Role in disease Gut flora

1 role in disease

1.1 ulcers
1.2 inflammatory bowel diseases
1.3 irritable bowel syndrome
1.4 other inflammatory or autoimmune conditions
1.5 obesity , metabolic syndrome
1.6 liver disease
1.7 systemic infections
1.8 cancer
1.9 neuropsychiatric

role in disease

bacteria in digestive tract can contribute , affected disease in various ways. presence or overabundance of kinds of bacteria may contribute inflammatory disorders such inflammatory bowel disease. additionally, metabolites members of gut flora may influence host signaling pathways, contributing disorders such obesity , colon cancer. alternatively, in event of breakdown of gut epithelium, intrusion of gut flora components other host compartments can lead sepsis.

ulcers

helicobacter pylori can cause stomach ulcers crossing epithelial lining of stomach. here body produces immune response. during response parietal cells stimulated , release hydrochloric acid (hcl) stomach. however, response not stimulate mucus-secreting cells protect , line epithelium of stomach. acid sears holes epithelial lining of stomach, resulting in stomach ulcers.

inflammatory bowel diseases

the 2 main types of inflammatory bowel diseases, crohn s disease , ulcerative colitis, chronic inflammatory disorders of gut; causes of these disease unknown , issues gut flora , relationship host have been implicated in these conditions. additionally, appears interactions of gut flora gut-brain axis have role in ibd, physiological stress mediated through hypothalamic–pituitary–adrenal axis driving changes intestinal epithelium , gut flora in turn releasing factors , metabolites trigger signaling in enteric nervous system , vagus nerve.

the diversity of gut flora appears diminished in people inflammatory bowel diseases compared healthy people; additionally, in people ulcerative colitis, proteobacteria , actinobacteria appear dominate; in people crohn s, enterococcus faecium , several proteobacteria appear over-represented.

there reasonable evidence correcting gut flora imbalances taking probiotics lactobacilli , bifidobacteria can reduce visceral pain , gut inflammation in ibd.

irritable bowel syndrome

irritable bowel syndrome result of stress , chronic activation of hpa axis; symptoms include abdominal pain, changes in bowel movements, , increase in proinflammatory cytokines. overall, studies have found luminal , mucosal microbiota changed in irritable bowel syndrome individuals, , these changes can relate type of irritation such diarrhea or constipation. also, there decrease in diversity of microbiome low levels of fecal lactobacilli , bifidobacteria, high levels of facultative anaerobic bacteria such escherichia coli, , increased ratios of firmicutes:bacteroidetes.

other inflammatory or autoimmune conditions

allergy, asthma, , diabetes mellitus autoimmune , inflammatory disorders of unknown cause, have been linked imbalances in gut flora , relationship host.

with asthma, 2 hypotheses have been posed explain rising prevalence in developed world. hygiene hypothesis posits children in developed world not exposed enough microbes , may contain lower prevalence of specific bacterial taxa play protective roles. second hypothesis focuses on western pattern diet, lacks whole grains , fiber , has overabundance of simple sugars. both hypotheses converge on role of short-chain fatty acids (scfas) in immunomodulation. these bacterial fermentation metabolites involved in immune signalling prevents triggering of asthma , lower scfa levels associated disease. lacking protective genera such lachnospira, veillonella, rothia , faecalibacterium has been linked reduced scfa levels. further, scfas product of bacterial fermentation of fiber, low in western pattern diet. scfas offer link between gut flora , immune disorders, , of 2016, active area of research. similar hypotheses have been posited rise of food , other allergies.

the connection between gut microbiota , diabetes mellitus type 1 has been linked anti-inflammatory scfas, such butyrate, regulating associated low-grade inflammatory state controlling gut permeability. additionally, butyrate has been shown decrease insulin resistance, suggesting gut communities low in butyrate-producing microbes may increase chances of acquiring diabetes mellitus type 2.

as of 2016 not clear if changes gut flora cause these auto-immune , inflammatory disorders or product of or adaptation them.

obesity , metabolic syndrome

the gut flora has been implicated in obesity , metabolic syndrome due key role plays in digestive process; western pattern diet appears drive , maintain changes in gut flora in turn change how energy derived food , how energy used. 1 aspect of healthy diet lacking in western-pattern diet fiber , other complex carbohydrates healthy gut flora require flourish; changes gut flora in response western-pattern diet appear increase amount of energy generated gut flora may contribute obesity , metabolic syndrome. there evidence microbiota influence eating behaviors based on preferences of microbiota, can lead host consuming more food resulting in obesity. has been observed higher gut microbiome diversity, microbiota spend energy , resources on competing other microbiota , less on manipulating host. opposite seen lower gut microbiome diversity, , these microbiotas may work create host food cravings.

additionally, liver plays dominant role in blood glucose homeostasis maintaining balance between uptake , storage of glucose through metabolic pathways of glycogenesis , gluconeogenesis. in recent studies, illustrated intestinal lipids regulate glucose homeostasis involving gut-brain-liver axis. direct administration of lipids upper intestine increases long chain fatty acyl-coenzyme (lcfa-coa) levels in upper intestines , suppresses glucose production under sub diaphragmatic vagotomy or gut vagal deafferentation. interrupts neural connection between brain , gut , blocks upper intestinal lipids’ ability inhibit glucose production. gut-brain-liver axis , gut microbiota composition can regulate glucose homeostasis in liver , provide potential therapeutic methods treat obesity , diabetes.

just gut flora can function in feedback loop can drive development of obesity, there evidence restricting intake of calories (i.e., dieting) can drive changes composition of gut flora.

liver disease

as liver fed directly portal vein, whatever crosses intestinal epithelium , intestinal mucosal barrier enters liver, cytokines generated there. dysbiosis in gut flora has been linked development of cirrhosis , non-alcoholic fatty liver disease.

systemic infections

normally-commensal bacteria can harmful host if outside of intestinal tract. translocation, occurs when bacteria leave gut through mucosal lining, border between lumen of gut , inside of body, can occur in number of different diseases, , can caused growth of bacteria in small intestine, reduced immunity of host, or increased gut lining permeability.

if gut perforated, bacteria can invade body, causing potentially fatal infection. aerobic bacteria can make infection worse using available oxygen , creating environment favorable anaerobes.

cancer

some genera of bacteria, such bacteroides , clostridium, have been associated increase in tumor growth rate, while other genera, such lactobacillus , bifidobacteria, known prevent tumor formation.

neuropsychiatric

interest in relationship between gut flora , neuropsychiatric issues sparked 2004 study showing germ-free mice showed exaggerated hpa axis response stress compared non-gf laboratory mice. of january 2016, of work has been done on role of gut flora in gut-brain axis had been conducted in animals, or characterizing various neuroactive compounds gut flora can produce, , studies humans measuring differences between people various psychiatric , neurological differences, or changes gut flora in response stress, or measuring effects of various probiotics (dubbed psychobiotics in context), had been small , not generalized; whether changes gut flora result of disease, cause of disease, or both in number of possible feedback loops in gut-brain axis, remained unclear.

a systematic review 2016 examined preclinical , small human trials have been conducted commercially available strains of probiotic bacteria , found among tested, bifidobacterium , lactobacillus genera (b. longum, b. breve, b. infantis, l. helveticus, l. rhamnosus, l. plantarum, , l. casei), had potential useful central nervous system disorders.