Acetate derived from the intestinal tract has a critical role in maintaining skeletal muscle mass and strength in mice.

Acetate is a short-chain fatty acid (SCFA) that is produced by microbiota in the intestinal tract. It is an important nutrient for the intestinal epithelium, but also has a high plasma concentration and is used in the various tissues. Acetate is involved in endurance exercise, but its role in resistance exercise remains unclear. To investigate this, mice were administered either multiple antibiotics with and without oral acetate supplementation or fed a low-fiber diet. Antibiotic treatment for 2 weeks significantly reduced grip strength and the cross-sectional area (CSA) of muscle fiber compared with the control group. Intestinal concentrations of SCFAs were reduced in the antibiotic-treated group. Oral administration of acetate with antibiotics prevented antibiotic-induced weakness of skeletal muscle and reduced CSA of muscle fiber. Similarly, a low-fiber diet for 1 year significantly reduced the CSA of muscle fiber and fecal and plasma acetate concentrations. To investigate the role of acetate as an energy source, acetyl-CoA synthase 2 knockout mice were used. These mice had a shorter lifespan, reduced skeletal muscle mass and smaller CSA of muscle fiber than their wild type littermates. In conclusion, acetate derived from the intestinal microbiome can contribute to maintaining skeletal muscle performance.

Comparative analysis of POD genes and their expression under multiple hormones in Pyrus bretschenedri.

BACKGROUND: Class III peroxidase (POD) enzymes play vital roles in plant development, hormone signaling, and stress responses. Despite extensive research on POD families in various plant species, the knowledge regarding the POD family in Chinese pear (Pyrus bretschenedri) is notably limited. RESULTS: We systematically characterized 113 POD family genes, designated as PbPOD1 to PbPOD113 based on their chromosomal locations. Phylogenetic analysis categorized these genes into seven distinct subfamilies (I to VII). The segmental duplication events were identified as a prevalent mechanism driving the expansion of the POD gene family. Microsynteny analysis, involving comparisons with Pyrus bretschenedri, Fragaria vesca, Prunus avium, Prunus mume and Prunus persica, highlighted the conservation of duplicated POD regions and their persistence through purifying selection during the evolutionary process. The expression patterns of PbPOD genes were performed across various plant organs and diverse fruit development stages using transcriptomic data. Furthermore, we identified stress-related cis-acting elements within the promoters of PbPOD genes, underscoring their involvement in hormonal and environmental stress responses. Notably, qRT-PCR analyses revealed distinctive expression patterns of PbPOD genes in response to melatonin (MEL), salicylic acid (SA), abscisic acid (ABA), and methyl jasmonate (MeJA), reflecting their responsiveness to abiotic stress and their role in fruit growth and development. CONCLUSIONS: In this study, we investigated the potential functions and evolutionary dynamics of PbPOD genes in Pyrus bretschenedri, positioning them as promising candidates for further research and valuable indicators for enhancing fruit quality through molecular breeding strategies.

Biofiltration of toluene in the presence of ethyl acetate or n-hexane: Performance and microbial community.

This study describes the operation of two independent parallel laboratory-scale biotrickling filters (BTFs) to degrade different types of binary volatile organic compound (VOC) mixtures. Comparison experiments were conducted to evaluate the effects of two typical VOCs, i.e., ethyl acetate (a hydrophilic VOC) and n-hexane (a hydrophobic VOC) on the removal performance of toluene (a moderately hydrophobic VOC) in BTFs ''A" and ''B", respectively. Experiments were carried out by stabilizing the toluene concentration at 1.64 g m-3 and varying the concentrations of gas-phase ethyl acetate (0.85-2.8 g m-3) and n-hexane (0.85-2.8 g m-3) at an empty bed residence time (EBRT) of 30 s. In the presence of ethyl acetate (850 ± 55 mg m-3), toluene exhibited the highest removal efficiency (95.4 ± 2.2%) in BTF "A". However, the removal rate of toluene varied from 48.1 ± 6.9% to 70.1 ± 6.8% when 850 ± 123 mg m-3 to 2800 ± 136 mg m-3 of n-hexane was introduced into BTF "B". The high-throughput sequencing data revealed that the genera Pseudomonas and Comamonadaceae_unclassified are the core microorganisms responsible for the degradation of toluene. The intensity of the inhibitory or synergistic effects on toluene removal was influenced by the type and concentration of the introduced VOC, as well as the number and activity of the genera Pseudomonas and Comamonadaceae_unclassified. It provides insights into the interaction between binary VOCs during biofiltration from a microscopic perspective.

Adlercreutzia faecimuris sp. nov., producing propionate and acetate isolated from mouse feces.

A novel strictly anaerobic bacterium, strain JBNU-10 T, was isolated from BALB/c mouse feces. Cells of the strain JBNU-10 T were Gram-stain positive, non-motile and rod-shaped. Optimum growth occurred at 37℃, with 1% (w/v) NaCl and at pH 7. Phylogenetic analysis based on 16S rRNA gene sequence showed that strain JBNU-10 T belonged to the genus Adlercreutzia and were closely related to Adlercreutzia muris WCA-131-CoC-2 T (95.90%). The genome sequencing of strain JBNU-10 T revealed a genome size of 2,790,983 bp, a DNA G + C content of 69.4 mol%. It contains a total of 2,266 CDSs, 5 rRNA genes and 49 tRNA genes. According to the data obtained strain JBNU-10 T shared ANI value below 77.6- 67.7%, dDDH value below 23.8% with the closely type species. Strain JBNU-10 T possessed iso-C16:0 DMA, C18:1 CIS 9 FAME, and C18:0 DMA as the major fatty acids and had DMMK-6. The major end products of fermentation is propionate and acetate. Based on phylogenetic, physiological and chemotaxonomic characteristics, strain JBNU-10 T represent a novel species of the genus Adlercreutzia. The type strain is JBNU-10 T (= KCTC 25028 T = CCUG 75610 T).

Integration of biocompatible hydrogen evolution catalyst developed from metal-mix solutions with microbial electrosynthesis.

Microbial conversion of CO2 to multi-carbon compounds such as acetate and butyrate is a promising valorisation technique. For those reactions, the electrochemical supply of hydrogen to the biocatalyst is a viable approach. Earlier we have shown that trace metals from microbial growth media spontaneously form in situ electro-catalysts for hydrogen evolution. Here, we show biocompatibility with the successful integration of such metal mix-based HER catalyst for immediate start-up of microbial acetogenesis (CO2 to acetate). Also, n-butyrate formation started fast (after twenty days). Hydrogen was always produced in excess, although productivity decreased over the 36 to 50 days, possibly due to metal leaching from the cathode. The HER catalyst boosted microbial productivity in a two-step microbial community bioprocess: acetogenesis by a BRH-c20a strain and acetate elongation to n-butyrate by Clostridium sensu stricto 12 (related) species. These findings provide new routes to integrate electro-catalysts and micro-organisms showing respectively bio and electrochemical compatibility.

Acetate Alleviates Gut Microbiota Depletion-Induced Retardation of Skeletal Muscle Growth and Development in Young Mice.

The normal growth and development of skeletal muscle is essential for the health of the body. The regulation of skeletal muscle by intestinal microorganisms and their metabolites has been continuously demonstrated. Acetate is the predominant short-chain fatty acids synthesized by gut microbiota through the fermentation of dietary fiber; however, the underlying molecular mechanisms governing the interaction between acetate and skeletal muscle during the rapid growth stage remains to be further elucidated. Herein, specific pathogen-free (SPF) mice, germ-free (GF) mice, and germ-free mice supplemented with sodium acetate (GS) were used to evaluate the effects of acetate on the skeletal muscle growth and development of young mice with gut microbiota deficiency. We found that the concentration of serum acetate, body mass gain, succinate dehydrogenase activity, and expression of the myogenesis maker gene of skeletal muscle in the GS group were higher than those in the GF group, following sodium acetate supplementation. Furthermore, the transcriptome analysis revealed that acetate activated the biological processes that regulate skeletal muscle growth and development in the GF group, which are otherwise inhibited due to a gut microbiota deficiency. The in vitro experiment showed that acetate up-regulated Gm16062 to promote skeletal muscle cell differentiation. Overall, our findings proved that acetate promotes skeletal muscle growth and development in young mice via increasing Gm16062 expression.

Transcriptomic evidence for an energetically advantageous relationship between Syntrophomonas wolfei and Methanothrix soehngenii.

Syntrophic interactions are key in anaerobic food chains, facilitating the conversion of complex organic matter into methane. A typical example involves acetogenic bacteria converting fatty acids (e.g., butyrate and propionate), a process thermodynamically reliant on H2 consumption by microorganisms such as methanogens. While most studies focus on H2-interspecies transfer between these groups, knowledge on acetate cross-feeding in anaerobic systems is lacking. This study investigated butyrate oxidation by co-cultures of Syntrophomonas wolfei and Methanospirillum hungatei, both with and without the addition of the acetate scavenger Methanothrix soehngenii. Growth and gene expression patterns of S. wolfei and M. hungatei were followed in the two conditions. Although butyrate consumption rates remained constant, genes in the butyrate degradation pathway of S. wolfei were less expressed in the presence of M. soehngenii, including genes involved in reverse electron transport. Higher expression of a type IV-pili operon in S. wolfei hints to the potential for direct interspecies electron transfer between S. wolfei and M. soehngenii and an energetically advantageous relationship between the two microorganisms. Overall, the presence of the acetate scavenger M. soehngenii positively influenced the energy metabolism of S. wolfei and highlighted the relevance of including acetate scavengers when investigating syntrophic fatty acid degradation.

Acetate reprogrammes tumour metabolism and promotes PD-L1 expression and immune evasion by upregulating c-Myc.

Acetate, a precursor of acetyl-CoA, is instrumental in energy production, lipid synthesis and protein acetylation. However, whether acetate reprogrammes tumour metabolism and plays a role in tumour immune evasion remains unclear. Here, we show that acetate is the most abundant short-chain fatty acid in human non-small cell lung cancer tissues, with increased tumour-enriched acetate uptake. Acetate-derived acetyl-CoA induces c-Myc acetylation, which is mediated by the moonlighting function of the metabolic enzyme dihydrolipoamide S-acetyltransferase. Acetylated c-Myc increases its stability and subsequent transcription of the genes encoding programmed death-ligand 1, glycolytic enzymes, monocarboxylate transporter 1 and cell cycle accelerators. Dietary acetate supplementation promotes tumour growth and inhibits CD8+ T cell infiltration, whereas disruption of acetate uptake inhibits immune evasion, which increases the efficacy of anti-PD-1-based therapy. These findings highlight a critical role of acetate promoting tumour growth beyond its metabolic role as a carbon source by reprogramming tumour metabolism and immune evasion, and underscore the potential of controlling acetate metabolism to curb tumour growth and improve the response to immune checkpoint blockade therapy.

Combined analysis of Polygonum cuspidatum transcriptome and metabolome revealed that PcMYB62, a transcription factor, responds to methyl jasmonate and inhibits resveratrol biosynthesis.

A comparative transcriptomic and metabolomic analysis of Polygonum cuspidatum leaves treated with MeJA was carried out to investigate the regulatory mechanisms of its active compounds. A total of 692 metabolites and 77,198 unigenes were obtained, including 200 differentially accumulated metabolites and 6819 differentially expressed genes. We screened potential regulatory transcription factors involved in resveratrol and flavonoids biosynthesis, and successfully identified an MYB transcription factor, PcMYB62, which could significantly decrease the resveratrol content in P. cuspidatum leaves when over-expressed. PcMYB62 could directly bind to the MBS motifs in the promoter region of stilbene synthase (PcSTS) gene and repress its expression. Besides, PcMYB62 could also repress PcSTS expression and resveratrol biosynthesis in transgenic Arabidopsis thaliana. Our results provide abundant candidate genes for further investigation, and the new finding of the inhibitory role of PcMYB62 on the resveratrol biosynthesis could also potentially be used in metabolic engineering of resveratrol in P. cuspidatum.

13C metabolite tracing reveals glutamine and acetate as critical in vivo fuels for CD8 T cells.

Infusion of 13C-labeled metabolites provides a gold standard for understanding the metabolic processes used by T cells during immune responses in vivo. Through infusion of 13C-labeled metabolites (glucose, glutamine, and acetate) in Listeria monocytogenes-infected mice, we demonstrate that CD8 T effector (Teff) cells use metabolites for specific pathways during specific phases of activation. Highly proliferative early Teff cells in vivo shunt glucose primarily toward nucleotide synthesis and leverage glutamine anaplerosis in the tricarboxylic acid (TCA) cycle to support adenosine triphosphate and de novo pyrimidine synthesis. In addition, early Teff cells rely on glutamic-oxaloacetic transaminase 1 (Got1)-which regulates de novo aspartate synthesis-for effector cell expansion in vivo. CD8 Teff cells change fuel preference over the course of infection, switching from glutamine- to acetate-dependent TCA cycle metabolism late in infection. This study provides insights into the dynamics of Teff metabolism, illuminating distinct pathways of fuel consumption associated with CD8 Teff cell function in vivo.

Functional characterisation of Artemisia annua jasmonic acid carboxyl methyltransferase: a key enzyme enhancing artemisinin biosynthesis.

MAIN CONCLUSION: Overexpression of Artemisia annua jasmonic acid carboxyl methyltransferase (AaJMT) leads to enhanced artemisinin content in Artemisia annua. Artemisinin-based combination therapies remain the sole deterrent against deadly disease malaria and Artemisia annua remains the only natural producer of artemisinin. In this study, the 1101 bp gene S-adenosyl-L-methionine (SAM): Artemisia annua jasmonic acid carboxyl methyltransferase (AaJMT), was characterised from A. annua, which converts jasmonic acid (JA) to methyl jasmonate (MeJA). From phylogenetic analysis, we confirmed that AaJMT shares a common ancestor with Arabidopsis thaliana, Eutrema japonica and has a close homology with JMT of Camellia sinensis. Further, the Clustal Omega depicted that the conserved motif I, motif III and motif SSSS (serine) required to bind SAM and JA, respectively, are present in AaJMT. The relative expression of AaJMT was induced by wounding, MeJA and salicylic acid (SA) treatments. Additionally, we found that the recombinant AaJMT protein catalyses the synthesis of MeJA from JA with a Km value of 37.16 µM. Moreover, site-directed mutagenesis of serine-151 in motif SSSS to tyrosine, asparagine-10 to threonine and glutamine-25 to histidine abolished the enzyme activity of AaJMT, thus indicating their determining role in JA substrate binding. The GC-MS analysis validated that mutant proteins of AaJMT were unable to convert JA into MeJA. Finally, the artemisinin biosynthetic and trichome developmental genes were upregulated in AaJMT overexpression transgenic lines, which in turn increased the artemisinin content.

Disordered GPR43/NLRP3 expression in peripheral leukocytes of patients with atrial fibrillation is associated with intestinal short chain fatty acids levels.

BACKGROUND: Atrial fibrillation (AF) is associated with circulating inflammation. Short-chain fatty acids (SCFAs) derived from gut microbiota (GM) regulate leukocyte function and inhibit the release of inflammatory cytokines, which are partly mediated by the G-protein-coupled receptor 43 (GPR43) signaling. This study aimed to investigate the expression of GPR43/NOD-like receptors family pyrin domain containing 3 (NLRP3) in leukocytes and the interaction with intestinal SCFAs levels in AF patients. METHODS: Expressions of GPR43 and NLRP3 mRNA in peripheral blood leukocytes from 23 AF patients and 25 non-AF controls were detected by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Expressions of leukocyte GPR43 and NLRP3 protein were evaluated by western blot analysis. The levels of plasma IL-1ß were measured by enzyme-linked immunosorbent assay (ELISA). The fecal SCFAs levels based on GC/MS metabolome of corresponding 21 controls and 14 AF patients were acquired from our published dataset. To evaluate the expression of NLRP3 and GPR43 and the release of IL-1ß, human THP-1 cells were stimulated with or without SCFAs (acetate, propionate, and butyrate), lipopolysaccharide (LPS), and nigericin in vitro, respectively. RESULTS: Compared to the controls, the mRNA expression in peripheral leukocytes was significantly reduced in AF patients (P = 0.011) coupled with the increase in downstream leukocyte NLRP3 mRNA expression (P = 0.007) and plasma IL-1ß levels (P < 0.001), consistent with changes in GPR43 and NLRP3 protein expression. Furthermore, leukocyte GPR43 mRNA levels were positively correlated with fecal GM-derived acetic acid (P = 0.046) and negatively correlated with NLRP3 mRNA expression (P = 0.024). In contrast to the negative correlation between left atrial diameter (LAD) and GPR43 (P = 0.008), LAD was positively correlated with the leukocyte NLRP3 mRNA levels (P = 0.024). Subsequent mediation analysis showed that 68.88% of the total effect of intestinal acetic acid on AF might be mediated by leukocyte GPR43/NLRP3. The constructed GPR43-NLRP3 score might have a predictive potential for AF detection (AUC = 0.81, P < 0.001). Moreover, SCFAs treatment increased GPR43 expression and remarkably reduced LPS/nigericin-induced NLRP3 expression and IL-1ß release in human THP-1 cells in vitro. CONCLUSIONS: Disrupted interactions between GPR43 and NLRP3 expression in peripheral blood leukocytes, associated with reduced intestinal GM-derived SCFAs, especially acetic acid, may be involved in AF development and left atrial enlargement by enhancing circulating inflammation.

Exploring rumen fermentation and microbial populations in Dhofari goats fed a chitosan-added diet.

The use of chitosan (CHI) in ruminant diets is a promising natural modifier for rumen fermentation, capable of modulating both the rumen pattern and microbial activities. The objective of this study was to explore the rumen fermentation and microbial populations in Dhofari goats fed a diet supplemented with CHI. A total of 24 Dhofari lactating goats (body weight, 27.32 ± 1.80 kg) were assigned randomly into three experimental groups (n = 8 ewes/group). Goats were fed a basal diet with either 0 (control), 180 (low), or 360 (high) mg CHI/kg of dietary dry matter (DM) for 45 days. Feeding high CHI linearly increased (p < 0.05) the propionate level and reduced the acetate, butyrate, and total protozoa count (p < 0.05). Ruminal ammonia nitrogen (NH3-N) concentrations and the acetate:propionate ratio decreased linearly when goats were fed CHI (p < 0.05). The abundances of both Spirochetes and Fibrobacteres phyla were reduced (p < 0.05) with both CHI doses relative to the control. Both low and high CHI reduced (p < 0.05) the relative abundances of Butyrivibrio hungatei, Fibrobacter succinogenes, Ruminococcus albus, Ruminococcus flavefaciens, Selenomonas ruminantium and Neocallimastix californiae populations. Adding CHI significantly decreased (p < 0.05) the abundances of Ascomycota, Basidiomycota, and Bacillariophyta phyla compared to the control. Adding CHI to the diet reduces the abundance of fibrolytic-degrading bacteria, however, it increases the amylolytic-degrading bacteria. Application of 360 mg of CHI/kg DM modified the relative populations of ruminal microbes, which could enhance the rumen fermentation patterns in Dhofari goats.

Insights into intraspecific diversity of central carbon metabolites in Saccharomyces cerevisiae during wine fermentation.

Saccharomyces cerevisiae is a major actor in winemaking that converts sugars from the grape must into ethanol and CO2 with outstanding efficiency. Primary metabolites produced during fermentation have a great importance in wine. While ethanol content contributes to the overall profile, other metabolites like glycerol, succinate, acetate or lactate also have significant impacts, even when present in lower concentrations. S. cerevisiae is known for its great genetic diversity that is related to its natural or technological environment. However, the variation range of metabolic diversity which can be exploited to enhance wine quality depends on the pathway considered. Our experiment assessed the diversity of primary metabolites production in a set of 51 S. cerevisiae strains from various genetic backgrounds. Results pointed out great yield differences depending on the metabolite considered, with ethanol having the lowest variation. A negative correlation between ethanol and glycerol was observed, confirming glycerol synthesis as a suitable lever to reduce ethanol yield. Genetic groups were linked to specific yields, such as the wine group and high α-ketoglutarate and low acetate yields. This research highlights the potential of using natural yeast diversity in winemaking. It also provides a detailed data set on production of well known (ethanol, glycerol, acetate) or little-known (lactate) primary metabolites.

The gut commensal Blautia maintains colonic mucus function under low-fiber consumption through secretion of short-chain fatty acids.

Beneficial gut bacteria are indispensable for developing colonic mucus and fully establishing its protective function against intestinal microorganisms. Low-fiber diet consumption alters the gut bacterial configuration and disturbs this microbe-mucus interaction, but the specific bacteria and microbial metabolites responsible for maintaining mucus function remain poorly understood. By using human-to-mouse microbiota transplantation and ex vivo analysis of colonic mucus function, we here show as a proof-of-concept that individuals who increase their daily dietary fiber intake can improve the capacity of their gut microbiota to prevent diet-mediated mucus defects. Mucus growth, a critical feature of intact colonic mucus, correlated with the abundance of the gut commensal Blautia, and supplementation of Blautia coccoides to mice confirmed its mucus-stimulating capacity. Mechanistically, B. coccoides stimulated mucus growth through the production of the short-chain fatty acids propionate and acetate via activation of the short-chain fatty acid receptor Ffar2, which could serve as a new target to restore mucus growth during mucus-associated lifestyle diseases.

Multi-modular metabolic engineering and efflux engineering for enhanced lycopene production in recombinant Saccharomyces cerevisiae.

Lycopene has been widely used in the food industry and medical field due to its antioxidant, anti-cancer, and anti-inflammatory properties. However, achieving efficient manufacture of lycopene using chassis cells on an industrial scale remains a major challenge. Herein, we attempted to integrate multiple metabolic engineering strategies to establish an efficient and balanced lycopene biosynthetic system in Saccharomyces cerevisiae. First, the lycopene synthesis pathway was modularized to sequentially enhance the metabolic flux of the mevalonate pathway, the acetyl-CoA supply module, and lycopene exogenous enzymatic module. The modular operation enabled the efficient conversion of acetyl-CoA to downstream pathway of lycopene synthesis, resulting in a 3.1-fold increase of lycopene yield. Second, we introduced acetate as an exogenous carbon source and utilized an acetate-repressible promoter to replace the natural ERG9 promoter. This approach not only enhanced the supply of acetyl-CoA but also concurrently diminished the flux toward the competitive ergosterol pathway. As a result, a further 42.3% increase in lycopene production was observed. Third, we optimized NADPH supply and mitigated cytotoxicity by overexpressing ABC transporters to promote lycopene efflux. The obtained strain YLY-PDR11 showed a 12.7-fold increase in extracellular lycopene level compared to the control strain. Finally, the total lycopene yield reached 343.7 mg/L, which was 4.3 times higher than that of the initial strain YLY-04. Our results demonstrate that combining multi-modular metabolic engineering with efflux engineering is an effective approach to improve the production of lycopene. This strategy can also be applied to the overproduction of other desirable isoprenoid compounds with similar synthesis and storage patterns in S. cerevisiae. ONE-SENTENCE SUMMARY: In this research, lycopene production in yeast was markedly enhanced by integrating a multi-modular approach, acetate signaling-based down-regulation of competitive pathways, and an efflux optimization strategy.

Stepwise Flux Optimization for Enhanced GABA Production from Acetate in Escherichia coli.

Strategic allocation of metabolic flux is essential for achieving a higher production performance in genetically engineered organisms. Flux optimization between cell growth and chemical production has led to the establishment of cost-effective chemical production methods in microbial cell factories. This effect is amplified when utilizing a low-cost carbon source. γ-Aminobutyric acid (GABA), crucial in pharmaceuticals and biodegradable polymers, can be efficiently produced from acetate, a cost-effective substrate. However, a balanced distribution of acetate-derived flux is essential for optimizing the production without hindering growth. In this study, we demonstrated GABA production from acetate using Escherichia coli by focusing on optimizing the metabolic flux at isocitrate and α-ketoglutarate nodes. Through a series of flux optimizations, the final strain produced 2.54 g/L GABA from 5.91 g/L acetate in 24 h (0.43 g/g yield). These findings suggest that delicate flux balancing with the application of a cheap substrate can contribute to cost-effective production of GABA.

Insights into the relative contribution of four precursors to 3-sulfanylhexan-1-ol and 3-sulfanylhexylacetate biogenesis during fermentation.

The desirable wine aroma compounds 3-sulfanylhexan-1-ol (3SH) and 3-sulfanylhexyl acetate (3SHA) are released during fermentation from non-volatile precursors present in the grapes. This work explores the relative contribution of four precursors (E-2-hexenal, 3-S-glutathionylhexan-1-ol, 3-S-glutathionylhexanal, and 3-S-cysteinylhexan-1-ol) to 3SH and 3SHA. Through the use of isotopically labelled analogues of these precursors in defined fermentation media, new insights into the role of each precursor have been identified. E-2-Hexenal was shown to contribute negligible amounts of thiols, while 3-S-glutathionylhexan-1-ol was the main precursor of both 3SH and 3SHA. The glutathionylated precursors were both converted to 3SHA more efficiently than 3-S-cysteinylhexan-1-ol. Interestingly, 3-S-glutathionylhexanal generated 3SHA without detectable concentrations of 3SH, suggesting possible differences in the way this precursor is metabolised compared to 3-S-glutathionylhexan-1-ol and 3-S-cysteinylhexan-1-ol. We also provide the first evidence for chemical conversion of 3-S-glutathionylhexan-1-ol to 3-S-(γ-glutamylcysteinyl)-hexan-1-ol in an oenological system.

Chronotropic and vasoactive properties of the gut bacterial short-chain fatty acids in larval zebrafish.

Short-chain fatty acids (SCFAs) produced by the gut bacteria have been associated with cardiovascular dysfunction in humans and rodents. However, studies exploring effects of SCFAs on cardiovascular parameters in the zebrafish, an increasingly popular model in cardiovascular research, remain limited. Here, we performed fecal bacterial 16S sequencing and gas chromatography/mass spectrometry (GC-MS) to determine the composition and abundance of gut microbiota and SCFAs in adult zebrafish. Following this, the acute effects of major SCFAs on heart rate and vascular tone were measured in anesthetized zebrafish larvae using fecal concentrations of butyrate, acetate, and propionate. Finally, we investigated if coincubation with butyrate may lessen the effects of angiotensin II (ANG II) and phenylephrine (PE) on vascular tone in anesthetized zebrafish larvae. We found that the abundance in Proteobacteria, Firmicutes, and Fusobacteria phyla in the adult zebrafish resembled those reported in rodents and humans. SCFA levels with highest concentration of acetate (27.43 µM), followed by butyrate (2.19 µM) and propionate (1.65 µM) were observed in the fecal samples of adult zebrafish. Immersion in butyrate and acetate produced a ∼20% decrease in heart rate (HR), respectively, with no observed effects of propionate. Butyrate alone also produced an ∼25% decrease in the cross-sectional width of the dorsal aorta (DA) at 60 min (*P < 0.05), suggesting compensatory vasoconstriction, with no effects of either acetate or propionate. In addition, butyrate significantly alleviated the decrease in DA cross-sectional width produced by both ANG II and PE. We demonstrate the potential for zebrafish in investigation of host-microbiota interactions in cardiovascular health.NEW & NOTEWORTHY We highlight the presence of a core gut microbiota and demonstrate in vivo short-chain fatty acid production in adult zebrafish. In addition, we show cardio-beneficial vasoactive and chronotropic properties of butyrate, and chronotropic properties of acetate in anesthetized zebrafish larvae.

Functional Characterization of PmDXR, a Critical Rate-Limiting Enzyme, for Turpentine Biosynthesis in Masson Pine (Pinus massoniana Lamb.).

As one of the largest and most diverse classes of specialized metabolites in plants, terpenoids (oprenoid compounds, a type of bio-based material) are widely used in the fields of medicine and light chemical products. They are the most important secondary metabolites in coniferous species and play an important role in the defense system of conifers. Terpene synthesis can be promoted by regulating the expressions of terpene synthase genes, and the terpene biosynthesis pathway has basically been clarified in Pinus massoniana, in which there are multiple rate-limiting enzymes and the rate-limiting steps are difficult to determine, so the terpene synthase gene regulation mechanism has become a hot spot in research. Herein, we amplified a PmDXR gene (GenBank accession no. MK969119.1) of the MEP pathway (methyl-erythritol 4-phosphate) from Pinus massoniana. The DXR enzyme activity and chlorophyll a, chlorophyll b and carotenoid contents of overexpressed Arabidopsis showed positive regulation. The PmDXR gene promoter was a tissue-specific promoter and can respond to ABA, MeJA and GA stresses to drive the expression of the GUS reporter gene in N. benthamiana. The DXR enzyme was identified as a key rate-limiting enzyme in the MEP pathway and an effective target for terpene synthesis regulation in coniferous species, which can further lay the theoretical foundation for the molecularly assisted selection of high-yielding lipid germplasm of P. massoniana, as well as provide help in the pathogenesis of pine wood nematode disease.