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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - THYRAGE (Resetting the THYRoid axis for prevention of AGE-related diseases and co-morbidities)

Teaser

Summary

We hypothesize that inappropriate thyroid hormone action in target cells is a common mechanism underlying susceptibility to age-related degenerative diseases and co-morbidities. Although regulation of systemic thyroid status is well understood and underpins treatment of common thyroid disease, it is only in the last decade that the importance of local regulation of thyroid hormone action in tissue development, homeostasis and repair has been identified. During evolution, this complex temporal and cell-specific regulation has been optimized for development and reproductive fitness but NOT for ageing. Humans with their exceptional longevity are thus exposed to a prolonged period of suboptimal local thyroid hormone action. Consistent with this, thyroid status is a continuous variable within the population that is related to fracture risk, muscle mass and cognitive decline. Moreover, in healthy longevity thyroid status is characterized by thyroid stimulating hormone in the upper half of the reference range. In these studies, we will determine how local regulation of thyroid hormone action controls tissue homeostasis and repair, whilst its dysregulation is a common mechanism underlying chronic disease development during ageing. We focus on osteoporosis, osteoarthritis, neuro-degeneration and sarcopenia as paradigm age-related, degenerative disorders whose rising prevalence and frequent co-occurrence in a single individual impose an increasing social and economic burden on European Societies. Using cutting-edge technology, our overall objectives are to (i) identify thyroid hormone dependent biomarkers for disease susceptibility in bone, cartilage, central nervous system and skeletal muscle, (ii) manipulate cell-specific thyroid hormone action in these tissues and (iii) develop cell-type specific modulators of thyroid hormone action.

Work performed

By bringing together academic and industrial experts, THYRAGE will integrate and manage clinical research, basic science and drug development. Using methods that are all well established in the laboratories of THYRAGE consortium partners, proof-of-principle studies comprise: (i) Manipulation of thyroid status, (ii) Cell-specific manipulation of thyroid hormone action, and (iii) Cell-specific delivery of thyroid hormone derivatives.

Human studies will assess the effect of manipulation of thyroid status on circulatory markers of tissue maintenance and repair. To test the hypothesis that the thyroid gland of members from long-lived families is less responsive to thyroid stimulating hormone (TSH) compared to the thyroid gland of controls, a challenge study with a low dose of recombinant human TSH has been performed for which a total of 30 participants has been included. To test whether thyroid hormone clearance is higher in members from long-lived families compared to controls, we also performed a challenge study with thyroid hormone, for which a total of 27 participants has been included. For both challenge studies recruitment has been completed, biomaterials are stored, and measurements of circulatory parameters of thyroid status are currently being performed. Human studies will be complemented by experiments in adult mice treated with methimazole and perchlorate supplemented with different doses of a combination of T4 and T3 in drinking water to render animals borderline hypothyroid or hyperthyroid, respectively, thereby mimicking individuals with thyroid status at extremes of the population reference range. Required protocols have been developed and distributed among consortium partners.

In mouse models, we will use inducible cell-specific gene targeting approaches to manipulate cell-specific thyroid hormone action in adult bone, cartilage and skeletal muscle and determine the consequences in established provocation models of osteoporosis, osteoarthritis, and sarcopenia. Similarly, non-viral transfection of short hairpin RNA will employed to manipulate cell-specific thyroid hormone action in the neural stem cell niche to determine the consequences in established provocation models of neurodegenerative disease. For all required procedures, technical staff have been trained. Mouse crosses have commenced, treatment protocols have been optimized, and rapid-throughput phenotyping methods have been validated. For studies examining the role of TH in bone and cartilage, administration of tamoxifen 175mg/kg by oral gavage has been identified as the optimal dosing regime for cell-specific inducible studies using both Agc1-CreERT2 and Col1-CreERT2 strains. Studies examining the role of TH in the neural stem cell niche indicate that thyroid hormone signalling is preferentially required for neural stem cell commitment towards neuronal precursor cells (while the absence of that thyroid hormone signalling favours commitment towards oligodendrocyte precursor cells).In line, the neuronal lineage was found to be more sensitive to brain hypothyroidism induced by the absence TH transporters (Mct8/Oatp1c1 DKO mice) than the oligodendroglial lineage. Moreover, the TH-distributor protein Transthyretin (TTR) was found to be a crucial effector of TH signalling-driven NSC fate choice toward a neuronal fate. In studies examining the role of TH in skeletal muscle, it was observed that D3 overexpression in muscle resulting in reduced TH signalling in skeletal muscle myofibers was protective for muscle loss upon hind limb muscle denervation.

We have successfully developed the chemistry for stable and labile linkage of the TH-antagonist NH3 to various tissue-specific peptides (like GLP1, NPY, secretin, calcitonin, etc.) and made available to the consortium partners a first series of compounds combining NH3 with the incretin-peptide GLP1, for tissue-specific modulation of thyroid hormone action that are currently being validated in vivo as well as in

Final results

THYRAGE integrates cross-disciplinary expertise from clinical and basic scientists, endocrinologists, neuroscientists, gerontologists, and industry-based peptide scientists and links several past and current projects funded by the European Commission on healthy ageing and age-related disease. The proposed work will result in a better understanding of the role of cell-specific thyroid hormone action in the pathophysiology of osteoporosis, osteoarthritis, neurological disorders and sarcopenia. Animal studies will:

(i) identify the underlying cellular and molecular basis of disease pathogenesis
(ii) identify signalling pathways involved in thyroid hormone regulated tissue maintenance and repair
(iii) Identify putative therapeutic targets.

Human studies will allow identification of thyroid hormone dependent biomarkers for increased or reduced disease risk. The generation of a panel of markers that define individual risk susceptibility will contribute to better disease prevention, health promotion, therapy development, and the management of co-morbidities.