Zinc: the Other Suspected Environmental Factor in Kashin-Beck Disease in Addition to Selenium

Kashin-Beck disease (KBD) is an endemic chronic osteochondral disease characterized by high prevalence, disability, and morbidity and is distributed from the northeast to the southwest in China, in some regions of Eastern Siberia in Russia, and in North Korea. Although the selenium deficiency etiological hypothesis for KBD has been proposed by scientists for decades, the idea that selenium deficiency is one of the most important environmental factors but not the primary and sole pathogenic factor for KBD has been widely accepted. Zn²⁺, which is closely involved in the synthesis of enzymes, nucleic acids, and proteins, is an essential microelement in vivo. A conundrum still exists in research on the relationship between Zn²⁺ and KBD due to inconsistent results, but it has been confirmed that Zn²⁺ can help repair metaphyseal lesions in patients with KBD, indicating that Zn²⁺ might play a key role in the pathogenesis of KBD, although the mechanism is unknown. The zinc-ZIP8-MTF1 axis in chondrocytes forms a catabolic cascade that promotes upregulation of the crucial effector matrix-degrading enzymes MMP3, MMP13, and ADAMTS5, thereby leading to osteoarthritis (OA) cartilage destruction. Zinc finger protein-related genes, the ZNT family, and the ZIP family of Zn²⁺ transporter genes have been found to be differentially expressed in KBD by high-throughput screening. Therefore, Zn²⁺ could play a key role in the pathogenesis of KBD.