Protective effects of Amygdalus mongolica on rats with renal fibrosis based on serum metabolomics

Renal fibrosis (RF) is a common outcome of various progressive chronic kidney diseases (CKDs) and, thus, seriously endangers human health. As the active ingredient of Amygdalus mongolica, amygdalin inhibits RF. Furthermore, our previous studies demonstrated that n-butanol extract (BUT) and petroleum ether extract (PET), which are effective components of A. mongolica, have an anti-renal fibrosis effect. However, their potential mechanisms of action are unclear and need further verification. The aims of this study were to further investigate the effects and potential mechanisms of A. mongolica extracts in the treatment of RF. The animals were divided into the control group, RF model group, PET group and BUT group. The RF rat model was established through unilateral ureteral obstruction (UUO). Biochemical indicators, including blood urea nitrogen (BUN), serum creatinine (Scr), and hydroxyproline (HYP, a routine marker of fibrosis), and the antioxidant index (including superoxide dismutase (SOD) and malondialdehyde (MDA)) were measured to evaluate the anti-RF effects of the extracts of A. mongolica. The histomorphology of renal tissue was observed and scored by HE and Masson staining. A serum metabonomic analysis based on UPLC-Q-TOF/MS was performed to assess the changes in the metabolic profile among the different groups. The results showed that PET and BUT significantly improved tubulointerstitial damage and fibrosis by reducing the levels of Scr, BUN, HYP, and MDA and increasing the level of SOD. Moreover, no significant differences in efficacy were observed between the BUT and PET groups. According to the metabolomics analysis, seventy-four potential biomarkers were identified, and eight crucial biomarkers were further selected. These key biomarkers significantly contributed to RF progression by participating in six metabolic pathways, including pathways involved in arginine and proline metabolism, histidine metabolism, nicotinamide metabolism, pentose and glucuronate interconversion, ascorbate and aldarate metabolism, and amino sugar and nucleotide sugar metabolism. In addition, eight key biomarkers and six crucial biomarkers were restored to levels similar to those observed in controls following the treatment with PET and BUT, respectively. The outcomes of these studies demonstrate the renoprotective effects of A. mongolica extracts in rats with RF and revealed the mechanism underlying these antifibrotic effects on metabolic activity for the first time.