Advances in probiotic research reveal that Lactobacillus johnsonii may reduce serum creatinine levels and renal fibrosis area in CKD rats—potentially reversing CKD progression—by elevating serum indole-3-carboxaldehyde (IAld) and inhibiting aryl hydrocarbon receptor (AhR) pathway nuclear translocation (96). This evidence concerns the gene AHR and renal fibrosis.