Ketoanalogs' Effects on Intestinal Microbiota Modulation and Uremic Toxins Serum Levels in Chronic Kidney Disease (Medika2 Study)

Abstract

Nutritional therapy (NT) is a therapeutic option in the conservative treatment of chronic kidney disease (CKD) patients to delay the start of dialysis. The aim of this study was to evaluate the specific effect of ketoanalogs (KA)-supplemented diets for gut microbiota modulation. In a previous study we observed that the Mediterranean diet (MD) and a KA-supplemented very-low-protein diet (VLPD) modulated beneficially gut microbiota, reducing indoxyl- and p-cresyl-sulfate (IS, PCS) serum levels, and ameliorating the intestinal permeability in CKD patients. In the current study, we added a third diet regimen consisting of KA-supplemented MD. Forty-three patients with CKD grades 3B-4 continuing the crossover clinical trial were assigned to six months of KA-supplemented MD (MD + KA). Compared to MD, KA-supplementation in MD + KA determined (i) a decrease of Clostridiaceae, Methanobacteriaceae, Prevotellaceae, and Lactobacillaceae while Bacteroidaceae and Lachnospiraceae increased; (ii) a reduction of total and free IS and PCS compared to a free diet (FD)-more than the MD, but not as effectively as the VLPD. These results further clarify the driving role of urea levels in regulating gut integrity status and demonstrating that the reduction of azotemia produced by KA-supplemented VLPD was more effective than KA-supplemented MD in gut microbiota modulation mainly due to the effect of the drastic reduction of protein intake rather than the effect of KA.

Keywords: CKD; indoxyl sulfate; intestinal microbiome; ketoanalogs; mediterranean diet; p-cresyl sulfate; very low protein diet.

Scheme 1

Study Design MEDIKA2.

Figure 1

Fecal microbiota composition in chronic kidney disease (CKD) patients associated with different dietary regimens. Three different dietary regimens were evaluated: the Mediterranean diet (MD), Mediterranean diet supplemented with ketoanalogs (MD + KA), and the very-low-protein diet supplemented with ketoanalogs (VLPD). The panel on the left (A) shows the relative abundance (as percentual average) of gut bacterial phyla found in CKD patients after each dietary regimen. Phyla with a relative abundance <0.1% in all samples were grouped together and named “Others”. The right panel (B) shows the relative abundance (as percentual average) of gut bacterial families (>1% at least in one sample) found in the feces of CKD patients after each dietary regimen.

Figure 2

Fecal microbial genera found in chronic kidney disease (CKD) patients associated with different diets: Mediterranean diet (MD), ketoanalog-supplemented Mediterranean diet (MD + KA), and ketoanalog-supplemented very-low-protein diet (VLPD). Only statistical different (p < 0.05) genera at least in one dietary regimen were reported. Eryt. -Eubacterium: genus Eubacterium belongs to the Erythrobacteraceae family; Pep. -Clostridium: genus Clostridium belongs to the Peptostreptococcaceae family.

Figure 3

Multivariable associations between phylum abundances and dietary features. The MD-boxplot includes both Mediterranean diets with (MD + KA) and without (MD) ketoanalog supplementation. Both diets supplemented with ketoanalogs (Mediterranean diet (MD + KA) and the very-low-protein diet (VLPD)) are included in the “yes” KA boxplot.

Figure 4

Serum levels of IS and PCS measured by multiple-reaction-monitoring mass spectrometry analysis. Serum levels of IS and PCS in CKD patients in accordance with the different diets (Table 1). p values were calculated by the Wilcoxon test.

Figure 5

D-lactate serum levels measured in CKD patients in accordance with the different diets (Wilcoxon test).