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Copyright ©The Author(s) 2015.
World J Gastroenterol. Nov 7, 2015; 21(41): 11597-11608
Published online Nov 7, 2015. doi: 10.3748/wjg.v21.i41.11597
Table 1 Metabolite, gut microbiota, and potential biologic functions
MetabolitesRelated bacteriaPotential biological functionsRef.
Short-chain fatty acidsClostridial clusters IV and XIVa of Firmicutes, including species of Eubacterium, Roseburia, Faecalibacterium, and CoprococcusDecreased colonic pH, inhibit the growth of pathogens; stimulate water and sodium absorption; participate in cholesterol synthesis; provide energy to the colonic epithelial cells; GI hormones secretion via enteroendocrine cells, implicated in human obesity, insulin resistance and type 2 diabetes, colorectal cancer. Immunological homeostasis in the gut[14-18]
Bile acidsLactobacillus, Bifidobacteria, Enterobacter, Bacteroides, ClostridiumAbsorb dietary fats and lipid-soluble vitamins, facilitate lipid absorption, maintain intestinal barrier function, signal systemic endocrine functions to regulate triglycerides, cholesterol, glucose and energy homeostasis[19-21]
Choline metabolitesFaecalibacterium prausnitzii, BifidobacteriumModulate lipid metabolism and glucose homeostasis. Involved in nonalcoholic fatty liver disease, dietary induced obesity, diabetes, and cardiovascular disease[22,23]
Phenolic, benzoyl, and phenyl derivativesClostridium difficile, F. prausnitzii, Bifidobacterium, Subdoligranulum, LactobacillusDetoxification of xenobiotics; indicate gut microbial composition and activity; utilize polyphenols. Urinary hippuric acid may be a biomarker of hypertension and obesity in humans. Urinary 4-hydroxyphenylacetate, 4-cresol, and phenylacetate are elevated in colorectal cancer. Urinary 4-cresyl sulfate is elevated in children with severe autism[24,25]
Indole derivativesClostridium sporogenes, E. coliProtect against stress-induced lesions in the GI tract; modulate expression of proinflammatory genes, increase expression of anti-inflammatory genes, strengthen epithelial cell barrier properties. Implicated in GI pathologies, brain-gut axis, and a few neurological conditions[26-28]
VitaminsBifidobacteriumProvide complementary endogenous sources of vitamins, strengthen immune function, exert epigenetic effects to regulate cell proliferation[29,30]
PolyaminesCampylobacter jejuni, Clostridium saccharolyticumExert genotoxic effects on the host, anti-inflammatory and antitumoral effects. Potential tumor markers[31,32]
LipidsBifidobacterium, Roseburia, Lactobacillus, Klebsiella, Enterobacter, Citrobacter, ClostridiumImpact intestinal permeability, activate intestine-brain-liver neural axis to regulate glucose homeostasis; LPS induces chronic systemic inflammation; conjugated fatty acids improve hyperinsulinemia, enhance the immune system and alter lipoprotein profiles. Cholesterol is the basis for sterol and bile acid production[33,34]
Neurotransmitters and neuroactive compounds:serotonin, tryptophan, kynurenine. dopamine, noradrenaline, GABALactobacillus ,Bifidobacterium, Escherichia, Bacillus, Saccharomyces, Candida, Streptococcus, EnterococcusNeurofunction related as mood, emotion, cognition, reward (CNS), motility/secretion and behavior[35-39]
HPA hormones: cortisolLactobacillus, BifidobacteriumIndirect regulation of HPA. Regulation of stress response, host metabolism, anti-inflammation, wound healing, endocrine abnormalities prominent in stress related psychiatric disorders[40]
Table 2 Effects of the probiotics intervention on gut microbiota composition and its clinical and/or biochemical consequences
Type of studyCategory of patients/duration of treatmentProbioticsClinical outcomeRef.
RCT36 cirrhotics/6 moLactobacillus.acidophilus, Lactobacillus bulgaricus, Bifidobacterium lactis and S. thermophilesBlood ammonia levels[88]
RCT65 cirrhotics/6 moLactobacilliIncidence of HE, hospital admission, plasma-ammonia level, serum bilirubin level[83]
R50 cirrhotics/14 dBifidobacterium, L. acidophilus and Enterococcus vs Bacillus subtilis and Enterococcus faeciumBifidobacterium count, fecal pH, fecal and blood ammonia in both groups, endotoxin level only with B. subtilis and E. faecium[89]
RCT17 cirrhotics with HVPG > 10 mmHg/2 moVSL # 3®Plasma aldosterone[81]
RCT41 chronic liver disease/14 dBifidobacterium bifidus, L. acidophilus, Lactobacillus bulgaricus, and S. thermophilusE. coli count, intestinal flora imbalance, improvement in debilitation, food intake, abdominal distension, and ascitic fluid[90]
RCT66 cirrhotics underwent liver transplantation/2 wk after the operationPediacoccus pentosaceus, Leuconostoc mesenteroides, Lactobacillus paracasei and Lactobacillus plantarumInfectious complication[78]
RCT39 cirrhotics/42 dE. coli NissleEndotoxemia, Child-Pugh score, Restoration of normal colonic colonization[91]
RCT63 cirrhotics patients with large oesophageal varices without history of variceal bleeding/2 moPropranolol plus VSL # 3®HVPG, plasma TNF-α levels.[92]
RCT25 nonalcoholic minimal HE cirrhotics (defined by a standard psychometric battery)/60 dYogurt contained L. bulgaricus and S. thermophilusMinimal HE[93]
RCT61 cirrhotics underwent hepatic surgery/2 wk before and after surgeryLactobacillus casei strain Shirota, Bifidobacterium breve strain Yakult, and galactooligosaccharidesIntestinal integrity, infectious complication[79]
RCT63 cirrhotics underwent liver transplantation/12 d after the operationL. plantarum 299 and oat fiberInfectious complication[77]
RCT50 cirrhotics underwent living donor liver transplantation/2 d and 2 wk before and after the operation, respectivelyL. casei strain Shirota, B. breve strain Yakult, and galactooligosaccharidesInfectious complication[94]
RCT30 cirrhotics with minimal HE/4 wkLactobacillus GGEndotoxemia, gut dysbiosis, gut microbiome-metabolome linkages[69]
RCT138 cirrhotics/3 moVSL # 3®HE, small intestinal bacterial overgrowth[84]