Mikio Sugano

Oral charcoal adsorbent (AST-120) prevents progression of cardiac damage in chronic kidney disease through suppression of oxidative stress

BACKGROUND Chronic kidney disease (CKD) is an important risk factor for cardiovascular disease (CVD). Increased oxidative stress plays a role in the pathogenesis of CVD in CKD patients. The oral charcoal adsorbent AST-120 attenuates the progression of CKD possibly by removing uraemic toxins such as indoxyl sulfate (IS), and reduces oxidative stress. We investigated the relationship between oxidative stress and cardiac damage in CKD and its prevention by AST-120. METHODS Male Lewis rats were administered adriamycin at 8 weeks of age, and the right kidney was removed at 12 weeks of age. From 14 weeks of age, the rats were treated daily with AST-120 (n = 8) or were untreated (control group, n = 8). At 34 weeks of age, the rats were killed and urinary and blood biochemical tests as well as cardiac histological analyses were performed. RESULTS At 14 weeks of age, there were no significant differences in blood pressure, renal function (creatinine clearance: 1.54 +/- 0.28 mL/min versus 1.60 +/- 0.22 mL/min), oxidative stress markers or other biochemical data between the control and AST-120 groups. At 34 weeks, despite similar blood pressure and renal function (creatinine clearance: 0.78 +/- 0.46 mL/min versus 0.75 +/- 0.54 mL/min), serum concentrations of IS and urinary excretion of 8-hydroxydeoxyguanosine (8-OHdG), acrolein and IS were significantly lower in the AST-120 group than in the control group. Heart volume, left ventricular volume and cardiac fibrosis were significantly smaller in the experimental AST-120 group than in the control group. Immunohistological analysis revealed that the numbers of 8-OHdG- and acrolein-positive cardiomyocytes and the degrees of myocardial and perivascular fibrosis were ameliorated by AST-120 administration. The myocardial fibrosis score was significantly associated with the 8-OHdG- (r = 0.848, P < 0.001) and acrolein-positive (r = 0.812, P < 0.001) cell scores. The perivascular fibrosis score was also significantly associated with the 8-OHdG- (r = 0.906, P < 0.0001) and acrolein-positive (r = 0.789, P < 0.001) cell scores. CONCLUSIONS Oxidative stress is suggested to play a key role in the development of cardiac hypertrophy and fibrosis in CKD. AST-120 may suppress oxidative stress and reduce cardiac damage in CKD.

Effect of Oral Adsorbent (AST-120) on Renal Function, Acquired Renal Cysts and Aortic Calcification in Rats with Adriamycin Nephropathy

Aims: The effect of oral adsorbent, AST-120, on the experimental renal disease induced by adriamycin, uninephrectomy and high protein diet proposed as a model of acquired cystic disease of the kidney was investigated. Methods: 3 mg of adriamycin was injected into the tail vein of rats and 4 weeks later right-side nephrectomy was performed, 2 weeks thereafter 26 rats with urinary protein excretion between 100 and 358 mg/day were selected from 60 rats. Two groups, 13 rats in each group, namely the AST-120-treated group and control group, both of which had equal renal damage before the administration of AST-120 or placebo. AST-120 (0.4 g/100 g BW/day) was administered for 19 weeks. Results: Serum creatinine and BUN in the AST-120-treated group were significantly lower (serum creatinine: 3.3 ± 2.1 vs. 7.1 ± 2.7 mg/dl, p < 0.003) and creatinine clearance was higher (0.62 ± 0.49 vs. 0.29 ± 0.30 ml/min, p < 0.05) at the final examination than in the control group. Survival rate which was examined using another set of 9 rats was higher in AST-120-treated rats than in AST-120-untreated rats. Serum indoxyl sulfate was significantly lower at all times after using AST-120 in the AST-120-treated group than in contrast to the control group. Histological examination revealed less severe interstitial and cystic changes in the AST-120-treated group. This suggests that AST-120 can prevent or retard the development of acquired renal cystic disease in this model. Aortic calcification tended to be less severe in the AST-120-treated group because of less serum Ca × P products. Conclusion: The AST-120-treated group significantly decreased serum creatinine and increased creatinine clearance with less severe renal cystic changes in this model during the later weeks of administration of AST-120 or at death, accompanied with the tendency of less severe aortic calcification.

Anti-oxidative effect of AST-120 on kidney injury after myocardial infarction.

Chronic kidney disease (CKD) is a crucial risk factor for cardiovascular disease (CVD), and combined CKD and CVD further increases morbidity and mortality. Here, we investigated effects of AST‐120 on oxidative stress and kidney injury using a model of myocardial infarction (MI) in rats.

Proteomic analysis of rat plasma by SELDI-TOF-MS under the condition of prevention of progressive adriamycin nephropathy using oral adsorbent AST-120

Aims: To determine changes in relative peak intensities of mass-to-charge ratio (m/z) between 2,000 and 15,000, which are difficult to evaluate by 2-dimensional gel electrophoresis, SELDI-TOF-MS (surface-enhanced laser desorption/ionization time of flight-mass spectrometry) proteomic changes in rat models of adriamycin nephropathy with or without AST-120 were investigated. Methods: A normal group (n = 5), an adriamycin nephropathy group (n = 9), and an adriamycin nephropathy + AST-120 group (4 g/head/day) (n = 9) were established in SD rats. Anion exchange chips, Q10, washed by 50 mM Tris-HCl pH 8 as a ProteinChip and sinapinic acid were used. The mass range between 2,000 and 15,000 Da was measured. Twenty to 34 weeks after adriamycin 3 mg/kg injection, the adriamycin nephropathy + AST-120 group (plasma creatinine value: 2.1 ± 0.8 mg/dl) clearly demonstrated slight renal dysfunction compared with that in the adriamycin nephropathy group (5.4 ± 2.0 mg/dl). Results: The relative intensities in the adriamycin nephropathy group were significantly higher in 7 peaks (such as 8,640, and 8,822 Da) and lower in 8 peaks (such as 4,188, and 8,358 Da) than those in the normal group. The relationship between the relative intensity of peaks and the plasma creatinine value demonstrated a positive correlation in 11 peaks (such as 8,640, and 8,822 Da), and a negative correlation in 6 peaks (such as 4,188 and 8,358 Da). Although the relative intensities of peaks in the adriamycin nephropathy + AST-120 group were between that of the adriamycin nephropathy group and that of the normal group, the relative intensities of 4 peaks (such as 3,664 and 5,179 Da) in the adriamycin nephropathy + AST-120 group demonstrated higher values than in the two other groups. The m/z 3,664 peak was purified and identified as a C-terminal fragment of apolipoprotein C-III. Conclusion: Low-molecular proteins and peptides in plasma in this chronic renal failure model showed not only increases but also decreases in some peaks. The relative intensities in some peaks increased in the adriamycin nephropathy + AST-120 group more than in the two other groups. One of these peaks was identified as the apolipoprotein C-III fragment. The relationship between these changes and the prevention of progression of chronic renal failure by AST-120 remains to be established.

Dietary Inorganic Phosphorus Regulates the Intestinal Peptide Transporter PepT1

BACKGROUND Both organic and inorganic phosphorus (Pi) are present in regularly consumed foods, such as meats, eggs, and dairy products. Pi is often included in foods as an additive (as hidden phosphorus). The intestinal peptide transporter PepT1 mediates protein absorption, which is disturbed in renal insufficiency. Our aim was to determine the effects of dietary Pi content on the peptide transport activity and expression of PepT1. METHODS The following animal models were used: (1) 7-week-old male Wistar rats; and (2) rats that underwent 3/4 nephrectomy to induce chronic kidney disease (CKD). The rats were fed a normal-protein (20%) diet containing low (0.02%), normal (0.6%), or high (1.2%) Pi levels. They were also fed diets containing varying amounts of protein and either low or normal Pi levels as follows: (1) low Pi/normal protein, (2) low Pi/high (50%) protein, (3) normal Pi/normal protein, and (4) normal Pi/high protein. RESULTS Intestinal peptide transport activity and PepT1 expression levels were significantly higher in the CKD rats than in sham-operated control ones. Compared with the normal-protein diet, the high-protein diet increased PepT1 expression in the CKD rats. Intestinal dipeptide transport activity and PepT1 protein levels did not increase in the rats fed the low-Pi/high-protein diet. In contrast, intestinal dipeptide transport activity and PepT1 protein expression were markedly increased in the rats fed the normal-Pi/high-protein diet. CONCLUSION Dietary Pi levels regulate intestinal peptide transport activity through PepT1.

Renal vascular structural properties and their alterations by removal of uraemic toxins in a rat model of chronic kidney disease

Renal vascular structural properties and their alterations by removal of uraemic toxins with AST‐120, an oral adsorbent, were examined in subtotal nephrectomized rats. Eight‐ or 9‐week‐old Sprague‐Dawley rats received 3/4 nephrectomy (n = 18) and thereafter were fed 24.5% protein diet with (AST; n = 9) or without (AST–; n = 9) AST‐120 (0.4 g/100 g bodyweight). Sham‐operated rats (Sham; n = 9) received the diet without AST‐120. At 21–22 weeks of age, flow–pressure (F‐P) and pressure–glomerular filtration rate (P‐GFR) relationships were determined for maximally vasodilated, perfused kidneys. The gradient of F‐P (minimal renal vascular resistance reflecting the overall luminal dimensions of pre‐ and post‐glomerular vasculature) was lower in AST– than Sham rats. In contrast, the x‐intercept (preglomerular : post‐glomerular vascular resistance ratio) and gradient (glomerular filtration capacity) of P‐GFR did not differ between the two groups. The vascular wall and lumen at the interlobular arteries were greater in AST– than Sham rats. Although the vascular wall and lumen at the interlobular arteries were less in AST than in AST– rats, the gradient of F‐P and the x‐intercept of P‐GFR did not differ between the two groups. In contrast, the glomerular filtration capacity was greater in AST than AST– rats. In conclusion, the lumen of both pre‐ and post‐glomerular resistance vessels increased and glomerular filtration capacity failed to increase in subtotal nephrectomized rats. Uraemic toxins could play an important role in the development of structural alterations in glomeruli rather than renal resistance vessels in chronic kidney disease.