Tissue metabolic profiling shows that saccharopine accumulates during renal ischemic-reperfusion injury, while kynurenine and itaconate accumulate in renal allograft rejection

Gut Microbiota Combined with Metabolomics Reveal the Mechanisms of Sika Deer Antler Protein on Cisplatin-Induced Hepatorenal Injury in Mice

Cisplatin is a widely used antineoplastic drug, though its adverse effects, particularly its hepatorenal toxicity, limit its long-term application. Sika deer antler is a valuable traditional Chinese medicine (TCM) documented to possess the capacity for tonifying the kidney and regulating the liver, of which the sika deer antler protein is an important active ingredient. In this study, two protein fractions, SVPr1 and SVPr2, of sika deer antler were purified and administered to mice treated with cisplatin, and serum metabolome and fecal microbiota were measured using ultrahigh-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) and 16S rRNA gene sequencing. SVPr1 and SVPr2 significantly ameliorated cisplatin-induced liver and kidney injury and reduced mitochondrial dysfunction, oxidative stress, inflammatory response, and apoptosis. In addition, SVPr1 and SVPr2 impacted the gut microbiota structure of mice, significantly increasing the relative abundances of Lactobacillus, which deserves to be scrutinized. Moreover, SVPr1 and SVPr2 antagonism of cisplatin-induced hepatorenal injury may be related to the regulation of lysine degradation, tryptophan metabolism, and riboflavin metabolism pathways, significantly altering the levels of L-saccharopine, L-lysine, L-kynurenine, 3-methylindole, xanthurenic acid, riboflavin, and D-ribulose-5-phosphate. A correlation between the differential metabolites and Lactobacillus was identified. These findings increased the knowledge of the gut microbiota-metabolites axis mediated by SVPr1 and SVPr2, and may be able to contribute to the development of new therapeutic strategies for the simultaneous prevention and treatment of liver and kidney injury from cisplatin treatment.

Preclinical models versus clinical renal ischemia reperfusion injury: A systematic review based on metabolic signatures

Despite decennia of research and numerous successful interventions in the preclinical setting, renal ischemia reperfusion (IR) injury remains a major problem in clinical practice, pointing toward a translational gap. Recently, two clinical studies on renal IR injury (manifested either as acute kidney injury or as delayed graft function) identified metabolic derailment as a key driver of renal IR injury. It was reasoned that these unambiguous metabolic findings enable direct alignment of clinical with preclinical data, thereby providing the opportunity to elaborate potential translational hurdles between preclinical research and the clinical context. A systematic review of studies that reported metabolic data in the context of renal IR was performed according to the PRISMA guidelines. The search (December 2020) identified 35 heterogeneous preclinical studies. The applied methodologies were compared, and metabolic outcomes were semi-quantified and aligned with the clinical data. This review identifies profound methodological challenges, such as the definition of IR injury, the follow-up time, and sampling techniques, as well as shortcomings in the reported metabolic information. In light of these findings, recommendations are provided in order to improve the translatability of preclinical models of renal IR injury.

A Review of Current and Emerging Trends in Donor Graft-Quality Assessment Techniques

The number of patients placed on kidney transplant waiting lists is rapidly increasing, resulting in a growing gap between organ demand and the availability of kidneys for transplantation. This organ shortage has forced medical professionals to utilize marginal kidneys from expanded criteria donors (ECD) to broaden the donor pool and shorten wait times for patients with end-stage renal disease. However, recipients of ECD kidney grafts tend to have worse outcomes compared to those receiving organs from standard criteria donors (SCD), specifically increased risks of delayed graft function (DGF) and primary nonfunction incidence. Thus, representative methods for graft-quality assessment are strongly needed, especially for ECDs. Currently, graft-quality evaluation is limited to interpreting the donor’s recent laboratory tests, clinical risk scores, the visual evaluation of the organ, and, in some cases, a biopsy and perfusion parameters. The last few years have seen the emergence of many new technologies designed to examine organ function, including new imaging techniques, transcriptomics, genomics, proteomics, metabolomics, lipidomics, and new solutions in organ perfusion, which has enabled a deeper understanding of the complex mechanisms associated with ischemia-reperfusion injury (IRI), inflammatory process, and graft rejection. This review summarizes and assesses the strengths and weaknesses of current conventional diagnostic methods and a wide range of new potential strategies (from the last five years) with respect to donor graft-quality assessment, the identification of IRI, perfusion control, and the prediction of DGF.

Itaconate as an inflammatory mediator and therapeutic target in cardiovascular medicine

Inflammation is a critical component of cardiovascular disease (CVD), encompassing coronary artery disease (CAD), cerebrovascular events and heart failure and is the leading cause of mortality worldwide. In recent years, metabolism has been placed centrally in the governance of the immune response. Termed immunometabolism, immune cells adapt cellular metabolic pathways to meet demands of activation and thus function. This rewiring influences not only the bioenergetics of the cell but altered metabolites act as signalling molecules to regulate cellular response. In this review, we focus on the TCA cycle derivative, itaconate, as one such metabolite with promising immunomodulatory and therapeutic potential in inflammatory cardiovascular disease.

Tackling Chronic Kidney Transplant Rejection: Challenges and Promises

Despite advances in post-transplant management, the long-term survival rate of kidney grafts and patients has not improved as approximately forty percent of transplants fails within ten years after transplantation. Both immunologic and non-immunologic factors contribute to late allograft loss. Chronic kidney transplant rejection (CKTR) is often clinically silent yet progressive allogeneic immune process that leads to cumulative graft injury, deterioration of graft function. Chronic active T cell mediated rejection (TCMR) and chronic active antibody-mediated rejection (ABMR) are classified as two principal subtypes of CKTR. While significant improvements have been made towards a better understanding of cellular and molecular mechanisms and diagnostic classifications of CKTR, lack of early detection, differential diagnosis and effective therapies continue to pose major challenges for long-term management. Recent development of high throughput cellular and molecular biotechnologies has allowed rapid development of new biomarkers associated with chronic renal injury, which not only provide insight into pathogenesis of chronic rejection but also allow for early detection. In parallel, several novel therapeutic strategies have emerged which may hold great promise for improvement of long-term graft and patient survival. With a brief overview of current understanding of pathogenesis, standard diagnosis and challenges in the context of CKTR, this mini-review aims to provide updates and insights into the latest development of promising novel biomarkers for diagnosis and novel therapeutic interventions to prevent and treat CKTR.

Tryptophan Metabolism via Kynurenine Pathway: Role in Solid Organ Transplantation

Solid organ transplantation is a gold standard treatment for patients suffering from an end-stage organ disease. Patient and graft survival have vastly improved during the last couple of decades; however, the field of transplantation still encounters several unique challenges, such as a shortage of transplantable organs and increasing pool of extended criteria donor (ECD) organs, which are extremely prone to ischemia-reperfusion injury (IRI), risk of graft rejection and challenges in immune regulation. Moreover, accurate and specific biomarkers, which can timely predict allograft dysfunction and/or rejection, are lacking. The essential amino acid tryptophan and, especially, its metabolites via the kynurenine pathway has been widely studied as a contributor and a therapeutic target in various diseases, such as neuropsychiatric, autoimmune disorders, allergies, infections and malignancies. The tryptophan-kynurenine pathway has also gained interest in solid organ transplantation and a variety of experimental studies investigating its role both in IRI and immune regulation after allograft implantation was first published. In this review, the current evidence regarding the role of tryptophan and its metabolites in solid organ transplantation is presented, giving insights into molecular mechanisms and into therapeutic and diagnostic/prognostic possibilities.