Heterozygote Advantage of the Type II Deiodinase Thr92Ala Polymorphism on Intrahospital Mortality of COVID-19

CONTEXT

The type 2 deiodinase and its Thr92Ala-DIO2 polymorphism have been linked to clinical outcomes in acute lung injury and pulmonary fibrosis.

OBJECTIVE

Our objectives were to evaluate were cumulative mortality during admission according to Thr92Ala-DIO2 polymorphism.

METHODS

Here we conducted an observational, longitudinal, and prospective cohort study to investigate a possible association between the Thr92Ala-DIO2 polymorphism and intrahospital mortality from COVID-19 in adult patients admitted between June and August 2020. Blood biochemistry, thyroid function tests, length of stay, comorbidities, complications, and severity scores were also studied according to Thr92Ala-DIO2 polymorphism.

RESULTS

In total, 220 consecutive patients (median age 62; 48-74 years) were stratified into 3 subgroups: Thr/Thr (n = 79), Thr/Ala (n = 119), and Ala/Ala (n = 23). While the overall mortality was 17.3%, the lethality was lower in Ala/Thr patients (12.6%) than in Thr/Thr patients (21.7%) or Ala/Ala patients (23%). The heterozygous genotype (Thr/Ala) was associated with a 47% reduced risk of intrahospital mortality whereas univariate and multivariate logistic regression adjusted for multiple covariates revealed a reduction that ranged from 51% to 66%. The association of the Thr/Ala genotype with better clinical outcomes was confirmed in a metanalysis of 5 studies, including the present one.

CONCLUSION

Here we provide evidence for a protective role played by Thr92Ala-DIO2 heterozygosity in patients with COVID-19. This protective effect follows an inheritance model known as overdominance, in which the phenotype of the heterozygote lies outside the phenotypical range of both homozygous.

Number, Proliferative Activity, and Expression of Thyroid Hormone Receptors in Dermal Fibroblasts in Mice with Changed Thyroid Status

We studied the intensity of age-specific changes in the dermis (number and proliferative activity of fibroblasts) in mice with normal and experimentally changed level of thyroid hormones. Receptors of thyroid hormones, TR-α and TR-β, in mouse dermal fibroblasts were identified by immunohistochemical methods. The relative expression of Thra, Thrb, and Dio2 genes was assessed by real-time PCR analysis. From the second to fifth month of life, the number of fibroblasts in the connective tissue layer of mouse skin decreased by 42.3%. The number of fibroblasts in the dermis of 5-month-old mice treated with Thyrozol significantly decreases by 25.9% (p<0.05), and vice versa, in mice receiving thyroxin this parameter increased by 4.7% in comparison with the control (p>0.05). TR-α and TR-β were identified in dermal fibroblasts in all groups of mice. No differences in the content TR-α and Thra gene expression in 2- and 5-month-old mice of the control and experimental were revealed. TR-β content in dermal fibroblasts of 2-month-old animals was maximum and exceeded this value in 5-month-old control mice by 25%. The number of these receptors decreased by 33.3% in mice treated with Thyrozol and increased by 25% in animals receiving thyroxin injection in comparison with the control. Relative expression of Thrb gene significantly increased only in mice treated with thyroxin. Comparative analysis of the relative expression of Dio2 gene revealed no differences between the experimental and control groups. Changes in the level of thyroid hormones, content of TR-β, and relative Thrb gene expression contribute to agerelated shifts in the number and proliferative activity of mouse dermal fibroblasts.

Thyrostimulin deficiency does not alter peripheral responses to acute inflammation-induced nonthyroidal illness

Thyrostimulin, a putative glycoprotein hormone, comprises the subunits GPA2 and GPB5 and activates the TSH receptor (TSHR). The observation that proinflammatory cytokines stimulate GPB5 transcription suggested a role for thyrostimulin in the pathogenesis of nonthyroidal illness syndrome (NTIS). In the present study, we induced acute inflammation by LPS administration to GPB5(-/-) and WT mice to evaluate the role of thyrostimulin in peripheral thyroid hormone metabolism during NTIS. In addition to serum thyroid hormone concentrations, we studied mRNA expression and activity of deiodinase types I, II, and III (D1, D2, and D3) in peripheral T3 target tissues, including liver, muscle, and white and brown adipose tissue (WAT and BAT), of which the latter three express the TSHR. LPS decreased serum free (f)T4 and fT3 indexes to a similar extent in GPB5(-/-) and WT mice. Serum reverse (r)T3 did not change following LPS administration. LPS also induced significant alterations in tissue D1, D2, and D3 mRNA and activity levels, but only the LPS-induced increase in WAT D2 mRNA expression differed between GPB5(-/-) and WT mice. In conclusion, lacking GPB5 during acute illness does not affect the LPS-induced decrease of serum thyroid hormones while resulting in subtle changes in tissue D2 expression that are unlikely to be mediated via the TSHR.

Exposure to monocrotophos pesticide causes disruption of the hypothalamic-pituitary-thyroid axis in adult male goldfish (Carassius auratus)

The thyroid hormones (THs) 3,3',5-triiodo-l-thyronine (T3) and l-thyroxine (T4) exert a wide range of biological effects on physiological processes of fish. To elucidate the thyroid disruption effects of monocrotophos (MCP), an organophosphate pesticide, on male goldfish (Carassius auratus), thyroid follicle histology, plasma total T3 (TT3), total T4 (TT4), free T3 (FT3) and free T4 levels, and the mRNA expression of indices involved in the hypothalamic-pituitary-thyroid axis (HPT axis) were examined following 21-day exposure to 0.01, 0.10 and 1.00mg/L of a 40% MCP-based pesticide. The results showed that MCP exposure induced the hyperplasia and hypertrophy of thyroid follicular epithelium and led to decreased plasma TT3 levels and TT3-to-TT4 ratios, without effect on plasma TT4 levels. Profiles of the changes in the relative abundance of deiodinase (D1, D2 and D3) transcripts were observed in the liver, brain and kidneys, during MCP exposure. An increase in the metabolism of T3, expressed as highly elevated hepatic d1 and d3 mRNA levels, might be associated with the reduction in plasma TT3 levels in both the 0.01 and 0.10mg/L groups, while in the 1.00mg/L MCP group, inhibited hepatic d2 transcripts might have also resulted in decreased TT3 levels by preventing the activation of T4 to T3. As a compensatory response to decreased T3 levels, pituitary thyroid-stimulating hormone β subunit mRNA transcription was up-regulated by the MCP pesticide. Decreases in plasma FT3 levels were also correlated with the modulation of hepatic transthyretin mRNA expression. Overall, the MCP pesticide exhibited thyroid-disrupting effects via interference with the HPT axis at multiple potential sites, resulting in disturbance of TH homeostasis.