Chronic kidney disease (CKD) in cats and dogs presents significant clinical challenges, with emerging research highlighting the pivotal role of the gut-kidney axis in its pathogenesis and management. ...Gut dysbiosis, characterized by alterations in the gut microbiome composition and function, contributes to microbial dysmetabolism of key nutrients causing uremic toxin accumulation and disruptions in amino acid, bile acid and fatty acid profiles. These disturbances in turn exacerbate renal dysfunction and systemic inflammation. Recent research in veterinary medicine, particularly in cats, supports the gut microbiome and microbial-derived metabolites as novel therapeutic targets. Potential therapeutic strategies targeting the gut microbiome and microbial dysmetabolism, including dietary management, probiotics, adsorbents, and addressing constipation, offer promising avenues for intervention to restore metabolic balance and preserve renal function. This review highlights the microbial influence on renal health and focuses on potential therapeutic strategies available to veterinarians to optimize the management of CKD in cats and dogs.
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The gut-kidney axis involves the interplay between the gut microbiome, intestinal barrier integrity, production of microbial metabolites, and renal physiologyDysbiosis exacerbates renal dysfunction through systemic inflammation and uremic toxin accumulationChronic kidney disease (CKD) in cats and dogs is associated with functional dysbiosis and derangements in the metabolism of key microbial metabolitesPotential therapeutic strategies targeting the gut microbiome offer promising avenues for intervention in CKD management for cats and dogs
The toxicological effects of p-cresol have primarily been attributed to its metabolism products; however, very little human data are available in the key organ (i.e., liver) responsible for the ...generation of these metabolites. Experiments were conducted in HepaRG cells utilizing the following markers of cellular toxicity: 2′-7′-dichlorofluorescein (DCF; oxidative stress) formation, total cellular glutathione (GSH) concentration, and lactate dehydrogenase (LDH; cellular necrosis) release. Concentrations of p-cresol, p-cresol sulfate, and p-cresol glucuronide were determined using validated assays. p-Cresol exposure resulted in concentration- and time-dependent changes in DCF (EC50 = 0.64 ± 0.37 mM at 24 h of exposure) formation, GSH (EC50 = 1.00 ± 0.07 mM) concentration, and LDH (EC50 = 0.85 ± 0.14 mM) release at toxicologically relevant conditions. p-Cresol was also relatively more toxic than 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid, indole-3-acetic acid, indoxyl sulfate, kynurenic acid, and hippuric acid on all markers. Although the exogenous administration of p-cresol sulfate and p-cresol glucuronide generated high intracellular concentrations of these metabolites, both metabolites were less toxic compared to p-cresol at equal-molar conditions. Moreover, p-cresol glucuronide was the predominant metabolite generated in situ from p-cresol exposure. Selective attenuation of glucuronidation (without affecting p-cresol sulfate formation, while increasing p-cresol accumulation) using independent chemical inhibitors (i.e., 0.75 mM l-borneol, 75 µM amentoflavone, or 100 µM diclofenac) consistently resulted in further increases in LDH release associated with p-cresol exposure (by 28.3 ± 5.3%, 30.0 ± 8.2% or 27.3 ± 6.8%, respectively, compared to p-cresol treatment). These novel data indicated that p-cresol was a relatively potent toxicant, and that glucuronidation was unlikely to be associated with the manifestation of its toxic effects in HepaRG cells.
The catalytic activity of 12-tungstophosphoric acid (TPA) supported on titania was investigated in butylation of
p-cresol with
tert-butanol. The catalyst with 20% TPA/TiO
2 calcined at 700
°C has ...shown higher activitiy than WO
3/ZrO
2, sulfated zirconia, H-beta catalyst in the above reaction.
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Butylation of
p-cresol with
tert-butanol was investigated on titania modified with 12-tungstophosphoric acid (TPA/TiO
2) catalyst under vapor phase conditions. Catalysts with different TPA loadings (10–25
wt.%) and calcination temperatures (650–750
°C) were prepared by suspending titanium hydroxide in methanol solution of TPA followed by drying and calcination. These catalysts were characterized by surface area, XRD,
31P MAS NMR, XPS, NH
3-TPD, and FTIR pyridine adsorption. XRD results indicated that the presence of TPA retarded the crystallization of titania and stabilized TiO
2 in anatase phase.
31P MAS NMR indicated the presence of TPA in various forms (dispersed, highly fragmented and Keggin intact). These catalysts showed both Brönsted and Lewis acidity, and 20% TPA on TiO
2 calcined at 700
°C (from here after words 20% TT-700) had the highest Brönsted as well as total acidity. Further, the catalytic activities were examined in
tert-butylation of
p-cresol with
tert-butanol. The catalytic activity depended on TPA coverage, and the highest activity corresponded to the monolayer of TPA on titania. The most active catalyst 20% TT-700 gave 82% conversion of
p-cresol and 89.5% selectivity towards 2-
tert-butyl cresol (TBC), 2,6-di-
tert-butyl cresol (DTBC) 7.5% and cresol-
tert-butyl ether (CTBE) 3% under optimized conditions. The activity was always higher than that of WO
3/ZrO
2, sulfated zirconia (SZ), USY, H-β zeolites and montmorillonite K-10 (K-10mont) under similar conditions.
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•Highly porous N-enriched carbons were firstly prepared from melamine/polyaniline.•Melamine/polyaniline-derived carbons (MPDCs) had remarkable performance in adsorptions.•MPDC700 had ...the highest adsorption capacity for p-nitrophenol and p-cresol from water.•Adsorptions were explained with π-π interaction and minor contribution of H-bonding.•The MPDC was recommended for phenols adsorption due to high capacity and reusability.
Recently, contamination of water resources with phenolic compounds (PCs) is severe. In this study, we firstly prepared nitrogen-enriched porous carbon via pyrolysis of a mixture of melamine and polyaniline. Melamine/polyaniline-derived carbons (MPDCs) were characterized and applied in the adsorption of PCs, like p-nitrophenol (pNP), hydroquinone (HQ) and p-cresol (pC), from water. A selected MPDC700, an MPDC prepared at 700 °C, had the highest adsorption capacity for pNP (Qmax: 910 ± 18 mg/g) and pC, compared with any known material. Based on the adsorption results under wide conditions and characteristics of MPDCs, the plausible adsorption mechanism, such as π-π interaction and hydrogen bonding, could be suggested. The best MPDC700 was recyclable for several runs; therefore, can be recommended as a competitive adsorbent to remove PCs from water.
12-Tungstophosphoric acid supported on nanosilica (TPA/SiO2) was employed as a catalyst for the tertiary butylation of p-cresol using tertiary butanol as an alkylating agent. The TPA/SiO2 catalyst ...was synthesized using the wet impregnation method followed by steaming at 150 °C for 6 h. The catalysts were characterized by means of X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) analysis. The surface acidity of the untreated and steamed catalysts was characterized via FTIR and DSC thermal analysis using pyridine as a probe molecule. The fresh and spent catalysts were characterized via TGA analysis. The catalytic activity studies showed that the steamed catalyst displayed higher activity, with a higher desired yield of 2-tert-butyl cresol (2-TBC) compared to the untreated catalyst, and that this activity was related to the presence of stronger Brønsted acid sites in the steamed catalyst. A detailed analysis of the TPA/SiO2 steamed catalyst was performed to study the effects of reactant time-on-stream, reactant feed rate, reaction temperature, and the molar ratio of tert-butanol to p-cresol. The optimum reaction temperature, tert-butanol/p-cresol molar ratio, feed rate, and time-on-stream were 413 K, a molar ratio of 2:1, 6 mL/min, and 2 h, respectively. The present study demonstrates that the TPA/SiO2 catalyst exhibits high activity in terms of % conversion and high % selectivity of 2-TBC under the optimized conditions. The characterization of fresh and spent catalysts confirmed the occurrence of coke deposition after the catalytic reaction. The catalyst was regenerated via heat treatment at 400 °C for 5 h. The regenerated catalyst was reused for subsequent runs for three cycles without showing a loss in its activity.
The catalytic performance of different molecular sieves in the alkylation of phenol with methanol to produce p‐cresol was evaluated, and the acidity and structure of the catalysts were characterized ...using
N2 adsorption–desorption and Fourier transform infrared spectroscopy techniques. It was shown that the catalytic activity of molecular sieves was closely related to their acidic site number, specific surface area, and pore structure. Since Zeolite ZSM‐5 (Zeolites Socony Mobil No. 5) has a relatively small amount of strong acid as well as a small pore size, it is favorable for the diffusion of p‐cresol out of the pores. Therefore, focusing on ZSM‐5, the effects of operating conditions such as weight hourly space velocity (WHSV), phenol/methanol (P/M) ratio, and reaction temperature on the catalytic performance were investigated. The results showed that increasing the WHSV, P/M ratio, and reaction temperature improved the selectivity to cresol. In addition, X‐ray diffraction and Thermal Gravity/Differential Thermal Gravity characterization methods were also carried out for ZSM‐5, and it was found that the deactivation of ZSM‐5 was due to coke deposition and pore blockage on the active site and that the selectivity to cresol could be restored by regenerating the catalyst and covering the strong acid site, which resulted in the reduction of the strong acid site to increase the selectivity of the product.
The structural properties of ZSM‐5 distinguish itself in the alkylation of phenol and methanol to p‐cresol. In this study, the effects of operating conditions such as the weight hourly space velocity (WHSV), P/M ratio, reaction temperature, as well as catalyst deactivation and regeneration on the catalytic performance were investigated using ZSM‐5.
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•Simultaneous degradation of phenolic compounds in AnMBR under saline conditions.•Increased concentration of the phenolics decreased their uptake rates in batch test.•Stronger ...methanogenic inhibitory effects with p-cresol than resorcinol.•Thermodynamic analysis explaining syntrophic associations in the AnMBRs.•Phylogenetic similarity of p-cresol- and resorcinol-degrading microbial communities.
Treating petrochemical wastewater is a challenge for conventional anaerobic reactors. One example is coal gasification wastewater that, besides its salinity, is rich in toxic and inhibitory aromatics, such as phenol, cresols, and resorcinol. Studies have shown that phenol and p-cresol share the same degradation intermediates, whereas resorcinol is degraded via another route. This study investigated the simultaneous degradation of p-cresol or resorcinol with phenol under anaerobic saline conditions. Batch experiments with anaerobic phenol-degrading biomass were conducted to assess the feasibility of the degradation of p-cresol and resorcinol. Volumetric uptake rates of 11.4 ± 2.4 mgp-cresol·L–1d–1 and 4.2 ± 1.9 mgresorcinol·L–1d–1 were determined. The effect of p-cresol and resorcinol on the specific methanogenic activity and the cell viability in phenol-degrading and non-adapted biomass was assessed. Half maximal inhibitory concentration (IC50) values of 0.73 gp-cresol·L-1 and 3.00 gresorcinol·L-1 were estimated for phenol-degrading biomass, whereas IC50 values of 0.60 gp-cresol·L-1 and 0.25 gresorcinol·L-1 were estimated for the non-adapted biomass. p-Cresol caused a higher decrease in the non-damaged cell counts in comparison to resorcinol. Two anaerobic membrane bioreactors under saline conditions 8 g Na+·L–1 were fed with mixtures of either phenol-p-cresol or phenol-resorcinol. At an influent phenol concentration of 2 g·L-1, maximum conversion rates of 22 mgp-cresol·gVSS-1d–1 and 16 mgresorcinol·gVSS–1d–1 were found. In both AnMBRs, Syntrophorhabdus sp. and Methanosaeta sp. were the most abundant bacteria and methanogen, respectively. The feasibility of simultaneous conversion of phenolic compounds under saline conditions in AnMBRs opens novel perspectives for the high-rate anaerobic treatment of chemical wastewater.
Scope
This study evaluates the effect of the prebiotic fiber xylooligosaccharide (XOS) on kidney function and gut microbiome in mice with adenine‐induced chronic kidney disease (CKD).
Method and ...results
Mice are fed the control diet containing adenine for 3 weeks to induce CKD and are switched to XOS supplemented (2 or 7%) or control diets for another 3 weeks. Mice with CKD exhibit increased blood urea nitrogen (BUN), creatinine, and kidney histopathology. XOS significantly reverses kidney injuries in CKD mice. Analysis of cecum microbiota reveales that adenine‐induced CKD does not change alpha diversity, and XOS induces a decrease of alpha diversity in control mice and mice with CKD. Beta diversity analysis shows significant clustering according to experimental groups. Six out of the nine bacterial genera enriched in CKD are significantly reduced with XOS intervention. Furthermore, XOS increases cecal short‐chain fatty acid (SCFA) production in both control and CKD mice. Cecal SCFAs and blood propionate are negatively correlated with BUN. XOS also decreases blood p‐cresol sulfate in CKD mice, likely resulting from altered microbial tyrosine metabolism.
Conclusion
These results show that XOS intervention improves kidney function in mice with CKD, and is associated with profound changes in microbial composition and metabolism.
Xylooligosaccharide (XOS) is considered a prebiotic fiber. This study provides evidence that dietary XOS supplementation is effective in enhancing recovery from adenine‐induced kidney damage by decreasing fibrosis and inflammation, as well as lowering circulating uremic toxin p‐cresol sulfate through regulating the gut microbiome.
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