Serum Levels of Cystatin C, BUN, and Creatinine in Two Different Protocols of Endurance and Speed Trainings in Healthy Young Men

IntroductionKidneys play an important role in controlling body fluid volume, plasma osmolarity, and electrolytes. Clinically, the serum level of blood urea nitrogen (BUN) and creatinine (Cr) are the most common indicators to assess glomerular filtration rate (GFR). However, these parameters are influenced by age, gender, body mass, race, and diet; especially in athletes. The serum level of cystatin C (Cys-C) is another biomarker proposed to evaluate the kidney function (Grubb, 2000,;Mingels, et al., 2009) because Cys-C negatively correlates with GFR. Cys-C is a non-glycosilated basic single chain protein produced by all nucleated cells into the blood circulation (Newman, 2002). Like inulin, it is freely filtered into the Bowman's capsule and is not reabsorbed by renal tubules. It is reported that serum level of Cys-C is not influenced by age, gender, body mass, race, and diet, and possibly its accuracy to evaluate the kidney function is higher than BUN and Cr(Newman, 2002). Furthermore, there are some interaction effects between exercise and kidney functions, and this interaction is extremely important to set up suitable training protocols. The renal hemodynamics and functions are influenced by duration and intensity of exercise (Poortmans, et al., 1997). The serum levels of Cr and urea remain almost unchanged in prolonged physical exercise (Gerth, et al., 2002). Hong and Lien examined 16 athletes before and after four weeks of boring training, and the BUN concentration increased significantly (Hong & Lien, 1984). The levels of creatine kinase (CK) and BUN were studied before and after exercise in badminton athletes, and CK not BUN increased significantly (Yang, 2007). Increase of lactate, glucose, Cr, and CK were also detected in 400-meter runners (Saraslanidis, et al., 2009). The decrease of Cys-C levels after 12 weeks of regular aerobic exercise in water was observed in patients with mild renal failure (Pechter, et al., 2003). Mingels et al. showed elevated Cys-C and Cr levels after a marathon running (Mingels, Jacobs, Kleijnen, Wodzig, & Dieijen-Visser, 2009). The effects of resistance exercises on Cys-C and C-reactive protein levels in obese females was studied, indicating that the exercise protocol has no effect on the concentrations of Cys-C and C-reactive protein (Hooseini- Kakhak, et al., 2009). It seems that exercise protocol and its intensity are the most important parameters to change the kidney function diagnostic biomarkers. In this study, we designed two different protocols of endurance and speed exercises, applied on healthy young men, and we attempted to determine the effect of endurance and speed exercises on serum levels of BUN, Cr, BUN/Cr ratio, and Cys-CMethods and ParticipantsThe experimental procedures were in advance approved by the Isfahan University of Medical Sciences and University of Isfahan Ethics Committees. Accordingly, all experimental procedures step by step were explained to the participants before the study. Those participants who accepted the experimental procedures were included. The participants were also allowed to discontinue the experimental procedures whenever they desired. Twenty healthy young male volunteer (age: 21 ±0.35 years, height: 173.9 ± 0.83 cm, and weight: 67± 1.5 kg) were selected from the general population. The body mass index (BMI) was determined (21.76 ± 0.70 kg/m2), and the participants were randomly divided into two groups with endurance (group 1, n =11) and speed (group 2, n =9) exercises protocols. The duration of training for each group was six weeks. Each exercise protocol consists of two acute sessions at the beginning and at the end of the six-week training. Training performed in three sessions per week, with a day's rest between the sessions. All acute sessions for both groups were held in the same weather conditions. Participants were prevented from exercise for three days, and then the first blood sample was obtained in the morning as before exercise sample (T0). …