The progression from mild to severe hyperglycemia coupled with insulin resistance causes mitochondrial dysfunction and alters the metabolic secretome of epithelial kidney cells.

Diabetic nephropathy (DN) and insulin resistance (IR) in kidney cells are considered main causes for end-stage renal failure. However, it is unclear how IR affects early stages of the disease. Here, we investigate the impact of mild (11 mM) and severe (22 mM) hyperglycemia, with and without induced IR, on cellular metabolism and mitochondrial bioenergetics in a human kidney cell line (HK-2). IR in HK-2 cells was induced with palmitic acid and cellular cytotoxicity was studied. We evaluated the impact of mild and severe hyperglycemia with and without IR on the metabolic secretome of the cells, their live-cell mitochondria function, mitochondrial membrane potential, and mitochondrial complex activities. Furthermore, we measured fatty acid oxidation and lipid accumulation. Cells cultured under mild hyperglycemic conditions exhibited increased mitochondrial bioenergetic parameters, such as basal respiration, ATP-linked production, maximal respiration capacity, and spare respiration capacity. However, these parameters decreased when cells were cultured under higher glucose concentrations when IR was induced. Our data suggests that progression from mild to severe hyperglycemia induces a metabolic shift, where gluconeogenic amino acids play a crucial role in supplying the energy requirements of HK-2. To our knowledge, this is the first study to evaluate the progression from mild to severe hyperglycemia allied to IR in human kidney cells. This work highlights that this progression leads to mitochondrial dysfunction and alters the metabolic profile of kidney cells. These results identify possible targets for early intervention in DN.

Mitochondrial Pathophysiology on Chronic Kidney Disease.

In healthy kidneys, interstitial fibroblasts are responsible for the maintenance of renal architecture. Progressive interstitial fibrosis is thought to be a common pathway for chronic kidney diseases (CKD). Diabetes is one of the boosters of CKD. There is no effective treatment to improve kidney function in CKD patients. The kidney is a highly demanding organ, rich in redox reactions occurring in mitochondria, making it particularly vulnerable to oxidative stress (OS). A dysregulation in OS leads to an impairment of the Electron transport chain (ETC). Gene deficiencies in the ETC are closely related to the development of kidney disease, providing evidence that mitochondria integrity is a key player in the early detection of CKD. The development of novel CKD therapies is needed since current methods of treatment are ineffective. Antioxidant targeted therapies and metabolic approaches revealed promising results to delay the progression of some markers associated with kidney disease. Herein, we discuss the role and possible origin of fibroblasts and the possible potentiators of CKD. We will focus on the important features of mitochondria in renal cell function and discuss their role in kidney disease progression. We also discuss the potential of antioxidants and pharmacologic agents to delay kidney disease progression.

Health-related quality of life may improve after transplantation in pancreas-kidney recipients.

Pancreas-kidney transplantation (PKT) may significantly improve quality of life (HRQOL) in patients with type 1 diabetes. We have assessed the changes felt by PKT patients, using the Gastrointestinal Quality of Life Index (GIQLI) and EuroQol-5D questionnaires. Patients were asked to compare how their HRQOL had changed from pre-transplantation to the last visit. The 60 men and 66 women enrolled had a mean follow-up of five yr; 84.1% with both grafts, 15.9% with one graft functioning. In all domains of EuroQol-5D scores improved after PKT, as well as the visual analogue scale health state (from 38% to 84%, p < 0.001; effect size 3.34). In GIQLI, physical function was felt better after PKT than before (14.83 ± 3.86 vs. 7.86 ± 4.43, p < 0.001; effect size 1.68); the same was observed for psychological status, social function, and GI complaints. Concerning the burden of medical treatment, the score significantly improved (from 1.31 to 3.63, p < 0.001, effect size 2.02). The rate of unemployed patients decreased after PKT (from 50.8% to 36.5%, p < 0.001). Multivariate analysis showed that having only one functioning graft was associated with worse HRQOL scores (B = -5.157, p = 0.015). In conclusion, for all assessed domains, patients reported a significant improvement in HRQOL after PKT. Maintenance of the two grafts functioning predicted higher improvement of HRQOL scores.

Pancreatic autoantibodies after pancreas-kidney transplantation - do they matter?

Type 1 diabetes recurrence has been documented in simultaneous pancreas-kidney transplants (SPKT), but this diagnosis may be underestimated. Antibody monitoring is the most simple, noninvasive, screening test for pancreas autoimmune activity. However, the impact of the positive autoimmune markers on pancreas graft function remains controversial. In our cohort of 105 SPKT, we studied the cases with positive pancreatic autoantibodies. They were immunosuppressed with antithymocyte globulin, tacrolimus, mycophenolate, and steroids. The persistence or reappearance of these autoantibodies after SPKT and factors associated with their evolution and with graft outcome were analyzed. Pancreatic autoantibodies were prospectively monitored. Serum samples were collected before transplantation and at least once per year thereafter. At the end of the follow-up (maximum 138 months), 43.8% of patients were positive (from pre-transplant or after recurrence) for at least one autoantibody - the positive group. Antiglutamic acid decarboxylase was the most prevalent (31.4%), followed by anti-insulin (8.6%) and anti-islet cell autoantibodies (3.8%). Bivariate analysis showed that the positive group had higher fasting glucose, higher glycated hemoglobin (HbA1c), lower C-peptide levels, and a higher number of HLA-matches. Analyzing the sample divided into four groups according to pre-/post-transplant autoantibodies profile, the negative/positive group tended to present the higher HbA1c values. Multivariate analysis confirmed the significant association between pancreas autoimmunity and HbA1c and C-peptide levels. Positivity for these autoantibodies pre-transplantation did not influence pancreas survival. The unfavorable glycemic profile observed in the autoantibody-positive SPKT is a matter of concern, which deserves further attention.

Peritoneal dialysis in anuric patients: old problems and new perspectives.

Anuric patients are often excluded from peritoneal dialysis (PD) because of the fear that PD is inadequate to treat this higher-risk group of patients. However, advances in PD knowledge and technique allow better and adjusted treatments. There is now clinical evidence that anuric patients can be successfully treated with PD, while new solutions promise to mitigate some limitations of automated PD, such as sodium and fluid removal and preservation of membrane function.

Evaluation of peritoneal transport and membrane status in peritoneal dialysis: focus on incident fast transporters.

BACKGROUND/AIM: The determinants of baseline fast solute transport are still unclear. We prospectively investigated the relationship of peritoneal solute transport with markers of inflammation, angiogenesis, and membrane status, with a focus on fast transporters. METHODS: Seventy-one incident peritoneal dialysis patients were assessed with baseline and annual peritoneal equilibration tests, using a 3.86% glucose dialysis solution. Residual renal function and markers of inflammation, including systemic and intraperitoneal interleukin-6 (IL-6), effluent cancer antigen 125 (CA-125), and vascular endothelial growth factor (VEGF) appearance rates (ARs), were investigated. The time course of the dialysate-to-plasma ratio of creatinine (D/P creatinine ratio) and its relationship with the biomarkers were investigated by a mixed linear model. RESULTS: Incident fast/fast average transporters had a similar age, diabetes prevalence, and serum and effluent IL-6 levels, but significantly higher levels of CA-125 and VEGF ARs than the slow/slow average group; the D/P creatinine ratio was not correlated with systemic IL-6, but was correlated with effluent CA-125 AR (r = 0.45, p < 0.0001) and VEGF AR (r = 0.52, p < 0.0001). The D/P creatinine ratio decreased with a U-shaped profile (p = 0.02). Intraperitoneal IL-6 was the significant and positive determinant of the time course of the D/P creatinine ratio (p < 0.0001). Effluent CA-125 decreased with time on peritoneal dialysis (p = 0.013). CONCLUSIONS: Baseline peritoneal fast transport was not associated with systemic inflammation, but was related to peritoneal locally produced substances able to mediate transitory hyperpermeability. The D/P creatinine ratio changed during the follow-up period with a U-shaped profile. This was associated with effluent IL-6 and partly with VEGF. CA-125 decreased throughout the follow-up period.

Peritoneal membrane evaluation in routine clinical practice.

BACKGROUND/AIMS: Establishment of reference values for small solute transport, sodium sieving and effluent CA125 with 3.86% (4 h) peritoneal equilibration test (PET), and comparison with fast-fast PET with regard to small solute transport categories. METHODS: Cross-sectional study; 69 prevalent patients. Sodium sieving corrected for sodium diffusion with a formula applicable to the PET. CA125 appearance rate (AR) was measured. Expected and observed 60 min D/P(creatinine) were compared by Bland and Altman. RESULTS: Means (95% CI): D/P(creatinine) 0.73 (0.70-0.76), MTAC(creatinine) 9.6 (8.4-10.9) ml/min, D/D0 glucose 0.30 (0.28-0.31), corrected dip 0.17 (0.15-0.18), CA125 150 (125-176) U/min. Both corrected and uncorrected sodium sieving were informative. Peritoneal transport was faster at 60 min dwell. UFF patients presented very low corrected dip and CA125 AR. CONCLUSION: 3.86% (4 h) PET provided results similar to those from SPA. Correction for diffusion of sodium sieving is dispensable for simple clinical evaluations. D/P(creatinine) at 60 min overestimated small solute transport rate. Effluent CA125 was consistently lower in UFF patients.

Peritoneal fast transport in incident peritoneal dialysis patients is not consistently associated with systemic inflammation.

BACKGROUND: The determinants of peritoneal fast transport status at the beginning of peritoneal dialysis (PD) are still under debate. The relationship between fast transport status and inflammation or co-morbidity, and its impact on patient survival are not fully elucidated. Our objective was to investigate if fast transport status in incident patients is associated with markers of inflammation and atherosclerosis, and its relationship to patient survival. METHODS: Seventy-three incident patients on PD performed a 3.86% peritoneal equilibrium test (PET) at 4.7+/-2.7 months after starting PD. Doppler carotid wall intima-media thickness (IMT) and the presence of carotid plaque were used as markers of atherosclerosis. C-reactive protein (CRP) and serum interleukin-6 (IL-6) were evaluated as markers of systemic inflammation. Baseline plasma levels of albumin, homocysteine, lipoprotein (a) [Lp(a)] and other lipid parameters were measured. Body mass index and residual renal function (RRF) were calculated. Patients were classified with the Davies co-morbidity score. RESULTS: The dialysate-plasma creatinine ratio (D/P creatinine) was 0.75 +/- 0.10; 26% were fast transporters (D/P > or = 0.85). In comparison with other transport categories, these had similar age, body mass index and RRF, and did not present a higher co-morbidity score than non-fast transporters. IMT did not significantly differ between groups. By multiple regression analysis, baseline peritoneal small solute transport was not related to systemic inflammation biomarkers. Fast transporters did not present higher levels of CRP or serum IL-6. Plasma levels of lipids, Lp(a), calcium x phosphorus product and albumin also did not differ between groups. Similar results were obtained when patients were grouped according to mass transfer area coefficient for creatinine. Patients with more than two co-morbidities had lower levels of plasma albumin (3.6 +/- 0.58 vs 3.9 +/- 0.9 g/dl, P = 0.054), significantly higher median levels of serum IL-6 (19.3 vs 9.2 pg/ml, P = 0.003) and wider IMT (0.90 +/- 0.36 vs 0.65 +/- 0.28 mm, P = 0.017). Multivariate analysis confirmed that baseline peritoneal transport was not a significant determinant of patient survival (P = 0.848), while the co-morbidity score remained significant (hazard ratio = 3.48, 95% confidence interval = 1.29-9.38, P = 0.014). CONCLUSION: Initial fast transport was not associated with systemic inflammation and atherosclerosis. In a population with preserved RRF and absence of baseline serious co-morbidity, it was not predictive of worse prognosis. Other determinants of early peritoneal fast transport deserve investigation.

Longitudinal membrane function in functionally anuric patients treated with APD: data from EAPOS on the effects of glucose and icodextrin prescription.

BACKGROUND: Peritoneal dialysis is associated with changes in membrane function that can lead eventually to ultrafiltration (UF) failure. Factors driving these changes are thought to include hypertonic glucose exposure, but previously reported associations are confounded by the presence of residual renal function. METHODS: Longitudinal membrane function (solute transport and UF capacity) were measured annually in a prospective cohort of 177 functionally anuric patients as part of the European Automated Peritoneal Dialysis Outcomes Study (EAPOS). Subgroup analysis was performed according to glucose exposure and icodextrin use at baseline. RESULTS: The whole cohort experienced an increase in solute transport and reduction in UF capacity at 12 and 24 months that could not be explained by informative censoring. These changes were accelerated and more severe in patients using either 2.27% or 3.86% glucose, or those not using icodextrin at baseline. These differences could not be explained by age, comorbidity score, previous time spent on renal replacement, differential dropout from the study, peritonitis rates, or, by definition, residual renal function. Patients using icodextrin at baseline had worse membrane function and were more likely to be diabetic. There was an association between membrane function changes and achieved 24-hour ultrafiltration over the 2-year study period. CONCLUSION: Anuric automated peritoneal dialysis (APD) patients experience significant detrimental changes in membrane function over a relatively short time period. Glucose appears to enhance these changes independent of residual renal function. Icodextrin use in these circumstances is associated with less deterioration in membrane function.