Is serum gastrin releasing peptid activity a biomarker for renal tubulointerstitial fibrosis ?

Aim: Interstitial fibrosis/tubular atrophy (IFTA) is very important in the pathogenesis of chronic kidney disease. Gastrin-releasing peptide (GRP) is a neuropeptide that is effective in various pathophysiological processes in the body, such as increased fibroblast activity. In this study, the relationship between serum GRP (sGRP) level and the presence and severity of IFTA was examined. Materials and Methods: 49 patients [mean age 44.1±15 year and 23 (49.6%) men) who underwent kidney biopsy and 20 healthy volunteers [mean age 43.4±7.2 year and 8 (40%) men] participated in the cross-sectional study. Clinical and laboratory characteristics of all participants were recorded. sGRP level measurement was performed using Elabscience Human Pro-Gastrin Releasing Peptide ELISA Kit. Scoring system was applied according to the percentage of IFTA severity in kidney tissue samples. Results: sGRP levels were found to be significantly higher in the patient group [30.0 U/L (22.1-48.1) vs 19.7 U/L (15.1-30.3), p=0.004 (Table 4)]. However, sGRP levels were found to be lower in the group with IFTA score 1, but it did not reach statistical significance [38.5 (28.3–65.0) in IFTA scores 1, 2 and 3+4, respectively; 23.2 (19.5-48.6); 27.2 (22.2– 36.5), p=0.090, (Table 5)]. A statistically significant positive correlation was found between sGRP and proteinuria (p=0.012, Table 6), and a negative correlation that did not reach statistical significance with IFTA score (p=0.168, Table 7). Conclusion: To our knowledge, in this first study evaluating the relationship between IFTA and sGRP levels, it was shown that the level of sGRP may increase in the presence of renal injury and proteinuria, and there may be an inverse relationship between the severity of IFTA and sGRP. This contrasting relationship suggests that it may be associated with decreased fibroblast activity after the development of severe fibrosis in the tissue. Our findings reveal that IFTA severity and proteinuria and sGRP level should be evaluated with large-scale studies. Keywords: Interstitial fibrosis/tubular atrophy, Proteinuria, Chronic Kidney Disease, Serum Gastrin-Releasing Peptide