Arteriovenous metabolomics in pigs reveals CFTR regulation ofmetabolism inmultiple organs.

Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene cause cystic fibrosis (CF), a multiorgan disease that exhibits diverse metabolic defects. However, other than specific CFTR mutations, the factors that influence disease progression and severity remain poorly understood. Aberrant metabolite levels have been reported, but whether CFTR loss itself or secondary abnormalities (infection, inflammation, malnutrition, and various treatments) drive metabolic defects are uncertain. Here, we implemented comprehensive arteriovenous metabolomics in newborn CF pigs, and the results revealed CFTR as a bona fide regulator of metabolism. CFTR loss impaired metabolite exchange across organs, including disrupted lung uptake of fatty acids yet enhanced uptake of arachidonic acid, a precursor of pro-inflammatory cytokines. CFTR loss also impaired kidney reabsorption of amino acids and lactate and abolished renal glucose homeostasis. These and additional unexpected metabolic defects prior to disease manifestations reveal a fundamental role for CFTR in controlling multi-organ metabolism. Such discovery informs a basic understanding of CF, provides a foundation for future investigation, and has implications for developing therapies targeting only a single tissue.

Aberrant splicing in Huntington's disease via disrupted TDP-43 activity accompanied by altered m6A RNA modification.

Huntington's disease (HD) is a neurodegenerative disorder caused by a CAG repeat expansion in the first exon of the HTT gene encoding huntingtin. Prior reports have established a correlation between CAG expanded HTT and altered gene expression. However, the mechanisms leading to disruption of RNA processing in HD remain unclear. Here, our analysis of the reported HTT protein interactome identifies interactions with known RNA-binding proteins (RBPs). Total, long-read sequencing and targeted RASL-seq of RNAs from cortex and striatum of the HD mouse model R6/2 reveals increased exon skipping which is confirmed in Q150 and Q175 knock-in mice and in HD human brain. We identify the RBP TDP-43 and the N6-methyladenosine (m6A) writer protein methyltransferase 3 (METTL3) to be upstream regulators of exon skipping in HD. Along with this novel mechanistic insight, we observe decreased nuclear localization of TDP-43 and cytoplasmic accumulation of phosphorylated TDP-43 in HD mice and human brain. In addition, TDP-43 co-localizes with HTT in human HD brain forming novel nuclear aggregate-like bodies distinct from mutant HTT inclusions or previously observed TDP-43 pathologies. Binding of TDP-43 onto RNAs encoding HD-associated differentially expressed and aberrantly spliced genes is decreased. Finally, m6A RNA modification is reduced on RNAs abnormally expressed in striatum from HD R6/2 mouse brain, including at clustered sites adjacent to TDP-43 binding sites. Our evidence supports TDP-43 loss of function coupled with altered m6A modification as a novel mechanism underlying alternative splicing/unannotated exon usage in HD and highlights the critical nature of TDP-43 function across multiple neurodegenerative diseases.

MAPK13 stabilization via m6A mRNA modification limits anticancer efficacy of rapamycin.

N6-adenosine methylation (m6A) is the most abundant mRNA modification that controls gene expression through diverse mechanisms. Accordingly, m6A-dependent regulation of oncogenes and tumor suppressors contributes to tumor development. However, the role of m6A-mediated gene regulation upon drug treatment or resistance is poorly understood. Here, we report that m6A modification of mitogen-activated protein kinase 13 (MAPK13) mRNA determines the sensitivity of cancer cells to the mechanistic target of rapamycin complex 1 (mTORC1)-targeting agent rapamycin. mTORC1 induces m6A modification of MAPK13 mRNA at its 3' untranslated region through the methyltransferase-like 3 (METTL3)-METTL14-Wilms' tumor 1-associating protein(WTAP) methyltransferase complex, facilitating its mRNA degradation via an m6A reader protein YTH domain family protein 2. Rapamycin blunts this process and stabilizes MAPK13. On the other hand, genetic or pharmacological inhibition of MAPK13 enhances rapamycin's anticancer effects, which suggests that MAPK13 confers a progrowth signal upon rapamycin treatment, thereby limiting rapamycin efficacy. Together, our data indicate that rapamycin-mediated MAPK13 mRNA stabilization underlies drug resistance, and it should be considered as a promising therapeutic target to sensitize cancer cells to rapamycin.

Gut microbiota indole-3-propionic acid mediates neuroprotective effect of probiotic consumption in healthy elderly: A randomized, double-blind, placebo-controlled, multicenter trial and in vitro study.

BACKGROUND & AIMS: The beneficial effects of probiotic consumption on age-related decline in cerebral function have been previously reported in the literature; however, the mechanistic link between gut and brain interactions has not yet been fully elucidated. Therefore, this study aimed to identify the role of gut microbiota-derived metabolites in gut-brain interactions via blood metabolomic profiling analysis in clinical trials and in vitro mechanistic studies. METHODS: A randomized, double-blind, placebo-controlled, multicenter clinical trial was conducted in 63 healthy elderly individuals (≥65 years of age). Participants were administered either placebo (placebo group, N = 31) or probiotic capsules (Bifidobacterium bifidum BGN4 and Bifidobacterium longum BORI; probiotics group, N = 32) for 12 weeks. Global and targeted metabolomic profiling analyses of their blood samples were then performed using 1H nuclear magnetic resonance and liquid chromatography-mass spectrometry methods, both at baseline and at the end of the trial. Gut microbial analysis was conducted using the 16S ribosomal ribonucleic acid gene sequencing method. Subsequently, microglial BV2 cells were treated in vitro with indole-3-propionic acid (IPA) following lipopolysaccharide stimulation, and neuronal SH-SY5Y cells were treated with conditioned media from the BV2 cells. Finally, the levels of pro-inflammatory cytokines in BV2 cells and neurotrophins in SH-SY5Y cells were quantified using a real-time polymerase chain reaction or enzyme-linked immunosorbent assay. RESULTS: The metabolomic profiling analyses showed that probiotic consumption significantly altered the levels of metabolites involved in tryptophan metabolism (P < 0.01). Among these metabolites, gut microbiota-produced IPA had a 1.91-fold increase in the probiotics group (P < 0.05) and showed a significant relation to gut bacterial profiles (P < 0.01). Elevated IPA levels were also positively associated with the level of serum brain-derived neurotropic factor (BDNF) in the probiotics group (r = 0.28, P < 0.05), showing an inverse trend compared to the placebo group. In addition, in vitro treatment with IPA (5 µM) significantly reduced the concentration of proinflammatory TNF-α in activated microglia (P < 0.05), and neuronal cells cultured with conditioned media from IPA-treated microglia showed a significant increase in BDNF and nerve growth factor production (P < 0.05). CONCLUSIONS: These results show that gut microbiota-produced IPA plays a role in protecting the microglia from inflammation, thus promoting neuronal function. Therefore, this suggests that IPA is a significant mediator linking the interaction between the gut and the brain in the elderly with probiotic supplementation.

Screening of gall bladder cancer through infrared analysis of bile and examination of varied bile constituent composition by the disease.

To demonstrate the infrared (IR)-based bile analysis as a reliable screening tool for gall bladder (GB) cancer, we analyzed a sample set of 37 diverse bile samples (five normal, 18 GB polyp, six hepatocellular carcinoma (HCC), and eight GB cancer subjects). Bile samples of normal subjects (control) and HCC patients were newly included to examine if IR-based bile analysis could be expanded to identify HCC. Concentrations of three bile acids and eight bile salts in the aqueous phase samples were determined in parallel and lipidomic analysis of nine lipid classes in the organic phase samples was performed using liquid chromatography-mass spectrometry. Concentrations of bile salts were lower and relative abundances of bile salts were dissimilar between GB cancer samples and remained group samples. Also, the levels of lipids such as phosphatidylcholines and phosphatidylethanolamines were again lower and their relative abundances in the organic phase of GB cancer samples were different from those of other samples. IR spectral features of the aqueous, organic, and amphiphilic aggregate phases were individually characteristic, while not descriptive enough for the thorough identification of GB cancer. Nonetheless, since they were mutually complementary to represent different metabolites in bile, the use of three phase-merged spectra was synergetic to yield the superior discrimination of GB cancer.

Sex-dependent effects of multiple acute concurrent stresses on memory: a role for hippocampal estrogens.

Memory disruption commonly follows chronic stress, whereas acute stressors are generally benign. However, acute traumas such as mass shootings or natural disasters-lasting minutes to hours and consisting of simultaneous physical, social, and emotional stresses-are increasingly recognized as significant risk factors for memory problems and PTSD. Our prior work has revealed that these complex stresses (concurrent multiple acute stresses: MAS) disrupt hippocampus-dependent memory in male rodents. In females, the impacts of MAS are estrous cycle-dependent: MAS impairs memory during early proestrus (high estrogens phase), whereas the memory of female mice stressed during estrus (low estrogens phase) is protected. Female memory impairments limited to high estrogens phases suggest that higher levels of estrogens are necessary for MAS to disrupt memory, supported by evidence that males have higher hippocampal estradiol than estrous females. To test the role of estrogens in stress-induced memory deficits, we blocked estrogen production using aromatase inhibitors. A week of blockade protected male and female mice from MAS-induced memory disturbances, suggesting that high levels of estrogens are required for stress-provoked memory impairments in both males and females. To directly quantify 17ß-estradiol in murine hippocampus we employed both ELISA and mass spectrometry and identified significant confounders in both procedures. Taken together, the cross-cycle and aromatase studies in males and females support the role for high hippocampal estrogens in mediating the effect of complex acute stress on memory. Future studies focus on the receptors involved, the longevity of these effects, and their relation to PTSD-like behaviors in experimental models.

Dietary Fructose and Fructose-Induced Pathologies.

The consumption of fructose as sugar and high-fructose corn syrup has markedly increased during the past several decades. This trend coincides with the exponential rise of metabolic diseases, including obesity, nonalcoholic fatty liver disease, cardiovascular disease, and diabetes. While the biochemical pathways of fructose metabolism were elucidated in the early 1990s, organismal-level fructose metabolism and its whole-body pathophysiological impacts have been only recently investigated. In this review, we discuss the history of fructose consumption, biochemical and molecular pathways involved in fructose metabolism in different organs and gut microbiota, the role of fructose in the pathogenesis of metabolic diseases, and the remaining questions to treat such diseases.

AIFM2 Is Required for High-Intensity Aerobic Exercise in Promoting Glucose Utilization.

Skeletal muscle is a major regulator of glycemic control at rest, and glucose utilization increases drastically during exercise. Sustaining a high glucose utilization via glycolysis requires efficient replenishment of NAD+ in the cytosol. Apoptosis-inducing mitochondrion-associated factor 2 (AIFM2) was previously shown to be a NADH oxidoreductase domain-containing flavoprotein that promotes glycolysis for diet and cold-induced thermogenesis. Here, we find that AIFM2 is selectively and highly induced in glycolytic extensor digitorum longus (EDL) muscle during exercise. Overexpression (OE) of AIFM2 in myotubes is sufficient to elevate the NAD+-to-NADH ratio, increasing the glycolytic rate. Thus, OE of AIFM2 in skeletal muscle greatly increases exercise capacity, with increased glucose utilization. Conversely, muscle-specific Aifm2 depletion via in vivo transfection of hairpins against Aifm2 or tamoxifen-inducible haploinsufficiency of Aifm2 in muscles decreases exercise capacity and glucose utilization in mice. Moreover, muscle-specific introduction of NDE1, Saccharomyces cerevisiae external NADH dehydrogenase (NDE), ameliorates impairment in glucose utilization and exercise intolerance of the muscle-specific Aifm2 haploinsufficient mice. Together, we show a novel role for AIFM2 as a critical metabolic regulator for efficient utilization of glucose in glycolytic EDL muscles.

Glycerate from intestinal fructose metabolism induces islet cell damage and glucose intolerance.

Dietary fructose, especially in the context of a high-fat western diet, has been linked to type 2 diabetes. Although the effect of fructose on liver metabolism has been extensively studied, a significant portion of the fructose is first metabolized in the small intestine. Here, we report that dietary fat enhances intestinal fructose metabolism, which releases glycerate into the blood. Chronic high systemic glycerate levels induce glucose intolerance by slowly damaging pancreatic islet cells and reducing islet sizes. Our findings provide a link between dietary fructose and diabetes that is modulated by dietary fat.

Estimating the Neutralizing Effect and Titer Correlation of Semi-Quantitative Anti-SARS-CoV-2 Antibody Immunoassays.

For the clinical application of semi-quantitative anti-SARS-CoV-2 antibody tests, the analytical performance and titer correlation of the plaque reduction neutralization test (PRNT) need to be investigated. We evaluated the analytical performance and PRNT titer-correlation of one surrogate virus neutralization test (sVNT) kit and three chemiluminescent assays. We measured the total antibodies for the receptor-binding domain (RBD) of the spike protein, total antibodies for the nucleocapsid protein (NP), and IgG antibodies for the RBD. All three chemiluminescent assays showed high analytical performance for the detection of SARS-CoV-2 infection, with a sensitivity ≥ 98% and specificity ≥ 99%; those of the sVNT were slightly lower. The representativeness of the neutralizing activity of PRNT ND50 ≥ 20 was comparable among the four immunoassays (Cohen's kappa ≈ 0.80). Quantitative titer correlation for high PRNT titers of ND50 ≥ 50, 200, and 1,000 was investigated with new cut-off values; the anti-RBD IgG antibody kit showed the best performance. It also showed the best linear correlation with PRNT titer in both the acute and convalescent phases (Pearson's R 0.81 and 0.72, respectively). Due to the slowly waning titer of anti-NP antibodies, the correlation with PRNT titer at the convalescent phase was poor. In conclusion, semi-quantitative immunoassay kits targeting the RBD showed neutralizing activity that was correlated by titer; measurement of anti-NP antibodies would be useful for determining past infections.

Inhibition of nonalcoholic fatty liver disease in mice by selective inhibition of mTORC1.

Nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) remain without effective therapies. The mechanistic target of rapamycin complex 1 (mTORC1) pathway is a potential therapeutic target, but conflicting interpretations have been proposed for how mTORC1 controls lipid homeostasis. We show that selective inhibition of mTORC1 signaling in mice, through deletion of the RagC/D guanosine triphosphatase-activating protein folliculin (FLCN), promotes activation of transcription factor E3 (TFE3) in the liver without affecting other mTORC1 targets and protects against NAFLD and NASH. Disease protection is mediated by TFE3, which both induces lipid consumption and suppresses anabolic lipogenesis. TFE3 inhibits lipogenesis by suppressing proteolytic processing and activation of sterol regulatory element-binding protein-1c (SREBP-1c) and by interacting with SREBP-1c on chromatin. Our data reconcile previously conflicting studies and identify selective inhibition of mTORC1 as a potential approach to treat NASH and NAFLD.

Integrated metagenomics and metabolomics analysis illustrates the systemic impact of the gut microbiota on host metabolism after bariatric surgery.

AIM: To explore how bariatric surgery (BS) modified the obesity-associated gut microbiome, the host metabolome, and their interactions in obese Korean patients. MATERIALS AND METHODS: Stool and fasting blood samples were obtained before and 1, 3, 6, and 12 months after BS from 52 patients enrolled in the Korean Obesity Surgical Treatment Study. We analysed the gut microbiome by 16S rRNA gene sequencing and the serum metabolome, including bile acids, by nuclear magnetic resonance spectroscopy and ultrahigh-performance liquid chromatography/triple quadrupole mass spectrometry. RESULTS: Stool metagenomics showed that 27 microbiota were enriched and 14 microbiota were reduced after BS, whereas the abundances and diversity of observed features were increased. The levels of branched-chain amino acids and metabolites of energy metabolism in serum were decreased after surgery, whereas the levels of metabolites related to microbial metabolism, including dimethyl sulphone, glycine, and secondary bile acids, were increased in the serum samples. In addition, we found notable mutual associations among metabolites and gut microbiome changes attributed to BS. CONCLUSIONS: Changes in the gut microbiome community and systemic levels of amino acids and sugars were directly derived from anatomical changes in the gastrointestinal tract after BS. We hypothesized that the observed increases in microbiome-related serum metabolites were a result of complex and indirect changes derived from BS. Ethnic-specific environmental or genetic factors could affect Korean-specific postmetabolic modification in obese patients who undergo BS.

Persistence of the neutralizing antibody response after SARS-CoV-2 infection.

OBJECTIVE: Neutralizing antibodies are among the factors used to measure an individual's immune status for the control of infectious diseases. We aimed to confirm the persistence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) neutralizing antibody levels in patients who had recovered from coronavirus disease 2019 (COVID-19). METHODS: Plasma donors in South Korea who had completely recovered from SARS-CoV-2 infection had follow-up testing to determine the persistence of neutralizing antibodies using a plaque-reduction neutralization test and ELISA. RESULTS: Of the 111 participants-aged 20-29 years, 37/111 (33.3%); 30-39 years, 17/111 (15.3%); 40-49 years, 23/111 (20.7%); 50-59 years, 21/111 (18.9%); 60-65 years, 13/111 (11.7%); male, 43/111 (38.7%); female, 68/111 (61.3%)-66.1% still had neutralizing antibodies approximately 9 months (range 255-302 days) after confirmation of the diagnosis. CONCLUSIONS: In this study we analysed the titre of neutralizing antibodies associated with predicting immune status in individuals with natural infection. Information about the persistence and change in levels of neutralizing antibodies against SARS-CoV-2 can be utilized to provide evidence for developing vaccination schedules for individuals with previous infection.

Integrated landscape of cardiac metabolism in end-stage human nonischemic dilated cardiomyopathy.

Heart failure (HF) is a leading cause of mortality. Failing hearts undergo profound metabolic changes, but a comprehensive evaluation in humans is lacking. We integrate plasma and cardiac tissue metabolomics of 678 metabolites, genome-wide RNA-sequencing, and proteomic studies to examine metabolic status in 87 explanted human hearts from 39 patients with end-stage HF compared with 48 nonfailing donors. We confirm bioenergetic defects in human HF and reveal selective depletion of adenylate purines required for maintaining ATP levels. We observe substantial reductions in fatty acids and acylcarnitines in failing tissue, despite plasma elevations, suggesting defective import of fatty acids into cardiomyocytes. Glucose levels, in contrast, are elevated. Pyruvate dehydrogenase, which gates carbohydrate oxidation, is de-repressed, allowing increased lactate and pyruvate burning. Tricarboxylic acid cycle intermediates are significantly reduced. Finally, bioactive lipids are profoundly reprogrammed, with marked reductions in ceramides and elevations in lysoglycerophospholipids. These data unveil profound metabolic abnormalities in human failing hearts.

Nm23-H1 activator phenylbutenoid dimer exerts cytotoxic effects on metastatic breast cancer cells by inducing mitochondrial dysfunction only under glucose starvation.

Mitochondrial oxidative phosphorylation (OXPHOS) has become an attractive target in anti-cancer studies in recent years. In this study, we found that a small molecule phenylbutenoid dimer NMac1 (Nm23-H1 activator 1), (±)-trans-3-(3,4-dimethoxyphenyl)-4-[(E)-3,4-dimethoxystyryl]cyclohex-1-ene, a previously identified anti-metastatic agent, has novel anti-proliferative effect only under glucose starvation in metastatic breast cancer cells. NMac1 causes significant activation of AMPK by decreasing ATP synthesis, lowers mitochondrial membrane potential (MMP, ΔΨm), and inhibits oxygen consumption rate (OCR) under glucose starvation. These effects of NMac1 are provoked by a consequence of OXPHOS complex I inhibition. Through the structure-activity relationship (SAR) study of NMac1 derivatives, NMac24 was identified as the most effective compound in anti-proliferation. NMac1 and NMac24 effectively suppress cancer cell proliferation in 3D-spheroid in vivo-like models only under glucose starvation. These results suggest that NMac1 and NMac24 have the potential as anti-cancer agents having cytotoxic effects selectively in glucose restricted cells.

Bi-allelic variants in OGDHL cause a neurodevelopmental spectrum disease featuring epilepsy, hearing loss, visual impairment, and ataxia.

The 2-oxoglutarate dehydrogenase-like (OGDHL) protein is a rate-limiting enzyme in the Krebs cycle that plays a pivotal role in mitochondrial metabolism. OGDHL expression is restricted mainly to the brain in humans. Here, we report nine individuals from eight unrelated families carrying bi-allelic variants in OGDHL with a range of neurological and neurodevelopmental phenotypes including epilepsy, hearing loss, visual impairment, gait ataxia, microcephaly, and hypoplastic corpus callosum. The variants include three homozygous missense variants (p.Pro852Ala, p.Arg244Trp, and p.Arg299Gly), three compound heterozygous single-nucleotide variants (p.Arg673Gln/p.Val488Val, p.Phe734Ser/p.Ala327Val, and p.Trp220Cys/p.Asp491Val), one homozygous frameshift variant (p.Cys553Leufs∗16), and one homozygous stop-gain variant (p.Arg440Ter). To support the pathogenicity of the variants, we developed a novel CRISPR-Cas9-mediated tissue-specific knockout with cDNA rescue system for dOgdh, the Drosophila ortholog of human OGDHL. Pan-neuronal knockout of dOgdh led to developmental lethality as well as defects in Krebs cycle metabolism, which was fully rescued by expression of wild-type dOgdh. Studies using the Drosophila system indicate that p.Arg673Gln, p.Phe734Ser, and p.Arg299Gly are severe loss-of-function alleles, leading to developmental lethality, whereas p.Pro852Ala, p.Ala327Val, p.Trp220Cys, p.Asp491Val, and p.Arg244Trp are hypomorphic alleles, causing behavioral defects. Transcript analysis from fibroblasts obtained from the individual carrying the synonymous variant (c.1464T>C [p.Val488Val]) in family 2 showed that the synonymous variant affects splicing of exon 11 in OGDHL. Human neuronal cells with OGDHL knockout exhibited defects in mitochondrial respiration, indicating the essential role of OGDHL in mitochondrial metabolism in humans. Together, our data establish that the bi-allelic variants in OGDHL are pathogenic, leading to a Mendelian neurodevelopmental disease in humans.

Quantitative analysis of m6A RNA modification by LC-MS.

N6-adenosine methylation (m6A) of messenger RNA (mRNA) plays key regulatory roles in gene expression. Accurate measurement of m6A levels is thus critical to understand its dynamic changes in various biological settings. Here, we provide a protocol to quantitate the levels of adenosine and m6A in cellular mRNAs. Using nuclease and phosphatase, we digest mRNA into nucleosides, which are subsequently quantified using liquid chromatography mass spectrometry. For complete details on the use and execution of this protocol, please refer to Cho et al. (2021).

Purine metabolite-based machine learning models for risk prediction, prognosis, and diagnosis of coronary artery disease.

Alterations in xanthine oxidase activity are known to be pathologically influential on coronary artery disease (CAD), but the association between purine-related blood metabolites and CAD has only been partially elucidated. We performed global metabolomics profiling and network analysis on blood samples from the Wonju and Pyeongchang (WP) cohort study (n = 2055) to elucidate the importance of purine related metabolites associated with potential CAD risk. Then, 5 selected serum metabolites were quantified from the WP cohort, Shinchon cohort (n = 259), and Shinchon case control (n = 424) groups to develop machine learning models for 10-year risk prediction, relapse within 10 years and diagnosis of the disease via 100 repeated 5-fold cross-validations of logistic models. The combination of purine metabolite levels or only xanthine levels in blood could be applied for machine learning model development for major adverse cardiac and cerebrovascular event (MACCE, cerebrovascular death, nonfatal myocardial infarction, percutaneous transluminal coronary angioplasty, coronary artery bypass graft, and stroke) risk prediction, relapse of MACCEs among patients with myocardial infarction history and diagnosis of stable CAD. In particular, our research provided initial evidence that blood xanthine and uric acid levels play different roles in the development of machine learning models for primary/secondary prevention or diagnosis of CAD. In this research, we determined that purine-related metabolites in blood are applicable to machine learning model development for CAD risk prediction and diagnosis. Also, our work advances current CAD biomarker discovery strategies mainly relying on clinical features; emphasizes the differential biomarkers in first/secondary prevention or diagnosis studies.

Global Microbiota-Dependent Histone Acetylation Patterns Are Irreversible and Independent of Short Chain Fatty Acids.

BACKGROUND AND AIMS: Although germ-free mice are an indispensable tool in studying the gut microbiome and its effects on host physiology, they are phenotypically different than their conventional counterparts. While antibiotic-mediated microbiota depletion in conventional mice leads to physiologic alterations that often mimic the germ-free state, the degree to which the effects of microbial colonization on the host are reversible is unclear. The gut microbiota produce abundant short chain fatty acids (SCFAs), and previous studies have demonstrated a link between microbial-derived SCFAs and global hepatic histone acetylation in germ-free mice. APPROACH AND RESULTS: We demonstrate that global hepatic histone acetylation states measured by mass spectrometry remained largely unchanged despite loss of luminal and portal vein SCFAs after antibiotic-mediated microbiota depletion. In contrast to stable hepatic histone acetylation states, we see robust hepatic transcriptomic alterations after microbiota depletion. Additionally, neither dietary supplementation with supraphysiologic levels of SCFA nor the induction of hepatocyte proliferation in the absence of microbiota-derived SCFAs led to alterations in global hepatic histone acetylation. CONCLUSIONS: These results suggest that microbiota-dependent landscaping of the hepatic epigenome through global histone acetylation is static in nature, while the hepatic transcriptome is responsive to alterations in the gut microbiota.

Repeated hypoxia exposure induces cognitive dysfunction, brain inflammation, and amyloidß/p-Tau accumulation through reduced brain O-GlcNAcylation in zebrafish.

Repetitive hypoxia (RH) exposure affects the initiation and progression of cognitive dysfunction, but little is known about the mechanisms of hypoxic brain damage. In this study, we show that sublethal RH increased anxiety, impaired learning and memory (L/M), and triggered downregulation of brain levels of glucose and several glucose metabolites in zebrafish, and that supplementation of glucose or glucosamine (GlcN) restored RH-induced L/M impairment. Fear conditioning (FC)-induced brain activation of and PKA/CREB signaling was abrogated by RH, and this effect was reversed by GlcN supplementation. RH was associated with decreased brain O-GlcNAcylation and an increased O-GlcNAcase (OGA) level. RH increased brain inflammation and p-Tau and amyloid ß accumulation, and these effects were suppressed by GlcN. Our observations collectively suggest that changes in O-GlcNAc flux during hypoxic exposure could be an important causal factor for neurodegeneration, and that supplementation of the HBP/O-GlcNAc flux may be a potential novel therapeutic or preventive target for addressing hypoxic brain damage.