Polyporus Umbellatus Protects Against Renal Fibrosis by Regulating Intrarenal Fatty Acyl Metabolites

Abstract

Background: Chronic renal failure (CRF) results in significant dyslipidemia and profound changes in lipid metabolism. Polyporus umbellatus (PPU) has been shown to prevent kidney injury and subsequent kidney fibrosis. Methods: Lipidomic analysis was performed to explore the intrarenal profile of lipid metabolites and further investigate the effect of PPU and its main bioactive component, ergone, on disorders of lipid metabolism in rats induced by adenine. Univariate and multivariate statistical analyses were performed for choosing intrarenal differential lipid species in CRF rats and the intervening effect of n-hexane extract of PPU and ergone on CRF rats. Results: Compared with control group, decreased creatinine clearance rate indicated declining kidney function in CRF group. Based on the lipidomics, we identified 65 lipid species that showed significant differences between CRF and control groups. The levels of 12 lipid species, especially fatty acyl lipids including docosahexaenoic acid, docosapentaenoic acid (22n-3), 10,11-Dihydro-12R-hydroxy-leukotriene C4, 3-hydroxydodecanoyl carnitine, eicosapentaenoic acid, hypogeic acid and 3-hydroxypentadecanoic acid had a strong linear correlation with creatinine clearance rate, which indicated these lipid species were associated with impaired renal function. In addition, receiver operating characteristics analysis showed that 12 lipid species had high area under the curve values with high sensitivity and specificity for differentiating CRF group from control group. These changes are related to the perturbation of fatty acyl metabolism. Treatment with PPU and ergone improved the impaired kidney function and mitigated renal fibrosis. Both chemometrics and cluster analyses showed that rats treated by PPU and ergone could be separated from CRF rats by using 12 lipid species. Intriguingly, PPU treatment could restore the levels of 12 lipid species, while treatment with ergone could only reverse the changes of six fatty acids in CRF rats. Conclusion: Altered intrarenal fatty acyl metabolites were implicated in pathogenesis of renal fibrosis. PPU and ergone administration alleviated renal fibrosis and partially improved fatty acyl metabolism. These findings suggest that PPU exerted its renoprotective effect by regulating fatty acyl metabolism as a potential biochemical mechanism. Therefore, these findings indicated that fatty acyl metabolism played an important role in renal fibrosis and could be considered as an effective therapeutic avenue against renal fibrosis.

Keywords: Polyporus umbellatus; chronic renal failure; ergone; fatty acid metabolism; lipidomics; mass spectrometry; ultra-performance liquid chromatography.

FIGURE 1

Adenine led to declining renal function and changed lipid metabolic profiling in CRF rats. (A) CCr in the control and adenine-induced CRF groups. ^## p < 0.01 compared with control group. (B) PCA of two components of 2193 variables from control and adenine-induced CRF groups. (C) PCA of two components of 65 lipid species from control and adenine-induced CRF groups. (D) Clustering analysis of 65 lipid species form control and adenine-induced CRF groups. (E) Heatmap of 65 lipid species between control and adenine-induced CRF groups. Red and green indicate increased and decreased levels, respectively.

FIGURE 2

Differential lipid species were associated with fatty acid metabolism. (A) Lipid metabolic networks were constructed by using Cytoscape, Reactome, KEGG and NetPath. Adenine-induced CRF were mainly associated with fatty acid metabolism, arachidonic acid metabolism. (B) Lipid metabolite sets enrichment overview including α-linolenic acid and linoleic acid metabolism, arachidonic acid metabolism, glycerolipid metabolism, fatty acid elongation in mitochondria, fatty acid biosynthesis, fatty acid metabolism, steroid biosynthesis and bile acid biosynthesis. The size and color of each circle is based on enrichment ratio and p-values, respectively. Enrichment ratio is computed by hits/expected, where hits indicates observed hits; expected indicates expected hits.

FIGURE 3

CCr-associated with 12 lipid species were associated with impaired renal function. (A) PCA of two components of 12 lipid species from control and adenine-induced CRF groups. (B) Heatmap of 12 lipid species between control and adenine-induced CRF groups. Red and green indicate increased and decreased levels, respectively. (C) Clustering analysis of 12 lipid species between control and adenine-induced CRF groups. (D) Correlation of 12 lipid species among control and adenine-induced CRF groups.

FIGURE 4

ROC curve of differential lipid species. Analysis of PLS-DA based ROC curves of 12 lipid species in control and adenine-induced CRF groups. The associated AUC, 95% CI, sensitivity and specificity values were indicated.

FIGURE 5

Treatment with PPU and ergone improved impaired renal function. Body weight, urine volume, kidney weight index and serum creatinine levels in the control, CRF, CRF + PPU and CRF + ERG groups. ^## p < 0.01 compared with control group, ^* p < 0.05, ^** p < 0.01 compared with CRF group.

FIGURE 6

Treatment with PPU and ergone ameliorate renal fibrosis. (A) Representative images of H&E stained kidney sections from control, adenine-induced CRF, CRF + PPU, and CRF + ERG groups. Magnification, ×400. (B) Representative images of Masson’s trichrome stained kidney sections from control, adenine-induced CRF, CRF + PPU, and CRF + ERG groups. Magnification, ×200. (C) Immunohistochemical analyses with anti-α-SMA, collagen I and fibronectin antibodies of rat kidney tissues in the control, adenine-induced CRF, CRF + PPU, and CRF + ERG groups. Magnification, ×400.

FIGURE 7

Treatment with PPU and ergone improved aberrant fatty acid metabolism in CRF rats. (A) sPLS-DA of two components of 12 lipid species from control, CRF, CRF + PPU, and CRF + ERG groups. (B) Clustering analysis of 12 lipid species among control, CRF, CRF + PPU, and CRF + ERG groups. (C) Heatmap of 12 lipid species among control, CRF, CRF + PPU, and CRF + ERG groups. Red and green indicate increased and decreased levels, respectively. (D) Relative intensity analysis of 12 lipid species among the control, CRF, CRF + PPU, and CRF + ERG groups. ^# p < 0.05, ^## p < 0.01 compared with control group; ^* p < 0.05, ^** p < 0.01 compared with CRF group.