Glutamine attenuates tubular cell apoptosis in acute kidney injury via inhibition of the c-Jun N-terminal kinase phosphorylation of 14-3-3*:

Glutaminolysis is a Potential Therapeutic Target for Kidney Diseases

Metabolic reprogramming contributes to the progression and prognosis of various kidney diseases. Glutamine is the most abundant free amino acid in the body and participates in more metabolic processes than other amino acids. Altered glutamine metabolism is a prominent feature in different kidney diseases. Glutaminolysis converts glutamine into the TCA cycle metabolite, alpha-ketoglutarate, via a cascade of enzymatic reactions. This metabolic pathway plays pivotal roles in inflammation, maladaptive repair, cell survival and proliferation, redox homeostasis, and immune regulation. Given the crucial role of glutaminolysis in bioenergetics and anaplerotic fluxes in kidney pathogenesis, studies on this cascade could provide a better understanding of kidney diseases, thus inspiring the development of potential methods for targeted therapy. Emerging evidence has shown that targeting glutaminolysis is a promising therapeutic strategy for ameliorating kidney disease. In this narrative review, equation including keywords related to glutamine, glutaminolysis and kidney are subjected to an exhaustive search on Pubmed database, we identified all relevant articles published before 1 April, 2024. Afterwards, we summarize the regulation of glutaminolysis in major kidney diseases and its underlying molecular mechanisms. Furthermore, we highlight therapeutic strategies targeting glutaminolysis and their potential clinical applications.

The Preventive Role of Glutamine Supplementation in Cardiac Surgery-Associated Kidney Injury from Experimental Research to Clinical Practice: A Narrative Review

Acute kidney injury represents a significant threat in cardiac surgery regarding complications and costs. Novel preventive approaches are needed, as the therapeutic modalities are still limited. As experimental studies have demonstrated, glutamine, a conditionally essential amino acid, might have a protective role in this setting. Moreover, the levels of glutamine after the cardiopulmonary bypass are significantly lower. In clinical practice, various trials have investigated the effects of glutamine supplementation on cardiac surgery with encouraging results. However, these studies are heterogeneous regarding the selection criteria, timing, dose, outcomes studied, and way of glutamine administration. This narrative review aims to present the potential role of glutamine in cardiac surgery-associated acute kidney injury prevention, starting from the experimental studies and guidelines to the clinical practice and future directions.

Bioinformatics analysis and experimental validation reveal the anti-ferroptosis effect of FZD7 in acute kidney injury

BACKGROUND

Ferroptosis plays an important role in acute kidney injury (AKI), but the specific regulatory mechanism of ferroptosis in AKI remains unclear. This study is expected to analyze ferroptosis-related genes (FRGs) in AKI and explore their underlying mechanisms.

RESULTS

A total of 479 differentially expressed genes (DEGs), including 196 up-regulated genes and 283 down-regulated genes were identified in the AKI chip GSE30718. 341 FRGs were obtained from the Genecard, OMIM and NCBI database. Totally 11 ferroptosis-related DEGs in AKI were found, in which 7 genes (CD44, TIGAR, RB1, LCN2, JUN, ARNTL, ACSL4) were up-regulated and 4 genes (FZD7, EP300, FOXC1, DLST) were down-regulated. Three core genes (FZD7, JUN, EP300) were obtained by PPI and KEGG analysis, among which the function of FZD7 in AKI is unclear. The WGCNA analysis found that FZD7 belongs to a module that was negatively correlated with AKI. Further basic experiments confirmed that FZD7 is down-regulated in mouse model of ischemia-reperfusion-AKI and cellular model of hypoxia-reoxygenation(H/R). In addition, knockdown of FZD7 could further aggravate the down-regulation of cell viability induced by H/R and Erastin, while overexpression of FZD7 can rescue its down-regulation to some extent. Furthermore, we verified that knockdown of FZD7 decreased the expression of GPX4 and overexpression of FZD7 increased the expression of GPX4, suggesting that FZD7 may inhibit ferroptosis by regulating the expression of GPX4 and plays a vital role in the onset and development of AKI.

CONCLUSIONS

This article revealed the anti-ferroptosis effect of FZD7 in acute kidney injury through bioinformatics analysis and experimental validation, suggesting that FZD7 is a promising target for AKI and provided more evidence about the vital role of ferroptosis in AKI.

Effect of Glutamine Administration After Cardiac Surgery on Kidney Damage in Patients at High Risk for Acute Kidney Injury: A Randomized Controlled Trial

BACKGROUND

Acute kidney injury (AKI) is a common complication after cardiac surgery and is associated with increased morbidity and mortality. However, no specific treatment options are available, emphasizing the need for preventive measures. The aim of this study was to clarify the effect of glutamine on [TIMP2]*[IGFBP7] levels at the end of the intervention period.

METHODS

In a randomized clinical, double-blind pilot study, 64 eligible cardiac surgery patients at high risk for AKI identified by high urinary [TIMP2]*[IGFBP7] were randomized, and body weight-adapted intravenous glutamine or saline-control was administered continuously for 12 hours postoperatively. The primary outcome was urinary [TIMP2]*[IGFBP7] at the end of the 12-hour study period. Secondary outcomes included kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) at 12 hours, overall AKI rates at 72 hours, free days through day 28 of mechanical ventilation and vasoactive medication, renal recovery at day 90, requirement of renal replacement therapy and mortality each at days 30, 60, and 90, length of intensive care unit (ICU) and hospital stay, and major adverse kidney events consisting of mortality, dialysis dependency, and persistent renal dysfunction (serum creatinine ≥2× compared to baseline value) at day 90 (major adverse kidney event; MAKE 90 ).

RESULTS

Sixty-four patients (mean age, 68.38 [standard deviation {SD} ± 10.48] years; 10 of 64 women) were enrolled and randomized. Patients received coronary artery bypass graft surgery (32/64), valve surgery (18/64), coronary artery bypass graft and valve surgery (6/64), or other procedures (8/64). Mean on-pump time was 68.38 (standard deviation ± 10.48) minutes. After glutamine administration, urinary [TIMP-2]*[IGFBP7] was significantly lower in the glutamine compared to the control group (primary end point, intervention: median, 0.18 [Q1, Q3; 0.09, 0.29], controls: median, 0.44 [Q1, Q3; 0.14, 0.79]; P = .01). In addition, [KIM-1] and [NGAL] were also significantly lower in the glutamine group. The overall AKI rate within 72 hours was not different among groups: (intervention 11/31 [35.5%] versus control 8/32 [25.0%]; P = .419; relative risk [RR], 0.86% [95% confidence interval {CI}, 0.62-1.20]). There were no differences regarding secondary end points.

CONCLUSIONS

Glutamine significantly decreased markers of kidney damage in cardiac surgery patients at high risk for AKI. Future trials have to be performed to investigate whether the administration of glutamine might be able to reduce the occurrence of AKI after cardiac surgery.

Heat Shock Protein 70 Is Involved in the Efficiency of Preconditioning with Cyclosporine A in Renal Ischemia Reperfusion Injury by Modulating Mitochondrial Functions

Cyclosporine A (CsA) preconditioning is known to target mitochondrial permeability transition pore and protect renal function after ischemia reperfusion (IR). The upregulation of heat-shock protein 70 (Hsp70) expression after CsA injection is thought to be associated with renal protection. The aim of this study was to test the effect of Hsp70 expression on kidney and mitochondria functions after IR. Mice underwent a right unilateral nephrectomy and 30 min of left renal artery clamping, performed after CsA injection and/or administration of the Hsp70 inhibitor. Histological score, plasma creatinine, mitochondrial calcium retention capacity, and oxidative phosphorylation were assessed after 24 h of reperfusion. In parallel, we used a model of hypoxia reoxygenation on HK2 cells to modulate Hsp70 expression using an SiRNA or a plasmid. We assessed cell death after 18 h of hypoxia and 4 h of reoxygenation. CsA significantly improved renal function, histological score, and mitochondrial functions compared to the ischemic group but the inhibition of Hsp70 repealed the protection afforded by CsA injection. In vitro, Hsp70 inhibition by SiRNA increased cell death. Conversely, Hsp70 overexpression protected cells from the hypoxic condition, as well as the CsA injection. We did not find a synergic association between Hsp70 expression and CsA use. We demonstrated Hsp70 could modulate mitochondrial functions to protect kidneys from IR. This pathway may be targeted by drugs to provide new therapeutics to improve renal function after IR.

Integrating Metabolomics and Network Pharmacology to Explore the Mechanism of Tongmai Yangxin Pills in Ameliorating Doxorubicin-Induced Cardiotoxicity

Doxorubicin (DOX) is a broad-spectrum chemotherapeutic drug used in clinical treatment of malignant tumors. It has a high anticancer activity but also high cardiotoxicity. The aim of this study was to explore the mechanism of Tongmai Yangxin pills (TMYXPs) in ameliorating DOX-induced cardiotoxicity through integrated metabolomics and network pharmacology. In this study, first, an ultrahigh-performance liquid chromatography-quadrupole-time-of-flight/mass spectrometry (UPLC-Q-TOF/MS) metabonomics strategy was established to obtain metabolite information and potential biomarkers were determined after data processing. Second, network pharmacological analysis was used to evaluate the active components, drug-disease targets, and key pathways of TMYXPs to alleviate DOX-induced cardiotoxicity. Targets from the network pharmacology analysis and metabolites from plasma metabolomics were jointly analyzed to select crucial metabolic pathways. Finally, the related proteins were verified by integrating the above results and the possible mechanism of TMYXPs to alleviate DOX-induced cardiotoxicity was studied. After metabolomics data processing, 17 different metabolites were screened, and it was found that TMYXPs played a role in myocardial protection mainly by affecting the tricarboxylic acid (TCA) cycle of myocardial cells. A total of 71 targets and 20 related pathways were screened out with network pharmacological analysis. Based on the combined analysis of 71 targets and different metabolites, TMYXPs probably played a role in myocardial protection through regulating upstream proteins of the insulin signaling pathway, MAPK signaling pathway, and p53 signaling pathway, as well as the regulation of metabolites related to energy metabolism. They then further affected the downstream Bax/Bcl-2-Cyt c-caspase-9 axis, inhibiting the myocardial cell apoptosis signaling pathway. The results of this study may contribute to the clinical application of TMYXPs in DOX-induced cardiotoxicity.

Protective effects of glutamine on lipopolysaccharide/D-galactosamine-induced fulminant hepatitis in mice

Fulminant hepatitis remains a critical health problem owing to its high mortality rate and the lack of effective therapies. An increasing number of studies have shown that glutamine supplementation provides protective benefits in inflammation-related disorders, but the pharmacological significance of glutamine in lipopolysaccharide (LPS)/D-galactosamine (D-Gal)-induced fulminant hepatitis remains unclear. In the present study, the potential effects of glutamine on LPS/D-Gal-induced fulminant hepatitis were investigated. Pretreatment with glutamine decreased plasma activities of alanine and aspartate aminotransferases, and ameliorated hepatic morphological abnormalities in LPS/D-Gal-exposed mice. Glutamine pretreatment also inhibited LPS/D-Gal-induced tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) production. In addition, glutamine pretreatment decreased the level of cleaved cysteinyl aspartate-specific proteinase 3 (caspase-3), suppressed the activities of caspase-3, caspase-8, and caspase-9, and reduced the number of cells positive for TdT-mediated dUTP nick-end labeling in LPS/D-Gal-challenged mice. Interestingly, post-treatment with glutamine also provided protective benefits against LPS/D-Gal-induced acute liver injury, although these effects were less robust than those of glutamine pre-treatment. Thus, glutamine may have potential value as a pharmacological intervention in fulminant hepatitis.

Glutamine prevents acute kidney injury by modulating oxidative stress and apoptosis in tubular epithelial cells

Acute kidney injury (AKI) represents a common complication in critically ill patients that is associated with increased morbidity and mortality. In a murine AKI model induced by ischemia/reperfusion injury (IRI), we show that glutamine significantly decreases kidney damage and improves kidney function. We demonstrate that glutamine causes transcriptomic and proteomic reprogramming in murine renal tubular epithelial cells (TECs), resulting in decreased epithelial apoptosis, decreased neutrophil recruitment, and improved mitochondrial functionality and respiration provoked by an ameliorated oxidative phosphorylation. We identify the proteins glutamine gamma glutamyltransferase 2 (Tgm2) and apoptosis signal-regulating kinase (Ask1) as the major targets of glutamine in apoptotic signaling. Furthermore, the direct modulation of the Tgm2-HSP70 signalosome and reduced Ask1 activation resulted in decreased JNK activation, leading to diminished mitochondrial intrinsic apoptosis in TECs. Glutamine administration attenuated kidney damage in vivo during AKI and TEC viability in vitro under inflammatory or hypoxic conditions.

Functional consequence of myeloid ferritin heavy chain on acute and chronic effects of rhabdomyolysis-induced kidney injury

Acute kidney injury (AKI) is a serious complication of rhabdomyolysis that significantly impacts survival. Myoglobin released from the damaged muscle accumulates in the kidney, causing heme iron-mediated oxidative stress, tubular cell death, and inflammation. In response to injury, myeloid cells, specifically neutrophils and macrophages, infiltrate the kidneys, and mediate response to injury. Ferritin, comprised of ferritin light chain and ferritin heavy chain (FtH), is vital for intracellular iron handling. Given the dominant role of macrophages and heme-iron burden in the pathogenesis of rhabdomyolysis, we studied the functional role of myeloid FtH in rhabdomyolysis-induced AKI and subsequent fibrosis. Using two models of rhabdomyolysis induced AKI, we found that during the acute phase, myeloid FtH deletion did not impact rhabdomyolysis-induced kidney injury, cell death or cell proliferation, suggesting that tubular heme burden is the dominant injury mechanism. We also determined that, while the kidney architecture was markedly improved after 28 days, tubular casts persisted in the kidneys, suggesting sustained damage or incomplete recovery. We further showed that rhabdomyolysis resulted in an abundance of disparate intra-renal immune cell populations, such that myeloid populations dominated during the acute phase and lymphoid populations dominated in the chronic phase. Fibrotic remodeling was induced in both genotypes at 7 days post-injury but continued to progress only in wild-type mice. This was accompanied by an increase in expression of pro-fibrogenic and immunomodulatory proteins, such as transforming growth factor-β, S100A8, and tumor necrosis factor-α. Taken together, we found that while the initial injury response to heme burden was similar, myeloid FtH deficiency was associated with lesser interstitial fibrosis. Future studies are warranted to determine whether this differential fibrotic remodeling will render these animals more susceptible to a second AKI insult or progress to chronic kidney disease at an accelerated pace.

Urinary metabolomics to develop predictors for pediatric acute kidney injury

BACKGROUND

Acute kidney injury (AKI) is characterized by an abrupt decline in glomerular filtration rate (GFR). We sought to identify separate early urinary metabolomic signatures at AKI onset (with-AKI) and prior to onset of functional impairment (pre-AKI).

METHODS

Pre-AKI (n=15), AKI (n=22), and respective controls (n=30) from two prospective PICU cohort studies provided urine samples which were analyzed by GC-MS and DI-MS mass spectrometry (193 metabolites). The cohort (n=58) was 8.7±6.4 years old and 66% male. AKI patients had longer PICU stays, higher PRISM scores, vasopressors requirement, and respiratory diagnosis and less commonly had trauma or post-operative diagnosis. Urine was collected within 2-3 days after admission and daily until day 5 or 14.

RESULTS

The metabolite classifiers for pre-AKI samples (1.5±1.1 days prior to AKI onset) had a cross-validated area under receiver operator curve (AUC)=0.93 (95%CI 0.85-1.0); with-AKI samples had an AUC=0.94 (95%CI 0.87-1.0). A parsimonious pre-AKI classifier with 13 metabolites was similarly robust (AUC=0.96, 95%CI 0.89-1.0). Both classifiers were similar and showed modest correlation of high-ranking metabolites (tau=0.47, p<0.001).

CONCLUSIONS

This exploratory study demonstrates the potential of a urine metabolite classifier to detect AKI-risk in pediatric populations earlier than the current standard of diagnosis with the need for external validation. A higher resolution version of the Graphical abstract is available as Supplementary information with inner reference to ESM for GA.

Fenofibrate reduces cisplatin-induced apoptosis by inhibiting the p53/Puma/Caspase-9 pathway and the MAPK/Caspase-8 pathway rather than by promoting autophagy in murine renal proximal tubular cells

The main lesion of cisplatin nephrotoxicity is damage to proximal tubular cells due to increased apoptosis via the mitochondrial and death receptor pathways, which may be alleviated by appropriate promotion of autophagy. Fenofibrate, a peroxisome proliferator-activated receptor-alpha (PPAR-α) activator, is recently reported to promote autophagy as well as protect against cisplatin nephrotoxicity, although the mechanisms were only partially analyzed. Here, the detailed mechanisms of these putative protective effects were investigated in a murine renal proximal tubular (mProx) cell line. Fenofibrate attenuated cisplatin-induced apoptosis of mProx cells based on flow cytometry. As for the mitochondrial apoptotic pathway, the reagent reduced cisplatin-stimulated caspase-3 activation by decreasing the phosphorylation of p53, JNK, and 14-3-3, cytosolic and mitochondrial Puma accumulation, cytochrome C release to the cytosol, and resulting cytosolic caspase-9 activation. Fenofibrate also decreased cisplatin-stimulated activation of caspases-8 by suppressing MAPK and NFkB pathways and reducing the gene expression of TNF-α, TL1A, and Fas, main mediators of the death receptor apoptotic pathway. Autophagy defined by p62 reduction and an increase in LC3 II/I was promoted by fenofibrate in mProx cells under starvation. Autophagy inhibition using 3-MA further increased basal and cisplatin-induced caspase-3 and -8 activation, but had no influence on the inhibitory effects of fenofibrate on caspase activation. In conclusion, our study suggests fenofibrate to be a candidate agent to mitigate cisplatin nephrotoxicity by inhibiting the mitochondrial and death apoptotic pathways rather than by promoting autophagy.

•

Fenofibrate reduced cisplatin-induced apoptosis in mProx cells.

•

Fenofibrate reduced caspase-3 activation by inhibiting p53/Puma/caspase-9 pathways.

•

Fenofibrate reduced caspase-8 activation by inhibiting MAPK/death receptor pathways.

•

Fenofibrate promoted autophagy in mProx cells under starvation conditions.

•

Autophagy inhibition, however, did not affect the protective effects.

Identification of biomarkers, immune infiltration landscape, and treatment targets of ischemia-reperfusion acute kidney injury at an early stage by bioinformatics methods

Background

Mechanisms underlying ischemia/reperfusion injury-acute kidney injury (IRI-AKI) are not fully elucidated. We conducted an integrative analysis of IRI-AKI by bioinformatics methods.

Methods

We screened gene expression profiles of the IRI-AKI at early phase from the Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) were identified and enrichment pathways were conducted based on gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) database, and Gene set enrichment analysis (GSEA). Immune cell infiltration analysis was performed to reveal the change of the microenvironment cell types. We constructed protein–protein interaction (PPI), and Cytoscape with plug-ins to find hub genes and modules. We performed robust rank aggregation (RRA) to combine DEGs and analyzed the target genes for miRNA/transcription factor (TF) and drug-gene interaction networks.

Results

A total of 239 and 384 DEGs were identified in GSE87024 and GSE34351 separately, with the 73 common DEGs. Enrichment analysis revealed that the significant pathways involve mitogen-activated protein kinase (MAPK) signaling, interleukin-17, and tumor necrosis factor (TNF) signaling pathway, etc. RRA analysis detected a total of 27 common DEGs. Immune cell infiltration analysis showed the plasma cells reduced and T cells increased in IRI-AKI. We identified JUN, ATF3, FOS, EGR1, HMOX1, DDIT3, JUNB, NFKBIZ, PPP1R15A, CXCL1, ATF4, and HSPA1B as hub genes. The target genes interacted with 23 miRNAs and 116 drugs or molecular compounds such as curcumin, staurosporine, and deferoxamine.

Conclusion

Our study first focused on the early IRI-AKI adopting RRA analysis to combine DEGs in different datasets. We identified significant biomarkers and crucial pathways involved in IRI-AKI and first construct the immune landscape and detected the potential therapeutic targets of the IRI-AKI by drug-gene network.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41065-022-00236-x.

Glutamine alleviates the renal dysfunction associated with gentamicin-induced acute kidney injury in Sprague-Dawley rats

Sepsis is a clinical condition caused by an uncontrolled response to an infection, leading to acute kidney injury (AKI) and an increased risk of mortality. Although life support and antibiotic therapy are available, the mortality rate remains high in patients with sepsis. The present study investigated the therapeutic effect of glutamine on gentamicin-induced acute kidney injury in Sprague-Dawley rats. We randomly grouped 24 male rats to the normal control, AKI (control), glutamine 50 mg/kg, and glutamine 500 mg/kg groups. The dose was administered orally for 14 consecutive days. Rats treated with glutamine 500 mg/kg showed changes in systolic blood pressure. Glutamine increased renal blood flow, creatinine clearance, and the levels of potassium, creatinine, blood urea nitrogen, and urine osmolality, while reducing the relative excretion of sodium, potassium, urinary sodium, and plasma blood urea nitrogen and creatinine levels. In our study, glutamine supplementation reduced gentamicin-induced oxidative stress and increased catalase, superoxide dismutase, glutathione peroxidase, and glutathione levels in AKI rats. In addition, glutamine supplementation attenuated the severity of pathological features in this model. Collectively, our results showed that gentamicin has therapeutic potential against gentamicin-induced AKI due to its ability to mitigate the effects of oxidative stress.

PPAR-δ activation reduces cisplatin-induced apoptosis via inhibiting p53/Bax/caspase-3 pathway without modulating autophagy in murine renal proximal tubular cells

BACKGROUND

Cisplatin-induced injury of renal proximal tubular cells results basically from increased apoptosis via mitochondrial damage, and is mitigated by appropriate enhancement of autophagy. Peroxisome proliferator-activated receptor-delta (PPAR-δ) reportedly protects against not only mitochondrial damages but also enhances autophagy. Thus, PPAR-δ may protect against cisplatin-induced kidney injury.

METHODS

We examined the protective effects of PPAR-δ activation on cisplatin-induced cellular injury and their detailed mechanisms in a murine renal proximal tubular (mProx) cell line using GW0742, an authentic PPAR-δ activator. Cisplatin-induced cell damages were evaluated by TUNEL assay and immunoblot analyses for p53, 14-3-3, Bax, Bcl2, cytochrome C, and activated caspases. Autophagy status was examined by immunoblot analyses for p62 and LC3.

RESULTS

GW0742 suppressed cisplatin-induced apoptosis of mProx cells by reducing the activation of caspase-3 via attenuating the phosphorylation of p53 and 14-3-3, mitochondrial Bax accumulation, cytochrome C release from mitochondria to the cytosol and ensuing cytosolic caspase-9 activation. In contrast, GW0742 did not diminish cisplatin-enhanced activation of caspases-8 or -12 as extrinsic or endothelium reticulum apoptotic pathways, respectively. The inhibitory effect of GW0742 on cisplatin-induced caspase-3 activation was significantly diminished by silencing of the PPAR-δ gene expression. GW0742 itself had no influence on starvation-stimulated or cisplatin-induced autophagy in mProx cells, suggesting that the protective effects were not mediated by autophagy modification.

CONCLUSION

Our results indicate that GW0742 may serve as a candidate agent to mitigate cisplatin nephrotoxicity via inhibiting the mitochondrial apoptotic pathway considerably depending on PPAR-δ, without modulating autophagy.

Identification of novel metabolomic biomarkers in an experimental model of septic acute kidney injury

The aim of this study is the identification of metabolomic biomarkers of sepsis and sepsis-induced acute kidney injury (AKI) in an experimental model. Pigs were anesthetized and monitored to measure mean arterial pressure (MAP), systemic blood flow (Q_T), mean pulmonary arterial pressure, renal artery blood flow (Q_RA), renal cortical blood flow (Q_RC), and urine output (UO). Sepsis was induced at t = 0 min by the administration of live Escherichia coli ( n = 6) or saline ( n = 8). At t = 300 min, animals were killed. Renal tissue, urine, and serum samples were analyzed by nuclear magnetic resonance (NMR) spectroscopy. Principal component analyses were performed on the processed NMR spectra to highlight kidney injury biomarkers. Sepsis was associated with decreased Q_T and MAP and decreased Q_RA, Q_RC, and UO. Creatinine serum concentration and neutrophil gelatinase-associated lipocalin (NGAL) serum and urine concentrations increased. NMR-based metabolomics analysis found metabolic differences between control and septic animals: 1) in kidney tissue, increased lactate and nicotinuric acid and decreased valine, aspartate, glucose, and threonine; 2) in urine, increased isovaleroglycine, aminoadipic acid, N-acetylglutamine, N-acetylaspartate, and ascorbic acid and decreased myoinositol and phenylacetylglycine; and 3) in serum, increased lactate, alanine, pyruvate, and glutamine and decreased valine, glucose, and betaine concentrations. The concentration of several metabolites altered in renal tissue and urine samples from septic animals showed a significant correlation with markers of AKI (i.e., creatinine and NGAL serum concentrations). NMR-based metabolomics is a potentially useful tool for biomarker identification of sepsis-induced AKI.

Glutathione Reduction of Patulin-Evoked Cytotoxicity in HEK293 Cells by the Prevention of Oxidative Damage and the Mitochondrial Apoptotic Pathway

Patulin (PAT) is a mycotoxin frequently detected in moldy fruits and fruit products. This study investigated the protective role of glutathione (GSH), an antioxidant agent, against PAT-induced cytotoxicity and its potential mechanisms in HEK293 cells. The obtained results showed that the addition of GSH significantly increased cell viability and decreased apoptosis induced by PAT. Additionally, GSH decreased intracellular ROS and mitochondrial ROS overproduction, suppressed the decline of the mitochondrial membrane potential, and maintained cellular ATP contents. GSH prevented the impairment of mitochondrial oxidative-phosphorylation system and, especially, enhanced the mRNA and protein levels of electron-transport-chain complex III (UQCRC2) and complex V (ATP5, ATP6 and ATP8). Furthermore, GSH increased endogenous GSH contents; enhanced the antioxidant-enzyme activities of SOD, CAT, GR, and GPx; and modulated oxidative damage. These results suggest that GSH reduces PAT-induced cytotoxicity via inhibition of oxidative damage and the mitochondrial apoptotic pathway in HEK293 cells.

Effect of parenteral glutamine supplementation combined with enteral nutrition on Hsp90 expression and Peyer's patch apoptosis in severely burned rats

OBJECTIVES

The aim of this study was to investigate the effects of parenteral glutamine (GLN) supplementation combined with enteral nutrition (EN) on heat shock protein (Hsp) 90 expression and Peyer's patch (PP) apoptosis in severely burned rats.

METHODS

Male Sprague-Dawley (SD) rats were randomly assigned to four groups: Sham burn + EN + GLN-free amino acid (AA; n = 10), sham burn + EN + GLN (n = 10), burn + EN + AA (n = 10), and burn + EN + GLN (n = 10). Two hours after a 30% total body surface area (TBSA), full-thickness scald burn injury on the back, burned rats in two of the experimental groups (burn + EN + AA and burn + EN + GLN groups) were fed with a conventional EN solution by oral gavage for 7 d. Simultaneously, rats in the burn + EN + GLN group were given 0.35 g GLN/kg body weight/d once via a tail vein injection for 7 d and rats in the burn + EN + AA group were administered isocaloric/isonitrogenous GLN-free amino acid solution (Tyrosine) for comparison. Rats in two sham burn control groups (sham burn + EN + AA and sham burn + EN + GLN groups) were treated in the same manner except for the burn injury. All rats in the four groups were given 175 kcal/kg body wt/d. There was isonitrogenous, isovolumic, and isocaloric intake among the four groups. At the end of the seventh day after completion of the nutritional program, all rats were anesthetized and samples were collected for further analysis. PP apoptosis was measured by terminal deoxyuridine nick-end labeling (TUNEL). The expression of Hsp90 in PPs was analyzed by western blotting. Caspase-3 activity of PPs was also assessed. Levels of proinflammatory cytokines of gut tissues were evaluated by enzyme-linked immunosorbent assay (ELISA). The intestinal immunoglobulin A (IgA) content was also determined by ELISA.

RESULTS

The results revealed that intestinal IgA content in rats of the burn + EN + GLN group were significantly increased compared with those in the burn + EN + AA group (P < 0.05). The expression of Hsp90 of PPs in rats in the burn + EN + GLN group was significantly upregulated compared with those in the burn + EN + AA group (P < 0.05). On the other hand, levels of proinflammatory cytokines of gut tissues, caspase-3 activity, and the number of TUNEL-stained cells of PPs in rats of the burn + EN + GLN group were markedly decreased compared with those of the burn + EN + AA group (P < 0.05).

CONCLUSIONS

The results of this study show that parenteral glutamine supplementation combined with EN may upregulate the expression of Hsp90, reduce caspase-3 activity, lessen the release of proinflammatory cytokines, attenuate PP apoptosis, and improve intestinal IgA response in burned rats. Clinically, therapeutic efforts to improve intestinal immunity may contribute to a favorable outcome in severely burned patients.

Serum prealbumin and its changes over time are associated with mortality in acute kidney injury

Serum prealbumin is a clinically relevant indicator of nutritional status and inflammation in patients with acute kidney injury (AKI). This study aimed to determine whether serum prealbumin and its longitudinal changes over a week could improve the prediction of 90-day mortality in AKI patients. This prospective cohort study included 340 adults with AKI between 2014 and 2015. There were 94 (27.6%) patient deaths within 90 days. Serum prealbumin level <10 mg/dL at the time of AKI diagnosis was associated with a 155% increased death risk ratio (adjusted hazard ratio [HR], 2.55; 95% confidence interval [CI], 1.18 to 5.49; P = 0.02). Serum prealbumin fall >4 mg/dL was also associated with 90-day mortality in adjusted Cox regression models (HR, 1.79; 95% CI, 1.06 to 3.03; P = 0.03). Compared to serum albumin, mortality-predictability of serum prealbumin (P = 0.01) and its changes (P = 0.01) were both increased. Adding prealbumin and its changes on the conventional covariates improved the prediction of progression to 90-day mortality (NRI 0.29, P = 0.04; aIDI 0.08; P = 0.03). In conclusion, serum prealbumin, and its changes were independent predictors of worse prognosis in AKI, and could be potential surrogates to better predict 90-day mortality.

Protein Feeding in Pediatric Acute Kidney Injury Is Not Associated With a Delay in Renal Recovery

OBJECTIVE

Critically ill children with acute kidney injury (AKI) are at high risk of underfeeding. Newer guidelines for nutrition support recommend higher protein intake. Therefore, the study evaluated the effects of protein feeding on the resolution of AKI and compared energy and protein intake in patients with and without AKI after implementation of Nutrition Support guidelines.

DESIGN

Retrospective study.

SUBJECTS

Five hundred twenty critically ill children from October 2012 to June 2013 and October to December 2013.

MAIN OUTCOME MEASURE

Energy and protein intake in patients with no AKI, resolved, or persistent AKI. Energy and protein intake was documented for days 1-8 of Pediatric Intensive Care Unit stay and in the postimplementation versus preimplementation period of nutrition support guidelines. AKI was defined by modified pRIFLE. Persistent AKI was defined as patients who did not resolve their AKI during the study period.

RESULTS

A higher percentage of patients with resolved and persistent AKI met ≥ 80% of protein needs versus no AKI. After adjustment for Pediatric Risk of Mortality Score, the odds ratio for protein intake of ≥ 80% compared to <80% of estimated protein needs was not significant, which suggests that higher protein intake was not associated with nonresolution of AKI. There were significant improvements in the cumulative protein gap in patients with no AKI in the postimplementation (-1.0 [-1.7 to -0.6] g/kg/day) compared to preimplementation period (-1.3 [-1.7 to -0.9] g/kg/day, P = .001) and persistent AKI in the postimplementation (-0.8 [-1.4 to -0.1] g/kg/day) compared to preimplementation (-1.3 [-1.7 to -0.9] g/kg/day, P = .03).

CONCLUSIONS

Higher protein intake was not associated with a delay in renal recovery in patients with AKI after adjustment for severity of illness. Protein intake was improved in critically ill children with no AKI, resolved, and persistent AKI after implementation of Nutrition Support Guidelines, but underfeeding persisted in these patients.

Effect of parenteral glutamine supplementation combined with enteral nutrition on Hsp90 expression and lymphoid organ apoptosis in severely burned rats

OBJECTIVE

The aim of this study is to investigate the effects of parenteral glutamine(GLN) supplementation combined with enteral nutrition (EN) on heat shock protein 90(Hsp90) expression, apoptosis of lymphoid organs and circulating lymphocytes, immunological function and survival in severely burned rats.

METHODS

Male SD rats were randomly assigned into 4 groups: a sham burn+EN+GLN-free amino acid (AA) group (n=10), a sham burn+EN+GLN group (n=10), a burn+EN+AA group (n=10), and a burn +EN +GLN group (n=10). Two hours after a 30% total body surface area (TBSA), full-thickness scald burn injury on the back was made, the burned rats in two experimental groups (the burn+EN+AA group and the burn+EN +GLN group) were fed with a conventional enteral nutrition solution by oral gavage for 7 days. Simultaneously, the rats in the burn+EN+GLN group were given 0.35g GLN/kg body weight/day once via a tail vein injection for 7 days, whereas those in the burn+EN+AA group were administered isocaloric/isonitrogenous GLN-free amino acid solution (Tyrosine) for comparison. The rats in two sham burn control groups (the sham burn+EN+AA group and the sham burn+EN +GLN group) were treated in the same procedure as above, except for burn injury. All rats in each of the four groups were given 175kcal/kg body wt/day. There was isonitrogenous, isovolumic and isocaloric intake among four groups. At the end of the 7th day after nutritional programme were finished, all rats were anesthetized and samples were collected for further analysis. Serum immunoglobulin quantification was conducted by ELISA. Circulating lymphocyte numbers were counted by Coulter LH-750 Analyzer. The percentages and apoptotic ratio of CD4 and CD8T lymphocytes in circulation were determined by flow cytometry (FCM). The neutrophil phagocytosis index (NPI) was examined. The GLN concentrations in plasma, thymus, spleen and skeletal muscle were measured by high performance liquid chromatography (HPLC). The organ index evaluation and TUNEL analysis of thymus and spleen were carried out. The expression of Hsp90 in thymus and spleen was analyzed by western blotting. Moreover, the survival in burned rats was observed.

RESULTS

The results revealed that parenteral GLN supplementation combined with EN significantly increased the GLN concentrations of plasma and tissues, the serum immunoglobulin content, the circulating lymphocyte number, the CD4/CD8 ratio, the indexes of thymus and spleen, NPI and survival as compared with the burn+EN+AA group (p<0.05). The expression of Hsp90 in thymus and spleen in the burn+EN+GLN group was significantly up-regulated as compared with the burn+EN+AA group (p<0.05). The apoptosis in circulating CD4 and CD8 lymphocytes, thymus and spleen in the burn+EN+GLN group was significantly decreased as compared with the burn+EN+AA group (p<0.05).

CONCLUSION

The results of this study show that parenteral GLN supplementation combined with EN may increase the GLN concentrations of plasma and tissues, up-regulate the expression of Hsp90, attenuate apoptosis in lymphoid organ and circulating lymphocyte, enhance the immunological function and improve survival in severely burned rats. Clinically, therapeutic efforts at the modulation of the immune dysfunction may contribute to a favorable outcome in severely burned patients.

Renoprotective approaches and strategies in acute kidney injury

Acute kidney injury (AKI) is a major renal disease associated with high mortality rate and increasing prevalence. Decades of research have suggested numerous chemical and biological agents with beneficial effects in AKI. In addition, cell therapy and molecular targeting have been explored for reducing kidney tissue damage and promoting kidney repair or recovery from AKI. Mechanistically, these approaches may mitigate oxidative stress, inflammation, cell death, and mitochondrial and other organellar damage, or activate cytoprotective mechanisms such as autophagy and pro-survival factors. However, none of these findings has been successfully translated into clinical treatment of AKI. In this review, we analyze these findings and propose experimental strategies for the identification of renoprotective agents or methods with clinical potential. Moreover, we propose the consideration of combination therapy by targeting multiple targets in AKI.

The metabolites of glutamine prevent hydroxyl radical-induced apoptosis through inhibiting mitochondria and calcium ion involved pathways in fish erythrocytes

The present study explored the apoptosis pathways in hydroxyl radicals ((∙)OH)-induced carp erythrocytes. Carp erythrocytes were treated with the caspase inhibitors in physiological carp saline (PCS) or Ca(2+)-free PCS in the presence of 40μM FeSO4/20μM H2O2. The results showed that the generation of reactive oxygen species (ROS), the release of cytochrome c and DNA fragmentation were caspase-dependent, and Ca(2+) was involved in calpain activation and phosphatidylserine (PS) exposure in (∙)OH-induced carp erythrocytes. Moreover, the results suggested that caspases were involved in PS exposure, and Ca(2+) was involved in DNA fragmentation in (∙)OH-induced fish erythrocytes. These results demonstrated that there might be two apoptosis pathways in fish erythrocytes, one is the caspase and cytochrome c-dependent apoptosis that is similar to that in mammal nucleated cells, the other is the Ca(2+)-involved apoptosis that was similar to that in mammal non-nucleated erythrocytes. So, fish erythrocytes may be used as a model for studying oxidative stress and apoptosis in mammal cells. Furthermore, the present study investigated the effects of glutamine (Gln)'s metabolites [alanine (Ala), citrulline (Cit), proline (Pro) and their combination (Ala10Pro4Cit1)] on the pathways of apoptosis in fish erythrocytes. The results displayed that Ala, Cit, Pro and Ala10Pro4Cit1 effectively suppressed ROS generation, cytochrome c release, activation of caspase-3, caspase-8 and caspase-9 at the physiological concentrations, prevented Ca(2+) influx, calpain activation, PS exposure, DNA fragmentation and the degradation of the cytoskeleton and oxidation of membrane and hemoglobin (Hb) and increased activity of anti-hydroxyl radical (AHR) in (∙)OH-induced carp erythrocytes. Ala10Pro4Cit1 produced a synergistic effect of inhibited oxidative stress and apoptosis in fish erythrocytes. These results demonstrated that Ala, Cit, Pro and their combination can protect mammal erythrocytes and nucleated cells against oxidative stress and apoptosis. The studies supported the use of Gln, Ala, Cit and Pro as oxidative stress and apoptosis inhibitors in mammal cells and the hypothesis that the inhibited effects of Gln on oxidative stress and apoptosis are at least partly dependent on that of its metabolites in mammalian.

Pathophysiological role of different tubular epithelial cell death modes in acute kidney injury

The histological substrate of many forms of intrinsic acute kidney injury (AKI) has been classically attributed to tubular necrosis. However, more recent studies indicate that necrosis is not the main form of cell death in AKI and that other forms such as apoptosis, regulated necrosis (i.e. necroptosis and parthanatos), autophagic cell death and mitotic catastrophe, also participate in AKI and that their contribution depends on the cause and stage of AKI. Herein, we briefly summarize the main characteristics of the major types of cell death and we also critically review the existing evidence on the occurrence of different types of cell death reported in the most common experimental models of AKI and human specimens. We also discuss the pathophysiological mechanisms linking tubule epithelial cell death with reduced glomerular filtration, azotaemia and hydroelectrolytic imbalance. For instance, special relevance is given to the analysis of the inflammatory component of some forms of cell death over that of others, as an important and differential pathophysiological determinant. Finally, known molecular mechanisms and signalling pathways involved in each cell death type pose appropriate targets to specifically prevent or reverse AKI, provided that further knowledge of their participation and repercussion in each AKI syndrome is progressively increased in the near future.

Effects of enteral nutrition with parenteral glutamine supplementation on the immunological function in septic rats

The aim of the present study was to investigate the effects of enteral nutrition (EN) with parenteral glutamine (GLN) supplementation on inflammatory response, lymphatic organ apoptosis, immunological function and survival in septic rats by caecal ligation and puncture (CLP). Male rats were randomly assigned into two experimental groups and two sham CLP control groups (n 10 per group). After CLP or sham CLP model and nutrition programme were completed, the GLN concentrations of plasma and tissues and several indices of immunological function including serum Ig content, circulating lymphocyte number, the CD4:CD8 ratio, the neutrophil phagocytosis index (NPI), the organ index and apoptosis of thymus and spleen, and plasma cytokine levels were determined. Moreover, the survival in septic rats was observed. The results revealed that EN with parenteral GLN supplementation remarkably increased the GLN concentrations of plasma and tissues, serum Ig content, the circulating lymphocyte number, the CD4:CD8 ratio, the indexes of thymus and spleen, NPI and survival compared with the control group (P< 0·05). In contrast, the apoptosis of thymus and spleen and the levels of TNF-α, IL-1β and IL-6 in plasma were obviously decreased compared with the control group (P< 0·05). These results show that EN with parenteral GLN supplementation diminished the release of inflammatory cytokines, attenuated lymphatic organ apoptosis, enhanced the immunological function and improved survival in septic rats.

Parenteral glutamine supplementation in combination with enteral nutrition improves intestinal immunity in septic rats

OBJECTIVES

The gut-associated lymphoid tissue is continuously exposed to antigens in the gut lumen and becomes the first line of defense against enteric bacteria and associated toxin. The aim of this study was to investigate the effects of parenteral glutamine (GLN) supplementation in combination with enteral nutrition (EN) on intestinal mucosal immunity in septic rats by cecal ligation and puncture (CLP).

METHODS

Male Sprague-Dawley rats were randomly assigned into four groups: A sham CLP + EN + saline group (n = 10), a sham CLP + EN + GLN group (n = 10), a CLP + EN + saline group (n = 10), and a CLP + EN + GLN group (n = 10). At 2 h after CLP or sham CLP, all rats in each of the four groups received an identical enteral nutrition solution as their base formula. Then, the rats in the sham CLP + EN + GLN group and CLP + EN + GLN group were given 0.35 g GLN/kg body weight daily for 7 d, all at the same time, via a tail vein injection; whereas those in the sham CLP + EN + saline group and CLP + EN + saline group were daily administered isovolumic sterile 0.9% saline for comparison. All rats in each of the four groups were given 290 kcal/kg body wt/d for 7 d. At the end of the seventh day after the nutritional program was finished, all rats were euthanized and the entire intestine was collected. Total Peyer's patches (PP) cell yield was counted by a hemocytometer. The percentage of PP lymphocyte subsets was analyzed by flow cytometry. The number of intestinal lamina propria IgA plasma cells was determined by the immunohistochemistry technique. The intestinal immunoglobulin A (IgA) levels were assessed by ELISA. PP apoptosis was evaluated by terminal deoxyuridine nick-end labeling.

RESULTS

The results revealed total PP cell yield, the numbers of PP lymphocyte subsets, intestinal lamina propria IgA plasma cells, and intestinal IgA levels in the CLP + EN + GLN group were significantly increased when compared with the CLP + EN + saline group (P < 0.05). On the other hand, the number of TUNEL-stained cells within PPs in the CLP + EN + GLN group was markedly decreased as compared with the CLP + EN + saline group (P < 0.05).

CONCLUSION

The results of this study show that parenteral glutamine supplementation in combination with enteral nutrition may attenuate PP apoptosis, increase PP cell yield and intestinal lamina propria IgA plasma cells, and subsequently improve intestinal mucosal immunity. Clinically, these results suggest therapeutic efforts at improving intestinal immunity may contribute to the prevention and treatment of sepsis.

Nutritional evaluation and management of AKI patients

Protein-energy wasting is common in patients with acute kidney injury (AKI) and represents a major negative prognostic factor. Nutritional support as parenteral and/or enteral nutrition is frequently needed because the early phases of this are often a highly catabolic state, although the optimal nutritional requirements and nutrient intake composition remain a partially unresolved issue. Nutrient needs of patients with AKI are highly heterogeneous, depending on different pathogenetic mechanisms, catabolic rate, acute and chronic comorbidities, and renal replacement therapy (RRT) modalities. Thus, quantitative and qualitative aspects of nutrient intake should be frequently evaluated in this clinical setting to achieve better individualization of nutritional support, to integrate nutritional support with RRT, and to avoid under- and overfeeding. Moreover, AKI is now considered a kidney-centered inflammatory syndrome; indeed, recent experimental data indicate that specific nutrients with anti-inflammatory effects could play an important role in the prevention of renal function loss after an episode of AKI.

Specialized nutritional support interventions in critically ill patients on renal replacement therapy

PURPOSE OF REVIEW

Optimal nutritional requirements and nutrient intake composition for patients with acute kidney injury remain a partially unresolved issue. Targeting nutritional support to the actual protein and energy needs improves the clinical outcome of critically ill patients, yet very few data are currently available on this topic in acute kidney injury. In this specific clinical condition the risk for underfeeding and overfeeding may be increased by factors interfering on nutrient need estimation, such as rapidly changing body weight due to fluid balance variations, nutrient losses and hidden calorie sources from renal replacement therapy. Moreover, as acute kidney injury is now considered a kidney-centered inflammatory syndrome, the renoprotective role of specific pharmaconutrients with anti-inflammatory properties remains to be fully defined. This review is aimed at discussing recently published results concerning quantitative and qualitative aspects of the nutritional approach to acute kidney injury in critically ill patients.

RECENT FINDINGS

Nutrient needs in patients with acute kidney injury can be difficult to estimate, and should be directly measured, especially in the ICU setting. In fact, recent findings suggest that hidden calorie sources not routinely taken into account - for example, calories from anticoagulants and replacement solutions for renal replacement therapy - could be quantitatively relevant in these patients. Moreover, recent experimental data indicate a possible role for some pharmaconutrients with anti-inflammatory effects (glutamine, and omega-3 fatty acids), in both the prevention of renal function worsening, and in the fostering of renal function recovery after an episode of acute kidney injury.

SUMMARY

Acute kidney injury includes a highly heterogeneous group of patients with widely varying nutrient needs and intakes. Nutritional requirements, in their quantitative and qualitative aspects, should be frequently assessed, individualized, and carefully integrated with renal replacement therapy, in order to avoid both underfeeding and overfeeding, as well as to exploit possible positive pharmacologic effects of specific nutrients.

The anti-oxidant effects are not the main mechanism for glutamine's protective effects on acute kidney injury in mice

Acute kidney injury (AKI) is a common problem characterized by an inflammatory response in the kidney and oxidative stress. However, there are no interventions to prevent AKI. Glutamine is an important precursor of glutathione and has also been shown to induce heat shock proteins (HSP). Thus, glutamine may affect both oxidative stress and inflammation. This study was to explore the effects of glutamine pretreatment on nephrotoxic AKI and to investigate the underlying mechanisms. First, the effects of alternate doses of glutamine were compared in CD-1 mice with AKI induced with folic acid intra-peritoneal injection. Then the effects of glutamine quercetin (an HSP inhibitor), and quercetin+glutamine, were compared in the same AKI model. AKI were assessed with plasma creatinine, urine neutrophil gelatinase-associated lipocalin, and renal histology. Inflammatory response was monitored with renal tumor necrosis factor (TNF-α), chemkines (CXCL1 and CCL2) contents, and neutrophil infiltration. Oxidative injury was detected with reduced glutathione, malondialdehyde, and protein thiol. Glutamine provided dose-dependent renal protection. Pretreatment with quercetin, which was showed to inhibit HSP-70 expression, abolished glutamine's renal-protective effects. Quercetin also abrogated glutamine's beneficial effects on renal TNF-α, chemokines, and neutrophil infiltration. However, quercetin did not affect glutamine's anti-oxidative effects. These results suggest that glutamine's renal-protective effects are mainly related to its activation of HSP-70, which mitigates inflammatory response, renal neutrophil infiltration and subsequent AKI. Regulating neutrophil infiltration might be a potential therapeutic target for AKI.

Renal protective effects of early continuous venovenous hemofiltration in rhabdomyolysis: improved renal mitochondrial dysfunction and inhibited apoptosis

Rhabdomyolysis (RM) and subsequent myoglobin (Mb) deposition can lead to acute kidney injury. Continuous venovenous hemofiltration (CVVH) can remove Mb, but direct renal protection is unclear. We hypothesized that CVVH can improve renal mitochondrial dysfunction in its early stage. Twenty-four mongrel dogs were randomly divided into four groups: (A) control; (B) model; (C) model + CVVH (50 mL/kg/h); and (D) model + CVVH (30 mL/kg/h). RM was induced by glycerol via intramuscular injection. The dogs were closely monitored for urine flow and renal function. Mb, plasma tumor necrosis factor-α (TNF-α), and interleukin (IL)-6 were measured by enzyme-linked immunosorbent assay. After 8 h of CVVH, the morphological changes of renal mitochondria were observed and mitochondrial function indicators (reactive oxygen species, malondialdehyde, and respiratory control index) were detected. Western blot analysis was used to detect the expression of Mb, TNF-α, and IL-6 in renal tubules. The terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay method and Western blot analysis were used to detect apoptosis and apoptosis-related proteins. In group B, the dog urine output gradually decreased with increased blood creatinine. In groups C and D, the urine output was normal and stable. CVVH effectively eliminated Mb. High-dose CVVH was significantly better for removal efficiency than low-dose CVVH. CVVH significantly reduced the deposition of circulating Mb in the kidney in a dose-dependent manner. The impact of CVVH on TNF-α and IL-6 were not observed. The morphological changes of mitochondria and function indicators were significantly improved in group C compared with groups D and B. Compared with group B, renal apoptosis and apoptosis-related protein expression were inhibited in groups C and D. Group C was significantly better for mitochondrial improvement and apoptosis inhibition than group D. At the cellular and molecular level, CVVH can improve renal mitochondrial function and inhibit cell apoptosis. Early CVVH can protect from RM-caused renal injuries in a dose-dependent manner.

Nutrition support among critically ill children with AKI

BACKGROUND

Critically ill children are at high risk of underfeeding and AKI, which may lead to further nutritional deficiencies. This study aimed to determine the adequacy of nutrition support during the first 5 days of intensive care unit (ICU) stay.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A chart review of pediatric patients admitted to the pediatric ICU for >72 hours between August 2007 and March 2008 was conducted. Patients were classified as having no AKI versus AKI by modified pediatric RIFLE criteria. All nutrition was analyzed. Basal metabolic rate (BMR) was estimated by the Schofield equation and protein needs by American Society for Parenteral and Enteral Nutrition guidelines.

RESULTS

Of the 167 patients, 102 were male and 65 were female (median age 1.4 years). Using the RIFLE criteria, 102 (61%) patients had no AKI, whereas 44 (26%) were classified as category R (risk), 12 (7%) as category I (injury), and 9 (5%) as category F (failure). The median 5-day energy intake was lower relative to estimated BMR. Overall protein provision (19%) was lower than energy provision (55%) compared with estimated needs (P<0.001). I/F patients were more likely to be fasted versus receiving enteral/parenteral nutrition (n=813 patient days) and to receive <90% of BMR (n=832 patient days) than No AKI/R patients.

CONCLUSIONS

Underfeeding, common in critically ill children, was accentuated in AKI. Protein underfeeding was greater than energy underfeeding in the first 5 days of PICU stay. Efforts should be made to provide adequate nutrition in ICU patients with AKI.

Zinc oxide nanoparticles cause nephrotoxicity and kidney metabolism alterations in rats

Although zinc oxide nanoparticles (ZnO NPs) have been widely used, their potential hazards on mammalian and human remain largely unknown. In this study, the biochemical compositions of urine and kidney from the rats treated with ZnO NPs (100, 300 and 1000 mg/kg, respectively) were investigated using (1)H nuclear magnetic resonance (NMR) technique with the pattern recognition of partial least squares-discriminant analysis. Hematology, clinical biochemistry and kidney histopathological examinations were also performed. Metabolic profiles from rats treated with ZnO NP(S) exhibited increases in the levels of taurine, lactate, acetate, creatine, phosphocholine, trimethylamine-N-oxide, α-glucose, and 3-D-hydroxybutyrate, as well as decreases in lipid, succinate, citrate, α-ketoglutarate, hippurate and 4-hydroxyphenylacetic acid in urine after ZnO NPs treatment for 14 days. A similar alteration pattern was also identified in kidney. Urine choline and phosphocholine increased significantly shortly after ZnO NPs treatment, moreover, some amino acids and glucose also increased during the experimental period. However, succinate, citrate and α-ketoglutarate in urine exhibited a different alteration trend, which showed increases on the first day after ZnO NPs treatment, but decreases gradually until the termination of the study. A similar alteration pattern of urinary (1)H NMR spectra was also detected in kidney. Moreover, ZnO NPs (1000 mg/kg) resulted in significant increases in serum creatine and blood urea nitrogen, decreases in hemoglobin, haematocrit and mean corpuscular hemoglobin concentration, and overt tubular epithelial cell necrosis. These findings show that ZnO NPs can disturb the energy metabolism and cause mitochondria and cell membrane impairment in rat kidney, which may contribute to ZnO NPs-induced nephrotoxicity.

Augmenter of liver regeneration attenuates tubular cell apoptosis in acute kidney injury in rats: the possible mechanisms

Augmenter of liver regeneration (ALR), the expression of which increased in rat kidneys after renal ischemia/reperfusion (I/R) injury, enhances renal tubular cell regeneration in vivo and in vitro. We aimed to investigate the effects of ALR on apoptosis of renal tubular cells after renal I/R injury in vivo and consider the possible mechanisms. Rats that were subjected to bilateral renal ischemia for 60 min followed by reperfusion were administered with either vehicle or recombinant human ALR (rhALR). Renal dysfunction and histologic injury were assessed by the measurement of serum biochemical markers and histological grading. Apoptosis was assessed by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL). Caspase-3 activity was measured using a colorimetric protease assay. Expression of Bcl-2, Bax Fas, phosphorylated-Akt (p-Akt), and phosphorylated-p53 (p-p53) was determined by western blotting. Compared with vehicle-treated rats, renal dysfunction and histologic injury were significantly attenuated by administration of rhALR. The number of TUNEL-positive tubular cells and caspase-3 activity were decreased, Bcl-2 and p-Akt expression was up-regulated, and Bax and p-p53 expression was down-regulated by administration of rhALR. However, administration of rhALR had no effect on Fas protein expression. These results indicate that the protective effect of rhALR on renal I/R injury is associated with its anti-apoptotic action in renal tubular cells. RhALR inhibits apoptosis by increasing the ratio of Bcl-2 to Bax and by decreasing the activity of caspase-3. The activation of Akt and inactivation of p53 are involved in the rhALR anti-apoptosis process.

Preventive effects of hyperbaric oxygen treatment on glycerol-induced myoglobinuric acute renal failure in rats

Myoglobinuric acute renal failure (ARF) is a uremic syndrome caused by traumatic or non-traumatic skeletal muscle breakdown and intracellular elements that are released into the bloodstream. We hypothesized that hyperbaric oxygen (HBO) therapy could be beneficial in the treatment of myoglobinuric ARF caused by rhabdomyolysis. A total of 32 rats were used in the study. The rats were divided into four groups: control, control+hyperbaric oxygen (control+HBO), ARF, and ARF+hyperbaric oxygen (ARF+HBO). Glycerol (8 ml/kg) was injected into the hind legs of each of the rats in ARF and ARF+HBO groups. 2.5 atmospheric absolute HBO was applied to the rats in the control+HBO and ARF+HBO groups for 90 min on two consecutive days. Plasma urea, creatinine, sodium, potassium, calcium, aspartate aminotransferase, alanine aminotransferase, lactic dehydrogenase, creatinine kinase and urine creatinine and sodium were examined. Creatinine clearance and fractional sodium excretion could then be calculated. Superoxide dismutase, catalase, glutathione and malondialdehyde (MDA) levels were assessed in renal tissue. Tissue samples were evaluated by Hematoxylin-eosin, PCNA and TUNEL staining histopathologically. MDA levels were found to be significantly decreased whereas SOD and CAT were twofold higher in the ARF+HBO group compared to the ARF group. Renal function tests were ameliorated by HBO therapy. Semiquantitative evaluation of histopathological findings indicated that necrosis and cast formation was decreased by HBO therapy and TUNEL staining showed that apoptosis was inhibited. PCNA staining showed that HBO therapy did not increase regeneration. Ultimately, we conclude that, in accordance with our hypothesis, HBO could be beneficial in the treatment of myoglobinuric ARF.

Post-translational modification of 14-3-3 isoforms and regulation of cellular function

14-3-3 is now well established as a family of dimeric proteins that can modulate interaction between proteins involved in a wide range of functions. In many cases, these proteins show a distinct preference for a particular isoform(s) of 14-3-3 and in many cases a specific repertoire of dimer formation influences the particular proteins that 14-3-3 interact. Well over 200 proteins have been shown to interact with 14-3-3. The purpose of this review is to give an overview of the recently identified post-translational modifications of 14-3-3 isoforms and how this regulates function, interaction, specificity of dimerisation between isoforms and cellular location of target proteins. The association between 14-3-3 and its targets usually involves phosphorylation of the interacting protein which has been the subject of many reviews and discussion of this is included in other reviews in this series. However, it is now realised that in some cases the phosphorylation and a number of other, novel covalent modifications of 14-3-3 isoforms may modulate interaction and dimerisation of 14-3-3. Since this aspect is now emerging to be of major importance in the mechanism of regulation by 14-3-3 isoforms and has not been the focus of previous reviews, this will be detailed here.

Cyclooxygenase-2-dependent phosphorylation of the pro-apoptotic protein Bad inhibits tonicity-induced apoptosis in renal medullary cells

During antidiuresis, cell survival in the renal medulla requires cyclooxygenase-2 (COX-2) activity. We have recently found that prostaglandin E2 (PGE2) promotes cell survival by phosphorylation and, hence, inactivation of the pro-apoptotic protein Bad during hypertonic stress in Madin-Darby canine kidney (MDCK) cells in vitro. Here we determine the role of COX-2-derived PGE(2) on phosphorylation of Bad and medullary apoptosis in vivo using COX-2-deficient mice. Both wild-type and COX-2-knockout mice constitutively expressed Bad in tubular epithelial cells of the renal medulla. Dehydration caused a robust increase in papillary COX-2 expression, PGE2 excretion, and Bad phosphorylation in wild-type, but not in the knockout mice. The abundance of cleaved caspase-3, a marker of apoptosis, was significantly higher in papillary homogenates, especially in tubular epithelial cells of the knockout mice. Knockdown of Bad in MDCK cells decreased tonicity-induced caspase-3 activation. Furthermore, the addition of PGE2 to cells with knockdown of Bad had no effect on caspase-3 activation; however, PGE2 caused phosphorylation of Bad and substantially improved cell survival in mock-transfected cells. Thus, tonicity-induced COX-2 expression and PGE2 synthesis in the renal medulla entails phosphorylation and inactivation of the pro-apoptotic protein Bad, thereby counteracting apoptosis in renal medullary epithelial cells.

Apoptosis and acute kidney injury

Improved mechanistic understanding of renal cell death in acute kidney injury (AKI) has generated new therapeutic targets. Clearly, the classic lesion of acute tubular necrosis is not adequate to describe the consequences of renal ischemia, nephrotoxin exposure, or sepsis on glomerular filtration rate. Experimental evidence supports a pathogenic role for apoptosis in AKI. Interestingly, proximal tubule epithelial cells are highly susceptible to apoptosis, and injury at this site contributes to organ failure. During apoptosis, well-orchestrated events converge at the mitochondrion, the organelle that integrates life and death signals generated by the BCL2 (B-cell lymphoma 2) protein family. Death requires the 'perfect storm' for outer mitochondrial membrane injury to release its cellular 'executioners'. The complexity of this process affords new targets for effective interventions, both before and after renal insults. Inhibiting apoptosis appears to be critical, because circulating factors released by the injured kidney induce apoptosis and inflammation in distant organs including the heart, lung, liver, and brain, potentially contributing to the high morbidity and mortality associated with AKI. Manipulation of known stress kinases upstream of mitochondrial injury, induction of endogenous, anti-apoptotic proteins, and improved understanding of the timing and consequences of renal cell apoptosis will inevitably improve the outcome of human AKI.

Phosphorylation mechanisms in intensive care medicine

INTRODUCTION

The phosphorylation states of proteins, lipids, carbohydrates, amino acids, and nucleotides control the mechanisms behind nearly all cellular functions. Therefore, not surprisingly, recent findings have shown that alterations in these phosphorylation pathways play a central role in the development and progression of many disease states. This review provides a brief summary of the function and activity of various phosphorylation mechanisms, outlines some of the major phosphorylation signaling cascades, and describes the role of these phosphorylation mechanisms in intensive care medicine.

METHODS

This article will comprise a comprehensive review of the literature in the context of intensive care medicine. Specifically, we will discuss the involvement of phosphorylation in the pathogenesis, diagnosis, and treatment of heart failure, myocardial infarction, stroke, respiratory failure, ventilation-induced lung injury, traumatic brain injury, acute organ failure, systemic sepsis, and shock.

CONCLUSION

Phosphorylation mechanisms clearly play an important role in many pathologies and treatment strategies of intensive care and therefore further understanding of these mechanisms may lead to the development of novel therapies and improved patient care.

Nutritional assessment and support in acute kidney injury

PURPOSE OF REVIEW

Acute kidney injury (AKI) in the ICU is associated with an increased risk of protein-energy wasting (PEW), a major negative prognostic factor. This review illustrates recently published data and guidelines concerning nutritional problems in AKI, pointing out complexities and peculiarities of the syndrome.

RECENT FINDINGS

The main goals of nutritional support in AKI on renal replacement therapy (RRT) are to ensure the provision of adequate amounts of nutrients, to prevent PEW, to promote tissue reparation, to support the immune system, and possibly to reduce mortality. The enteral route should be preferred, even though parenteral nutrition is often required to target nutritional needs. Special attention should be paid both to the impact of RRT on macronutrient and micronutrient losses, and to the risk of complications. In fact, due to both the acute loss of the kidneys' homeostatic function, and the frequent need of RRT, patients with AKI are especially prone to hypoglycemia and hyperglycemia, hypertriglyceridemia, fluid balance alterations, electrolyte and acid-base derangements.

SUMMARY

This review highlights the most recent concepts and recommendations for nutritional support in AKI, stressing the need for a close integration between adequate nutrition and RRT in this clinical condition, with the aim of carefully tailoring both therapies on patients' changing needs. Recent findings about the renoprotective role of some nutrients (glutamine, omega-3 fatty acids) are also discussed.