Supplementary Material for: Association of Copeptin, a Surrogate Marker of Arginine Vasopressin, with Decreased Kidney Function in Sugarcane Workers in Guatemala

<b><i>Background:</i></b> Vasopressin is elevated in response to heat and dehydration and has been postulated to have a role in the chronic kidney disease of unknown origin being observed in Central America. The aims of this study were to examine whether the vasopressin pathway, as measured by copeptin, is associated with the presence of kidney dysfunction, and to examine whether higher fluid intake is associated with lower circulating copeptin and thereby preserves kidney health among sugarcane workers exposed to hot conditions. <b><i>Methods:</i></b> Utilizing a longitudinal study of 105 workers in Guatemala, we examined relationships between hydration indices, plasma copeptin concentrations, and kidney function markers at 3 times during the 6-month harvest. We also examined whether baseline copeptin concentrations increased the odds of developing an estimated glomerular filtration rate (eGFR) &lt;60 mL/min/1.73 m². <b><i>Results:</i></b> Copeptin concentrations were positively associated with serum creatinine (β 1.41, 95% CI 0.88–2.03) and negatively associated with eGFR (β –1.07, 95% CI –1.43 to –0.70). In addition, as workers improved their hydration (measured by increases in fluid balance), copeptin concentrations were reduced, and this reduction was associated with an improvement in kidney function. <b><i>Conclusions:</i></b> Results suggest that copeptin should be studied as a potential prognostic biomarker.

<b><i>研究背景：</i></b> 加压素（vasopressin）可因受热与脱水而升高，现有假说认为其在中美洲地区检出的不明原因慢性肾病的发生中发挥作用。本研究旨在明确两个问题：其一，通过copeptin（copeptin）检测的加压素通路是否与肾功能不全的发生相关；其二，在高温环境下作业的甘蔗工人中，较高的液体摄入量是否与更低的循环copeptin水平相关，进而维持肾脏健康。<b><i>研究方法：</i></b> 本研究针对危地马拉的105名工人开展一项纵向队列研究，在为期6个月的甘蔗收获期内的3个时间点，分析水化指标、血浆copeptin浓度与肾功能标志物之间的关联。同时本研究还评估了基线copeptin浓度是否会升高发展为估算肾小球滤过率（eGFR）<60 mL/min/1.73 m²的比值比。<b><i>研究结果：</i></b> Copeptin浓度与血清肌酐呈正相关（β=1.41，95%置信区间：0.88~2.03），与eGFR呈负相关（β=-1.07，95%置信区间：-1.43~-0.70）。此外，随着工人水化状态改善（以体液平衡增加量评估），copeptin浓度随之降低，且该降低与肾功能改善相关。<b><i>研究结论：</i></b> 本研究结果提示，可将copeptin作为潜在的预后生物标志物开展进一步研究。