24 h severe fluid restriction increases a biomarker of renal injury in healthy males.

Abstract

Purpose: Exercise-induced hypohydration exacerbates biomarkers of renal injury, but studies isolating the effects of hypohydration without exercise have produced mixed findings. This study investigated the effects of 24-h severe fluid restriction on biomarkers of renal injury and glucose tolerance.

Methods: Fifteen males (age: 27 ± 5 y; BMI: 24.1 ± 3.8 kg/m²) completed two randomised trials, involving consuming either 40 mL/kg body mass water to maintain euhydration (EU) or severe fluid restriction via limiting water consumption to 100 mL (HYP). A standardised dry food diet was consumed in both trials (~ 300 g water). At baseline and 24 h post-baseline, nude body mass, and blood and urine samples (additional urine sample at 12 h) were collected. An oral glucose tolerance test was conducted after 24-h post-baseline measurements (n = 12).

Results: At 24 h, body mass loss (HYP: - 1.52 ± 0.34%, EU: - 0.24 ± 0.40%), plasma volume loss, serum, and urine osmolality were greater in HYP than EU (P ≤ 0.004). Osmolality-corrected urinary kidney injury molecule-1 (uKIM-1) concentrations were greater in HYP at 12 (HYP: 1.097 ± 0.587 ng/mOsm, EU: 0.570 ± 0.408 ng/mOsm; P < 0.001) and 24-h (HYP: 1.932 ± 1.173 ng/mOsm, EU: 1.599 ± 1.012 ng/mOsm; P = 0.01). There was no trial-by-time interactions for osmolality-corrected urinary neutrophil gelatinase-associated lipocalin concentrations (P = 0.781) or plasma glucose (P = 0.550) and insulin (P = 0.193) concentrations.

Conclusion: Hypohydration produced by 24-h fluid restriction increased proximal tubular injury but did not affect glucose tolerance.