Chronic kidney disease progression in native and transplant kidneys

The Role of Ketone Bodies in Various Animal Models of Kidney Disease

The kidney is a vital organ that carries out significant metabolic functions in our body. Due to the complexity of its role, the kidney is also susceptible to many disease conditions, such as acute kidney injury (AKI) and chronic kidney disease (CKD). Despite the prevalence and our increased understanding of the pathophysiology of both AKI and CKD as well as the transition of AKI to CKD, no well-established therapeutics have been applied clinically to these conditions, rendering an urgent need for a novel potential therapeutic target to be developed. In this article, we reviewed the function of ketone bodies in some common kidney conditions, such as drug-induced nephrotoxicity, ischemia and reperfusion injury, fibrosis development, diabetic kidney disease, kidney aging, hypertension, and CKD progression. All the selected studies reviewed were performed in animal models by primarily utilizing rodents, which also provide invaluable sources for future clinical applications. Ketone bodies have shown significant renal protective properties via attenuation of oxidative stress, increased expression of anti-inflammatory proteins, gene regulation, and a reduction of apoptosis of renal cells. A physiological level of ketone bodies could be achieved by fasting, a ketogenic diet, and an exogenous ketone supplement. Finally, the limitations of the long-term ketogenic diet were also discussed.

Endophilin A2 protects against renal fibrosis by targeting TGF-β/Smad signaling

Renal fibrosis underlies all forms of end-stage kidney disease. Endophilin A2 (EndoA2) plays a role in nephrotic syndrome; however, its effect on renal fibrosis remains unknown. Here, we demonstrate that EndoA2 protects against kidney interstitial fibrosis via the transforming growth factor-β (TGF-β)/Smad signaling pathway. Mouse kidneys with fibrosis or kidney biopsy specimens from patients with fibrotic nephropathy had lower levels of EndoA2 protein expression than that in kidneys without fibrosis. In vivo overexpression of EndoA2 with the endophilin A2 transgene (EndoA2^Tg ) notably prevented renal fibrosis, decreased the protein expression of profibrotic molecules, suppressed tubular injury, and reduced apoptotic tubular cells in the obstructed kidney cortex of mice with unilateral ureteral obstruction (UUO). In vivo and in vitro overexpression of EndoA2 markedly inhibited UUO- or TGF-β1-induced phosphorylation of Smad2/3 and tubular epithelial cells dedifferentiation. Furthermore, EndoA2 was co-immunoprecipitated with the type II TGF-β receptor (TβRII), thus inhibiting the binding of the type I TGF-β receptor (TβRI) to TβRII. These findings indicate that EndoA2 mitigates renal fibrosis, at least partially, via modulating the TGF-β/Smad signaling. Targeting EndoA2 may be a new potential therapeutic strategy for treatment of renal fibrosis.

Challenges in the Management of the Patient with a Failing Kidney Graft: A Narrative Review

Patients with a failed kidney allograft have steadily increase in recent years and returning to dialysis after graft loss is one of the most difficult transitions for chronic kidney disease patients and their assistant physicians. The management of these patients is complex and encompasses the treatment of chronic kidney disease complications, dialysis restart and access planning, immunosuppression withdrawal, graft nephrectomy, and evaluation for a potential retransplant. In recent years, several groups have focused on the management of the patient with a failing renal graft and expert recommendations are arising. A review of Pubmed, ScienceDirect and the Cochrane Library was performed focusing on the specific care of these patients, from the management of low clearance complications to concerns with a subsequent kidney transplant. Conclusion: There is a growing interest in the failing renal graft and new approaches to improve these patients’ outcomes are being defined including specific multidisciplinary programs, individualized immunosuppression withdrawal schemes, and strategies to prevent HLA sensitization and increase retransplant rates.

Non-Immunologic Causes of Late Death-Censored Kidney Graft Failure: A Personalized Approach

Despite continuous advances in surgical and immunosuppressive protocols, the long-term survival of transplanted kidneys is still far from being satisfactory. Antibody-mediated rejection, recurrent autoimmune diseases, and death with functioning graft are the most frequent causes of late-kidney allograft failure. However, in addition to these complications, a number of other non-immunologic events may impair the function of transplanted kidneys and directly or indirectly lead to their failure. In this narrative review, we will list and discuss the most important nonimmune causes of late death-censored kidney graft failure, including quality of the donated kidney, adherence to prescriptions, drug toxicities, arterial hypertension, dyslipidemia, new onset diabetes mellitus, hyperuricemia, and lifestyle of the renal transplant recipient. For each of these risk factors, we will report the etiopathogenesis and the potential consequences on graft function, keeping in mind that in many cases, two or more risk factors may negatively interact together.

Blockade of Orai1 Store-Operated Calcium Entry Protects against Renal Fibrosis

Evidence supports an important role of Ca²⁺ release-activated Ca²⁺ channel protein 1 (Orai1)-mediated Ca²⁺ entry in the development of renal fibrosis, a common pathologic feature of CKDs that lead to ESRD, but the molecular mechanisms remain unclear. We determined the role of Orai1 calcium channel in renal fibrosis induced by high-fat diet and by unilateral ureteral obstruction. Mouse kidneys with fibrosis had higher levels of Orai1 protein expression than did kidneys without fibrosis. In vivo knockdown of Orai1 with adenovirus harboring Orai1-short hairpin RNA or inhibition of Orai1 with SKF96365 dramatically prevented renal fibrosis and significantly decreased protein expression of fibronectin, α‑smooth muscle actin, and TGF‑β1 in the kidney cortex of ApoE^-/- mice on a high-fat diet and in the obstructed kidneys of mice with unilateral ureteral obstruction. Compared with kidney biopsy specimens of patients with glomerular minimal change disease, those of patients with fibrotic nephropathy had higher expression levels of Orai1. In cultured human proximal tubule epithelial cells (HK2), knockdown of Orai1 Ca²⁺ channel with adenovirus-Orai1-short hairpin RNA markedly inhibited TGF-β1-induced intracellular Ca²⁺ influx and phosphorylation of smad2/3. Knockdown or blockade of the Orai1 Ca²⁺ channel in HK2 cells also prevented epithelial-to-mesenchymal transition induced by TGF‑β1. In conclusion, blockade of the Orai1 Ca²⁺ channel prevented progression of renal fibrosis in mice, likely by suppressing smad2/3 phosphorylation and TGF-β1-induced epithelial-to-mesenchymal transition. These results render the Orai1 Ca²⁺ channel a potential therapeutic target against renal fibrosis.

Cardiovascular and renal outcome in recipients of kidney grafts from living donors: role of aortic stiffness

BACKGROUND

Cardiovascular (CV) risk remains high in renal transplant patients despite a clear improvement conferred by transplantation. This risk is attributed mostly to recipient-related risk factors. Donor vascular characteristics, such as arterial stiffness, have been poorly investigated in this regard.

METHODS

Recipients of living-related (n = 75) and living-unrelated (n = 20) kidney grafts were recruited at a mean time of 107 ± 41 months after transplantation for baseline evaluation and follow-up for the occurrence of the following composite outcome: myocardial infarction, stroke, CV death, doubling of serum creatinine or development of end-stage renal disease (ESRD). At inclusion, recipients and their corresponding donors underwent complete history, physical examination, laboratory tests and non-invasive measurement of aortic pulse wave velocity (PWV).

RESULTS

During a mean follow-up of 56 ± 18 months, 20 recipients doubled their serum creatinine, of whom 16 reached ESRD, and 9 suffered of a new CV event (5 of which were fatal). Cox proportional hazards regression analysis showed that, in addition to recipient-related parameters, such as the presence of CV event and the estimated glomerular filtration rate at inclusion, donor aortic PWV was a strong and independent predictor of the composite recipient outcome.

CONCLUSIONS

Donor large artery stiffness may predict recipient CV and graft outcome. This finding demonstrates the tight link that exists between the vascular system and the kidneys and suggests that donor contribution to recipient outcome goes beyond simple parameters like age, gender and even familial or non-familial donor type.

Prevalence and complications of chronic kidney disease in paediatric renal transplantation: a K/DOQI perspective

Background. Although renal transplant recipients (RTR) have been included as patients with chronic kidney disease (CKD) by the Kidney Disease Outcome Quality Initiative (K/DOQI), there are very few studies looking at CKD complications among paediatric RTR. Methods. CKD parameters of paediatric RTR with at least 1 year post-transplant follow-up were retrospectively reviewed as per K/DOQI criteria. Results. The study population included 129 RTR aged 2.7-20 (median 13.9) years, of which 67% were male and 87% Caucasian with follow-up between 1 and 14.8 (median 3.8) years. Sixty-six per cent of RTR were in either CKD Stage 3 (70) or 4 (15). A high incidence of CKD complications was identified (albuminuria 60%, anaemia 50%, acidosis 30%, hyperparathyroidism 20%, hypoalbuminaemia 16%, hyperphosphataemia 12% and hypocalcaemia 3%). Hypertension (defined as systolic blood pressure greater than 95th percentile for age and height or on any anti-hypertensive medication) was found in 53% (n = 68) of the study population, out of which 7% (n = 5) was having uncontrolled hypertension with systolic blood pressure greater than 95th percentile despite being on anti-hypertensive medication. There was an increase in complications (P = 0.0001) as well as use of CKD medications (erythropoietin-stimulating agent, sodium bicarbonate, 1-alfacalcidol and phosphate binders) across the CKD stages in RTR (P = 0.001). Conclusion. The study confirmed a high prevalence of CKD with its related complications along with increase in frequency of complications across the stages of CKD among paediatric RTR. Further multi-centre prospective studies are required to substantiate our findings and to explore whether early identification and intervention can improve renal allograft outcome.

Chronic renal failure in kidney transplant recipients. Do they receive optimum care?: data from the UK renal registry

We report the prevalence of chronic kidney disease (CKD) and related complications in a national cohort of RTR (n=9542), and compare this with dialysis patients. The majority of RTR were classified as having CKD stage 2T (21.6%) or 3T (57.5%) with 15.7% classified as CKD stage 4T and 3.1% as stage 5T. Only 2.1% of RTR were in CKD stage 1T. The proportion of patients with stage 4T and 5T CKD who lost their graft in the following year was 8% and 49%, respectively. The prevalence of anemia (hemoglobin <11 g/dL) increased from 4.4% in stage 1T to 51.5% in stage 5T and compared with 30% in dialysis patients (p<0.0001). Hypertension, hyperphosphatemia, elevated Ca x PO(4), raised iPTH and hypoalbuminemia rose with increasing CKD stage. For many variables, the achievement of standards was lower in stage 5T RTR than in dialysis patients. There were center differences in median estimated glomerular filtration rate and percentage of patients with hemoglobin <11 g/dL (p<0.0001). In conclusion, many patients in stage 4T-5T have CKD-related complications that fall below targets established for nontransplant CKD patients. They are at increased risk of graft loss. More attention needs to be paid to managing these complications and preparing these patients for a return to dialysis and/or retransplantation.

Aortic Stiffness, Living Donors, and Renal Transplantation

In subjects with renal disease, reduced renal function and increased arterial stiffness are significantly associated in cross-sectional studies. The relationship is independent of age, blood pressure (BP), and atherosclerosis. Because both variables are independent predictors of cardiovascular risk, time-dependent relationships between them are important to determine. Aortic pulse wave velocity was measured noninvasively by comparison with healthy volunteers in 101 living kidney donors and their 101 corresponding recipients. Healthy volunteers were divided into 2 groups: one was recipient related through familial links and the other was nonrecipient related. Independently of age, gender, and BP, pulse wave velocity was significantly elevated in donors and recipients by comparison with the 2 groups of healthy volunteers. Pulse wave velocity was significantly higher in the recipient-related than in the nonrecipient-related group. Whereas in healthy volunteers, pulse wave velocity was exclusively related to age, gender, and BP, in donors and recipients, it was rather associated with a cluster of cardiovascular risk factors, including smoking habits and plasma glucose. Major factors related to pulse wave velocity were renal: time since nephrectomy (donation date) in donors, in whom pulse pressure was specifically associated with proteinuria, and renal rejection in recipients. Plasma creatinine doubling secondary to chronic allograft nephropathy was significantly associated with renal rejection and donor pulse wave velocity, independent of age. Our findings strongly suggest consistent interactions (including familial factors) between kidney function and arterial stiffness. Assessment of cause–effect relationships and implication of biochemical and/or genetic factors warrant additional studies.

Non-immunologic intervention in chronic allograft nephropathy

BACKGROUND

Chronic allograft nephropathy is the main cause of late graft loss. It has been suggested that both alloantigen-dependent and alloantigen-independent factors influence the development of progressive transplant failure. The present study analyzed the importance of non-immunologic factors in the progression of kidney disease in transplant patients, with the emphasis on well-established risk factors for progression in native kidneys.

METHODS

A retrospective analysis was performed on 485 renal transplant patients who had functioning kidneys for at least 1 year. We investigated whether the initial presence and subsequent maintenance of proteinuria, hypertension, anemia, hyperlipidemia, and hyperparathyroidism influenced the progression of transplant failure. To analyze the relative effects of these factors, patients were categorized into two groups: group A had a baseline serum creatinine concentration of less than 1.5 mg/dL, and group B had a baseline serum creatinine concentration of 1.5 to 3 mg/dL.

RESULTS

High urine protein excretion was a significant independent risk factor for progression of renal failure (group A: relative risk, 3.73; 95% confidence interval [CI], 2.24-6.21; group B: relative risk, 4.01; 95% CI, 2.51-6.39). Hypertension was also a significant independent risk factor for progression, but the risk was lower than for proteinuria (group A: relative risk, 1.2; 95% CI, 1.04-1.75; group B: relative risk, 1.20; 95% CI, 1.02-2.1). Anemia, hyperlipidemia, and hyperparathyroidism had no influence on the progression of renal failure.

CONCLUSION

Our results show strong independent relationships between high blood pressure, urine protein excretion, and the relative risk of chronic progression of renal failure, as described for native kidney disease. These factors are potentially modifiable and are therefore attractive targets for therapeutic targets.

Managing the Failing Allograft

Managing the failing allograft juxtaposes immunosuppressive management and routine chronic kidney disease care. The complications of immunosuppression can be more pronounced in those with renal failure (infection, anemia, bone disease). The withdrawal of immunosuppression may be associated with acute allograft rejection, arthralgias, and the development of antidonor antibodies. Likewise depression is prevalent. Improving well-being and overall survival necessitates proper titration of immunosuppressive medications and control of blood pressure, anemia, lipids, and glucose along with attention to treatment of depression.