Aguascalientes: one of the hottest chronic kidney disease (CKD) hotspots in Mexico and a CKD of unknown aetiology mystery to be solved

In a recent issue of Clinical Kidney Journal (CKJ), Gutierrez-Peña et al. reported a high incidence and prevalence of advanced chronic kidney disease (CKD) in Aguascalientes, Mexico. This contradicts Global Burden of Disease estimates, which should be updated. A key component of this high burden of CKD relates to young people ages 20-40 years in whom the cause of CKD was unknown [CKD of unknown aetiology (CKDu)]. The incidence of kidney replacement therapy in this age group in Aguascalientes is among the highest in the world, second only to Taiwan. However, high-altitude Aguascalientes, with a year-round average temperature of 19°C, does not fit the geography of other CKDu hotspots. Furthermore, kidney biopsies in young people showed a high prevalence of focal segmental glomerulosclerosis. Potential causes of CKDu in Aguascalientes include the genetic background (no evidence, although podocytopathy genes should be explored) and environmental factors. The highest prevalence of CKD was found in Calvillo, known for guava farming. Thus guava itself, known to contain bioactive, potentially nephrotoxic molecules and pesticides, should be explored. Additionally, there are reports of water sources in Aguascalientes contaminated with heavy metals and/or pesticides. These include fluoride (increased levels found in Calvillo drinking water) as well as naturally occurring arsenic, among others. Fluoride may accumulate in bone and cause kidney disease years later, and maternal exposure to excess fluoride may cause kidney disease in offspring. We propose a research agenda to clarify the cause of CKDu in Aguascalientes that should involve international funders. The need for urgent action to identify and stem the cause of the high incidence of CKD extends to other CKD hotspots in Mexico, including Tierra Blanca in Veracruz and Poncitlan in Jalisco.

The unaccomplished mission of reducing mortality in patients on kidney replacement therapy

Six years ago, a comprehensive review by the EURECA-m working group of the ERA-EDTA thoroughly addressed the drivers of mortality in patients with end-stage kidney disease. Not unexpectedly, the key global driver of early death in these patients was the lack of access to kidney replacement therapy. However, and contrary to the expectations of non-nephrologists, mortality was still high when kidney replacement therapy was provided. This was due to excess cardiovascular and non-cardiovascular mortality, and the need to further characterize correctable risk factors and eventually test the impact of correcting them was emphasized. In this issue of ckj, seven reports address risk factors for death in non-dialysis chronic kidney disease (CKD), dialysis and kidney transplant patients. They characterize irreversible (e.g. sex; age; genetic variants of the KL gene encoding the anti-ageing protein Klotho) and reversible (obesity; mineral and bone disorder parameters; anti-depressant drugs, especially those that increase the QT; amputation; public health investments) factors associated with mortality of CKD patients on or off kidney replacement therapy.

SGLT2 inhibitors for non-diabetic kidney disease: drugs to treat CKD that also improve glycaemia

Sodium-glucose co-transporter-2 (SGLT2) inhibitors decreased cardiovascular (CV) events and improved renal outcomes in CV safety studies in type 2 diabetes melitus (T2DM) patients at high CV risk. Canagliflozin also improved kidney outcomes in diabetic kidney disease in the Canagliflozin and Renal Events in Diabetes and Nephropathy Clinical Evaluationtrial. More recently, the Dapagliflozin and Prevention of Adverse Outcomes in Heart Failure (DAPA-HF) trial showed that dapagliflozin improved CV outcomes in patients with HF with or without diabetes. Protection from HF in non-diabetics was confirmed for empagliflozin in the EMPagliflozin outcomE tRial in Patients With chrOnic heaRt Failure With Reduced Ejection Fraction (EMPEROR-Reduced) trial. A meta-analysis of DAPA-HF and EMPEROR-Reduced confirmed reductions in all-cause and CV death and the combined risk of CV death or worsening HF, as well as in the composite renal endpoint {hazard ratio [HR] 0.62 [95% confidence interval (CI) 0.43-0.90]} without differences based on the presence of diabetes or baseline estimated glomerular filtration rate (eGFR). Moreover, the Study to Evaluate the Effect of Dapagliflozin on Renal Outcomes and Cardiovascular Mortality in Patients With Chronic Kidney Disease (DAPA-CKD) showed that dapagliflozin as an add-on over renin-angiotensin system blockade in patients with chronic kidney disease (CKD; with or without T2DM) reduced the HR for the primary endpoint (time to the first occurrence of ≥50% eGFR decline, end-stage kidney disease or renal or CV death) to 0.61 (95% CI 0.51-0.72) and for the secondary endpoints of worsening renal function or death from kidney failure [HR 0.56 (95% CI 0.45-0.68)], hospitalization for HF or CV death [HR 0.71 (95% CI 0.55-0.92)] and all-cause mortality [HR 0.69 (95% CI 0.53-0.88)]. These beneficial effects were consistent in patients with and without T2DM. In conclusion, SGLT2 inhibitors offer CV and kidney protection in both diabetic and non-diabetic CKD and, additionally, improve glycaemic control in T2DM, making them first-line therapy for CKD independent from diabetic status.

Pelacarsen for lowering lipoprotein(a): implications for patients with chronic kidney disease

Chronic kidney disease (CKD) patients are at an increased risk of cardiovascular disease (CVD) and statins may not be protective in advanced CKD. The reasons for the limited efficacy of statins in advanced CKD are unclear, but statins may increase plasma levels of the highly atherogenic molecule lipoprotein(a), also termed Lp(a), as well as PCSK9 (protein convertase subtilisin/kexin type 9) levels. Lp(a) has also been linked to calcific aortic stenosis, which is common in CKD. Moreover, circulating Lp(a) levels increase in nephrotic syndrome with declining renal function and are highest in patients on peritoneal dialysis. Thus, the recent publication of the Phase 2 randomized controlled trial of pelacarsen [also termed AKCEA-APO(a)-LRx and TQJ230], a hepatocyte-directed antisense oligonucleotide targeting the LPA gene messenger RNA, in persons with CVD should be good news for nephrologists. Pelacarsen safely and dose-dependently decreased Lp(a) levels by 35-80% and a Phase 3 trial [Lp(a)HORIZON, NCT04023552] is planned to run from 2020 to 2024. Unfortunately, patients with estimated glomerular filtration rate <60 mL/min or urinary albumin:creatinine ratio >100 mg/g were excluded from Phase 2 trials and those with 'significant kidney disease' will be excluded from the Phase 3 trial. Optimized exclusion criteria for Lp(a)HORIZON would provide insights into the role of Lp(a) in CVD in CKD patients.

Optimizing the timing of nephrology referral for patients with diabetic kidney disease

Age-standardized rates of diabetes mellitus (DM)-related complications, such as acute myocardial infarction, stroke or amputations, have decreased in recent years, but this was not associated with a clear reduction of the incidence of advanced chronic kidney disease (CKD) requiring renal replacement therapy. The early detection of diabetic kidney disease (DKD) is a key to reduce complications, morbidity and mortality. Consensus documents and clinical practice guidelines recommend referral of DM patients to nephrology when the estimated glomerular filtration rate falls below 30 mL/min/1.73 m² or when albuminuria exceeds 300 mg/g urinary creatinine. Conceptually, it strikes as odd that patients with CKD are referred to the specialist caring for the prevention and treatment of CKD only when >70% of the functioning kidney mass has been lost. The increasing global health burden of CKD, driven in large part by DKD, the suboptimal impact of routine care on DKD outcomes as compared with other DM complications, the realization that successful therapy of CKD requires early diagnosis and intervention, the advances in earlier diagnosis of kidney injury and the recent availability of antidiabetic drugs with a renal mechanism of action and lack of hypoglycaemia risk, which additionally are cardio- and nephroprotective, all point towards a paradigm shift in the care for DM patients in which they should be referred earlier to nephrology as part of a coordinated and integrated care approach.

Megalin/lipoprotein receptor-related protein 2 autoimmunity and kidney disease

In this issue of Clinical Kidney Journal, Gamayo et al. describe two cases of anti-low-density lipoprotein receptor-related protein 2 (LRP2) nephropathy. This is a recently described entity that has features of both tubulointerstitial disease and segmental membranous nephropathy. The originality of the present report consists of the association of a disease thought to be rare (only 13 in prior described patients, 11 in the past year) with B-cell lymphoproliferative disease. Together with the finding of a third case among 224 elderly patients studied, this raises the issue of the underdiagnoses of LRP2 nephropathy, on top of the potential association to B-cell malignancy. We now put these findings in context within the wider frame of autoimmunity against megalin/LRP2 and related antigens such as Fx1A and CD69.

Kidney disease and electrolytes in COVID-19: more than meets the eye

COVID-19 is a global pandemic fuelled in some countries by government actions. The current issue of Clinical Kidney Journal presents 15 articles on COVID-19 and kidney disease from three continents, providing a global perspective of the impact of severe acute respiratory syndrome coronavirus 2 on electrolytes and different kidney compartments (glomeruli, tubules and vascular compartments) and presenting clinically as a syndrome of inappropriate antidiuretic hormone secretion, acute kidney injury, acute kidney disease, collapsing glomerulopathy and thrombotic microangiopathy, among others, in the context of a brand-new cardiorenal syndrome. Kidney injury may need acute dialysis that may overwhelm haemodialysis (HD) and haemofiltration capabilities. In this regard, acute peritoneal dialysis (PD) may be lifesaving. Additionally, pre-existent chronic kidney disease increases the risk of more severe COVID-19 complications. The impact of COVID-19 on PD and HD patients is also discussed, with emphasis on preventive measures. Finally, current therapeutic approaches and potential future therapeutic approaches undergoing clinical trials, such as complement targeting by eculizumab, are also presented.

Klotho, the elusive kidney-derived anti-ageing factor

Chronic kidney disease (CKD) is one of the fastest growing causes of death worldwide. Only early diagnosis will allow prevention of both CKD progression and the negative impact of CKD on all-cause and cardiovascular mortality. Klotho is a protein produced by the kidneys that has anti-ageing and phosphaturic properties, preventing excess positive phosphate balance. There is evidence that Klotho downregulation is one of the earliest consequences of kidney injury. Thus the development of reliable assays to monitor Klotho levels may allow an early diagnosis of CKD and monitoring the impact of therapies aimed at preserving Klotho expression or at preventing CKD progression. However, the performance of Klotho assays has been suboptimal so far. In this issue of Clinical Kidney Journal, Neyra et al. explore methods to improve the reliability of Klotho assays.