Sialic acids (Sias) are a family of electronegatively charged nine-carbon monosaccharides containing a carboxylic acid, mostly found as terminal residues in glycans of glycoproteins and glycolipids. They are bound to galactose or N-acetylgalactosamine via α2,3 or α2,6 linkage, or to other Sias especially via α2,8 linkage, which results in monomeric, oligomeric, and polymeric forms. Sias play determinant roles in a multitude of biological processes in human tissues from development to adult life until aging. In this review, we summarized the current knowledge on the sialylation status in the human testis with a main focus on sexually mature life and aging, when this organ shows significant morphofunctional changes resulting into variations of hormonal levels, as well as changes in molecules involved in mitochondrial function, receptors, and signaling proteins. Evidence suggests that Sias may have crucial morphofunctional roles in the different testicular components during the sexually mature age. With advancing age, significant loss of Sias and/or changes in sialylation status occur in all the testicular components, which seems to contribute to morphofunctional changes characteristic of the aging testis. Based on the current knowledge, further in-depth investigations will be necessary to better understand the mechanistic role of Sias in the biological processes of human testicular tissue and the significance of their changes during the aging process. Future investigations might also contribute to the development of novel prophylactic and/or therapeutic approaches that, by maintaining/restoring the correct sialylation status, could help in slowing down the testis aging process, thus preserving the testicular structure and functionality and preventing age-related pathologies.

中文翻译：

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成人睾丸在性成熟和衰老过程中唾液酸化状态及其与形态功能变化的关系：叙述性综述

唾液酸 (Sias) 是一类带负电的九碳单糖，含有羧酸，主要作为糖蛋白和糖脂聚糖的末端残基存在。它们通过 α2,3 或 α2,6 连接与半乳糖或 N-乙酰半乳糖胺结合，或者特别是通过 α2,8 连接与其他 Sias 结合，从而形成单体、寡聚和聚合形式。Sias 在人体组织从发育到成年直至衰老的多种生物过程中发挥着决定性作用。在这篇综述中，我们总结了目前关于人类睾丸唾液酸化状态的知识，主要关注性成熟和衰老，此时该器官表现出显着的形态功能变化，导致激素水平的变化，以及参与激素水平变化的分子的变化。线粒体功能、受体和信号蛋白。有证据表明，在性成熟年龄期间，Sias 可能在不同睾丸成分中发挥重要的形态功能作用。随着年龄的增长，所有睾丸成分中都会出现 Sias 的显着丧失和/或唾液酸化状态的变化，这似乎导致了衰老睾丸特征的形态功能变化。基于现有知识，需要进一步深入研究，以更好地了解 Sias 在人体睾丸组织生物学过程中的机制作用及其在衰老过程中变化的意义。未来的研究也可能有助于开发新的预防和/或治疗方法，通过维持/恢复正确的唾液酸化状态，可以帮助减缓睾丸衰老过程，从而保留睾丸结构和功能并预防与年龄相关的病变。