REVIEW | doi:10.20944/preprints202101.0517.v1
Subject: Life Sciences, Biochemistry Keywords: Gram-negative bacterial; Metabolite transporter; pathways; metabolic engineering approaches
Online: 25 January 2021 (15:49:13 CET)
Metabolite transport across cellular membranes is a key feature of living organisms. Specialized proteins or protein complexes mediate such transport processes and are accessible to genetic engineering approaches. This special issue will reflect on the different transport between cellular compartments. It will provide an overview about different transporter classes and metabolic engineering approaches in different organisms ranging from Bacteria to Eukarya. The transport mechanisms energetics of these compounds were thought little of, and most consideration was given to the designing of metabolic pathways. Gram-negative microbes discharge a wide scope of proteins whose capacities incorporate biogenesis of organelles, for example, pilli and flagella, supplement securing, destructiveness, and efflux of medications and different poisons. Six particular emission frameworks have been appeared to intervene protein send out through the inward and external layers of Gram-negative microbes. These pathways are exceptionally monitored all through the Gram-negative bacterial species. In Gram-positive microscopic organisms, discharged proteins are usually moved across the single layer by the Sec pathway or the two-arginine (Tat) pathway. Recently efforts focused on transporter and metabolite engineering, visualize the improvement and enhancement of microbial cell to pass such metabolites these metabolite carrier proteins are inserted into the inner membrane of mitochondria across the inner membrane, specialized carrier proteins are necessary that mediate the transport into and out of the mitochondrial matrix. Two main strategies for metabolic engineering in plants: the introduction of genes encoding new enzymes and the use of TFs controlling specialized metabolic pathways
ARTICLE | doi:10.20944/preprints202202.0249.v1
Subject: Life Sciences, Molecular Biology Keywords: HIV Nef; neurotoxicity; inflammatory cytokines; kynurenine metabolite
Online: 21 February 2022 (10:00:10 CET)
HIV-1 Nef is a multifunctional protein with well-known lethal properties. HIV infects various cells from the brain compartment and expressed nef is responsible for developing neuropathogenic potential. HIV-infected glial cells express nefvirotoxinand stimulate the cascade of various pathways to activate uninfected cells to release neurotoxic elements damaging cells themselves. A lot of genetic variabilities of this protein have been reported from patients with HIV-associated neurocognitive disorders. To determine the neurotoxic potential of subtype-specific nef plasmids and nef plasmids of clinical samples with and without HAND were transfected in normal human astrocytes (NHA) and monocyte-derived macrophages (MDM) using nef-pCMV-HA plasmid constructs. Supernatants from subtype-specific Nef plasmids indicated the upregulation of proinflammatory cytokines. The induced expression might be due to the nef genetic variability or variations in the transfection efficiency and expression levels of nef.The mRNA expression of IL-6, IP-10, and TNF-α indicated upregulation of 5.0-fold in NHA and 3-fold in MDM with respect to empty vector control transfection. Further, the kynurenine metabolites were also assessed from culture supernatants of NHA and MDM indicating the upregulation of IDO and KYNU in NHA by 3.0-fold and 3.2-fold in MDM.The expression levels of nef and cytokines at the translational level were confirmed by western blotting and bio-plex Pro cytokine estimation assay respectively along with controls expressing green fluorescent protein (GFP).The oxidative stress was also found to be elevated as compared to control cells as determined by the estimation of nitric oxide from the culture supernatant to confirm the neurotoxic potential of HIV nef plasmids. The downregulation in the levels of cytokines, as well as kynurenine metabolites, was observed in culture supernatants after blocking the expression of nef using HIV nef siRNA. Phylogenetic analysis of Nef sequences indicated subtype C predominance except one sequence showing the partial sequence of HIV-1 subtype B sequence forming BC recombinantThe upregulation in the cytokine and pathway-specific metabolites might be linked with the neurotoxic potential of HIV-1 Nef leading to neuropathogenesis. In conclusion, the variation in the transfection efficiency, nef expression levels, and the genetic variability of Nef might be responsible for upregulating the expression levels of cytokines and kynurenine metabolites in astrocytes and MDM.
Subject: Medicine & Pharmacology, Pharmacology & Toxicology Keywords: Cannabis; Metabolite; Principal Component Analysis; Random Forest
Online: 5 September 2020 (07:51:50 CEST)
The many strains of Cannabis spp. are associated with many effects on users and contain many different potentially psychoactive metabolites, but the links between metabolite profiles and user effects are unclear. Here we take a statistical approach to linking cause (i.e. metabolites) to effects in Cannabis spp. through the prism of strains, using quantitative data for metabolite composition and user effects. We find that species (indica vs. sativa) explains <2% of the variability in metabolite profiles, while strain explains 1/3 of variability, indicating species is nonindicative of metabolite composition, while strain is approximately indicative. Using random forests we generate a table of potential metabolite-effect links. We also find that effect-weighted metabolite composition can effectively be described in terms of four values representing the concentrations of pairs or triplets of particular compounds.
ARTICLE | doi:10.20944/preprints201906.0310.v1
Subject: Life Sciences, Microbiology Keywords: cyanobacteria; secondary metabolite; genome mining; molecular networking
Online: 30 June 2019 (10:42:22 CEST)
Cyanobacteria are an ancient lineage of slow-growing photosynthetic bacteria and a proliﬁc source of natural products with diverse chemical structures and potent biological activities and toxicities. The chemical identiﬁcation of these compounds remains a major bottleneck. Strategies that can prioritize the most proliﬁc strains and novel compounds are of great interest. Here, we combine chemical analysis and genomics to investigate the chemodiversity of secondary metabolites based on their pattern of distribution within some cyanobacteria. Planktothrix being a cyanobacterial genus known to form blooms worldwide and to produce a broad spectrum of toxins and other bioactive compounds, we applied this combined approach on four closely related strains of Planktothrix. The chemical diversity of the metabolites produced by the four strains was evaluated using an untargeted metabolomics strategy with high-resolution LC-MS. Metabolite proﬁles were correlated with the potential of metabolite production identified by genomics for the different strains. Although, the Planktothrix strains present a global similarity in term biosynthetic cluster gene for microcystin, aeruginosin and prenylagaramide for example, we found remarkable strain-specific chemo-diversity. Only few of the chemical features were common to the four studied strains. Additionally, the MS/MS data were analyzed using Global Natural Products Social Molecular Networking (GNPS) to identify molecular families of the same biosynthetic origin. In conclusion, we present an efﬁcient integrative strategy for elucidating the chemical diversity of a given genus and link the data obtained from analytical chemistry to biosynthetic genes of cyanobacteria.
ARTICLE | doi:10.20944/preprints201810.0287.v1
Subject: Life Sciences, Other Keywords: exercise; polyphenol; metabolite; Hippurate; intestinal tract; colon
Online: 15 October 2018 (07:39:26 CEST)
Using a randomized, double-blinded, placebo-controlled, parallel group design, this investigation determined if the combination of 2-weeks flavonoid supplementation (329 mg/day, quercetin, anthocyanins, flavan-3-ols mixture) and a 45-minute walking bout (62.2±0.9% VO2max) enhanced the translocation of gut-derived phenolics into circulation in a group of walkers (N = 77). The walkers (flavonoid, placebo groups) were randomized to either sit or walk briskly on treadmills for 45 minutes (thus four groups: placebo-sit, placebo-walk, flavonoid-sit, flavonoid-walk). A comparator group of runners (N = 19) ingested a double flavonoid dose for 2 weeks (658 mg/day) and ran for 2.5 h (69.2±1.2% VO2max). Four blood samples were collected (pre- and post-supplementation, immediately-post- and 24-h post-exercise/rest). Of the 76 metabolites detected in this targeted analysis, 15 increased after the 2.5-h run, and when grouped were also elevated post-exercise (versus placebo-sit) for the placebo- and flavonoid-walking groups (P < 0.05). A secondary analysis showed that pre-study plasma concentrations of gut-derived phenolics in the runners were 40% higher compared to walkers (P = 0.031). These data indicate that acute exercise bouts (brisk walking, intensive running) are linked to an increased translocation of gut-derived phenolics into circulation, an effect that is amplified when combined with a 2-week period of increased flavonoid intake or chronic training as a runner.
REVIEW | doi:10.20944/preprints201805.0214.v1
Subject: Life Sciences, Microbiology Keywords: Streptomyces; polyketides; secondary metabolite; polyketide synthases (PKSs)
Online: 15 May 2018 (08:58:00 CEST)
Polyketides are large group of secondary metabolites that have notable variety in their structure and function. Polyketides exhibit a wide range of bioactivities such as antibacterial, antifungal, anticancer, antiviral, immune-suppressing, anti-cholesterol and anti-inflammatory activity. Naturally, they are found in bacteria, fungi, plants, protists, insects, mollusks and sponges. Streptomyces is a genus of Gram-positive bacteria that has a filamentous form like fungi. This genus is best known as one of polyketides producers. Some examples of polyketides produced by Streptomyces are rapamycin, oleandomycin, actinorhodin, daunorubicin and caprazamycin. Biosynthesis of polyketides involves a group of enzyme activities called polyketide synthases (PKSs). There are three types of PKSs (type I, type II, and type III) in Streptomyces that responsible for producing polyketides. This paper focuses on biosynthesis of polyketides in Streptomyces with three structurally different types of PKSs.
ARTICLE | doi:10.20944/preprints202108.0484.v1
Subject: Biology, Other Keywords: cyanobacteria; metabolomics; high-resolution mass spectrometry; secondary metabolite induction; culture conditions
Online: 25 August 2021 (10:48:20 CEST)
Cyanobacteria are microorganisms able to adapt to a wide variety of environmental conditions and abiotic stresses. They produce a very large number of metabolites that can participate in the adaptation of cyanobacteria to a large range of resources such as light, temperature, or nutrient. The metabolites variation is one way to understand the physiological status and adaptation of cells. In this study, we aim to understand how the diversity and the dynamics of the whole metabolome is dependent of the growth phases and under control of abiotic factors (e.g. light intensity and temperature). The cyanobacteria Aliinostoc sp. PMC 882.14 was selected for its large number of biosynthetic gene clusters. Metabolomes were analyzed by using mass spectrometry (qTOF-MS/MS) combined with untargeted analysis to investigate the metabolite dynamics. Significant variations were characterized between exponential and stationary phases, whatever the culture conditions (“control”, “higher light”, or “higher temperature”). ”Higher light” and “higher temperature” favored the synthesis of metabolites belonging to the same molecular families. Among highly regulated metabolites, we observe the presence of mycosporine-like amino acids (MAAs), and various variants of somamides, microginins, and microviridins. Through Aliinostoc sp. PMC 882.14, this study shows the importance of knowing the physiological state of cyanobacteria for comparative global metabolomics and questions the regulation processes involve into metabolite families production. Our results also open up new perspectives in the context of the production of targeted bioactive metabolites.
ARTICLE | doi:10.20944/preprints202205.0069.v1
Subject: Medicine & Pharmacology, General Medical Research Keywords: Volatile organic compound; VOC; headspace; breath; breath biomarker; volatile metabolite; breath diagnosis
Online: 6 May 2022 (09:27:04 CEST)
Volatile compounds, abundant in breath, can be used to accurately diagnose and monitor a range of medical conditions. This offers a non-invasive, low-cost approach with screening applications; however, uptake of this diagnostic approach has been limited by conflicting published outcomes. Most published reports rely on large scale screening of the public, at single time points and without reference to ambient air. Here, we present a novel approach to volatile sampling from cellular headspace and mouse breath that incorporates multi-time point analysis and ambient air subtraction revealing compound flux as an effective proxy of active metabolism. This approach to investigating breath volatiles offers a new avenue for disease biomarker discovery and diagnosis. Using gas chromatography mass spectrometry (GC/MS), we focus on low molecular weight, metabolic substrate/by-product compounds and demonstrate that this non-invasive technique is sensitive (reproducible at ~1 µg cellular protein, or ~500,000 cells) and capable of precisely determining cell type, status and treatment. Isolated cellular models represent components of larger mammalian systems and we show that stress- and pathology-indicative compounds are detectable in mice, supporting further investigation using this methodology as a tool to identify volatile targets in human patients.
ARTICLE | doi:10.20944/preprints202103.0596.v1
Subject: Biology, Anatomy & Morphology Keywords: postharvest treatment; jasmonate; metabolite profiling; lipid metabolism; Solanum lycopersicum; ethylene inhibition; fruit quality
Online: 24 March 2021 (16:12:21 CET)
Application of exogenous jasmonate can stimulate the production of ethylene, carotenoids and aroma compounds, resulting in the acceleration of fruit ripening. These alterations improve fruit quality and make fruit desirable for human consumption, but overripening of a fruit results in large losses of fruit crops. In order to overcome this problem, 1-methylcyclopropene was ap-plied to the fruits due to its capacity to block the receptors of ethylene, resulting in the sup-pressed of fruit ripening. In this study, treatments only with 1-methylcyclopropene, and with both 1-methylcyclopropene and methyl jasmonate was conducted to observe if an exogenous methyl jasmonate can improve the levels of metabolites in their fruits with ethylene receptors blocked. Fruits were analyzed at 4, 10 and 21 day after harvest (DAH) and compared with the no treated fruits. The postharvest treatments affected primary metabolites (sugars, organic acids, amino acids and fatty acids) and secondary metabolites (carotenoids, tocopherols and phytoster-ols). However, the lipid metabolism of the tomato was the most impacted by the exogenous jasmonate. Fatty acids, carotenoids, tocopherols and phytosterols showed a delay in their pro-duction at 4 and 10 DAH. In contrast, at 21 DAH these non-polar metabolites exhibited an im-portant improvement in their accumulation.
Subject: Medicine & Pharmacology, Nutrition Keywords: metabolomics; metabolite profiling; prudent diet; western diet; food provisions; diet records; nutritional epidemiology; mass spectrometry
Online: 22 September 2019 (15:20:34 CEST)
A large body of evidence has linked unhealthy eating patterns with an alarming increase in obesity and chronic disease worldwide. However, existing methods of assessing dietary intake in nutritional epidemiology rely on food frequency questionnaires or dietary records that are prone to bias and selective reporting. Herein, metabolic phenotyping was performed on 42 healthy participants from the Diet and Gene Intervention (DIGEST) pilot study, a parallel two-arm randomized clinical trial that provided complete diets to all participants. Matching urine and plasma specimens were collected at baseline and following 2 weeks of provision of either a Prudent or Western diet with a weight-maintaining menu plan designed by a dietician. Targeted and nontargeted metabolite profiling was conducted using three complementary analytical platforms, where 80 plasma metabolites and 84 creatinine-normalized urinary metabolites were reliably measured (CV < 30%) in the majority of participants (> 75%) after implementing a rigorous data workflow for metabolite authentication with stringent quality control. We classified a panel of metabolites with distinctive trajectories following 2 weeks of food provisions when using complementary univariate and multivariate statistical models. Unknown metabolites associated with contrasting dietary patterns were identified with high resolution MS/MS and/or co-elution after spiking with authentic standards. Overall, 3-methylhistidine and proline betaine concentrations increased consistently after participants were assigned a Prudent diet (q< 0.05) in both plasma and urine samples with a corresponding decrease in the Western diet group. Similarly, creatinine-normalized urinary imidazole propionate, hydroxypipecolic acid, dihydroxybenzoic acid, and enterolactone glucuronide, as well as plasma ketoleucine and ketovaline increased with a Prudent diet (p< 0.05) after adjustments for age, sex and BMI. In contrast, plasma myristic acid, linoelaidic acid, linoleic acid, a-linoleic acid, pentadecanoic acid, alanine, proline, carnitine and deoxycarnitine, as well as urinary acesulfame K increased among participants following a Western diet. Most metabolites were also correlated (r > ±0.30, p< 0.05) to changes in average intake of specific nutrients from self-reported diet records reflecting good adherence to assigned food provisions. Our study revealed robust biomarkers sensitive to short-term changes in habitual diet for accurate monitoring of healthy eating patterns in free-living populations, which is required for validating evidence-based public health policies for chronic disease prevention.
ARTICLE | doi:10.20944/preprints202104.0390.v1
Subject: Life Sciences, Biochemistry Keywords: redox metabolites; mass-spectrometry method; HILIC chromatography; NADH; NADPH; Glutathione; redox metabolite detection in mammalian cells
Online: 14 April 2021 (16:09:16 CEST)
Cellular redox state is highly dynamic and delicately balanced between constant production of reactive oxygen species (ROS), and neutralization by endogenous antioxidants, such as glutathione. Physiologic ROS levels can function as signal transduction messengers, while high levels of ROS can react with and damage various molecules eliciting cellular toxicity. The redox state is reflective of the cell’s metabolic status and can inform on regulated cell-state transitions or various pathologies including aging and cancer. Therefore, methods that enable reliable, quantitative readout of the cellular redox state are imperative for scientists from multiple fields. Liquid-chromatography mass-spectrometry (LC-MS) based methods to detect small molecules that reflect the redox balance in the cell such as glutathione, NADH and NADPH, have been developed and applied successfully, but because redox metabolites are very labile, these methods are not easily standardized or consolidated. Here we report a robust LC-MS method for the simultaneous detection of several redox-reactive metabolites that is compatible with parallel global metabolic profiling in mammalian cells. We performed a comprehensive comparison between three commercial hydrophilic interaction chromatography (HILIC) columns, and we describe the application of our method in mammalian cells and tissues. The presented method is easily applicable and will enable the study of ROS function and oxidative stress in mammalian cells by researchers from various fields.
ARTICLE | doi:10.20944/preprints202012.0635.v1
Subject: Medicine & Pharmacology, Allergology Keywords: Free fatty acid receptor 2; microbiota; metabolite; sensor; G-coupled protein receptor; signaling; Alzheimer’s disease; senescence; C. elegans
Online: 24 December 2020 (14:56:00 CET)
Gut microbiota and its metabolites like short chain fatty acids (SCFAs) are linked with pathology of Alzheimer’s disease (AD)- a debilitating public health problem in older adults. However, strategies to beneficially modulate gut microbiota and its sensing signaling pathways remain largely unknown. Here, we screened, validated and established the agonists of free fatty acid receptor 2 (FFAR2) signaling, which senses beneficial signals from SCFAs produced by microbiota in the gut. We demonstrated that inhibition of FFAR2 signaling increases amyloid-beta (Aβ) stimulated neuronal toxicity. Thus, we screened FFAR2 agonists, using in-silico library of more than 144,000 natural compounds, and 15 compounds were selected based on binding with FFAR2 agonist sites. Further, cell culture toxicity and FFAR2 stimulatory experiments demonstrated that Fenchol (a natural compound commonly present in basil) was potent FFAR2 agonist in neuronal cells. Interestingly, we also demonstrated that Fenchol protects Aβ-stimulated neurodegeneration in FFAR2 dependent manner. In addition, Fenchol reduced AD like phenotypes such as Aβ-accumulation and, learning and memory behaviors in Caenorhabditis (C.) elegans. Fenchol increased Aβ-clearance by increasing proteasome/lysosome activity and reduced senescence in neuronal cells. These results demonstrated that the inhibition of FFAR2 signaling promotes Aβ-induced neurodegeneration, while activating it by Fenchol as a natural agonist reverse it by promoting Aβ-clearance and reducing cellular senescence; thus stimulation of FFAR2 signaling can be a therapeutic approach to prevent/ treat AD.