Gut Microbiome and Depression Flashcards
What is the gut microbiome?
numerically the human body carries as many bacterial cells as it does human
the vast majority are commensal and inhabit the gastrointestinal tract
the microbiome is increasingly recognized for it’s contributions to health and numerous diverse diseases
microbiome contents are considered comparable to epigenetics
microbiome is heritable - first colonization from parents and influenced by family and early environment
microbiome is plastic to life experiences, genetics, diet, exercise, age, geography, and stress
What are the bacterial influences of the microbiome?
bacteria are long recognized to contribute extensively to gut metabolism, especially carbohydrate metabolism
gut microbiome also contributes to immune system development
microbiota also affect CNS function and behavior through a number of bidirectional pathways
collectively known as the gut-brain axis
autonomic afferent/efferent
peripheral immune functions
HPA (stress) functions
bacterial metabolites: short-chain fatty acids (SCFA), biogenic amines, trace nutrients (e.g. selenium)
What are germ-free animal studies?
germ-free (GF) mice are raised and housed in aseptic conditions: lack commensal microbiota in the GI, deficient immune development
observation in GF mice first highlighted the connection between gut microbiome and mood/behavior
GF mice have exaggerates HPA response to stress
stress response are normalized following colonization or transplant from conventional mice
What is microbiome plasticity to stress?
developmental stress model show corresponding changes in microbiome
maternal separation of rats causes persistent changes in gut microbiota
microbiome changes correlate with development of exaggerated stress response
stress response are normalized by probiotic treatment
What is the human clinical evidence for microbiome plasticity to stress?
significant co-morbidity of depression in metabolic/gastrointestinal disorders: diabetes, obesity, IBS, Crohn’s, etc.
consistent evidence of increased gut permeability in GI disorders: e.g., obese individuals have significantly elevated levels of circulating LPS
relationship of diet and exercise to mood disorders
How do diet and exercise influence the plasticity of the gut microbiome?
numerous observational studies have identified associations between diet and risk of MDD
recent studies show early life sensitivity
physical inactivity increases risk of depression
What are the therapeutic options for treating depression through the gut microbiome?
current therapeutic options being explored to modify the gut-brain axis include: probiotics, dietary interventions (esp. childhood interventions), fecal microbiota transplant
present trials are typically limited to individuals with GI disorders: irritable bowel syndrome, Crohn’s disease, obesity
psychological outcomes are being readily incorporated into trial protocols
