Effects of high-dose creatine supplementation on kidney and liver responses in sedentary and exercised rats

This study evaluated the effects of high-dose of short-termcreatine supplementation (5g.kg-1.day-1 to 1 week) and long-termcreatine supplementation (1g.kg-1.day-1 to 4-8 weeks) on kidneyand liver structure and function of sedentary and exercisedwistar rats (exercise sessions consisted of swimming at 80% ofmaximal work load supported during 5 days per week with dailysessions of 60 minutes throughout the duration of the supplementation).seventy-two animals (245 ± 5g) were divided intofour groups (n = 18): control diet sedentary (sed), creatine dietsedentary (cre), control diet exercised (exe), and creatinediet exercised (execre). histological and blood biochemicalstudies were performed after one, four, and eight weeks ofcreatine supplementation and exercise (n = 6). no differenceswere found when comparing sed, exe and execre groupsfor kidney and liver structure and function at one, four and eightweeks. however, the cre group showed higher levels ofcreatinine (1.1 ± 0.2 vs. 0.4 ± 0.1 mg.dl-1; p < 0.05), and urea (37± 3 vs. 19 ± 1 mg.dl-1; p < 0.05) when compared with all othersgroups at four and eight weeks. at eight weeks, the cre grouppresented increased levels of alt (41 ± 7 vs. 23 ± 7 u.l-1; p <0.05), ast (89 ± 6 vs. 62 ± 5 u.l-1; p < 0.05), ggt (8.0 ± 0.9vs. 3.9 ± 1.0 u.l-1; p < 0.05), and ap (125 ± 10 vs. 69 ± 9 u.l-1;p < 0.05) also when compared with all others groups. moreover,the cre group demonstrated some structural alterations indicatingrenal and hepatic damage at four and eight weeks, respectively.these results suggest that long-term creatine supplementation(up to 4-8 weeks) may adversely affect kidney and liverstructure and function of sedentary but not of exercised rats.