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Mechanisms4 sources

Microbiome Diversity Metrics (Alpha and Beta Diversity)

This knowledge-base record is being expanded from WikiBiome’s evidence graph.

Mechanisms12 sources

Microbiome-Derived Metabolites

Microbiome-derived metabolites are small molecules made, consumed, or chemically transformed through activity in the gut microbiome and other host-associated communities. They connect community function to host biology, but the phrase covers several kinds of provenance:…

An epithelial cutaway appears separately from five generic microbial forms and four differently shaded spheres.

Mechanisms8 sources

Dietary Metal-Microbiome Interactions

Every meal delivers metals to the gut lumen — essential minerals, trace elements, and contaminants alike. These metals do not passively transit the GI tract. They actively reshape the microbial ecosystem, selecting for metal-tolerant organisms, enabling virulence in met…

Mechanisms8 sources

Gut Microbiome

The community of trillions of microorganisms — bacteria, archaea, fungi (mycobiome), viruses, and bacteriophages — inhabiting the human gastrointestinal tract, with the highest density in the colon (~10¹¹ cells/g). The gut microbiome encodes 100–150 times more genes tha…

An open gastrointestinal trough, four separate generic microbial forms, and three matching unmarked silver material coupons form unconnected groups.

Mechanisms22 sources

Gut-Metal-Microbiome Interactions

The relationship between heavy metals and the gut microbiota is bidirectional: metals reshape microbial community composition and metabolic output, while the microbiota modulates metal absorption, speciation, and toxicity. The gut microbiota serves as the first line of …

Mechanisms8 sources

Oral Microbiome

The oral microbiome is the second most complex microbial community in the human body after the gut, harboring ~700 species across distinct niches (tongue, buccal mucosa, gingival crevice, saliva, dental plaque). While traditionally studied in the context of dental disea…

Mechanisms3 sources

Semen Microbiome

The semen microbiome refers to the microbial community inhabiting the male reproductive tract and seminal fluid. Core genera identified through shotgun metagenomic sequencing include Corynebacterium, Staphylococcus, Streptococcus, and Prevotella, though composition vari…

Mixed generic bacterial forms, a sample tube with an unlabeled DNA model, and an abstract read-like panel appear separately.

Mechanisms6 sources

16S rRNA Sequencing

16S rRNA gene sequencing is the most widely used method for characterizing bacterial communities in this wiki. It targets the ~1,500 base pair 16S ribosomal RNA gene, which contains nine hypervariable regions (V1–V9) flanked by conserved sequences. Universal primers amp…

A generic ribbon-like protein, three separate ligand-like forms, and a nucleus model with paired protein forms and DNA appear separately.

Mechanisms5 sources

AhR (Aryl Hydrocarbon Receptor)

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that functions as a master sensor at the intersection of gut microbial metabolism, environmental chemical exposure, and immune regulation. It is expressed broadly across immune cells, intesti…

An unlabeled fused steroid-ring scaffold, a five-part membrane-channel model, and a generic neuron appear separately.

Mechanisms5 sources

Allopregnanolone

Allopregnanolone (3α-hydroxy-5α-pregnan-20-one) is a neurosteroid metabolite of progesterone that is the most potent endogenous positive allosteric modulator of GABA-A receptors. It is central to the pathophysiology of PMDD and postpartum depression — conditions where a…

Paired kidney cutaways, a generic single-pass membrane protein, and a separate soluble protein teaching form appear separately.

Mechanisms3 sources

Alpha-Klotho

An anti-aging protein that has emerged as a critical mediator between heavy metal exposure and chronic kidney disease progression. Originally discovered as a gene whose mutation caused premature aging in mice, alpha-klotho is now understood to be a multifunctional prote…

A synaptic-terminal cutaway, one long generic protein chain, and three separate short chains appear as distinct teaching groups.

Mechanisms7 sources

Alpha-Synuclein

A 140-amino-acid presynaptic protein whose misfolding into insoluble fibrils and their deposition in Lewy bodies is the defining neuropathological hallmark of parkinsons disease and the broader family of synucleinopathies (including Lewy body dementia and multiple syste…

Mechanisms4 sources

Ammonia

Ammonia is a nitrogen-containing product of microbial urease activity. When urease hydrolyzes urea, ammonia and bicarbonate are produced; in the microbial systems covered by WikiBiome, those products can provide nitrogen and raise local pH maier 2019 nickel microbial pa…

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Mechanisms7 sources

Amyloid-Beta

Amyloid-beta (Aβ) is a 36–43 amino acid peptide derived from the proteolytic cleavage of amyloid precursor protein (APP) by beta-secretase (BACE1) and gamma-secretase. Its aggregation from soluble monomers into insoluble fibrillar plaques in the brain is the defining ne…

One isolated ribbon, four separate ribbons, and an ordered five-ribbon bundle appear as three distinct teaching groups.

Mechanisms8 sources

Amyloid-Beta Aggregation

The process by which soluble amyloid-beta (Aβ) monomers assemble into neurotoxic oligomers and insoluble fibrillar plaques in the brain -- the defining neuropathological event of alzheimers disease. What distinguishes WikiBiome's treatment of this process from conventio…

Mixed generic bacteria, a dish with six unmarked discs, and a bacterial cutaway with a closed DNA ring and membrane pump-like form appear separately.

Mechanisms7 sources

Antimicrobial Resistance

The ability of microorganisms to survive and replicate in the presence of antimicrobial agents — antibiotics, antifungals, antivirals, antiparasitic drugs — at concentrations that would normally inhibit or kill them. Antimicrobial resistance (AMR) is designated by the W…

Mechanisms5 sources

Arachidonic Acid

Arachidonic acid (AA) is a 20-carbon omega-6 polyunsaturated fatty acid (20:4n-6) that serves as the primary substrate for prostaglandin and leukotriene synthesis via COX-2 and 5-LOX pathways. It is the dominant pro-inflammatory lipid mediator — and its balance with ant…

A generic membrane-embedded protein with an internal heme-like disc and two separate unlabeled four-ring steroid scaffolds appear as three groups.

Mechanisms5 sources

Aromatase

Aromatase (CYP19A1) is the cytochrome P450 enzyme that catalyzes the final and rate-limiting step of estrogen biosynthesis — the conversion of androgens (testosterone, androstenedione) to estrogens (estradiol, estrone). It is expressed in the ovaries, placenta, adipose …

A generic receptor protein and small fused-ring token appear separately from a nucleus cutaway and a short DNA double helix.

Mechanisms8 sources

Aryl Hydrocarbon Receptor (AhR)

This page serves as a cross-reference point for the existing ahr concept page, which provides comprehensive coverage of AhR signaling, microbiome-derived ligands, and immune regulation. The aryl hydrocarbon receptor is a ligand-activated transcription factor that integr…

Mechanisms3 sources

Aspirin

Aspirin (acetylsalicylic acid) is a non-steroidal anti-inflammatory drug (NSAID) that irreversibly inhibits cyclooxygenase (COX) enzymes, suppressing prostaglandin synthesis. While widely used as an antiplatelet and anti-inflammatory agent, aspirin carries significant i…

Two complete teaching models show longitudinal and circular artery cutaways with patent lumens and restrained eccentric intimal plaque.

Mechanisms3 sources

Atherosclerosis

Progressive inflammatory disease of the arterial wall characterized by lipid accumulation, immune cell infiltration, and fibrous plaque formation. In the metallomics framework, atherosclerosis sits at the convergence of three interacting systems: heavy metal toxicity, g…

An open membrane cup, a closed double-membrane cargo vesicle, and a lysosome-like vesicle beside another closed cargo vesicle appear as three groups.

Mechanisms8 sources

Autophagy

Autophagy (from Greek, "self-eating") is the cellular process of degrading and recycling damaged organelles, misfolded proteins, and intracellular pathogens through lysosomal digestion. It is the cell's primary quality control mechanism -- a housekeeping system that bec…

Complete uterine anatomy, eight generic rods, and a projected membrane fragment appear as three separate non-contacting teaching groups.

Mechanisms11 sources

Bacterial Contamination Hypothesis

The bacterial contamination hypothesis proposes that bacterial endotoxin (LPS) contamination of menstrual blood and endometrial tissue is a key driver of endometriosis pathogenesis. First formalized by Khan et al. (2018), this hypothesis shifts endometriosis from a pure…

A complete mucosal teaching cutaway is separated from one orderly four-rod group and one mixed six-form microbial group.

Mechanisms3 sources

Bacterial Vaginosis

Bacterial vaginosis (BV) is the most common vaginal infection in women of reproductive age, affecting an estimated 29% of women globally. Rather than an infection by a single pathogen, BV represents a polymicrobial dysbiotic state -- a collapse of the protective Lactoba…

Three separated teaching models show a tailed icosahedral bacteriophage-like form, a flexible filamentous form, and a small tailless icosahedral form.

Mechanisms14 sources

Bacteriophages

Viruses that exclusively infect bacteria. Bacteriophages -- phages for short -- are the most abundant biological entities on Earth, outnumbering bacteria in most environments by ratios of 1:1 to 10:1. In the human gut, the phageome represents a powerful but underexplore…

Mechanisms4 sources

BDNF (Brain-Derived Neurotrophic Factor)

BDNF is the primary neurotrophin supporting neuronal survival, synaptic plasticity, and memory formation in the hippocampus and prefrontal cortex. Reduced BDNF is a consistent finding in depression, schizophrenia, and neurodegeneration. The gut microbiome modulates BDNF…

A compact generic four-lobed enzyme form is separated from one linked ring-and-aglycone context token and one separated product-context pair.

Mechanisms7 sources

Beta-Glucuronidase

Beta-glucuronidase (β-glucuronidase, EC 3.2.1.31) is an enzyme that catalyzes the hydrolysis of glucuronidated compounds, cleaving the β-1,4-glycosidic bond between a sugar and a glucuronic acid group. In the microbiome, beta-glucuronidase is the key enzyme of the estro…

Mechanisms8 sources

Bile Acid Metabolism

Bile acids are cholesterol-derived amphipathic molecules synthesized in the liver, secreted into the duodenum, and extensively modified by gut bacteria. The host-microbe co-metabolism of bile acids creates a signaling network with profound effects on lipid metabolism, g…

Mechanisms3 sources

Biomarkers

Measurable indicators of biological state, exposure, or disease. In the metallomics context, biomarkers span three interconnected domains: metal biomarkers (quantifying exposure and body burden), microbiome biomarkers (reflecting microbial community disruption), and met…

Mechanisms3 sources

Blood-Brain Barrier

A selective semipermeable border formed by brain endothelial cells connected by tight junctions, pericytes, and astrocytic end-feet. The BBB restricts passage of most molecules from blood to brain, protecting the CNS from toxins, pathogens, and inflammatory mediators. M…

Three separated generic fused-ring teaching tokens share a family motif while differing in their unlabeled peripheral forms.

Mechanisms3 sources

Cephalosporins

Cephalosporins are a class of beta-lactam antibiotics (five generations) that inhibit bacterial cell wall synthesis by binding penicillin-binding proteins. They are among the most prescribed antibiotic classes and among the most disruptive to the gut microbiome.

An open ligand teaching form, an isolated metal sphere, and a separate closed ligand-and-sphere model appear without arrows.

Mechanisms3 sources

Chelation Therapy

Chelation therapy uses high-affinity metal-binding molecules to form stable, excretable complexes with toxic metals, removing them from the body. The term derives from Greek "chele" (claw) -- the chelator grips the metal ion at multiple coordination sites. While chelati…

An intact epithelial cutaway, a separate mixed six-form microbial group, and two separate outside rods appear without contact.

Mechanisms3 sources

Colonization Resistance

The collective ability of the resident gut microbiome to prevent colonization by exogenous pathogens and suppress expansion of resident pathobionts. Colonization resistance is not a property of any single organism but an emergent function of the whole microbial communit…

Mechanisms3 sources

Comorbidities

The co-occurrence of multiple diseases in the same individual at rates exceeding chance. Comorbidity patterns are a central puzzle in medicine -- why do IBD patients develop CVD? Why does PCOS cluster with T2D? Why do neurodegenerative diseases associate with depression…

A five-recess epithelial strip appears separately from five varied microbial forms and two additional outside rods.

Mechanisms5 sources

Competitive Exclusion

Competitive exclusion is the ecological principle that two species competing for the same limiting resource cannot coexist indefinitely — one will outcompete the other. In the gut microbiome, competitive exclusion is the primary mechanism by which commensal bacteria pre…

Mechanisms5 sources

Cortisol

Cortisol is the primary glucocorticoid stress hormone, produced by the adrenal cortex under HPA (hypothalamic-pituitary-adrenal) axis control. In the WikiBiome framework, cortisol is the molecular bridge between psychological stress and microbiome disruption — it direct…

A generic membrane-associated two-subunit enzyme model appears separately from a bent chain and a five-membered-ring token.

Mechanisms6 sources

COX-2 (Cyclooxygenase-2)

Cyclooxygenase-2 (COX-2) is the inducible enzyme that converts arachidonic acid to prostaglandin H₂ — the precursor of prostaglandin E₂ (PGE₂), prostacyclin, and thromboxane. Unlike COX-1 (constitutive, homeostatic), COX-2 is transcriptionally induced by nf kappa b duri…

Three short rods, two curved rods, four silver-blue spheres, and three copper-colored spheres form four separate groups.

Mechanisms4 sources

Cross-Feeding

Cross-feeding (syntrophy) is the metabolic cooperation in which one organism's waste product becomes another's substrate. It is the cooperative counterpart to competitive exclusion — rather than competing for the same resource, organisms partition metabolic labor into s…

A generic mitochondrion-like cutaway appears separately from four copper-colored spheres and three folded protein-like forms.

Mechanisms4 sources

Cuproptosis

A distinct form of regulated cell death caused by excess intracellular copper binding to lipoylated proteins in the TCA cycle, first characterized by Tsvetkov et al. in Science (2022). Unlike ferroptosis (iron-dependent lipid peroxidation) or apoptosis (caspase-dependen…

Three separated generic compact peptide teaching forms each contain three copper-colored bridge-like crosslinks.

Mechanisms3 sources

Defensins

Defensins are small (29–45 amino acid) cationic antimicrobial peptides that form the first line of chemical defense at mucosal surfaces. Alpha-defensins (HD5, HD6) are produced by Paneth cells in the small intestinal crypts; beta-defensins (hBD1-4) are produced by epith…

A molar cutaway with a shallow surface depression appears separately from a five-form plaque model and four mineral-context spheres.

Mechanisms4 sources

Dental Caries

Dental caries (tooth decay) is the most prevalent chronic disease worldwide, driven by acid-producing biofilm bacteria — primarily Streptococcus mutans and Lactobacillus species — that demineralize tooth enamel. In the WikiBiome framework, dental caries connects to the …

Mechanisms20 sources

Developmental Metal Vulnerability: Critical Windows of Susceptibility

This page unifies the infant formula contamination, pregnancy complications, autism spectrum disorder, necrotizing enterocolitis, and neurodevelopmental toxicity threads around a single organizing insight: metal toxicity is disproportionately severe during specific deve…

A water droplet and a dish of seven grain-like forms appear separately from three slate spheres and one smaller copper-colored sphere.

Mechanisms6 sources

Dietary Arsenic Exposure

arsenic (As) is unique among dietary heavy metals because it exists in two fundamentally different forms with dramatically different toxicities: inorganic arsenic (iAs, the dangerous form) and organic arsenic (arsenobetaine, arsenosugars — largely non-toxic). Understand…

A water droplet and a dish with three leafy and three granular plant-food groupings appear separately from four silver spheres.

Mechanisms6 sources

Dietary Cadmium Exposure

cadmium (Cd) enters the human body primarily through food. Unlike nickel, which has high-concentration food categories that can be avoided, cadmium contamination is diffuse — embedded in staple crops, leafy greens, and grains that form the basis of most dietary patterns…

Mechanisms5 sources

Dietary Lead Exposure

lead (Pb) has no safe level of exposure. Unlike most dietary metals, lead does not play any known biological role — every atom absorbed represents toxic burden. While environmental lead exposure (paint, soil, air) has decreased dramatically since leaded gasoline phase-o…

A closed capsule, a six-well screening plate with one sphere per well, and a folded target-like form with an empty pocket appear separately.

Mechanisms5 sources

Drug Repurposing

Drug repurposing (also called drug repositioning) is the strategy of identifying new therapeutic uses for existing approved drugs. It dramatically accelerates the path from bench to bedside because safety, pharmacokinetics, and manufacturing are already established. In …

A microscopy-informed mixed microbial community with rods, cocci, curved rods, and branching forms on a pale cool field.

Mechanisms14 sources

Dysbiosis

Disruption of the normal composition and metabolic function of microbial communities, particularly the gut microbiome. In the metallomics context, dysbiosis is both a consequence of metal toxicity and an amplifier of further disease -- creating vicious cycles where meta…

Mechanisms6 sources

Dysmenorrhea

Dysmenorrhea -- painful menstruation -- is the most common gynecological complaint, affecting 50-90% of reproductive-age women. It is classified as primary (no identifiable pelvic pathology) or secondary (caused by conditions such as endometriosis, adenomyosis, or fibro…

Mechanisms8 sources

EDTA

Ethylenediaminetetraacetic acid (EDTA) is a synthetic aminopolycarboxylic acid widely used as a chelation agent for heavy metal poisoning, particularly lead. In the microbiome context, EDTA is significant for two reasons: its therapeutic use in metal detoxification and …

A two-bilayer envelope with a tripartite pump, a separate one-bilayer carrier model, and five substrate-context tokens form three groups.

Mechanisms3 sources

Efflux Pumps

Membrane-spanning protein complexes that actively export substrates from the bacterial cell, using energy from ATP hydrolysis or the proton motive force. In the context of metal-microbiome biology, efflux pumps serve a dual role that has profound clinical consequences: …

Three receptor-pocket teaching forms show a seated round token, a distinct seated token with a sphere nearby, and a pocket-covering token with a sphere nearby.

Mechanisms5 sources

Endocrine Disruption

Endocrine-disrupting chemicals (EDCs) are exogenous substances that interfere with hormone synthesis, secretion, transport, binding, action, or elimination. The classical EDC list -- BPA, phthalates, dioxins, PCBs, pesticides -- is well established. What WikiBiome adds …

Mechanisms8 sources

Endocrine Disruptors

Exogenous chemicals that interfere with hormone synthesis, secretion, transport, binding, or elimination, mimicking or blocking endogenous hormones at physiologically relevant concentrations. In the metallomics-microbiome framework, endocrine disruptors occupy a critica…

A patent vessel with four red-cell-like discs, a separate six-cell endothelial tile, and four paired context objects form three groups.

Mechanisms6 sources

Endothelial Dysfunction

Endothelial dysfunction is the impairment of the vascular endothelium's ability to produce nitric oxide (NO), regulate vascular tone, and prevent thrombosis. It is the earliest detectable stage of atherosclerosis and the mechanistic link between gut dysbiosis, systemic …

Mechanisms9 sources

Endotoxemia

Endotoxemia is the presence of bacterial endotoxin (lipopolysaccharide, LPS) in the bloodstream. Metabolic endotoxemia — chronic, low-grade LPS translocation from the gut — is a central mechanism linking dysbiosis to systemic disease across dozens of conditions in this …

Mechanisms6 sources

Epigenetic Modifications

Epigenetic modifications — heritable changes in gene expression without altering the DNA sequence — are a primary mechanism through which both heavy metals and the gut microbiome influence disease across the lifespan. The three major epigenetic mechanisms (DNA methylati…

An unmarked DNA helix, a chromatin ribbon with five nucleosome-like cores, and an RNA-like ribbon with two hairpins form three groups.

Mechanisms10 sources

Epigenetics

Epigenetics is the study of heritable changes in gene expression that occur without alterations to the DNA sequence itself. These changes -- primarily DNA methylation, histone modifications, and non-coding RNA regulation -- represent a molecular memory system that can b…

Mechanisms8 sources

Epithelial-Mesenchymal Transition

Epithelial-mesenchymal transition (EMT) is a cellular program in which polarized epithelial cells lose their cell-cell adhesion and acquire migratory, mesenchymal properties. While essential during embryonic development and wound healing, aberrant EMT activation drives …

Mechanisms3 sources

Essential Oils

Essential oils are volatile aromatic compounds extracted from plants, composed primarily of terpenes, phenylpropanoids, and their oxygenated derivatives. In the WikiBiome context, essential oils are relevant not as aromatherapy but as sources of bioactive molecules with…

An intestinal teaching cutaway with five generic microbial forms sits beside three DNA helices and three non-literal four-ring context tokens.

Mechanisms4 sources

Estrobolome

The estrobolome is the aggregate of enteric bacterial genes whose products are capable of metabolizing estrogens. First proposed by Plottel and Blaser (2011), the concept describes how the gut microbiome acts as an endocrine organ, modulating circulating estrogen levels…

A liver and gallbladder model, an intact intestinal barrier, and four separate four-ring tokens with two satellite beads appear as three unconnected groups.

Mechanisms3 sources

Estrogen Recirculation

Estrogen recirculation is the recycling loop by which conjugated estrogens excreted in bile are deconjugated by gut bacterial beta glucuronidase, reabsorbed across the intestinal epithelium, and returned to systemic circulation uzuner 2023 bidirectional relationship end…

Mechanisms8 sources

Farnesoid X Receptor (FXR)

The farnesoid X receptor (FXR), also known as NR1H4, is a nuclear receptor that functions as the primary bile acid sensor in the body. Activated by bile acids — especially chenodeoxycholic acid (CDCA) — FXR regulates bile acid synthesis, cholesterol metabolism, glucose …

Mechanisms4 sources

Fecal Microbiota Transplant (FMT)

The transfer of processed stool from a healthy donor into a recipient's gastrointestinal tract to restore a disrupted microbial community. FMT is the most direct form of microbiome intervention -- replacing the entire community rather than supplementing individual strai…

Mechanisms10 sources

Gut Barrier Dysfunction

Gut barrier dysfunction -- colloquially "leaky gut" -- is the pathological increase in intestinal permeability that permits translocation of bacteria, bacterial products (LPS, peptidoglycan), metals, and dietary antigens from the gut lumen into the systemic circulation.…

Mechanisms16 sources

Gut-Brain Axis

Bidirectional communication between the gut microbiota and the central nervous system, mediated by neural (vagus nerve, enteric nervous system), immune (cytokines, microglia), endocrine (HPA axis), and metabolic (SCFAs, neurotransmitter precursors, tryptophan metabolite…

Mechanisms8 sources

Gut-Gonadal Axis

The gut-gonadal axis describes the bidirectional communication between the intestinal microbiome and the reproductive endocrine system. Gut bacteria modulate sex hormone levels through enzymatic activity (particularly beta glucuronidase-mediated estrogen deconjugation),…

An open gastrointestinal trough, four separate generic microbial forms, and two external kidney models form three unconnected teaching groups.

Mechanisms8 sources

Gut-Kidney Axis

The gut-kidney axis describes the bidirectional relationship between the gut microbiome and kidney function. As kidney disease progresses, the resulting biochemical changes (uremia, altered pH, fluid shifts) reshape the gut microbiome. The dysbiotic microbiome, in turn,…

Mechanisms3 sources

Gut-Penis Axis

The gut-penis axis is an emerging concept describing the systemic pathway by which gut microbiome dysbiosis impairs erectile function through endothelial nitric oxide (NO) suppression and chronic inflammation. Though less established than the gut-brain or gut-heart axes…

An open gastrointestinal trough, four separate generic microbial forms, and a simplified normal bladder-neck and prostate model form unconnected groups.

Mechanisms3 sources

Gut-Prostate Axis

The gut-prostate axis describes the bidirectional communication between the gut microbiome and the prostate gland. Gut-derived microbial metabolites, inflammatory mediators, and immune signals influence prostatic health, while prostatic disease states alter systemic inf…

Mechanisms3 sources

Gut-Testis Axis

The gut-testis axis describes the bidirectional communication between the gut microbiome and the male reproductive system. Gut-derived microbial metabolites, immune signals, and systemic inflammatory mediators influence testicular function, testosterone biosynthesis, an…

Mechanisms3 sources

Gut-Thyroid Axis

The gut-thyroid axis describes the bidirectional communication between the gut microbiome and the thyroid gland. The thyroid regulates metabolism, energy homeostasis, and immune function -- and the microbiome influences thyroid physiology at every level: mineral absorpt…

Mechanisms5 sources

Gut-Vagina Axis

The gut-vagina axis describes the bidirectional relationship between the intestinal and vaginal microbiomes. Emerging evidence shows that gut microbial composition influences vaginal colonization patterns through immune modulation, metabolite exchange, and direct microb…

Mechanisms3 sources

Heavy Metal Neurotoxicity

heavy metals exert some of their most devastating effects on the nervous system. lead, mercury, and arsenic are the three metals with the most extensively documented neurotoxic mechanisms, but cadmium, manganese, aluminum, and nickel also contribute to neurological dama…

Mechanisms10 sources

Heavy Metals

Heavy metals is a widely used but chemically imprecise umbrella term for elements discussed because of their density, persistence, environmental occurrence, or toxicity. One common convention uses density above 5 g/cm3, but density alone does not determine biological ha…

Mechanisms5 sources

Homocysteine

Homocysteine is a sulfur-containing amino acid intermediate in the methionine cycle. Elevated plasma homocysteine (hyperhomocysteinemia) is an established risk factor for cardiovascular disease, endothelial dysfunction, and neurodegenerative disease. The gut microbiome …

Mechanisms8 sources

Horizontal Gene Transfer and Mobile Genetic Elements

Horizontal gene transfer (HGT) is the movement of genetic material between organisms outside of parent-to-offspring inheritance. In the gut microbiome, HGT -- primarily mediated by mobile genetic elements (MGEs) including plasmids, transposons, integrons, and integrativ…

Mechanisms4 sources

Human Milk Oligosaccharides (HMOs)

Human milk oligosaccharides are a diverse family of over 200 structurally distinct complex sugars found in breast milk. They are the third most abundant solid component of human milk (after lactose and lipids), yet they are not digestible by the infant. Their sole purpo…

Mechanisms6 sources

Hydrogen Sulfide (H₂S)

Hydrogen sulfide is a gaseous signaling molecule (gasotransmitter) produced by both host enzymes (CBS, CSE, 3-MST) and gut bacteria — primarily sulfate-reducing bacteria (desulfovibrio). Like nitric oxide and carbon monoxide, H₂S has dual roles: physiological signaling …

Mechanisms3 sources

Hyperaccumulator Plants

Hyperaccumulator plants are species that concentrate heavy metals in their tissues at 10–100× the levels found in non-accumulating species growing in the same soil. Over 700 plant species are known hyperaccumulators — primarily for nickel (~530 species), but also zinc, …

Mechanisms3 sources

Hyperandrogenism

Hyperandrogenism -- the clinical or biochemical excess of androgens (testosterone, androstenedione, DHEA-S) -- is a defining feature of polycystic ovary syndrome (PCOS), affecting 60-80% of women with the condition. It manifests as hirsutism, acne, androgenic alopecia, …

Mechanisms6 sources

Hyperparathyroidism

Hyperparathyroidism is the overproduction of parathyroid hormone (PTH), a master regulator of calcium homeostasis. While primary hyperparathyroidism (from parathyroid adenoma) is well described, the WikiBiome framework highlights secondary hyperparathyroidism -- the com…