Preventive carnosine supplementation attenuates painful diabetic neuropathy via restoring mitochondrial function and suppressing inflammasome activation

Figure 3 The impact of intraperitoneal injection of carnosine on behavioral, electrophysiological, ultrastructural, and neuronal functional abnormalities in painful diabetic neuropathy rats. ^aP < 0.05, ^bP < 0.01, ^cP < 0.001 vs the control group; ^dP < 0.05, ^eP < 0.01, ^fP < 0.001 vs the painful diabetic neuropathy group. Two-way analysis of variance with Sidak’s multiple comparisons test for Figure 3B-E. One-way analysis of variance with Tukey’s multiple comparisons test for Figure 3F, H, and N; Linear mixed-effects models were used for statistical analyses of data shown in panels Figure 3K-M, with animal ID designated as the random intercept to account for clustered microscopic observations nested within individual rats. Bonferroni-adjusted pairwise comparisons were performed for intergroup comparisons across the three experimental groups. Figure 3B-F: n = 11; Figure 3G and H: n = 3; Figure 3I-M: n = 3 rats per group, with at least 50 mitochondria counted in 3 random fields per sample. For Figure 3K and L, each field was the statistical unit; for Figure 3M, each individual mitochondrion was the statistical unit for mitochondrial length quantification; Figure 3N: n = 8. A: Flowchart of the experiments; B: Changes in body weight after intraperitoneal carnosine injection; C: Changes in blood glucose level following intraperitoneal carnosine injection; D: Paw withdrawal threshold in rats post-intraperitoneal carnosine injection; E: Paw withdrawal latency in rats post-intraperitoneal carnosine injection; F: Motor nerve conduction velocity and sensory nerve conduction velocity in rats following intraperitoneal carnosine injection; G and H: Results of whole-cell patch-clamp recordings at week 3 after streptozotocin injection; G: Representative traces of neuronal action potential; H: Statistical analysis of the action potential number in dorsal root ganglia (DRG) neurons of rats (n = 3); I: Ultrastructural changes of the DRG post-intraperitoneal carnosine injection. Scale bar = 2 μm; J: Alterations in mitochondrial structure in the DRG post-intraperitoneal carnosine injection. Scale bar = 500 nm; K: The number of mitochondria per field; L: Proportion of abnormal mitochondria relative to the total mitochondrial count; M: Mitochondrial length; N: Changes in mitochondrial membrane potential in the DRG following intraperitoneal carnosine injection. PDN: Painful diabetic neuropathy; MNCV: Motor nerve conduction velocity; SNCV: Sensory nerve conduction velocity; STZ: Streptozotocin.