Gut-liver axis and probiotics: Their role in non-alcoholic fatty liver disease

Table 1 Intestinal microbiota composition in obese individuals

Ref.	Subjects	Method	Firmicutes	Bacteroidetes	Actinobacteria	Proteobacteria	Archaea
Turnbaugh et al[30]	12 ob/2 nw	16 S RNA pyrosequencing 454	+	-	/	/	/
Turnbaugh et al[31]	31 MZ twin pairs/23 DZ twin pairs/46 mo	16 S RNA pyrosequencing 454	==	--	++	==	==
Mouzaki et al[32]	17 nw/11 ss/22 NASH	qPCR	++	--	No statistical difference	No statistical difference	/
Armougom et al[33]	20 ob/20 nw	qPCR	++	--	/	/	+
Million et al[34]	68 ob/47 nw	qPCR; cell counts	++	==	-	/
Nadal et al[35]	39 ob adolescents low calorie 10 wk	FISH	++	--	++	++	++
Santacruz et al[36]	36 ob adolescents low calorie 10 wk	RT-PCR	++	--	++	/	/
Zhang et al[37]	3 ob/3 nw	qPCR + 16 S RNA pyrosequencing 454	+-(Lachnospiraceae)	+(Prevotellaceae)	+(Coriobacteriaceae)	+	+(Methanobrevibacter smithii)
Wong et al[38]	16 ob NASH/22 nw ctrls	16 S RNA pyrosequencing 454	--	++	--	++	/
Zhu et al[39]	16 nw/25 I/22 NASH	16 S RNA pyrosequencing 454	--	++	--	++	/
Schwiertz et al[40]	33 ob/35 ow/30 nw	qPCR	--	==	-	/	-

Firmicutes: Clostridia, Lactobacillales, Coccacea; ob: Obese; nw: Normal weight; ss: Simple steatosis; ow: Overweight; MZ: Monozygotic; DZ: Dizygotic.

Table 2 Studies with probiotics in animal models of non-alcoholic fatty liver disease

Ref.	Animal model	Probiotic	Weeks	Positive effects	Negative effects
Li et al[63]	HFD ob/ob mice	VSL#3	4	Reduced liver inflammation and serum ALT
Esposito et al[64]	HFD Sprague-Dawley rats	VSL#3	4	Significantly reduced TNF alpha levels, MMP-2 and MMP-9 activities, iNOS, and Cox-2 expression. Increased PPAR-alpha expression	NS
Ma et al[65]	HFD-WT male C57BL6	VSL#3	4	Improved NKT cells depletion, insulin resistance, and hepatic steatosis	NS
Velayudham et al[66]	MCD mouse	VSL#3	10	Prevented PPAR-induced fibrosis. Increased expression of Bambi, a negative regulator of the TGFβ signaling pathway	Did not prevent NASH.
					Did not protect against MCD liver injury
Mencarelli et al[67]	Apo E-/- mice fed dextran sulfate sodium	VSL#3	12	Reversed IR and prevented steatohepatitis by transactivation of PPARγ	NS
Bhathena et al[68]	MCD Bio F1B Golden Syrian hamster	Lactobacillus fermentum ATCC	12	Reduced liver fat deposition, decreased total cholesterol, triglycerides, uric acid, and insulin resistance	NS
Wagnerberger et al[69]	High fructose intake C57BL/6 L mouse	Lactobacillus Casei-Shirota	8	Attenuated the TLR4 signaling pathway and increased PPAR activity
Karahan et al[70]	MCD Wistar rats	Pro1; Pro2	2 and 8	Both probiotics reduced ≥ 50% the incidence of steatohepatitis by modulating apoptosis + anti-inflammatory activity	NS
Yalçin et al[71]	Broilers fed low-protein diet	Primalac 454	4	Significantly diminished histological grade, steatosis and cell ballooning scores	Increased serum TG
Xu et al[72]	HFD Sprague-Dawley rats	Lactobacillus acidophilus Bifidobacterium longum	12	Bifidobacterium longum was superior to Lactobacillus acidophilus in attenuating liver fat accumulation. No variation of intestinal permeability in the treated groups
Nardone et al[74]	Ischemia/reperfusion (I/R) in rats fed a standard or MCD diet	Lactobacillus Paracasei	8	Reduced LPS levels. Attenuated I/R-related damage	NS
Fazeli et al[75]	Rats on high cholesterol diet	Lactobacillus plantarum A7	2	Significantly reduced levels of cholesterol, TG and LDL	NS
Endo et al[77]	Male Fischer CDAA rats	Butyrate producing Clostridium butyricum MIYAIRI 588	8, 16, 50	Delayed CDAA-induced NAFLD progression and liver tumorigenesis. Reduced lipid deposition and improved IR, serum endotoxin levels, and hepatic inflammatory indexes. Improved ZO-1 expression	NS
Chiua et al[78]	HepG2 cells exposed to LPS	Lactobacilli bacteria lisate		Suppressed cytokine signaling 1 and PPAR alpha via NOD-NF-κB and cross-regulation of TLR4	NS
Raso et al[76]	Rats on a HFD	Synbiotic with Lactobacillus paracasei B21060	6	Improved IR parametersReduced cytokine synthesis and restored the HFD-dysregulated TLR 2, 4 and 9 mRNAs.Preserved gut barrier integrity	NS

Primalac 454: Lactobacillus acidophilus, Lactobacillus casei, Enterococcus faecium, and Bifidobacterium thermophilus; VSL#3: Streptococcus thermophilus, Bifidobacterium breve, Bifidobacterium longum, Bifidobacterium infantis, Lactobacillus acidophilus, Lactobacillus plantarum, Lactobacillus paracasei, and Lactobacillus delbrueckii subsp. bulgaricus; Pro1: Lactobacillus fermentum, Lactobacillus plantarum, and Enterococcus faecium; Pro2: Enterococcus faecium and Lactobacillus Pl; ALT: Alanine aminotransferase; AST: Aspartate aminotransferase; TNF: Tumor necrosis factor; IL: Interleukin; IR: Insulin resistance; PPAR: Peroxisome proliferator-activated receptors; MMP: Matrix metalloproteinase; NOS: Nitric oxide synthase; NOD: Nucleotide-binding oligomerization domain receptors; TLR: Toll-like receptors; CDAA: Choline-deficient, L-amino acid-defined; MCD: Methionine-choline deficient.

Table 3 Studies with probiotics in human non-alcoholic fatty liver disease

Ref.	Probiotic(s)	Study design	Month	Main results	ALT or AST	GGT	US/MRI/LH
Wong et al[87]	Lepicol: 10 g/d10 adult NASH ctrls10 adult NASH patients	RCT	6	Significantly reduced ASTChanged intrahepatic triglyceride content (IHTG)	Pr vs plac: ALT NS decrease AST: -13 ± 31 vs 23 ± 32, P = 0.021	NR	Reduced IHTG at SMR (P = 0.034)
Vajro et al[73]	Lactobacillus GG: 12 billion CFU/d 10 pediatric obese ctrls 10 pediatric obese patients	RCT	2	Significantly reduced aminotransferases and anti-peptidoglycan-polysaccharide Abs. TNF-α stable	Pr vs plac: Decreased ALT 70.3 ± 34.76 vs 40.1 ± 22.37, P = 0.03	Normal	Unchanged
Loguercio et al[81]	Bio-Flora: 4 tablets/d 10 adult NASH patients	Open label	2	Decreased ALT and GGT	Decreased ALT -64.5% ± 26.5%, P < 0.01	-55 ± 31, P < 0.01	NR
Loguercio et al[82]	VSL#3: 450 billion/d 22 patients	Open label	NR	Significantly improved plasma MDA and 4-HNE (data not shown)	NR	NR	NR
Solga et al[84]	VSL#3: 450 billion/d 4 adult NAFLD patients	Open label	4	Significantly increased ultrasound liver fat NS different glycosylated Hb; TNF-α, IL-6	Unchanged	NR	Increased liver fat at MRS
Aller et al[85]	Lactobacillus bulgaricus streptoc.	RCT	3	Significantly reduced aminotransferases	Decreased in Pr:ALT: 67.7 ± 25.1 vs 60.4 ± 30.4, P < 0.05AST: 41.3 ± 15.5 UI/L vs 35.6 ± 10.4 UI/L, P < 0.05	118 ± 63 vs 107 ± 60 (P < 0.05)	NR
	Thermophiles: 500 million CFU/d
	14 adult NAFLD ctrls
	14 adult NAFLD patients
Malaguarnera et al[86]	Bifidobacterium longum and Fos: 2.5 g/d + vit B1, B2 , B6, B12 + life style 34 adult NASH ctrls 32 adult NASH patients	RCT	4	Improved fibrosis scores in 70% of patients. Reduced HOMA-IR, LDL cholesterol , CRP, TNF-α, AST	Pr vs plac: ALT NS decrease AST -69.6 vs -45.9, P = 0.05	NR	Decreased US bright liver -42% vs -11%, P < 0.001
Shavakhi et al[91]	Proxetin: 2 tablets/d	RCT	6	Significantly reduced ALT in Metformin/	Pr vs plac:ALT Decrease45.2 ± 32.5 vs 112.5 ± 69,P < 0.001	NR	Reduced US grade in M/Pr, P < 0.01
	Metformin: 500 mg/d			Probiotic (M/Pr) vs M/
	36 adult NASH ctrls			placebo (M/Plac)
	34 adult NASH patients			M reduced BMI enhanced by Pr
Eslamparast et al[89]	Proxetin 2 tablets/d26 adult NASH ctrls26 adult NASH patients	RCT	6	Significantly and persistently reduced ALT Significantly reduced AST, HOMA-IR, GGT, CRP, TNF-α, and NF-κB p65	Pr vs placDecreased ALT (wk) 28 -25.1 vs -7.3, P < 0.001	Reduced Pr vs plac-15.8 vs -5.21, P < 0.01	Significant improvement elastography and fibrosis score
Alisi et al[90]	VSL#3	RCT	4	Significantly increased GLP-1 and aGLP-1 Sign. decreased BMI	Pr vs plac ALT unchanged	NR	Significantly improved ultrasound fatty liver score

Proxetin: Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus rhamnosus, Lactobacillus bulgaricus, Bifidobacterium breve, Bifidobacterium longum, Streptococcus thermophilus + FOS 350 mg; Lepicol: Lactobacillus plantarum, Lactobacillus delbrueckii, Lactobacillus acidophilus, Lactobacillus rhamnosus, and Bifidobacterium bifidum (Each sachet contains 10 g of probiotic cultures) + FOS; VSL#3: Streptococcus thermophilus, Bifidobacterium breve, Bifidobacterium longum, Bifidobacterium infantis, Lactobacillus acidophilus, Lactobacillus plantarum, Lactobacillus paracasei, Lactobacillus delbrueckii subsp. bulgaricus; BioFlora: Lactobacilli (acidophilus; lactis; casei; brevis; salivarum; rhamnosus; plantarum; bulgaricus), iron, vitamin C, B6, D3, B2, B12, folic acid and zinc oxide, + FOS; FOS: Fructooligosaccharides; ALT: Alanine aminotransferase; AST: Aspartate aminotransferase; GGT: Gamma-glutamyl transpeptidase; MRI: Magnetic resonance imaging; LH: Liver histology; BMI: Body mass index; NR: Not reported; Pl: Placebo; Pr: Probiotic; NS: Not significant; Sign: Significantly; TNF: Tumor necrosis factor; IL: Interleukin.