Association of serum interleukin-2 with severity and prognosis in hospitalized patients with community-acquired pneumonia: a prospective cohort study.

The prior studies have shown that interleukin-2 (IL-2) exerts important roles in the pathological and physiological processes of lung diseases. However, the role of IL-2 in community-acquired pneumonia (CAP) is still uncertain. Through a prospective cohort study, our research will explore the correlations between serum IL-2 levels and the severity and prognosis in CAP patients. There were 267 CAP patients included. Blood samples were obtained. Serum IL-2 were tested by enzyme-linked immunosorbent assay (ELISA). Demographic traits and clinical characteristics were extracted. Serum IL-2 were gradually elevated with increasing severity scores in CAP patients. Correlation analyses revealed that serum IL-2 were connected with physiological parameters including liver and renal function in CAP patients. According to a logistic regression analysis, serum IL-2 were positively correlated with CAP severity scores. We also tracked the prognostic outcomes of CAP patients. The increased risks of adversely prognostic outcomes, including mechanical ventilation, vasoactive agent usage, ICU admission, death, and longer hospital length, were associated with higher levels of IL-2 at admission. Serum IL-2 at admission were positively associated with severe conditions and poor prognosis among CAP patients, indicated that IL-2 may involve in the initiation and development of CAP. As a result, serum IL-2 may be an available biomarker to guide clinicians in assessing the severity and determining the prognosis of CAP.

Cordycepin Modulates Microglial M2 Polarization Coupled with Mitochondrial Metabolic Reprogramming by Targeting HKII and PDK2.

The microenvironment mediated by the microglia (MG) M1/M2 phenotypic switch plays a decisive role in the neuronal fate and cognitive function of Alzheimer's disease (AD). However, the impact of metabolic reprogramming on microglial polarization and its underlying mechanism remains elusive. This study reveals that cordycepin improved cognitive function and memory in APP/PS1 mice, as well as attenuated neuronal damage by triggering MG-M2 polarization and metabolic reprogramming characterized by increased OXPHOS and glycolysis, rather than directly protecting neurons. Simultaneously, cordycepin partially alleviates mitochondrial damage in microglia induced by inhibitors of OXPHOS and glycolysis, further promoting MG-M2 transformation and increasing neuronal survival. Through confirmation of cordycepin distribution in the microglial mitochondria via mitochondrial isolation followed by HPLC-MS/MS techniques, HKII and PDK2 are further identified as potential targets of cordycepin. By investigating the effects of HKII and PDK2 inhibitors, the mechanism through which cordycepin targeted HKII to elevate ECAR levels in the glycolysis pathway while targeting PDK2 to enhance OCR levels in PDH-mediated OXPHOS pathway, thereby inducing MG-M2 polarization, promoting neuronal survival and exerting an anti-AD role is elucidated.

Early signs of neurodegenerative diseases: Possible mechanisms and targets for Golgi stress.

The Golgi apparatus plays a crucial role in mediating the modification, transport, and sorting of intracellular proteins and lipids. The morphological changes occurring in the Golgi apparatus are exceptionally important for maintaining its function. When exposed to external pressure or environmental stimulation, the Golgi apparatus undergoes adaptive changes in both structure and function, which are known as Golgi stress. Although certain signal pathway responses or post-translational modifications have been observed following Golgi stress, further research is needed to comprehensively summarize and understand the related mechanisms. Currently, there is evidence linking Golgi stress to neurodegenerative diseases; however, the role of Golgi stress in the progression of neurodegenerative diseases such as Alzheimer's disease remains largely unexplored. This review focuses on the structural and functional alterations of the Golgi apparatus during stress, elucidating potential mechanisms underlying the involvement of Golgi stress in regulating immunity, autophagy, and metabolic processes. Additionally, it highlights the pivotal role of Golgi stress as an early signaling event implicated in the pathogenesis and progression of neurodegenerative diseases. Furthermore, this study summarizes prospective targets that can be therapeutically exploited to mitigate neurodegenerative diseases by targeting Golgi stress. These findings provide a theoretical foundation for identifying novel breakthroughs in preventing and treating neurodegenerative diseases.

Phycoremediation Potential of Salt-Tolerant Microalgal Species: Motion, Metabolic Characteristics, and Their Application for Saline-Alkali Soil Improvement in Eco-Farms.

Microalgae have great potential for remediating salt-affected soil. In this study, the microalgae species Coelastrella sp. SDEC-28, Dunaliella salina SDEC-36, and Spirulina subsalsa FACHB-351 were investigated for their potential to rehabilitate salt-affected soils. Nylon screens with optimal aperture sizes and layer numbers were identified to efficiently intercept and harvest biomass, suggesting a correlation between underflow capability and the tough cell walls, strong motility, and intertwining characteristics of the algae. Our investigations proved the feasibility of incorporating monosodium glutamate residue (MSGR) into soil extracts at dilution ratios of 1/200, 1/2000, and 1/500 to serve as the optimal medium for the three microalgae species, respectively. After one growth period of these three species, the electrical conductivities of the media decreased by 0.21, 1.18, and 1.78 mS/cm, respectively, and the pH remained stable at 7.7, 8.6, and 8.4. The hypotheses that microalgae can remediate soil and return profits have been verified through theoretical calculations, demonstrating the potential of employing specific microalgal strains to enhance soil conditions in eco-farms, thereby broadening the range of crops that can be cultivated, including those that are intolerant to saline-alkali environments.

Phosphorus-supplemented seawater-wastewater cyclic system for microalgal cultivation: Production of high-lipid and high-protein algae.

The reuse of wastewater after seawater cultivation is critically important. In this study, a phosphorus-supplemented seawater-wastewater cyclic system (PSSWCS) based on Chlorella pyrenoidosa SDEC-35 was developed. With the addition of phosphorus, the algal biomass and the ability to assimilate nitrogen and carbon were improved. At the nitrogen to phosphorus ratio of 20:1, the biomass productivity per mass of nitrogen reached 3.6 g g-1 (N) day-1 in the second cycle. After the third cycle the protein content reached 35.7% of dry mass, and the major metabolic substances in PSSWCS reached the highest content level of 89.5% (35.7% protein, 38.3% lipid, and 15.5% carbohydrate). After the fourth cycle the lipid content maintained at 40.1%. Furthermore, 100.0% recovery of wastewater in PSSWCS increased the nitrogen and carbon absorption to 15.0 and 396.8 g per tonne of seawater. This study achieved seawater-wastewater recycle and produced high-lipid and high-protein algae by phosphorus addition.

Novel methodology for detection and prediction of mild cognitive impairment using resting-state EEG.

BACKGROUND: Early discrimination and prediction of cognitive decline are crucial for the study of neurodegenerative mechanisms and interventions to promote cognitive resiliency. METHODS: Our research is based on resting-state electroencephalography (EEG) and the current dataset includes 137 consensus-diagnosed, community-dwelling Black Americans (ages 60-90 years, 84 healthy controls [HC]; 53 mild cognitive impairment [MCI]) recruited through Wayne State University and Michigan Alzheimer's Disease Research Center. We conducted multiscale analysis on time-varying brain functional connectivity and developed an innovative soft discrimination model in which each decision on HC or MCI also comes with a connectivity-based score. RESULTS: The leave-one-out cross-validation accuracy is 91.97% and 3-fold accuracy is 91.17%. The 9 to 18 months' progression trend prediction accuracy over an availability-limited subset sample is 84.61%. CONCLUSION: The EEG-based soft discrimination model demonstrates high sensitivity and reliability for MCI detection and shows promising capability in proactive prediction of people at risk of MCI before clinical symptoms may occur.

Transparent PEDOT counter electrodes for bifacial dye-sensitized solar cells using a cobalt complex mediator.

Poly(3,4-ethylenedioxythiophene) (PEDOT) aggregate-deposited counter electrodes (CEs) were applied to bifacial dye-sensitized solar cells with a cobalt complex electrolyte. The high transparency and excellent electrochemical activity of PEDOT CEs result in an impressive cell bifaciality of 0.92 under standard test conditions (AM 1.5G, 100 mW cm-2), and maximum power production of 11.3% under realistic conditions with an effective albedo of 50%.

The diagnostic value of lncRNA HOTAIR for cervical carcinoma in vaginal discharge and serum.

There is a lower incidence of cervical carcinoma compared with other common carcinomas, however, the mortality rate of cervical carcinoma is higher, suggesting that the treatment and prognosis of cervical carcinoma are relatively poor. Therefore, cervical carcinoma patients urgently need to find new diagnostic markers for early detection and treatment. One hundred and fifty cervical carcinoma and 100 benign cervical disease patients from 2019 January to 2021 December in Tianjin Central Hospital of Gynecology Obstetrics were selected and 100 healthy women were as normal group. The expression of HOX transcript antisense RNA (HOTAIR) in cervical carcinoma and paracancerous tissue, serum sample was measured by realtime PCR assay. The receiver operating characteristic of HOTAIR for cervical carcinoma was analyzed. The study found that the expression level of HOTAIR in primary cervical carcinoma is closely related to tumor metastasis and prognosis. The expression level of HOTAIR in paracancerous tissue was significantly lower than that in cancer tissue, and the expression level of HOTAIR in vaginal discharge and serum was higher than that in cervical carcinoma patients which was positively correlated with tumor malignancy, meanwhile, HOTAIR was significantly reduced after surgery 3 months both in vaginal discharge and serum. In order to examine the diagnostic efficiency of HOTAIR for cervical carcinoma, we found that the area under curve of vaginal discharge was 0.9723, sensitivity was 92%, specificity was 98%, the area under curve of serum was 0.8518, sensitivity was 79%, and specificity was 94% by receiver operating characteristic analysis. The accuracy were 92.7% and 89.3% in vaginal discharge and serum via certified by cervical carcinoma and benign cervical disease patient and healthy people. The above results show that the diagnostic performance of HOTAIR in vaginal discharge is higher than that of serum, and it is expected to become a marker for cervical carcinoma diagnosis and treatment.

Interface Engineering Modulated Valley Polarization in MoS2/hBN Heterostructure.

Layered transition metal dichalcogenides (TMDs) provide a favorable research platform for the advancement of spintronics and valleytronics because of their unique spin-valley coupling effect, which is attributed to the absence of inversion symmetry coupled with the presence of time-reversal symmetry. To maneuver the valley pseudospin efficiently is of great importance for the fabrication of conceptual devices in microelectronics. Here, we propose a straightforward way to modulate valley pseudospin with interface engineering. An underlying negative correlation between the quantum yield of photoluminescence and the degree of valley polarization was discovered. Enhanced luminous intensities were observed in the MoS2/hBN heterostructure but with a low value of valley polarization, which was in stark contrast to those observed in the MoS2/SiO2 heterostructure. Based on the steady-state and time-resolved optical measurements, we reveal the correlation between exciton lifetime, luminous efficiency, and valley polarization. Our results emphasize the significance of interface engineering for tailoring valley pseudospin in two-dimensional systems and probably advance the progression of the conceptual devices based on TMDs in spintronics and valleytronics.

Citrus Honey Ameliorates Liver Disease and Restores Gut Microbiota in Alcohol-Feeding Mice.

Citrus honey (CH) is rich in nutrients that have a wide variety of biological functions, such as antibacterial, anti-inflammatory, and antioxidant activities, and which demonstrate therapeutic properties, such as anti-cancer and wound-healing abilities. However, the effects of CH on alcohol-related liver disease (ALD) and the intestinal microbiota remain unknown. This study aimed to determine the alleviating effects of CH on ALD and its regulatory effects on the gut microbiota in mice. In total, 26 metabolites were identified and quantified in CH, and the results suggested that the primary metabolites were abscisic acid, 3,4-dimethoxycinnamic acid, rutin, and two markers of CH, hesperetin and hesperidin. CH lowered the levels of aspartate aminotransferase, glutamate aminotransferase, and alcohol-induced hepatic edema. CH could promote the proliferation of Bacteroidetes while reducing the abundance of Firmicutes. Additionally, CH also showed some inhibitory effects on the growth of Campylobacterota and Turicibacter. CH enhanced the secretion of short-chain fatty acids (SCFAs), such as acetic acid, propionic acid, butyric acid, and valeric acid. Given its alleviating functions in liver tissue damage and its regulatory effects on the gut microbiota and SCFAs, CH could be a promising candidate for the therapeutic treatment of ALD.

Role of N6-methyladenosine modification in central nervous system diseases and related therapeutic agents.

N6-methyladenosine (m6A) is a ubiquitous mRNA modification in eukaryotes. m6A occurs through the action of methyltransferases, demethylases, and methylation-binding proteins. m6A methylation of RNA is associated with various neurological disorders, including Alzheimer's disease (AD), Parkinson's disease (PD), depression, cerebral apoplexy, brain injury, epilepsy, cerebral arteriovenous malformations, and glioma. Furthermore, recent studies report that m6A-related drugs have attracted considerable concerns in the therapeutic areas of neurological disorders. Here, we mainly summarized the role of m6A modification in neurological diseases and the therapeutic potential of m6A-related drugs. The aim of this review is expected to be useful to systematically assess m6A as a new potential biomarker and develop innovative modulators of m6A for the amelioration and treatment of neurological disorders.

A Study on the Heating and Deicing Performance of Microwave-Absorbing Asphalt Mixtures.

Road icing in winter brings challenges to traffic safety, and microwave heating and deicing technology is an effective method with the advantages of high efficiency and environmental protection. Magnetite has been widely used as a microwave-absorbing material in pavement. In this paper, magnetite powder formed by crushing natural magnetite and high-purity Fe3O4 powder after purification were mixed to replace mineral powder, and the magnetite aggregate was used to replace the limestone aggregate with the same particle size to enhance the asphalt mixtures' microwave absorption capacity. The effect of microwave heating time and microwave power on the heating of the asphalt mixtures was studied, and the heating performance of different thicknesses of the asphalt mixtures under microwave radiation was evaluated. The heating performance of the mixtures under different initial temperatures and ice layer thicknesses was also assessed. The results showed that the addition of the magnetite powder-Fe3O4 powder and the magnetite aggregate significantly enhanced the heating performance of the asphalt mixtures by microwave heating. The replacement of the magnetite powder-Fe3O4 powder, the microwave heating time, and the microwave power had positive effects on the heating efficiency of the asphalt mixtures. Moreover, the thinner asphalt mixtures had a better heating performance. The heating and deicing performance of the mixtures decreased with a decline in initial temperature. As the ice thickness increased, the deicing time of the specimen surface to reach 0 °C also increased.

From lab to application: Cultivating limnetic microalgae in seawater coupled with wastewater for biodiesel production on a pilot scale.

The technology of cultivating salt-tolerant limnetic microalgae in seawater reduces the freshwater demand and costs of biodiesel production. However, all current trials still occur on the bench scale, and efforts for pilot-scale operation are urgently needed. This study firstly optimised the diameter of the photobioreactors (PBRs) to 0.2 m, as the single module to produce lipid-rich Golenkinia sp. SDEC-16 because of the better algal growth and light attenuation in the PBRs, and then established a 1000 L algal cultivation system. In a medium of seawater supplemented with monosodium glutamate wastewater at a ratio of 1:1000 (S-MSGW), the biomass productivity was 0.26 g/L/d, which was approaching the 0.30 g/L/d obtained in BG11, and the lipid productivity (98.99 mg/L/d) was doubled in comparison to growth in BG11. C16-C18 accounted for more than 98% of the total fatty acid in S-MSGW, and the biodiesel properties also met the biodiesel standards. The input cost of the biodiesel in this pilot-scale system was estimated to be 2.2 $/kg. When considering the carbon reduction and diversified application of the biomass, Golenkinia sp. would annually capture 186.77 kg/m3 PBR of CO2, and yield an output-to-input ratio (OIR) of 3.4 in S-MSGW, higher than the 2.8 in BG11.

Cordycepin improved neuronal synaptic plasticity through CREB-induced NGF upregulation driven by MG-M2 polarization: a microglia-neuron symphony in AD.

PURPOSE: Microglia-neuron crosstalk is critically involved in synaptic plasticity and degeneration by releasing diverse mediators in Alzheimer's disease (AD). Therefore, determining contributors that modulate the systemic microenvironment is essential. Cordycepin (CCS) is a novel neuroprotective compound obtained from Cordyceps militaris. However, the anti-AD efficacy and potential mechanism of CCS treatment remain unclear. This study aimed to elucidate the microglia-neuron symphony in AD after CCS treatment and to explore the possible mechanisms of its neuroprotective efficacy. METHODS AND RESULTS: CCS treatment improved learning and memory impairment in 9-month-old APP/PS1 mice by behavioral tests. CCS polarized the microglia from M1 to M2, inhibited neuronal apoptosis and promoted synaptic remodeling accompanied by in vivo and in vitro upregulation of NGF. The cAMP-response element-binding protein (CREB) was also activated after MG-M2 polarization. Further, we verified that the sg3 promoter region of NGF (-1018 to -1011) is the key binding site for CREB-induced NGF transcription, which increased NGF expression and secretion. Finally, microglia-derived NGF was confirmed as an important mediator in microglia-neuron symphony to improve the neuronal microenvironment after CCS treatment. CONCLUSIONS: CCS improved the neuronal synaptic plasticity and senescence by promoting MG-M2 activation driven by CREB-induced NGF upregulation and facilitated symphony communication between the microglia and neuron in AD. This study provides a new perspective on the development of a novel strategy for anti-AD therapy and offers new targets for anti-AD drug development.

Functional lightweight polystyrene@polydopamine nanoparticle for high-performance ELISA.

Nanoparticles are usually used as carrier to load more antibody and enzyme to improve the sensitivity of enzyme-linked immunosorbent assay (ELISA). However, limited by high density and complicated modification procedure, the traditional nanoparticles such as Au nanoparticles (AuNPs) usually induce large background signal and poor reproducibility in ELISA. In this work, functional lightweigh nanoparticle polystyrene@polydopamine (PS@PDA) was prepared and induced as the carrier of detection antibody and horseradish peroxidase (HRP) to form PS@PDA@Ab2/HRP biojungates. The appropriate density (close to water) and good hydropilicity ensure the good dispersion of PS@PDA@Ab2/HRP in solution, preventing the physical sedimention and decreasing the background signal even though the bioconjugate's size is close to 200 nm. The large surface area and abundant active group from PDA facilitate the loading of detection antibody and HRP, improving the loading efficiency and stability of biojungates. Based on it, taking interleukin-17A (IL-17A, a biomarker of psoriasis) as the detection target, we developed a PS@PDA-based sandwich ELISA, achieving a sensitive dynamic range from 0.3 to 80 pg/mL and a detection limit of 0.2 pg/mL. Furthermore, the contents of IL-17A were assayed successfully in 10-fold diluted serum samples from psoriasis patients. Compared with those commercial or AuNP-based ELISA, our PS@PDA-based ELISA method exhibits higher sensitivity, lower background interference, and higher stability, which will significantly improve the application of ELISA in the low-abundant biomolecule assays.

Study on Microwave Deicing Efficiency of Microwave-Absorbing Concrete Pavements and Its Influencing Factors.

Microwave deicing technology, as a new environmentally friendly deicing technology, can effectively solve the problem of the frequent icing of road surfaces in the winter, which affects the safety of traffic. To improve the efficiency of microwave deicing on cement concrete pavement, this study proposed the use of magnetite, iron sulfide slag, steel slag, lead-zinc slag, and graphite as microwave-absorbing materials, and conducted microwave deicing tests under the influence of five factors, namely the form of the pavement surface structure, the content of the microwave-absorbing material, microwave power, the shielding state, and dry and wet conditions. Layer by layer, we selected the combination of pavement surface structure, microwave-absorbing material content, microwave power, shielding state, and dry and wet conditions on the bottom surface of the concrete slab with the optimal deicing effect. The results showed that the 2 cm scattered microwave-absorbing surface concrete structure has the fastest heating rate; the higher the magnetite content and microwave power, the higher the deicing efficiency; the maximum heating rate can be increased by 17.6% when the shielding layer is set at the bottom of the cement concrete slab; and the heating rate of the microwave-absorbing concrete slab in the wet state is increased by 20.8% relative to the dry state. In summary, 7000 W of power, a magnetite content of 60 vol % in the scattered microwave-absorbing surface, a shielding layer set at the bottom surface, and wet conditions can greatly improve the efficiency of microwave deicing compared with the microwave ice melting effects of plain cement concrete and other microwave-absorbing materials mixed into the concrete. In addition, the temperature uniformity of the microwave-absorbing materials is essential to improve the deicing efficiency of microwave-absorbing concrete, so it is essential to explore it further.

Tuning the optical absorption performance of MoS2 monolayers with compressive strain.

Strain engineering has been extensively applied as a promising strategy in the regulation of physical and chemical properties of two-dimensional (2D) materials, which remarkably broadens their application prospects in flexible electronics and chip manufacturing. However, the difficulty in fixing a flexible substrate under compression and the challenge in adjusting the focal distance have hindered the in-depth investigation of compressive strain. Here, we fabricated a home-made strain loading device and proposed a compressive strain measurement method, via which the strain-dependent optical absorption properties of MoS2 monolayers under compression has been studied. According to the measured optical absorption spectra, the first blueshift and then redshift trend under compression was obviously observed. The reliability of the experimentally observed trend in peak position shift was theoretically verified by density functional theory calculation. Our work offers a feasible way to characterize optical properties of 2D materials under compressive strain and expands the space for the development of next-generation micro/nano-scale optoelectronic devices.

Exploring recycled agricultural wastes for high-rate removal of nitrogen in wastewater: Emphasizing on the investigation of the inner driving force and comparison with conventional liquid carbon sources.

In this study, four typical recycled agricultural wastes (AWs), corn cob, wheat straw, sawdust and walnut shells (named AW1, AW2, AW3 and AW4, respectively), were selected as external solid carbon sources to enhance the removal of nitrogen in wastewater, and specifically, the driving mechanism was thoroughly investigated. The leaching experiments showed that the dissolved organic carbon (DOC) release capacity followed the order of AW1>AW2>AW3>AW4, ranging from 6.21 to 31.92 mg/g. DOC released from AWs mainly consisted of protein-like substances, fulvic acid-like substances and humic-like substances. AW1 and AW2 achieved comparable NOx--N removal performance with a liquid carbon source of sodium acetate (SA) during the long-term denitrification experiments (>94.2%) but not for the other two AWs (only 16.8%-38.1%). Denitrification performance relied on DOC released from AWs at the beginning, while the enrichment of the functional CAZymes (including glycoside hydrolase and carbohydrate esterase) involved in cellulose and hemicellulose decomposition of AWs and functional genes (GAPDH, gap 2, PK, etc.) related to glycolysis were the inner driving force, which guaranteed the continuous supply of electron donors for denitrification. The relatively high abundances of napAB, narGHI, nirKS, norBC and nosZ, which encode nitrate reductase, nitrite reductase, NO reductase and N2O reductase, assured the better denitrification performance in the SA, AW1 and AW2 groups. In addition to denitrification-related functional genes, the relative abundances of nirBD and nrfAH associated with dissimilatory nitrate reduction were much higher in AW1 and AW2 groups than in SA group, implying that the nitrogen removal mechanism should be different in liquid carbon source and AW-based solid carbon source systems. In addition, GLU, gltBD and glnA, which participate in ammonia assimilation were the highest in the AW2 group, resulting in a large amount of organic nitrogen accumulation (peak concentration of approximately 24.5 mg/L), and this finally ruled it out as an alternative external carbon source. The abovementioned microbial mechanism was verified based on the correlation analysis of nutrient removal and functional genes combined with host bacterial analysis. Our study can provide valuable information for understanding the mechanism of using AWs as alternative external carbon sources to promote the removal of nitrogen in wastewater.

Synthesis of graphene nanomesh with symmetrical fractal patterns via hydrogen-free chemical vapor deposition.

Graphene nanomesh (GNM), an emerging graphene nanostructure with a tunable bandgap, has gained tremendous interests owing to its great potentials in the fields of high-performance field-effect transistors, electrochemical sensors, new generation of spintronics and energy converters. In previous works, GNM has been successfully obtained on copper foil surface by employing hydrogen as an etching agent. A more facile, and low-cost strategy for the preparation of GNM is required. Here, we demonstrated a direct and feasible means for synthesizing large-area GNM with symmetrical fractal patterns via a hydrogen-free chemical vapor deposition method. The influences of the growth time and the gas source flow on the morphology of GNM patterns were systematically investigated. Then, we exhibited the key reaction details and proposed a growth mechanism of the GNM synthesis during the hydrogen-free chemical vapor deposition process. This work provides a valuable guidance for quality control in GNM mass production.

Association of Circulating Apolipoprotein AI Levels in Patients With Alzheimer's Disease: A Systematic Review and Meta-Analysis.

With the development of medicine, our research on Alzheimer's disease (AD) has been further deepened, but the mechanism of its occurrence and development has not been fully revealed, and there is currently no effective treatment method. Several studies have shown that apolipoprotein AI (ApoA-I) can affect the occurrence and development of Alzheimer's disease by binding to amyloid ß (Aß). However, the association between circulating levels of ApoA-I and AD remains controversial. We conducted a meta-analysis of 18 studies published between 1992 and 2017 to determine whether the ApoA-I levels in the blood and cerebrospinal fluid (CSF) are abnormal in AD. Literatures were searched in PubMed, EMBASE and Web of Science databases without language limitations. A pooled subject sample including 1,077 AD patients and 1,271 healthy controls (HCs) was available to assess circulating ApoA-I levels; 747 AD patients and 680 HCs were included for ApoA-I levels in serum; 246 AD patients and 456 HCs were included for ApoA-I levels in plasma; 201 AD patients and 447 HCs were included for ApoA-I levels in CSF. It was found that serum and plasma levels of ApoA-I were significantly reduced in AD patients compared with HCs {[standardized mean difference (SMD) = -1.16; 95% confidence interval (CI) (-1.72, -0.59); P = 0.000] and [SMD = -1.13; 95% CI (-2.05, -0.21); P = 0.016]}. Patients with AD showed a tendency toward higher CSF ApoA-I levels compared with HCs, although this difference was non-significant [SMD = 0.20; 95% CI (-0.16, 0.56); P = 0.273]. In addition, when we analyzed the ApoA-I levels of serum and plasma together, the circulating ApoA-I levels in AD patients was significantly lower [SMD = -1.15; 95% CI (-1.63, -0.66); P = 0.000]. These results indicate that ApoA-I deficiency may be a risk factor of AD, and ApoA-I has the potential to serve as a biomarker for AD and provide experimental evidence for diagnosis of AD. Systematic Review Registration: PROSPERO, identifier: 325961.