Abstract
Prevalence of thyroid dysfunction and its impact on cognition in older people has been demonstrated, but many points remain unclarified. In order to study the effect of aging on the thyroid gland, we compared the thyroid gland of very old mice with that of younger ones. We have first investigated the changes of thyroid microstructure and the possibility that molecules involved in thyroid function might be associated with structural changes. Results from this study indicate changes in the height of the thyrocytes and in the amplitude of interfollicular spaces, anomalous expression/localization of thyrotropin, thyrotropin receptor, and thyroglobulin aging. Thyrotropin and thyrotropin receptor are upregulated and are distributed inside the colloid while thyroglobulin fills the interfollicular spaces. In an approach aimed at defining the behavior of molecules that change in different physiopathological conditions of thyroid, such as galectin-3 and sphingomyelinase, we then wondered what was their behavior in the thyroid gland in aging. Importantly, in comparison with the thyroid of young animals, we have found a higher expression of galectin-3 and a delocalization of neutral sphingomyelinase in the thyroid of old animals. A possible relationship between galectin-3, neutral sphingomyelinase, and aging has been discussed.
Highlights
Galectins are a family of proteins with specific domains of 130 amino acids able to bind β-galactosides [1]. 15 mammalian galectins are classified into three groups: prototype galectins, tandem galectins, and chimera-type group, of which galectin-3 (Gal-3) is the only member [2]
Our results demonstrated that the aging induces an increase of TSH receptor (TSHR) with disordered localization in the thyrocytes, within the follicles, and in the interfollicular spaces (Figure 2(b))
We found that the level of Gal-3 is increased in old animals and especially it is abundant in colloid (Figure 4)
Summary
Galectins are a family of proteins with specific domains of 130 amino acids able to bind β-galactosides [1]. 15 mammalian galectins are classified into three groups: prototype galectins, tandem galectins, and chimera-type group, of which galectin-3 (Gal-3) is the only member [2]. Gal-3 is known to modulate many immune reactions [4]. It can be released extracellularly under different inflammatory stimuli like lipopolysaccharide, known to induce upregulation of Gal-3 expression [5]. Gal-3 plays a role in leukocyte recruitment to the inflamed microcirculation [6]. Recent evidence shows that Gal-3 plays a role in numerous pathologic conditions such as inflammation [7], metabolic disorders [8], and cancer [9]. The microgravity induces the upregulation of Gal-3 in thyrocytes as well as its release in colloid [11]
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