SA-ß-Gal in Kidney Tubules as a Predictor of Renal Outcome in Patients with Chronic Kidney Disease.

Cellular senescence has emerged as an important driver of aging and age-related disease in the kidney. The activity of ß-galactosidase at pH 6 (SA-ß-Gal) is a classic maker of senescence in cellular biology; however, the predictive role of kidney tissue SA-ß-Gal on eGFR loss in chronic kidney disease (CKD) is still not understood. We retrospectively studied the expression of SA-ß-Gal in kidney biopsies obtained in a cohort [n = 22] of incident patients who were followed up for 3 years as standard of care. SA-ß-Gal staining was approximately fourfold higher in the tubular compartment of patients with CKD vs. controls [26.0 ± 9 vs. 7.4 ± 6% positive tubuli in patients vs. controls; p < 0.025]. Tubular expressions of SA-ß-Gal, but not proteinuria, at the time of biopsy correlated with eGFR loss at the follow up; moreover, SA-ß-Gal expression in more than 30% of kidney tubules was associated with fast progressive kidney disease. In conclusion, our study shows that SA-ß-Gal is upregulated in the kidney tubular compartment of adult patients affected by CKD and suggests that tubular SA-ß-Gal is associated with accelerated loss of renal function.

Interdialytic weight gain is not associated with symptoms of depression or apathy in patients on chronic hemodialysis.

PURPOSE: Little is known about the relationships between apathy, depressive symptoms and interdialytic weight gain (IDWG) in patients on chronic hemodialysis. Aim of the present study is to investigate the association between IDWG and symptoms of depression and apathy in hemodialysis patients. METHODS: A total of 139 chronic patients of the HD units between January 2020 and December 2021 were included in the present cross-sectional study. IDWG was calculated as the difference between the pre-HD weight and the weight registered after the previous session; the average of the sessions in a month was registered. Apathy Evaluation Scale (AES) was adopted to evaluate apathy. Depression was assessed by Beck Depression Inventory (BDI). RESULTS: Ninety-three patients had IDWG% ≤ 4 and 46 had an IDWG% > 4. Correlation between IDWG% and BDI as well that between IDWG% and AES were not statistically significant. Median BDI and mean AES did not differ significantly between the groups. In addition, 104 patients had a BDI < 16 and 35 had a BDI ≥ 6. Seventy-five patients had an AES score ≤ 35 and 63 had a AES score > 35. The IDWG (kg) and the IDWG% did not differ significantly between the two groups. CONCLUSION: IDWG is not associated with symptoms of depression or apathy in hemodialysis patients. Thus, these results may question if the use of behavioral intervention aimed at improving motivation is warranted in the hemodialysis population to reduce the IDWG.

Fatigue and apathy in patients on chronic hemodialysis.

INTRODUCTION: This study explores the link between fatigue and apathy in patients on chronic hemodialysis (HD). METHODS: One hundred thirty-nine chronic HD patients underwent the assessment of fatigue, apathy, depression, and their functional status, with the fatigue severity scale (FSS), the Apathy Evaluation Scale (AES), the beck depression inventory (BDI), the activity of daily living (ADL), and instrumental activity of daily living (IADL). RESULTS: Patients with high FSS had a significantly lower ADL and IADL score, higher BDI, Charlson Comorbidity Index, and AES score, and lower serum levels of creatinine, compared to low FSS patients. FSS was highly correlated with the AES, as well as with the BDI and the AES correlates with the BDI. At multiple regression analyses, only apathy and IADL were independent predictor variables of fatigue in HD population. CONCLUSION: Future longitudinal studies could determine if apathy is a causative factor for fatigue manifestation and development in HD patients.

Effects of Low-Protein, and Supplemented Very Low-Protein Diets, on Muscle Protein Turnover in Patients With CKD.

INTRODUCTION: Early studies have shown that patients with chronic kidney disease (CKD) are able to maintain nitrogen balance despite significantly lower protein intake, but how and to what extent muscle protein metabolism adapts to a low-protein diet (LPD) or to a supplemented very LPD (sVLPD) is still unexplored. METHODS: We studied muscle protein turnover by the forearm perfusion method associated with the kinetics of 2H-phenylalanine in patients with CKD: (i) in a parallel study in subjects randomized to usual diet (1.1 g protein/kg, n = 5) or LPD (0.55 g protein/kg, n = 6) (Protocol 1); (ii) in a crossover, self-controlled study in subjects on a 0.55 g/kg LPD followed by a sVLPD (0.45 g/kg + amino/ketoacids 0.1 g/kg, n = 6) (Protocol 2). RESULTS: As compared with a 1.1 g/kg containing diet, a 0.55 g/kg LPD induced the following: (i) a 17% to 40% decrease in muscle protein degradation and net protein balance, respectively, (ii) no change in muscle protein synthesis, (iii) a slight (by approximately 7%, P < 0.06) decrease in whole-body protein degradation, and (iv) an increase in the efficiency of muscle protein turnover. As compared with an LPD, an sVLPD induced the following: (i) no change in muscle protein degradation, and (ii) an approximately 50% decrease in the negative net protein balance, and an increase in the efficiency of muscle protein turnover. CONCLUSION: The results of these studies indicate that in patients with CKD the adaptation of muscle protein metabolism to restrained protein intake can be obtained via combined responses of protein degradation and the efficiency of recycling of amino acids deriving from protein breakdown.

Interorgan handling of fibroblast growth factor-23 in humans.

Fibroblast growth factor-23 (FGF-23) accumulates in blood of patients with chronic kidney disease (CKD) and is associated both with cardiovascular complications and disease progression. However, our knowledge of the sites and mechanisms that regulate plasma FGF-23 is still incomplete. We measured plasma intact FGF-23 across the kidney, splanchnic organs, and lung in 11 patients [estimated glomerular filtration rate (eGFR) 60 ± 6 ml/min] during elective diagnostic cardiac catheterizations. In these patients FGF-23 was removed by the kidney, with a fractional extraction (FE) of ∼22%. The FE of FGF-23 across the kidney was similar to that of creatinine (∼17%, P = NS). In addition, the FGF-23 FE by the kidney was significantly directly related to eGFR (r = 0.709 P = 0.018) and to kidney creatinine FE (r = 0.736 P = 0.013) but only as a trend to plasma phosphate levels (r = 0.55, P = 0.18). There was no difference in FGF-23 levels in blood perfusing splanchnic organs and cardiopulmonary bed. However, the arterial-venous difference of FGF-23 across the lung was directly related to FGF-23 pulmonary artery levels, suggesting that the lung, and possibly the heart, participate in the homeostasis of plasma FGF-23 when its systemic levels are increased. Our data show that the human kidney is the only site for FGF-23 removal from blood and suggest that FGF-23 is predominantly removed by glomerular filtration. The kidney ability to remove FGF-23 from the circulation likely accounts for the early increase in blood of FGF-23 in patients with CKD.

Toll-like receptor 4 signalling mediates inflammation in skeletal muscle of patients with chronic kidney disease.

BACKGROUND: Inflammation in skeletal muscle is implicated in the pathogenesis of insulin resistance and cachexia but why uremia up-regulates pro-inflammatory cytokines is unknown. Toll-like receptors (TLRs) regulate locally the innate immune responses, but it is unknown whether in chronic kidney disease (CKD) TLR4 muscle signalling is altered. The aim of the study is to investigate whether in CKD muscle, TLRs had abnormal function and may be involved in transcription of pro-inflammatory cytokine. METHODS: TLR4, phospho-p65, phospho-ikBα, tumour necrosis factor (TNF)-α, phospho p38, Murf 1, and atrogin were studied in skeletal muscle from nondiabetic CKD stage 5 patients (n = 29) and controls (n = 14) by immunohistochemistry, western blot, and RT-PCR. Muscle cell cultures (C2C12) exposed to uremic serum were employed to study TLR4 expression (western blot and RT-PCR) and TLR-driven signalling. TLR4 signalling was abrogated by a small molecule chemical inhibitor or TLR4 siRNA. Phospho AKT and phospho p38 were evaluated by western blot. RESULTS: CKD subjects had elevated TLR4 gene and protein expression. Also expression of NFkB, p38 MAPK and the NFkB-regulated gene TNF-α was increased. At multivariate analysis, TLR4 protein content was predicted by eGFR and Subjective Global Assessment, suggesting that the progressive decline in renal function and wasting mediate TLR4 activation. In C2C12, uremic serum increased TLR4 as well as TNF-α and down-regulated pAkt. These effects were prevented by blockade of TLR4. CONCLUSIONS: CKD promotes muscle inflammation through an up-regulation of TLR4, which may activate downward inflammatory signals such as TNF-α and NFkB-regulated genes.

Multidisciplinary evaluation at baseline and during treatment improves the rate of compliance and efficacy of deferasirox in elderly myelodysplastic patients.

BACKGROUND: Deferasirox (DFX) is used to reduce iron levels in patients with myelodysplastic syndrome (MDS) who develop iron overload after chronic red blood cell infusions. However, DFX can be associated with renal and gastrointestinal toxicities, which may cause treatment interruption or discontinuation. This study aimed to determine the effectiveness and safety of DFX in patients with MDS. METHODS: This multicenter, retrospective, observational study was conducted at two hospitals in Italy. Elderly patients with transfusion-dependent MDS received DFX for up to 12 months and were divided into two groups: group A comprised patients who were not under multidisciplinary assessment; group B comprised patients under multidisciplinary control. Treatment effectiveness was estimated by monitoring the serum ferritin (SF) levels throughout the study. Any treatment-related adverse events (AEs), clinically relevant analytical alterations, and reasons for treatment discontinuation were monitored. RESULTS: The study included 44 patients (13 female, 31 male; median age 77.0 years). At 3 months, SF levels decreased by ≥20 % in 29 and 31 % of patients in groups A and B, respectively, in 17 and 36 % of patients at 6 months, and in 22 and 58 % at 12 months. The most common AEs were diarrhea and increased serum creatinine, which were more frequent in group A. The discontinuation rate after renal AE was 15 and 5 % in groups A and B, respectively. CONCLUSION: Multidisciplinary evaluation can be an effective strategy for monitoring renal function in patients on DFX therapy, to improve treatment adherence and overall efficacy in elderly patients with MDS.

Uric acid promotes apoptosis in human proximal tubule cells by oxidative stress and the activation of NADPH oxidase NOX 4.

Mild hyperuricemia has been linked to the development and progression of tubulointerstitial renal damage. However the mechanisms by which uric acid may cause these effects are poorly explored. We investigated the effect of uric acid on apoptosis and the underlying mechanisms in a human proximal tubule cell line (HK-2). Increased uric acid concentration decreased tubule cell viability and increased apoptotic cells in a dose dependent manner (up to a 7-fold increase, p<0.0001). Uric acid up-regulated Bax (+60% with respect to Ctrl; p<0.05) and down regulated X-linked inhibitor of apoptosis protein. Apoptosis was blunted by Caspase-9 but not Caspase-8 inhibition. Uric acid induced changes in the mitochondrial membrane, elevations in reactive oxygen species and a pronounced up-regulation of NOX 4 mRNA and protein (p<0.05). In addition, both reactive oxygen species production and apoptosis was prevented by the NADPH oxidase inhibitor DPI as well as by Nox 4 knockdown. URAT 1 transport inhibition by probenecid and losartan and its knock down by specific siRNA, blunted apoptosis, suggesting a URAT 1 dependent cell death. In summary, our data show that uric acid increases the permissiveness of proximal tubule kidney cells to apoptosis by triggering a pathway involving NADPH oxidase signalling and URAT 1 transport. These results might explain the chronic tubulointerstitial damage observed in hyperuricaemic states and suggest that uric acid transport in tubular cells is necessary for urate-induced effects.

[Untold stories of kidney metabolism]. / Il metabolismo renale: alcune storie non ancora raccontate.

In the last decades, many progress has been made in our understanding of kidney metabolism and transport of a wide amount of solutes. The purpose of this review is to highlight some issues of kidney metabolism which are still not completely understood and that are nonetheless implicated in the pathophysiology of chronic kidney disease. These untold stories include the recently discovered ammonium transporter proteins Rh and the role of ammonium in causing kidney hypertrophy and renal damage; the role of the human kidney methionine metabolism on epigenetics and the effects of accelerated glucose reabsorption in the proximal tubule on tubulointerstitial damage in diabetic nephropathy. These issues have potential clinical applications and can be a starting point for future research in kidney disease.