Canagliflozin protects the cardiovascular system through effects on the gut environment in non-diabetic nephrectomized rats.

BACKGROUND: The gut produces toxins that contribute to the cardiovascular complications of chronic kidney disease. Canagliflozin, a sodium glucose cotransporter (SGLT) 2 inhibitor that is used as an anti-diabetic drug, has a weak inhibitory effect against SGLT1 and may affect the gut glucose concentration and environment. METHODS: Here, we determined the effect of canagliflozin on the gut microbiota and the serum gut-derived uremic toxin concentrations in 5/6th nephrectomized (Nx) rats. RESULTS: Canagliflozin increased the colonic glucose concentration and restored the number of Lactobacillus bacteria, which was low in Nx rats. In addition, the expression of tight junction proteins in the ascending colon was low in Nx rats, and this was partially restored by canagliflozin. Furthermore, the serum concentrations of gut-derived uremic toxins were significantly increased by Nx and reduced by canagliflozin. Finally, the wall of the thoracic aorta was thicker and there was more cardiac interstitial fibrosis in Nx rats, and these defects were ameliorated by canagliflozin. CONCLUSIONS: The increases in colonic glucose concentration, Lactobacillus numbers and tight junction protein expression, and the decreases in serum uremic toxin concentrations and cardiac interstitial fibrosis may have been caused by the inhibition of SGLT1 by canagliflozin because similar effects were not identified in tofogliflozin-treated rats.

Contribution of uremic dysbiosis to insulin resistance and sarcopenia.

BACKGROUND: Chronic kidney disease (CKD) leads to insulin resistance (IR) and sarcopenia, which are associated with a high mortality risk in CKD patients; however, their pathophysiologies remain unclear. Recently, alterations in gut microbiota have been reported to be associated with CKD. We aimed to determine whether uremic dysbiosis contributes to CKD-associated IR and sarcopenia. METHODS: CKD was induced in specific pathogen-free mice via an adenine-containing diet; control animals were fed a normal diet. Fecal microbiota transplantation (FMT) was performed by oral gavage in healthy germ-free mice using cecal bacterial samples obtained from either control mice (control-FMT) or CKD mice (CKD-FMT). Vehicle mice were gavaged with sterile phosphate-buffered saline. Two weeks after inoculation, mice phenotypes, including IR and sarcopenia, were evaluated. RESULTS: IR and sarcopenia were evident in CKD mice compared with control mice. These features were reproduced in CKD-FMT mice compared with control-FMT and vehicle mice with attenuated insulin-induced signal transduction and mitochondrial dysfunction in skeletal muscles. Intestinal tight junction protein expression and adipocyte sizes were lower in CKD-FMT mice than in control-FMT mice. Furthermore, CKD-FMT mice showed systemic microinflammation, increased concentrations of serum uremic solutes, fecal bacterial fermentation products and elevated lipid content in skeletal muscle. The differences in gut microbiota between CKD and control mice were mostly consistent between CKD-FMT and control-FMT mice. CONCLUSIONS: Uremic dysbiosis induces IR and sarcopenia, leaky gut and lipodystrophy.

ß-hydroxybutyrate attenuates renal ischemia-reperfusion injury through its anti-pyroptotic effects.

Ketone bodies including ß-hydroxybutyrate (ß-OHB) have been shown to protect against ischemic tissue injury when present at low concentrations. We evaluated the impact of ß-OHB on renal ischemia/reperfusion injury (IRI). Mice were treated with a continuous infusion of ß-OHB using an osmotic mini-pump before and after IRI. We also tested the effects of increasing endogenous serum ß-OHB levels by fasting. Renal IRI was attenuated by ß-OHB treatment compared to saline control, with similar results in the fasting condition. ß-OHB treatment reduced the number of terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL)-positive cells and increased expression of forkhead transcription factor O3 (FOXO3), an upstream regulator of pyroptosis. Although ß-OHB treatment did not impact markers of apoptosis, it decreased the expression of caspase-1 and proinflammatory cytokines, indicating that ß-OHB blocked pyroptosis. In a human proximal tubular cell line exposed to hypoxia and reoxygenation, ß-OHB reduced cell death in a FOXO3-dependent fashion. Histone acetylation was decreased in kidneys exposed to IRI and in proximal tubular cells exposed to hypoxia and reoxygenation, and this effect was ameliorated by ß-OHB through the inactivation of histone deacetylases. In vitro, ß-OHB treatment restored histone acetylation at the FOXO3 promoter. Consistent with epigenetic molecular effects, the renoprotective effects of ß-OHB were still observed when the continuous infusion was stopped at the time of IRI. Thus, ß-OHB attenuates renal IRI through anti-pyroptotic effects, likely mediated by an epigenetic effect on FOXO3 expression.

Oral adsorbent AST-120 ameliorates gut environment and protects against the progression of renal impairment in CKD rats.

BACKGROUND: Oral charcoal adsorbent AST-120 (AST) is reported to ameliorate renal dysfunction by the absorption of toxic substance in the gut. Recent study revealed that, in CKD, gut environment is disturbed including the decrease in tight junctions and Lactobacillus (Lact). In this study, we examined whether AST improves the renal dysfunction through gut environment. METHOD: Six-week-old spontaneously hypertensive rats (SHR) were rendered CKD by 5/6th nephrectomy (Nx). SHRs were divided into SHR (Sham), SHR with Nx (Nx), and Nx given AST (Nx + AST) (n = 10, each). After 12 weeks, rats were killed and biochemical parameters were explored. The gut flora was analyzed. Furthermore, gut molecular changes in tight junctions and toll-like receptors were examined. We also investigated the effects of the combination therapy with AST and Lact. RESULTS: The increase in serum urea nitrogen and urinary protein excretion in Nx was restored in Nx + AST. The increased renal glomerulosclerosis in Nx was ameliorated in Nx + AST. Increases in serum uremic toxins and IL-6 in Nx were ameliorated in Nx + AST. The gut flora analysis revealed that the decrease in Lact in Nx was restored in Nx + AST. The downregulation in the tight junction and TLR2 in Nx was mitigated by AST. However, combination therapy failed to exhibit additional effects. CONCLUSION: AST ameliorated renal function with the restoration of Lact and tight junction through TLR pathway, which would mitigate systemic inflammation and contributed to their renoprotective effects. Our study provides a novel mechanism of the renoprotective effects by AST.

Safety of warfarin therapy in chronic hemodialysis patients: a prospective cohort study.

BACKGROUND: We conducted a multicenter prospective cohort study to assess the safety of warfarin therapy in Japanese hemodialysis (HD) patients. METHODS: Chronic HD patients on warfarin therapy (warfarin users) were recruited from 111 HD centers in Japan. Two dialysis-vintage-matched warfarin non-users (non-users) were selected from the same HD center as each warfarin user. Clinical data were collected upon registration and every 12 months thereafter for up to 36 months. RESULTS: The final cohort consisted of 365 warfarin users and 692 non-users and was followed for an average of 27.7 months. The mean age of warfarin users (68.8 ± 10.6 years) was significantly higher than that of non-users (66.9 ± 11.0 years, p < 0.001). The analyses by multivariate Cox proportional-hazard models showed that the age [hazard ratio (HR) = 1.07 for each 1-year increase, 95 % confidence interval (CI) 1.05-1.08, p < 0.001] was significantly associated with the death from any cause, but warfarin use (1.08, CI 0.75-1.57, p = 0.68) was not when being adjusted for sex, diabetes mellitus, antiplatelet use, and atrial fibrillation. The risk of composite events, which included death from any cause, stroke, cardiovascular disease, and peripheral arterial disease, was also associated with age but was not associated with warfarin use. CONCLUSION: The results of this study suggested that warfarin use by HD patients might not be harmful in chronic state, while the safety for the initiation of warfarin therapy in HD patients remained to be determined.

Posterior reversible encephalopathy syndrome in a uremic patient with autosomal recessive polycystic kidney disease.

Posterior reversible encephalopathy syndrome (PRES) is characterized by headache, seizures, altered mental status, and visual disturbance. It is diagnosed by the presence of both clinical symptoms and radiographic findings on the parietal-occipital lobes. We here report a 61-year-old woman with non-compensative liver cirrhosis and chronic kidney disease, presenting with uremia-induced PRES. She expressed loss of consciousness and subsequent visual disturbance, during the progression of uremia. She was treated with hemodiafiltration therapy, and the symptoms of PRES fully improved. The case is of particular interest, in that the appearance of abnormal findings on magnetic resonance imaging was delayed more than 2 weeks, as compared to that of clinical symptoms. The etiology of chronic kidney disease in the patient was considered to be autosomal recessive polycystic kidney disease, and we performed DNA sequencing analysis on the polycystic kidney and hepatic disease 1 gene. Two homozygous missense mutations were found in the patient and may combinatorially affect the disease. This case raises a possibility that the incidence of PRES is much higher if the radiological examination is performed more frequently.