The efficacy and safety of nutrient supplements in the treatment of mental disorders: a meta‐review of meta‐analyses of randomized controlled trials

The role of nutrition in mental health is becoming increasingly acknowledged. Along with dietary intake, nutrition can also be obtained from “nutrient supplements”, such as polyunsaturated fatty acids (PUFAs), vitamins, minerals, antioxidants, amino acids and pre/probiotic supplements. Recently, a large number of meta‐analyses have emerged examining nutrient supplements in the treatment of mental disorders. To produce a meta‐review of this top‐tier evidence, we identified, synthesized and appraised all meta‐analyses of randomized controlled trials (RCTs) reporting on the efficacy and safety of nutrient supplements in common and severe mental disorders. Our systematic search identified 33 meta‐analyses of placebo‐controlled RCTs, with primary analyses including outcome data from 10,951 individuals. The strongest evidence was found for PUFAs (particularly as eicosapentaenoic acid) as an adjunctive treatment for depression. More nascent evidence suggested that PUFAs may also be beneficial for attention‐deficit/hyperactivity disorder, whereas there was no evidence for schizophrenia. Folate‐based supplements were widely researched as adjunctive treatments for depression and schizophrenia, with positive effects from RCTs of high‐dose methylfolate in major depressive disorder. There was emergent evidence for N‐acetylcysteine as a useful adjunctive treatment in mood disorders and schizophrenia. All nutrient supplements had good safety profiles, with no evidence of serious adverse effects or contraindications with psychiatric medications. In conclusion, clinicians should be informed of the nutrient supplements with established efficacy for certain conditions (such as eicosapentaenoic acid in depression), but also made aware of those currently lacking evidentiary support. Future research should aim to determine which individuals may benefit most from evidence‐based supplements, to further elucidate the underlying mechanisms.     

Effects of heat and UV radiation on the mobilization of transposon mariner-Mos1

There are many complex interactions between transposable elements (TEs) and host genomes. Environmental changes that induce stressful conditions help to contribute for increasing complexity of these interactions. The transposon mariner-Mos1 increases its mobilization under mild heat stress. It has putative heat shock elements (HSEs), which are probably activated by heat shock factors (HSFs). Ultraviolet radiation (UVC) is a stressor that has been suggested as able to activate heat shock protein genes (Hsp). In this study, we test the hypothesis that if UVC induces Hsp expression, as heat does, it could also promote mariner-Mos1 transposition and mobilization. The Drosophila simulans white-peach is a mutant lineage that indicates the mariner-Mos1 transposition phenotypically through the formation of mosaic eyes. This lineage was exposed to UVC or mild heat stress (28 °C) in order to evaluate the induction of mariner-Mos1 expression by RT-qPCR, as well as the mariner-Mos1 mobilization activity based on the count number of red spots in the eyes. The effects of both treatments on the developmental time of flies and cell cycle progression were also investigated. Both the analysis of eyes and mariner-Mos1 gene expression indicate that UVC radiation has no effect in mariner-Mos1 transposition, although heat increases the expression and mobilization of this TE soon after the treatment. However, the expression of Hsp70 gene increased after 24 h of UVC exposure, suggesting different pathway of activation. These results showed that heat promotes mariner-Mos1 mobilization, although UVC does not induce the expression or mobilization of this TE.

Electronic supplementary material

The online version of this article (doi:10.1007/s12192-015-0611-2) contains supplementary material, which is available to authorized users.     

Exposure of Petunia Seedlings to Ethylene Decreased Apical Dominance by Reducing the Ratio of Auxin to Cytokinin

Seedlings of Petunia x hybrida ‘Orchid’ treated with the ethylene-releasing compound ethephon at 0.9, 1.7, and 3.5 mM evolved ethylene at a higher rate as the concentration of ethephon increased. Regardless of the concentration of ethephon applied, ethylene evolution peaked 6 to 8 h following application. Evidence that ethephon application decreased apical dominance included an increase in the number of new nodes on the main stem and a sustained increase in the length of new and existing lateral shoots compared to the control (no ethephon). Plants treated with 3.5 mM ethephon developed mild chlorosis, whereas a concentration of 1.7 mM ethephon decreased apical dominance without phytotoxic effects. The auxin/cytokinin ratio decreased in the apical shoot section as early as 1 h after ethephon treatment. In contrast, a decrease in the ratio in the subapical shoot section was not detected until 24 h after ethephon application. Reduction in auxin/cytokinin ratio was a result of a decrease in indole-3-acetic acid (IAA) and an increase of zeatin riboside (ZR), but not isopentenyladenosine (iPA). These results suggest that exposing ‘Orchid’ petunia seedlings to ethylene via ethephon lowers the auxin/cytokinin ratio, thereby promoting the outgrowth of lateral shoots.     

MxiM and MxiJ, Base Elements of the Mxi-Spa Type III Secretion System of Shigella, Interact with and Stabilize the MxiD Secretin in the Cell Envelope

The type III secretion pathway is broadly distributed across many parasitic bacterial genera and serves as a mechanism for delivering effector proteins to eukaryotic cell surface and cytosolic targets. While the effectors, as well as the host responses elicited, differ among type III systems, they all utilize a conserved set of 9 to 11 proteins that together form a bacterial envelope-associated secretory organelle or needle complex. The general structure of the needle complex consists of a transenvelope base containing at least three ring-forming proteins (MxiD, MxiJ, and MxiG in Shigella) that is connected to a hollow needle-like extension that projects away from the cell surface. Several studies have shown that the initial steps in needle complex assembly require interactions among the base proteins, although specific details of this process remain unknown. Here we identify a role for another base element in Shigella, MxiM, in interactions with the major outer-membrane-associated ring-forming protein, MxiD. MxiM affects several features of MxiD, including its stability, envelope association, and assembly into homomultimeric structures. Interestingly, many of the effects were also elicited by the inner-membrane-associated base element, MxiJ. We confirmed that MxiM-MxiD and MxiJ-MxiD interactions occur in vivo in the cell envelope, and we present evidence that together these base elements can form a transmembrane structure which is likely an important intermediary in the process of needle complex assembly.     

Organisation and expression of a wound/ripening-related small multigene family from tomato

cDNA clones derived from a ripe tomato fruit cDNA library were used to investigate changes in the abundance of specific mRNAs in ripening fruit and wounded leaves. mRNAs related to one cDNA clone (pTOM 13) were expressed in both situations. This clone was used to identify homologous sequences in a tomato genomic library. Three groups of related clones that hybridised to the pTOM 13 cDNA insert were identified and subcloned into plasmid vectors. Genomic Southern analysis of tomato DNA using gene-specific DNA fragments isolated from the subcloned DNAs indicated that all pTOM 13 closely related genes had been isolated. RNA dot blot analysis with these DNA fragments as probes indicated differential expression of this small multigene family in leaves and fruit.     

Human TCR transgenic Bet v 1-specific Th1 cells suppress the effector function of Bet v 1-specific Th2 cells

Pollinosis to birch pollen is a common type I allergy in the Northern Hemisphere. Moreover, birch pollen-allergic individuals sensitized to the major birch pollen allergen Bet v 1 frequently develop allergic reactions to stone fruits, hazelnuts, and certain vegetables due to immunological cross-reactivity. The major T cell epitope Bet v 1(142-153) plays an important role in cross-reactivity between the respiratory allergen Bet v 1 and its homologous food allergens. In this study, we cloned and functionally analyzed a human αβ TCR specific for the immunodominant epitope Bet v 1(142-153). cDNAs encoding TCR α- and β-chains were amplified from a Bet v 1(142-153)-specific T cell clone, introduced into Jurkat T cells and peripheral blood T lymphocytes of allergic and nonallergic individuals, and evaluated functionally. The resulting TCR transgenic (TCRtg) T cells responded in an allergen-specific and costimulation-dependent manner to APCs either pulsed with Bet v 1(142-153) peptide or coexpressing invariant chain::Bet v 1(142-153) fusion proteins. TCRtg T cells responded to Bet v 1-related food and tree pollen allergens that were processed and presented by monocyte-derived dendritic cells. Bet v 1(142-153)-presenting but not Bet v 1(4-15)-presenting artificial APCs coexpressing membrane-bound IL-12 polarized allergen-specific TCRtg T cells toward a Th1 phenotype, producing high levels of IFN-γ. Coculture of such Th1-polarized T cells with allergen-specific Th2-differentiated T cells significantly suppressed Th2 effector cytokine production. These data suggest that human allergen-specific TCR can transfer the fine specificity of the original T cell clone to heterologous T cells, which in turn can be instructed to modulate the effector function of the disease initiating/perpetuating allergen-specific Th2-differentiated T cells.     

A structural basis for the allosteric regulation of non-hydrolysing UDP-GlcNAc 2-epimerases

The non-hydrolysing bacterial UDP-N-acetylglucosamine 2-epimerase (UDP-GlcNAc 2-epimerase) catalyses the conversion of UDP-GlcNAc into UDP-N-acetylmannosamine, an intermediate in the biosynthesis of several cell-surface polysaccharides. This enzyme is allosterically regulated by its substrate UDP-GlcNAc. The structure of the ternary complex between the Bacillus anthracis UDP-GlcNAc 2-epimerase, its substrate UDP-GlcNAc and the reaction intermediate UDP, showed direct interactions between UDP and its substrate, and between the complex and highly conserved enzyme residues, identifying the allosteric site of the enzyme. The binding of UDP-GlcNAc is associated with conformational changes in the active site of the enzyme. Kinetic data and mutagenesis of the highly conserved UDP-GlcNAc-interacting residues confirm their importance in the substrate binding and catalysis of the enzyme. This constitutes the first example to our knowledge, of an enzymatic allosteric activation by direct interaction between the substrate and the allosteric activator.     

Identifying Active Phage Lysins through Functional Viral Metagenomics

Recent metagenomic sequencing studies of uncultured viral populations have provided novel insights into the ecology of environmental bacteriophage. At the same time, viral metagenomes could also represent a potential source of recombinant proteins with biotechnological value. In order to identify such proteins, a novel two-step screening technique was devised for cloning phage lytic enzymes from uncultured viral DNA. This plasmid-based approach first involves a primary screen in which transformed Escherichia coli clones that demonstrate colony lysis following exposure to inducing agent are identified. This effect, which can be due to the expression of membrane-permeabilizing phage holins, is discerned by the development a hemolytic effect in surrounding blood agar. In a secondary step, the clones identified in the primary screen are overlaid with autoclaved Gram-negative bacteria (specifically Pseudomonas aeruginosa) to assay directly for recombinant expression of lytic enzymes, which are often encoded proximally to holins in phage genomes. As proof-of-principle, the method was applied to a viral metagenomic library constructed from mixed animal feces, and 26 actively expressed lytic enzymes were cloned. These proteins include both Gram-positive-like and Gram-negative-like enzymes, as well as several atypical lysins whose predicted structures are less common among known phage. Overall, this study represents one of the first functional screens of a viral metagenomic population, and it provides a general approach for characterizing lysins from uncultured phage.The field of metagenomics has expanded rapidly in recent years, providing access to environmental microorganisms that would remain unapproachable by standard, culture-based methods. The foundation of metagenomics lies in the direct extraction of DNA/RNA from environmental samples (e.g., soil, water, or feces) without prior isolation of individual microbial species (reviewed in references 18 and 32). It has been estimated that only a small proportion of naturally occurring microbes—approximately 1% of soil bacteria, for instance—are culturable under standard laboratory conditions (31). In this light, metagenomics has become an increasingly common tool for studying diverse ecosystems, from around the globe to within the human body.Overall, metagenomics research can be divided into two general categories: sequence-based and functional. In the former, environmental DNA is sequenced in mass and compared with genetic databases to address broad questions of ecology, taxonomy, and diversity. Some of the most extensive metagenomic studies to date have been sequence based in nature, benefiting from the development of high-throughput sequencing technologies. Notable examples include a 76-megabase study of an acid mine biofilm (33), a 1-gigabase analysis of the Sargasso Sea (35), and a 6.3-gigabase sampling of global oceanic samples (25). In functional metagenomics, by contrast, environmental genes are recombinantly expressed within a host organism, which is monitored for the acquisition of a desired phenotype. Rather than providing insight into entire ecosystems, functional studies aim to identify individual molecules with biomedical or industrial value. Targeted compounds may be either proteins (usually enzymes) encoded directly by environmental genes or small molecules synthesized by several enzymes of a gene cluster. Numerous classes of molecules have been identified to date, with particular interest in the areas of biosynthesis, biomass degradation, and antibiotic discovery (reviewed in references 2, 34, and 36).While bacteria provide the majority of DNA to most metagenomic pools, recent studies have begun focusing on subsets of total environmental populations. A prominent example is viral metagenomics, in which viral particles (predominately bacteriophage) are purified from cellular material prior to DNA extraction (reviewed in references 10 and 12). Although the yield of DNA from environmental phage isolates is generally low, PCR amplification techniques have been developed to overcome this issue (4, 26). Viral metagenomic analyses have been conducted on a growing number of samples, including ones purified from soil (15), seawater (4, 39), and human feces (3). These studies have revealed a remarkable abundance of novel sequences, supporting the notion that phage represent the largest source of untapped genetic diversity on the planet (19). Despite this wealth of information, viral metagenomic studies to date have remained predominantly sequence based in nature. In this regard, functional screens of viral metagenomes could provide a large source of recombinant molecules.Recently one class of phage-encoded protein has received particular attention from the biotechnology field: phage lytic enzymes (also referred to as endolysins or lysins) (reviewed in references 16 and 17). These peptidoglycan hydrolases are expressed late in the infective cycle of double-stranded DNA phage, and—along with a membrane-permeabilizing protein known as a holin—they are responsible for disrupting the bacterial cell envelope and freeing progeny viral particles. Despite this conserved biological function, phage lysins (especially Gram-positive ones) are a tremendously diverse group of proteins whose enzymatic specificity includes various bonds within the peptidoglycan macromolecule. They include glycosyl hydrolases that target the polysaccharide backbone (muramidases/lysozymes and glucosaminidases), alanine amidases that target the initial l-alanine of the pentapeptide stem, and endopeptidases that target subsequent peptide bonds in the stem or cross bridge. While lysins of Gram-negative phage generally consist of an enzymatic domain alone, Gram-positive lysins are modular and combine an N-terminal lytic domain with a C-terminal binding domain that can recognize various epitopes within the target cell envelope.Although researchers have known of lysins for decades, interest has increased markedly in recent years after it was proposed that they could act as novel anti-infective agents against Gram-positive pathogens, whose peptidoglycan is directly accessible from the extracellular space (8, 23, 28). A growing number of in vitro and in vivo studies have confirmed the ability of recombinantly expressed lysins to kill such organisms, and their appeal lies in both the potency and the specificity they demonstrate toward individual Gram-positive species. This enzybiotic value of phage lysins goes alongside additional proposed applications in the areas of food (11), agricultural (20), veterinary (7), and industrial science (21, 40).Considering this potential, lytic enzymes represent an intriguing functional target for viral metagenomic screens. At the same time, identifying lysins in this manner would present several distinct challenges. Aside from general concerns common to all functional screens (e.g., protein expression and solubility), metagenomic lysin identification would face the following particular issues. (i) Clonal toxicity: recombinant lysin expression is typically well tolerated by host bacteria, since the enzymes are sequestered in the cytoplasm away from the peptidoglycan layer. Holins, on the other hand, interact nonspecifically with plasma membranes and are generally toxic to an Escherichia coli host, inducing bacteriolysis from within (9). Since holins are short (∼100 residues) and are often encoded adjacent to lysins, they can lead to selective toxicity of many of the clones one hopes to identify. In a metagenomic screen, where numerous lysins are present within a single library, this effect could lead to a significant loss of positive hits. (ii) Target bacterial species: in standard phage genomic screens, lysin-encoding clones are selected by their ability to kill the host bacterium of the encoding phage, which generally demonstrates the highest sensitivity (27). In a metagenomic screen, however, numerous host species of unknown origin could be present within a sample, confounding this choice of screening agent.To address these issues, we have devised a novel functional strategy for the general cloning of lytic enzymes from uncultured phage DNA. It utilizes a plasmid-based E. coli expression system and consists of a two-step process. Following induction by arabinose, clones are first screened for holin-mediated lysis by a hemolytic effect they create in the surrounding blood agar. These initial hits are then restreaked as patches and overlaid with Gram-negative cells whose outer membranes have been permeabilized by autoclaving, serving as a general source of peptidoglycan. The clones are observed for surrounding Gram-negative clearing zones to assay directly for the recombinant production of lytic enzymes encoded adjacent to the holins. As proof-of-principle, we applied our methodology to a viral metagenomic library constructed from mixed animal feces, identifying 26 actively expressed lysins of diverse molecular architectures. The first of its kind, this study presents a general model for lysin identification through viral metagenomics, highlighting the potential of this field for cloning of proteins of biotechnological or academic value.