BACKGROUND AND OBJECTIVES:Current evidence suggests that gut microbiota dysbiosis accelerates aging and aging-related diseases through pro-inflammatory pathways. This study aimed to evaluate dietary quality in relation to inflammation and gut microbiota, and to explore their relationship with chronic diseases among urban Chinese adults aged 40-69 years. METHODS AND STUDY DESIGN:A cross-sectional study was conducted among urban Chinese adults aged 40-69 years. Dietary quality was assessed by dietary intake, dietary inflammation index (DII), and dietary index for gut microbiota (DI-GM). Log-binomial regression was per-formed to examine the associations between DII, DI-GM and chronic diseases. RESULTS:An excessive energy proportion from fat (37.4%) and an insufficient contribution from carbohydrates (44.7%) indicated an imbalance in macronutrient intake. The medians and interquartile ranges for DII and DI-GM of the participants were 1.3 (0.2, 2.5) and 3.0 (2.0,5.0), respectively, suggesting a pro-inflammatory and gut microbiota-unfavorable dietary tendency. Livestock contributed most to dietary inflammation in the population (standardized β = 0.251), whereas vegetables showed the strongest inverse effect (standardized β = -0.500). A higher DI-GM score was suggested to be a protective factor against self-reported dysglycemia (OR = 0.311; 95%CI: 0.118, 0.818). CONCLUSIONS:The participants exhibited an imbalance in macronutrient intake and a dietary tendency that was pro-inflammatory and unfavorable to gut microbiota. Notably, this study revealed a negative relationship between DI-GM and dysglycemia in middle-aged and elderly population, which under-scores the potential of targeting gut microbiota through diet for chronic disease prevention in this population.

Oxysterols, gut metabolites, and N6-methyladenosine (m6A) are extensively implicated in the pathogenesis of cognitive dysfunction, while their alterations in different stages of mild cognitive impairment (MCI) have not been elucidated. Therefore, this study was conducted to explore the associations of oxysterols, gut metabolites, and m6A methylation profiles in early MCI (EMCI) and late MCI (LMCI) individuals. Liquid chromatography-mass spectrometry, untargeted metabolomic analysis, and m6A mRNA Epitranscriptomic Microarray were used to detect the characteristics of serum oxysterols (n = 35/group), fecal gut metabolites (n = 30/group), and m6A in whole blood (n = 4/group) respectively. The concentration of serum β-amyloid (Aβ) was detected with ELISA (n = 25/group). The gene expression of amyloid precursor protein (APP) and its key enzyme β-secretase (BACE1) in whole blood were measured by quantitative real-time PCR (n = 25/group). EMCIs and LMCIs, especially LMCIs, exhibited poorer performance in almost all global and multidimensional cognitive tests. Serum 27-hydroxycholesterol (27-OHC) and 24S-hydroxycholesterol (24S-OHC) were elevated in EMCI and LMCI groups. Changes in gut metabolites occurred mainly in the EMCI group, in which several gut metabolites, including Procyanidin dimer B7 and Phorbol myristate, were significantly decreased. The m6A methylation landscape of EMCIs and LMCIs obviously differed from Controls. Hypomethylated mRNAs accounted for the majority and were mainly accompanied by downregulated mRNAs, which was consistent with the downregulated expression of the m6A writer methyltransferase-like 4 (METTL4). 27-OHC and 24S-OHC combined with various gut metabolites significantly distinguished between MCI subgroups from healthy controls (EMCI/Control: AUC = 0.877; LMCI/Control: AUC = 0.952). Heatmap revealed the correlation between Phorbol myristate and differentially m6A-methylated mRNAs. Differentially expressed gut metabolites and methylated mRNAs were commonly enriched in 34 KEGG metabolic pathways, including cholesterol metabolism and neurodegenerative disease-related pathways. Our study explored the altered oxysterols, gut metabolites, and m6A methylation and their associations in different stages of MCI. The potential function of aberrant gut metabolites in oxysterols and m6A methylation driving MCI progression warrants further mechanistic investigation.

Identifying the mechanistic targets of crosstalk between sarcopenia (SA) and mild cognitive impairment (MCI) is critical for screening high-risk populations and exploring effective prevention and treatment strategies. In a nationwide multicenter prospective cohort study combined with an RCT study, it is found that indexes of muscle health reveal a strong predictive relationship with cognitive performance assessed using the Montreal Cognitive Assessment (MoCA). Furthermore, Random Forest models suggest that lecithin can predict both diseases. Erythrocyte lipid analysis and RCT study indicate the protective function of lecithin and the potential involvement of irisin in that process. In rodent models, phosphocholine (PC) alleviates learning and memory impairments and muscle attenuation in SAMP8 mice, while FNDC5/irisin knockdown accelerates brain and muscle damage or eliminates the protective effects of PC. Transcriptome analysis shows that PGC1α (the regulator of FNDC5) is regulated by PC treatment, and the results of knocking out PGC1α and FNDC5/irisin are consistent. Here it is found that muscle-secreted FNDC5/irisin is a key target of "muscle-brain" crosstalk, and lecithin may postpone the progression of MCI and SA by stimulating PGC1α-FNDC5/irisin-mediated cross-protection of cognition and skeletal muscle.

The epigenetic regulation of genes involved in cholesterol and oxysterol homeostasis is an emerging field with significant potential for elucidating the association between sterol homeostasis and diseases. DNA, RNA, histone modifications, as well as non-coding RNA, regulate cholesterol and oxysterol homeostasis by coordinating pathways involved in cholesterol synthesis, uptake, efflux, and alterations in metabolites. Therefore, dysregulation of epigenetic modifications may have important implications for the pathogenesis of cholesterol and oxysterol metabolism disorders. Here, we review recent advances in the function and mechanism of the interaction between cholesterol/oxysterol metabolism regulation and epigenetic modifications to discuss how each of the 4 parts of cholesterol metabolism is executed and regulated with the participation of epigenetic modification.

Oxysterols, as metabolites of cholesterol, play a key role in cholesterol homeostasis, autophagosome formation, and regulation of immune responses. Disorders in oxysterol metabolism are closely related to the pathogenesis of neurodegenerative diseases. To systematically investigate the profound molecular regulatory mechanisms of neurodegenerative diseases, it is necessary to quantify oxysterols and their metabolites in central and peripheral biospecimens simultaneously and accurately. However, there are a lot of unsolved problems with the existing methods, such as the hindrance of applying a single method to different biological specimens or the challenge of simultaneous quantification due to differential groups on the ends of the oxysterol side chains. Herein, according to the physicochemical properties and structure of oxysterols, an optimized liquid chromatography-tandem mass spectrometry method for the quantification of oxysterols was established by optimizing the sample preparation process, chromatographic conditions, mobile phase pH, and solvent selection. Seven oxysterols were detected by this method, including 27-hydroxycholesterol, 7α-hydroxycholesterol, 7α,27-dihydroxycholesterol, 7-dehydrocholesterol, 7α-hydroxy-3-oxo-4-cholestenoic acid, 3-hydroxy-5-cholestenoic acid, and 24(S)-hydroxycholesterol. Non-derivatization extraction with methyl tert-butyl ether was used for different biospecimens, followed by simultaneous chromatographic separation of oxysterols on a phenyl hexyl column. By repeated validation, this method exhibited satisfactory linearity, precision, recovery, sensitivity, repeatability, and stability, and it was successfully applied to the detection of oxysterols in the plasma, cerebral cortex, and liver of mouse. In summary, our optimized method enables concurrent analysis and quantification of oxysterols and their metabolites in various biospecimens, presenting a broad range of applicability.

Perturbed cholesterol metabolism may play an important role in the development of dementia and its preclinical stage, mild cognitive impairment (MCI). Oxysterols, the metabolites generated during cholesterol oxidation, also appear to be risk factors for MCI. Therefore, we aimed to investigate if the metabolic profile of blood oxysterols could be used to characterize MCI risk. This cross-sectional study incorporated 501 participants-253 patients with MCI and 248 cognitively normal controls. Serum levels of 22 free oxysterols were measured, and a set of 27 oxysterol-related gene polymorphisms was genotyped. Five [27-hydroxycholesterol (27-OHC), 27-OHC periphery-derived metabolite 3β-hydroxy-5-cholestenoic acid (27-CA) and brain-derived metabolite 7α-hydroxy-3-oxo-4-cholestenoic acid (7-HOCA), 4β-hydroxycholesterol (4β-OHC); 4α-hydroxycholesterol (4α-OHC)] of the twenty-two oxysterols detected in serum significantly differed between the patients with MCI and controls, greatly distinguishing patients with MCI from control individuals (AUC=0.834, 95 % CI: 0.804-0.866). Association analyses demonstrated significant correlations between these candidate oxysterol biomarkers with younger age, higher blood lipids, worse cognitive performance, and higher monounsaturated fatty acid intake. This panel of serum free oxysterols as candidate serum oxysterol biomarkers for MCI highlighted the essential role of 27-OHC in the pathogenesis of early dementia prevention. (The study registered in the Chinese Clinical Trial Registry as ChiCTR-OOC-17011882).

Background/Objectives: Alterations of oxysterols and gut microbiota have been recognized as indicators affecting mild cognitive impairment (MCI) and sarcopenia, respectively, whereas their association with co-dysfunction has not been investigated. Methods: In this study, a total of 1035 individuals were divided into Control (n = 264), MCI (n = 435), and MCI with possible sarcopenia (MPS, n = 336) groups. Cognition and muscle indexes, serum oxysterols, and gut microbiota were measured. Spearman’s rank coefficients were calculated to determine their correlations. Results: Performances of global and multidimensional cognitive tests was successively worse in the Control, MCI, and MPS groups. Longer duration of five-time chair stand test, lower 6-meter walk speed, and handgrip strength were observed in the MPS group, along with increased 27-hydroxycholesterol (27-OHC) and 5α,6α-epoxycholesterol and decreased 5α-Cholest-8(14)-ene-3β,15α-diol (15-HC). Higher concentrations of amyloid precursor protein (APP), neurofilament, and C-terminal agrin fragment (CAF) were discovered in the MCI and MPS groups. The α-diversity of gut microbiota in the MCI and MPS group was remarkably decreased, followed by a shifted abundance of microbial taxa, such as Alistipes and Rikenellaceae. Multiple significant correlations were found between cognition and muscle indexes and with oxysterols. Conclusions: Our study indicates that oxysterols and gut microbiota are prominently involved in the co-dysfunction of cognition and muscle.

Gut microbiota and microRNAs (miRNAs) have been proved to be intimately involved in dementia. Our previous studies have showed that oxysterols and the subsequent neurotoxic effects contributed to the pathogenesis of cognitive decline. However, the exact mechanism linking dietary oxysterol-induced cognitive changes, gut microbiota, and miRNAs remains elusive. Here, two sets of experiments were conducted on male C57BL/6J mice treated with mixed-oxysterol diet or 27-hydroxycholesterol (27-OHC) combined with antibiotic cocktails and miRNA antagonists. Neurobehavioral tests were conducted to assess learning and memory of mice. 16S ribosomal DNA gene sequencing was performed to evaluate microbial diversity and community composition. Oxysterol levels were detected using HPLC–MS. Western blotting and RT-qPCR were used to detect the expression of the intestinal barrier-related factors. We found that a 0.05

Background and Objectives: To explore the nutritional challenges and its influencing factors of adults aged 4069 living in Chinese cities. Methods and Study Design: This cross-sectional study involved 300 subjects from 29 cities in China. Questionnaires were used to collect demographic information, presence of chronic disease, and the use of nutritional supplements and fortified foods. 24-hour food intake was recorded using the Eat-Right Assistant, a validated digital service. Results: Fiber (56.7%), calcium (66.3%) and selenium (67.0%) were the nutrients with the highest insufficient intake. The foods with the highest inadequate consumption were dairy products (91%), fruits (84.3%), tubers (76.3%), soybeans and nuts (70%), and whole grains (65%). Even though 95.7% of the study population showed medium-high level of dietary diversity, dietary imbalance was present among 99% of the subjects. Higher socioeconomic status, passive health awareness, or the use of nutritional supplements or fortified foods showed positive influence on nutrient intake and dietary quality. Conclusions: This research provided insights into the dietary intake status and its influencing factors of 300 urban residents aged 40-69. The adult population still face a challenge of inadequate nutrient intake and imbalanced diet. In addition, this study supported the feasibility of using a digital service in research. Further studies with a larger sample size are needed to confirm current findings. This will help to clarify the unmet nutritional needs of adults in China and thus help to achieve healthy aging.

Trophoblast cell syncytialization is essential for placental and fetal development. Abnormal trophoblast cell fusion leads to pregnancy pathologies, such as preeclampsia (PE), intrauterine growth restriction (IUGR), and miscarriage. 27-hydroxycholesterol (27-OHC) is the most abundant oxysterol in human peripheral blood synthesized by sterol 27-hydroxylase (CYP27A1) and is considered a critical mediator between hypercholesterolemia and a variety of related disorders. Gestational hypercholesterolemia was associated with spontaneous preterm delivery and low birth weight (LBW) in term infants, yet the mechanism is unclear. In this study, two trophoblast cell models and CD-1 mice were used to evaluate the effects of 27-OHC on trophoblast fusion during placenta development. Two different kinds of trophoblast cells received a dosage of 2.5, 5, or 10 uM 27-OHC. Three groups of pregnant mice were randomly assigned: control, full treatment (E0.5-E17.5), or late treatment (E13.5-E17.5). All mice received daily intraperitoneal injections of saline (control group) and 27-OHC (treatment group; 5.5 mg/kg). In vitro experiments, we found that 27-OHC inhibited trophoblast cell fusion in primary human trophoblasts (PHT) and forskolin (FSK)-induced BeWo cells. 27-OHC up-regulated the expression of the PI3K/AKT/mTOR signaling pathway-related proteins. Moreover, the PI3K inhibitor LY294002 rescued the inhibitory effect of 27-OHC. Inhibition of trophoblast cell fusion by 27-OHC was also observed in CD-1 mice. Furthermore, fetal weight and placental efficiency decreased and fetal blood vessel development was inhibited in pregnant mice treated with 27-OHC. This study was the first to prove that 27-OHC inhibits trophoblast cell fusion by Activating PI3K/AKT/mTOR signaling pathway. This study reveals a novel mechanism by which dyslipidemia during pregnancy results in adverse pregnancy outcomes.

IntroductionTo investigate the effect of vitamin D3 (VD3) combined with folic acid (FA) intervention on the cognitive function among patients with mild cognitive impairment (MCI) and vitamin D deficiency.MethodsOur study is a single-center, randomized, controlled trial. A total of 402 patients were randomly assigned to the placebo group (n=135), FA group (n=134), and FA+1600IU VD3 group (n=133). The intervention period was 24 weeks. The primary endpoint was the mean change in Montreal Cognitive Assessment (MoCA) compared to baseline. Secondary endpoints included other cognitive functions, serum vitamin D, folic acid, and homocysteine levels.ResultsThe Intention-to-Treat analysis results of MoCA showed that the adjusted Least Squares Means (LSM) differences between the FA+1600IU VD3 group and the placebo or FA group were 0.456 (95% CI -0.198 to 1.11; p=0.171) and 0.038 (95% CI -0.600 to 0.676; p=0.907), respectively, and the Per-protocol set analysis results showed that the adjusted LSM differences between the FA+1600IU VD3 group and the placebo or FA group were 0.659 (95% CI 0.005 to 1.313; p=0.048) and 0.251 (95% CI -0.387 to 0.889; p=0.44), respectively.ConclusionThe effect of FA+1600IU VD3 intervention for 6 months on overall cognitive function in MCI patients with vitamin D deficiency was not significant, but its role may be underestimated and requires further long-term studies to confirm.

The abnormality in N6-methyladenosine (m6A) methylation is involved in the course of Alzheimer’s disease (AD), while the intervention of 27-Hydroxycholesterol (27-OHC) can affect the m6A methylation modification in the brain cortex. Disordered gut microbiota is a key link in 27-OHC leading to cognitive impairment, and further studies have found that the abundance of Roseburia intestinalis in the gut is significantly reduced under the intervention of 27-OHC. This study aims to investigate the association of 27-OHC, Roseburia intestinalis in the gut, and brain m6A modification in the learning and memory ability injury. In this study, 9-month-old male C57BL/6J mice were treated with antibiotic cocktails for 6 weeks to sweep the intestinal flora, followed by 27-OHC or normal saline subcutaneous injection, and then Roseburia intestinalis or normal saline gavage were applied to the mouse. The 27-OHC level in the brain, the gut barrier function, the m6A modification in the brain, and the memory ability were measured. From the results, we observed that 27-OHC impairs the gut barrier function, causing a disturbance in the expression of m6A methylation-related enzymes and reducing the m6A methylation modification level in the brain cortex, and finally leads to learning and memory impairment. However, Roseburia intestinalis supplementation could reverse the negative effects mentioned above. This study suggests that 27-OHC-induced learning and memory impairment might be linked to brain m6A methylation modification disturbance, while Roseburia intestinalis, as a probiotic with great potential, could reverse the damage caused by 27-OHC. This research could help reveal the mechanism of 27-OHC-induced neural damage and provide important scientific evidence for the future use of Roseburia intestinalis in neuroprotection.

Background This study aims to explore the relationship between dietary lecithin intake and cognitive function and the development and progression of Mild cognitive impairment (MCI) in the elderly over 60 years old. Methods The research undertaken included a cohort of 1917 participants aged over 60. Body composition was evaluated through bioelectrical impedance analysis. Cognitive function and dietary intake were assessed using neuropsychological tests and a food frequency questionnaire. Spearman correlation analysis, multiple linear regression, logistic regression, and receiver operating characteristic curves were employed to elucidate the relationship of dietary lecithin on MoCA (Montreal Cognitive Assessment) score and the risk of MCI and predictive effect. Results Of 1917 participants enrolled, 1023 (53.4%) had MCI and 542 (53.0%) were women. After adjusting for multiple confounders, multiple linear regression showed that after dichotomizing lecithin and serum cholesterol indicators according to the median, high levels of lecithin, TC(Total Cholesterol) and low levels of LDL-C(Low density lipoprotein cholesterol)/HDL-C(High density lipoprotein cholesterol) were associated with higher MoCA; logistic regression showed that compared with low intake level, the odds ratio (95% CI) of MCI risk in high dietary lecithin intake group was 0.80(0.64,0.99). The results of ROC curve showed that the model had a good predictive effect on MCI. Conclusions Higher dietary lecithin intake was associated with better performance on cognitive assessments and diminished risk of MCI among the elderly population aged 60 and above. It possesses the capabilities to function as prospective biomarkers that may indicate an increased risk of cognitive decline among the elderly demographic.

The role of the gut microbiota in the association between high-fat diet and cognition is not clear. We hypothesized that a high-fat diet may influence cognition by altering the intestinal microbiota. Fecal microbiota isolated from male C57BL/6J mice feeding on various high-fat diets and a control basic diet were transplanted to antibiotic-treated recipient mice. The measurement of weight and plasma lipids, novel object recognition test, 16S rRNA gene sequencing of feces, and hematoxylin-eosin staining of the hippocampal cornu ammonis 1 and cornu ammonis 3 areas were performed for all mice. Compared with those in the control and n-3 polyunsaturated fatty acid (n-3 PUFA) groups, donor obese mice fed with diets high in long-chain saturated fatty acids, n-6 polyunsaturated fatty acids (n-6 PUFAs), and trans fatty acids exhibited significant cognitive impairment (all P < .05). There were fewer neurons in the hippocampal area in the n-6 PUFA group than in the n-3 PUFA group (P < .05). Similar effect on cognition and neurons in hippocampal area in corresponding recipient mice were revealed after fecal microbiota transplantation. In addition, the composition of intestinal microbiota differed among recipient mice after fecal microbiota transplantation from donor mice. According to these results, it was concluded that diets rich in long-chain saturated fatty acids, n-6 PUFAs, and trans fatty acids may lead to cognitive impairment by damaging the structure of the hippocampus through influencing the intestinal microbiota in mice, whereas a diet high in n-3 PUFAs may exhibit a beneficial effect.

Background and Objective:Cognitive dysfunction is highly prevalent in obese people, and food is a key factor in obesity, and dietary inflammatory index (DII) can reflect whether diet has anti-inflammatory or pro-inflammatory potential. In addition, dietary fatty acid consumption is linked to inflammation, obesity, and cognitive impairment. Erythrocyte membrane fatty acids can reflect dietary fatty acid intake. Our hypothesis was that erythrocyte membrane fatty acids might have a significant impact on the relationship between DII and cognition in obese individuals, and we designed experiments to test the hypothesis.Methods:In three villages in Beijing, we collected 579 respondents from individuals 45 to 75 years old and categorized them by body mass index. The Montreal Cognitive Assessment (MoCA) score and DII score was calculated and gas chromatography was used to measure the proportion of erythrocyte membrane fatty acids. The relationship between the DII score and cognition was examined using multiple linear regression and binary logistic regression. Mediation analysis can help to understand the causal chain between variables, deeply explore the internal relationship and mechanism of action between variables. So a multiple chain mediation model was developed to investigate the mediating factors between the DII score and cognitive association.Results:According to adjusted linear regression, higher DII scores were linked to lower MoCA scores in the obese group. The negative correlation between DII score and cognitive function score remains in binary linear regression. We discovered through mediation analysis that erythrocyte membrane fatty acids mediate the detrimental link between DII and cognitive function in obese individuals.Conclusion:We propose that higher DII scores in obese people are associated with a decline in cognitive function. In addition, this effect might be mediated via the fatty acids in the erythrocyte membrane.

Gut microbiome dysbiosis has been widely implicated in cognitive impairment, but the identity of the specific bacterial taxa and mechanisms are not fully elucidated. Brain glucose hypometabolism coincides with the cognitive decline. This study explored the link among cognition, gut microbiota and glucose uptake based on the fecal microbiota transplantation from mild cognitive impairment individuals (MCI-FMT) and investigated whether similar mechanisms were involved in 27-hydroxycholesterol (27-OHC)-induced cognitive decline. Our results showed that the MCI-FMT mice exhibited learning and memory decline and morphological lesions in the brain and colon tissues. There were reduced 18F-fluorodeoxyglucose uptake, downregulated expression of glucose transporters (GLUT1,3,4) and upregulated negative regulator of glucose uptake (TXNIP) in the brain. MCI-FMT altered the bacterial composition and diversity of the recipient mice, and the microbial signatures highlighted by the increased abundance of Bacteroides recapitulated the negative effects of MCI bacterial colonization. However, inhibiting Bacteroidetes or TXNIP increased the expression of GLUT1 and GLUT4, significantly improving brain glucose uptake and cognitive performance in 27-OHC-treated mice. Our study verified that cognitive decline and abnormal cerebral glucose uptake were associated with gut microbiota dysbiosis; we also revealed the involvement of Bacteroidetes and molecular mechanisms of TXNIP-related glucose uptake in cognitive deficits caused by 27-OHC.

Brain glucose hypometabolism is a significant manifestation of Alzheimer's disease (AD). 27-hydroxycholesterol (27-OHC) and the gut microbiota have been recognized as factors possibly influencing the pathogenesis of AD. This study aimed to investigate the link between 27-OHC, the gut microbiota, and brain glucose uptake in AD. Here, 6-month-old male C57BL/6 J mice were treated with sterile water or antibiotic cocktails, with or without 27-OHC and/or 27-OHC synthetic enzyme CYP27A1 inhibitor anastrozole (ANS). The gut microbiota, brain glucose uptake levels, and memory ability were measured. We observed that 27-OHC altered microbiota composition, damaged brain tissue structures, decreased the 2-deoxy-2-[18 F] fluorodeoxyglucose (18F-FDG) uptake value, downregulated the gene expression of glucose transporter type 4 (GLUT4), reduced the colocalization of GLUT1/glial fibrillary acidic protein (GFAP) in the hippocampus, and impaired spatial memory. ANS reversed the effects of 27-OHC. The antibiotic-treated mice did not exhibit similar results after 27-OHC treatment. This study reveals a potential molecular mechanism wherein 27-OHC-induced memory impairment might be linked to reduced brain glucose uptake, mediated by the gut microbiota.

The cholesterol-oxidized metabolite 27-hydroxycholesterol (27-OHC) is synthesized by CYP27A1, which is a key factor in vitamin D and oxysterol metabolism. Both vitamin D and 27-OHC are considered to play important roles in Alzheimer's disease (AD). The study aims to research the effects of co-supplementation of vitamin D, folic acid, and vitamin B-12 on learning and memory ability in vitamin D-deficient mice, and to explore the underlying mechanism. In this study, C57BL/6J mice were fed a vitamin D-deficient diet for 13 weeks to establish a vitamin D-deficient mice model. The vitamin D-deficient mice were then orally gavaged with vitamin D (VD), folic acid (FA), and vitamin B-12 (VB12) alone or together for eight weeks. Following the gavage, the learning and memory ability of the mice were evaluated by Morris Water Maze and Novel object recognition test. The CYP27A1-related gene and protein expressions in the liver and brain were determined by qRT-PCR. The serum level of 27-OHC was detected by HPLC-MS. Serum levels of 25(OH)D, homocysteine (Hcy), and S-Adenosylmethionine (SAM) were measured by ELISA. After feeding with the vitamin D-deficient diet, the mice performed longer latency to a platform (p < 0.001), lower average speed (p = 0.026) in the Morris Water Maze, a lower time discrimination index (p = 0.009) in Novel object recognition, and performances were reversed after vitamin D, folic acid and vitamin B-12 supplementation alone or together (p < 0.05). The gene expressions of CYP27A1 in the liver and brain were upregulated in the vitamin D-deficiency (VDD) group compared with the control (CON) group (p = 0.015), while it was downregulated in VDD + VD and VDD + VD-FA/VB12 groups compared with the VDD group (p < 0.05), with a similar trend in the protein expression of CYP27A1. The serum levels of 27-OHC were higher in the VDD group, compared with CON, VDD + VD, and VDD + VD-FA/VB12 group (p < 0.05), and a similar trend was found in the brain. The serum 25(OH)D levels were significantly decreased in the vitamin D-deficiency group (p = 0.008), and increased in the vitamin D-supplemented group (p < 0.001). The serum levels of SAM were higher in the B vitamins-supplemented group, compared with CON and VDD groups (p < 0.05). This study suggests that CYP27A1 expression may be involved in the mechanism of learning and memory impairment induced by vitamin D deficiency. Co-supplementation with vitamin D, folic acid, and vitamin B-12 significantly reverses this effect by affecting the expression of CYP27A1, which in turn regulates the metabolism of 27-OHC, 25(OH)D, and SAM.

Abstract This study was aiming to verify critical role of gut microbiota linking diet-induced obesity and cognitive dysfunction. After antibiotic treatment, male C57BL/6 mice were subjected to fecal microbiota transplantation (FMT) using fecal microbiota isolated from donor mice fed on various high-fat diets and control basic diet. Novel object recognition test, 16S rRNA gene sequencing of feces and haematoxylineosin staining of hippocampal CA1 area were performed for all mice. The results showed that donor obese mice induced by diets high in long-chain saturated fatty acid (LCSFA), n-6 polyunsaturated fatty acid (n-6 PUFA) and trans fatty acid (TFA) had significant cognitive impairment (all Ps < 0.05) compared with that in control and n-3 polyunsaturated fatty acid (n-3 PUFA) groups. In recipient mice, the similar effect of above high-fat diets was revealed after FMT, while in absence of obesity. The donor mice in LCSFA, medium-chain saturated fatty acid (MCSFA), n-6 PUFA, and TFA groups showed more structural breakage and less nerve cells in hippocampal CA1 area than that in other groups, which was similar to corresponding recipients. According to these results it was concluded that high LCSFA, n-6 PUFA, and TFA diets may impair the cognitive function by damaging the structures of CA1 region in hippocampal through influencing intestinal microbiota in mice.