Both hyperthermia and dehydration during physical work in the heat contribute to the risk of acute kidney injury

Abstract

Occupational heat stress increases the risk of acute kidney injury (AKI) and kidney disease. This study tested the hypothesis that attenuating the magnitude of hyperthermia (i.e., increase in core temperature) and/or dehydration during prolonged physical work in the heat attenuates increases in AKI biomarkers. Thirteen healthy adults (3 women, 23 ± 2 yr) exercised for 2 h in a 39.7 ± 0.6°C, 32 ± 3% relative-humidity environmental chamber. In four trials, subjects received water to remain euhydrated (<i>Water</i>), continuous upper-body cooling (<i>Cooling</i>), a combination of both (<i>Water + Cooling</i>), or no intervention (<i>Control</i>). The magnitude of hyperthermia (increased core temperature of 1.9 ± 0.3°C; <i>P</i> < 0.01) and dehydration (percent loss of body mass of -2.4 ± 0.5%; <i>P</i> < 0.01) were greatest in the <i>Control</i> group. There were greater increases in the urinary biomarkers of AKI in the <i>Control</i> trial: albumin (increase of 13 ± 11 μg/mL; <i>P</i> ≤ 0.05 compared with other trials), neutrophil gelatinase-associated lipocalin (NGAL) (increase of 16 ± 14 ng/dL, <i>P</i> ≤ 0.05 compared with <i>Cooling</i> and <i>Water + Cooling</i> groups), and insulin-like growth factor-binding protein 7 (IGFBP7) (increase of 227 ± 190 ng/mL; <i>P</i> ≤ 0.05 compared with other trials). Increases in IGFBP7 in the <i>Control</i> trial persisted after correcting for urine production/concentration. There were no differences in the AKI biomarker tissue inhibitor of metalloproteinase 2 (TIMP-2) between trials (<i>P</i> ≥ 0.11). Our findings indicate that the risk of AKI is highest with greater magnitudes of hyperthermia and dehydration during physical work in the heat. Additionally, the differential findings between IGFBP7 (preferentially secreted in proximal tubules) and TIMP-2 (distal tubules) suggest the proximal tubules as the location of potential renal injury.<b>NEW & NOTEWORTHY</b> We demonstrate that the risk for acute kidney injury (AKI) is higher in humans with greater magnitudes of hyperthermia and dehydration during physical work in the heat and that alleviating the hyperthermia and/or limiting dehydration equally reduce the risk of AKI. The biomarker panel employed in this study suggests the proximal tubules as the location of potential renal injury.