Autosomic dominant polycystic kidney disease and metformin: Old knowledge and new insights on retarding progression of chronic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is the most common congenital kidney disorder, generally caused by mutations in the PKD1 and PKD2 genes, coding for polycystins 1 and 2. Its pathogenesis is accompanied by alterations of the cAMP, mTOR, MAPK/ERK, and JAK/STAT pathways. ADPKD is clinically characterized by the formation of many growing cysts with kidney enlargement and a progressive damage to the parenchyma, up to its complete loss of function, and the onset of end-stage renal disease (ESRD). The current aim of ADPKD therapy is the inhibition of cyst development and retardation of chronic kidney disease progression. Several drugs have been recently included as potential therapies for ADPKD including metformin, the drug of choice for the treatment of type 2 diabetes mellitus, according to its potential inhibitory effects on cystogenesis. In this review, we summarize preclinical and clinical evidence endorsing or rejecting metformin administration in ADPKD evolution and pathological mechanisms. We explored the biology of APDKD and the role of metformin in slowing down cystogenesis searching PubMed and Clinical Trials to identify relevant data from the database inception to December 2020. From our research analysis, evidence for metformin as emerging cure for ADPKD mainly arise from preclinical studies. In fact, clinical studies are still scanty and stronger evidence is awaited. Its effects are likely mediated by inhibition of the ERK pathway and increase of AMPK levels, which are both linked to ADPKD pathogenesis.

Membrane bioreactors as hybrid artificial pancreas: experimental evaluation

Results of cultured islet transplantation in the management of insulin-dependent diabetes are still unsatisfactory. The main problem preventing success is the swift and resolute host immune rejection. To obviate this we designed and experimented a model of bioartificial pancreas, made of polymeric hollow fibers, put into the blood circulation as an artero-venous bypass to immunoisolate endocrine tissue from leucocytes and immunoglobulins. We tested four different membrane bioreactors (BR1-4). BR1 and 2 had seven hollow fibers, the others more than 6,000 smaller fibers. In BR4 a connecting tube with a high-permeability membrane was inserted between the islet compartment and the bioreactor outlet to improve the ultrafiltration flow. In vitro, the islets inside the bioreactor perfused with glucose solutions (300 mg%) showed a rapid, high insulin secretory response, related to the glucose stimulation. The use of the outside connection allowed a twofold increase of insulin production.

Retarding Progression of Chronic Kidney Disease in Autosomal Dominant Polycystic Kidney Disease with Metformin and Other Therapies: An Update of New Insights

Autosomal dominant polycystic kidney disease (ADPKD) is the most frequent single-gene disorder leading to renal failure. Current therapies are aimed to treat renal and extrarenal complications of ADPKD, but improved knowledge of the pathophysiological mechanisms leading to the generation and growth of cysts has permitted the identification of new drug candidates for clinical trials. Among these, in this review, we will examine above all the role of metformin, hypothesized to be able to activate the AMP-activated protein kinase (AMPK) pathway and potentially modulate some mechanisms implicated in the onset and the growth of the cysts.

Hybrid artificial pancreas: islet transplantation inside membrane bioreactors

The use of pancreatic islet transplantation in membrane bioreactors put in vascular circuits aims at resetting the glucose homeostasis in diabetic or pancreatectomized patients, avoiding immune host rejection. Our experience was carried out at following stages: porcine pancreas explantation and enzymatic separation of endocrine tissue from exocrine fraction by collagenase; evaluation of islet functionality (culture tests); in vitro tests of the islets-bioreactor system, to assess the metabolic response to the glucose; in vivo evaluation to assay the haemodynamic behaviour. The trials showed a good metabolic bioreactor functionality and a decreasing incidence of coagulative problems.

Incidence of Acute Pulmonary Edema Before and After the Systematic Use of Ultrasound B-Lines

INTRODUCTION

Acute pulmonary edema (APE) due to fluid overload is considered the most feared complication in hemodialysis patients. Various diagnostic tests have been proposed to assess the fluid status in patients with end-stage kidney failure (ESKF); among these, lung ultrasound (measuring the number of B-lines) is emerging as a promising tool to identify pulmonary congestion in this patient population.

METHODS

We compared the incidence of APE before and after the implementation of lung ultrasound as a routine practice in our unit. The pre (from 1 January 2007 to 31 December 2008)- and post (from 1 January 2017 to 31 December 2018)-B-line implementation periods included 98 and 108 hemodialysis patients, respectively. By accurately reviewing their electronic medical records, all episodes of APE were collected. The 10-year interval between the two periods was specifically chosen to ensure no overlap between patients of the two cohorts whereas the single-center design was adopted to minimize the influence of center effect on the study results.

RESULTS

APE episodes occurred more frequently in patients from the pre-B-line implementation group (18/98, i.e., 18.4%) compared with those from the post B-line implementation group (6/108, i.e., 5.5%) (p = 0.004). An analysis based on repeated APE events showed that the incidence rate of APE was significantly higher during the pre-implementation period (2.0 APE episodes per 100 person-months, 95% CI: 1.4-2.7) than during the post-implementation period (0.3 APE episodes per 100 person-months, 95% CI: 0.1-0.7), with an incidence rate ratio (post- versus pre-) of 0.17 (95% CI: 0.07-0.40; p < 0.001). The odds of experiencing APE episodes were 74% lower (odds ratio: 0.26, 95% CI: 0.10-0.69) in patients from the post B-line implementation period compared with those from the pre-implementation period. Notably, adjusting for potential confounders did not affect the strength of this association, which remained statistically significant (p ≤ 0.030). Finally, dominance analysis indicated that the implementation of B-lines was the primary factor explaining the difference in APE episodes between the two periods, followed by dialysis duration and intra-dialysis weight gain.

CONCLUSIONS

The systematic use of lung ultrasound (a simple, easy-to-learn, rapid and non-invasive method, easily performed at the patient's bed) in everyday clinical practice was associated with a drastic reduction in episodes of APE in hemodialysis patients. Further observational and interventional studies are needed to confirm these results.

MO156THE ‘WITHIN-DAY’ VARIABILITY OF ALBUMINURIA INFLUENCES THE MONITORING OF NEPHROPROTECTIVE TREATMENT EFFECT

Background and Aims

Measurement of urine proteins, mainly through the 24-hour excretion or the albumin-to-creatinine ratio (ACR) has become crucial in current clinical practice in Nephrology. Besides being a biomarker of injury, albuminuria also exerts direct pro-inflammatory and pro-fibrotic effects on renal tubules. Hence, a large number of intervention studies have been aimed at lowering albuminuria levels in patients with Chronic Kidney Disease (CKD). However, albuminuria is a measure characterized by a random variability that has been evaluated in several mechanistic and experimental studies and may be influenced by several factors, such as posture, exercise and dietary factors. The aim of the present study was to evaluate the within-day variability, specifically in a cohort of CKD outpatients who were on Renin-Angiotensin-Aldosterone-System inhibitors (RAASi) therapy.

Method

We enrolled consecutive CKD patients referred to the Nephrology Unit at Magna Graecia University Hospital of Catanzaro between January 1st and March 30th 2020. Inclusion criteria were: age &gt; 18 years, diagnosis of CKD from any cause, presence of albuminuria in the range 150-3500 mg/g at screening. Patients already treated with RAASi, patients with active malignancy/signs of glomerulonephritis requiring immunosuppressive therapies, were excluded. At screening visit, patients with increased albuminuria were started with an Angiotensin Converting Enzyme inhibitor (ACEi) or an Angiotensin II Receptor Blocker (ARB). A second ambulatory visit was scheduled 1 month after start of RAASi therapy. During this visit, patients were asked to stay in the Renal Unit for 12 hours. They collected urine void for ACR, protein-to-creatinine ratio (PCR) and urine creatinine (Ucreat) assessment at 8am,1pm and 6pm. For each patient, comparisons between ACR, PCR and Ucreat were assessed by Kruskal-Wallis test and Friedman post-hoc, using the Benjamini-Hochberg as adjustment method. Coefficients of variation (CV,standard deviation/mean) were also computed.

Results

Final analysis included 43 patients (46.5% of males). Mean age was 59.6±16.7 years and median eGFR 41 [21-74] mL/min/1.73m2. A high cardiovascular (CV) risk profile was testified by the prevalence of type 2 diabetes (30.2%) and previous CV disease (34.8%). When patient characteristics were compared across ACR categories (&lt;30, 30-300, &gt;300 mg/g), systolic blood pressure was increased (p=0.020) and mean age decreased from 68.0 to 54.8 years on average (p=0.038). ACR values collected were 189 [38-759], 252 [51-1685] and 229 [56-1185] mg/g at 8am, 1pm and 6pm, respectively, with a CV of 24.6% (95%CI 12.4-39.1). 8am ACR was significantly different from 1pm ACR (p&lt;0.001) and from 6pm ACR (p&lt;0.001). 1 pm ACR was significantly different from 6pm ACR (p=0.002). Median PCR were 335 [115-932], 429 [146-1811] and 447 [151-1465] mg/g respectively at 8am, 1pm and 6pm, with CV being 17.8% (95%CI 9.0-26.6). 8am PCR differed significantly from 1pm and 6pm PCR (p&lt;0.001 for both), while 1pm ACR was lower than 6pm ACR (p&lt;0.001). Ucreat was 66 [53-103], 63 [47-96] and 69 [50-90] mg/dL respectively at 8am, 1pm and 6pm with no significant variation trend. Individual within-day ACR and PCR trends are depicted in the Figure .

Conclusion

The present analysis showed a significant individual within-day variability of albuminuria, measured as both ACR and PCR, suggesting that another parameter, in addition to those already known, may be responsible for the day-by-day albuminuria variation. Moreover, the absence of variability in Ucreat, namely the denominator of the ACR/PCR formula, suggests that the true variation is likely dependent on the urine protein values. Thus, albuminuria reduction in response to RAASi treatment should be carefully evaluated by measuring ACR/PCR preferentially at a similar time of the day for each patient. This would allow to avoid under- or overestimation of the actual treatment effect.