CARM1 hypermethylates the NuRD chromatin remodeling complex to promote cell cycle gene expression and breast cancer development.

Protein arginine methyltransferase CARM1 has been shown to methylate a large number of non-histone proteins, and play important roles in gene transcriptional activation, cell cycle progress, and tumorigenesis. However, the critical substrates through which CARM1 exerts its functions remain to be fully characterized. Here, we reported that CARM1 directly interacts with the GATAD2A/2B subunit in the nucleosome remodeling and deacetylase (NuRD) complex, expanding the activities of NuRD to include protein arginine methylation. CARM1 and NuRD bind and activate a large cohort of genes with implications in cell cycle control to facilitate the G1 to S phase transition. This gene activation process requires CARM1 to hypermethylate GATAD2A/2B at a cluster of arginines, which is critical for the recruitment of the NuRD complex. The clinical significance of this gene activation mechanism is underscored by the high expression of CARM1 and NuRD in breast cancers, and the fact that knockdown CARM1 and NuRD inhibits cancer cell growth in vitro and tumorigenesis in vivo. Targeting CARM1-mediated GATAD2A/2B methylation with CARM1 specific inhibitors potently inhibit breast cancer cell growth in vitro and tumorigenesis in vivo. These findings reveal a gene activation program that requires arginine methylation established by CARM1 on a key chromatin remodeler, and targeting such methylation might represent a promising therapeutic avenue in the clinic.

Balanced Solution versus Normal Saline in Predicted Severe Acute Pancreatitis: A Stepped Wedge Cluster Randomized Trial.

OBJECTIVE: To compare the effect of balanced multielectrolyte solutions(BMES) versus normal saline(NS) for intravenous fluid on chloride levels and clinical outcomes.in patients with predicted severe acute pancreatitis (pSAP). SUMMARY BACKGROUND DATA: Isotonic crystalloids are recommended for initial fluid therapy in acute pancreatitis, but whether the use of BMES in preference to NS confers clinical benefits is unknown. METHODS: In this multicenter, stepped-wedge, cluster-randomized trial, we enrolled patients with pSAP (APACHE II score ≥8 and C-reactive protein >150 mg/L) admitted within 72 hours of the advent of symptoms. The study sites were randomly assigned to staggered start dates for one-way crossover from the NS phase (NS for intravenous fluid) to the BMES phase(Sterofudin for intravenous fluid). The primary endpoint was the serum chloride concentration on trial day3. Secondary endpoints included a composite of clinical and laboratory measures. RESULTS: Overall, 259 patients were enrolled from eleven sites to receive NS(n=147) or BMES(n=112). On trial day3, the mean chloride level was significantly lower in patients who received BMES(101.8 mmol/L(SD4.8) versus 105.8 mmol/L(SD5.9), difference -4.3 mmol/L [95%CI -5.6 to -3.0 mmol/L];P<0.001). For secondary endpoints, patients who received BMES had less systemic inflammatory response syndrome(19/112,17.0% versus 43/147,29.3%, P=0.024) and increased organ failure-free days (3.9 d(SD2.7) versus 3.5days(SD2.7), P<0.001) by trial day7. They also spent more time alive and out of ICU(26.4 d(SD5.2) versus 25.0days(SD6.4), P=0.009) and hospital(19.8 d(SD6.1) versus16.3days(SD7.2), P<0.001) by trial day30. CONCLUSIONS: Among patients with pSAP, using BMES in preference to NS resulted in a significantly more physiological serum chloride level, which was associated with multiple clinical benefits(Trial registration number: ChiCTR2100044432).

The novel CDK9 inhibitor, XPW1, alone and in combination with BRD4 inhibitor JQ1, for the treatment of clear cell renal cell carcinoma.

BACKGROUND: Clear cell renal cell carcinoma (ccRCC) is a highly lethal malignancy with few therapeutic options. Cyclin­dependent kinase 9 (CDK9), a potential therapeutic target of many cancers, has been recently observed to be upregulated in ccRCC patients. Therefore, we aimed to investigate the therapeutic potential of CDK9 in ccRCC and develop a novel CDK9 inhibitor with low toxicity for ccRCC treatment. METHODS: The expression of CDK9 in ccRCC was checked using the online database and tissue microarray analysis. shRNA-mediated CDK9 knockdown and CDK inhibitor were applied to evaluate the effect of CDK9 on ccRCC. Medicinal chemistry methods were used to develop a new CDK9 inhibitor with drugability. RNA-seq and ChIP-seq experiments were conducted to explore the mechanism of action. MTS, western blotting, and colony formation assays were performed to evaluate the anti-ccRCC effects of CDK9 knockdown and inhibition in vitro. The in vivo anti-tumour efficacy was evaluated in a xenograft model. RESULTS: CDK9 is overexpressed and associated with poor survival in ccRCC. Knockdown or inhibition of CDK9 significantly suppressed ccRCC cells. XPW1 was identified as a new potent and selective CDK9 inhibitor with excellent anti-ccRCC activity and low toxicity. In mechanism, XPW1 transcriptionally inhibited DNA repair programmes in ccRCC cells, resulting in an excellent anti-tumour effect. CDK9 and BRD4 were two highly correlated transcriptional regulators in ccRCC patients, and the BRD4 inhibitor JQ1 enhanced XPW1's anti-ccRCC effects in vitro and in vivo. CONCLUSIONS: This work provides valuable insights into the therapeutic potential of CDK9 in ccRCC. The CDK9 inhibitor XPW1 would be a novel therapeutic agent for targeting ccRCC, alone or in rational combinations.

Water-Induced Single-Crystal to Single-Crystal Transformation of Ionic Hydrogen-Bonded Organic Frameworks with Enhanced Proton Conductivity.

Two ionic hydrogen-bonded organic frameworks (iHOF-10, iHOF-11) were prepared using 1,1'-diamino-4,4'-bipyridine diiodide (Dbpy ⋅ 2I) and tetrakis(4-sulfophenyl)ethylene (H4 TPE). With increasing RH and temperature, water molecules induce single crystal to single crystal (SCSC) transformation of iHOF-10, resulting in the formation of iHOF-11. At 90 °C, 98 % RH, the proton conductivity of iHOF-11 (7.03×10-3  S cm-1 ) is 2.09 times higher than iHOF-10 (3.37×10-3  S cm-1 ). At 50 °C, 98 % RH, iHOF-11 (9.49×10-4  S cm-1 ) is 19.06 times higher than iHOF-10 (4.98×10-5  S cm-1 ). The proton conductivity shows water molecules enter the crystal and induce crystal transformation and reorganization of the hydrogen bonding structure, thus increasing the proton conductivity and stability.

Involvement of transverse mesocolon is associated with development of colonic fistula in patients with acute necrotizing pancreatitis.

BACKGROUND: Involvement of transverse mesocolon (TM) during acute necrotizing pancreatitis(ANP) indicates that inflammation has spread from retroperitoneal space to peritoneum. Nevertheless, the impact of TM involvement, as confirmed by contrast-enhanced computed tomography (CECT), on local complications and clinical outcomes was poorly investigated. PURPOSE: This study aimed to explore the association between CECT-diagnosed TM involvement and the development of colonic fistula in a cohort of ANP patients. METHODS: This is a single-center, retrospective cohort study involving ANP patients admitted from January 2020 to December 2020. TM involvement was diagnosed by two experienced radiologists. The study subjects were enrolled consecutively and divided into two groups: TM involvement and non-TM involvement. The primary outcome was colonic fistula during the index admission. Clinical outcomes were compared between the two groups, and the association between the TM involvement and the development of colonic fistula was assessed using multivariable analysis to adjust for baseline unbalances. RESULTS: A total of 180 patients with ANP were enrolled, and 86 (47.8%) patients had TM involvement. The incidence of the colonic fistula is significantly higher in patients with TM involvement (16.3% vs. 5.3%;p = 0.017). Moreover, the length of hospital stay was 24(13,68) days in patients with TM involvement and 15(7,31) days in those not (p = 0.001). Analysis of multivariable logistic regression revealed that TM involvement is an independent risk factor for the development of colonic fistula (odds ratio: 10.253, 95% CI: 2.206-47.650, p = 0.003). CONCLUSION: TM involvement in ANP patients is associated with development of colonic fistula in ANP patients.

S-dinotefuran affects the social behavior of honeybees (Apis mellifera)and increases their risk in the colony.

The toxic effects of neonicotinoid pesticides on honeybees is a global concern, whereas little is known about the effect of stereoisomeric pesticides among honeybee social behavior. In this study, we investigated the effects of stereoisomeric dinotefuran on honeybee social behavior. We found that honeybees exhibit a preference for consuming food containing S-dinotefuran, actively engage in trophallaxis with S-dinotefuran-consuming peers, and consequently acquire higher levels of S-dinotefuran compared with R-dinotefuran. In comparison to R-dinotefuran, S-dinotefuran stimulates honeybees to elevate their body temperature, thereby attracting more peers for trophallaxis. Transcriptome analysis revealed a significant enrichment of thermogenesis pathways due to S-dinotefuran exposure. Additionally, metabolome data indicated that S-dinotefuran may enhance body temperature by promoting lipid synthesis in the lysine degradation pathway. Consequently, body temperature emerges as a key factor influencing honeybee social behavior. Our study is the first to highlight the propensity of S-dinotefuran to raise honeybee body temperature, which prompts honeybee to preferentially engage in trophallaxis with peers exhibiting higher body temperatures. This preference may lead honeybees to collect more dinotefuran-contaminated food in the wild, significantly accelerating dinotefuran transmission within a population. Proactive trophallaxis further amplifies the risk of neonicotinoid pesticide transmission within a population, making honeybees that have consumed S-dinotefuran particularly favored within their colonies. These findings may contribute to our understanding of the higher risk associated with neonicotinoid use compared with other pesticides.

Evaluation and comparison of multi-omics data integration methods for cancer subtyping.

Computational integrative analysis has become a significant approach in the data-driven exploration of biological problems. Many integration methods for cancer subtyping have been proposed, but evaluating these methods has become a complicated problem due to the lack of gold standards. Moreover, questions of practical importance remain to be addressed regarding the impact of selecting appropriate data types and combinations on the performance of integrative studies. Here, we constructed three classes of benchmarking datasets of nine cancers in TCGA by considering all the eleven combinations of four multi-omics data types. Using these datasets, we conducted a comprehensive evaluation of ten representative integration methods for cancer subtyping in terms of accuracy measured by combining both clustering accuracy and clinical significance, robustness, and computational efficiency. We subsequently investigated the influence of different omics data on cancer subtyping and the effectiveness of their combinations. Refuting the widely held intuition that incorporating more types of omics data always produces better results, our analyses showed that there are situations where integrating more omics data negatively impacts the performance of integration methods. Our analyses also suggested several effective combinations for most cancers under our studies, which may be of particular interest to researchers in omics data analysis.

A network embedding based method for partial multi-omics integration in cancer subtyping.

Integrative analysis of multiple omics offers the opportunity to uncover coordinated cellular processes acting across different omics layers. The ever-increasing of multi-omics data provides us a comprehensive insight into cancer subtyping. Many multi-omics integrative methods have been developed, but few of them can deal with partial datasets in which some samples only have data for a subset of the omics. In this study, we propose a partial multi-omics integrative method, MSNE (Multiple Similarity Network Embedding), for cancer subtyping. MSNE integrates the multi-omics information by embedding the neighbor relations of samples defined by the random walk on multiple similarity networks. We compared MSNE with five existing multi-omics integrative methods on twelve datasets in both full and partial scenarios. MSNE achieved the best result on pan-cancer and image datasets. Furthermore, on ten cancer subtyping datasets, MSNE got the most enriched clinical parameters and comparable log-rank test P-values in survival analysis. In conclusion, MSNE is an effective and efficient integrative method for multi-omics data and, especially, has a strong power on partial datasets.

JMJD6 and U2AF65 co-regulate alternative splicing in both JMJD6 enzymatic activity dependent and independent manner.

JMJD6, a jumonji C (Jmj C) domain-containing protein demethylase and hydroxylase, has been implicated in an array of biological processes. It has been shown that JMJD6 interacts with and hydroxylates multiple serine/arginine-rich (SR) proteins and SR related proteins, including U2AF65, all of which are known to function in alternative splicing regulation. However, whether JMJD6 is widely involved in alternative splicing and the molecular mechanism underlying JMJD6-regulated alternative splicing have remained incompletely understood. Here, by using RASL-Seq, we investigated the functional impact of RNA-dependent interaction between JMJD6 and U2AF65, revealing that JMJD6 and U2AF65 co-regulated a large number of alternative splicing events. We further demonstrated the JMJD6 function in alternative splicing in jmjd6 knockout mice. Mechanistically, we showed that the enzymatic activity of JMJD6 was required for a subset of JMJD6-regulated splicing, and JMJD6-mediated lysine hydroxylation of U2AF65 could account for, at least partially, their co-regulated alternative splicing events, suggesting both JMJD6 enzymatic activity-dependent and independent control of alternative splicing. These findings reveal an intimate link between JMJD6 and U2AF65 in alternative splicing regulation, which has important implications in development and disease processes.

Arginine methylation of HSP70 regulates retinoid acid-mediated RARß2 gene activation.

Although "histone" methyltransferases and demethylases are well established to regulate transcriptional programs and to use nonhistone proteins as substrates, their possible roles in regulation of heat-shock proteins in the nucleus have not been investigated. Here, we report that a highly conserved arginine residue, R469, in HSP70 (heat-shock protein of 70 kDa) proteins, an evolutionarily conserved protein family of ATP-dependent molecular chaperone, was monomethylated (me1), at least partially, by coactivator-associated arginine methyltransferase 1/protein arginine methyltransferase 4 (CARM1/PRMT4) and demethylated by jumonji-domain-containing 6 (JMJD6), both in vitro and in cultured cells. Functional studies revealed that HSP70 could directly regulate retinoid acid (RA)-induced retinoid acid receptor ß2 (RARß2) gene transcription through its binding to chromatin, with R469me1 being essential in this process. HSP70's function in gene transcriptional regulation appears to be distinct from its protein chaperon activity. R469me1 was shown to mediate the interaction between HSP70 and TFIIH, which involves in RNA polymerase II phosphorylation and thus transcriptional initiation. Our findings expand the repertoire of nonhistone substrates targeted by PRMT4 and JMJD6, and reveal a new function of HSP70 proteins in gene transcription at the chromatin level aside from its classic role in protein folding and quality control.

Functionalized HgTe nanoparticles promote laser-induced solid phase ionization/dissociation for comprehensive glycan sequencing.

Glycoconjugates are ubiquitously present and play a critical role in various biological processes. Due to their low stability and incredibly high degree of structural diversity, the structural characterization of glycan generally requires chemical derivatization and sophisticated instrumentation. Herein, we report a method for complicated glycan characterization in a single assay by employing 2,5-dihydroxybenzoic acid functionalized mercury telluride nanoparticles (HgTe@DHB NPs) as a dual ionization-dissociation element in matrix-assisted laser desorption/ionization mass spectrometry. Using a linear glycan, HgTe@DHB NPs promote laser-induced extensive and intense dissociation of the glycan, superior to HgTe microparticles and other inorganic nanoparticles (TiO2, ZnO, and Mn2O3 NPs). Abundant generation of diagnostic glycosidic (Y-, and B-type ions) and cross-ring cleavage (A-type ions) ions permits unambiguous determination of the composition, sequence, branching, and linkage of labile sialylated glycans. The general utility of this approach was demonstrated by the characterization of labile sialylated glycans and two sets of complicated isomeric glycans. This phenomenon was delineated further by investigating the NP's physico-chemical characteristics, revealing that their nanoscale-dependent thermodynamic properties, including UV absorption, photoelectron release dynamics and thermal energy, were the key to levitate temperature synergistically, thus inducing spontaneous glycan decomposition during the nanoparticle-assisted laser desorption-ionization process. Our results show that this "pseudo-MS/MS" obtained by HgTe@DHB can be beneficial for the analysis of biologically relevant and more complicated carbohydrates, without the need for chemical pre-derivatization and conventional tandem mass spectrometry.

Induction of Nur77-dependent apoptotic pathway by a coumarin derivative through activation of JNK and p38 MAPK.

Coumarins are plant-derived natural products with a broad range of known pharmacological activities including anticancer effects. However, the molecular mechanisms by which this class of promising compounds exerts their anticancer effects remain largely unknown. We report here that a furanocoumarin named apaensin could effectively induce apoptosis of cancer cells through its activation of Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK). Apoptosis induction by apaensin in cancer cells was suppressed by chemical inhibitors of JNK and p38 MAPK. Inhibition of the expression of orphan nuclear receptor Nur77 by small interfering RNA (siRNA) approach also abrogated the death effect of apaensin. Molecular analysis demonstrated that JNK activation was required for the nuclear export of Nur77, a known apoptotic event in cancer cells. Although p38 MAPK activation was not involved in Nur77 nuclear export, it was essential for Nur77 mitochondrial targeting through induction of Nur77 interaction with Bcl-2, which is also known to convert Bcl-2 from an antiapoptotic to a proapoptotic molecule. Together, our results identify a new natural product that targets orphan nuclear receptor Nur77 through its unique activation of JNK and p38 MAPK and provide insight into the complex regulation of the Nur77-Bcl-2 apoptotic pathway.

A solvent-controlled photoresponsive ionic hydrogen-bonded organic framework for encryption applications.

Two novel ionic hydrogen-bonded organic frameworks (iHOF-17 and iHOF-18) were obtained by integrating organosulfonic acids with amidine salts. Among them, iHOF-18 exhibits fast, reversible, and high-contrast UV-induced photochromic properties, and this property is solvent-controlled. This work provides valuable insights for designing advanced anti-counterfeiting techniques and encryption applications.

Bone transport induces the release of factors with multi-tissue regenerative potential for diabetic wound healing in rats and patients.

Tibial cortex transverse distraction is a surgical method for treating severe diabetic foot ulcers (DFUs), but the underlying mechanism is unclear. We show that antioxidant proteins and small extracellular vesicles (sEVs) with multiple-tissue regenerative potential are released during bone transport (BT) in humans and rats. These vesicles accumulate in diabetic wounds and are enriched with microRNAs (miRNAs) (e.g., miR-494-3p) that have high regenerative activities that improve the circulation of ischemic lower limbs while also promoting neovascularization, fibroblast migration, and nerve fiber regeneration. Deletion of miR-494-3p in rats reduces the beneficial effects of BT on diabetic wounds, while hydrogels containing miR-494-3p and reduced glutathione (GSH) effectively repair them. Importantly, the ginsenoside Rg1 can upregulate miR-494-3p, and a randomized controlled trial verifies that the regimen of oral Rg1 and GSH accelerates wound healing in refractory DFU patients. These findings identify potential functional factors for tissue regeneration and suggest a potential therapy for DFUs.

Regulation of proteolytic cleavage of retinoid X receptor-α by GSK-3ß.

We recently reported that an N-terminally truncated retinoid X receptor-α (tRXRα) produced in cancer cells acts to promote cancer cell growth and survival through AKT activation. However, how RXRα is cleaved and how the cleavage is regulated in cancer cells remain undefined. In this study, we demonstrated that calpain II could cleave RXRα protein in vitro, generating two truncated RXRα products. The cleavage sites in RXRα were mapped by Edman N-terminal sequencing to Gly(90)↓Ser(91) and Lys(118)↓Val(119). Transfection of the resulting cleavage product RXRα/90, but not RXRα/118, resulted in activation of AKT in cancer cells, similar to the effect of tRXRα. In support of the role of calpain II in cancer cells, transfection of calpain II expression vector or its activation by ionomycin enhanced the production of tRXRα, whereas treatment of cells with calpain inhibitors reduced the levels of tRXRα. Co-immunoprecipitation assays also showed an interaction between calpain II and RXRα. In studying the regulation of tRXRα production, we observed that treatment of cells with lithium chloride or knockdown of glycogen synthase kinase-3ß (GSK-3ß) significantly increased the production of tRXRα. Conversely, overexpression of GSK-3ß reduced tRXRα expression. Furthermore, we found that the inhibitory effect of GSK-3ß on tRXRα production was due to its suppression of calpain II expression. Taken together, our data demonstrate that GSK-3ß plays an important role in regulating tRXRα production by calpain II in cancer cells, providing new insights into the development of new strategies and agents for the prevention and treatment of tRXRα-related cancers.

Taurine homeostasis requires de novo synthesis via cysteine sulfinic acid decarboxylase during zebrafish early embryogenesis.

Cysteine sulfinic acid decarboxylase (Csad) is the rate-limiting enzyme in the de novo biosynthesis of taurine. There are a number of physiological roles of taurine, such as bile salt synthesis, osmoregulation, lipid metabolism, and oxidative stress inhibition. To investigate the role of de novo synthesis of taurine during embryonic development, zebrafish csad was cloned and functionally analyzed. Semi-quantitative RT-PCR showed that csad transcripts are maternally deposited, while whole-mount in situ hybridization demonstrated that csad is expressed in yolk syncytial layer and various embryonic tissues such as notochord, brain, retina, pronephric duct, liver, and pancreas. Knockdown of csad significantly reduced the embryonic taurine level, and the affected embryos had increased early mortality and cardiac anomalies. mRNA coinjection and taurine supplementation rescued the cardiac phenotypes suggesting that taurine originating from the de novo synthesis pathway plays a role in cardiac development. Our findings indicated that the de novo synthesis pathway via Csad plays a critical role in taurine homeostasis and cardiac development in zebrafish early embryos.

[Study on preventive and therapeutic mechanism of traditional Chinese medicine based on analysis on key network nodes].

To analyze the intersections among the western medicine action network for preventing and treating coronary heart disease (CHD), as well as traditional Chinese medicine (TCM) action network for activating blood and dissolving stasis. In this article, 11 characteristic parameter values of network nodes, including connectivity, bottleneck, betweenness, were calculated. The target identification model was established based on key node characteristic parameters in the CHD-western medicine intersection network with support vector machine. Its C and y parameters were 5.14 and--1.11, respectively, with the predicted accuracies for positive and negative samples of 81.6% and 79.2%. The predicted sensitivity, specificity and accuracy of the test set samples were 81.5%, 78.3% and 79.6%, respectively. Besides, the model was applied to predict potential action targets of the CHD-activating blood and dissolving stasis TCM intersection network, and 180 positive nodes and 42 negative nodes were obtained. In this article, 9 positive nodes, including calnexin, interleukin-1, tumor necrosis factor, were taken as examples to analyze the action mechanism of TCM for preventing and treating CHD. The results showed that the network potential key target analysis method was helpful to explore the potential action targets of activating blood and dissolving stasis TCMs for preventing and treating CHD, methodologically supportive to reveal the action mechanism of TCMs at molecular and systematic levels, and significant in guiding the research and development of new drugs.

[Action mechanism of drugs for preventing and treating coronary heart disease based on biological networks].

Coronary heart disease (CHD) related genes and targets, as well as drug targets for preventing and treating CHD were taken as the study objects to build a CHD disease network and a drug action network preventing and treating CHD. Such topological characteristic parameters of the networks as degree distribution, characteristic path length, connectivity and heterogeneity were analyzed to verify the reliability of the networks. On that basis, the intersection calculation was conducted for both networks to analyze the drug action mechanism of their sub-networks. The disease network are composed of 15,221 nodes and 31,177 sides, while the drug action network preventing and treating CHD has 15,073 nodes and 32,376 sides. Both of their topological characteristic parameters showed scale-free small world structural characteristics. Two reaction pathways in the sub-networks-calcitonin gene-related peptide and IL-6 activated JAK/STAT were taken as examples to discuss the indirect action mechanism for preventing and treating CHD. The results showed that the biological network analysis method combining the disease network and the drug action network is helpful to further studies on the action mechanism of the drugs, and significant to the prevention and treatment of diseases.

Simultaneous Detection and Distribution of Five Juvenile Hormones in 58 Insect Species and the Absolute Configuration in 32 Insect Species.

Juvenile hormone (JH) plays an important role in regulating various insect physiological processes. Herein, a novel method (chiral and achiral) for the simultaneous detection of five JHs was established by processing a whole insect without complicated hemolymph extraction. The proposed method was used to determine the distribution of JHs in 58 insect species and the absolute configuration of JHs in 32 species. The results showed that JHSB3 was uniquely synthesized in Hemiptera, JHB3 was unique to Diptera, and JH I and JH II were unique to Lepidoptera. JH III was present in most insect species surveyed, with social insects having generally higher JH III titers. Interestingly, JHSB3 and JHB3, both double epoxidation JHs, were found in insects with sucking mouthparts. The absolute conformation of JH III and the 10C of the detected JHs were all R stereoisomers.

Intravenous amino acids may mediate the adverse effect of early parenteral nutrition on mortality in critically ill patients requiring mechanical ventilation: A post hoc analysis of the NEED trial.

BACKGROUND: There is controversy regarding the optimal timing of initiating parenteral nutrition (PN) in critically ill patients. We aimed to evaluate the association between early PN and clinical outcomes and explore the mediation effects of different macronutrients in a cohort of mechanically ventilated patients. METHODS: This is a post hoc analysis of the NEED trial aiming to investigate the effect of implementing an evidence-based feeding guideline in newly-admitted critically ill patients. All eligible patients were divided into those who received early PN within the first 3 days of enrollment (early PN) or those who did not (non-early PN). Propensity score matching with a one-to-one nearest neighbor-matching algorithm was applied to control potential confounders. Mediation analysis was used to test the indirect effect of different macronutrients from PN on the relationship between early PN and 28-day mortality. RESULTS: The propensity score matching created 370 matched pairs of 1154 patients that met the eligibility criteria. Compared with non-early PN, patients receiving early PN had significantly higher 28-day mortality (19.7% vs 12.4%; hazard ratio = 1.904; 95% CI, 1.063-3.410; P = 0.03). Mediation analysis showed that amino acids from early PN mediated 65% (mediation effect = 0.07; 95% CI, 0.02-0.13; P = 0.01) of the detrimental effect of early PN on the 28-day mortality. CONCLUSION: Early PN is associated with increased 28-day mortality in critically ill patients requiring invasive mechanical ventilation. The detrimental effect may be mediated by intravenous amino acids from early PN.