-572.
PMID: 30880626 DOI: 10.1089/thy.2018.0506

BACKGROUND: Previous in vitro experiments have demonstrated that prostaglandin F2-alpha (PF2α) reduced proliferation and adipogenesis in a murine cell line and human orbital fibroblasts derived from subjects with inactive Graves' orbitopathy (GO). The objective of this study was to determine if the PGF2α analogue bimatoprost is effective at reducing proptosis in this population.
METHODS: A randomized controlled double-masked crossover trial was conducted in a single tertiary care academic medical center. Patients with long-standing, inactive GO but persistent proptosis (>20 mm in at least one eye) were recruited. Allowing for a 15% dropout rate, 31 patients (26 females) were randomized in order to identify a treatment effect of 2.0 mm (p = 0.05; power 0.88). Following informed consent, participants were randomized to receive bimatoprost or placebo for three months, after which they underwent a two-month washout before switching to the opposite treatment. The primary outcome was the change in exophthalmometry readings over the two three-month treatment periods.
RESULTS: The mean exophthalmometer at baseline was 23.6 mm (range 20.0-30.5 mm), and the mean age of the patients was 55 years (range 28-74 years). The median duration of GO was 7.6 years (interquartile range 3.6-12.3 years). The majority were still suffering from diplopia (61.3%) with bilateral involvement (61.3%). Using multi-level modeling adjusted for baseline, period, and carry-over, bimatoprost resulted in a -0.17 mm (reduction) exophthalmometry change ([confidence interval -0.67 to +0.32]; p = 0.490). There was a mean change in intraocular pressure of -2.7 mmHg ([confidence interval -4.0 to -1.4]; p = 0.0070). One patient showed periorbital fat atrophy on treatment, which resolved on stopping treatment. Independent analysis of proptosis by photographic images (all subjects) and subgroup analysis on monocular disease (n = 12) did not show any apparent benefit.
CONCLUSIONS: In inactive GO, bimatoprost treatment over a three-month period does not result in an improvement in proptosis.
Fulltext Expression of Endogenous Putative TSH Binding Protein in Orbit

Draman MS, Grennan-Jones F, Taylor P, Muller I, Evans S, Haridas A, et al.

Curr Issues Mol Biol, 2021 Oct 27;43(3):1794-1804.
PMID: 34889904 DOI: 10.3390/cimb43030126

Thyroid stimulating antibodies (TSAB) cause Graves' disease and contribute to Graves' Orbitopathy (GO) pathogenesis. We hypothesise that the presence of TSH binding proteins (truncated TSHR variants (TSHRv)) and/or nonclassical ligands such as thyrostimulin (α2β5) might provide a mechanism to protect against or exacerbate GO. We analysed primary human orbital preadipocyte-fibroblasts (OF) from GO patients and people free of GO (non-GO). Transcript (QPCR) and protein (western blot) expression levels of TSHRv were measured through an adipogenesis differentiation process. Cyclic-AMP production by TSHR activation was studied using luciferase-reporter and RIA assays. After differentiation, TSHRv levels in OF from GO were significantly higher than non-GO (p = 0.039), and confirmed in ex vivo analysis of orbital adipose samples. TSHRv western blot revealed a positive signal at 46 kDa in cell lysates and culture media (CM) from non-GO and GO-OF. Cyclic-AMP decreased from basal levels when OF were stimulated with TSH or Monoclonal TSAB (M22) before differentiation protocol, but increased in differentiated cells, and was inversely correlated with the TSHRv:TSHR ratio (Spearman correlation: TSH r = -0.55, p = 0.23, M22 r = 0.87, p = 0.03). In the bioassay, TSH/M22 induced luciferase-light was lower in CM from differentiated GO-OF than non-GO, suggesting that secreted TSHRv had neutralised their effects. α2 transcripts were present but reduced during adipogenesis (p < 0.005) with no difference observed between non-GO and GO. β5 transcripts were at the limit of detection. Our work demonstrated that TSHRv transcripts are expressed as protein, are more abundant in GO than non-GO OF and have the capacity to regulate signalling via the TSHR.
Fulltext Gut Microbiome Associated With Graves Disease and Graves Orbitopathy: The INDIGO Multicenter European Study

Biscarini F, Masetti G, Muller I, Verhasselt HL, Covelli D, Colucci G, et al.

J Clin Endocrinol Metab, 2023 Jul 14;108(8):2065-2077.
PMID: 36683389 DOI: 10.1210/clinem/dgad030

CONTEXT: Gut bacteria can influence host immune responses but little is known about their role in tolerance-loss mechanisms in Graves disease (GD; hyperthyroidism caused by autoantibodies, TRAb, to the thyrotropin receptor, TSHR) and its progression to Graves orbitopathy (GO).
OBJECTIVE: This work aimed to compare the fecal microbiota in GD patients, with GO of varying severity, and healthy controls (HCs).
METHODS: Patients were recruited from 4 European countries (105 GD patients, 41 HCs) for an observational study with cross-sectional and longitudinal components.
RESULTS: At recruitment, when patients were hyperthyroid and TRAb positive, Actinobacteria were significantly increased and Bacteroidetes significantly decreased in GD/GO compared with HCs. The Firmicutes to Bacteroidetes (F:B) ratio was significantly higher in GD/GO than in HCs. Differential abundance of 15 genera was observed in patients, being most skewed in mild GO. Bacteroides displayed positive and negative correlations with TSH and free thyroxine, respectively, and was also significantly associated with smoking in GO; smoking is a risk factor for GO but not GD. Longitudinal analyses revealed that the presence of certain bacteria (Clostridiales) at diagnosis correlated with the persistence of TRAb more than 200 days after commencing antithyroid drug treatment.
CONCLUSION: The increased F:B ratio observed in GD/GO mirrors our finding in a murine model comparing TSHR-immunized with control mice. We defined a microbiome signature and identified changes associated with autoimmunity as distinct from those due to hyperthyroidism. Persistence of TRAb is predictive of relapse; identification of these patients at diagnosis, via their microbiome, could improve management with potential to eradicate Clostridiales.