Healthy and Chronic Kidney Disease (CKD) Dogs Have Differences in Serum Metabolomics and Renal Diet May Have Slowed Disease Progression

Abstract

Chronic kidney disease (CKD) is highly prevalent in dogs, and metabolomics investigation has been recently introduced for a better understanding of the role of diet in CKD. This study aimed to compare the serum metabolomic profile of healthy dogs (CG) and dogs with CKD (CKD-T0 and CKD-T6) to evaluate whether the diet would affect metabolites. Six dogs (5 females; 1 male; 7.47 ± 2.31 years old) with CKD stage 3 or 4 (IRIS) were included. CG consisted of 10 healthy female dogs (5.89 ± 2.57 years old) fed a maintenance diet. Serum metabolites were analyzed by ¹H nuclear magnetic resonance (¹H NMR) spectra. Principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) were performed to assess differences in metabolomic profiles between groups and before (CKD-T0) and after renal diet (CKD-T6). Data analysis was performed on SIMCA-P software. Dogs with CKD showed an altered metabolic profile with increased urea, creatinine, creatine, citrate, and lipids. Lactate, branched-chain amino acids (BCAAs), and glutamine were decreased in the CKD group. However, after 6 months of diet, the metabolite profiles of CKD-T0 and CKD-T6 were similar. Metabolomics profile may be useful to evaluate and recognize metabolic dysfunction and progression of CKD, and the diet may have helped maintain and retard the progression of CKD.

Keywords: metabolic profile; nutrition; renal dogs; survival; uremic toxins.

Figure 1

Expansion (−0.2–6.0 ppm) of 1D NOESY-presat ¹H NMR spectra (600 MHz, 300 K) of the serum of the evaluated groups, indicating the main detected metabolites on the different samples. (a) Spectrum of the serum of CKD dogs after being fed a renal diet for 6 months (CKD-T6) highlighting all assignments of the metabolites’ NMR signals that have been identified; (b) spectrum of the serum of CKD dogs before being fed a renal diet for 6 months (CKD-T0), showing lactate and BCAAs in lower concentrations; (c) spectrum of the serum of healthy dogs (CG), highlighting the metabolites with a lower concentration than in both CKD groups (CKD-T0 and CKD-T6).

Figure 2

Principal component analysis (PCA) of ¹H NMR data of dogs’ serum. (a) PCA score scatter plot of first principal component (PC1) versus second principal component (PC2); (b) PC1 loadings column plot of PCA, showing the main metabolites that influenced the separation; (c) PC2 loadings column plot of PCA, showing the main metabolites that influenced the separation; (d) PLS-DA score scatter plot of axis 1 versus axis 2; (e) loadings column plot of axis 1 of PLS-DA; (f) loadings column plot of axis 2 of PLS-DA, showing the main metabolites that influenced the separation. CG: control group of healthy animals; QC: quality control; CKD-T0: CKD dogs before being fed a renal diet; CKD-T6: CKD dogs after being fed a renal diet.

Figure 3

Hierarchical clustering heatmap of a targeted PLS-DA of ¹H NMR data of dogs’ serum showing the main metabolites’ average levels for each group. CG: control group (healthy animals); CKD-T0: CKD dogs before being fed a renal diet; CKD-T6: CKD dogs after being fed a renal diet.