Effect of High Sodium Intake on Gut Tight Junctions' Structure and Permeability to Bacterial Toxins in a Rat Model of Chronic Kidney Disease

INTRODUCTION

Uremic toxicity changes the gut structure and permeability, allowing bacterial toxins to translocate from the lumen to the blood during chronic kidney failure (CKD). Clinical fluid overload and tissue edema without uremia have similar effects but have not been adequately demonstrated and analyzed in CKD.

AIMS

To investigate the effect of sodium intake on the plasma concentration of gut-derived uremic toxins, indoxyl sulfate (IS), and p-cresyl sulfate (pCS) and the expression of genes and proteins of epithelial gut tight junctions in a rat model of CKD.

METHODS

Sham-operated (control group, CG) and five-sixths nephrectomized (5/6Nx) Sprague-Dawley rats were randomly assigned to low (LNa), normal (NNa), or high sodium (HNa) diets., Animals were then sacrificed at 8 and 12 weeks and analyzed for IS and pCS plasma concentrations, as well as for gene and protein expression of thigh junction proteins, and transmission electron microscopy (TEM) in colon fragments.

RESULTS

The HNa 5/6Nx groups had higher concentrations of IS and pCS than CG, NNa, and LNa at eight and twelve weeks. Furthermore, HNa 5/6Nx groups had reduced expression of the claudin-4 gene and protein than CG, NNa, and LNa. HNa had reduced occludin gene expression compared to CG. Occludin protein expression was more reduced in HNa than in CG, NNa, and LNa. The gut epithelial tight junctions appear dilated in HNa compared to NNa and LNa in TEM.

CONCLUSION

Dietary sodium intake and fluid overload have a significant role in gut epithelial permeability in the CKD model.

Role of thyroid hormones and mir-208 in myocardial remodeling in 5/6 nephrectomized rats

BACKGROUND AND AIMS

Thyroid hormones exert important effects on heart remodeling through mir-208. The process may have a role in myocardial changes in chronic kidney disease where thyroid abnormalities are common. In this study the effect of T4 supplementation on left ventricle (LV) remodeling in 5/6 nephrectomized rats (5/6Nx) was analyzed.

METHODS

5/6Nx rats and 5/6Nx under T4 supplementation (5/6Nx + T4) were compared with control (C) and thyroidectomized (Tx) rats. After 8 weeks of follow-up, LV was analyzed for α-MHC, β-MHC, TGF-β, and mir-208 expression, hydroxyproline content, and myocardial fibrosis. Serum collagenase activity was also analyzed.

RESULTS

Heart weight increased in 5/6Nx rats compared to C, which was prevented with T4 supplementation (C, 1.5 ± 0.04; 5/6Nx, 1.8 ± 0.09; 5/6Nx + T4, 1.6 ± 0.07 g, p <0.05). The same pattern was seen for LV wall thickness, hydroxyproline content, LV fibrosis, and mRNA TGF-β expression (C, 0.47 ± 0.17; 5/6Nx, 10.55 ± 3.4; 5/6Nx + T4, 3.01 ± 0.52, p <0.01). Tx rats had reduction in heart weight, increased LV wall thickness, and fibrosis. Collagenase activity did not change in any group. mRNA expression of α-, β-MHC, and TGF-β increased in 5/6Nx in comparison to C and 5/6Nx + T4. Expression of mir-208 decreased in 5/6Nx groups, and levels were restored with T4 supplementation (4.21 ± 0.28, 3.39 ± 0.29, and 4.26 ± 0.37 RU, respectively, p <0.01).

CONCLUSIONS

Decreased plasma level of thyroid hormones or sensitivity at tissue level observed in chronic kidney disease induced by 5/6Nx has an important effect in heart remodeling processes, some of it related or mediated by mir-208 and TGF-β expression in the heart.

Icodextrin improves metabolic and fluid management in high and high-average transport diabetic patients

BACKGROUND

Icodextrin-based solutions (ICO) have clinical and theoretical advantages over glucose-based solutions (GLU) in fluid and metabolic management of diabetic peritoneal dialysis (PD) patients; however, these advantages have not yet been tested in a randomized fashion.

OBJECTIVE

To analyze the effects of ICO on metabolic and fluid control in high and high-average transport diabetic patients on continuous ambulatory PD (CAPD).

PATIENTS AND METHODS

A 12-month, multicenter, open-label, randomized controlled trial was conducted to compare ICO (n = 30) versus GLU (n = 29) in diabetic CAPD patients with high-average and high peritoneal transport characteristics. The basic daily schedule was 3 x 2 L GLU (1.5%) and either 1 x 2 L ICO (7.5%) or 1 x 2 L GLU (2.5%) for the long-dwell exchange, with substitution of 2.5% or 4.25% for 1.5% GLU being allowed when clinically necessary. Variables related to metabolic and fluid control were measured each month.

RESULTS

Groups were similar at baseline in all measured variables. More than 66% of the patients using GLU, but only 9% using ICO, needed prescriptions of higher glucose concentration solutions. Ultrafiltration (UF) was higher (198 +/- 101 mL/day, p < 0.05) in the ICO group than in the GLU group over time. Changes from baseline were more pronounced in the ICO group than in the GLU group for extracellular fluid volume (0.23 +/- 1.38 vs -1.0 +/- 1.48 L, p < 0.01) and blood pressure (systolic 1.5 +/- 24.0 vs -10.4 +/- 30.0 mmHg, p < 0.01; diastolic 1.5 +/- 13.5 vs -6.2 +/- 14.2 mmHg, p < 0.01). Compared to baseline, patients in the ICO group had better metabolic control than those in the GLU group: glucose absorption was more reduced (-17 +/- 44 vs -64 +/- 35 g/day) as were insulin needs (3.6 +/- 3.4 vs - 9.1 +/- 4.7 U/day, p < 0.01), fasting serum glucose (8.3 +/- 36.5 vs -37 +/- 25.8 mg/dL, p < 0.01), triglycerides (54.5 +/- 31.9 vs -54.7 +/- 39.9 mg/dL, p < 0.01), and glycated hemoglobin (0.79% +/- 0.79% vs -0.98% +/- 0.51%, p < 0.01). Patients in the ICO group had fewer adverse events related to fluid and glucose control than patients in the GLU group.

CONCLUSION

Icodextrin represents a significant advantage in the management of high transport diabetic patients on PD, improving peritoneal UF and fluid control and reducing the burden of glucose overexposure, thereby facilitating metabolic control.

Inflammation and extracellular volume expansion are related to sodium and water removal in patients on peritoneal dialysis

BACKGROUND

Inflammation is an important risk for mortality in dialysis patients. Extracellular fluid volume (ECFv) expansion, a condition commonly seen in peritoneal dialysis (PD) patients, may be associated with inflammation. However, published support for this relationship is scarce.

OBJECTIVES

To quantify the proportion of patients on PD with inflammation and to analyze the role of ECFv expansion and the factors related to these conditions.

DESIGN

A prospective, multicenter cross-sectional study in six hospitals with a PD program.

PATIENTS AND METHODS

Adult patients on PD were studied. Clinical data, body composition, and sodium and fluid intake were recorded. Biochemical analysis, C-reactive protein (CRP), and peritoneal and urinary fluid and sodium removal were also measured.

RESULTS

CRP values positive (>or=3.0 mg/L) for inflammation were found in 147 (80.3%) and negative in 36 patients. Patients with positive CRP had higher ECFv/total body water (TBW) ratio (women 47.69 +/- 0.69 vs 47.36 +/- 0.65, men 43.15 +/- 1.14 vs 42.84 +/- 0.65; p < 0.05), higher serum glucose (125.09 +/- 81.90 vs 103.28 +/- 43.30 mg/dL, p < 0.03), and lower serum albumin (2.86 +/- 0.54 vs 3.17 +/- 0.38 g/dL, p < 0.001) levels. They also had lower ultrafiltration (1003 +/- 645 vs 1323 +/- 413 mL/day, p < 0.005) and total fluid removal (1260 +/- 648 vs 1648 +/- 496 mL/day, p < 0.001), and less peritoneal (15.59 +/- 162.14 vs 78.11 +/- 110.70 mEq/day, p < 0.01) and total sodium removal (42.06 +/- 142.49 vs 118.60 +/- 69.73 mEq/day, p < 0.001). In the multivariate analysis, only ECFv/TBW was significantly (p < 0.04) and independently associated with inflammation. ECFv/TBW was correlated with fluid removal (r = 0.16, p < 0.03) and renal sodium removal (r = 0.2, p < 0.01).

CONCLUSION

The data suggest that ECFv expansion may have a significant role as an inflammatory stimulus. The results disclose a relationship between the two variables, ECFv expansion and inflammation, identified as independent risk factors for mortality in PD patients.