Effects of acute hypothyroidism on plasma melatonin and Aanat and Asmt expression in the pineal gland and gonads of rats.

Autor:	Paiva RVN; Chronobiology Research Group, Department of Health Sciences, State University of Santa Cruz, Ilhéus, Brazil.; Reproduction and Endocrinology Research Center, Department of Biological Sciences, State University of Santa Cruz, Ilhéus, Brazil., Mondes PHL; Chronobiology Research Group, Department of Health Sciences, State University of Santa Cruz, Ilhéus, Brazil., Brandão BJ; Chronobiology Research Group, Department of Health Sciences, State University of Santa Cruz, Ilhéus, Brazil., Sant'Anna JN; Chronobiology Research Group, Department of Health Sciences, State University of Santa Cruz, Ilhéus, Brazil., Freire Dos Santos ME; Chronobiology Research Group, Department of Health Sciences, State University of Santa Cruz, Ilhéus, Brazil., Fighera YM; Chronobiology Research Group, Department of Health Sciences, State University of Santa Cruz, Ilhéus, Brazil., Santos LC; Reproduction and Endocrinology Research Center, Department of Biological Sciences, State University of Santa Cruz, Ilhéus, Brazil., Markus RP; Chronopharmacology Laboratory, Department of Physiology, Institute of Biosciences, University of São Paulo, São Paulo, Brazil., Fernandes PACM; Chronopharmacology Laboratory, Department of Physiology, Institute of Biosciences, University of São Paulo, São Paulo, Brazil., Silva JF; Reproduction and Endocrinology Research Center, Department of Biological Sciences, State University of Santa Cruz, Ilhéus, Brazil., Tamura EK; Chronobiology Research Group, Department of Health Sciences, State University of Santa Cruz, Ilhéus, Brazil.
Jazyk:	angličtina
Zdroj:	Frontiers in endocrinology [Front Endocrinol (Lausanne)] 2024 Aug 01; Vol. 15, pp. 1322867. Date of Electronic Publication: 2024 Aug 01 (Print Publication: 2024).
DOI:	10.3389/fendo.2024.1322867
Abstrakt:	Introduction: The reproductive system is tightly regulated by environmental and physiological signals. Melatonin, known as the hormone of darkness, plays a crucial role in regulating both the circadian and reproductive systems in mammals. Hypothyroidism is a key endocrine disorder that harms the reproductive system. Despite many studies on melatonin's effects on the reproductive system, there is conflicting information regarding melatonin synthesis modulation in hypothyroidism. The objective of this study was to investigate the modulation of plasma melatonin levels and gene expression of Aanat and Asmt in the pineal gland and gonads of rats with hypothyroidism at different times of the day. Methods: Female and male Wistar rats were divided into control and hypothyroid groups. Hypothyroidism was induced using propylthiouracil (PTU) for 15 days, rats were euthanized six hours after lights on (ZT6), before lights off (ZT11.5), and six hours after lights off (ZT18). Free thyroxine (FT4) and melatonin were quantified in plasma, and gene expressions of melatonin synthesizing enzymes ( Aanat and Asmt ) were measured in pineal and sexual organs (testis and ovary). Also, morphological analysis was performed in sexual organs. Results: The results reveal some disparities between the sexes. Hypothyroidism reduced antral and primary follicles in the ovary, and reduced the weight of testis, epididymis, and prostate. In relation to gene expression, we observed a reduction in Aanat expression in the pineal gland during the light phase (ZT6), and in males, this reduction occurred during the dark phase (ZT18). Regarding Asmt expression, there was a decrease in females also during the dark phase (ZT18). In the gonads, there was an increase in expression in both sexes at ZT11.5. Additionally, it was interesting to observe the association between FT4 levels and Asmt expression in the gonads. Conclusions: This study showed that acute hypothyroidism can affect components of the melatonergic system in gonads, particularly gene expression of melatonin synthesis enzymes ( Aanat and Asmt ) contributing to changes in reproduction organs during disease progression. These findings enhance our understanding of melatonin synthesis in the reproductive system during hypothyroidism, showing distinct responses in male and female rats, and suggest that hypothyroidism affects the circadian rhythmicity of melatonin synthesis in a sex-dependent manner. Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. (Copyright © 2024 Paiva, Mondes, Brandão, Sant’Anna, Freire dos Santos, Fighera, Santos, Markus, Fernandes, Silva and Tamura.)
Databáze:	MEDLINE
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