Analysis of differentially expressed advanced glycation end product-modified proteins in diabetic rat kidney

The objective of the study is to analyze and identify differentially expressed advanced glycation end product (AGE)-modified proteins in diabetic rat kidney tissues. A total of 60 healthy male Sprague-Dawley rats were randomly divided into the normal control group, 1-month diabetic group, and 3-month diabetic group. Two percent streptozotocin (55 kg/kg) was intraperitoneally injected to establish the diabetic rat model. AGE-modified protein concentrations in the renal tissues were measured by ELISA. The differentially expressed AGE-modified proteins in renal tissues were separated with one-dimensional electrophoresis (1-DE) Western blotting and analyzed and identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS). AGE-modified protein concentrations in the 1-month diabetic group (420.9 ± 53.0 μg/mL) and 3-month diabetic group (618.8 ± 86.1 μg/mL) were significantly higher than the control group (332.3 ± 51.4 μg/mL) (p < 0.05 and p < 0.001, respectively). AGE-modified protein concentrations in the 3-month diabetic group were higher than in the 1-month diabetic group (p < 0.001). The blood glucose levels were positively correlated with AGE-modified protein concentrations in the diabetic groups (r = 0.4303, p = 0.4303). Four differentially expressed AGE-modified proteins were separated with 1-DE Western blotting, of which the expression levels of three proteins were twofold higher in the 3-month diabetic group as compared to the control group or 1-month diabetic group. The four upregulated proteins were identified by MALDI-TOF-MS as actin, transferrin, catalase, and albumin. Non-enzyme glycosylation of proteins may affect the structure of these proteins and probably the functions and cause kidney damage in diabetic rats.