Chronic Kidney Disease, Gut Dysbiosis, and Constipation: A Burdensome Triplet.

Gut dysbiosis has been implicated in the progression of chronic kidney disease (CKD). Alterations in the gut environment induced by uremic toxins, the dietary restriction of fiber-rich foods, and multiple drugs may be involved in CKD-related gut dysbiosis. CKD-related gut dysbiosis is considered to be characterized by the expansion of bacterial species producing precursors of harmful uremic toxins, such as indoxyl sulfate and p-cresyl sulfate, and the contraction of species generating beneficial short-chain fatty acids, such as butyrate. Gut-derived uremic toxins cause oxidative stress and pro-inflammatory responses, whereas butyrate exerts anti-inflammatory effects and contributes to gut epithelial integrity. Gut dysbiosis is associated with the disruption of the gut epithelial barrier, which leads to the translocation of endotoxins. Research on CKD-related gut dysbiosis has mainly focused on chronic inflammation and consequent cardiovascular and renal damage. The pathogenic relationship between CKD-related gut dysbiosis and constipation has not yet been investigated in detail. Constipation is highly prevalent in CKD and affects the quality of life of these patients. Under the pathophysiological state of gut dysbiosis, altered bacterial fermentation products may play a prominent role in intestinal dysmotility. In this review, we outline the factors contributing to constipation, such as the gut microbiota and bacterial fermentation; introduce recent findings on the pathogenic link between CKD-related gut dysbiosis and constipation; and discuss potential interventions. This pathogenic link needs to be elucidated in more detail and may contribute to the development of novel treatment options not only for constipation, but also cardiovascular disease in CKD.

Impact of sevelamer hydrochloride on serum magnesium concentrations in hemodialysis patients.

Serum Mg levels are elevated in patients with renal insufficiency: harmful effects of hypomagnesemia have been reported in patients receiving hemodialysis (HD). In this cross-sectional study, which included 86 HD patients (male : female = 56:30, age 68 ± 12 years), we examined the clinical factors associated with serum Mg levels, with a focus on sevelamer, a phosphate binder widely used to control the hyperphosphatemia of HD patients. The mean serum Mg concentration among our patients was 2.48 ± 0.37 mg/dL (1.02 ± 0.15 mmol/L). Sevelamer was administered to 67 patients (77.9%) at a mean dose of 1.98 ± 1.64 g/day. Sex, diabetes mellitus, cardiovascular disease, anuria, and drugs other than sevelamer were not associated with serum Mg levels. HD duration, serum calcium, albumin, high-density lipoprotein cholesterol, normalized protein catabolic rate (nPCR), creatinine generation rate, and sevelamer dose correlated positively with serum Mg levels, whereas a negative correlation was observed for age and high-sensitivity C-reactive protein. A stepwise multiple regression analysis revealed that age, nPCR, and the dose of sevelamer were independently associated with serum Mg levels. Sevelamer and Mg have been reported to exhibit similar effects, such as an anti-inflammatory effect, inhibition of cardiovascular calcification, and decreased mortality. Therefore, the pleiotropic effects of sevelamer may be partly attributable to the increase in serum Mg levels caused by the drug itself.

Efficacy and safety of eldecalcitol, a new active vitamin D3 analog, in the bone metabolism of postmenopausal women receiving maintenance hemodialysis.

Eldecalcitol (ELD), a new active vitamin D3 analog developed in Japan, has attracted attention as an effective osteoporotic therapeutic drug. However, because ELD leads to greater calcium absorption than does conventional active vitamin D3, it has yet to be used in patients with renal insufficiency. Therefore, we evaluated the efficacy and safety of ELD treatment in 27 postmenopausal women receiving maintenance dialysis in our institution and underwent ELD treatment (starting at 0.5 µg/day) for 6 months. The mean serum albumin-corrected calcium (Caalb) level was significantly increased following treatment (9.01 ± 0.60 before versus 9.56 ± 0.55 after treatment, mean ± SD). Severe hypercalcemia was prevented through cessation or adjustment of the dosage of calcium-containing phosphate binders or existing active vitamin D. The mean serum phosphorus and intact parathyroid hormone levels were well-controlled throughout. The median levels of bone turnover markers, bone-specific alkaline phosphatase and tartrate-resistant acid phosphatase-5b were significantly decreased. The mean lumbar spine bone mineral density (BMD) was increased, a significant difference being observed in age-matched Z-scores (-0.60 ± 1.6 versus -0.36 ± 1.5, p = 0.018). The average change in lumbar spine BMD after ELD treatment was 3.10%, and in patients with a T-score of <-4.0, it was 5.63%. There was no effect on forearm BMD. Although this study is based on short-term observation in a single institution, our results suggest that ELD could be used to increase bone density in dialysis patients.

Emerging effects of sevelamer in chronic kidney disease.

Sevelamer, a non-absorbable anion exchange resin, is used to control hyperphosphatemia in chronic kidney disease (CKD) by binding to dietary phosphate in the gastrointestinal tract. Lipid-lowering effect is a widely recognized pleiotropic effect of sevelamer. In addition, many studies have reported that sevelamer leads to reduced vascular calcification compared with calcium-containing phosphate binders, which is attributed to the improved lipid profiles and decreased calcium load. In addition, recent studies have suggested novel pleiotropic effects on bone structure, inflammation, oxidative stress, anemia, fetuin-A, and trace element metabolism in CKD patients. All of these effects have the potential to suppress the development/progression of cardiovascular lesions and reduce mortality. This review summarizes novel findings from recent studies and discusses the potential pleiotropic effects of sevelamer on non-traditional cardiovascular risk factors in CKD patients.

Clinical factors associated with serum copper levels and potential effect of sevelamer in hemodialysis patients.

OBJECTIVE: Copper is an essential mineral nutrient for humans. Serum copper levels of hemodialysis patients are higher than those of healthy subjects, but it remains to be elucidated whether increased serum copper may have harmful effects. In addition, a recent in vitro study has shown that sevelamer can adsorb copper. In the present study, we searched for clinical factors associated with serum copper levels in hemodialysis patients. METHODS: This cross-sectional study included patients undergoing hemodialysis for more than 6 months. In these patients, we statistically tested associations between serum copper levels and other parameters, including nutritional markers, lipid profiles, oxidative stress, inflammation, and sevelamer administration. RESULTS: Among 48 patients (male/female = 28:20, age 71 ± 10 years, hemodialysis duration 84 ± 72 months), sevelamer hydrochloride was administered in 39 patients (81.3 %). In univariate analysis, serum copper levels showed significant positive correlations with serum levels of total cholesterol, low-density lipoprotein (LDL) cholesterol, high-sensitivity C-reactive protein (hs-CRP), and malondialdehyde modified-LDL and negative correlations with plasma total homocysteine levels and the administered dose of sevelamer. In multivariate analysis, serum levels of LDL-cholesterol and hs-CRP were found to be independent determinants of serum copper levels. CONCLUSION: We found that serum copper levels were independently associated with dyslipidemia and inflammation in hemodialysis patients, but the pathogenic roles of copper remain to be elucidated. In addition, potential effect of sevelamer on serum copper levels should be examined in appropriately designed studies.

Potential influence of sevelamer hydrochloride on responsiveness to erythropoiesis-stimulating agents in haemodialysis patients.

AIM: Vitamin D analogues, cinacalcet, and sevelamer play pivotal roles in the management of chronic kidney disease-mineral bone disorder, and are noted to have pleiotropic effects. We examined whether these agents might be associated with the responsiveness to erythropoiesis-stimulating agents (ESA). METHODS: In this cross-sectional study including haemodialysis patients treated with ESA, we searched for clinical parameters associated with the ESA resistance index, which was calculated as the weekly ESA dose divided by the patient's haemoglobin value. RESULTS: Among 45 patients (male: female = 28 : 17, age 68 ± 10 years, haemodialysis duration 84 ± 60 months), vitamin D analogue, cinacalcet, and sevelamer were used in 95.6%, 26.7%, and 84.4% of the patients, respectively. Univariate analysis showed significant association of the ESA resistance index with transferrin saturation rate (TSAT), vitamin D analogue dose, and sevelamer dose. In multivariate analysis, the sevelamer dose and TSAT were found to be independent determinants of the ESA resistance index. CONCLUSION: Our preliminary data showed an independent association between sevelamer dose and the responsiveness to ESA in haemodialysis patients. Further studies are required to investigate the causal relationship between sevelamer and ESA responsiveness.

A novel mechanism in maggot debridement therapy: protease in excretion/secretion promotes hepatocyte growth factor production.

Maggot debridement therapy (MDT) is effective for treating intractable wounds, but its precise molecular mechanism, including the association between MDT and growth factors, remains unknown. We administered MDT to nine patients (66.3 ± 11.8 yr, 5 male and 4 female) with intractable wounds of lower extremities because they did not respond to conventional therapies. Significant increases of hepatocyte growth factor (HGF) levels were observed in femoral vein blood during 48 h of MDT (P < 0.05), but no significant change was found for vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), transforming growth factor-ß1 (TGF-ß1), or tumor necrosis factor-α (TNF-α). We conducted NIH-3T3 cell stimulation assay to evaluate the relation between HGF and protease activity in excretion/secretion (ES) derived from maggots. Compared with the control group, HGF was significantly higher in the 0.05 µg/ml ES group (P < 0.01). Furthermore, protease inhibitors suppressed the increase of HGF (P < 0.05). The HGF expression was increased in proportion to the ES protein concentration of 0.025 to 0.5 µg/ml. In fact, ES showed stronger capability of promoting HGF production and less cytotoxicity than chymotrypsin or bromelain. HGF is an important factor involved in cutaneous wound healing. Therefore, these results suggest that formation of healthy granulation tissue observed during MDT results from the increased HGF. Further investigation to identify molecules enhancing HGF expression by MDT will contribute greatly to drug target discovery for intractable wound healing therapy.

Impact of lower limbs' arterial calcification on the prevalence and severity of PAD in patients on hemodialysis.

BACKGROUND: Peripheral arterial disease (PAD) is one of the serious complications in patients on hemodialysis (HD) therapy. However, arterial calcification of lower limbs' arteries and its impact on the prevalence and severity of PAD has never been quantitatively evaluated in HD patients with PAD. METHODS: Ninety-seven HD patients were enrolled to evaluate calcification score in superficial femoral artery (SFACS) and below-knee arteries (BKACS) quantitatively by 64-row multidetector computed tomography as well as ankle-brachial pressure index (ABI), toe-brachial pressure index (TBI), and clinical and laboratory parameters. RESULTS: Forty-six patients (47.2%) had PAD, and 11 patients had critical limb ischemia (CLI). SFACS and BKACS were significantly associated with the prevalence and severity of PAD, and receiver-operating characteristic analysis showed that SFACS and BKACS well predicted the prevalence of PAD and CLI in HD patients. The independent associating factors for PAD were BKACS and low TBI (r(2) = 0.534; P < .0001). Low TBI was also an independent associating factor for CLI (r(2) = 0.245; P < .0001). Multivariate analysis indicated that the independent associating factors for TBI in HD patients were BKACS and C-reactive protein (CRP; r(2) = 0.358; P = .006). CONCLUSIONS: Present quantitative analysis clearly provided the first evidence that arterial calcification of lower limbs' arteries was closely associated with the prevalence and severity of PAD in HD patients. Furthermore, arterial calcification of below-knee arteries and micro-inflammation represented as CRP were the independent associating factors for low TBI, which was the independent associating factor for PAD and CLI in HD patients.

Serum biological antioxidant potential predicts the prognosis of hemodialysis patients.

BACKGROUND: It is well known that oxidative stress is enhanced in patients with end-stage renal disease. However, little is known about the relationship between serum antioxidant capacity and clinical outcome in hemodialysis (HD) patients. METHODS: We examined the relationship between serum biomarkers of oxidative stress and clinical outcomes including all-cause mortality, hospitalization rate and incidence of cardiovascular events in HD patients. As biomarkers of oxidative stress, we measured serum levels of coenzyme Q10 (CoQ10) and biological antioxidant potential (BAP). RESULTS: 108 patients were observed for 30 months as the follow-up periods. The survival group (n = 83) showed significantly higher BAP values compared with those in death groups (n = 25; p < 0.05). When serum BAP levels were divided into two groups by their median value, the group with higher BAP values had a better survival rate than that with lower BAP values on the Kaplan-Meier survival analysis (p = 0.05). Although serum levels of CoQ10 did not show any association with clinical outcomes, lower BAP was selected as an independent risk factor for all-cause mortality as well as the absence of angiotensin-converting enzyme inhibitors/angiotensin II receptor blockers therapy by age-adjusted Cox regression analysis. CONCLUSIONS: This study indicated that BAP could predict the prognosis of HD patients.

Beraprost sodium, an orally active prostaglandin I(2) analog, improves renal anemia in hemodialysis patients with peripheral arterial disease.

Beraprost sodium (BPS) is a stable, orally active prostaglandin I(2) (PGI(2) ) analog with antiplatelet and vasodilating properties. It has been reported that PGI(2) has pleiotropic effects that are anti-inflammatory and anti-atherogenic. In this study, we aim to determine the relationship between PGI(2) and renal anemia. We conducted a prospective randomized trial including 20 hemodialysis patients. Ten patients were assigned to be treated with 120 µg/day of BPS and the other patients were assigned to a control group. After six months, the titer of hemoglobin had significantly increased in the BPS group compared to the baseline (11.1 ± 0.3 g/dL vs. 10.3 ± 1.4 g/dL, respectively), and there was a significant difference between the BPS group and the control group. The level of ferritin was lower in the BPS group compared to the control group, but the average dose of erythropoietin did not significantly change. These findings suggest that BPS may improve renal anemia in hemodialysis patients.

[Efficacy and safety of concomitant use of rabeprazole during dual-antiplatelet therapy with clopidogrel and aspirin after drug-eluting stent implantation: a retrospective cohort study].

After coronary stent implantation, dual-antiplatelet therapy (DAT), such as aspirin and clopidogrel, is essential to prevent stent thrombosis. Proton-pump inhibitors (PPIs) may be used to prevent gastrointestinal (GI) bleeding during DAT, but there is no evidence for the efficacy of PPIs in this setting. Because both clopidogrel and PPIs are metabolized by cytochrome P450 (CYP) 2C19, there is a possibility that, through drug interaction, PPIs diminish the antiplatelet effect of clopidogrel. In this retrospective cohort study, we evaluated the efficacy and safety of rabeprazole in patients receiving DAT of clopidogrel and aspirin after drug-eluting stent implantation. In 199 patients treated with DAT alone (control group) and 103 patients treated with rabeprazole plus DAT (rabeprazole group), we examined the incidences of GI bleeding and major adverse cardiac events (MACE) including stent thrombosis. The incidence of GI bleeding was not significantly different between the groups (hazard ratio 0.47 [95% confidence interval 0.15-1.42], P=0.18; P=0.17 in log-rank test), although no patient with severe bleeding was observed in the rabeprazole group. The use of rabeprazole did not increase the incidence of MACE (hazard ratio 1.28 [95% confidence interval 0.54-3.00], P=0.56; P=0.56 in log-rank test). One patient who developed subacute stent thrombosis under DAT was genetically proven to be a CYP2C19 poor metabolizer. The effect of rabeprazole to prevent GI bleeding is limited in patients receiving DAT. It remains to be confirmed whether these results may depend on CYP2C19 polymorphisms or a class of PPIs.

Differences in associated factors between aortic and mitral valve calcification in hemodialysis.

Increased prevalence of aortic and mitral valve calcification has been reported in patients on hemodialysis, but it remains unknown whether aortic and mitral valve calcification arise from similar pathogenesis. We detected heart valve calcification using two-dimensional echocardiography, and we related valve calcification to various clinical parameters in patients treated with hemodialysis three times a week for more than 1 year. In 112 patients (77 men and 35 women, age 67+/-10 years, duration on hemodialysis 95+/-67 months), aortic and mitral valve calcification were observed in 84 (75.0%) and 58 (51.7%) patients, respectively. Aortic valve calcification was associated with increased age, higher serum calcium, lower serum albumin, lower total cholesterol and higher high-sensitivity C-reactive protein. Multivariate analysis showed that increased age and higher serum calcium were independently associated with aortic valve calcification. Conversely, mitral valve calcification was associated with increased age, higher high-sensitivity C-reactive protein and higher serum beta(2)-microglobulin, but not with higher serum calcium. In multivariate analysis, increased age and higher serum beta(2)-microglobulin were independently associated with mitral valve calcification. Serum beta(2)-microglobulin was associated with longer duration on hemodialysis, malnutrition inflammation (lower serum albumin and higher high-sensitivity C-reactive protein) and dyslipidemia. Considering the results in previous studies showing that the distribution of beta(2)-microglobulin amyloid deposition was consistent with that of tissue calcification in patients on hemodialysis, beta(2)-microglobulin may have pathogenic roles in valve calcification.

Impact of coronary artery calcification in hemodialysis patients: Risk factors and associations with prognosis.

The risk factors of coronary artery calcification (CAC) and the impact of CAC on cardiovascular events, cardiovascular deaths, and all-cause deaths in hemodialysis (HD) patients have not been fully elucidated. We examined the CAC score (CACS) in 74 HD patients using electron-beam computed tomography. Fifty-six patients underwent a second electron-beam computed tomography after a 15-month interval to evaluate CAC progression. We evaluated (1) the risk factors for CAC and its progression and (2) the impact of CAC on the prognosis. In the cross-sectional study, HD vintage and high-sensitive C-reactive protein (hsCRP) were the independent risk factors for CAC. In the prospective cohort study, delta CACS (progression of CAC) was significantly correlated with hsCRP, fibrinogen, and serum calcium level in the univariate analysis. Stepwise multiple regression analysis revealed that only hsCRP was the independent risk factor for CAC progression in HD patients. Kaplan-Meier survival analysis revealed that cardiovascular events (P<0.0001), cardiovascular deaths (P=0.039), and all-cause deaths (P=0.026) were significantly associated with CACS. In conclusion, CAC had significantly progressed in HD patients during the 15-month observation period. Microinflammation was the only independent risk factor for CAC progression in HD patients. The advanced CAC was a significant prognostic factor in HD patients, i.e., which was strongly associated with future cardiovascular events, cardiovascular deaths, and all-cause deaths.

Postprandial hyperglycemia and hyperinsulinemia associated with renal arterio-arteriolosclerosis in chronic kidney disease.

Hypertension has an important function in the formation of renal arterio-arteriolosclerosis. However, renal arterio-arteriolosclerosis is sometimes found in biopsy specimens of normotensive patients, which indicates unknown factors may contribute to renal arterio-arteriolosclerosis. In this study, we aimed to evaluate the effects of glucose metabolism/insulin resistance on renal arterio-arteriolosclerosis. Forty-eight patients with biopsy-proven non-diabetic chronic glomerular disease were included. Renal arterio-arteriolosclerosis was evaluated as the percentage of vessels showing hyaline changes or wall thickening. We correlated renal arterio-arteriolosclerosis with clinical parameters including indices obtained by 75 g oral glucose tolerance test. Of the 48 patients, 30 had hypertension. The results of univariate analysis showed significant association of renal arterio-arteriolosclerosis with hypertension, increased serum creatinine (S-Cr), hypertriglyceridemia, increased 2-h plasma glucose (PG) and increased 2-h plasma insulin (PI). In stepwise multiple regression analysis, hypertension (beta=0.344, P=0.009), S-Cr (beta=0.287, P=0.03) and 2-h PG (beta=0.274, P=0.03) were independently associated with renal arterio-arteriolosclerosis. Eleven of the 30 hypertensive patients did not have renal arterio-arteriolosclerosis. The hypertensive patients with renal arterio-arteriolosclerosis showed significantly higher 2-h PG (134+/-25 vs. 106+/-26 mg per 100 ml, P=0.008) and higher 2-h PI (67.7+/-34.9 vs. 48.3+/-30.0 microU ml(-1), P=0.04) compared with those without renal arterio-arteriolosclerosis, but the difference in S-Cr was not significant. Postprandial hyperglycemia and hyperinsulinemia may contribute to the formation of renal arterio-arteriolosclerosis independently of hypertension.

Increased leukocyte aggregates are associated with atherosclerosis in patients with hemodialysis.

Little data are available on the role of blood rheology in atherosclerosis in hemodialysis (HD) patients. This study sought to assess the relationship between leukocytes conjugated with platelets (leukocyte aggregates [LA]) and atherosclerosis in patients with HD. The present study included 118 patients on HD. As surrogate markers of atherosclerosis, aortic stiffness measured by brachial-ankle pulse wave velocity, and carotid intima-media thickness (IMT) were measured. As an assessment of LA, a method, microchannel array flow analyzer, which makes it possible to directly observe the flow of blood cell elements through the microchannel, was used. We measured a number of LA during 50 microL flow of whole blood through microchannels. In 12 age-matched healthy individuals, a number of LA during 50 microL flow of whole blood was 25.7+/-5.4, whereas in HD patients it was significantly increased up to 48.2+/-16.4 (P<0.001). Flow cytometry demonstrated that LA were predominantly monocytes. Leukocyte aggregates were positively associated with plasma levels of fibrinogen (P<0.01), or serum high-sensitive C-reactive protein (P<0.01). Moreover, LA had highly significant associations with brachial-ankle pulse wave velocity (P<0.001) and IMT (P<0.001). In conclusion, we demonstrated hemorheologically that monocyte-platelet conjugates play an important role in aortic stiffness and IMT in HD patients.

High-density lipoprotein cholesterol and left ventricular mass index in peritoneal dialysis.

OBJECTIVE: The prevalence of left ventricular hypertrophy (LVH) reaches 75% in patients with end-stage renal disease. In patients on peritoneal dialysis (PD), some factors, such as hypertension, volume overload, serum albumin, and residual renal function, have been reported to be related to LVH. Dyslipidemia often occurs in PD but it remains unclear whether dyslipidemia is related to LVH. We investigated the relationship between clinical parameters, including lipid profile, and left ventricular mass index (LVMI). METHODS: In this cross-sectional study, 34 patients undergoing PD for more than 1 year without combined therapy with hemodialysis were included. We recorded the patients' clinical data and related those parameters with LVMI as evaluated by echocardiography. RESULTS: The patients included 23 males and 11 females (age 62.2 +/- 12.1 years, duration on PD 31.6 +/- 15.6 months). Mean LVMI was 142 +/- 37 g/m2. In univariate analysis, urine volume (r = -0.493, p = 0.003), total cholesterol (r = -0.418, p = 0.01), high-density lipoprotein cholesterol (HDL-C; r = -0.374, p = 0.02), and human atrial natriuretic peptide (hANP; r = 0.600, p < 0.001) significantly correlated with LVMI. Stepwise multiple regression analysis showed that hANP (beta = 0.524, p = 0.001) and HDL-C (beta = -0.422, p = 0.007) were independently associated with LVMI (r2 = 0.32). CONCLUSION: Strict volume control and salt restriction is essential for prevention of LVH. The role of HDL-C in the development of LVH in PD patients remains to be determined.