NAD+ homeostasis in renal health and disease

L-shaped association between dietary niacin intake and chronic kidney disease among adults in the USA: a cross-sectional study

BACKGROUND

Chronic kidney disease (CKD), which has become a global public health issue, is associated with mitochondrial dysfunction. Niacin is a necessary coenzyme for mitochondrial energy metabolism. However, the association between dietary niacin intake and CKD remains uncertain. This study aimed to investigate the association between dietary niacin intake and CKD in American adults.

METHODS

This is a cross-sectional study. 25,608 individuals aged ≥20 years from the National Health and Nutrition Examination Survey from 2007 to 2018 were involved.Dietary niacin intake was estimated based on 24-hour dietary recalls conducted by trained personnel. CKD was determined by an estimated glomerular filtration rate (eGFR) (<60 ml/min/1.73 m2) or a urinary albumin-to-creatinine ratio (ACR) (≥30mg/g). The association between dietary niacin intake and CKD was investigated using multivariable logistic regression analysis.

RESULTS

Of 25,608 participants, 17.14% (4388/25,608) had CKD. Compared to individuals with lower niacin intake (quartile [Q]1, ≤15.30 mg/day), those with higher niacin intake in Q2 (15.31-22.07 mg/day), Q3 (22.08-31.09 mg/day), and Q4 (≥31.10 mg/day) exhibited adjusted odds ratios for CKD of 0.89 (95% confidence interval [CI]:0.81-0.99, p = 0.024), 0.83 (95% CI:0.75-0 .92, p < 0 .001), and 0.83 (95% CI:0.75-0.93, p = 0.001) respectively. The relationship between dietary niacin intake and CKD among U.S. adults follows an L-shaped pattern, with an inflection point at approximately 28.04 mg/day.

CONCLUSIONS

These results suggest an L-shaped association between dietary niacin intake and CKD. Individuals with low dietary niacin intake levels should be alert to the risk of CKD.

Mitochondrial dysfunction in acute kidney injury

Acute kidney injury (AKI) is a systemic clinical syndrome increasing morbidity and mortality worldwide in recent years. Renal tubular epithelial cells (TECs) death caused by mitochondrial dysfunction is one of the pathogeneses. The imbalance of mitochondrial quality control is the main cause of mitochondrial dysfunction. Mitochondrial quality control plays a crucial role in AKI. Mitochondrial quality control mechanisms are involved in regulating mitochondrial integrity and function, including antioxidant defense, mitochondrial quality control, mitochondrial DNA (mtDNA) repair, mitochondrial dynamics, mitophagy, and mitochondrial biogenesis. Currently, many studies have used mitochondrial dysfunction as a targeted therapeutic strategy for AKI. Therefore, this review aims to present the latest research advancements on mitochondrial dysfunction in AKI, providing a valuable reference and theoretical foundation for clinical prevention and treatment of this condition, ultimately enhancing patient prognosis.

Quantification of relevant metabolites in apoptotic bodies from HK-2 cells by targeted metabolomics based on liquid chromatography-tandem mass spectrometry

BACKGROUND

Apoptotic bodies play an important role in the cellular communication as a consequence of the great variety of biomolecules they harbor. There is evidence that 1st generation apoptotic bodies from HK-2 cells induced by cisplatin or UV light trigger apoptosis in naïve HK-2 cells whereas 2nd generation apoptotic bodies activate cell proliferation showing an opposite effect. Thus, the development of new analytical strategies to quantify the changes in the involved metabolites is imperative to shed light on the biological mechanisms which trigger apoptosis and cell proliferation.

RESULTS

A LC-(Q-Orbitrap)MS method has been developed to quantify the metabolites unequivocally identified in the apoptotic body fluid from HK-2 cells in our previous works based on untargeted metabolomics. Thus, two different columns and gradients were tested and the HILIC column was selected taking into account the retention times and chromatographic separation. Also, different normal collision energies were tested for each metabolite and the parallel reaction monitoring was chosen to carry out the quantitative analysis. Once the method was optimized, it was evaluated in terms of linearity, limits of detection and quantification, matrix effects, accuracy, and precision, for each metabolite. Limits of detection ranged from 0.02 to 1.4 ng mL-1. A total of 9 relevant metabolites proposed as potential biomarkers to reveal metabolic differences among apoptotic bodies from HK-2 cells were quantified and some insights about the biological relevance were discussed.

SIGNIFICANCE

The first targeted metabolomics methodology enabling the quantification of relevant metabolites in apoptotic bodies from HK-2 cells was developed using LC-(Q-Orbitrap)MS. Pyridoxine, kynurenine, and creatine concentrations were determined in apoptotic bodies from HK-2 cells treated with cisplatin and UV light. Phenylacetylglycine, hippuric acid, butyrylcarnitine, acetylcarnitine, carnitine, and phenylalanine were determined in 1st and 2nd generation apoptotic bodies from HK-2 cells treated with cisplatin. Concentrations determined were useful to establish their biological role in the metabolism.

Multifunctional Ru(III)/Fe3O4/DNA nanoplatform for photothermal-enhanced photodynamic and chemodynamic cancer therapy

Among the many cancer treatment methods, there have been many reports on the use of nanoplatforms with single treatment methods such as photothermal, photodynamic or chemodynamic for cancer treatment. In this study, Ru(III) with photodynamic effect and Fe3O4 nanoparticles with photothermal and chemodynamic effects are connected through long DNA chains with efficient active targeting rolling circle amplification to construct Ru(III)/Fe3O4/DNA nano-platform realizes the combination of photothermal, photodynamic and chemodynamic treatment, which significantly improves the therapeutic effect of the nano-platform. Its multiple active targeting capabilities reduce the damage to normal cells. Ru(III) has excellent photodynamic effect and can catalyze the respiration product NADH (Nicotinamide adenine dinucleotide)to produce highly oxidizing H2O2. Fe3O4 NPs has weak absorption at 808 nm indicates that it can perform mild photothermal treatment, and the Fe2+ in it can react with H2O2 to produce ·OH and participate in chemodynamic treatment. Each repeating unit on the rolling circle amplified DNA long chain is connected to the AS1411 aptamer that can actively target cancer cells. Unlike the passive targeting of other nanomedicines, active and efficient targeting is achieved, and a small amount of drugs can achieve high efficacy. The therapeutic effect also reduces the damage to normal cells. The comprehensive killing effect of Ru(III)/Fe3O4/DNA can reach 85.1 %. Its high targeting of cancer cells can also be used for imaging detection of cancer cells. This new nanoplatform provides an idea for the synergy of multiple cancer treatments.

Dual Time-Dependent Effects of Interleukin-33 Administration on the Kidney Postmyocardial Infarction

Kidney damage is a serious prevalent complication that occurs after a myocardial infarction (MI) and is associated with worse outcomes. Interleukin-33 (IL-33), a member of the IL-1 superfamily, functions as an alarmin that is released upon necrosis or tissue damage to alert immune cells expressing the ST2L receptor. IL-33 is increased in kidney disease, and recent studies have shown that the IL-33/ST2 axis is instrumental in both disease progression and repair. In this study, we investigated the effect of IL-33 administration on kidneys in C57BL6/J male mice 4 and 7 days after the induction of MI. The mice received either IL-33 or vehicle (PBS) treatment. Cardiac systolic function and systemic inflammation were assessed, and kidneys were subjected to histological and molecular analysis. The administration of IL-33 for 4 days post-MI improved renal structure consistent with reduced expression of profibrotic markers, reduced apoptosis, and increased expression of the anti-inflammatory cytokine IL-4. In addition, IL-33 administration enhanced the levels of Sirtuin3, nicotinamide phosphoribosyltransferase, and the renal nicotinamide adenine dinucleotide pool which are critical for mitochondrial function and energy production, indicating metabolic benefits. However, this protection seems to be lost with the continued administration of IL-33 for 7 days post-MI coinciding with aggravated cardiac dysfunction and increased systemic inflammation. These findings demonstrate that while IL-33 treatment can help improve kidney damage post-MI in the short term, extended treatment may not be beneficial. This may be due to the direct effects of IL-33 on the kidneys or indirectly mediated by adverse cardiac remodeling influencing the cardiorenal crosstalk.

Ablation of NAMPT in dopaminergic neurons leads to neurodegeneration and induces Parkinson's disease in mouse

Nicotinamide phosphoribosyltransferase (NAMPT) is the key enzyme in the salvaging synthesize pathway of nicotinamide adenine dinucleotide (NAD). The neuroprotective roles of NAMPT on neurodegeneration have been explored in aging brain and Alzheimer's Disease. However, its roles in Parkinson's Disease (PD) remain to be elucidated. We found that the dopaminergic neurons in substantia nigra expressed higher levels of NAMPT than the other types of neurons. Using conditional knockout of the Nampt gene in dopaminergic neurons and utilizing a NAMPT inhibitor in the substantia nigra of mice, we found that the NAMPT deficiency triggered the time-dependent loss of dopaminergic neurons, the impairment of the dopamine nigrostriatal pathway, and the development of PD-like motor dysfunction. In the rotenone-induced PD mouse model, nicotinamide ribose (NR), a precursor of NAD, rescued the loss of dopaminergic neurons, the impairment of dopamine nigrostriatal pathway, and mitigated PD-like motor dysfunction. In SH-SY5Y cells, NAD suppression induced the accumulation of reactive oxygen species (ROS), mitochondrial impairment, and cell death, which was reversed by N-acetyl cysteine, an antioxidant and ROS scavenger. Rotenone decreased NAD level, induced the accumulation of ROS and the impairment of mitochondria, which was reversed by NR. In summary, our findings show that the ablation of NAMPT in dopaminergic neurons leads to neurodegeneration and contributes to the development of PD. The NAD precursors have the potential to protect the degeneration of dopaminergic neurons, and offering a therapeutic approach for the treatment of PD.

β-carotene protects against α-amanitin nephrotoxicity via modulation of oxidative, autophagic, nitric oxide signaling, and polyol pathways in rat kidneys

Alpha-amanitin (α-AMA), a toxic component of Amanita phalloides, causes severe hepato- and nephrotoxicity. This study investigated the protective effects of βeta-carotene (βC) against α-AMA-induced kidney damage in rats. Thirty-two male Sprague-Dawley rats were divided into four groups: Control, βC (50 mg/kg/day), α-AMA (3 mg/kg), and βC+α-AMA. βC was administered orally for 7 days before α-AMA injection. Renal function, oxidative stress markers, histopathological changes, and enzyme activities were evaluated 48 h post-α-AMA administration. α-AMA significantly increased serum creatinine and urea levels, decreased glutathione and catalase activity, and increased malondialdehyde levels (P < 0.001). βC pretreatment attenuated these changes (P < 0.05). Histopathological examination revealed reduced tubular degeneration in the βC+α-AMA group (P < 0.001). Immunohistochemical analysis showed increased LC3B and Beclin-1 expression in α-AMA-treated rats, indicating enhanced autophagy, partially reversed by βC. Additionally, α-AMA reduced nitric oxide synthase (NOS) activity and increased aldose reductase (AR) activity, both normalized by βC pretreatment (P < 0.01). βC demonstrates protective effects against α-AMA-induced nephrotoxicity through antioxidant action, modulation of autophagy, and regulation of NOS and AR pathways, suggesting its potential as a therapeutic agent in α-AMA poisoning.

Metabolome and Transcriptome Profiling Reveals Age-Associated Variations in Meat Quality and Molecular Mechanisms of Taihe Black-Bone Silky Fowls

To explore the changes in meat quality and molecular mechanisms during the growth and development of Taihe black-bone silky fowl, this study employed liquid chromatography-mass spectrometry (LC-MS/MS) metabolomics to elucidate the dynamic changes of key differential metabolites (DMs) affecting meat quality, indicating that chicken at D120 had higher levels of ω-3 polyunsaturated fatty acids (PUFAs), creatine, anserine, and homocarnosine, while D150 had the most stachydrine and D210 had the most acylcarnitines. Additionally, D120 and D180 had more umami and sweet compounds. Furthermore, key metabolic pathways influenced by age included purine metabolism, the pentose phosphate pathway, nicotinate and nicotinamide metabolism, and taurine and hypotaurine metabolism. Transcriptomic identified differential expression genes (DEGs) are predominantly enriched in focal adhesion, the TGF-β signaling pathway, and the MAPK signaling pathway. Integrated metabolomics and transcriptomics revealed complex regulatory networks of DEGs and DMs in key metabolic pathways. This research enhanced our understanding of the biology of Taihe black-bone silky fowl meat quality, revealing possible biomarkers.

Blocking of SIRT7/FOXO3a axis by miR-152-3p enhances cisplatin sensitivity in breast cancer

BACKGROUND

Cisplatin-based chemoresistance is major obstacle for breast cancer (BC) including Triple-negative breast cancer (TNBC). SIRT7 is reportedly involved in the progression of BC, the underlining mechanism in Cisplatin-based chemoresistance in BC remains unclear. This work is to elucidate effects of SIRT7 on cisplatin resistance in breast cancer regulated by miR-152-3p.

METHODS

The RNA expression of SIRT7 and miRNAs in breast cancer were available from TCGA database. SIRT7-targeted miRNAs were predicted by TargetScan, miRanda, miRDB databases. The association of SIRT7 expression with predicted miRNA was validated by Luciferase assay. Cell apoptosis was determined by Flow cytometry. Cell viability was detected by CCK8 assay. The mRNA expression was measured by quantitative real-time polymerase chain reaction (qRT-PCR) assay. Protein expression was determined by Western blotting assay.

RESULTS

SIRT7 mRNA levels were dramatically enhanced in BC tissues compared to para-carcinoma tissues, also increased in BC patients with Cisplatin-based chemotherapy containing TNBC compared with those without. The increase of SIRT7 expression was obviously relevant to shorter survive time of them. Importantly, SIRT7 inhibition facilitated Cisplatin-induced cell apoptosis of TNBC (MDA-MB-231 and MDA-MB-468) and non- TNBC (MCF-7). Notably, miR-152-3p was predicted as a negative regulator of SIRT7 by overlapping downregulated miRNAs in BC patients treated with Cisplatin-based chemotherapy and miRNAs to target SIRT7. Mechanically, miR-152-3p blocked SIRT7 to stimulate an activation of FOXO3a, cleaved PARP1 and Caspase-3, sensitizing Cisplatin-induced apoptosis of BC cells.

CONCLUSIONS

Inhibition of SIRT7 by miR-152-3p may be a promising strategy against the resistance to cisplatin-based chemotherapy in BC containing TNBC.

Inflammation primes the murine kidney for recovery by activating AZIN1 adenosine-to-inosine editing

The progression of kidney disease varies among individuals, but a general methodology to quantify disease timelines is lacking. Particularly challenging is the task of determining the potential for recovery from acute kidney injury following various insults. Here, we report that quantitation of post-transcriptional adenosine-to-inosine (A-to-I) RNA editing offers a distinct genome-wide signature, enabling the delineation of disease trajectories in the kidney. A well-defined murine model of endotoxemia permitted the identification of the origin and extent of A-to-I editing, along with temporally discrete signatures of double-stranded RNA stress and adenosine deaminase isoform switching. We found that A-to-I editing of antizyme inhibitor 1 (AZIN1), a positive regulator of polyamine biosynthesis, serves as a particularly useful temporal landmark during endotoxemia. Our data indicate that AZIN1 A-to-I editing, triggered by preceding inflammation, primes the kidney and activates endogenous recovery mechanisms. By comparing genetically modified human cell lines and mice locked in either A-to-I-edited or uneditable states, we uncovered that AZIN1 A-to-I editing not only enhances polyamine biosynthesis but also engages glycolysis and nicotinamide biosynthesis to drive the recovery phenotype. Our findings implicate that quantifying AZIN1 A-to-I editing could potentially identify individuals who have transitioned to an endogenous recovery phase. This phase would reflect their past inflammation and indicate their potential for future recovery.

Perspectives on the involvement of the gut microbiota in salt-sensitive hypertension

Salt-sensitivity hypertension (SSH) is an independent predictor of cardiovascular event-related death. Despite the extensiveness of research on hypertension, which covers areas such as the sympathetic nervous system, the renin-angiotensin system, the vascular system, and the immune system, its pathogenesis remains elusive, with sub-optimal blood pressure control in patients. The gut microbiota is an important component of nutritional support and constitutes a barrier in the host. Long-term high salt intake can lead to gut microbiota dysbiosis and cause significant changes in the expression of gut microbiota-related metabolites. Of these metabolites, short chain fatty acids (SCFAs), trimethylamine oxide, amino acids, bile acids, and lipopolysaccharide are essential mediators of microbe-host crosstalk. These metabolites may contribute to the incidence and development of SSH via inflammatory, immune, vascular, and nervous pathways, among others. In addition, recent studies, including those on the histone deacetylase inhibitory mechanism of SCFAs and the blood pressure-decreasing effects of H2S via vascular activation, suggest that several proteins and factors in the classical pathway elicit their effects through multiple non-classical pathways. This review summarizes changes in the gut microbiota and its related metabolites in high-salt environments, as well as corresponding treatment methods for SSH, such as diet management, probiotic and prebiotic use, antibiotic use, and fecal transplantation, to provide new insights and perspectives for understanding SSH pathogenesis and the development of strategies for its treatment.

Homeostatic regulation of NAD(H) and NADP(H) in cells

Nicotinamide adenine dinucleotide (NAD+)/reduced NAD+ (NADH) and nicotinamide adenine dinucleotide phosphate (NADP+)/reduced NADP+ (NADPH) are essential metabolites involved in multiple metabolic pathways and cellular processes. NAD+ and NADH redox couple plays a vital role in catabolic redox reactions, while NADPH is crucial for cellular anabolism and antioxidant responses. Maintaining NAD(H) and NADP(H) homeostasis is crucial for normal physiological activity and is tightly regulated through various mechanisms, such as biosynthesis, consumption, recycling, and conversion between NAD(H) and NADP(H). The conversions between NAD(H) and NADP(H) are controlled by NAD kinases (NADKs) and NADP(H) phosphatases [specifically, metazoan SpoT homolog-1 (MESH1) and nocturnin (NOCT)]. NADKs facilitate the synthesis of NADP+ from NAD+, while MESH1 and NOCT convert NADP(H) into NAD(H). In this review, we summarize the physiological roles of NAD(H) and NADP(H) and discuss the regulatory mechanisms governing NAD(H) and NADP(H) homeostasis in three key aspects: the transcriptional and posttranslational regulation of NADKs, the role of MESH1 and NOCT in maintaining NAD(H) and NADP(H) homeostasis, and the influence of the circadian clock on NAD(H) and NADP(H) homeostasis. In conclusion, NADKs, MESH1, and NOCT are integral to various cellular processes, regulating NAD(H) and NADP(H) homeostasis. Dysregulation of these enzymes results in various human diseases, such as cancers and metabolic disorders. Hence, strategies aiming to restore NAD(H) and NADP(H) homeostasis hold promise as novel therapeutic approaches for these diseases.

NAD deficiency contributes to progressive kidney disease in HIV-nephropathy mice

HIV disease remains prevalent in the United States and is particularly prevalent in sub-Saharan Africa. Recent investigations revealed that mitochondrial dysfunction in kidney contributes to HIV-associated nephropathy (HIVAN) in Tg26 transgenic mice. We hypothesized that nicotinamide adenine dinucleotide (NAD) deficiency contributes to energetic dysfunction and progressive tubular injury. We investigated metabolomic mechanisms of HIVAN tubulopathy. Tg26 and wild-type (WT) mice were treated with the farnesoid X receptor (FXR) agonist INT-747 or nicotinamide riboside (NR) from 6 to 12 wk of age. Multiomic approaches were used to characterize kidney tissue transcriptomes and metabolomes. Treatment with INT-747 or NR ameliorated kidney tubular injury, as shown by serum creatinine, the tubular injury marker urinary neutrophil-associated lipocalin, and tubular morphometry. Integrated analysis of metabolomic and transcriptomic measurements showed that NAD levels and production were globally downregulated in Tg26 mouse kidneys, especially nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme in the NAD salvage pathway. Furthermore, NAD-dependent deacetylase sirtuin3 activity and mitochondrial oxidative phosphorylation activity were lower in ex vivo proximal tubules from Tg26 mouse kidneys compared with those of WT mice. Restoration of NAD levels in the kidney improved these abnormalities. These data suggest that NAD deficiency might be a treatable target for HIVAN.NEW & NOTEWORTHY The study describes a novel investigation that identified nicotinamide adenine dinucleotide (NAD) deficiency in a widely used HIV-associated nephropathy (HIVAN) transgenic mouse model. We show that INT-747, a farnesoid X receptor agonist, and nicotinamide riboside (NR), a precursor of nicotinamide, each ameliorated HIVAN tubulopathy. Multiomic analysis of mouse kidneys revealed that NAD deficiency was an upstream metabolomic mechanism contributing to HIVAN tubulopathy.

NAD+ metabolism and therapeutic strategies in cardiovascular diseases

Nicotinamide adenine dinucleotide (NAD+) is a central and pleiotropic metabolite involved in cellular energy metabolism, cell signaling, DNA repair, and protein modifications. Cardiovascular diseases (CVDs) are the leading cause of death worldwide. Metabolic stress and aging directly affect the cardiovascular system. Compelling data suggest that NAD + levels decrease with age, obesity, and hypertension, which are all notable risk factors for CVD. In addition, the therapeutic elevation of NAD + levels reduces chronic low-grade inflammation, reactivates autophagy and mitochondrial biogenesis, and enhances oxidative metabolism in vascular cells of humans and rodents with vascular disorders. In preclinical models, NAD + boosting can also expand the health span, prevent metabolic syndrome, and decrease blood pressure. Moreover, NAD + storage by genetic, pharmacological, or natural dietary NAD + -increasing strategies has recently been shown to be effective in improving the pathophysiology of cardiac and vascular health in different animal models, and human health. Here, we review and discuss NAD + -related mechanisms pivotal for vascular health and summarize recent experimental evidence in NAD + research directly related to vascular disease, including atherosclerosis, and coronary artery disease. Finally, we comparatively assess distinct NAD + precursors for their clinical efficacy and the efficiency of NAD + elevation in the treatment of major CVD. These findings may provide ideas for new therapeutic strategies to prevent and treat CVD in the clinic.

Smart RNA Sequencing Reveals the Toxicological Effects of Diisobutyl Phthalate (DiBP) in Porcine Oocytes

Diisobutyl phthalate (DiBP) is commonly used in the plastics industry, and recent studies have shown that environmental exposure and accumulation in the food chain caused inflammation in some organs. However, the underlying mechanisms by which DiBP affects oocyte quality have not yet been fully defined. We used immunostaining and fluorescence to evaluate the effects of DiBP exposure and demonstrated that it impaired the morphology of matured porcine oocytes through generation of cytoplasmic fragmentation, accompanied by the perturbed dynamics of the spindle and actin cytoskeleton, misdistributed endoplasmic reticulum, as well as partial exocytosis of cortical granules and ovastacin. Moreover, analysis of Smart RNA-seq found that DiBP-induced aberrant oocyte maturation could be induced by abnormal mitochondrial function and apoptosis. Importantly, we discovered that supplementation with pyrroloquinoline quinone (PQQ) significantly attenuated the meiotic abnormalities induced by DiBP exposure through the modulation of reactive oxygen species levels. Our findings demonstrated that DiBP exposure adversely affects oocyte meiotic maturation and that PQQ supplementation was an effective strategy to protect oocyte quality against DiBP exposure.

Fueling the success of transplantation through nutrition: recent insights into nutritional interventions, their interplay with gut microbiota and cellular mechanisms

PURPOSE OF REVIEW

The role of nutrition in organ health including solid organ transplantation is broadly accepted, but robust data on nutritional regimens remains scarce calling for further investigation of specific dietary approaches at the different stages of organ transplantation. This review gives an update on the latest insights into nutritional interventions highlighting the potential of specific dietary regimens prior to transplantation aiming for organ protection and the interplay between dietary intake and gut microbiota.

RECENT FINDINGS

Nutrition holds the potential to optimize patients' health prior to and after surgery, it may enhance patients' ability to cope with the procedure-associated stress and it may accelerate their recovery from surgery. Nutrition helps to reduce morbidity and mortality in addition to preserve graft function. In the case of living organ donation, dietary preconditioning strategies promise novel approaches to limit ischemic organ damage during transplantation and to identify the underlying molecular mechanisms of diet-induced organ protection. Functioning gut microbiota are required to limit systemic inflammation and to generate protective metabolites such as short-chain fatty acids or hydrogen sulfide.

SUMMARY

Nutritional intervention is a promising therapeutic concept including the pre- and rehabilitation stage in order to improve the recipients' outcome after solid organ transplantation.

Dissemination of pathogenic bacteria is reinforced by a MARTX toxin effector duet

Multiple bacterial genera take advantage of the multifunctional autoprocessing repeats-in-toxin (MARTX) toxin to invade host cells. Secretion of the MARTX toxin by Vibrio vulnificus, a deadly opportunistic pathogen that causes primary septicemia, the precursor of sepsis, is a major driver of infection; however, the molecular mechanism via which the toxin contributes to septicemia remains unclear. Here, we report the crystal and cryo-electron microscopy (EM) structures of a toxin effector duet comprising the domain of unknown function in the first position (DUF1)/Rho inactivation domain (RID) complexed with human targets. These structures reveal how the duet is used by bacteria as a potent weapon. The data show that DUF1 acts as a RID-dependent transforming NADase domain (RDTND) that disrupts NAD+ homeostasis by hijacking calmodulin. The cryo-EM structure of the RDTND-RID duet complexed with calmodulin and Rac1, together with immunological analyses in vitro and in mice, provide mechanistic insight into how V. vulnificus uses the duet to suppress ROS generation by depleting NAD(P)+ and modifying Rac1 in a mutually-reinforcing manner that ultimately paralyzes first line immune responses, promotes dissemination of invaders, and induces sepsis. These data may allow development of tools or strategies to combat MARTX toxin-related human diseases.

Synergistic susceptibility to environmental lead toxicity in chronic kidney disease

PURPOSE OF REVIEW

While high levels of lead exposure, as occurs accidentally or occupationally, can cause toxicity across multiple organ systems, the hazard of commonly encountered levels of lead in the environment remains unresolved. Challenges to researching the health effects of lead include its complex interplay with renal function, rendering analyses at risk of unaccounted confounding, and the likely small effect size of environmental levels of exposure. While children are known to be disproportionately susceptible to lead toxicity, resulting in appropriately more stringent regulatory surveillance for those under 5 years old, emerging evidence suggests that those with chronic kidney disease (CKD) similarly are at a greater risk. This review summarizes the role of environmental lead toxicity as a potential cause and consequence of CKD.

RECENT FINDINGS

Whether environmental lead exposure causes CKD remains debatable, with little recent research advancing the conflicting, mostly cross-sectional, analyses from years ago. However, an emerging body of evidence suggests that CKD increases the susceptibility to lead toxicity. Higher circulating lead levels and lower urinary excretion result in greater lead accumulation in CKD, with simultaneous greater risk of clinically meaningful disease. Recent studies suggest that levels of lead found commonly in the United States drinking water supply, and currently permissible by the Environmental Protection Agency, associate with hematologic toxicity in those with advanced CKD. Whether environmental lead contamination may have additional negative health impact among this at-risk population, including cardiovascular and neurocognitive disease, warrants further study.

SUMMARY

The underlying pathophysiology of kidney disease synergizes the susceptibility to environmental lead toxicity for those with CKD. Low levels of exposure, as found commonly in the United States water supply, may have adverse health impact in CKD. Further research will be needed to determine if more stringent environmental regulations are warranted to protect the health of all.

Ameliorating Mitochondrial Dysfunction for the Therapy of Parkinson's Disease

Parkinson's disease (PD) is currently the second most incurable central neurodegenerative disease resulting from various pathogenesis. As the "energy factory" of cells, mitochondria play an extremely important role in supporting neuronal signal transmission and other physiological activities. Mitochondrial dysfunction can cause and accelerate the occurrence and progression of PD. How to effectively prevent and suppress mitochondrial disorders is a key strategy for the treatment of PD from the root. Therefore, the emerging mitochondria-targeted therapy has attracted considerable interest. Herein, the relationship between mitochondrial dysfunction and PD, the causes and results of mitochondrial dysfunction, and major strategies for ameliorating mitochondrial dysfunction to treat PD are systematically reviewed. The study also prospects the main challenges for the treatment of PD.

Tubular insulin-induced gene 1 deficiency promotes NAD+ consumption and exacerbates kidney fibrosis

Profibrotic proximal tubules (PT) were identified as a unique phenotype of proximal tubule cells (PTCs) in renal fibrosis by single-cell RNA sequencing (scRNA-seq). Controlling the process of renal fibrosis requires understanding how to manage the S1 subset's branch to the S3 subset rather than to the profibrotic PT subset. Insulin-induced gene 1 (Insig1) is one of the branch-dependent genes involved in controlling this process, although its role in renal fibrosis is unknown. Here, we discovered that tubular Insig1 deficiency, rather than fibroblast Insig1 deficiency, plays a detrimental role in the pathogenesis of renal fibrosis in vivo and in vitro. Overexpression of Insig1 profoundly inhibited renal fibrosis. Mechanistically, Insig1 deletion in PTCs boosted SREBP1 nuclear localization, increasing Aldh1a1 transcriptional activity, causing excessive NAD+ consumption and ER enlargement, as well as accelerating renal fibrosis. We also identified nicardipine as a selective inhibitor of Aldh1a1, which could restore NAD+ and maintain ER homeostasis, as well as improve renal fibrosis. Together, our findings support tubular Insig1 as a new therapeutic target for chronic kidney disease (CKD).

Lysine and salt-sensitive hypertension

PURPOSE OF REVIEW

Salt-sensitive (SS) hypertension and its associated kidney damage have been extensively studied, yet proper therapeutic strategies are lacking. The interest in altering the metabolome to affect renal and cardiovascular disease has been emerging. Here, we discuss the effect and potential mechanism behind the protective effect of lysine, an essential amino acid, on the progression of SS hypertension.

RECENT FINDINGS

We have recently demonstrated that administering lysine in an SS rodent model can control the progression of hypertension. Both the animal and pilot human studies showed that lysine can efficiently inhibit tubular reabsorption of albumin and protect the kidneys from further damage. In addition, we conducted multilevel omics studies that showed increased lysine conjugation and excretion, leading to the depletion of harmful metabolites and an increase in useful ones.

SUMMARY

Lysine's twofold action involves both mechanically flushing protein from proximal tubules to shield the kidneys and initiating metabolic adaptations in the kidneys. This results in a net positive impact on SS hypertension. While further research is necessary to apply the current findings in clinical settings, this study offers some evidence suggesting that lysine supplementation holds promise as a therapeutic approach for hypertensive kidney disease.

Utilizing pathophysiological concepts of ischemia-reperfusion injury to design renoprotective strategies and therapeutic interventions for normothermic ex vivo kidney perfusion

Normothermic machine perfusion (NMP) has emerged as a promising tool for the preservation, viability assessment, and repair of deceased-donor kidneys prior to transplantation. These kidneys inevitably experience a period of ischemia during donation, which leads to ischemia-reperfusion injury when NMP is subsequently commenced. Ischemia-reperfusion injury has a major impact on the renal vasculature, metabolism, oxygenation, electrolyte balance, and acid-base homeostasis. With an increased understanding of the underlying pathophysiological mechanisms, renoprotective strategies and therapeutic interventions can be devised to minimize additional injury during normothermic reperfusion, ensure the safe implementation of NMP, and improve kidney quality. This review discusses the pathophysiological alterations in the vasculature, metabolism, oxygenation, electrolyte balance, and acid-base homeostasis of deceased-donor kidneys and delineates renoprotective strategies and therapeutic interventions to mitigate renal injury and improve kidney quality during NMP.

Ultrasmall Polyphenol-NAD+ Nanoparticle-Mediated Renal Delivery for Mitochondrial Repair and Anti-Inflammatory Treatment of AKI-to-CKD Progression

As a central metabolic molecule, nicotinamide adenine dinucleotide (NAD+) can potentially treat acute kidney injury (AKI) and chronic kidney disease (CKD); however, its bioavailability is poor due to short half-life, instability, the deficiency of targeting, and difficulties in transmembrane transport. Here a physiologically adaptive gallic acid-NAD+ nanoparticle is designed, which has ultrasmall size and pH-responsiveness, passes through the glomerular filtration membrane to reach injured renal tubules, and efficiently delivers NAD+ into the kidneys. With an effective accumulation in the kidneys, it restores renal function, immune microenvironment homeostasis, and mitochondrial homeostasis of AKI mice via the NAD+-Sirtuin-1 axis, and exerts strong antifibrotic effects on the AKI-to-CKD transition by inhibiting TGF-β signaling. It also exhibits excellent stability, biodegradable, and biocompatible properties, ensuring its long-term safety, practicality, and clinical translational feasibility. The present study shows a potential modality of mitochondrial repair and immunomodulation through nanoagents for the efficient and safe treatment of AKI and CKD.

A novel marine-derived anti-acute kidney injury agent targeting peroxiredoxin 1 and its nanodelivery strategy based on ADME optimization

Insufficient therapeutic strategies for acute kidney injury (AKI) necessitate precision therapy targeting its pathogenesis. This study reveals the new mechanism of the marine-derived anti-AKI agent, piericidin glycoside S14, targeting peroxiredoxin 1 (PRDX1). By binding to Cys83 of PRDX1 and augmenting its peroxidase activity, S14 alleviates kidney injury efficiently in Prdx1-overexpression (Prdx1-OE) mice. Besides, S14 also increases PRDX1 nuclear translocation and directly activates the Nrf2/HO-1/NQO1 pathway to inhibit ROS production. Due to the limited druggability of S14 with low bioavailability (2.6%) and poor renal distribution, a pH-sensitive kidney-targeting dodecanamine-chitosan nanoparticle system is constructed to load S14 for precise treatment of AKI. l-Serine conjugation to chitosan imparts specificity to kidney injury molecule-1 (Kim-1)-overexpressed cells. The developed S14-nanodrug exhibits higher therapeutic efficiency by improving the in vivo behavior of S14 significantly. By encapsulation with micelles, the AUC0‒t , half-life time, and renal distribution of S14 increase 2.5-, 1.8-, and 3.1-fold, respectively. The main factors contributing to the improved druggability of S14 nanodrugs include the lower metabolic elimination rate and UDP-glycosyltransferase (UGT)-mediated biotransformation. In summary, this study identifies a new therapeutic target for the marine-derived anti-AKI agent while enhancing its ADME properties and druggability through nanotechnology, thereby driving advancements in marine drug development for AKI.

Derangement in Nicotinamide Adenine Dinucleotide Metabolism is Observed During Acute Kidney Injury Among Male Agricultural Workers at Risk for Mesoamerican Nephropathy

Introduction

Mesoamerican nephropathy (MeN) is a chronic kidney disease (CKD) which may be caused by recurrent acute kidney injury (AKI). We investigated urinary quinolinate-to-tryptophan ratio (Q/T), a validated marker of nicotinamide adenine dinucleotide (NAD+) biosynthesis that is elevated during ischemic and inflammatory AKI, in a sugarcane worker population in Nicaragua with high rates of MeN.

Methods

Among 693 male sugarcane workers studied, we identified 45 who developed AKI during the harvest season. We matched them 1:1 based on age and job category with 2 comparison groups: (i) "no kidney injury," active sugarcane workers with serum creatinine (sCr) <1.1 mg/dl; and (ii) "CKD," individuals no longer working in sugarcane due to their CKD, who had additional 1:1 matching for sCr. We measured urine metabolites using liquid chromatography coupled tandem mass spectrometry (LC-MS/MS) and compared Q/T and other metabolic features between the AKI and comparison groups.

Results

Urine Q/T was significantly higher in workers with AKI than in those with no kidney injury (median interquartile Range [IQR]: 0.104 [0.074-0.167] vs. 0.060 [0.045-0.091], P < 0.0001) and marginally higher than in workers with CKD (0.086 [0.063-0.142], P = 0.059). Urine levels of the NAD+ precursor nicotinamide were lower in the AKI group than in comparison groups.

Conclusion

Workers at risk for MeN who develop AKI demonstrate features of impaired NAD+ biosynthesis, thereby providing new insights into the metabolic mechanisms of injury in this population. Therapeutic use of oral nicotinamide, which may ameliorate NAD+ biosynthetic derangement and fortify against kidney injury, should be investigated to prevent AKI in this setting.

The Role of Mitochondrial Sirtuins (SIRT3, SIRT4 and SIRT5) in Renal Cell Metabolism: Implication for Kidney Diseases

Kidney diseases, including chronic kidney disease (CKD), diabetic nephropathy, and acute kidney injury (AKI), represent a significant global health burden. The kidneys are metabolically very active organs demanding a large amount of ATP. They are composed of highly specialized cell types in the glomerulus and subsequent tubular compartments which fine-tune metabolism to meet their numerous and diverse functions. Defective renal cell metabolism, including altered fatty acid oxidation or glycolysis, has been linked to both AKI and CKD. Mitochondria play a vital role in renal metabolism, and emerging research has identified mitochondrial sirtuins (SIRT3, SIRT4 and SIRT5) as key regulators of renal cell metabolic adaptation, especially SIRT3. Sirtuins belong to an evolutionarily conserved family of mainly NAD+-dependent deacetylases, deacylases, and ADP-ribosyl transferases. Their dependence on NAD+, used as a co-substrate, directly links their enzymatic activity to the metabolic status of the cell. In the kidney, SIRT3 has been described to play crucial roles in the regulation of mitochondrial function, and the antioxidative and antifibrotic response. SIRT3 has been found to be constantly downregulated in renal diseases. Genetic or pharmacologic upregulation of SIRT3 has also been associated with beneficial renal outcomes. Importantly, experimental pieces of evidence suggest that SIRT3 may act as an important energy sensor in renal cells by regulating the activity of key enzymes involved in metabolic adaptation. Activation of SIRT3 may thus represent an interesting strategy to ameliorate renal cell energetics. In this review, we discuss the roles of SIRT3 in lipid and glucose metabolism and in mediating a metabolic switch in a physiological and pathological context. Moreover, we highlight the emerging significance of other mitochondrial sirtuins, SIRT4 and SIRT5, in renal metabolism. Understanding the role of mitochondrial sirtuins in kidney diseases may also open new avenues for innovative and efficient therapeutic interventions and ultimately improve the management of renal injuries.

Mini-encyclopedia of mitochondria-relevant nutraceuticals protecting health in primary and secondary care-clinically relevant 3PM innovation

Despite their subordination in humans, to a great extent, mitochondria maintain their independent status but tightly cooperate with the "host" on protecting the joint life quality and minimizing health risks. Under oxidative stress conditions, healthy mitochondria promptly increase mitophagy level to remove damaged "fellows" rejuvenating the mitochondrial population and sending fragments of mtDNA as SOS signals to all systems in the human body. As long as metabolic pathways are under systemic control and well-concerted together, adaptive mechanisms become triggered increasing systemic protection, activating antioxidant defense and repair machinery. Contextually, all attributes of mitochondrial patho-/physiology are instrumental for predictive medical approach and cost-effective treatments tailored to individualized patient profiles in primary (to protect vulnerable individuals again the health-to-disease transition) and secondary (to protect affected individuals again disease progression) care. Nutraceuticals are naturally occurring bioactive compounds demonstrating health-promoting, illness-preventing, and other health-related benefits. Keeping in mind health-promoting properties of nutraceuticals along with their great therapeutic potential and safety profile, there is a permanently growing demand on the application of mitochondria-relevant nutraceuticals. Application of nutraceuticals is beneficial only if meeting needs at individual level. Therefore, health risk assessment and creation of individualized patient profiles are of pivotal importance followed by adapted nutraceutical sets meeting individual needs. Based on the scientific evidence available for mitochondria-relevant nutraceuticals, this article presents examples of frequent medical conditions, which require protective measures targeted on mitochondria as a holistic approach following advanced concepts of predictive, preventive, and personalized medicine (PPPM/3PM) in primary and secondary care.

Cardiac Surgery-Associated Acute Kidney Injury

AKI is a common and serious complication of cardiac surgery that has a significant impact on patient morbidity and mortality. The Kidney Disease Improving Global Outcomes definition of AKI is widely used to classify and identify AKI associated with cardiac surgery (cardiac surgery-associated AKI [CSA-AKI]) on the basis of changes in serum creatinine and/or urine output. There are various preoperative, intraoperative, and postoperative risk factors for the development of CSA-AKI which should be recognized and addressed as early as possible to expedite its diagnosis, reduce its occurrence, and prevent or ameliorate its devastating complications. Crucial issues are the inaccuracy of serum creatinine as a surrogate parameter of kidney function in the perioperative setting of cardiothoracic surgery and the necessity to discover more representative markers of the pathophysiology of AKI. However, except for the tissue inhibitor of metalloproteinase-2 and insulin-like growth factor binding protein 7 ratio, other diagnostic biomarkers with an acceptable sensitivity and specificity are still lacking. This article provides a comprehensive review of various aspects of CSA-AKI, including pathogenesis, risk factors, diagnosis, biomarkers, classification, prevention, and treatment management.

The role of Testis-Specific Protein Y-encoded-Like 2 in kidney injury

Renal ischemia-reperfusion injury (IRI) is a major cause of acute kidney injury (AKI). Recent findings suggest that Testis-Specific Protein Y-encoded-Like 2 (TSPYL2) plays a fibrogenic role in diabetes-associated renal injury. However, the role of TSPYL2 in IRI-induced kidney damage is not entirely clear. In this study, we found that the expression of TSPYL2 was upregulated in a mouse model of AKI and in the hypoxia/reoxygenation (H/R) cell model. Knockdown of TSPYL2 attenuated kidney injury after IRI. More specifically, the knockdown of TSPYL2 or aminocarboxymuconate-semialdehyde decarboxylase (ACMSD) alleviated renal IRI-induced mitochondrial dysfunction and oxidative stress in vitro and in vivo. Further investigation showed that TSPYL2 regulated SREBP-2 acetylation by inhibiting SIRT1 and promoting p300 activity, thereby promoting the transcriptional activity of ACMSD. In conclusion, TSPYL2 was identified as a pivotal regulator of IRI-induced kidney damage by activating ACMSD, which may lead to NAD+ content and the damaging response in the kidney.

Kynurenine 3-monooxygenase limits de novo NAD+ synthesis through dietary tryptophan in renal proximal tubule epithelial cell models

Nicotinamide adenine dinucleotide (NAD+) is a pivotal coenzyme, essential for cellular reactions, metabolism, and mitochondrial function. Depletion of kidney NAD+ levels and reduced de novo NAD+ synthesis through the tryptophan-kynurenine pathway are linked to acute kidney injury (AKI), whereas augmenting NAD+ shows promise in reducing AKI. We investigated de novo NAD+ biosynthesis using in vitro, ex vivo, and in vivo models to understand its role in AKI. Two-dimensional (2-D) cultures of human primary renal proximal tubule epithelial cells (RPTECs) and HK-2 cells showed limited de novo NAD+ synthesis, likely due to low pathway enzyme gene expression. Using three-dimensional (3-D) spheroid culture model improved the expression of tubular-specific markers and enzymes involved in de novo NAD+ synthesis. However, de novo NAD+ synthesis remained elusive in the 3-D spheroid culture, regardless of injury conditions. Further investigation revealed that 3-D cultured cells could not metabolize tryptophan (Trp) beyond kynurenine (KYN). Intriguingly, supplementation of 3-hydroxyanthranilic acid into RPTEC spheroids was readily incorporated into NAD+. In a human precision-cut kidney slice (PCKS) ex vivo model, de novo NAD+ synthesis was limited due to substantially downregulated kynurenine 3-monooxygenase (KMO), which is responsible for KYN to 3-hydroxykynurenine conversion. KMO overexpression in RPTEC 3-D spheroids successfully reinstated de novo NAD+ synthesis from Trp. In addition, in vivo study demonstrated that de novo NAD+ synthesis is intact in the kidney of the healthy adult mice. Our findings highlight disrupted tryptophan-kynurenine NAD+ synthesis in in vitro cellular models and an ex vivo kidney model, primarily attributed to KMO downregulation.NEW & NOTEWORTHY Nicotinamide adenine dinucleotide (NAD+) is essential in regulating mitochondrial function. Reduced NAD+ synthesis through the de novo pathway is associated with acute kidney injury (AKI). Our study reveals a disruption in de novo NAD+ synthesis in proximal tubular models, but not in vivo, attributed to downregulation of enzyme kynurenine 3-monooxygenase (KMO). These findings highlight a crucial role of KMO in governing de novo NAD+ biosynthesis within the kidney, shedding light on potential AKI interventions.

The role of mitophagy in the development of chronic kidney disease

Chronic kidney disease (CKD) represents a significant global health concern, with renal fibrosis emerging as a prevalent and ultimate manifestation of this condition. The absence of targeted therapies presents an ongoing and substantial challenge. Accumulating evidence suggests that the integrity and functionality of mitochondria within renal tubular epithelial cells (RTECs) often become compromised during CKD development, playing a pivotal role in the progression of renal fibrosis. Mitophagy, a specific form of autophagy, assumes responsibility for eliminating damaged mitochondria to uphold mitochondrial equilibrium. Dysregulated mitophagy not only correlates with disrupted mitochondrial dynamics but also contributes to the advancement of renal fibrosis in CKD. While numerous studies have examined mitochondrial metabolism, ROS (reactive oxygen species) production, inflammation, and apoptosis in kidney diseases, the precise pathogenic mechanisms underlying mitophagy in CKD remain elusive. The exact mechanisms through which modulating mitophagy mitigates renal fibrosis, as well as its influence on CKD progression and prognosis, have not undergone systematic investigation. The role of mitophagy in AKI has been relatively clear, but the role of mitophagy in CKD is still rare. This article presents a comprehensive review of the current state of research on regulating mitophagy as a potential treatment for CKD. The objective is to provide fresh perspectives, viable strategies, and practical insights into CKD therapy, thereby contributing to the enhancement of human living conditions and patient well-being.

Molecular mechanism of NAD+ and NMN binding to the Nudix homology domains of DBC1

Deleted in breast cancer 1 (DBC1) is a human nuclear protein that modulates the activities of various proteins involved in cell survival and cancer progression. Oxidized form of nicotinamide adenine dinucleotide (NAD+) is suggested to bind to the Nudix homology domains (NHDs) of DBC1, thereby regulating DBC1-Poly (ADP-ribose) polymerase 1 (PARP1) interactions, resulting in the restoration of DNA repair. Using Nuclear Magnetic Resonance (NMR) and Isothermal Titration Calorimetry (ITC), we confirmed NAD+ and its precursor nicotinamide mononucleotide (NMN) both bind the NHD domain of DBC1 (DBC1354-396). NAD+ likely interacts with DBC1354-396 through hydrogen bonding, with a binding affinity (8.99 μM) nearly twice that of NMN (17.0 μM), and the key binding sites are primarily residues E363 and D372, in the agreement with Molecular Docking experiments. Molecular Dynamics (MD) simulation further demonstrated E363 and D372's anchoring role in the binding process. Additional mutagenesis experiments of E363 and D372 confirmed their critical involvement of ligand-protein interactions. These findings lead to a better understanding of how NAD+ and NMN regulate DBC1, thereby offering insights for the development of targeted therapies and drug research focused on DBC1-associated tumors.

Exposures to drinking water disinfection byproducts and kidney function in Chinese women

BACKGROUND

Disinfection byproducts (DBPs), the ubiquitous contaminants in drinking water, have been shown to impair renal function in experimental studies. However, epidemiological evidence is sparse.

OBJECTIVE

To investigate exposures to DBPs in associations with renal function among women.

METHODS

A total of 920 women from December 2018 to January 2020 were abstracted from the Tongji Reproductive and Environmental (TREE) Study, an ongoing cohort study in Wuhan, China. Urine samples were gathered at baseline recruitment and analyzed for dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) as biomarkers of DBP exposures. Serum uric acid (UA), creatinine, and estimated glomerular filtration rate (eGFR) were measured as indicators of renal function. Multivariate linear regression and restricted cubic spline (RCS) models were conducted to assess urinary DCAA and TCAA concentrations in associations with renal function indicators. Stratified analyses by age and body mass index (BMI) were also performed.

RESULTS

We found null evidence of urinary TCAA in associations with renal function indicators. However, elevated urinary DCAA tertiles were related to decreased eGFR (β = -1.78%, 95% CI: 3.21%, -0.36%, comparing the upper vs. lower tertile; P for trend = 0.01). This inverse association still existed when urinary DCAA concentration was treated as a continuous variable, and the dose-response relationship was linear based on the RCS model (P for overall association = 0.002 and P for non-linear associations = 0.44). In the stratified analyses, we found an association of urinary DCAA concentration with decreased UA level among women <30 years but an association with increased UA level among women ≥30 years (P for interaction = 0.04).

CONCLUSION

Urinary DCAA but not TCAA was associated with impaired renal function among women undergoing assisted reproductive technology.

Nicotinamide riboside activates renal metabolism and protects the kidney in a model of Alport syndrome

Chronic kidney disease (CKD) is associated with renal metabolic disturbances, including impaired fatty acid oxidation (FAO). Nicotinamide adenine dinucleotide (NAD + ) is a small molecule that participates in hundreds of metabolism-related reactions. NAD + levels are decreased in CKD, and NAD + supplementation is protective. However, both the mechanism of how NAD + supplementation protects from CKD, as well as the cell types most responsible, are poorly understood. Using a mouse model of Alport syndrome, we show that nicotinamide riboside (NR), an NAD + precursor, stimulates renal peroxisome proliferator-activated receptor α signaling and restores FAO in the proximal tubules, thereby protecting from CKD in both sexes. Bulk RNA-sequencing shows that renal metabolic pathways are impaired in Alport mice and dramatically activated by NR in both sexes. These transcriptional changes are confirmed by orthogonal imaging techniques and biochemical assays. Single nuclei RNA-sequencing and spatial transcriptomics, both the first of their kind from Alport mice, show that NAD + supplementation restores FAO in the proximal tubules with minimal effects on the podocytes. Finally, we also report, for the first time, sex differences at the transcriptional level in this Alport model. Male Alport mice had more severe inflammation and fibrosis than female mice at the transcriptional level. In summary, the data herein identify both the protective mechanism and location of NAD + supplementation in this model of CKD.

Transient inhibition of sodium-glucose cotransporter 2 after ischemia/reperfusion injury ameliorates chronic kidney disease

Sodium-glucose cotransporter 2 (SGLT2) inhibitor, dapagliflozin (Dapa), exhibited nephroprotective effects in patients with chronic kidney disease (CKD). We assessed the efficacy of short-term Dapa administration following acute kidney injury (AKI) in preventing CKD. Male Wistar rats were randomly assigned to Sham surgery, bilateral ischemia for 30 minutes (abbreviated as IR), and IR + Dapa groups. Daily treatment with Dapa was initiated just 24 hours after IR and maintained for only 10 days. Initially, rats were euthanized at this point to study early renal repair. After severe AKI, Dapa promptly restored creatinine clearance (CrCl) and significantly reduced renal vascular resistance compared with the IR group. Furthermore, Dapa effectively reversed the mitochondrial abnormalities, including increased fission, altered mitophagy, metabolic dysfunction, and proapoptotic signaling. To study this earlier, another set of rats was studied just 5 days after AKI. Despite persistent renal dysfunction, our data reveal a degree of mitochondrial protection. Remarkably, a 10-day treatment with Dapa demonstrated effectiveness in preventing CKD transition in an independent cohort monitored for 5 months after AKI. This was evidenced by improvements in proteinuria, CrCl, glomerulosclerosis, and fibrosis. Our findings underscore the potential of Dapa in preventing maladaptive repair following AKI, emphasizing the crucial role of early intervention in mitigating AKI long-term consequences.

Sirtuins in kidney diseases: potential mechanism and therapeutic targets

Sirtuins, which are NAD+-dependent class III histone deacetylases, are involved in various biological processes, including DNA damage repair, immune inflammation, oxidative stress, mitochondrial homeostasis, autophagy, and apoptosis. Sirtuins are essential regulators of cellular function and organismal health. Increasing evidence suggests that the development of age-related diseases, including kidney diseases, is associated with aberrant expression of sirtuins, and that regulation of sirtuins expression and activity can effectively improve kidney function and delay the progression of kidney disease. In this review, we summarise current studies highlighting the role of sirtuins in renal diseases. First, we discuss sirtuin family members and their main mechanisms of action. We then outline the possible roles of sirtuins in various cell types in kidney diseases. Finally, we summarise the compounds that activate or inhibit sirtuin activity and that consequently ameliorate renal diseases. In conclusion, targeted modulation of sirtuins is a potential therapeutic strategy for kidney diseases. Video Abstract.

Mitochondrial metabolism and targeted treatment strategies in ischemic-induced acute kidney injury

Ischemia-reperfusion injury (IRI) is a common cause of acute kidney injury (AKI). The kidney is susceptible to IRI under several clinical conditions, including hypotension, sepsis, and surgical procedures, such as partial nephrectomy and kidney transplantation. Extensive research has been conducted on the mechanism and intervention strategies of renal IRI in past decades; however, the complex pathophysiology of IRI-induced AKI (IRI-AKI) is not fully understood, and there remains a lack of effective treatments for AKI. Renal IRI involves several processes, including reactive oxygen species (ROS) production, inflammation, and apoptosis. Mitochondria, the centers of energy metabolism, are increasingly recognized as substantial contributors to the early phases of IRI. Multiple mitochondrial lesions have been observed in the renal tubular epithelial cells (TECs) of IRI-AKI mice, and damaged or dysfunctional mitochondria are toxic to the cells because they produce ROS and release cell death factors, resulting in TEC apoptosis. In this review, we summarize the recent advances in the mitochondrial pathology in ischemic AKI and highlight promising therapeutic approaches targeting mitochondrial dysfunction to prevent or treat human ischemic AKI.

Optimized protocol for quantification of extracellular nicotinamide adenine dinucleotide: evaluating clinical parameters and pre-analytical factors for translational research

Nicotinamide adenine dinucleotide (NAD+), a coenzyme for more than 500 enzymes, plays a central role in energy production, metabolism, cellular signaling, and DNA repair. Until recently, NAD+ was primarily considered to be an intracellular molecule (iNAD+), however, its extracellular species (eNAD+) has recently been discovered and has since been associated with a multitude of pathological conditions. Therefore, accurate quantification of eNAD+ in bodily fluids such as plasma is paramount to answer important research questions. In order to create a clinically meaningful and reliable quantitation method, we analyzed the relationship of cell lysis, routine clinical laboratory parameters, blood collection techniques, and pre-analytical processing steps with measured plasma eNAD+ concentrations. Initially, NAD+ levels were assessed both intracellularly and extracellularly. Intriguingly, the concentration of eNAD+ in plasma was found to be approximately 500 times lower than iNAD+ in peripheral blood mononuclear cells (0.253 ± 0.02 μM vs. 131.8 ± 27.4 μM, p = 0.007, respectively). This stark contrast suggests that cellular damage or cell lysis could potentially affect the levels of eNAD+ in plasma. However, systemic lactate dehydrogenase in patient plasma, a marker of cell damage, did not significantly correlate with eNAD+ (n = 33; r = -0.397; p = 0.102). Furthermore, eNAD+ was negatively correlated with increasing c-reactive protein (CRP, n = 33; r = -0.451; p = 0.020), while eNAD+ was positively correlated with increasing hemoglobin (n = 33; r = 0.482; p = 0.005). Next, variations in blood drawing, sample handling and pre-analytical processes were examined. Sample storage durations at 4°C (0-120 min), temperature (0° to 25°C), cannula sizes for blood collection and tourniquet times (0 - 120 s) had no statistically significant effect on eNAD+ (p > 0.05). On the other hand, prolonged centrifugation (> 5 min) and a faster braking mode of the centrifuge rotor (< 4 min) resulted in a significant decrease in eNAD+ levels (p < 0.05). Taken together, CRP and hemoglobin appeared to be mildly correlated with eNAD+ levels whereas cell damage was not correlated significantly to eNAD+ levels. The blood drawing trial did not show any influence on eNAD+, in contrast, the preanalytical steps need to be standardized for accurate eNAD+ measurement. This work paves the way towards robust eNAD+ measurements, for use in future clinical and translational research, and provides an optimized hands-on protocol for reliable eNAD+ quantification in plasma.

NAD+ Protects against Hyperlipidemia-induced Kidney Injury in Apolipoprotein E-deficient Mice

Background: Hyperlipidemia is an independent risk factor for kidney injury. Several studies have shown that nicotinamide adenine dinucleotide (NAD+) is an important coenzyme involved in normal body metabolism. Therefore, this study aimed to investigate the possible protective effects of NAD+ against hyperlipidemia-induced kidney injury in apolipoprotein Edeficient (ApoE-/-) mice.

Methods: Twenty-five eight-week-old male ApoE-/- mice were randomly assigned into four groups: normal diet (ND), ND supplemented with NAD+ (ND+NAD+), high-fat diet (HFD), and HFD supplemented with NAD+ (HFD+NAD+). The mice were subjected to their respective diets for a duration of 16 weeks. Blood samples were obtained from the inferior vena cava, collected in serum tubes, and stored at -80°C until use. Kidney tissues was fixed in 10% formalin and then embedded in paraffin for histological evaluation. The remainder of the kidney tissues was snapfrozen in liquid nitrogen for Western blot analysis.

Results: Metabolic parameters (total cholesterol, triglycerides, low-density lipoprotein-cholesterol, creatinine, and blood urea nitrogen) were significantly higher in the HFD group compared to the other groups. Histological analysis revealed prominent pathological manifestations in the kidneys of the HFD group. The HFD+NAD+ group showed increased levels of oxidative stress markers (NRF2 and SOD2) and decreased levels of NOX4 compared to the HFD group. Furthermore, the HFD group exhibited higher levels of TGF-β, Smad3, Collagen I, Collagen III, Bax, and Bak compared to the other groups. NAD+ supplementation in the HFD+NAD+ group significantly increased the levels of SIRT3, HO-1, Bcl-2, and Bcl-xL compared to the HFD group. Additionally, NF-κB protein expression was higher in the HFD group than in the HFD+NAD+ group.

Conclusion: These findings demonstrated that NAD+ may hold potential as a clinical treatment for kidney injury caused by hyperlipidemia.

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Jian-Pi-Yi-Shen formula alleviates renal fibrosis by restoring NAD+ biosynthesis in vivo and in vitro

BACKGROUND

Patients with chronic kidney disease (CKD) lack efficacious treatment. Jian-Pi-Yi-Shen formula (JPYSF) has demonstrated significant clinical efficacy in treating CKD for decades. However, its renoprotective mechanism has not been fully elucidated. This study aimed to determine whether JPYSF could delay renal fibrosis progression in CKD by restoring nicotinamide adenine dinucleotide (NAD+) biosynthesis.

METHODS

Adenine-diet feeding was used to model CKD in C57BL/6 mice. JPYSF was orally administered for 4 weeks. Human proximal tubular epithelial cells (HK-2) cells were stimulated with transforming growth factor-β1 (TGF-β1) with or without JPYSF treatment. Renal function of mice was assessed by serum creatinine and blood urea nitrogen levels. Renal histopathological changes were assessed using Periodic acid-Schiff and Masson's trichrome staining. Cell viability was assessed using a cell counting kit-8 assay. NAD+ concentrations were detected by a NAD+/NADH assay kit. Western blotting, immunohistochemistry, and immunofluorescence were employed to examine fibrosis-related proteins and key NAD+ biosynthesis enzymes expression in the CKD kidney and TGF-β1-induced HK-2 cells.

RESULTS

JPYSF treatment could not only improve renal function and pathological injury but also inhibit renal fibrosis in CKD mice. Additionally, JPYSF reversed fibrotic response in TGF-β1-induced HK-2 cells. Moreover, JPYSF rescued the decreased NAD+ content in CKD mice and TGF-β1-induced HK-2 cells through restoring expression of key enzymes in NAD+ biosynthesis, including quinolinate phosphoribosyltransferase, nicotinamide mononucleotide adenylyltransferase 1, and nicotinamide riboside kinase 1.

CONCLUSIONS

JPYSF alleviated renal fibrosis in CKD mice and reversed fibrotic response in TGF-β1-induced HK-2 cells, which may be related to the restoration of NAD+ biosynthesis.

Impact of NAD+ metabolism on ovarian aging

Nicotinamide adenine dinucleotide (NAD+), a crucial coenzyme in cellular redox reactions, is closely associated with age-related functional degeneration and metabolic diseases. NAD exerts direct and indirect influences on many crucial cellular functions, including metabolic pathways, DNA repair, chromatin remodeling, cellular senescence, and immune cell functionality. These cellular processes and functions are essential for maintaining tissue and metabolic homeostasis, as well as healthy aging. Causality has been elucidated between a decline in NAD levels and multiple age-related diseases, which has been confirmed by various strategies aimed at increasing NAD levels in the preclinical setting. Ovarian aging is recognized as a natural process characterized by a decline in follicle number and function, resulting in decreased estrogen production and menopause. In this regard, it is necessary to address the many factors involved in this complicated procedure, which could improve fertility in women of advanced maternal age. Concerning the decrease in NAD+ levels as ovarian aging progresses, promising and exciting results are presented for strategies using NAD+ precursors to promote NAD+ biosynthesis, which could substantially improve oocyte quality and alleviate ovarian aging. Hence, to acquire further insights into NAD+ metabolism and biology, this review aims to probe the factors affecting ovarian aging, the characteristics of NAD+ precursors, and the current research status of NAD+ supplementation in ovarian aging. Specifically, by gaining a comprehensive understanding of these aspects, we are optimistic about the prominent progress that will be made in both research and therapy related to ovarian aging.

Hepatocyte nuclear factor 4α mediated quinolinate phosphoribosylltransferase (QPRT) expression in the kidney facilitates resilience against acute kidney injury

Nicotinamide adenine dinucleotide (NAD+) levels decline in experimental models of acute kidney injury (AKI). Attenuated enzymatic conversion of tryptophan to NAD+ in tubular epithelium may contribute to adverse cellular and physiological outcomes. Mechanisms underlying defense of tryptophan-dependent NAD+ production are incompletely understood. Here we show that regulation of a bottleneck enzyme in this pathway, quinolinate phosphoribosyltransferase (QPRT) may contribute to kidney resilience. Expression of QPRT declined in two unrelated models of AKI. Haploinsufficient mice developed worse outcomes compared to littermate controls whereas novel, conditional gain-of-function mice were protected from injury. Applying these findings, we then identified hepatocyte nuclear factor 4 alpha (HNF4α) as a candidate transcription factor regulating QPRT expression downstream of the mitochondrial biogenesis regulator and NAD+ biosynthesis inducer PPARgamma coactivator-1-alpha (PGC1α). This was verified by chromatin immunoprecipitation. A PGC1α - HNF4α -QPRT axis controlled NAD+ levels across cellular compartments and modulated cellular ATP. These results propose that tryptophan-dependent NAD+ biosynthesis via QPRT and induced by HNF4α may be a critical determinant of kidney resilience to noxious stressors.

Electrochromic Sensor Augmented with Machine Learning for Enzyme-Free Analysis of Antioxidants

Our study presents an electrochromic sensor that operates without the need for enzymes or multiple oxidant reagents. This sensor is augmented with machine learning algorithms, enabling the identification, classification, and prediction of six different antioxidants with high accuracy. We utilized polyaniline (PANI), Prussian blue (PB), and copper-Prussian blue analogues (Cu-PBA) at their respective oxidation states as electrochromic materials (ECMs). By designing three readout channels with these materials, we were able to achieve visual detection of antioxidants without relying on traditional "lock and key" specific interactions. Our sensing approach is based on the direct electrochemical reactions between oxidized electrochromic materials (ECMsox) as electron acceptors and various antioxidants, which act as electron donors. This interaction generates unique fingerprint patterns by switching the ECMsox to reduced electrochromic materials (ECMsred), causing their colors to change. Through the application of density functional theory (DFT), we demonstrated the molecular-level basis for the distinct multicolor patterns. Additionally, machine learning algorithms were employed to correlate the optical patterns with RGB data, enabling complex data analysis and the prediction of unknown samples. To demonstrate the practical applications of our design, we successfully used the EC sensor to diagnose antioxidants in serum samples, indicating its potential for the on-site monitoring of antioxidant-related diseases. This advancement holds promise for various applications, including the real-time monitoring of antioxidant levels in biological samples, the early diagnosis of antioxidant-related diseases, and personalized medicine. Furthermore, the success of our electrochromic sensor design highlights the potential for exploring similar strategies in the development of sensors for diverse analytes, showcasing the versatility and adaptability of this approach.

GLIS1 alleviates cell senescence and renal fibrosis through PGC1-α mediated mitochondrial quality control in kidney aging

Mitochondrial dysfunction is implied as a crucial factor in age-related chronic kidney disease. It is confirmed that Gli-like transcription factor 1 (GLIS1) is involved in age-related renal fibrosis, however, the correlation between mitochondrial disturbances and GLIS1-driven kidney aging are not clearly clarified. Thus, we investigated the regulatory mechanism of GLIS1 in the homeostasis of mitochondrial quality control both in vivo and in vitro. The lower expression of GLIS1 was identified in natural and accelerated kidney aged models, accompanied by the dysfunctions of mitochondrial quality control, including enhanced mitochondrial fission, reduced mitochondrial biogenesis and mitophagy, whereas, GLIS1 could maintain mitochondrial stability by interacting with peroxisome proliferator-activated receptor γ coactivator-1α (PGC1-α). Additionally, the over-expressed GLIS1 inhibited extracellular matrix accumulation and alleviated renal fibrosis while siGLIS1 inhibited PGC1-α transcription, as well as affecting its mitochondria-protective functions. Collectively, we demonstrated that GLIS1 mediated mitochondrial quality control through targeting PGC1-α in kidney aging, which might be a promising therapeutic target for attenuating cell senescence and age-related renal fibrosis.

Huangqi-Danshen decoction protects against cisplatin-induced acute kidney injury in mice

Background: Acute kidney injury (AKI) induced by cisplatin remains a major impediment to the clinical application of cisplatin, necessitating urgent exploration for promising solutions. Huangqi-Danshen decoction (HDD), a Chinese herbal preparation, has been shown by our group to have a reno-protective effect in adenine-induced chronic kidney disease mice and diabetic db/db mice. However, the effect of HDD on cisplatin-induced AKI and its underlying mechanisms are unknown. Methods: The AKI model was established by intraperitoneal injection of cisplatin (20 mg/kg) in C57BL/6 mice. The mice in the treatment group were administrated with HDD (6.8 g/kg/d) for 5 consecutive days before cisplatin challenge. After 72 h cisplatin injection, blood and kidney tissue were subsequently collected for biochemical detection, histopathological evaluation, Western blot analysis, immunohistochemical staining, and terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling assay. Ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry was used to detect changes in renal metabolites. Results: The results showed that HDD significantly reduced serum creatinine and blood urea nitrogen levels and alleviated renal histopathological injury in cisplatin-induced AKI mice. And HDD treatment demonstrated a significant inhibition in apoptosis, inflammation, and oxidative stress in AKI mice. Moreover, non-target metabolomics revealed that HDD significantly restored 165 altered metabolites in AKI mice. Subsequent enrichment analysis and pathway analysis of these metabolites indicated that nicotinate and nicotinamide metabolism was the primary pathway affected by HDD intervention. Further investigation showed that HDD could upregulate nicotinamide adenine dinucleotide (NAD+) biosynthesis-related enzymes quinolinate phosphoribosyltransferase, nicotinamide mononucleotide adenylyltransferase 1, and nicotinamide phosphoribosyltransferase to replenish NAD+ content in the kidney of AKI mice. Conclusion: In summary, HDD exerted a protective effect against cisplatin-induced AKI and suppressed apoptosis, inflammation, and oxidative stress in the kidney of AKI mice, which may be attributed to the modulation of NAD+ biosynthesis.

Inflammation primes the kidney for recovery by activating AZIN1 A-to-I editing

The progression of kidney disease varies among individuals, but a general methodology to quantify disease timelines is lacking. Particularly challenging is the task of determining the potential for recovery from acute kidney injury following various insults. Here, we report that quantitation of post-transcriptional adenosine-to-inosine (A-to-I) RNA editing offers a distinct genome-wide signature, enabling the delineation of disease trajectories in the kidney. A well-defined murine model of endotoxemia permitted the identification of the origin and extent of A-to-I editing, along with temporally discrete signatures of double-stranded RNA stress and Adenosine Deaminase isoform switching. We found that A-to-I editing of Antizyme Inhibitor 1 (AZIN1), a positive regulator of polyamine biosynthesis, serves as a particularly useful temporal landmark during endotoxemia. Our data indicate that AZIN1 A-to-I editing, triggered by preceding inflammation, primes the kidney and activates endogenous recovery mechanisms. By comparing genetically modified human cell lines and mice locked in either A-to-I edited or uneditable states, we uncovered that AZIN1 A-to-I editing not only enhances polyamine biosynthesis but also engages glycolysis and nicotinamide biosynthesis to drive the recovery phenotype. Our findings implicate that quantifying AZIN1 A-to-I editing could potentially identify individuals who have transitioned to an endogenous recovery phase. This phase would reflect their past inflammation and indicate their potential for future recovery.

Nicotinamide Adenine Dinucleotide in Aging Biology: Potential Applications and Many Unknowns

Recent research has unveiled an expansive role of NAD+ in cellular energy generation, redox reactions, and as a substrate or cosubstrate in signaling pathways that regulate health span and aging. This review provides a critical appraisal of the clinical pharmacology and the preclinical and clinical evidence for therapeutic effects of NAD+ precursors for age-related conditions, with a particular focus on cardiometabolic disorders, and discusses gaps in current knowledge. NAD+ levels decrease throughout life; age-related decline in NAD+ bioavailability has been postulated to be a contributor to many age-related diseases. Raising NAD+ levels in model organisms by administration of NAD+ precursors improves glucose and lipid metabolism; attenuates diet-induced weight gain, diabetes, diabetic kidney disease, and hepatic steatosis; reduces endothelial dysfunction; protects heart from ischemic injury; improves left ventricular function in models of heart failure; attenuates cerebrovascular and neurodegenerative disorders; and increases health span. Early human studies show that NAD+ levels can be raised safely in blood and some tissues by oral NAD+ precursors and suggest benefit in preventing nonmelanotic skin cancer, modestly reducing blood pressure and improving lipid profile in older adults with obesity or overweight; preventing kidney injury in at-risk patients; and suppressing inflammation in Parkinson disease and SARS-CoV-2 infection. Clinical pharmacology, metabolism, and therapeutic mechanisms of NAD+ precursors remain incompletely understood. We suggest that these early findings provide the rationale for adequately powered randomized trials to evaluate the efficacy of NAD+ augmentation as a therapeutic strategy to prevent and treat metabolic disorders and age-related conditions.

Protein acetylation and related potential therapeutic strategies in kidney disease

Kidney disease can be caused by various internal and external factors that have led to a continual increase in global deaths. Current treatment methods can alleviate but do not markedly prevent disease development. Further research on kidney disease has revealed the crucial function of epigenetics, especially acetylation, in the pathology and physiology of the kidney. Histone acetyltransferases (HATs), histone deacetylases (HDACs), and acetyllysine readers jointly regulate acetylation, thus affecting kidney physiological homoeostasis. Recent studies have shown that acetylation improves mechanisms and pathways involved in various types of nephropathy. The discovery and application of novel inhibitors and activators have further confirmed the important role of acetylation. In this review, we provide insights into the physiological process of acetylation and summarise its specific mechanisms and potential therapeutic effects on renal pathology.

N-methyl-2-pyridone-5-carboxamide (N-Me-2PY) has potent anti-fibrotic and anti-inflammatory activity in a fibrotic kidney model: is it an old uremic toxin?

BACKGROUND

Uremic toxins accumulate in renal tissues and cells due to chronic kidney disease (CKD). Abnormalities in nicotinamide adenine dinucleotide (NAD +) metabolism lead to the progression of CKD. NAD + metabolites, such as N-methyl-2-pyridone-5-carboxamide (N-Me-2PY) and N-methyl-4-pyridone-5-carboxamide (N-Me-4PY), have been recognized as uremic toxins. However, no reports have validated whether they are actually harmful to the body. Therefore, we focused on the structural similarity of these metabolites to the anti-fibrotic drug pirfenidone and evaluated their effects on renal fibrosis.

METHODS

Each NAD + metabolite was treated with TGFβ1 to kidney fibroblasts or tubular epithelial cells, and quantitative RT-PCR and Western blot analysis were conducted. N-Me-2PY was orally administered to a ligated murine kidney fibrosis model (UUO) to evaluate its anti-fibrotic and toxic effects on the body.

RESULTS

N-Me-2PY, N-Me-4PY, and nicotinamide N-oxide (NNO) inhibited TGFβ1-induced fibrosis and inflammatory gene expression in kidney fibroblasts. N-Me-2PY strongly suppressed the expression of types I and III collagen, αSMA, and IL-6. N-Me-2PY also suppressed TGFβ1-induced type I collagen and IL-6 expression in renal tubular epithelial cells. No toxic effect was observed with N-Me-2PY treatment, while attenuating renal fibrosis and tubular dilation in UUO mice. Suppression of various fibrosis- and inflammation-related genes was also observed. N-Me-2PY did not inhibit TGFβ1-induced Smad3 phosphorylation but inhibited Akt phosphorylation, suggesting that N-Me-2PY exerts anti-fibrotic and anti-inflammatory effects through Akt inhibition, similar to pirfenidone.

CONCLUSIONS

NAD + metabolites, such as N-Me-2PY, are not uremic toxins but are potential therapeutic agents that have anti-fibrotic effects in CKD.

NAD+ precursor nutritional supplements sensitize the brain to future ischemic events

Nicotinamide adenine dinucleotide (NAD+) is a redox cofactor critical for oxidative phosphorylation. Nicotinamide (NAM) and nicotinamide riboside (NR) are NAD+ precursors widely used as nutritional supplements to augment oxidative phosphorylation. Indeed, NAD+ precursors have been reported to improve outcomes in ischemic stroke when administered as a rescue therapy after stroke onset. However, we have also reported that enhanced reliance on oxidative phosphorylation before ischemia onset might worsen outcomes. To address the paradox, we examined how NAD+ precursors modulate the outcome of middle cerebral artery occlusion in mice, when administered either 20 minutes after reperfusion or daily for three days before ischemia onset. A single post-ischemic dose of NAM or NR indeed improved tissue and neurologic outcomes examined at 72 hours. In contrast, pre-ischemic treatment for three days enlarged the infarcts and worsened neurological deficits. As a possible explanation for the diametric outcomes, a single dose of NAM or NR augmented tissue AMPK, PGC1α, SIRT1, and ATP in both naïve and ischemic brains, while the multiple-dose paradigm failed to do so. Our data suggest that NAD+ precursor supplements may sensitize the brain to subsequent ischemic events, despite their neuroprotective effect when administered after ischemia onset.