It has become apparent that the molecular and biochemical integrity of interactive families, genera, and species of human gut microflora is critically linked to maintaining complex metabolic and behavioral processes mediated by peripheral organ systems and central nervous system neuronal groupings. Relatively recent studies have established intrinsic ratios of enterotypes contained within the human microbiome across demographic subpopulations and have empirically linked significant alterations in the expression of bacterial enterotypes with the initiation and persistence of several major metabolic and psychiatric disorders. Accordingly, the goal of our review is to highlight potential thematic/functional linkages of pathophysiological alterations in gut microbiota and bidirectional gut-brain signaling pathways with special emphasis on the potential roles of gut dysbiosis on the pathophysiology of psychiatric illnesses. We provide critical discussion of putative thematic linkages of Parkinson's disease (PD) data sets to similar pathophysiological events as potential causative factors in the development and persistence of diverse psychiatric illnesses. Finally, we include a concise review of preclinical paradigms that involve immunologically-induced GI deficits and dysbiosis of maternal microflora that are functionally linked to impaired neurodevelopmental processes leading to affective behavioral syndromes in the offspring.

Department of Psychiatry 1st Faculty of Medicine Charles University Prague and General University Hospital Prague Center for Cognitive and Molecular Neuroscience Ke Karlovu 11 120 00 Prague 2 Czech Republic

Warsaw Medical University Public Central Teaching Hospital Warsaw Poland

Zobrazit více v PubMed

Baganz NL, Blakely RD (2013) A dialogue between the immune system and brain, spoken in the language of serotonin. ACS Chem Neurosci 4:48–63. 10.1021/cn300186b PubMed PMC

Barthels C et al (2017) CD40-signalling abrogates induction of RORγt+ Treg cells by intestinal CD103+ DCs and causes fatal colitis. Nat Commun 8:14715. 10.1038/ncomms14715 PubMed PMC

Beaumont E et al (2017) Cervical vagus nerve stimulation augments spontaneous discharge in second- and higher-order sensory neurons in the rat nucleus of the solitary tract. Am J Physiol Heart Circ Physiol 313:H354-H367. 10.1152/ajpheart.00070.2017 PubMed PMC

Bedarf JR et al (2017) Functional implications of microbial and viral gut metagenome changes in early stage L-DOPA-naive Parkinson’s disease patients. Genome Med 9:39. 10.1186/s13073-017-0428-y PubMed PMC

Bieri G, Gitler AD, Brahic M (2017) Internalization, axonal transport and release of fibrillar forms of alpha-synuclein. Neurobiol Dis. 10.1016/j.nbd.2017.03.007 PubMed PMC

Bodea LG et al (2014) Neurodegeneration by activation of the microglial complement-phagosome pathway. J Neurosci 34:8546–8556. 10.1523/JNEUROSCI.5002-13.2014 PubMed PMC

Borodovitsyna O, Flamini M, Chandler D (2017) Noradrenergic modulation of cognition in health and disease. Neural Plast 2017:6031478 10.1155/2017/6031478 PubMed PMC

Borre YE, Moloney RD, Clarke G, Dinan TG, Cryan JF (2014) The impact of microbiota on brain and behavior: mechanisms & therapeutic potential. Adv Exp Med Biol 817:373–403. 10.1007/978-1-4939-0897-4_17 PubMed

Braak H, Del Tredici K (2017) Neuropathological staging of brain pathology in sporadic Parkinson’s disease: separating the wheat from the chaff. J Park Dis 7:S73–S87. 10.3233/JPD-179001 PubMed PMC

Braak H, Rub U, Gai WP, Del Tredici K (2003) Idiopathic Parkinson’s disease: possible routes by which vulnerable neuronal types may be subject to neuroinvasion by an unknown pathogen. J Neural Transm 110:517–536. 10.1007/s00702-002-0808-2 PubMed

Caputi V et al (2017) Antibiotic-induced dysbiosis of the microbiota impairs gut neuromuscular function in juvenile mice. Br J Pharmacol 174:3623–3639. 10.1111/bph.13965 PubMed PMC

Carreno FR, Frazer A (2017) Vagal nerve stimulation for treatment-resistant. Depress Neurother 14:716–727. 10.1007/s13311-017-0537-8 PubMed PMC

Coleman OI, Haller D (2017) Bacterial signaling at the intestinal epithelial interface in inflammation and cancer. Front Immunol 8:1927. 10.3389/fimmu.2017.01927 PubMed PMC

De Biase D, Pennacchietti E (2012) Glutamate decarboxylase-dependent acid resistance in orally acquired bacteria: function, distribution and biomedical implications of the gadBC operon. Mol Microbiol 86:770–786. 10.1111/mmi.12020 PubMed

De Filippis R et al (2012) Expanding the phenotype associated with FOXG1 mutations and in vivo FoxG1 chromatin-binding dynamics. Clin Genet 82:395–403. 10.1111/j.1399-0004.2011.01810.x PubMed

de Muinck EJ, Lundin KEA, Trosvik P (2017) Linking spatial structure and community-level biotic interactions through cooccurrence and time series modeling of the human intestinal microbiota. mSystems. 10.1128/mSystems.00086-17 PubMed PMC

Devos D et al (2013) Colonic inflammation in Parkinson’s disease. Neurobiol Dis 50:42–48. 10.1016/j.nbd.2012.09.007 PubMed

Diaz Heijtz R et al (2011) Normal gut microbiota modulates brain development and behavior. Proc Natl Acad Sci USA 108:3047–3052. 10.1073/pnas.1010529108 PubMed PMC

Dinan TG, Cryan JF (2017) Microbes, immunity, and behavior: psychoneuroimmunology meets the microbiome. Neuropsychopharmacology 42:178–192. 10.1038/npp.2016.103 PubMed PMC

Dinan TG, Stilling RM, Stanton C, Cryan JF (2015) Collective unconscious: how gut microbes shape human behavior. J Psychiatr Res 63:1–9. 10.1016/j.jpsychires.2015.02.021 PubMed

Dobbs RJ, Charlett A, Purkiss AG, Dobbs SM, Weller C, Peterson DW (1999) Association of circulating TNF-alpha and IL-6 with ageing and parkinsonism. Acta Neurol Scand 100:34–41 PubMed

Dworak M, Stebbing M, Kompa AR, Rana I, Krum H, Badoer E (2014) Attenuation of microglial and neuronal activation in the brain by ICV minocycline following myocardial infarction. Auton Neurosci 185:43–50. 10.1016/j.autneu.2014.03.007 PubMed

Esmaili A et al (2009) Enteropathogenic Escherichia coli infection inhibits intestinal serotonin transporter function and expression. Gastroenterology 137:2074–2083. 10.1053/j.gastro.2009.09.002 PubMed PMC

Farrand AQ, Helke KL, Gregory RA, Gooz M, Hinson VK, Boger HA (2017) Vagus nerve stimulation improves locomotion and neuronal populations in a model of Parkinson’s disease. Brain Stimul. 10.1016/j.brs.2017.08.008 [Epub ahead of print] PubMed PMC

Fearnley JM, Lees AJ (1991) Ageing and Parkinson’s disease: substantia nigra regional selectivity. Brain 114 (Pt 5):2283–2301 PubMed

Forsyth CB et al (2011) Increased intestinal permeability correlates with sigmoid mucosa alpha-synuclein staining and endotoxin exposure markers in early Parkinson’s disease. PLoS ONE 6:e28032. 10.1371/journal.pone.0028032 PubMed PMC

Frohlich EE et al (2016) Cognitive impairment by antibiotic-induced gut dysbiosis: analysis of gut microbiota-brain communication. Brain Behav Immun 56:140–155. 10.1016/j.bbi.2016.02.020 PubMed PMC

Gershon MD, Tack J (2007) The serotonin signaling system: from basic understanding to drug development for functional GI disorders. Gastroenterology 132:397–414. 10.1053/j.gastro.2006.11.002 PubMed

Giannoccaro MP, La Morgia C, Rizzo G, Carelli V (2017) Mitochondrial DNA and primary mitochondrial dysfunction in Parkinson’s disease. Mov Disord 32:346–363. 10.1002/mds.26966 PubMed

Hoffman JM et al (2012) Activation of colonic mucosal 5-HT(4) receptors accelerates propulsive motility and inhibits visceral hypersensitivity. Gastroenterology 142:844–854 e844. 10.1053/j.gastro.2011.12.041 PubMed PMC

Hsiao EY (2013) Immune dysregulation in autism spectrum disorder. Int Rev Neurobiol 113:269–302. 10.1016/B978-0-12-418700-9.00009-5 PubMed

Humann J et al (2016) Bacterial peptidoglycan traverses the placenta to induce fetal neuroproliferation and aberrant postnatal behavior. Cell Host Microbe 19:901. 10.1016/j.chom.2016.05.017 PubMed

Hyland NP, Cryan JF (2016) Microbe-host interactions: influence of the gut microbiota on the enteric nervous system. Dev Biol 417:182–187. 10.1016/j.ydbio.2016.06.027 PubMed

Ivanov AI (2012) Structure and regulation of intestinal epithelial tight junctions: current concepts and unanswered questions. Adv Exp Med Biol 763:132–148 PubMed

Jin Y, Kong J (2017) Transcutaneous vagus nerve stimulation: a promising method for treatment of autism spectrum disorders. Front Neurosci 10:609. 10.3389/fnins.2016.00609 PubMed PMC

Kang DW et al (2017) Microbiota transfer therapy alters gut ecosystem and improves gastrointestinal and autism symptoms: an open-label study. Microbiome 5:10. 10.1186/s40168-016-0225-7 PubMed PMC

Kelly CJ et al (2015) Crosstalk between microbiota-derived short-chain fatty acids and intestinal epithelial HIF augments tissue barrier function. Cell Host Microbe 17:662–671. 10.1016/j.chom.2015.03.005 PubMed PMC

Kelly JR et al (2016) Transferring the blues: depression-associated gut microbiota induces neurobehavioural changes in the rat. J Psychiatr Res 82:109–118. 10.1016/j.jpsychires.2016.07.019 PubMed

Kosikowska U, Biernasiuk A, Korona-Glowniak I, Kiciak S, Tomasiewicz K, Malm A (2016) The association of chronic hepatitis C with respiratory microbiota disturbance on the basis of decreased Haemophilus spp. colonization. Med Sci Monit 22:625–632 PubMed PMC

Kutchko KM, Siltberg-Liberles J (2013) Metazoan innovation: from aromatic amino acids to extracellular signaling. Amino Acids 45:359–367. 10.1007/s00726-013-1509-x PubMed PMC

Lamberts JT, Hildebrandt EN, Brundin P (2015) Spreading of alpha-synuclein in the face of axonal transport deficits in Parkinson’s disease: a speculative synthesis. Neurobiol Dis 77:276–283. 10.1016/j.nbd.2014.07.002 PubMed

Lang AS, Beatty JT (2000) Genetic analysis of a bacterial genetic exchange element: the gene transfer agent of Rhodobacter capsulatus. Proc Natl Acad Sci USA 97:859–864 PubMed PMC

Le W, Rowe D, Xie W, Ortiz I, He Y, Appel SH (2001) Microglial activation and dopaminergic cell injury: an in vitro model relevant to Parkinson’s disease. J Neurosci 21:8447–8455 PubMed PMC

Lebouvier T, Chaumette T, Paillusson S, Duyckaerts C, Bruley des Varannes S, Neunlist M, Derkinderen P (2009) The second brain and Parkinson’s disease. Eur J Neurosci 30:735–741. 10.1111/j.1460-9568.2009.06873.x PubMed

Li G, Young KD (2013) Indole production by the tryptophanase TnaA in Escherichia coli is determined by the amount of exogenous tryptophan. Microbiology 159:402–410. 10.1099/mic.0.064139-0 PubMed

Liu WH, Chuang HL, Huang YT, Wu CC, Chou GT, Wang S, Tsai YC (2016) Alteration of behavior and monoamine levels attributable to Lactobacillus plantarum PS128 in germ-free mice. Behav Brain Res 298:202–209. 10.1016/j.bbr.2015.10.046 PubMed

Lucas N, Hubain P, Loas G, Jurysta F (2017) Treatment resistant depression: actuality and perspectives in 2017. Rev Med Brux 38:16–25 PubMed

Macedo D, Filho A, Soares de Sousa CN, Quevedo J, Barichello T, Junior HVN, Freitas de Lucena D (2017) Antidepressants, antimicrobials or both? Gut microbiota dysbiosis in depression and possible implications of the antimicrobial effects of antidepressant drugs for antidepressant effectiveness. J Affect Disord 208:22–32. 10.1016/j.jad.2016.09.012 PubMed

Main BS, Minter MR (2017) Microbial immuno-communication in neurodegenerative diseases. Front Neurosci 11:151. 10.3389/fnins.2017.00151 PubMed PMC

Malkki H (2017) Parkinson disease: could gut microbiota influence severity of Parkinson disease? Nat Rev Neurol 13:66–67. 10.1038/nrneurol.2016.195 PubMed

Manoharan I et al (2016) Homeostatic PPARα signaling limits inflammatory responses to commensal microbiota in the intestine. J Immunol 196:4739–4749. 10.4049/jimmunol.1501489 PubMed PMC

Mariani J et al (2015) FOXG1-dependent dysregulation of GABA/glutamate neuron differentiation in autism. Spectr Disord Cell 162:375–390. 10.1016/j.cell.2015.06.034 PubMed PMC

Martin AM, Young RL, Leong L, Rogers GB, Spencer NJ, Jessup CF, Keating DJ (2017) The diverse metabolic roles of peripheral serotonin. Endocrinology 158:1049–1063. 10.1210/en.2016-1839 PubMed

Mawe GM, Hoffman JM (2013) Serotonin signalling in the gut—functions, dysfunctions and therapeutic targets. Nat Rev Gastroenterol Hepatol 10:473–486. 10.1038/nrgastro.2013.105 PubMed PMC

McWilliams TG, Muqit MM (2017) PINK1 and Parkin: emerging themes in mitochondrial homeostasis. Curr Opin Cell Biol 45:83–91. 10.1016/j.ceb.2017.03.013 PubMed

Mertsalmi TH, Aho VTE, Pereira PAB, Paulin L, Pekkonen E, Auvinen P, Scheperjans F (2017) More than constipation—bowel symptoms in Parkinson’s disease and their connection to gut microbiota. Eur J Neurol 24:1375–1383. 10.1111/ene.13398 PubMed

Mittal R et al (2017) Neurotransmitters: the critical modulators regulating gut-brain axis. J Cell Physiol 232:2359–2372. 10.1002/jcp.25518 PubMed PMC

Moonen AJH, Wijers A, Dujardin K, Leentjens AFG (2017) Neurobiological correlates of emotional processing in Parkinson’s disease: a systematic review of experimental studies. J Psychosom Res 100:65–76. 10.1016/j.jpsychores.2017.07.009 PubMed

Mulak A, Bonaz B (2015) Brain-gut-microbiota axis in Parkinson’s disease. World J Gastroenterol 21:10609–10620. 10.3748/wjg.v21.i37.10609 PubMed PMC

Noble EE, Hsu TM, Kanoski SE (2017) Gut to brain dysbiosis: mechanisms linking western diet consumption, the microbiome, and cognitive impairment. Front Behav Neurosci 11:9. 10.3389/fnbeh.2017.00009 PubMed PMC

Obata Y, Pachnis V (2016) The effect of microbiota and the immune system on the development and organization of the enteric nervous system. Gastroenterology 151:836–844. 10.1053/j.gastro.2016.07.044 PubMed PMC

O’Leary OF et al (2018) The vagus nerve modulates BDNF expression and neurogenesis in the hippocampus. Eur Neuropsychopharmacol 28:307–316. 10.1016/j.euroneuro.2017.12.004 PubMed

O’Mahony SM, Clarke G, Borre YE, Dinan TG, Cryan JF (2015) Serotonin, tryptophan metabolism and the brain-gut-microbiome axis. Behav Brain Res 277:32–48. 10.1016/j.bbr.2014.07.027 PubMed

Omenetti S, Pizarro TT (2015) The Treg/Th17 axis: a dynamic balance regulated by the gut microbiome. Front Immunol 6:639. 10.3389/fimmu.2015.00639 PubMed PMC

Özoğul F (2004) Production of biogenic amines by Morganella morganii, Klebsiella pneumoniae and Hafnia alvei using a rapid HPLC method. Eur Food Res Technol 219:465–469

Persico AM, Napolioni V (2013) Urinary p-cresol in autism spectrum disorder. Neurotoxicol Teratol 36:82–90. 10.1016/j.ntt.2012.09.002 PubMed

Petra AI, Panagiotidou S, Hatziagelaki E, Stewart JM, Conti P, Theoharides TC (2015) Gut-microbiota-brain axis and its effect on neuropsychiatric disorders with suspected immune dysregulation. Clin Ther 37:984–995. 10.1016/j.clinthera.2015.04.002 PubMed PMC

Ray A, Dittel BN (2015) Interrelatedness between dysbiosis in the gut microbiota due to immunodeficiency and disease penetrance of colitis. Immunology 146:359–368. 10.1111/imm.12511 PubMed PMC

Reigstad CS et al (2015) Gut microbes promote colonic serotonin production through an effect of short-chain fatty acids on enterochromaffin cells. FASEB J 29:1395–1403. 10.1096/fj.14-259598 PubMed PMC

Rietdijk CD, Perez-Pardo P, Garssen J, van Wezel RJ, Kraneveld AD (2017) Exploring Braak’s hypothesis of Parkinson’s disease. Front Neurol 8:37. 10.3389/fneur.2017.00037 PubMed PMC

Rivard L, Srinivasan J, Stone A, Ochoa S, Sternberg PW, Loer CM (2010) A comparison of experience-dependent locomotory behaviors and biogenic amine neurons in nematode relatives of Caenorhabditis elegans. BMC Neurosci 11:22 10.1186/1471-2202-11-22 PubMed PMC

Rolig AS et al (2017) The enteric nervous system promotes intestinal health by constraining microbiota composition. PLoS Biol 15:e2000689. 10.1371/journal.pbio.2000689 PubMed PMC

Roshchina VV (2010) Evolutionary considerations of neurotransmitters in microbial, plant, and animal cells. In: Lyte M, Freestone PPE (eds) Microbial endocrinology: interkingdom signaling in infectious disease and health, vol XVI. Springer, New York, pp 17–52

Salloum NC, Gott BM, Conway CR (2017) Sustained remission in patients with treatment-resistant depression receiving vagal nerve stimulation: a case series. Brain Stimul 10:997–1000. 10.1016/j.brs.2017.06.001 PubMed

Scheperjans F et al (2015) Gut microbiota are related to Parkinson’s disease and clinical phenotype. Mov Disord 30:350–358. 10.1002/mds.26069 PubMed

Shaw W (2016) Clostridia bacteria in the gastrointestinal tract as a major cause of depression and other neuropsychiatric disorders. In: Greenblatt J, Brogan K (eds) Integrative psychiatry for depression: redefining models for assessment, treatment, and prevention of mood disorders. Taylor and Francis, New York, pp 31–48

Sherwin E, Rea K, Dinan TG, Cryan JF (2016) A gut (microbiome) feeling about the brain. Curr Opin Gastroenterol 32:96–102. 10.1097/MOG.0000000000000244 PubMed

Shishov VA, Kirovskaia TA, Kudrin VS, Oleskin AV (2009) [Amine neuromediators, their precursors, and oxidation products in the culture of Escherichia coli K-12]. Prikl Biokhim Mikrobiol 45:550–554 PubMed

Singh SK, Pal A (2015) Biophysical approaches to the study of LeuT, a prokaryotic homolog of neurotransmitter sodium symporters. Methods Enzymol 557:167–198. 10.1016/bs.mie.2015.01.002 PubMed PMC

Smith MR, Fernandes J, Go YM, Jones DP (2017) Redox dynamics of manganese as a mitochondrial life-death switch. Biochem Biophys Res Commun 482:388–398. 10.1016/j.bbrc.2016.10.126 PubMed PMC

Snyder C, Kream RM, Ptacek R, Stefano GB (2015) Mitochondria, microbiome and their potential psychiatric modulation. Autism Open Access 5:144. 10.4172/2165-7890.1000144

Sonetti D, Ottaviani E, Bianchi F, Rodriquez M, Stefano ML, Scharrer B, Stefano GB (1994) Microglia in invertebrate ganglia. Proc Natl Acad Sci USA 91:9180–9184 PubMed PMC

Song Y, Liu C, Finegold SM (2004) Real-time PCR quantitation of clostridia in feces of autistic children. Appl Environ Microbiol 70:6459–6465. 10.1128/AEM.70.11.6459-6465.2004 PubMed PMC

Stefano GB (1986) Conformational matching: a possible evolutionary force in the evolvement of signal systems. In: Stefano GB (ed) CRC Handbook of comparative opioid and related neuropeptide mechanisms, vol 2. CRC Press Inc., Boca Raton, pp 271–277

Stefano GB, Kream RM (2007) Endogenous morphine synthetic pathway preceded and gave rise to catecholamine synthesis in evolution (review). Int J Mol Med 20:837–841 PubMed

Stefano GB, Kream RM (2010) Dopamine, morphine, and nitric oxide: an evolutionary signaling triad CNS. Neurosci Ther 16:e124–e137. 10.1111/j.1755-5949.2009.00114.x PubMed PMC

Stefano GB, Kream R (2015a) Psychiatric disorders involving mitochondrial processes. Psychol Obs 1:1–6

Stefano GB, Kream R (2015b) Evolutionary perspective on microglial/neuronal coupling with special relevance to psychiatric illnesses. J Psychiatr 18:329. 10.4172/2378-5756.1000329

Stefano GB, Kream RM (2016) Mitochondrial DNA heteroplasmy in human health and disease. Biomed Rep 4:259–262. 10.3892/br.2016.590 PubMed PMC

Stefano GB, Catapane EJ, Aiello E (1976) Dopaminergic agents: influence on serotonin in the molluscan nervous system. Science 194:539–541 PubMed

Stefano GB, Bilfinger TV, Fricchione GL (1994) The immune neuro-link and the macrophage: Postcardiotomy delirium. HIV-associated dementia psychiatry. Prog Neurobiol 42:475–488 PubMed

Stefano GB, Samuel J, Kream RM (2017) Antibiotics may trigger mitochondrial dysfunction inducing psychiatric disorders. Med Sci Monit 23:101–106 PubMed PMC

Thompson SM, Kallarackal AJ, Kvarta MD, Van Dyke AM, LeGates TA, Cai X (2015) An excitatory synapse hypothesis of depression. Trends Neurosci 38:279–294. 10.1016/j.tins.2015.03.003 PubMed PMC

Tobe EH (2013) Mitochondrial dysfunction, oxidative stress, and major depressive disorder. Neuropsychiatr Dis Treat 9:567–573. 10.2147/NDT.S44282 PubMed PMC

Tremlett H, Bauer KC, Appel-Cresswell S, Finlay BB, Waubant E (2017) The gut microbiome in human neurological disease: a review. Ann Neurol 81:369–382. 10.1002/ana.24901 PubMed

Tulstrup MV et al (2015) Antibiotic treatment affects intestinal permeability and gut microbial composition in Wistar rats dependent on antibiotic class. PLoS One 10:e0144854. 10.1371/journal.pone.0144854 PubMed PMC

Unger MM et al (2016) Short chain fatty acids and gut microbiota differ between patients with Parkinson’s disease and age-matched controls. Parkinsonism Relat Disord 32:66–72. 10.1016/j.parkreldis.2016.08.019 PubMed

Verheijden S, De Schepper S, Boeckxstaens GE (2015) Neuron-macrophage crosstalk in the intestine: a “microglia” perspective. Front Cell Neurosci 9:403. 10.3389/fncel.2015.00403 PubMed PMC

Vermeiren Y, De Deyn PP (2017) Targeting the norepinephrinergic system in Parkinson’s disease and related disorders: the locus coeruleus story. Neurochem Int 102:22–32. 10.1016/j.neuint.2016.11.009 PubMed

Villaran RF et al (2010) Ulcerative colitis exacerbates lipopolysaccharide-induced damage to the nigral dopaminergic system: potential risk factor in Parkinson’s disease. J Neurochem 114:1687–1700. 10.1111/j.1471-4159.2010.06879.x PubMed

Wallace CJ, Milev R (2017a) The effects of probiotics on depressive symptoms in humans: a systematic review. Ann Gen Psychiatr 16:14. 10.1186/s12991-017-0138-2 PubMed PMC

Wallace CJ, Milev R (2017b) Erratum to: the effects of probiotics on depressive symptoms in humans: a systematic review. Ann Gen Psychiatr 16:18. 10.1186/s12991-017-0141-7 PubMed PMC

Wells JM et al (2017) Homeostasis of the gut barrier and potential biomarkers. Am J Physiol Gastrointest Liver Physiol 312:G171–G193. 10.1152/ajpgi.00048.2015 PubMed PMC

Winklhofer KF, Haass C (2010) Mitochondrial dysfunction in Parkinson’s disease. Biochim Biophys Acta 1802:29–44. 10.1016/j.bbadis.2009.08.013 PubMed

Wu GD et al (2011) Linking long-term dietary patterns with gut microbial enterotypes. Science 334:105–108. 10.1126/science.1208344 PubMed PMC

Wu GD, Bushmanc FD, Lewis JD (2013) Diet, the human gut microbiota and IBD. Anaerobe 24:117–120. 10.1016/j.anaerobe.2013.03.011 PubMed

Yakunina N, Kim SS, Nam EC (2017) Optimization of transcutaneous vagus nerve stimulation using functional MRI. Neuromodulation 20:290–300. 10.1111/ner.12541 PubMed

Yamashita A, Singh SK, Kawate T, Jin Y, Gouaux E (2005) Crystal structure of a bacterial homologue of Na+/Cl− dependent neurotransmitter transporters. Nature 437:215–223. 10.1038/nature03978 PubMed

Yano JM et al (2015) Indigenous bacteria from the gut microbiota regulate host serotonin biosynthesis. Cell 161:264–276. 10.1016/j.cell.2015.02.047 PubMed PMC

Yoo BB, Mazmanian SK (2017) The enteric network: interactions between the immune and nervous systems of the Gut. Immunity 46:910–926. 10.1016/j.immuni.2017.05.011 PubMed PMC

Zheng P et al (2016) Gut microbiome remodeling induces depressive-like behaviors through a pathway mediated by the host’s metabolism. Mol Psychiatr 21:786–796. 10.1038/mp.2016.44 PubMed

Zhou L, Foster JA (2015) Psychobiotics and the gut-brain axis: in the pursuit of happiness. Neuropsychiatr Dis Treat 11:715–723. 10.2147/NDT.S61997 PubMed PMC

HIV, HSV, SARS-CoV-2 and Ebola Share Long-Term Neuropsychiatric Sequelae

Mitochondrial DNA Heteroplasmy as an Informational Reservoir Dynamically Linked to Metabolic and Immunological Processes Associated with COVID-19 Neurological Disorders

SARS-CoV-2, Trait Anxiety, and the Microbiome

Interoception, Trait Anxiety, and the Gut Microbiome: A Cognitive and Physiological Model

Endocrine disruptors and gut microbiome interactions

Behaviorally-Mediated Entrainment of Whole-Body Metabolic Processes: Conservation and Evolutionary Development of Mitochondrial Respiratory Complexes

Chromosomal Processes in Mind-Body Medicine: Chronic Stress, Cell Aging, and Telomere Length