Acute Kidney Injury (AKI) is strongly associated with adverse outcome and mortality independently of the cause of renal damage [1][2][3] . The mechanisms determining the deleterious systemic effects of AKI are poorly understood and specific interventions, including optimization of renal replacement therapy, had a marginal effect on AKI-associated mortality in clinical trials [4][5][6][7][8] . The kidney contributes to up to 40% of systemic glucose production by gluconeogenesis during fasting and stress conditions, mainly synthesized from lactate in the proximal tubule [9][10][11][12] , rendering this organ a major systemic lactate disposal 13 . Whether kidney gluconeogenesis is impaired during AKI and how this might influence systemic metabolism remains unknown. Here we demonstrate that glucose production and lactate clearance are impaired during human AKI using renal arteriovenous catheterization in patients. Using single cell transcriptomics in mice and RNA sequencing in human biopsies, we show that glycolytic and gluconeogenetic pathways are modified during AKI in the proximal tubule specifically, explaining the metabolic alterations. We further demonstrate that impaired renal gluconeogenesis and lactate clearance during AKI are major determinants of systemic glucose and lactate levels in critically ill patients. Most importantly, altered glucose metabolism in AKI emerged as a major determinant of AKIassociated mortality. Thiamine supplementation restored renal glucose metabolism and substantially reduced AKI-associated mortality in intensive care patients. This study highlights an unappreciated systemic role of renal glucose and lactate metabolism in stress conditions, delineates general mechanisms explaining AKI-associated mortality and introduces a potential therapeutic intervention for a highly prevalent clinical condition with limited therapeutic options.To study the impact of AKI on renal glucose and lactate metabolism, we performed renal vein catheterization in patients undergoing cardiac surgery with cardiopulmonary bypass and experiencing (n=18) or not (n=87) post-operative AKI (Supplementary Table 1). We found a switch from net renal lactate uptake to net renal lactate release in patients experiencing AKI (-0.01±0.03 mmol/min to 0.02±0.02 mmol/min, p<0.001). Moreover, AKI patients showed a decrease in the renal net glucose release (0.06±0.07 mmol/min to 0.01±0.04 mmol/min, p=0.016) compared to the control group (Fig. 1 a,b). This suggested a simultaneous reduction of gluconeogenesis and activation of glycolysis in the kidney in response to AKI. Glycosuria was unlikely to be involved since all patients had arterial glucose levels below the glycosuria threshold (5.4 ± 0.94 mmol/L). To further characterize this process, we compared kidney allograft biopsies obtained during transplantation shortly (49±16 minutes) after

Background Nicotinamide adenine dinucleotide (NAD+) is a ubiquitous coenzyme involved in electron transport and a co-substrate for sirtuin function. NAD+ deficiency has been demonstrated in the context of acute kidney injury (AKI). Methods We studied the expression of key NAD+ biosynthesis enzymes in kidney biopsies from human allograft patients and patients with chronic kidney disease (CKD) at different stages. We used ischaemia–reperfusion injury (IRI) and cisplatin injection to model AKI, urinary tract obstruction [unilateral ureteral obstruction (UUO)] and tubulointerstitial fibrosis induced by proteinuria to investigate CKD in mice. We assessed the effect of nicotinamide riboside (NR) supplementation on AKI and CKD in animal models. Results RNA sequencing analysis of human kidney allograft biopsies during the reperfusion phase showed that the NAD+  de novo synthesis is impaired in the immediate post-transplantation period, whereas the salvage pathway is stimulated. This decrease in de novo NAD+ synthesis was confirmed in two mouse models of IRI where NR supplementation prevented plasma urea and creatinine elevation and tubular injury. In human biopsies from CKD patients, the NAD+  de novo synthesis pathway was impaired according to CKD stage, with better preservation of the salvage pathway. Similar alterations in gene expression were observed in mice with UUO or chronic proteinuric glomerular disease. NR supplementation did not prevent CKD progression, in contrast to its efficacy in AKI. Conclusion Impairment of NAD+ synthesis is a hallmark of AKI and CKD. NR supplementation is beneficial in ischaemic AKI but not in CKD models.

Hypertension-related, calcium-regulated gene (HCaRG/COMMD5) is highly expressed in renal proximal tubules, where it contributes to the control of cell proliferation and differentiation. HCaRG accelerates tubular repair by facilitating re-differentiation of injured proximal tubular epithelial cells, thus improving mouse survival after acute kidney injury. Sustained hyper-proliferation and de-differentiation are important hallmarks of tumor progression. Here, we demonstrate that cancer cells overexpressing HCaRG maintain a more differentiated phenotype, while several of them undergo autophagic cell death. Its overexpression in mouse renal cell carcinomas led to smaller tumor size with less tumor vascularization in a homograft tumor model. Mechanistically, HCaRG promotes de-phosphorylation of the proto-oncogene erythroblastosis oncogene B (ErbB)2/HER2 and epigenetic gene silencing of epidermal growth factor receptor and ErbB3 via promoter methylation. Extracellular signal-regulated kinase, AKT and mammalian target of rapamycin which mediate ErbB-dowstream signaling pathways are inactivated by HCaRG expression. In addition, HCaRG is underexpressed in human renal cell carcinomas and more expressed in normal tissue adjacent to renal cell carcinomas of patients with favorable prognosis. Taken together, our data suggest a role for HCaRG in the inhibition of tumor progression as a natural inhibitor of the ErbB signals in cancer and as a potential prognostic marker for renal cell carcinomas.

OBJECTIVES: Sepsis is a common condition in the ICU. Despite much research, its prognosis remains poor. In 2017, a retrospective before/after study reported promising results using a combination of thiamine, ascorbic acid, and hydrocortisone called “metabolic resuscitation cocktail” and several randomized controlled trials assessing its effectiveness were performed. DESIGN: We conducted a systematic review and meta-analysis of randomized controlled trials in septic ICU patients to assess the effects of this combination therapy. SETTING: PubMed, Embase, and the Cochrane library databases were searched from inception to March of 2021. Data were extracted independently by two authors. The main outcome was the change in Sequential Organ Failure Assessment score within 72 hours. Secondary outcomes included renal composite endpoints (acute kidney injury) Kidney Disease - Improving Global Outcome organization stage 3 or need for renal replacement therapy, vasopressor duration, and 28-day mortality. SUBJECTS: We included randomized controlled trials with patients admitted to the ICU with sepsis or septic shock. INTERVENTION: The trials compared a combination of thiamine, ascorbic acid, and hydrocortisone to standard care or placebo in patients admitted to ICU with sepsis or septic shock. MEASUREMENTS AND MAIN RESULTS: We included eight randomized controlled trials (n = 1,335 patients). Within 72 hours, the median of mean improvement was –1.8 and –3.2 in the control and intervention groups, respectively (eight randomized controlled trials, n = 1,253 patients); weighted mean difference –0.82 (95% CI, –1.15 to –0.48). Data were homogeneous and the funnel plot did not suggest any publication bias. Duration of vasopressor requirement was significantly reduced in the intervention group (six randomized controlled trials). There was no evidence of a difference regarding the ICU mortality and the renal composite outcome (acute kidney injury KDIGO 3 or need for renal replacement therapy, seven randomized controlled trials). CONCLUSIONS: Metabolic resuscitation cocktail administrated in ICU septic patients improves change in Sequential Organ Failure Assessment score within 72 hours. However, this improvement is modest and its clinical relevance is questionable. The impact on renal failure and mortality remains unclear.