Inflammation is a major mediator of CKD progression and is partly driven by altered gut microbiome and intestinal barrier disruption, events which are caused by: urea influx in the intestine resulting in dominance of urease-possessing bacteria; disruption of epithelial barrier by urea-derived ammonia leading to endotoxemia and bacterial translocation; and restriction of potassium-rich fruits and vegetables which are common sources of fermentable fiber. Restriction of these foods leads to depletion of bacteria that convert indigestible carbohydrates to short chain fatty acids which are important nutrients for colonocytes and regulatory T lymphocytes. We hypothesized that a high resistant starch diet attenuates CKD progression. Male Sprague Dawley rats were fed a chow containing 0.7% adenine for 2 weeks to induce CKD. Rats were then fed diets supplemented with amylopectin (low-fiber control) or high fermentable fiber (amylose maize resistant starch, HAM-RS2) for 3 weeks. CKD rats consuming low fiber diet exhibited reduced creatinine clearance, interstitial fibrosis, inflammation, tubular damage, activation of NFkB, upregulation of pro-inflammatory, pro-oxidant, and pro-fibrotic molecules; impaired Nrf2 activity, down-regulation of antioxidant enzymes, and disruption of colonic epithelial tight junction. The high resistant starch diet significantly attenuated these abnormalities. Thus high resistant starch diet retards CKD progression and attenuates oxidative stress and inflammation in rats. Future studies are needed to explore the impact of HAM-RS2 in CKD patients.

Patients and animals with chronic kidney disease (CKD) exhibit profound alterations in the gut environment including shifts in microbial composition, increased fecal pH, and increased blood levels of gut microbe-derived metabolites (xenometabolites). The fermentable dietary fiber high amylose maize-resistant starch type 2 (HAMRS2) has been shown to alter the gut milieu and in CKD rat models leads to markedly improved kidney function. The aim of the present study was to identify specific cecal bacteria and cecal, blood, and urinary metabolites that associate with changes in kidney function to identify potential mechanisms involved with CKD amelioration in response to dietary resistant starch. Male Sprague-Dawley rats with adenine-induced CKD were fed a semipurified low-fiber diet or a high-fiber diet [59% (wt/wt) HAMRS2] for 3 wk (n = 9 rats/group). The cecal microbiome was characterized, and cecal contents, serum, and urine metabolites were analyzed. HAMRS2-fed rats displayed decreased cecal pH, decreased microbial diversity, and an increased Bacteroidetes-to-Firmicutes ratio. Several uremic retention solutes were altered in the cecal contents, serum, and urine, many of which had strong correlations with specific gut bacteria abundances, i.e., serum and urine indoxyl sulfate were reduced by 36% and 66%, respectively, in HAMRS2-fed rats and urine p-cresol was reduced by 47% in HAMRS2-fed rats. Outcomes from this study were coincident with improvements in kidney function indexes and amelioration of CKD outcomes previously reported for these rats, suggesting an important role for microbial-derived factors and gut microbe metabolism in regulating host kidney function.

Background: Integrity of the tight junction (TJ) which seals the gap between the epithelial cells of the gastrointestinal tract is critical in preventing the entry of the microbial toxins, antigens, and other harmful products in the subepithelial tissues and the internal milieu. By enabling the absorption of these products, impairment of the intestinal epithelial barrier leads to local and systemic inflammation. We have recently found depletion of the key protein constituents of colonic epithelial TJ in animals with chronic kidney disease (CKD). Postmortem studies have revealed the presence of inflammation throughout the gastrointestinal tract in uremic humans. This observation suggests that uremia may cause disruption of the epithelial barrier in all segments of the gastrointestinal tract including the stomach, jejunum, and ileum. The present study was undertaken to explore this possibility. Methods: Sprague-Dawley rats were randomized to CKD or control groups. The CKD group was subjected to 5/6 nephrectomy while the control group underwent a sham operation. The animals were observed for 10 weeks at which time they were euthanized and their stomachs, jejunums, and ileums were removed and processed for measurement of TJ proteins. Results: The CKD rats showed marked azotemia, systemic oxidative stress, and marked depletion of the key protein constituents of the epithelial TJ (claudin-1, occludin, and ZO1) in the stomach, jejunum, and ileum. Conclusions: The present study extends the earlier finding of uremia-induced disruption of colonic epithelial TJ by documenting the involvement of the stomach, jejunum, and ileum as well.

Oxidative stress and inflammation play a central role in progression and complications of CKD and are, in part, due to impairment of the Nrf2 system which regulates expression of antioxidant and detoxifying molecules. Natural Nrf2 inducing phytochemicals have been shown to ameliorate kidney disease in experimental animals. However due to adverse outcomes clinical trial of synthetic Nrf2 activator, bardoxolone methyl (BARD), in CKD patients was terminated. BARD activates Nrf2 via 2 covalent modification of reactive cysteine residues in Nrf2 repressor molecule, Keap-1. In addition to Nrf2, Keap1 suppresses IKKB, the positive regulator of NF k B. Treatment with BARD analog, dh404, at 5-20 mg/kg/day in diabetic obese Zucker rats exacerbates whereas its use at 2 mg/kg/day in 5/6 nephrectomized rats attenuates CKD progression. We, therefore, hypothesized that deleterious effects of high dose BARD are mediated by activation of NF k B.CKD (5/6 nephrectomized) rats were randomized to receive dh404 (2 or 10mg/kg/day) or vehicle for 12 weeks. Vehicle-treated group exhibited glomerulosclerosis, interstitial fibrosis and inflammation, activation of NF k B, upregulation of oxidative, inflammatory and fibrotic pathways, and suppression of Nrf2 activity and its key target gene products. Treatment with low dose dh404 restored Nrf2 activity and expression of its target genes, attenuated activation of NF k B and fibrotic pathways, and reduced glomerulosclerosis, interstitial fibrosis and inflammation. In contrast treatment with high dh404 dosage intensified proteinuria, renal dysfunction and histological abnormalities, amplified up-regulations of NF k B and fibrotic pathways, and suppression of Nrf2 system. Thus therapy with BARD analogs exerts a dose-dependent dimorphic impact on CKD progression.

Background: Chronic kidney disease (CKD) causes klotho deficiency, oxidative stress and inflammation which are common features and major mediators of progression of renal disease. Oxidative stress in CKD is, partly, due to impaired activation of Nrf2, the master regulator of genes encoding antioxidant and cytoprotective molecules. Oxidative stress inhibits klotho expression in the kidney. Given the role of Nrf2 dysfunction in the pathogenesis of oxidative stress in CKD, we hypothesized that treatment with Nrf2 activator, dh404, may restore renal klotho expression and attenuate oxidative stress and inflammation in CKD. Methods: Male SD rats were subjected to 5/6 nephrectomy (CKD) or sham operation. The CKD rats were randomized to receive dh404 (2mg/kg/day) or vehicle for 12 weeks. At the conclusion of the observation period tail arterial pressure was measured and 24-hr urine was collected. Animals