2.3.8. Summary of Changes in uKIM-1

uKIM-1 was increased after all exercises, but when normalized to uCr, it was unchanged. The changes in uKIM-1 were long-lasting, uKIM-1 was elevated 2 days after a marathon [46] and 9 days after an 80 km run [51]. At the same time, uNGAL decreased more rapidly.

#### 2.3.9. Changes in Urinary L-FABP after Exercise

L-FABP belongs to the fatty acid-binding protein superfamily and has a molecular mass of about 14 kDa. The function of the members of the FABP family is the regulation of fatty acids uptake and the intracellular transport. L-FABP binds fatty acids and transports them to the mitochondria and peroxisomes. L-FABP also protects renal cells from oxidative stress [8]. The urinary L-FABP level is correlated with the peritubular capillary flow and ischemia. It appears to be a promising biomarker for both the diagnosis and prediction of AKI and its outcomes among critically ill patients [5,8,9]. L-FABP is localized in the proximal tubule and secreted into urine in response to a number of different intrarenal stresses, such as proteinuria, hypoxia, hyperglycemia, hypertension and oxidative stress [37,53,54].

Only two studies in healthy populations concerning changes in uL-FABP after exercise have been published. uL-FABP was significantly increased after incremental short maximal exercise on a cycling ergometer in a group of 116 adults of variable age (24–83 years) in a study published by Kosaki et al. In this experiment, uL-FABP/uCr changes were independently correlated with albuminuria, which supported previous observations that protein overload in the proximal tubule may cause an increase in uL-FABP [53]. After short exercise (one leg calf-rise exercise), Kanda et al. did not find any changes in uL-FABP [37].
