Synthetic Enzyme Research Articles

How lignin biosynthesis responds to nitrogen in plants: ascoping review.

Nitrogen (N) plays a critical role in the functioning of key amino acids and synthetic enzymes responsible for the various stages of lignin biosynthesis. However, the precise mechanisms through which N influences lignin biosynthesis have not been fully elucidated. This scoping review explores how lignin biosynthesis responds to N in plants. A systematic search of the literature in several databases was conducted using relevant keywords. Only 44 of the 1842 selected studies contained a range of plant species, experimental conditions, and research approaches. Lignin content, structure, and biosynthetic pathways in response to N are discussed, and possible response mechanisms of lignin under low N are proposed. Among the selected studies, 64.52% of the studies reter to lignin content found a negative correlation between N availability and lignin content. Usually, high N decreases the lignin content, delays cell lignification, increases p-hydroxyphenyl propane (H) monomer content, and regulates lignin synthesis through the expression of key genes (PAL, 4CL, CCR, CAD, COMT, LAC, and POD) encoding miRNAs and transcription factors (e.g., MYB, bHLH). N deficiency enhances lignin synthesis through the accumulation of phenylpropanoids, phenolics, and soluble carbohydrates, and indirect changes in phytohormones, secondary metabolites, etc. This review provides new insights and important references for future studies on the regulation of lignin biosynthesis.

Cerium Vanadate Nanozyme with pH-Dependent Dual Enzymatic Activity for Glioblastoma Targeted Therapy and Postradiotherapy Damage Protection.

Nanocatalytic therapy is an emerging technology that uses synthetic nanoscale enzyme mimics for biomedical treatment. However, in the field of neuroscience, achieving neurological protection while simultaneously killing tumor cells is a technical challenge. Herein, we synthesized a biomimic and translational cerium vanadate (CeVO4) nanozyme for glioblastoma (GBM) therapy and the repair of brain damage after GBM ionizing radiation (IR). This system exhibited pH dependence: it showed potent Superoxide dismutase (SOD) enzyme activity in a neutral environment and Peroxidase (POD) enzyme activity in an acidic environment. In GBM cells, this system acted in lysosomes, causing cellular damage and reactive oxygen species (ROS) accumulation; in neuronal cells, this nanozyme could undergo lysosomal escape and nanozyme aggregation with mitochondria, reversing the mitochondrial damage caused by IR and restoring the expression level of the antiapoptotic BCL-2 protein. Mechanistically, we believe that this distribution difference is related to the specific uptake internalization mechanism and lysosomal repair pathway in neurons, and ultimately led to the dual effect of tumor killing and nerve repair in the in vivo model. In summary, this study provides insight into the repair of brain damage after GBM radiation therapy.

Inhibition of 2-AG hydrolysis alleviates posttraumatic headache attributed to mild traumatic brain injury

BackgroundPosttraumatic headache (PTH) is a common and debilitating symptom following repetitive mild traumatic brain injury (rmTBI), and it mainly resembles a migraine-like phenotype. While modulation of the endocannabinoid system (ECS) is effective in treating TBI and various types of pain including migraine, the role of augmentation of endocannabinoids in treating PTH has not been investigated.MethodsRepetitive mild TBI was induced in male C57BL/6J mice using the non-invasive close-head impact model of engineered rotational acceleration (CHIMERA). Periorbital allodynia was assessed using von Frey filaments and determined by the “Up-Down” method. Immunofluorescence staining was employed to investigate glial cell activation and calcitonin gene-related peptide (CGRP) expression in the trigeminal ganglion (TG) and trigeminal nucleus caudalis (TNC) of the rmTBI mice. Levels of 2-arachidonoyl glycerol (2-AG), anandamide (AEA), and arachidonic acid (AA) in the TG, medulla (including TNC), and periaqueductal gray (PAG) were measured by mass spectrometry. The therapeutic effect of endocannabinoid modulation on PTH was also assessed.ResultsThe rmTBI mice exhibited significantly increased cephalic pain hypersensitivity compared to the sham controls. MJN110, a potent and selective inhibitor of the 2-AG hydrolytic enzyme monoacylglycerol lipase (MAGL), dose-dependently attenuated periorbital allodynia in the rmTBI animals. Administration of CGRP at 0.01 mg/kg reinstated periorbital allodynia in the rmTBI animals on days 33 and 45 post-injury but had no effect in the sham and MJN110 treatment groups. Activation of glial cells along with increased production of CGRP in the TG and TNC at 7 and 14 days post-rmTBI were attenuated by MJN110 treatment. The anti-inflammatory and anti-nociceptive effects of MJN110 were partially mediated by cannabinoid receptor activation, and the pain-suppressive effect of MJN110 was completely blocked by co-administration of DO34, an inhibitor of 2-AG synthase. The levels of 2-AG in TG, TNC and PAG were decreased in TBI animals, significantly elevated and further reduced by the selective inhibitors of 2-AG hydrolytic and synthetic enzymes, respectively.ConclusionEnhancing endogenous levels of 2-AG appears to be an effective strategy for the treatment of PTH by attenuating pain initiation and transmission in the trigeminal pathway and facilitating descending pain inhibitory modulation.

Environmental responsive peroxidase-like activity of MoS2@halloysite nanotubes mediated by piezoelectric effect

Nanozymes, as a class of synthetic enzymes, have the characteristics of abundant raw materials and powerful environmental adaptability, potentially serving as substitutes for natural enzymes. Herein, the MoS2 nanosheets were anchored on the surface of alkali activated halloysite nanotubes by utilizing a facile hydrothermal process, resulting in the formation of MoS2@halloysite (MoS2@HNTs) core-shell nanocomposites. The catalytic effect of material on peroxidase under the mechanical stress of applied ultrasonic vibration was systematically investigated with 3,3′,5,5′-tetramethylbenzidine (TMB) as the substrate for chromogenic reaction. The results demonstrated that the established piezoelectric polarization effect generated by MoS2 with asymmetric crystal structure under mechanical force can promote the in-situ coloration of TMB. Concretely, MoS2@HNTs possessing higher Michaels constant (3.42 mmol L-1) and reaction velocity (3.16 × 10–6 mol L-1 min-1) exhibited enhanced peroxidase-like activity compared to pristine MoS2 microspheres. This may be attributed to the fact that halloysite dispersed the MoS2 nanosheets, exposing more reactive sites, and the nanocomposites produced more pronounced structural deformation under mechanical stress. The detailed experiments and theoretical calculation have elucidated the structure-activity relationship and microscopic mechanism among the microstructures, piezoelectric polarization effects and peroxidase catalytic effects of materials. This work provides an advanced prototype for the research of environmental responsive enzyme-like catalytic effects of mineral-based nanozymes with the regulation of external environmental factors.

Retinoic acid-mediated homeostatic plasticity in the nucleus accumbens core contributes to incubation of cocaine craving.

Incubation of cocaine craving refers to the progressive intensification of cue-induced craving during abstinence from cocaine self-administration. We showed previously that homomeric GluA1 Ca2+-permeable AMPARs (CP-AMPAR) accumulate in excitatory synapses of nucleus accumbens core (NAcc) medium spiny neurons (MSN) after ∼1 month of abstinence and thereafter their activation is required for expression of incubation. Therefore, it is important to understand mechanisms underlying CP-AMPAR plasticity. We hypothesize that CP-AMPAR upregulation represents a retinoic acid (RA)-dependent form of homeostatic plasticity, previously described in other brain regions, in which a reduction in neuronal activity disinhibits RA synthesis, leading to GluA1 translation and CP-AMPAR synaptic insertion. We tested this using viral vectors to bidirectionally manipulate RA signaling in NAcc during abstinence following extended-access cocaine self-administration. We used shRNA targeted to the RA degradative enzyme Cyp26b1 to increase RA signaling. This treatment accelerated incubation; rats expressed incubation on abstinence day (AD) 15, when it is not yet detected in control rats. It also accelerated CP-AMPAR synaptic insertion measured with slice physiology. CP-AMPARs were detected in Cyp26b1 shRNA-expressing MSN, but not control MSN, on AD15-18. Next, we used shRNA targeted to the major RA synthetic enzyme Aldh1a1 to reduce RA signaling. In MSN expressing Aldh1a1 shRNA, synaptic CP-AMPARs were reduced in late withdrawal (AD42-60) compared to controls. However, we did not detect an effect of this manipulation on incubated cocaine seeking (AD40). These findings support the hypothesis that increased RA signaling during abstinence contributes to CP-AMPAR accumulation and incubation of cocaine craving.

Systemic strategies for cytokinin biosynthesis and catabolism in Arabidopsis roots and leaves under prolonged ammonium nutrition

Cytokinins are growth-regulating plant hormones that are considered to adjust plant development under environmental stresses. During sole ammonium nutrition, a condition known to induce growth retardation of plants, altered cytokinin content can contribute to the characteristic ammonium toxicity syndrome. To understand the metabolic changes in cytokinin pools, cytokinin biosynthesis and degradation were analyzed in the leaves and roots of mature Arabidopsis plants. We found that in leaves of ammonium-grown plants, despite induction of biosynthesis on the expression level, there was no active cytokinin build-up because they were effectively routed toward their downstream catabolites. In roots, cytokinin conjugation was also induced, together with low expression of major synthetic enzymes, resulting in a decreased content of the trans-zeatin form under ammonium conditions. Based on these results, we hypothesized that in leaves and roots, cytokinin turnover is the major regulator of the cytokinin pool and does not allow active cytokinins to accumulate. A potent negative-regulator of root development is trans-zeatin, therefore its low level in mature root tissues of ammonium-grown plants may be responsible for occurrence of a wide root system. Additionally, specific cytokinin enhancement in apical root tips may evoke a short root phenotype in plants under ammonium conditions. The ability to flexibly regulate cytokinin metabolism and distribution in root and shoot tissues can contribute to adjusting plant development in response to ammonium stress.

Tenebrio molitor Larvae Feeding Strategy to Degrade Polypropylene Components from Disposable Masks

<p><strong>Abstract.</strong>The surge in mask consumption during the COVID-19 pandemic led to the widespread use of disposable polypropylene masks for protection. However, the accumulation of used masks poses environmental challenges due to the slow degradation of polypropylene. Here, we investigate the potential of <em>Tenebrio molitor</em> larvae in degrading polypropylene masks, exploiting their synthetic polymer-breaking enzymes and associated microflora. In this study, we implemented various feeding strategies and established specific feed compositions to assess <em>T. molitor</em> larvae's consumption behavior towards polypropylene masks. Over a 21-day observation period, we noted a consumption rate of 0.4% of masks, with a 7.5% mortality rate among the larvae. The average daily consumption rate was 0.201 grams, resulting in a 2.3% increase in larval weight and the production of 0.4635 grams of feces. Our findings highlight the potential of <em>T. molitor</em> larvae as effective mask degraders. Optimizing cultivation conditions and feeding strategies may further enhance microbial diversity, potentially introducing more polypropylene degraders within <em>T. molitor</em>, thereby expediting mask degradation. This study emphasizes the promising role of <em>T. molitor</em> larvae in addressing the environmental challenges posed by the accumulation of polypropylene masks.</p><p><strong>Keywords: </strong></p><p>Mask, Degrade, <em>Tenebrio molitor</em>, Microflora, Polypropylene</p>

Exploring the effect of prolonged fasting on kynurenine pathway metabolites and stress markers in healthy male individuals.

Prolonged fasting triggers a stress response within the human body. Our objective was to investigate the impact of prolonged fasting, in conjunction with stress, on kynurenine pathway metabolites. Healthy males were divided into fasting group (zero-calorie-restriction) for 6 days (FAST, n = 14), and control group (CON, n = 10). Blood and saliva samples were collected at baseline, Day 2, Day 4, Day 6 during fasting period, and 1 week after resuming regular diet. Plasma levels of kynurenine pathway metabolites were measured using ultra-performance liquid chromatography-mass spectrometry (UPLC-MS/MS). Plasma and salivary samples were analyzed for stress markers. A pronounced activation of the kynurenine pathway in individuals on FAST trial was revealed. Concentrations of picolinic acid (PIC), kynurenic acid (KYNA) and 3-hydroxykynurenine (3-HK) were significantly increased, with peak levels observed on Day 6 (P < 0.0001). Conversely, concentrations of tryptophan (TRP) and quinolinic acid (QUIN) decreased (P < 0.0001), while kynurenine (KYN) and nicotinamide (NAM) levels remained stable. Cortisol and noradrenaline concentrations remained unchanged. However, adrenaline levels significantly increased on Day 4 within FAST compared to CON (P = 0.005). Notably, all deviations in kynurenine pathway metabolite levels returned to baseline values upon resuming regular diet following the 6-day fasting regimen, even when weight and BMI parameters were not restored. Extended fasting over 6 days induces the kynurenine pathway and has minimal effects on stress markers. Restoration of metabolite concentrations upon regular feeding implies rapid adaptation of the kynurenine pathway synthetic enzymes to maintain homeostasis when faced with perturbations.

Serum Hydroxysteroid (17beta) dehydrogenase 1 concentration in pregnant women correlates with pregnancy-associated plasma protein a but does not serve as an independent marker for preeclampsia.

Hydroxysteroid (17beta) dehydrogenase 1 (HSD17B1) is a steroid synthetic enzyme expressed in ovarian granulosa cells and placental syncytiotrophoblasts. Here, HSD17B1 serum concentration was measured with a validated immuno assay during pregnancy at three time points (12-14, 18-20 and 26-28weeks of gestation). The concentration increased 2.5-fold (p < 0.0001) and 1.7-fold (p = 0.0019) during the follow-up period for control women and women who later developed preeclampsia (PE), respectively, and a significant difference was observed at weeks 26-28 (p = 0.0266). HSD17B1 concentration at all the three time points positively correlated with serum PAPPA measured at the first time point (first time point r = 0.38, p = 1.1x10-10; second time point r = 0.27, p = 5.9x10-6 and third timepoint r = 0.26, p = 2.3x10-5). No correlation was observed between HSD17B1 and placental growth factor (PLGF). Serum HSD17B1, furthermore, negatively correlated with the mother's weight and body mass index (BMI), mirroring the pattern observed for PAPPA. The univariable logistic regression identified a weak association between HSD17B1 at 26-28weeks and later development of PE (P = 0.04). Also, the best multivariable model obtained using penalized logistic regression with stable iterative variable selection at 26-28weeks included HSD17B1, together with PLGF, PAPPA and the mother's BMI. While the area under the ROC curve of the model was higher than that of the adjusted PLGF, the difference was not statistically significant. In summary, the serum concentration of HSD17B1 correlated with PAPPA, another protein expressed in syncytiotrophoblasts, and with mother's weight and BMI but could not be considered as an independent marker for PE.

Bidirectionally regulated synthetic ferrocene-based aminal-linked porous organic polymer artificial enzyme towards photothermal-amplified synergistic antibacterial and wound healing therapy

Development of hetero-atom rich porous organic polymers (POPs) in facile and easy accessible methods are of significant importance to broad application potentials and enrich diversity of such materials. Here, a bidirectional adjustment strategy, starting with amino and aldehyde monomers, concurrently, was used for the rational preparation of N-rich aminal-linked POPs with customized structure and function. Five novel ferrocene-based aminal-linked POPs, were facilely fabricated via the one-pot catalyst-free Schiff base polycondensation between the 1,1′-Ferrocene dicarboxaldehyde and different types of triazine-bearing monomers with diverse geometrical features and functions (Porphyrin, cationic viologen, Ferrocene, 1,4,7,10-tetraazacyclododecane, and benzyl). The concurrent introduction of Ferrocene (redox-active) and triazine-Porphyrin (photoactive) endowed remarkable mimicking peroxidase-like activity and excellent photothermal and photodynamic activity with Fc-TDPP, which could be used as a broad spectrum fungicide, exerting photothermal enhanced photodynamic and enzyme antibacterial therapy. Notably, in vitro and in vivo experiments confirmed Fc-TDPP could not only kill S. aureus and E. coli quickly and efficiently, but also significantly accelerate the repairing of open wounds with S. aureus-infection. The as-proposed strategy are available for the low-cost constructing N-rich POPs with specific structure and functions targeted for wide potential applications in various fields.

Unraveling the nexus of NAD+ metabolism and diabetic kidney disease: insights from murine models and human data.

Nicotinamide adenine dinucleotide (NAD+) is a critical coenzyme involved in kidney disease, yet its regulation in diabetic kidney disease (DKD) remains inadequately understood. Therefore, we investigated the changes of NAD+ levels in DKD and the underlying mechanism. Alternations of NAD+ levels and its biosynthesis enzymes were detected in kidneys from streptozotocin-induced diabetic mouse model by real-time PCR and immunoblot. The distribution of NAD+ de novo synthetic enzymes was explored via immunohistochemical study. NAD+ de novo synthetic metabolite was measured by LC-MS. Human data from NephroSeq were analyzed to verify our findings. The study showed that NAD+ levels were decreased in diabetic kidneys. Both mRNA and protein levels of kynurenine 3-monooxygenase (KMO) in NAD+ de novo synthesis pathway were decreased, while NAD+ synthetic enzymes in salvage pathway and NAD+ consuming enzymes remained unchanged. Further analysis of human data suggested KMO, primarily expressed in the proximal tubules shown by our immunohistochemical staining, was consistently downregulated in human diabetic kidneys. Our study demonstrated KMO of NAD+ de novo synthesis pathway was decreased in diabetic kidney and might be responsible for NAD+ reduction in diabetic kidneys, offering valuable insights into complex regulatory mechanisms of NAD+ in DKD.

Dietary glycine supplementation enhances syntheses of creatine and glutathione by tissues of hybrid striped bass (Morone saxatilis ♀ × Morone chrysops ♂) fed soybean meal-based diets

BackgroundWe recently reported that supplementing glycine to soybean meal-based diets is necessary for the optimum growth of 5- to 40-g (Phase-I) and 110- to 240-g (Phase-II) hybrid striped bass (HSB), as well as their intestinal health. Although glycine serves as an essential substrate for syntheses of creatine and glutathione (GSH) in mammals (e.g., pigs), little is known about these metabolic pathways or their nutritional regulation in fish. This study tested the hypothesis that glycine supplementation enhances the activities of creatine- and GSH-forming enzymes as well as creatine and GSH availabilities in tissues of hybrid striped bass (HSB; Morone saxatilis♀ × Morone chrysops♂).MethodsPhase-I and Phase-II HSB were fed a soybean meal-based diet supplemented with 0%, 1%, or 2% glycine for 8 weeks. At the end of the 56-d feeding, tissues (liver, intestine, skeletal muscle, kidneys, and pancreas) were collected for biochemical analyses.ResultsIn contrast to terrestrial mammals and birds, creatine synthesis occurred primarily in skeletal muscle from all HSB. The liver was most active in GSH synthesis among the HSB tissues studied. In Phase-I HSB, supplementation with 1% or 2% glycine increased (P < 0.05) concentrations of intramuscular creatine (15%–19%) and hepatic GSH (8%–11%), while reducing (P < 0.05) hepatic GSH sulfide (GSSG)/GSH ratios by 14%–15%, compared with the 0-glycine group; there were no differences (P > 0.05) in these variables between the 1% and 2% glycine groups. In Phase-II HSB, supplementation with 1% and 2% glycine increased (P < 0.05) concentrations of creatine and GSH in the muscle (15%–27%) and liver (11%–20%) in a dose-dependent manner, with reduced ratios of hepatic GSSG/GSH in the 1% or 2% glycine group. In all HSB, supplementation with 1% and 2% glycine dose-dependently increased (P < 0.05) activities of intramuscular arginine:glycine amidinotransferase (22%–41%) and hepatic γ-glutamylcysteine synthetase (17%–37%), with elevated activities of intramuscular guanidinoacetate methyltransferase and hepatic GSH synthetase and GSH reductase in the 1% or 2% glycine group. Glycine supplementation also increased (P < 0.05) concentrations of creatine and activities of its synthetic enzymes in tail kidneys and pancreas, and concentrations of GSH and activities of its synthetic enzymes in the proximal intestine.ConclusionsSkeletal muscle and liver are the major organs for creatine and GSH syntheses in HSB, respectively. Dietary glycine intake regulates creatine and GSH syntheses by both Phase-I and Phase-II HSB in a tissue-specific manner. Based on the metabolic data, glycine is a conditionally essential amino acid for the growing fish.

Quercetin Induces Mitochondrial Apoptosis and Downregulates Ganglioside GD3 Expression in Melanoma Cells.

Malignant melanoma represents a form of skin cancer characterized by a bleak prognosis and heightened resistance to traditional therapies. Quercetin has demonstrated notable anti-carcinogenic, anti-inflammatory, anti-oxidant, and pharmacological effects across various cancer types. However, the intricate relationship between quercetin's anti-cancer properties and ganglioside expression in melanoma remains incompletely understood. In this study, quercetin manifests specific anti-proliferative, anti-migratory, and cell-cycle arrest effects, inducing mitochondrial dysfunction and apoptosis in two melanoma cancer cell lines. This positions quercetin as a promising candidate for treating malignant melanoma. Moreover, our investigation indicates that quercetin significantly reduces the expression levels of ganglioside GD3 and its synthetic enzyme. Notably, this reduction is achieved through the inhibition of the FAK/paxillin/Akt signaling pathway, which plays a crucial role in cancer development. Taken together, our findings suggest that quercetin may be a potent anti-cancer drug candidate for the treatment of malignant melanoma.

Sphingomyelin is involved in regulating UCP1-mediated nonshivering thermogenesis

Adipogenesis is one of the major mechanisms for adipose tissue expansion, during which spindle-shaped mesenchymal stem cells commit to the fate of adipocyte precursors and differentiate into round-shaped fat-laden adipocytes. Here, we investigated the lipidomic profile dynamics of ex vivo-differentiated brown and white adipocytes derived from the stromal vascular fractions of interscapular brown (iBAT) and inguinal white adipose tissues. We showed that sphingomyelin was specifically enriched in terminally differentiated brown adipocytes, but not white adipocytes. In line with this, freshly isolated adipocytes of iBAT showed higher sphingomyelin content than those of inguinal white adipose tissue. Upon cold exposure, sphingomyelin abundance in iBAT gradually decreased in parallel with reduced sphingomyelin synthase 1 protein levels. Cold-exposed animals treated with an inhibitor of sphingomyelin hydrolases failed to maintain core body temperature and showed reduced oxygen consumption and iBAT UCP1 levels. Conversely, blockade of sphingomyelin synthetic enzymes resulted in enhanced nonshivering thermogenesis, reflected by elevated body temperature and UCP1 levels. Taken together, our results uncovered a relation between sphingomyelin abundance and fine-tuning of UCP1-mediated nonshivering thermogenesis.

Ovarian PERK/NRF2/CX43/StAR/progesterone pathway activation mediates female reproductive dysfunction induced by cold exposure

Ambient air temperature is a key factor affecting human health. Female reproductive disorders are representative health risk events under low temperature. However, the mechanism involving in cold-induced female reproductive disorders remains largely unknown. Female mice were intermittently exposed to cold conditions (4 °C) to address the health risk of low temperature on female reproductive system. Primary granulosa cells (GCs) were prepared and cultured under low temperature (35 °C) or exposed to β3-adrenoreceptor agonist, isoproterenol, to mimic the condition of cold exposure. Western-blot, RT-PCR, co-IP, ELISA, pharmacological inhibition or siRNA-mediated knockdown of target gene were performed to investigate the possible role of hormones, gap conjunction proteins, and ER stress sensor protein in regulating female reproductive disorders under cold exposure. Cold exposure induced estrous cycle disorder and follicular dysplasia in female mice, accompanying with abnormal upregulation of progesterone and its synthetic rate-limiting enzyme, StAR, in the ovarian granulosa cells. Under the same conditions, an increase in connexin 43 (CX43) expressions in the GCs was also observed, which contributed to elevated progesterone levels in the ovary. Moreover, ER stress sensor protein, PERK, was activated in the ovarian GCs after cold exposure, leading to the upregulation of downstream NRF2-dependent CX43 transcription and aberrant increase in progesterone synthesis. Most importantly, blocking PERK expression in vivo significantly inhibited NRF2/CX43/StAR/progesterone pathway activation in the ovary and efficiently rescued the prolongation of estrous cycle and the increase in follicular atresia of the female mice induced by cold stress. We have elucidated the mechanism of ovarian PERK/NRF2/CX43/StAR/progesterone pathway activation in mediating female reproductive disorder under cold exposure. Targeting PERK might be helpful for maintaining female reproductive health under cold conditions.

Community dynamics and metagenomic analyses reveal Bacteroidota's role in widespread enzymatic Fucus vesiculosus cell wall degradation

Enzymatic degradation of algae cell wall carbohydrates by microorganisms is under increasing investigation as marine organic matter gains more value as a sustainable resource. The fate of carbon in the marine ecosystem is in part driven by these degradation processes. In this study, we observe the microbiome dynamics of the macroalga Fucus vesiculosus in 25-day-enrichment cultures resulting in partial degradation of the brown algae. Microbial community analyses revealed the phylum Pseudomonadota as the main bacterial fraction dominated by the genera Marinomonas and Vibrio. More importantly, a metagenome-based Hidden Markov model for specific glycosyl hydrolyses and sulphatases identified Bacteroidota as the phylum with the highest potential for cell wall degradation, contrary to their low abundance. For experimental verification, we cloned, expressed, and biochemically characterised two α-L-fucosidases, FUJM18 and FUJM20. While protein structure predictions suggest the highest similarity to a Bacillota origin, protein–protein blasts solely showed weak similarities to defined Bacteroidota proteins. Both enzymes were remarkably active at elevated temperatures and are the basis for a potential synthetic enzyme cocktail for large-scale algal destruction.

Increased Farnesoid X Receptor agonism in frontal cortex is associated with neuronal loss in a pig model of pediatric non-alcoholic fatty liver disease

Clinical studies suggest a link between non-alcoholic fatty liver disease (NAFLD) and neurodegeneration, but the mechanisms connecting both pathologies remain unknown. Rodent models of liver failure have shown neurological decline to be associated with increased bile acid (BA) levels and BA-activated farnesoid X receptor (FXR) signaling in the brain, which may disrupt brain’s cholesterol metabolism and promote neuronal death. We have previously established a pediatric animal model of NAFLD by feeding juvenile Iberian pigs a diet high in fat and fructose (HFF) for 10 weeks. The aim of this study was to determine whether BAs and FXR gene expression were increased in the frontal cortex (FC) of NAFLD pigs, and whether these changes were associated with neuronal loss. Eighteen 15-day-old Iberian pigs were assigned to receive for 10 weeks either a control (CON) or a HFF diet. FC was collected for immunohistochemistry, metabolomics, and transcriptomics analyses. Functional enrichment analyses were performed on differentially expressed genes to identify Gene Ontology (GO) terms using the Database for Annotation, Visualization, and Integrated Discovery. All HFF-fed pigs developed NAFLD. Immunostaining of mature neurons with NeuN was lower in FC of HFF compared with CON (P ≤ 0.05), whereas total BA levels increased (P ≤ 0.05) in FC of HFF-fed pigs. Brain levels of cholic and conjugated deoxycholic acids, which are FXR agonists, increased ( P ≤ 0.05) in HFF compared with CON. Conversely, tauroursodeoxycholic acid, which has strong FXR-antagonistic effect and has been shown to exert neuroprotective functions, was decreased (P ≤ 0.001) in HFF and was positively correlated with NeuN staining intensity (R2 = 0.623; P ≤ 0.001). Expression of FC genes encoding FXR, BA synthetic enzymes sterol 24- and 27-hydroxylases, and BA transporters Na+-taurocholate cotransporting polypeptide, organic anion transporting polypeptide, and organic solute transporters alpha and beta did not differ between groups. GO terms associated with Wnt/β-catenin pathway, which promotes neuronal survival and neurogenesis, were downregulated in HFF-fed pigs ( P ≤ 0.05), whereas mitochondrial respiratory chain complex and mitochondrion increased in HFF compared with CON ( P ≤ 0.01). In conclusion, increased BA levels and FXR agonism in frontal cortex of NAFLD pigs was associated with dysregulated Wnt/β-catenin signaling pathway and neuronal loss. California State University Agriculture Research Institute (grants 58873 and 58913), California Polytechnic State University internal funding programs Baker/Koob, RSCA, Frost, BiOWiSH Technologies, Hilmar Ingredients, and Acorn Seekers. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Angiotensin-(1-7) Mas Receptors are Highly Colocalized to GABAergic Proopiomelanocortin Neurons in the Arcuate Nucleus of the Hypothalamus

Previous studies from our laboratory have shown that circulating levels of angiotensin (Ang)-(1-7), a protective hormone of the renin-angiotensin system, are greatly reduced in obese hypertensive mice. Additionally, restoration of this hormone reduces cardiovascular sympathetic tone and lowers blood pressure in this model suggesting a central mechanism of action. In support of this, our recent data show that the sympatho-inhibitory and blood pressure lowering effects of Ang-(1-7) involve activation of mas receptors (masR) within the arcuate nucleus of the hypothalamus (ARC). More specifically, we have found that masR are highly colocalized to proopiomelanocortin (POMC) neurons in the ARC. Due to the heterogeneous nature of POMC neuron subtypes, we wanted to explore the neurotransmitter phenotype of these POMCmasR neurons. We hypothesized that due to the blood pressure lowering effects of Ang-(1-7), POMCmasR are likely colocalized to inhibitory GABAergic neurons. To test this, we performed RNAscope in-situ hybridization in male C57Bl/6J mice after twelve weeks of either a 60% high fat diet (HFD) or matched control diet (n=12-18/group). We used RNAscope to colocalize expression of POMC, masR, and the vesicular GABA transporter, Vgat, mRNA transcripts within the ARC. Colocalization of POMCmasR and Vgat was quantified and percent-colocalization compared between control and HFD groups. We found that POMCmasR are highly colocalized with the GABAergic marker, Vgat, to a similar extent in control and HFD groups (84±4 vs. 90±2% of neurons, respectively; p=0.294 unpaired t-test). The population of POMC neurons that did not express masR also did not colocalize with Vgat. As an initial step to determine if masR modulates GABAergic signaling in the ARC, we assessed gene expression of glutamate decarboxylase 2 (Gad2; a GABA synthetic enzyme) in the ARC following chronic six-week treatment with systemic Ang-(1-7) versus saline infusion in male mice fed a control diet versus HFD (n=9-13/group). We found that Ang-(1-7) increases ARC Gad2 mRNA in HFD mice (1.03±0.09 control diet vs. 0.93±0.07 HFD vs. 1.23±0.07 HFD plus Ang-(1-7); p=0.023 one-way ANOVA). Supporting specificity of these actions, Ang-(1-7) did not alter POMC mRNA in the ARC. These overall data suggest that masR primarily localize to GABA-expressing POMC neurons in the ARC, and Ang-(1-7) may directly modulate GABA synthesis pathways in this brain region. Further studies are needed to elucidate the functional importance of these ARC POMC GABAergic neurocircuits to the depressor effects of Ang-(1-7) in obesity. Funding: NIH R01 HL156986. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Trimethylamine N-oxide ameliorates hepatic damage including reduction of hepatic bile acids and cholesterol in Fxr-null mice

There are conflicting animal experiments on the effect of trimethylamine N-oxide (TMAO), the dietary metabolite, on non-alcoholic fatty liver disease (NAFLD). This study aims to determine the effect of TMAO on NAFLD. A diet containing 0.3% TMAO was fed to farnesoid X receptor (Fxr)-null mice, a model of NAFLD, for 13 weeks. Fxr-null mice fed TMAO showed significant reductions in liver damage markers but not wild-type mice. Hepatic bile acid and cholesterol levels were significantly decreased, and triacylglycerol levels tended to decrease in TMAO-fed Fxr-null mice. Changes in mRNA levels of hepatic bile acid and cholesterol transporters and synthetic enzymes were observed, which could explain the decreased hepatic bile acid and cholesterol levels in Fxr-null mice given the TMAO diet but not in the wild-type mice. These results suggest that TMAO intake ameliorates liver damage in Fxr-null mice, further altering bile acid/cholesterol metabolism in an FXR-independent manner.

Signaling Ligand Heterogeneities in the Peduncle Complex of the Cephalopod Mollusc Octopus bimaculoides

Introduction: The octopus peduncle complex is an agglomeration of neural structures with remarkably diverse functional roles. The complex rests on the optic tract, between the optic lobe and the central brain, and comprises the peduncle lobe proper, the olfactory lobe, and the optic gland. The peduncle lobe regulates visuomotor behaviors, the optic glands control sexual maturation and maternal death, and the olfactory lobe is thought to receive input from the olfactory organ. Recent transcriptomic and metabolomic studies have identified candidate peptide and steroid ligands in the Octopus bimaculoides optic gland. Methods: With gene expression for these ligands and their biosynthetic enzymes, we show that optic gland neurochemistry extends beyond the traditional optic gland secretory tissue and into lobular territories. Results: A key finding is that the classically defined olfactory lobe is itself a heterogeneous territory and includes steroidogenic territories that overlap with cells expressing molluscan neuropeptides and the synthetic enzyme dopamine beta-hydroxylase. Conclusion: Our study reveals the neurochemical landscape of the octopus peduncle complex, highlighting the unexpected overlap between traditionally defined regions.