Impacts of age, type 2 diabetes, and hypertension on circulating neutrophil gelatinase-associated lipocalin and kidney injury molecule-1 after prolonged work in the heat in men

Purpose: Prolonged work in the heat increases the risk of acute kidney injury (AKI) in young men. Whether aging and age-associated chronic disease may exacerbate the risk of AKI remains unclear. Methods: We evaluated plasma neutrophil gelatinase-associated lipocalin (NGAL) and serum kidney injury molecule-1 (KIM1) before and after 180 min of moderate-intensity work (200 W/m ²) in temperate (wet-bulb globe temperature [WBGT] 16 °C) and hot (32 °C) environments in healthy young (n = 13, 22 years) and older men (n = 12, 59 years), and older men with type 2 diabetes (T2D; n = 9, 60 years) or hypertension (HTN; n = 9, 60 years). Results: There were no changes in NGAL or KIM1 concentrations following prolonged work in temperate conditions in any group. Despite a similar work tolerance, the relative change in NGAL was greater in the older group when compared to the young group following exercise in the hot condition (mean difference + 82 ng/mL; p < 0.001). Baseline concentrations of KIM1 were ~ 22 pg/mL higher in the older relative to young group, increasing by ~ 10 pg/mL in each group after exercise in the heat (both p ≤ 0.03). Despite a reduced work tolerance in the heat in older men with T2D (120 ± 40 min) and HTN (108 ± 42 min), elevations in NGAL and KIM1 were similar to their healthy counterparts. Conclusion: Age may be associated with greater renal stress following prolonged work in the heat. The similar biomarker responses in T2D and HTN compared to healthy older men, alongside reduced exercise tolerance in the heat, suggest these individuals may exhibit greater vulnerability to heat-induced AKI if work is prolonged.