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Caloric restriction (CR)-mediated organ protection has been shown to be extremely efficient in rodent models of acute kidney injury (AKI). Limited understanding of the underlying mechanisms paired with a risk of malnourishment and feasibility problems has hindered the translation of this immense potential to the patient setting. In this mini-review, the current mechanistic concepts of CR-mediated stress-resistance as potential key targets for renal protection in AKI will be highlighted.

Background Frequent outbreaks around the globe and endemic appearance in different parts of the world emphasize the substantial risk of hantavirus diseases. Increasing incidence rates, trends of changing distribution of hantavirus species and new insights into clinical courses of hantavirus diseases call for multinational surveillance. Furthermore, evidence-based guidelines for the management of hantavirus diseases and scoring systems, which allow stratification of patients into risk categories, are lacking. Methods Hantavirus registry (HantaReg) is a novel registry platform facilitating multinational research of hantavirus-caused diseases, such as haemorrhagic fever with renal syndrome (HFRS) and hantavirus cardiopulmonary syndrome (HCPS). HantaReg provides an electronic case report form and uses the General Data Protection Regulation compliant platform clinicalsurveys.net, which can be accessed from any internet browser in the world. Having a modular structure, the registry platform is designed to display or hide questions and items according to the documented case (e.g. patient with HFRS versus HCPS) to facilitate fast, but standardized, data entry. Information categories documented in HantaReg are demographics, pre-existing diseases, clinical presentation, diagnostic and therapeutic approaches, as well as outcome. Conclusions HantaReg is a novel, ready-to-use platform for clinical and epidemiological studies on hantavirus diseases and facilitates the documentation of the disease course associated with hantavirus infections. HantaReg is expected to promote international collaboration and contributes to improving patient care through the analysis of diagnostic and treatment pathways for hantavirus diseases, providing evidence for robust treatment recommendations. Moreover, HantaReg enables the development of prognosis-indicating scoring systems for patients with hantavirus disease.

Caloric Restriction (CR) extends lifespan and augments cellular stress-resistance from yeast to primates, making CR an attractive strategy for organ protection in the clinic. Translation of CR to patients is complex, due to problems regarding adherence, feasibility and safety concerns in frail patients. Novel tailored dietary regimens, which modulate the dietary composition of macro- and micronutrients rather than reducing calorie intake promise similar protective effects and increased translatability. However, a direct head-to-head comparison to identify the most potent approach for organ protection as well as overlapping metabolic consequences has not been performed. We systematically analyzed six dietary preconditioning protocols - fasting mimicking diet (FMD), ketogenic diet (KD), dietary restriction of branched chained amino acids (BCAA), two dietary regimens restricting sulfur-containing amino acids (SR80/100) and CR - in a rodent model of renal ischemia-reperfusion injury (IRI) to quantify diet-induced resilience in kidneys. Of the administered diets, FMD, SR80/100 and CR efficiently protect from kidney damage after IRI. Interestingly, these approaches show overlapping changes in oxidative and hydrogen sulfide (H2S)-dependent cysteine catabolism as a potential common mechanism of organ protection.

Caloric Restriction (CR) extends lifespan and augments cellular stress-resistance from yeast to primates, making CR an attractive strategy for organ protection in the clinic. Translation of CR to patients is complex, due to problems regarding adherence, feasibility and safety concerns in frail patients. Novel tailored dietary regimens, which modulate the dietary composition of macro- and micronutrients rather than reducing calorie intake promise similar protective effects and increased translatability. However, a direct head-to-head comparison to identify the most potent approach for organ protection as well as overlapping metabolic consequences has not been performed. We systematically analyzed six dietary preconditioning protocols - fasting mimicking diet (FMD), ketogenic diet (KD), dietary restriction of branched chained amino acids (BCAA), two dietary regimens restricting sulfur-containing amino acids (SR80/100) and CR - in a rodent model of renal ischemia-reperfusion injury (IRI) to quantify diet-induced resilience in kidneys. Of the administered diets, FMD, SR80/100 and CR efficiently protect from kidney damage after IRI. Interestingly, these approaches show overlapping changes in oxidative and hydrogen sulfide (H2S)-dependent cysteine catabolism as a potential common mechanism of organ protection. Importantly, these metabolic changes can be recapitulated in patients preconditioned by a diet limiting sulfur-containing amino acids indicating conserved diet-induced mechanisms of stress-resistance that may ultimately lead to clinical application.

Acute kidney injury (AKI) is a frequent and critical complication in the clinical setting. In rodents AKI can be prevented effectively through caloric restriction (CR), which has also been shown to increase lifespan in many species. In Caenorhabditis elegans (C. elegans) longevity studies revealed that a marked CR-induced reduction of endocannabinoids may be a key mechanism. Thus, we hypothesized that regulation of endocannabinoids, in particular arachidonoyl ethanolamide (AEA), might also play a role in CR-mediated protection from renal ischemia-reperfusion injury (IRI) in mammals including humans. In male C57Bl6J mice, CR significantly reduced renal IRI and led to a significant decrease of AEA. Supplementation of AEA to near-normal serum concentrations by repetitive intraperitoneal administration in CR mice, however, did not abrogate the protective effect of CR. We also analyzed serum samples taken before and after CR from patients of three different pilot trials of dietary interventions. In contrast to mice and C. elegans, we detected an increase of AEA. We conclude that endocannabinoid levels in mice are modulated by CR, but CR-mediated renal protection does not depend on this effect. Moreover, our results indicate that modulation of endocannabinoids by CR in humans may differ fundamentally from the effects in animal models.

Diseases of the renal filtration unit—the glomerulus—are the most common cause of chronic kidney disease. Podocytes are the pivotal cell type for the function of this filter and focal-segmental glomerulosclerosis (FSGS) is a classic example of a podocytopathy leading to proteinuria and glomerular scarring. Currently, no targeted treatment of FSGS is available. This lack of therapeutic strategies is explained by a limited understanding of the defects in podocyte cell biology leading to FSGS. To date, most studies in the field have focused on protein-coding genes and their gene products. However, more than 80% of all transcripts produced by mammalian cells are actually non-coding. Here, long non-coding RNAs (lncRNAs) are a relatively novel class of transcripts and have not been systematically studied in FSGS to date. The appropriate tools to facilitate lncRNA research for the renal scientific community are urgently required due to a row of challenges compared to classical analysis pipelines optimized for coding RNA expression analysis. Here, we present the bioinformatic pipeline CALINCA as a solution for this problem. CALINCA automatically analyzes datasets from murine FSGS models and quantifies both annotated and de novo assembled lncRNAs. In addition, the tool provides in-depth information on podocyte specificity of these lncRNAs, as well as evolutionary conservation and expression in human datasets making this pipeline a crucial basis to lncRNA studies in FSGS.