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Allicin Modifies the Composition and Function of the Gut Microbiota in Alcoholic Hepatic Steatosis Mice
Abstract
The intestinal microbiome plays an important role in the pathogenesis of liver diseases. Alcohol intake induces gut microbiota dysbiosis and alters its function. This study investigated the antibiotic effect of allicin in mice with hepatic steatosis. Male C57BL/6 mice were administered an ethanol diet supplemented with allicin (5 and 20 mg/kg bw/day) for 4 weeks. Allicin modified the gut microbiota composition. Cecal microbiota exhibited a positive correlation with alcohol and hepatic triacylglycerol, but were suppressed with allicin. Ethanol diet with 5 mg allicin induced a lower intestinal permeability compared to ethanol diet alone. Allicin mediated the LPS-CD14-TLR4-induced hepatic inflammation pathway by reducing LPS, CD14, TLR4, and pro-inflammatory cytokines—TNF-ɑ, IL-1β, and IL-6. However, hepatic inflammation primarily resulted from alcohol toxicity rather than LPS production in the gut. The prediction of functional profiles from metagenomic 16S rRNA data revealed different functional profiles in each group. The predicted aldehyde dehydrogenase tended to increase in alcoholic mice administered allicin. The predicted LPS-related pathway and LPS biosynthesis protein results exhibited a similar trend as plasma LPS levels. Thus, alcohol and allicin intake shapes the gut microbiota and its functional profile and improves the CD14-TLR4 pathway to alleviate inflammation in the liver.
... Allicin exhibits various antimicrobial activities in both in vitro and in vivo studies [35][36][37] . Recently, allicin was reported to exhibit a modulatory effect on the gut microbiota and reduced hepatic steatosis 38,39 . Additionally, our previous pilot study showed that allicin supplementation shaped the gut microbiota composition and reduced TMAO production by the gut microbiota in mice subject to moderate carnitine consumption (0.02% ʟ-carnitine) 40 . ...
... The TMAO-reducing effect of allicin is probably based on its broad-spectrum antimicrobial activities 35 . Additionally, previous studies reported that garlic and its bioactive compounds exhibited lipid-lowering and fatty liver-protective effects via gut microbiota modulation 39,44 . Following allicin intake, it can be metabolized to various sulfur-containing bioactive compounds such as diallyl sulfide, diallyl disulfide, and diallyl trisulfide for modulating the microbiome composition in the gut [45][46][47][48] . ...
... Information on the resources is provided in Supplementary Table 2. Allicin synthesis, purification, and identification were based on our laboratory protocol 39,40,55 . The purity of allicin was >97%; it was dissolved in 0.5% carboxymethyl cellulose (CMC) and stored at −80°C before administration to the mice. ...
Cardiovascular disease (CVD) is strongly associated with the gut microbiota and its metabolites, including trimethylamine- N -oxide (TMAO), formed from metaorganismal metabolism of ʟ-carnitine. Raw garlic juice, with allicin as its primary compound, exhibits considerable effects on the gut microbiota. This study validated the benefits of raw garlic juice against CVD risk via modulation of the gut microbiota and its metabolites. Allicin supplementation significantly decreased serum TMAO in ʟ-carnitine-fed C57BL/6 J mice, reduced aortic lesions, and altered the fecal microbiota in carnitine-induced, atherosclerosis-prone, apolipoprotein E-deficient (ApoE −/− ) mice. In human subjects exhibiting high-TMAO production, raw garlic juice intake for a week reduced TMAO formation, improved gut microbial diversity, and increased the relative abundances of beneficial bacteria. In in vitro and ex vivo studies, raw garlic juice and allicin inhibited γ-butyrobetaine (γBB) and trimethylamine production by the gut microbiota. Thus, raw garlic juice and allicin can potentially prevent cardiovascular disease by decreasing TMAO production via gut microbiota modulation.
... 31,32,33 Recently, allicin was reported to exhibit a modulatory effect on the gut microbiota and reduced hepatic steatosis. 34,35 Additionally, our previous pilot study showed that allicin supplementation shaped the gut microbiota composition and reduced TMAO production by the gut microbiota in mice subjected to moderate carnitine consumption (0.02 %carnitine). 36 However, the role of raw garlic with allicin in improving cardiovascular phenotypes via gut microbiota modulation has not been fully elucidated. ...
... 31 Additionally, previous studies reported that garlic and its bioactive compounds exhibited lipid-lowering and fatty liver-protective effects via gut microbiota modulation. 35,40 Following allicin intake, it can be metabolized to various sulfur-containing bioactive compounds, such as diallyl sul de, diallyl disul de, and diallyl trisul de for modulating the microbiome composition in the gut. 41,42,43,44 Previously, in a human study, we developed the OCCT, which can robustly distinguish the low-and high-TMAO producers. ...
... Allicin synthesis, puri cation, and identi cation were based on our laboratory protocol. 35,36,48 The purity of allicin was more than 97 %; it was dissolved in 0.5 % carboxymethyl cellulose (CMC) and stored at −80°C before administration to the mice. ...
Cardiovascular disease (CVD) is strongly associated with the gut microbiota and its metabolites, including trimethylamine- N -oxide (TMAO) formed from ʟ-carnitine. Raw garlic juice, with allicin as its primary compound, has been shown to powerfully impact the gut microbiota. This study validated the benefits of raw garlic juice against CVD risk via modulation of the gut microbiota and its metabolites. Allicin supplementation significantly decreased serum TMAO in ʟ-carnitine-fed C57BL/6J mice. It also reduced aortic lesions and altered the fecal microbiota in carnitine-induced, atherosclerosis-prone, apolipoprotein E-deficient mice. In human subjects exhibiting high TMAO production, raw garlic juice intake for a week reduced TMAO formation, improved gut microbial diversity, and increased the relative abundances of beneficial bacteria. In in vitro study, raw garlic juice inhibited γ-butyrobetaine (γBB) and trimethylamine (TMA) production by the gut microbiota. Thus, raw garlic juice can potentially prevent cardiovascular disease by decreasing TMAO production through gut microbiota modulation.
... Six-week-old male C57BL/6J mice were purchased from Taiwan National Laboratory Animal Center and housed in an alternating light/dark cycle (12 h) room with a temperature of 23±2°C and relative humidity of 50-70%. 24,25 After two weeks of adaptive feeding, the mice (n=192) were randomly assigned to four groups: (1) control diet (Research Diets, Inc., NJ, USA; D12450K)+intraperitoneal injection of phosphate buffer saline (PBS); (2) Palm oilcontaining high-fat diet (P-HFD; Gubra Amylin NASH (GAN) diet; Research Diets, Inc., NJ, USA; D09100310)+intraperitoneal injection of PBS; (3) P-HFD+intraperitoneal injection of LPS (500 µg/kg bw/week; LPS from Escherichia coli O55:B5; Sigma-Aldrich; L2880); and (4) P-HFD+intraperitoneal injection of CCl 4 (320 µg/kg bw/week; Merck Millipore; code 1.02209.1000). Control diet comprises 10 kcal% fat and carbohydrates, mainly in the form of corn starch. ...
... Plasma FITC-dextran measurements were performed using a uorometer at 485 nm of excitation and 538 nm of emission (Fluoroskan Ascent FL, Thermo Fisher Scienti c, USA) in black 96-well plates. 25 Statistical analysis Data are represented as mean±standard deviation (SD). An unpaired two-tailed Student's t-test or oneway ANOVA with Tukey's range test was used to compare group means. ...
Animal models of non-alcoholic steatohepatitis (NASH) and liver fibrosis are essential for preclinical research of novel drugs. A high-fat diet (HFD) animal model has an indispensable role in the research of gut-liver axis by generating an imbalance of gut microbiota and intestinal leakage, resulting in translocation of harmful bacterial metabolites and lipopolysaccharides (LPSs) to the liver, triggering hepatic immune responses, and stimulating NASH and liver fibrosis. Replacing trans-fat with palm oil in HFDs is an emerging animal model with human translatability in terms of liver biopsy phenotype and transcriptome changes. We developed the NASH and fibrosis C57BL/6J mouse model using a palm oil-containing high-fat diet (P-HFD) combined with LPS to simulate gut dysbiosis and endotoxemia and examined the role of carbon tetrachloride (CCl 4 ) on the gut-liver axis. We developed the mouse models, and the mice were fed P-HFD with or without intraperitoneal LPS/CCl 4 injections. NASH/fibrosis progression and gut microbiota shift were examined at 4, 8, 12, 16, 20, and 24 weeks (n=192). The animal model showed obesogenic and metabolic changes, hepatomegaly, increased hepatic lipid levels, NASH phenotype, increased gut dysbiosis, changes in gut microbiota and its function, reduced beneficial bacteria, increased pathogenic related microbiome, intestinal leakage, and endotoxemia. P-HFD with LPS supplementation resulted in comparable NASH, intestinal leakage, and endotoxemia phenotypes compared with the P-HFD group, but worsened the degree of intestinal microbiota dysbiosis by increasing the occurrence of pathogenic bacteria and reducing beneficial microbiota. P-HFD with CCl 4 resulted in a liver fibrosis phenotype and produced a more severe gut microbiota shift. These mouse models could be informative for a researcher focused on the gut-liver axis and could be used as valuable tool for preclinical drug testing.
... Curcumin processed a variety of bioactivities such as antioxidant, anti-inflammatory, and hepatoprotective effects, and a systematic review and dose-response meta-analysis of randomized controlled trials demonstrated that curcumin could ameliorate visceral fat and abdominal obesity in NAFLD patients [60]. Allicin (diallyl thiosulfonate), a bioactive component from the aqueous extracts of garlic, could decrease the abundance of gut microbiota, like Christensenellaceae and Ruminococcaceae, in alcoholic hepatic steatosis mice, resulting in a reduction of hepatic triacylglycerol level [61,62]. ...
... Allicin, a bioactive compound from garlic, could attenuate AFLD in C57BL/6 mice by increasing the levels of glutathione (GSH), CAT, and the activity of alcohol dehydrogenase (ADH), as well as decreasing the levels of SERBP-1c, CYP2E1, TNF-α, and interleukins 9 Oxidative Medicine and Cellular Longevity [107]. Also, allicin could alleviate alcohol-induced hepatic steatosis in C57BL/6 mice by modifying gut dysbiosis and then reducing the production of lipopolysaccharide (LPS) and further inhibiting TLR4-mediated inflammation [62]. Besides, the consumption of the ginger extract could significantly regulate lipid homeostasis in Wistar rats by increasing the expression of hepatocyte nuclear factor 4 α gene (HNF4A), while decreasing the expression of the protein tyrosine phosphatase 1B gene (PTP1B) [108,148]. ...
Fatty liver disease (FLD), including nonalcoholic fatty liver disease (NAFLD) and alcoholic fatty liver disease (AFLD), is a serious chronic metabolic disease that affects a wide range of people. Lipid accumulation accompanied by oxidative stress and inflammation in the liver is the most important pathogenesis of FLD. The plant-based, high-fiber, and low-fat diet has been recommended to manage FLD for a long time. This review discusses the current state of the art into the effects, mechanisms, and clinical application of plant-based foods in NAFLD and AFLD, with highlighting related molecular mechanisms. Epidemiological evidence revealed that the consumption of several plant-based foods was beneficial to alleviating FLD. Further experimental studies found out that fruits, spices, teas, coffee, and other plants, as well as their bioactive compounds, such as resveratrol, anthocyanin, curcumin, and tea polyphenols, could alleviate FLD by ameliorating hepatic steatosis, oxidative stress, inflammation, gut dysbiosis, and apoptosis, as well as regulating autophagy and ethanol metabolism. More importantly, clinical trials confirmed the beneficial effects of plant-based foods on patients with fatty liver. However, several issues need to be further studied especially the safety and effective doses of plant-based foods and their bioactive compounds. Overall, certain plant-based foods are promising natural sources of bioactive compounds to prevent and alleviate fatty liver disease.
... Allicin, the principal active component of garlic (Allium sativum, Liliaceae), has been suggested to exert various pharmacological effects such as anti-oxidative stress, anti-inflammation, and anti-apoptosis [18][19][20]. Intriguingly, previous Dong Li and Haipeng Liang contributed equally to this work. study has showed that allicin has protective effects in leadinduced hematopoietic stem cell aging (30 μg/kg) and cognitive impairment (30 mg/kg) [21,22]. ...
... Accumulating evidences has indicated that lead exposure could induce oxidative stress and result in bone damages. Allicin is a bioactive component which exerts a variety of biological effects including anti-oxidative stress, anti-inflammation, and anti-apoptosis [18][19][20]. However, the protective effects of allicin on lead-induced bone loss are still not fully clarified. ...
The aim of this study was to investigate the effects of allicin on lead-induced bone loss in mice. Male C57BL/6 J mice (3-weeks-old) were randomly divided into four groups: control group, lead group, allicin+lead group, and allicin group. Micro-CT, histology, oxidative stress, and osteoclastogenesis-related gene expression were analyzed. The results showed that allicin significantly ameliorated lead-induced bone loss, reduced oxidative stress, and inhibited osteoclastogenesis in mice. Moreover, we found that allicin upregulated the expression of SIRT1 and deacetylation of FoxO1. In conclusion, our study demonstrated that allicin exerts protective effects on lead-induced bone loss via antioxidant activity, preventing osteoclastogenesis, and activating SIRT1/FOXO1 pathway in mice, implying a potential therapy for lead-induced bone loss.
... Some of these components, including Allicin, have demonstrated hepatoprotective effects. Allicin, for instance, exhibits antiinflammatory properties by suppressing the expression of LPS, CD14, TLR4, TNF-α, IL-1β, and IL-6, thereby ameliorating the lipopolysaccharide (LPS)-CD14-toll-like receptor 4 (TLR4)-induced inflammatory pathway in the liver [40,41]. Certain compounds in garlic, such as allin, allyl cysteine, diallyl disulfide, and allyl disulfide, act as scavengers of superoxide anion radicals, mitigating lipid peroxidation and hepatocyte damage [42][43][44]. ...
Objective
Employing network pharmacology and molecular docking, the study predicts the active compounds in garlic and elucidates their mechanism in inhibiting the development of alcoholic liver disease (ALD). ALD is a global chronic liver disease with potential for hepatocellular carcinoma progression.
Methods
The main active ingredients and targets of garlic were identified through screening the TCMSP, TCM-ID, and ETCM databases. ALD disease targets were sourced from DisGeNET, GeneCards, and DiGSeE databases, and intervention targets for garlic were determined through intersections. Protein interaction networks were constructed using the STRING platform, and GO and KEGG pathway enrichment analyses were performed with R software. The garlic component-disease-target network was established using Cytoscape software. Validation of active ingredients against core targets was conducted through molecular docking simulations using AutoDock Vina software. Expression validation of core targets was carried out using human sequencing data of ALD obtained from the GEO database.
Results
Integration of garlic drug targets with ALD disease targets identified 83 target genes. Validation through an alcohol-induced ALD mouse model supported certain network pharmacology findings, suggesting that garlic may impede disease progression by mitigating the inflammatory response and promoting ethanol metabolism.
Conclusion
This study provides insights into the potential therapeutic mechanisms of garlic in inhibiting ALD development. The identified active ingredients offer promising avenues for further investigation and development of treatments for ALD, emphasizing the importance of botanical remedies in liver disease management.
... Allicin has been found to ameliorate intervertebral disc degeneration through the inhibition of oxidative stress and reduction in apoptosis [10], and it can also delay the progression of pulmonary arterial hypertension through the modulation of proinflammatory and profibrotic markers in the lung and heart [11]. Additionally, certain studies have indicated that allicin has the potential to reduce hepatic steatosis and enhance cardiovascular phenotypes through the modulation of gut microbiota [12][13][14]. Importantly, Zhao et al. [15] recently reported that H2S-mediated Keap1 S-sulfhydration alleviates liver damage through the activation of Nrf2 and that the administration of the exogenous H2S donor plays a protective role in streptozotocin (STZ) plus HFD-induced, or CCl 4 -stimulated, liver dysfunction. Dong et al. [16] found that by activating Nrf2, the levels of TNF-α and IL-1β in the hippocampus can be significantly reduced, thereby alleviating oxidative stress injury in the hippocampus of rats. ...
The global burden of liver disease is enormous, which highlights the need for effective hepatoprotective agents. It was reported that allicin exhibits protective effects against a range of diseases. In this study, we further evaluated allicin’s effect and mechanism in acute hepatic injury. Liver injury in mice was induced by intraperitoneal injection with 1% CCl4 (10 mL/kg/day). When the first dose was given, CCl4 was given immediately after administration of different doses of allicin (40, 20, and 10 mg/kg/day) as well as compound glycyrrhizin (CGI, 80 mg/kg/day), and then different doses of allicin (40, 20, and 10 mg/kg/day) as well as compound glycyrrhizin (CGI, 80 mg/kg/day) were administrated every 12 h. The animals were dissected 24 h after the first administration. The findings demonstrated a significant inhibition of CCl4-induced acute liver injury following allicin treatment. This inhibition was evidenced by notable reductions in serum levels of transaminases, specifically aspartate transaminase, along with mitigated histological damage to the liver. In this protective process, allicin plays the role of reducing the amounts or the expression levels of proinflammatory cytokines, IL-1β, IL-6. Furthermore, allicin recovered the activities of the antioxidant enzyme catalase (CAT) and reduced the production of malondialdehyde (MDA) in a dose-dependent manner, and also reduced liver Caspase 3, Caspase 8, and BAX to inhibit liver cell apoptosis. Further analysis showed that the administration of allicin inhibited the increased protein levels of Nuclear factor-erythroid 2-related factor 2 (Nrf2) and NAD(P)H:quinone oxidoreductase 1 (NQO1), which is related to inflammation and oxidative stress. The in vitro study of the LPS-induced RAW264.7 inflammatory cell model confirmed that allicin can inhibit important inflammation-related factors and alleviate inflammation. This research firstly clarified that allicin has a significant protective effect on CCl4-induced liver injury via inhibiting the inflammatory response and hepatocyte apoptosis, alleviating oxidative stress associated with the progress of liver damage, highlighting the potential of allicin as a hepatoprotective agent.
... Researchers suggest that only 5 mg of allicin supplementation can promote hepatoprotective effects. Panyod et al. [64] observed that allicin treatment in vivo can reduce liver inflammation by promoting the control of TLR4 hepatic levels and pro-inflammatory cytokines in mice with alcoholic hepatic steatosis. These results are significant for guiding a safe dosage in future clinical studies in patients with liver disease. ...
Chronic inflammation is associated with the development and progression of several non-communicable diseases (NCDs), such as diabetes, cardiovascular disease, chronic kidney disease, cancer, and non-alcoholic fatty liver disease. Evidence suggests that pattern recognition receptors (PRRs) that identify pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs) are crucial in chronic inflammation. Among the PRRs, Toll-like receptor 4 (TLR4) stimulates several inflammatory pathway agonists, such as the nuclear factor-κB (NF-κB), interferon regulator factor 3 (IRF3), and nod-like receptor pyrin domain containing 3 (NLRP3) pathways, that consequently trigger the expression of pro-inflammatory biomarkers, increasing the risk of NCD development and progression. Currently, studies have focused on the antagonistic potential of bioactive compounds, following the concept of food as a medicine, in which nutritional strategies may mitigate inflammation via TLR4 modulation. Thus, this narrative review discusses preclinical evidence concerning bioactive compounds from fruit, vegetable, spice, and herb extracts (curcumin, resveratrol, catechin, cinnamaldehyde, emodin, ginsenosides, quercetin, allicin, and caffeine) that may regulate the TLR4 pathway and reduce the inflammatory response. Bioactive compounds can inhibit TLR4-mediated inflammation through gut microbiota modulation, improvement of intestinal permeability, inhibition of lipopolysaccharide (LPS)-TLR4 binding, and decreasing TLR4 expression by modulation of microRNAs and antioxidant pathways. The responses directly mitigated inflammation, especially NF-κB activation and inflammatory cytokines release. These findings should be considered for further clinical studies on inflammation-mediated diseases.
... Freshly crushed garlic contains many Allicin (diallyl thiosulfinate), a crucial active compound in garlic. Allicin has a remarkable property to cure various anti-inflammatory, anti-microbial, cardiovascular protection, and immunity functions [19][20][21]. It has made it a popular drug in clinics in recent years [22]. ...
Squamous carcinoma (SCC) is one of the most common types of cancer in the world. The increasing rates of industrialization and the subsequent environmental changes have aggravated the issue of skin cancer. The stern topical barrier is impaired in diseases like skin cancer while challenging to break. Chemotherapy and surgery are no longer the only ways to treat skin cancers. Hence, we effectively developed allicin-loaded poly (lactic-co-glycolic acid) nanoparticles (NPs), designated as Allicin@NPs, for the treatment of in vitro squamous carcinoma cells has been developed. The Allicin@NPs characterization of the morphology investigation was assessed by the high-resolution transmission electron microscopy. Hydrodynamic parameters and zeta potential were investigated using the dynamic light scattering technique. The in vitro MTT analysis has displayed a substantial inhibition effect of Allicin@NPs on squamous carcinoma cells (B16F10 and A431 cells), and the proliferation of the cells was examined by EdU staining methods. Furthermore, morphological examination of the SCC cells was confirmed by ethidium bromide and acridine orange and Hoechst 33342 nuclear staining methods. The mechanism of apoptosis was further investigated by flow cytometry analysis. Notably, Allicin@NPs have proved that the dramatically improved animal model systemic toxicity profiles of the Allicin is recognized as potential candidates for SCC therapy employing these Allicin@NPs and needs further investigation.
... 120 Allicin has been reported to modify the gut microbiome associated with fatty liver disease. 14,121,122 Allicin supplementation also reportedly altered the gut-microbiota composition and decreased TMAO generation by the gut microbiota in mice administered carnitine (Table 4). 123 Allicin relieves atherosclerosis in ApoE À/À , and raw garlic juice (containing allicin) reduces plasma TMAO and increases beneficial bacteria, including Faecalibacterium prausnitzii and Akkermansia spp. in humans. ...
Dietary nutrients are associated with the development of cardiovascular disease (CVD) both through traditional pathways (inducing hyperlipidemia and chronic inflammation) and through the emergence of a metaorganism-pathogenesis pathway (through the gut microbiota, its metabolites, and host). Several molecules from food play an important role as CVD risk-factor precursors either themselves or through the metabolism of the gut microbiome. Animal-based dietary proteins are the primary source of CVD risk-factor precursors; however, some plants also possess these precursors, though at relatively low levels compared with animal-source food products. Various medications have been developed to treat CVD through the gut-microbiota–circulation axis, and they exhibit potent effects in CVD treatment. Nevertheless, such medicines are still being improved, and there are many research gaps that need to be addressed. Furthermore, some medications have unpleasant or adverse effects. Numerous foods and herbs impart beneficial effects upon health and disease. In the past decade, many studies have focused on treating and preventing CVD by modulating the gut microbiota and their metabolites. This review provides an overview of the available information, summarizes current research related to the gut-microbiota–heart axis, enumerates the foods and herbs that are CVD-risk precursors, and illustrates how metabolites become CVD risk factors through the metabolism of gut microbiota. Moreover, we present perspectives on the application of foods and herbs—including prebiotics, probiotics, synbiotics, postbiotics, and antibiotic-like substances—as CVD prevention agents to modulate gut microbiota by inhibiting gut-derived CVD risk factors.
Taxonomy (classification by EVISE)
Cardiovascular disease, gut microbiota, herbal medicine, preventive medicine, dietary therapy, nutrition supplements.
... Allicin modulated the Keap1-Nrf2 regulatory pathway, leading to the transcription of cytoprotective genes and the decline of oxidative damage (Marón et al. 2020). Also, allicin alleviated the inflammation caused by diabetic macroangiopathy by attenuating the NF-κB level (Li et al. 2020), as well as TNF-α (Panyod et al. 2020). Moreover, allicin enhanced GPx that contributed negatively to the prevention of NF-κB, TNF-α, mRNA expression, and ROS in monocytes infected with Mycobacterium tuberculosis (Hasan et al. 2006). ...
Acrylamide (ACR) is an unsaturated monomer that served various fields; however, it is a potent neurotoxin. The target of the present study is to explore the neuroprotective efficacy of allicin and melatonin on ACR-induced neurotoxicity. Thirty-six male adult rats were non-selectively separated into six groups: placebo, allicin (20 mg/kg b.w daily per os), melatonin (10 mg/kg b.w 3 times/week per os), ACR (50 mg/kg b.w daily per os), ACR-allicin, and ACR-melatonin at the same doses as the preceding groups. The assessment of brain biomarkers, neurotransmitters, antioxidative status, Nrf2 signaling pathway, and histopathological analyses was performed following 21 days. ACR exposure induced brain lipid and DNA oxidative damage as well as reduced the glutathione (GSH) levels. The obvious brain oxidative injuries contributed to distinct brain dysfunction that was assured by alteration of brain neurotransmitters (serotonin, dopamine, acetylcholine, and acetylcholinesterase) and pathological brain lesions. Furthermore, ACR exposure increased hydroxy deoxyguanosine (8-OHdG), tumor necrosis factor-α (TNF-α), and amyloid protein (AB1-42). Finally, the mRNA transcripts of brain Keap-1, Nrf2, and NF-kB were upregulated after ACR intoxication. Interestingly, allicin and melatonin alleviated the ACR-induced brain damage assessed by the normalization of the mentioned analyses. The present study demonstrated the protective role of both allicin and melatonin in ACR-prompted neuropathy by alleviation of redox imbalance and enhancement of neurotransmitters as well as relieving DNA damage and anti-inflammatory effect.
... Alcohol consumption could cause the imbalance of gut microflora and destroy the homeostasis of bile acid metabolism. Recently, the critical role of gut microflora and bile acids in ALD has been demonstrated (Hartmann et al., 2018;Panyod et al., 2020). Moreover, Wahlstrom et al. (Wahlström et al., 2017) have confirmed the concept of gut microflora-bile acid axis. ...
Alcoholic liver disease (ALD) is the most common complication of alcohol abuse, while we lack safe and effective treatment for ALD. This study aimed to explore the effects of nicotinamide riboside (NR) on lipid metabolism and gut microflora‐bile acid axis in alcohol‐exposed mice. NR significantly improved liver histopathological damage and abnormal liver function. NR as a provider of nicotinamide adenine dinucleotide (NAD+) increased the NAD+/NADH ratio. Meanwhile, NR inhibited the activation of the protein phosphatase 1 signaling pathway, decreased the liver triglyceride and total bile acid levels, and reduced lipid accumulation. According to the results of gut microflora species analysis, NR intervention changed the microbial community structure at the phylum, family and genus levels, and the species abundances returned to a level similar to these of the normal control group. Besides, the results of high‐performance liquid chromatograph‐mass spectrometry showed that NR intervention resulted in fecal bile acid levels tending to be normal with decreased chenodeoxycholic acid level and increased deoxycholic acid and hyocholic acid levels. Spearman's correlation analysis showed a correlation between gut microflora and bile acids. Therefore, NR supplementation has the potential to prevent ALD, and its mechanism may be related to regulating lipid metabolism disorders and the gut microflora‐bile acid axis.
... 236 Similarly, a metaanalysis of RCTs showed reductions in fasting blood glucose with garlic extracts. 237 In mice, allicin improved gut barrier properties, 238 and also changed the GM toward fewer numbers of Streptococcus, Aeromonas, Vibrio, Corynebacterium, Marinomonas, among other, was observed, and explained by the anti-microbial activity of allicin. This antimicrobial activity is recognized for some time, 239 including activity against Gram-positive and Gram-negative bacteria, certain fungi such as C. albicans, and also anti-parasitic and anti-viral activity. ...
Phytochemicals are bioactive compounds found in plants that play a key role in promoting health and preventing diseases. Present in fruits, vegetables, grains, and seed oils, these compounds are considered safe for consumption due to the co‐evolution and adaptation between mammals and plants. Due to their wide‐ranging biological effects, they have attracted considerable research interest. This comprehensive review explores the mechanisms of action, health benefits, and applications of dietary phytochemicals, with a particular focus on key groups such as polyphenols, flavonoids, and carotenoids. Research shows that dietary phytochemicals interact with nuclear and membrane receptors, influence metabolic pathways, and affect epigenetic modifications. Our review highlights the broad range of biological activities of these compounds, including antioxidant, antibacterial, anti‐inflammatory, anti‐diabetic, and anticancer effects, all of which contribute to their health‐promoting properties. Clinical evidence supports their role in the prevention and management of diseases such as cardiovascular disorders, metabolic conditions, and cancer, with diets rich in phytochemicals being linked to a lower risk of disease. Phytochemicals are also at the cutting edge of applications in food preservation, dietary supplements, and emerging medical treatments. Additionally, we identified advancements in extraction and identification techniques, particularly in metabolomics, which further enhance their applications in these areas. Despite their promising benefits, challenges such as bioavailability, regulatory barriers, and the need for robust clinical trials persist. However, innovative delivery systems like nanoparticles, liposomes, and encapsulation offer potential solutions to enhance bioavailability by improving absorption and stability. The review concludes by emphasizing the potential of personalized nutrition and combination therapies to enhance the health benefits of dietary phytochemicals while stressing the need for advancements in extraction methods, clinical trials, and bioavailability.
In the era of free antibiotics used in animal production, the application of feed additives should be prioritized to improve poultry health and production. This study was conducted to evaluate the influences of garlic fermented by Lactobacillus spp. on the growth rate, intestinal microorganisms, and immune response of turkey broilers. A completely randomised design was used, involving 90 turkey broilers aged 1–56 days, with five treatments and three replicates per treatment. The birds were given feed and water ad libitum for entire the experiment period. The treatments included the supplement of aqueous extract from fermented garlic (FG) to drinking water. The results showed that broilers supplemented with 0.8% FG exhibited the largest final body weight (1,158 g/bird), body weight gain (19.64 g/bird/day), and significantly improved feed conversion ratio (1.962) while decreased the feed intake of turkey broilers from to 1–56 days. The immune organ indices including the spleen, thymus, and bursa of Fabricius indices were increased in the treatment of 0.6% FG (P<0.05) while antibody titres (at 28 and 42 days of age) were improved in the 0.6% and 0.8% FG treatment (P<0.05). Clostridium perfringens and Salmonella spp. were not detected in the intestines of these birds, while the amount of Escherichia coli was reduced (P<0.05) and Lactobacillus spp. increased (P>0.05) without a significant effect. It can be concluded that supplementation with 0.8% FG improved growth performance, and 0.6% FG may enhance the immunity of turkeys. The use of 0.6 and 0.8% FG could be widely applied for poultry production.
Mounting evidence implicates the gut microbiota as a possible key susceptibility factor for atherosclerosis (AS). The employment of dietary phytochemicals that strive to target the gut microbiota has gained scientific support for treating AS. This study conducted a general overview of the links between the gut microbiota and AS, and summarized available evidence that dietary phytochemicals improve AS via manipulating gut microbiota. Then, the microbial metabolism of several dietary phytochemicals was summarized, along with a discussion on the metabolites formed and the biotransformation pathways involving key gut bacteria and enzymes. This study additionally focused on the anti-atherosclerotic potential of representative metabolites from dietary phytochemicals, and investigated their underlying molecular mechanisms. In summary, microbiota-dependent dietary phytochemical therapy is a promising strategy for AS management, and knowledge of "phytochemical-microbiota-biotransformation" may be a breakthrough in the search for novel anti-atherogenic agents.
Liver injury is a life-threatening condition, and the hepatoprotective potential of cyanidin-3-glucoside (C3G) has been previously demonstrated. However, due to the low bioavailability, it has been doubtful that relatively low...
Coccidiosis is a protozoan intestinal disease that reduces the production of the sheep industry and causes large economic losses for sheep. Although chemically synthesised drugs are routinely employed to treat coccidiosis in sheep, the anticoccidial drug resistance and drug residues in edible meat have prompted an urgent search for alternatives. Herein, the anticoccidial properties of diclazuril, a conventional anticoccidial drug, and Allium sativum, Houttuynia cordata and Portulaca oleracea were assessed. Forty 45-day-old lambs naturally infected with Eimeria spp. were selected and randomly divided into five groups. The results showed that the sheep treated for coccidiosis had considerably decreased average daily gain (ADG) during both administration and withdrawal of the drug compared to the control group. Furthermore, at days 14, 21, 28 and 35, respectively, the three herbs and diclazuril had similar anticoccidial effects, with lower oocysts per gram (OPG) than the control group. On day 78, OPG in the three herbal groups was significantly lower than in the diclazuril group. In addition, the abundance and composition of the gut microbiota were changed in sheep treated with the three herbs and diclazuril compared to the untreated sheep. Moreover, some intestinal microorganisms have a correlation with OPG and ADG when using Spearman correlation analysis. In summary, our results suggest that all three herbs produce anticoccidial effects similar to diclazuril and modulate the balance of gut microbiota in growing lambs.
Excessive alcohol intake will aggravate the health risk between the liver and intestine and affect the multi-directional information exchange of metabolites between host cells and microbial communities. Because of the side effects of clinical drugs, people tend to explore the intervention value of natural drugs on diseases. As a flavor substance, spices have been proven to have medicinal value, but they are still rare in treating hepatointestinal diseases caused by alcohol. This paper summarized the metabolic transformation of alcohol in the liver and intestine and summarized the potential value of various perfume active substances in improving liver and intestine diseases caused by alcohol. It is also found that bioactive substances in spices can exert antioxidant activity in the liver and intestine environment and reduce the oxidative stress caused by diseases. These substances can interfere with fatty acid synthesis, promote sugar and lipid metabolism, and reduce liver injury caused by steatosis. They can effectively regulate the balance of intestinal flora, promote the production of SCFAs, and restore the intestinal microenvironment.
There is limited knowledge about the factors that drive gut–liver axis changes after selenium (Se) deficiency‐induced gut or liver injuries. Thus, we tested Se deficiency in mice to determine its effects on intestinal bacterial balance and whether it induced liver injury. Serum Se concentration, lipopolysaccharide (LPS) level, and liver injury biomarkers were tested using a biochemical method, while pathological changes in the liver and jejunum were observed via hematoxylin and eosin stain, and a fluorescence spectrophotometer was used to evaluate intestinal permeability. Tight junction (TJ)‐related and toll‐like receptor (TLR) signaling‐related pathway genes and proteins were tested using quantitative polymerase chain reaction, western blotting, immunohistochemistry, and 16S ribosomal ribonucleic acid gene‐targeted sequencing of jejunum microorganisms. Se deficiency significantly decreased glutathione peroxidase activity and disrupted the intestinal flora, with the most significant effect being a decrease in Lactobacillus reuteri . The expression of TJ‐related genes and proteins decreased significantly with increased treatment time, whereas supplementation with Se, fecal microbiota transplantation, or L. reuteri reversed these decreases. Signs of liver injury and LPS content were significantly increased after intestinal flora imbalance or jejunum injury, and the levels of TLR signaling‐related genes were significantly increased. The results indicated that Se deficiency disrupted the microbiota balance, decreased the expression of intestinal TJ factors, and increased intestinal permeability. By contrast, LPS increased due to a bacterial imbalance, which may induce inflammatory liver injury via the TLR4 signaling pathway.
A microbial ecosystem is a complex community of multiple bacterial interactions. The potential role of gut microbiota in human health has already attracted the attention of many researchers. Dysregulation of the gut microbial community has been suggested to be closely associated with the progression of various chronic diseases. Malignant neoplasms represent a major global health burden and are now the leading cause of death. The formation of tumors is often thought to be influenced by genetic and environmental factors. Recent research advances have indicated that multiple malignancies may also be attributed to the gut microbiota. In this review, we highlight the complex interactions between gut microbes and their metabolites, as well as the potential impact of gut microecology on the occurrence and development of tumors. In addition, potential strategies for targeted therapy of tumors using gut microecology are discussed. In the near future, intestinal microecology is likely to be used for early screening of tumors and subsequent clinical treatment.
A high-fat diet (HFD) animal model has an indispensable role in the research of gut-liver axis by generating an imbalance of gut microbiota and intestinal leakage, resulting in translocation of harmful bacterial metabolites and lipopolysaccharides (LPSs) to the liver, triggering immune responses, and stimulating non-alcoholic steatohepatitis (NASH). Replacing trans-fat with palm oil in HFDs is an emerging animal model with human translatability in terms of liver biopsy phenotype and transcriptome changes. We developed the NASH and fibrosis mouse model using a palm oil-containing high-fat diet (P-HFD) combined with LPS to simulate gut dysbiosis and endotoxemia and examined the role of carbon tetrachloride (CCl 4 ) on the gut-liver axis. The mice were fed P-HFD with or without intraperitoneal LPS/CCl 4 injections. NASH/fibrosis progression and gut microbiota shift were examined at 4, 8, 12, 16, 20, and 24 weeks (n = 192). The P-HFD animal model showed obesogenic and metabolic changes, hepatomegaly, NASH phenotype, increased gut dysbiosis, changes in gut microbiota and its function, reduced beneficial bacteria, increased pathogenic related microbiome, intestinal leakage, and endotoxemia. P-HFD with LPS supplementation resulted in comparable NASH phenotypes compared with the P-HFD group, but worsened the degree of intestinal microbiota dysbiosis by increasing the occurrence of pathogenic bacteria and reducing beneficial microbiota. P-HFD with CCl 4 resulted in a liver fibrosis phenotype and produced a more severe gut microbiota shift. These mouse models could be informative for a researcher focused on the gut-liver axis and could be used as valuable tool for preclinical drug testing.
Alcohol-associated liver disease (ALD) comprises a spectrum of liver diseases that include: steatosis to alcohol-associated hepatitis, cirrhosis, and ultimately hepatocellular carcinoma. The pathophysiology and potential underlying mechanisms for alcohol-associated liver disease are unclear. Moreover, the treatment of ALD remains a challenge. Intestinal microbiota include bacteria, fungi, and viruses, that are now known to be important in the development of ALD. Alcohol consumption can change the gut microbiota and function leading to liver disease. Given the importance of interactions between intestinal microbiota, alcohol, and liver injury, the gut microbiota has emerged as a potential biomarker and therapeutic target. This review focuses on the potential mechanisms by which the gut microbiota may be involved in the pathogenesis of ALD and explains how this can be translated into clinical management. We discuss the potential of utilizing the gut microbiota signature as a biomarker in ALD patients. Additionally, we present an overview of the prospect of modulating the intestinal microbiota for the management of ALD.
Allicin is the main active ingredient in freshly-crushed garlic and some other allium plants, and its anticancer effect on cancers of digestive system has been confirmed in many studies. The aim of this review is to summarize epidemiological studies and in vitro and in vivo investigations on the anticancer effects of allicin and its secondary metabolites, as well as their biological functions. In epidemiological studies of esophageal cancer, liver cancer, pancreatic cancer, and biliary tract cancer, the anticancer effect of garlic has been confirmed consistently. However, the results obtained from epidemiological studies in gastric cancer and colon cancer are inconsistent. In vitro studies demonstrated that allicin and its secondary metabolites play an antitumor role by inhibiting tumor cell proliferation, inducing apoptosis, controlling tumor invasion and metastasis, decreasing angiogenesis, suppressing Helicobacter pylori, enhancing the efficacy of chemotherapeutic drugs, and reducing the damage caused by chemotherapeutic drugs. In vivo studies further demonstrate that allicin and its secondary metabolites inhibit cancers of the digestive system. This review describes the mechanisms against cancers of digestive system and therapeutic potential of allicin and its secondary metabolites.
Background: Hepatic ischemia/reperfusion (I/R) injury to the liver is a significant cause of morbidity and mortality following liver surgery, trauma, and hemorrhagic shock. It was reported that allicin, a type of garlic compound, had a protective effect against other hepatic diseases. Allicin's ability to protect against liver injury caused by ischemic reperfusion remains unknown. As a result, we conducted this study to determine allicin's effects and mechanism of action in hepatic I/R injury. Method: The liver I/R injury model was established by clamping the blood supply to the left and middle liver lobes. Three days prior to the hepatic I/R injury, different concentrations of allicin were gavaged. Then, hepatic function, histological changes, apoptosis markers, oxidative stress, and inflammatory cytokines were measured, and the molecular mechanisms were evaluated using western blot. Another separation experiment used IRAK-M knockout mice and peroxisome proliferator-activated receptor-gamma (PPARγ) inhibitor to deduce the molecular mechanisms. Results: Pretreatment with allicin prior to hepatic I/R injury reduced liver damage by inhibiting aminotransferase activity and alleviating liver injury. It significantly decreased cell apoptosis, interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) production, and hepatic oxidative stress. Furthermore, this study demonstrated that GW9662 (inhibitor of PPARγ) abrogated allicin's positive effect by inhibiting PPARγ expression while suppressing IRAK-M expression. Thus, the depletion of IRAK-M cannot influence the expression of PPARγ. The down-regulation of PPARγ-IRAK-M disabled the protection of allicin in I/R injury. Conclusion: Allicin protects against hepatic I/R injury via dose-dependent regulation of the PPARγ-IRAK-M-TLR4 signaling pathway, and it may be a potential drug in future clinical treatment.
Background and aim
Garlic essential oil (GEO) isolated from Garlic (Allium sativum L.) exerts biological activities in disease prevention, particularly in metabolic and liver diseases, and is used for a dietary therapy for centuries. However, due to the side effects associated with the excessive consumption of GEO, there is a need to evaluate the safety of the GEO.
Experimental procedure
Ames test using five Salmonella typhimurium strains (TA98, TA100, TA102, TA1535, and TA1537) and Chinese hamster ovary (CHO–K1) cells with or without metabolic activation (S9 system), and mammalian erythrocyte micronucleus test were used to assess the genotoxicity and clastogenic effects of GEO. A repeated dose of GEO (15, 25, and 50 mg/kg body weight, p.o.) were administrated to ICR mice for 28 days to ascertain the subacute toxicity of GEO.
Results and conclusions
The results of the Ames test with or without S9 system indicated that GEO did not induce mutagenicity nor have clastogenic effects in CHO–K1 cells with or without S9 activation. Furthermore, GEO did not affect the ratio of immature to total erythrocytes or the number of micronuclei in immature erythrocytes of ICR mice after 24 and 48 h. In a 28-day oral toxicity assessment, GEO (15, 25, and 50 mg/kg body weight, p.o.)-fed ICR mice exhibited normal behaviors, mortality, body weight, daily intake, hematology, clinical biochemistry, and organ weight. GEO shows no genotoxicity, and the no-observed-adverse-effect level (NOAEL) for GEO is considered to be greater than 50 mg/kg bw/day orally for 28 days in mice.
Section
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Allicin, a thiosulfonate extract from freshly minced garlic, has been reported to have various biological effects on different organs and systems of animals and human. It can reduce oxidative stress, inhibit inflammatory response, resist pathogen infection and regulate intestinal flora. In addition, dozens of studies also demonstrated allicin could reduce blood glucose level, protect cardiovascular system and nervous system, and fight against cancers. Allicin was widely used in disease prevention and health care. However, more investigations on human cohort study are needed to verify the biological or clinical effects of allicin in the future. In this review, we summarized the biological effects of allicin from previous outstanding and valuable studies and provided useful information for future studies on the health effects of allicin.
Background
Intestinal mucosa barrier function and gut-liver axis are impaired by ethanol in chronic alcoholic liver disease (ALD). However, the possible mechanism is not clear. This study aimed to investigate the effects of Forkhead Box O4 (FOXO4) on alcohol-induced chronic liver injury and its molecular mechanism(s).
Methods
Male C57BL/6J mice were injected with or without FOXO4-WT, FOXO4-TB or NF-κB vectors, and fed with Lieber-DeCarli liquid diets containing 36% ethanol for eight weeks to induce chronic ALD. Thereafter, blood, liver, colon and fecal samples were collected. Biochemical parameters, endotoxin and inflammatory cytokines in the blood and antioxidant enzymes in the liver were tested by commercial kits. Histopathological changes in the liver were evaluated by HE staining. In addition, the mRNA and protein expression of FOXO4, NF-κB, ZO-1 and Occluding in the colon were measured by quantitative real-time PCR and Western blot, respectively. Furthermore, gut microbiota composition in the fecal samples was investigated with 16S rDNA sequencing.
Results
FOXO4 significantly ameliorated liver histopathological damage. Moreover, FOXO4 reduced the serum endotoxin, biochemical parameters (ALT, AST, ALP and TG), antioxidant enzymes (ROS and MDA), inflammatory cytokines (IL-6, IL-1β, and TNF-α), but restored the levels of GSH, SOD and IL-10. Furthermore, FOXO4 significantly inhibited the expression of NF-κB, p-NF-κB p65, p-IKKα and p-IKKβ, and up-regulated the expression of ZO-1 and Occludin. Additionally, FOXO4 modulated the gut microbiota composition and certain bacteria including Odoribacter, Parasutterella and Psychrobacter.
Conclusion
These findings suggest that FOXO4 protects against alcohol-induced chronic liver injury via inhibiting NF-κB and modulating gut microbiota in C57BL/6J mice.
A healthy gut microbiota (GM) is paramount for a healthy lifestyle. Alterations of the GM have been involved in the aetiology of several chronic diseases, including obesity and type 2 diabetes, as well as cardiovascular and neurodegenerative diseases. In pathological conditions, the diversity of the GM is commonly reduced or altered, often toward an increased Firmicutes/Bacteroidetes ratio. The colonic fermentation of dietary fiber has shown to stimulate the fraction of bacteria purported to have beneficial health effects, acting as prebiotics, and to increase the production of short chain fatty acids, e.g. propionate and butyrate, while also improving gut epithelium integrity such as tight junction functionality. However, a variety of phytochemicals, often associated with dietary fiber, have also been proposed to modulate the GM. Many phytochemicals possess antioxidant and anti-inflammatory properties that may positively affect the GM, including polyphenols, carotenoids, phytosterols/phytostanols, lignans, alkaloids, glucosinolates and terpenes. Some polyphenols may act as prebiotics, while carotenoids have been shown to alter immunoglobulin A expression, an important factor for bacteria colonization. Other phytochemicals may interact with the mucosa, another important factor for colonization, and prevent its degradation. Certain polyphenols have shown to influence bacterial communication, interacting with quorum sensing. Finally, phytochemicals can be metabolized in the gut into bioactive constituents, e.g. equol from daidzein and enterolactone from secoisolariciresinol, while bacteria can use glycosides for energy. In this review, we strive to highlight the potential interactions between prominent phytochemicals and health benefits related to the GM, emphasizing their potential as adjuvant strategies for GM-related diseases.
Human gut microbiota is a dynamic and variable system that can change over time and in response to different diets and treatments. There is currently no doubt that gut microbiota can provide interesting therapeutic opportunities, since it can metabolize biologically active molecules, drugs, and their precursors, and control their bioavailability. Moreover, it can produce both beneficial and dangerous metabolites that influence host’s health. In this review, we summarize the current knowledge on the involvement of gut microbiota in two chronic human pathologies that represent the greatest challenges of modern medicine: atherosclerosis and cancer. Interesting parallels are observed between the mechanisms and possible treatment approaches of these pathologies. Some of the common effects of therapeutic agents targeting both pathologies, such as anti-inflammatory activity, are partially mediated by the gut microbiota. We will discuss the effects of common drugs (metformin, statins and aspirin) and various nutraceuticals on gut microbiota and outline the pathways of microbial involvement in mediating the pleiotropic beneficial effects of these agents in atherosclerosis and cancer.
Noninfectious (autoimmune and immune-mediated) uveitis is an ocular inflammatory disease which can lead to blindness in severe cases. Due to the potential side effects of first-line drugs for clinical uveitis, novel drugs and targets against uveitis are still urgently needed. In the present study, using rat experimental autoimmune uveitis (EAU) model, we first found that minocycline treatment can substantially inhibit the development of EAU and improve the retinal function by suppressing the retinal microglial activation, and block the infiltration of inflammatory cells, including Th17, into the retina by decreasing the major histocompatibility complex class II (MHC II) expression in resident and infiltrating cells. Moreover, we demonstrated that minocycline treatment can remodel the gut microenvironment of EAU rats by restoring the relative abundance of Ruminococcus bromii, Streptococcus hyointestinalis, and Desulfovibrio sp. ABHU2SB and promoting a functional shift in the gut via reversing the levels of L-proline, allicin, aceturic acid, xanthine, and leukotriene B4, and especially increasing the production of propionic acid, histamine, and pantothenic acid. At last, we revealed that minocycline treatment can significantly attenuate the progression of EAU after inflammation onset, which may be explained by the role of minocycline in the remodeling of the gut microenvironment since selective elimination of retinal microglia on the later stages of EAU was shown to have little effect. These data clearly demonstrated that inhibition of microglial activation and remodeling of the gut microenvironment can suppress the development and progression of experimental autoimmune uveitis. Considering the excellent safety profile of minocycline in multiple clinical experiments, we suggest that minocycline may have therapeutic implications for clinical uveitis.
Eating habits and lifestyle directly impact general health. Consumption of fat- and sugar-rich foods and alcohol increase the risk of developing fatty liver disease. The prevalence of fatty liver disease is markedly critical, and its pathogenesis and progression are complicated. Chinese herbal medicine has been used to treat and prevent human diseases through-out history, and is a rich source of biologically active substances with unique curative properties. More recently, Chinese herbs and their extracts have been identified as a novel source of potential therapeutic agents in the prevention and treatment of fatty liver disease. Beneficial effects of these herbal medicines mean that they can be classified as novel candidates for the treatment and prevention of both alcoholic fatty liver disease (AFLD) and non-alcoholic fatty liver disease (NAFLD), in place of conventional allopathic treatments. In this review, we explore the current literature related to herbal medicines used for the treatment of or protection against fatty liver diseases and describe their mechanisms of action.
Excessive alcohol intake can alter the gut microbiota, which may underlie the pathophysiology of alcohol-related diseases. We examined gut microbiota composition and functions in patients with alcohol overconsumption for >10 years, compared to a control group of patients with a history of no or low alcohol intake. Faecal microbiota composition was assessed by 16S rRNA sequencing. Gut microbiota functions were evaluated by quantification of short-chain fatty acids (SCFAs) and predictive metagenome profiling (PICRUSt). Twenty-four patients, mean age 64.8 years (19 males), with alcohol overconsumption, and 18 control patients, mean age 58.2 years (14 males) were included. The two groups were comparable regarding basic clinical variables. Nutritional assessment revealed lower total score on the screening tool Mini Nutritional Assessment, lower muscle mass as assessed by handgrip strength, and lower plasma vitamin C levels in the alcohol overconsumption group. Bacteria from phylum Proteobacteria were found in higher relative abundance, while bacteria from genus Faecalibacterium were found in lower relative abundance in the group of alcohol overconsumers. The group also had higher levels of the genera Sutterella, Holdemania and Clostridium, and lower concentration and percentage of butyric acid. When applying PICRUSt to predict the metagenomic composition, we found that genes related to invasion of epithelial cells were more common in the group of alcohol overconsumers. We conclude that gut microbiota composition and functions in patients with alcohol overconsumption differ from patients with low consumption of alcohol, and seem to be skewed into a putative pro-inflammatory direction.
Nonalcoholic fatty liver disease (NAFLD) is the accumulation of fat in the liver in the absence of secondary causes. NAFLD is a multifactorial disease that results from the interaction of genetic predisposition and metabolic, inflammatory and environmental factors. Among these factors, dysregulation of gut microbiome has been linked to the development of fatty liver disease. The microbiome composition can be modified by dietary habits leading to gut microbiome dysbiosis, especially when a diet is rich in saturated fats, animal products and fructose sugars. Different species of bacteria in the gut metabolize nutrients differently, triggering different pathways that contribute to the accumulation of fat within the liver and triggering inflammatory cascades that promote liver damage. In this review, we summarize the current understanding of the roles of gut microbiota in mediating NAFLD development and discuss possible gut microbiota-targeted therapies for NAFLD. We summarize experimental and clinical evidence, and draw conclusions on the therapeutic potential of manipulating gut microbiota to decrease the incidence and prevalence of fatty liver disease.
Sequence-based approaches to study microbiomes, such as 16S rRNA gene sequencing and metagenomics, are uncovering associations between microbial taxa and a myriad of factors. A drawback of these approaches is that the necessary sequencing library preparation and bioinformatic analyses are complicated and continuously changing, which can be a barrier for researchers new to the field. We present three essential components to conducting a microbiome experiment from start to finish: first, a simplified and step-by-step custom gene sequencing protocol that requires limited lab equipment, is cost-effective, and has been thoroughly tested and utilized on various sample types; second, a series of scripts to integrate various commonly used bioinformatic tools that is available as a standalone installation or as a single downloadable virtual image; and third, a set of bioinformatic workflows and tutorials to provide step-by-step guidance and education for those new to the microbiome field. This resource will provide the foundations for those newly entering the microbiome field and will provide much-needed guidance and best practices to ensure that quality microbiome research is undertaken. All protocols, scripts, workflows, tutorials, and virtual images are freely available through the Microbiome Helper website (https://github.com/mlangill/microbiome-helper/wiki).
Background
VSEARCH is an open source and free of charge multithreaded 64-bit tool for processing and preparing metagenomics, genomics and population genomics nucleotide sequence data. It is designed as an alternative to the widely used USEARCH tool (Edgar, 2010) for which the source code is not publicly available, algorithm details are only rudimentarily described, and only a memory-confined 32-bit version is freely available for academic use.
Methods
When searching nucleotide sequences, VSEARCH uses a fast heuristic based on words shared by the query and target sequences in order to quickly identify similar sequences, a similar strategy is probably used in USEARCH. VSEARCH then performs optimal global sequence alignment of the query against potential target sequences, using full dynamic programming instead of the seed-and-extend heuristic used by USEARCH. Pairwise alignments are computed in parallel using vectorisation and multiple threads.
Results
VSEARCH includes most commands for analysing nucleotide sequences available in USEARCH version 7 and several of those available in USEARCH version 8, including searching (exact or based on global alignment), clustering by similarity (using length pre-sorting, abundance pre-sorting or a user-defined order), chimera detection (reference-based or de novo), dereplication (full length or prefix), pairwise alignment, reverse complementation, sorting, and subsampling. VSEARCH also includes commands for FASTQ file processing, i.e., format detection, filtering, read quality statistics, and merging of paired reads. Furthermore, VSEARCH extends functionality with several new commands and improvements, including shuffling, rereplication, masking of low-complexity sequences with the well-known DUST algorithm, a choice among different similarity definitions, and FASTQ file format conversion. VSEARCH is here shown to be more accurate than USEARCH when performing searching, clustering, chimera detection and subsampling, while on a par with USEARCH for paired-ends read merging. VSEARCH is slower than USEARCH when performing clustering and chimera detection, but significantly faster when performing paired-end reads merging and dereplication. VSEARCH is available at https://github.com/torognes/vsearch under either the BSD 2-clause license or the GNU General Public License version 3.0.
Discussion
VSEARCH has been shown to be a fast, accurate and full-fledged alternative to USEARCH. A free and open-source versatile tool for sequence analysis is now available to the metagenomics community.
Obesity is associated with low-grade chronic inflammation and intestinal dysbiosis. Ganoderma lucidum is a medicinal mushroom used in traditional Chinese medicine with putative anti-diabetic effects. Here, we show that a water extract of Ganoderma lucidum mycelium (WEGL) reduces body weight, inflammation and insulin resistance in mice fed a high-fat diet (HFD). Our data indicate that WEGL not only reverses HFD-induced gut dysbiosis-as indicated by the decreased Firmicutes-to-Bacteroidetes ratios and endotoxin-bearing Proteobacteria levels-but also maintains intestinal barrier integrity and reduces metabolic endotoxemia. The anti-obesity and microbiota-modulating effects are transmissible via horizontal faeces transfer from WEGL-treated mice to HFD-fed mice. We further show that high molecular weight polysaccharides (>300 kDa) isolated from the WEGL extract produce similar anti-obesity and microbiota-modulating effects. Our results indicate that G. lucidum and its high molecular weight polysaccharides may be used as prebiotic agents to prevent gut dysbiosis and obesity-related metabolic disorders in obese individuals.
The characterization of phylogenetic and functional diversity are key elements in the analysis of microbial communities. Amplicon-based sequencing of marker genes, such as 16S rRNA, is a powerful tool for assessing and comparing the structure of microbial communities at a high phylogenetic resolution. Because 16S rRNA sequencing is more cost-effective than whole metagenome shotgun sequencing, marker gene analysis is frequently used for broad studies that involve a large number of different samples. However, in comparison to shotgun sequencing approaches, insights into the functional capabilities of the community get lost when restricting the analysis to taxonomic assignment of 16S rRNA data.
Tax4Fun is a software package that predicts the functional capabilities of microbial communities based on 16S rRNA datasets. We evaluated Tax4Fun on a range of paired metagenome/16S rRNA datasets to assess its performance. Our results indicate that Tax4Fun provides a good approximation to functional profiles obtained from metagenomic shotgun sequencing approaches.
Tax4Fun is an open-source R package and applicable to output as obtained from the SILVAngs web server or the application of QIIME with a SILVA database extension. Tax4Fun is freely available for download at http://tax4fun.gobics.de/.
kasshau@gwdg.de.
© The Author(s) 2015. Published by Oxford University Press.
The main carriers of the pharmacological activity of garlic (Allium sativum L.) are organic sulfur compounds, the most important among them being allicin, a sulfenic acid thioester, or allylthiosulfonate. In this paper, the identification of synthesized and purified allicin was determined by using various spectroscopic methods (UV/VIS, FTIR, NMR). A HPLC method was developed for the detection and determination of the allicin content. The thermal degradation of allicin by using FTIR method was monitored. The method for the production of allicin gel based on Carbopol 940 (poly(acrylic acid)) was elaborated. The antimicrobial activity of pure allicin and allicin incorporated into gel by using a disk diffusion method was determined. In order to determine the antioxidant activity of allicin DPPH test was done and it was proved that with low concentrations (1 mgcm-3) a high DPPH radicals scavenging capacity (90%) was achieved.
A "leaky gut" may be the cutting edge for the passage of toxins, antigens or bacteria into the body, and may play a pathogenic role in advanced liver cirrhosis and its complications. Plasma endotoxin levels have been admitted as a surrogate marker of bacterial translocation and close relations of endotoxemia to hyperdynamic circulation, portal hypertension, renal, cardiac, pulmonary and coagulation disturbances have been reported. Bacterial overgrowth, increased intestinal permeability, failure to inactivate endotoxin, activated innate immunity are all likely to play a role in the pathological states of bacterial translocation. Therapeutic approach by management of the gut-liver axis by antibiotics, probiotics, synbiotics, prebiotics and their combinations may improve the clinical course of cirrhotic patients. Special concern should be paid on anti-endotoxin treatment. Adequate management of the gut-liver axis may be effective for prevention of liver cirrhosis itself by inhibiting the progression of fibrosis.
Subway systems are indispensable for urban societies, but microbiological characteristics of subway aerosols are relatively unknown. Previous studies investigating microbial compositions in subways employed methodologies that underestimated the diversity of microbial exposure for commuters, with little focus on factors governing subway air microbiology, which may have public health implications. Here, a culture-independent approach unraveling the bacterial diversity within the urban subway network in Hong Kong is presented. Aerosol samples from multiple subway lines and outdoor locations were collected. Targeting the 16S rRNA gene V4 region, extensive taxonomic diversity was found, with the most common bacterial genera in the subway environment among those associated with skin. Overall, subway lines harbored different phylogenetic communities based on α- and β-diversity comparisons, and closer inspection suggests that each community within a line is dependent on architectural characteristics, nearby outdoor microbiomes, and connectedness with other lines. Microbial diversities and assemblages also varied depending on the day sampled, as well as the time of day, and changes in microbial communities between peak and nonpeak commuting hours were attributed largely to increases in skin-associated genera in peak samples. Microbial diversities within the subway were influenced by temperature and relative humidity, while carbon dioxide levels showed a positive correlation with abundances of commuter-associated genera. This Hong Kong data set and communities from previous studies conducted in the United States formed distinct community clusters, indicating that additional work is required to unravel the mechanisms that shape subway microbiomes around the globe.
The aim of the present study was to identify bacteria that may contribute to the onset of metabolic dysfunctions. We isolated and identified a candidate bacterium belonging to Lachnospiraceae (strain AJ110941) in the feces of hyperglycemic obese mice. The colonization of germ-free ob/ob mice by AJ110941 induced significant increases in fasting blood glucose levels as well as liver and mesenteric adipose tissue weights, and decreases in plasma insulin levels and HOMA-β values. These results indicated that the specific gut commensal bacterium AJ110941 influenced the development of obesity and diabetes in ob/ob mice with genetic susceptibility for obesity.
Background
Increasing evidence suggest that the gut microbiota plays an important role in liver pathology after acute alcohol intake. The aim of our study was to investigate the roles played by commensal bacteria in alcohol-induced liver injury and in the dysbiosis caused by alcohol intake in germ-free mice, as well as the possibility of protection against alcohol-induced injuries in animals fed a high-fiber diet. For these purposes, germ-free and conventional mice were submitted to acute alcohol intake, consisting of administration of ethanol in their drinking water for 7 days, with a higher dose of alcohol administered on day 7.ResultsThere was no liver injury after alcohol consumption, and there was less neutrophil infiltration and lower pro-inflammatory cytokine levels (CXCL-1/KC and interleukin (IL)-6) in the liver in germ-free mice compared with alcohol-fed conventional mice. Additionally, conventionalization of germ-free mice with intestinal contents from alcohol-fed conventional mice induced injury and inflammation in both the liver and the intestine, suggesting that alcohol intake successively caused a perturbation of the intestinal microbiota (dysbiosis) and liver injury. Finally, previous treatment with a high-fiber diet decreased liver injury and gut permeability in alcohol-fed conventional mice.Conclusions
In conclusion, the results of the present study provide evidence that the gut microbiota plays an important role in alcohol-induced liver injury, apparently through dysbiosis of the intestinal microbial ecosystem caused by alcohol intake. Furthermore, treatment with a high-fiber diet can counteract hepatocyte pathology and gut leakage and thus could be a promising therapeutic option.
Enteric dysbiosis plays an essential role in the pathogenesis of alcoholic liver disease (ALD). Detailed characterization of the alterations in the gut microbiome is needed for understanding their pathogenic role in ALD and developing effective therapeutic approaches using probiotic supplementation. Mice were fed liquid Lieber-DeCarli diet without or with alcohol (5% v/v) for 6 weeks. A subset of mice were administered the probiotic Lactobacillus rhamnosus GG (LGG) from 6 to 8 weeks. Indicators of intestinal permeability, hepatic steatosis, inflammation and injury were evaluated. Metagenomic analysis of the gut microbiome was performed by analyzing the fecal DNA by amplification of the V3-V5 regions of the 16S rRNA gene and large-scale parallel pyrosequencing on the 454 FLX Titanium platform. Chronic ethanol feeding caused a decline in the abundance of both Bacteriodetes and Firmicutes phyla, with a proportional increase in the gram negative Proteobacteria and gram positive Actinobacteria phyla; the bacterial genera that showed the biggest expansion were the gram negative alkaline tolerant Alcaligenes and gram positive Corynebacterium. Commensurate with the qualitative and quantitative alterations in the microbiome, ethanol caused an increase in plasma endotoxin, fecal pH, hepatic inflammation and injury. Notably, the ethanol-induced pathogenic changes in the microbiome and the liver were prevented by LGG supplementation. Overall, significant alterations in the gut microbiome over time occur in response to chronic alcohol exposure and correspond to increases in intestinal barrier dysfunction and development of ALD. Moreover, the altered bacterial communities of the gut may serve as significant therapeutic target for the prevention/treatment of chronic alcohol intake induced intestinal barrier dysfunction and liver disease.
The gut flora plays an important role in the pathogenesis of the complications of cirrhosis. Hepatic encephalopathy (HE) represents a broad continuum of neuropsychological dysfunction in patients with acute or chronic liver disease and/or porto-systemic shunting of blood flow and it manifests with progressive deterioration of the superior neurological functions. The pathophysiology of this disease is complex, as it involves overproduction and reduced metabolism of various neurotoxins, particularly ammonia. Management of HE is diversified and requires several steps: elimination of precipitating factors, removal of toxins, proper nutritional support, modulation of resident fecal flora and downregulation of systemic and gut-derived inflammation. This review will provide an overview of gut barrier function and the influence of gut-derived factors on HE, focusing on the role of gut microbiota in the pathogenesis of HE and the recent literature findings on its therapeutic manipulation.
The microbial communities that colonize different regions of the human gut influence many aspects of health. In the healthy state, they contribute nutrients and energy to the host via the fermentation of nondigestible dietary components in the large intestine, and a balance is maintained with the host's metabolism and immune system. Negative consequences, however, can include acting as sources of inflammation and infection, involvement in gastrointestinal diseases, and possible contributions to diabetes mellitus and obesity. Major progress has been made in defining some of the dominant members of the microbial community in the healthy large intestine, and in identifying their roles in gut metabolism. Furthermore, it has become clear that diet can have a major influence on microbial community composition both in the short and long term, which should open up new possibilities for health manipulation via diet. Achieving better definition of those dominant commensal bacteria, community profiles and system characteristics that produce stable gut communities beneficial to health is important. The extent of interindividual variation in microbiota composition within the population has also become apparent, and probably influences individual responses to drug administration and dietary manipulation. This Review considers the complex interplay between the gut microbiota, diet and health.
Intestinal dysbiosis and bacterial translocation are common in patients with advanced liver disease, and there is strong evidence that the translocation of bacteria and their products across the epithelial barrier drives experimental liver disease progression. The aims of our study were to investigate dynamics of bacterial translocation and changes in the enteric microbiome in early stages of liver disease.
Cholestatic liver injury was induced by ligation of the common bile duct (BDL) and toxic liver injury by injection of carbon tetrachloride (CCl(4)) in mice.
Increased intestinal permeability and bacterial translocation occurred one day following liver injury in both disease models. This was accompanied by decreased intestinal expression of the tight junction protein occludin. Although BDL resulted in a rapid onset of intestinal bacterial overgrowth, bacterial overgrowth was observed in mice injected with CCl(4) only in advanced stages of liver fibrosis. To further assess the qualitative changes in the intestinal microbiome, massively parallel pyrosequencing of 16S rRNA genes revealed minor microbial changes following BDL, while CCl(4) administration resulted in a relative abundance of Firmicutes and Actinobacteria compared with oil-injected mice. Four different liver disease models (cholestasis, toxic, alcohol, obesity) show few similarities in their intestinal microbiome.
Acute liver injury is associated with an early onset of increased intestinal permeability and bacterial translocation that precede changes in the microbiome. The enteric microbiome differs with respect to the etiology of liver disease.
Non-alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of metabolic syndrome and the leading cause of chronic liver disease in the Western world. Twenty per cent of NAFLD individuals develop chronic hepatic inflammation (non-alcoholic steatohepatitis, NASH) associated with cirrhosis, portal hypertension and hepatocellular carcinoma, yet the causes of progression from NAFLD to NASH remain obscure. Here, we show that the NLRP6 and NLRP3 inflammasomes and the effector protein IL-18 negatively regulate NAFLD/NASH progression, as well as multiple aspects of metabolic syndrome via modulation of the gut microbiota. Different mouse models reveal that inflammasome-deficiency-associated changes in the configuration of the gut microbiota are associated with exacerbated hepatic steatosis and inflammation through influx of TLR4 and TLR9 agonists into the portal circulation, leading to enhanced hepatic tumour-necrosis factor (TNF)-α expression that drives NASH progression. Furthermore, co-housing of inflammasome-deficient mice with wild-type mice results in exacerbation of hepatic steatosis and obesity. Thus, altered interactions between the gut microbiota and the host, produced by defective NLRP3 and NLRP6 inflammasome sensing, may govern the rate of progression of multiple metabolic syndrome-associated abnormalities, highlighting the central role of the microbiota in the pathogenesis of heretofore seemingly unrelated systemic auto-inflammatory and metabolic disorders.
This study describes and validates a new method for metagenomic biomarker discovery by way of class comparison, tests of biological consistency and effect size estimation. This addresses the challenge of finding organisms, genes, or pathways that consistently explain the differences between two or more microbial communities, which is a central problem to the study of metagenomics. We extensively validate our method on several microbiomes and a convenient online interface for the method is provided at http://huttenhower.sph.harvard.edu/lefse/.
Unlabelled:
The translocation of bacteria and bacterial products into the circulation contributes to alcoholic liver disease. Intestinal bacterial overgrowth is common in patients with alcoholic liver disease. The aims of our study were to investigate bacterial translocation, changes in the enteric microbiome, and its regulation by mucosal antimicrobial proteins in alcoholic liver disease. We used a mouse model of continuous intragastric feeding of alcohol or an isocaloric diet. Bacterial translocation occurred prior to changes observed in the microbiome. Quantitative changes in the intestinal microflora of these animals were assessed first using conventional culture techniques in the small and large intestine. Although we found no difference after 1 day or 1 week, intestinal bacterial overgrowth was observed in the gastrointestinal tract of mice fed alcohol for 3 weeks compared with control mice fed an isocaloric liquid diet. Because <20% of all gastrointestinal bacteria can be cultured using conventional methodologies, we performed massively parallel pyrosequencing to further assess the qualitative changes in the intestinal microbiome following alcohol exposure. Sequencing of 16S ribosomal RNA genes revealed a relative abundance of Bacteroidetes and Verrucomicrobia bacteria in mice fed alcohol compared with a relative predominance of Firmicutes bacteria in control mice. With respect to the host's transcriptome, alcohol feeding was associated with down-regulation in gene and protein expression of bactericidal c-type lectins Reg3b and Reg3g in the small intestine. Treatment with prebiotics partially restored Reg3g protein levels, reduced bacterial overgrowth, and lessened alcoholic steatohepatitis.
Conclusion:
Alcohol feeding is associated with intestinal bacterial overgrowth and enteric dysbiosis. Intestinal antimicrobial molecules are dysregulated following chronic alcohol feeding contributing to changes in the enteric microbiome and to alcoholic steatohepatitis.
The pathogenesis of alcoholic liver injury involves interactions of several intracellular signalling pathways in different cell types of the liver. Alcohol-induced sensitization of liver macrophages to portal endotoxin/lipopolysaccharide (LPS) is considered a hallmark of alcoholic liver disease (ALD). Intracellular mechanisms associated with LPS-induced signalling play a crucial role in the initiation and progression of alcoholic liver injury, and are being extensively explored. LPS recognition by Toll-like receptor 4 (TLR4) on macrophages and other cell types in the liver, activation of downstream signalling pathways culminating in activation of transcription factors such as NFkappaB, AP-1 leads to increased inflammatory cytokine production in ALD. In addition, LPS-induced MAPK such as ERK and p38 also contribute to liver injury. The importance of alcohol-induced reactive oxygen species and interactions with TLR pathways in macrophages leading to inflammation is becoming increasingly evident. Collectively, these signalling pathways induce pro- and anti-inflammatory cytokines that play an important role in ALD. In this review we describe the key signalling intermediates leading to alcohol-induced inflammation in alcoholic liver disease.
Chronic Helicobacter pylori disease is reduced withAllium vegetable intake. This study was designed to assess the in vivo anti-H. pylori potential of a variety of garlic substances. The garlic materials all showed substantial but widely differing anti-H. pylori effects against all strains and isolates tested. The MICs (range, 8 to 32 μg/ml) and minimum bactericidal concentrations
(MBCs) (range, 16 to 32 μg/ml) of undiluted garlic oil (GO) were smaller than those of garlic powder (GP) (MIC range, 250
to 500 μg/ml; MBC range, 250 to 500 μg/ml) but greater than the MIC of allicin (4.0 μg/ml) (Table 2) present in GP. Allicin (MIC, 6 μg/ml; MBC, 6 μg/ml) was more potent than diallyl disulfide (MIC range, 100 to 200 μg/ml;
MBC range, 100 to 200 μg/ml), its corresponding sulfide, but of a strength similar to that of diallyl tetrasulfide (MIC range,
3 to 6 μg/ml; MBC range, 3 to 6 μg/ml). Antimicrobial activity of the diallyl sulfides increased with the number of sulfur
atoms. Time course viability studies and microscopy showed dose-dependent anti-H. pylori effects with undiluted GO, GP, allicin, and diallyl trisulfide after a lag phase of ca. 1 to 2 h. Substantial in vitro anti-H. pylori effects of pure GO and GP and their diallyl sulfur components exist, suggesting their potential for in vivo clinical use
against H. pylori infections.
In this study, we investigated the liver-protective effects of allicin, an active compound in fresh garlic, against alcoholic fatty liver disease (AFLD) and liver inflammation. Its effects were investigated in an AFLD model in male C57BL/6 mice, which were fed Lieber-DeCarli liquid diet containing ethanol. Allicin (5 and 20 mg/kg b.w./day) was orally administered daily in the AFLD mice for 4 weeks. Our results indicate that allicin promotes hepatoprotection by significantly reducing aspartate transaminase (AST) and alanine transaminase (ALT) levels (p < 0.05) in the plasma, which are key indicators of liver damage. Allicin reduced fat accumulation, increased glutathione and catalase levels, and decreased microsomal protein cytochrome P450 2E1 (CYP2E1) expression (p < 0.05) in the livers of the AFLD mice. Further, allicin supplementation significantly decreased proinflammatory tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6 levels, and suppressed the expression of sterol regulatory element-binding protein-1 (SREBP-1) (p < 0.05). Additionally, it improved hepatic alcohol dehydrogenase activity (p < 0.05). Collectively, these findings demonstrate that allicin attenuates liver oxidative stress and inflammation.
Trimethylamine N-oxide (TMAO) was recently discovered as a novel and independent risk factor for promoting atherosclerosis while it has been found to be generated from dietary carnitine through metabolism of gut microbiota for decades. Antibiotics were found to successfully inhibit the pathway of gut microbiota-dependent TMAO formation, as well as prevention of atherosclerosis. However, the side effects and resistance potential of antibiotics limit their potential application. Allicin is a well-established antimicrobial phytochemical naturally found in fresh blended garlic and easily acquired from diet. Here we demonstrated that the plasma TMAO levels in C57BL/6 mice fed with dietary carnitine were 4-22 times greater than that in the control chow diet group during carnitine challenge test. Interestingly, the differences of plasma TMAO level were not seen when comparing mice in carnitine plus allicin diet group with the control chow diet group. The results of this study suggest that dietary allicin may be capable of protecting the host from producing TMAO when carnitine is consumed through its impact on gut microbiota. Allicin and dietary fresh garlic containing allicin may be used as functional foods for the prevention of atherosclerosis.
Alcoholic liver disease (ALD) is a leading cause of morbidity and mortality worldwide. Alcoholic fatty liver disease can progress to steatohepatitis, alcoholic hepatitis, fibrosis, and cirrhosis. Patients with alcohol abuse show quantitative and qualitative changes in the composition of the intestinal microbiome. Furthermore, patients with ALD have increased intestinal permeability and elevated systemic levels of gut-derived microbial products. Maintaining eubiosis, stabilizing the mucosal gut barrier, or preventing cellular responses to microbial products protect from experimental ALD. Therefore, intestinal dysbiosis and pathological bacterial translocation appear fundamental for the pathogenesis of ALD. This review highlights causes for intestinal dysbiosis and pathological bacterial translocation, their relationship, and consequences for ALD. We also discuss how the liver affects the intestinal microbiota.
Copyright © 2015 by the Research Society on Alcoholism.
The causes of obesity, other than genes and environment, are poorly understood. A recent study showed that exposure of mice to antibiotics in early life induced lasting effects on body composition owing to alteration of the intestinal microbiota.
Host genetics and the gut microbiome can both influence metabolic phenotypes. However, whether host genetic variation shapes the gut microbiome and interacts with it to affect host phenotype is unclear. Here, we compared microbiotas across >1,000 fecal samples obtained from the TwinsUK population, including 416 twin pairs. We identified many microbial taxa whose abundances were influenced by host genetics. The most heritable taxon, the family Christensenellaceae, formed a co-occurrence network with other heritable Bacteria and with methanogenic Archaea. Furthermore, Christensenellaceae and its partners were enriched in individuals with low body mass index (BMI). An obese-associated microbiome was amended with Christensenella minuta, a cultured member of the Christensenellaceae, and transplanted to germ-free mice. C. minuta amendment reduced weight gain and altered the microbiome of recipient mice. Our findings indicate that host genetics influence the composition of the human gut microbiome and can do so in ways that impact host metabolism.
Acquisition of the intestinal microbiota begins at birth, and a stable microbial community develops from a succession of key organisms. Disruption of the microbiota during maturation by low-dose antibiotic exposure can alter host metabolism and adiposity. We now show that low-dose penicillin (LDP), delivered from birth, induces metabolic alterations and affects ileal expression of genes involved in immunity. LDP that is limited to early life transiently perturbs the microbiota, which is sufficient to induce sustained effects on body composition, indicating that microbiota interactions in infancy may be critical determinants of long-term host metabolic effects. In addition, LDP enhances the effect of high-fat diet induced obesity. The growth promotion phenotype is transferrable to germ-free hosts by LDP-selected microbiota, showing that the altered microbiota, not antibiotics per se, play a causal role. These studies characterize important variables in early-life microbe-host metabolic interaction and identify several taxa consistently linked with metabolic alterations. PAPERCLIP:
The gut microbiome is altered in cirrhosis; however its evolution with disease progression is partly understood. We aimed to study changes in microbiome over cirrhosis severity, its stability over time and its longitudinal alterations with decompensation.
Controls and age-matched cirrhotics (compensated/decompensated/hospitalized) were included. Their stool microbiota was quantified using multi-tagged pyrosequencing. Ratio of autochthonous to non-autochthonous taxa was calculated as the cirrhosis dysbiosis ratio(CDR); a low number indicating dysbiosis. Firstly, microbiome was compared between controls and cirrhotic sub-groups. Second, for stability assessment, stool collected twice within 6 months in compensated outpatients was analyzed. Thirdly, changes after decompensation were assessed using (a) longitudinal comparison in patients before/after hepatic encephalopathy development (HE), (b) longitudinal cohort of hospitalized infected cirrhotics MELD-matched to uninfected cirrhotics followed for 30 days.
244 subjects [219 cirrhotics (121 compensated outpatients,54 decompensated outpatients,44 inpatients) and 25 age-matched controls)] were included. CDR was highest in controls(2.05) than compensated(0.89), decompensated(0.66) and inpatients(0.32,p<0.0001) and negatively correlated with endotoxin. Microbiota and CDR remained unchanged in stable outpatient cirrhotics (0.91 vs. 0.86, p=0.45). In patients studied before/after HE development, dysbiosis occurred post-HE(CDR:1.2 to 0.42, p=0.03). In the longitudinal matched-cohort, microbiota were significantly different between infected/uninfected cirrhotics at baseline and a low CDR was associated with death and organ failures within 30 days.
Progressive changes in the gut microbiome accompany cirrhosis and become more severe in the setting of decompensation. The cirrhosis dysbiosis ratio may be a useful quantitative index to describe microbiome alterations accompanying cirrhosis progression.
Fatty liver is significantly associated with hepatic cirrhosis and liver cancer. Excessive alcohol consumption causes alcoholic fatty liver disease (AFLD). Ginger has been reported to exhibit antioxidant potential and hepatoprotective activity. In the present study, a mouse model for AFLD was developed by employing male C57BL/6 mice who were fed an alcohol-containing liquid diet (Lieber-DeCarli diet) ad libitum. In the treatment groups, ginger essential oil (GEO) and citral were orally administered every day for 4 weeks. Serum biochemical analysis, antioxidant enzyme activity analysis, and histopathological evaluation revealed that GEO and citral exhibited hepatoprotective activity against AFLD. Metabolites in serum samples were profiled by high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (HPLC-QTOF-MS). Metabolomic data indicated the amounts of metabolites such as D-glucurono-6,3-lactone, glycerol-3-phosphate, pyruvic acid, lithocholic acid, 2-pyrocatechuic acid, and prostaglandin E1 were increased after alcohol administration, but the levels were recovered in treatment groups. Our analysis indicated that ginger possesses hepatoprotective properties against AFLD. Further, these metabolites can serve as early non-invasive candidate biomarkers in the clinical application of AFLD for health management.
While a central role for the microbiota in the precipitation of infectious and non-infectious complications of liver disease has been long established, evidence for a more fundamental role in the etiology of several liver diseases continues to accumulate. However, though progress is rapidly occurring in this area, the definitive delineation of the precise relevance of changes in the microbiota to various forms and stages of liver disease is still far from complete. While high quality clinical evidence supports the use of antibiotic therapy, in the management of hepatic encephalopathy, spontaneous bacterial peritonitis and other infectious complications, how these interventions impact on the microbiota and microbiota-host interactions has not been clearly defined. Although probiotics and even, perhaps, fecal transplantation hold promise in the management of liver disease, and the potential impact of probiotics is supported by a considerable amount of laboratory data, high-quality clinical evidence is scanty.
Hepatocellular carcinoma is the most prevalent type of liver cancer globally and ranks first among the cancer-related mortalities in Taiwan. This study aims to understand the modes of cell death mechanism induced by allicin, a major phytochemical of crushed garlic, in human hepatoma cells. Our earlier study indicated allicin induced autophagic cell death in human hepatocellular carcinoma Hep G2 (p53wildtype) cells whereas in the present study allicin induced apoptotic cell death through caspase-dependent and -independent pathways by ROS over-production in human hepatocellular carcinoma Hep 3B (p53mutation) cells. To gain insight into the cell death mechanism in p53 knocked down Hep G2, we silenced p53 gene using siRNA mediated silencing. Allicin treatment induced apoptotic cell death in p53 knocked down Hep G2 cells similar to that of Hep 3B cells. These results suggest that allicin induced cell death in human hepatoma cells either through autophagy or apoptosis and might be a potential novel complementary gene therapeutic agent for the treatment of either autophagy or apoptosis resistant cancer cells.
Clinical and animal data indicate that gut-derived endotoxin and other luminal bacterial products are necessary cofactors for development of alcoholic liver disease (ALD). Although gut leakiness is clearly an important cause of endotoxemia in ALD, it cannot fully explain endotoxemia in all ALD subjects and thus other factors may be involved. One possible factor is a change in gut microbiota composition (dysbiosis). Thus, the aim of our study was to interrogate the gut bacterial microbiota in alcohol-fed rats to see if chronic alcohol consumption affects gut bacteria composition. Male Sprague-Dawley rats were given either alcohol or dextrose intragastrically by gavage twice daily for up to 10 weeks. A subgroup of rats was also given either a probiotic (lactobacillus GG) or a prebiotic (oats) by gavage. Ileal and colonic mucosal-attached microbiota composition were interrogated by Length Heterogeneity PCR (LH-PCR) fingerprinting. Results: Bacterial microbiota composition in alcohol-fed rats is not different from dextrose-fed rats at weeks 4 and 6. Mucosa-associated microbiota composition in the colon is altered at 10 weeks of daily alcohol gavage. Both LGG and oats prevented alcohol-induced dysbiosis up to 10 weeks of alcohol treatment. Daily alcohol consumption for 10 weeks alters colonic mucosa-associated bacterial microbiota composition in rats. Our data showed, for the first time, that daily alcohol consumption can affect colonic microbiome composition and suggest that dysbiosis may be an important mechanism of alcohol-induced endotoxemia. Further studies are needed to determine how dysbiotic microbiota contributes to development of ALD and whether therapeutic interventions targeted toward dysbiotic microbiota can prevent complications of alcoholism like ALD.
The human gastrointestinal tract harbors a complex and abundant microbial community that can reach levels as high as 10(13)-10(14) microorganisms in the colon. These microorganisms are essential to a host's well-being in terms of nutrition and mucosa immunity. However, numerous studies have also implicated members of the colonic microbiota in the development of colorectal cancer (CRC). While CRC involves a genetic component where damaged DNA and genetic instability initiates a malignant transformation, environmental factors can also contribute to the onset of CRC. Furthermore, considering the constant exposure of the colonic mucosa to the microbiome and/or its metabolites, the mucosa has long been proposed to contribute to colon tumorigenesis. However, the mechanistic details of these associations remain unknown. Fortunately, due to technical and conceptual advances, progress in characterizing the taxonomic composition, metabolic capacity, and immunomodulatory activity of human gut microbiota have been made, thereby elucidating its role in human health and disease. Furthermore, the use of experimental animal models and clinical/epidemiological studies of environmental etiological factors has identified a correlation between gut microbiota composition and gastrointestinal cancers. Bacteria continuously stimulate activated immunity in the gut mucosa and also contribute to the metabolism of bile and food components. However, the highest levels of carcinogen production are also associated with gut anaerobic bacteria and can be lowered with live lactobacilli supplements. In this review, evidence regarding the relationship between microbiota and the development of CRC will be discussed, as well as the role for microbial manipulation in affecting disease development.
Fatty liver induced by alcohol abuse is a major worldwide health hazard leading to morbidity and mortality. Previous studies indicate anti-fatty liver properties of garlic. In this study we have investigated the molecular mechanisms of garlic oil (GO) or diallyl disulfide (DADS) imparted hepatoprotection against alcohol induced fatty liver in C57BL/6 mice using microarray-based global gene expression analysis. Alcohol liquid diet resulted in severe fatty liver with increased levels of serum aspartate aminotransferease and alanine aminotransferease, triglycerides and decreased levels of liver glutathione and antioxidant enzymes. The major canonical pathways implicated by alcohol treatment are the metabolisms of xenobiotics by cytochrome P450, glutathione and arachidonic acid. Treatment with DADS or GO normalized the serum aminotransferease levels, liver antioxidant enzymes and reduced the contents of triglycerides and cholesterol. The canonical pathways involved in the amelioration of liver includes arachidonic acid metabolism, altered T cell and B cell signaling, tryptophan metabolism, and antigen presentation pathway for DADS; and metabolism of xenobiotics, mitotic roles of Polo-like kinase, fatty acid metabolism, LPS/IL-1 mediated inhibition of RXR function, and C21-steroid hormone metabolism for GO.
Garlic has been used throughout history for both culinary and medicinal purpose. Allicin is a major component of crushed garlic. Although it is sensitive to heat and light and easily metabolized into various compounds such as diallyl disulfide, diallyl trisulfide, and diallyl sulfide, allicin is still a major bioactive compound of crushed garlic. The mortality of hepatocellular carcinoma is quite high and ranks among the top 10 cancer-related deaths in Taiwan. Although numerous studies have shown the cancer-preventive properties of garlic and its components, there is no study on the effect of allicin on the growth of human liver cancer cells. In this study, we focused on allicin-induced autophagic cell death in human liver cancer Hep G2 cells. Our results indicated that allicin induced p53-mediated autophagy and inhibited the viability of human hepatocellular carcinoma cell lines. Using Western blotting, we observed that allicin decreased the level of cytoplasmic p53, the PI3K/mTOR signaling pathway, and the level of Bcl-2 and increased the expression of AMPK/TSC2 and Beclin-1 signaling pathways in Hep G2 cells. In addition, the colocalization of LC3-II with MitoTracker-Red (labeling mitochondria), resulting in allicin-induced degradation of mitochondria, could be observed by confocal laser microscopy. In conclusion, allicin of garlic shows great potential as a novel chemopreventive agent for the prevention of liver cancer.
The in vitro antibacterial activity of essential oils (EOs) obtained from fresh bulbs of garlic, Allium sativum L., and leek, Allium porrum L. ( Alliaceae), was studied. A. sativum (garlic) EO showed a good antimicrobial activity against Staphylococcus aureus (inhibition zone 14.8 mm), Pseudomonas aeruginosa (inhibition zone 21.1 mm), and Escherichia coli (inhibition zone 11.0 mm), whereas the EO of A. porrum (leek) had no antimicrobial activity. The main constituents of the garlic EO were diallyl monosulfide, diallyl disulfide (DADS), diallyl trisulfide, and diallyl tetrasulfide. The EO of A. porrum was characterized by the presence of dipropyl disulfide (DPDS), dipropyl trisulfide, and dipropyl tetrasulfide. The antimicrobial activities of the DADS and DPDS were also studied. The results obtained suggest that the presence of the allyl group is fundamental for the antimicrobial activity of these sulfide derivatives when they are present in Allium or in other species (DADS inhibition zone on S. aureus 15.9 mm, P. aeruginosa 21.9 mm, E. coli 11.4 mm). Copyright © 2012 John Wiley & Sons, Ltd.
Alcoholic liver disease (ALD) is a major cause of morbidity and mortality worldwide. The spectrum of disease ranges from fatty liver to hepatic inflammation, necrosis, progressive fibrosis and hepatocellular carcinoma. In developed countries, ALD is a major cause of end-stage liver disease that requires transplantation. The most effective therapy for ALD is alcohol abstinence. However, for patients with severe forms of ALD (that is, alcoholic hepatitis) and for those who do not achieve abstinence from alcohol, targeted therapies are urgently needed. The development of new drugs for ALD is hampered by the scarcity of studies and the drawbacks of existing animal models, which do not reflect all the features of the human disease. However, translational research using liver samples from patients with ALD has identified new potential therapeutic targets, such as CXC chemokines, osteopontin and tumor necrosis factor receptor superfamily member 12A. The pathogenetic roles of these targets, however, remain to be confirmed in animal models. This Review summarizes the epidemiology, natural history, risk factors and current knowledge of the pathogenetic mechanisms of ALD. In addition, this article provides a detailed description of the findings of these translational studies and of the animal models used to study ALD.
Inflammation is strongly associated with chronic hepatic injury and the ensuing wound-healing process. Recent evidence from mouse models and human studies implicates Toll-like receptors (TLRs) as important regulators of the inflammatory response and a functional link between inflammation and fibrosis in the chronically injured liver. Here, we review mechanisms by which TLR4 and TLR4 ligands from the intestinal microbiota contribute to hepatic injury, inflammation, hepatic stellate cell activation, and fibrosis.
The purpose of this study was to investigate the prevalence of hepatic steatosis in an asymptomatic U.S. adult population using attenuation values at unenhanced CT as the reference standard. We also assessed the utility of known clinical risk factors for diagnosis.
For 3,357 consecutive asymptomatic adults (1,865 women and 1,492 men; mean age, 57.0 years), hepatic and splenic CT attenuation values (Hounsfield units) were obtained by unenhanced CT using a low-dose colonography technique for colorectal cancer screening. Multiple attenuation criteria for steatosis were applied, including liver thresholds and comparison of liver and spleen attenuation. Relevant clinical risk factors were compared against a CT liver attenuation < or = 40 HU, which has been shown to exclude mild steatosis.
Mean liver attenuation was 58.8 +/- 10.8 (SD) HU. The prevalence of moderate-to-severe hepatic steatosis (defined by liver attenuation < or = 40 HU) was 6.2% (208/3,357). For CT attenuation criteria that include milder degrees of steatosis, prevalence increased to as high as 45.9% (1,542/3,357) for a liver-to-spleen attenuation ratio of < or = 1.1. Overweight status (body mass index > 25) was a sensitive indicator for moderate-to-severe steatosis (92.8%) but was highly nonspecific (37.5%). Other clinical risk factors, such as diabetes, dyslipidemia, hypertension, alcohol overuse, and hepatitis, were more specific (77.6-92.4%) but highly insensitive (1.9-37.5%). Combining clinical risk factors did not substantially increase the accuracy for screening.
Assessment of liver attenuation by use of unenhanced CT represents an objective and noninvasive means for detection of asymptomatic hepatic steatosis, whereas clinical risk factor assessment is unreliable. Further longitudinal investigation is needed to determine the most appropriate attenuation threshold and the risk for disease progression to steatohepatitis and cirrhosis.
During infections, pathogens bind to toll-like receptor (TLR)4 and CD14 receptors and induce cytokine release, leading to inflammation. Here, we investigated TLR4 and CD14 expression on peripheral blood leukocytes (PBLs) and their roles in lipopolysaccharide (LPS)-induced cytokine and chemokine release. Full-term and preterm neonates and adults were studied. PBLs were pretreated with anti-TLR4- and anti-CD14-blocking antibodies and stimulated with LPS. Cytokine and chemokine levels were measured in supernatants. TLR4, CD14 expression, and LPS-induced CXCL8 release were higher in neonates, possibly contributing to aberrant inflammation. TLR4 blockade resulted in approximately 3-fold greater suppression of LPS-induced CXCL8 release in preterm neonates (38%) than in adults (14%). CD14 blockade (approximately 80%) in neonates induced approximately 3-fold greater inhibition of CXCL8 release, compared with anti-TLR4 (approximately 30%). Anti-TLR4 partly (50-60%) inhibited IL-10 and TNF-alpha, whereas anti-CD14 completely suppressed their release. Our findings reveal that neonates depend more on TLR4 for CXCL8 release. Furthermore, neonatal LPS-induced CXCL8 release, apart from TLR4/CD14-mediated signaling, is regulated by LPS interactions with other TLRs and/or immune receptors. IL-10 and TNF-alpha release depends on LPS binding not only to CD14/TLR4 but also to CD14 associated with another TLR. Our findings reveal the contribution of TLR4 and CD14 in neonatal cytokine and chemokine release and could aid in design of antagonists to prevent harmful inflammation.
Not all alcoholics develop liver disease (ALD). Thus, excessive ethanol consumption is necessary, but not sufficient, to induce alcoholic steatohepatitis (ASH) and ALD. Since endotoxemia is present in patients with ALD, it has been proposed that gut-derived, circulating endotoxin is the necessary co-factor for ASH. But, it is not known whether endotoxemia is the consequence or the trigger for ALD. Accordingly, the aim of the current study was to determine whether endotoxemia occurs prior to development of ASH and whether gut leakiness is the primary cause of the endotoxemia in an animal model of ASH.
Time courses for development of gut hyperpermeability, nitric oxide production, oxidative injury to the gut, endotoxemia, and liver injury were assessed in rats during 10 weeks of daily alcohol gavage.
Liver fat and serum transaminase increased after 2 weeks, but evidence of liver cell injury and inflammation (ASH) occurred after 8 weeks. Gut leakiness, intestinal oxidative injury, and endotoxemia occurred in weeks 2-4 and progressed thereafter.
That alcohol-induced gut leakiness and endotoxemia preceded steatohepatitis indicates they are not the consequence of ALD. Our data support the hypothesis that gut leakiness resulting in endotoxemia is a key co-factor (trigger) for ASH.
The effects of chronic alcohol consumption on the bowel flora and the potential therapeutic role of probiotics in alcohol-induced liver injury have not previously been evaluated. In this study, 66 adult Russian males admitted to a psychiatric hospital with a diagnosis of alcoholic psychosis were enrolled in a prospective, randomized, clinical trial to study the effects of alcohol and probiotics on the bowel flora and alcohol-induced liver injury. Patients were randomized to receive 5 days of Bifidobacterium bifidum and Lactobacillus plantarum 8PA3 versus standard therapy alone (abstinence plus vitamins). Stool cultures and liver enzymes were performed at baseline and again after therapy. Results were compared between groups and with 24 healthy, matched controls who did not consume alcohol. Compared to healthy controls, alcoholic patients had significantly reduced numbers of bifidobacteria (6.3 vs. 7.5 log colony-forming unit [CFU]/g), lactobacilli (3.15 vs. 4.59 log CFU/g), and enterococci (4.43 vs. 5.5 log CFU/g). The mean baseline alanine aminotransferase (ALT), aspartate aminotransferase (AST), and gamma-glutamyl transpeptidase (GGT) activities were significantly elevated in the alcoholic group compared to the healthy control group (AST: 104.1 vs. 29.15 U/L; ALT: 50.49 vs. 22.96 U/L; GGT 161.5 vs. 51.88 U/L), indicating that these patients did have mild alcohol-induced liver injury. After 5 days of probiotic therapy, alcoholic patients had significantly increased numbers of both bifidobacteria (7.9 vs. 6.81 log CFU/g) and lactobacilli (4.2 vs. 3.2 log CFU/g) compared to the standard therapy arm. Despite similar values at study initiation, patients treated with probiotics had significantly lower AST and ALT activity at the end of treatment than those treated with standard therapy alone (AST: 54.67 vs. 76.43 U/L; ALT 36.69 vs. 51.26 U/L). In a subgroup of 26 subjects with well-characterized mild alcoholic hepatitis (defined as AST and ALT greater than 30 U/L with AST-to-ALT ratio greater than one), probiotic therapy was associated with a significant end of treatment reduction in ALT, AST, GGT, lactate dehydrogenase, and total bilirubin. In this subgroup, there was a significant end of treatment mean ALT reduction in the probiotic arm versus the standard therapy arm. In conclusion, patients with alcohol-induced liver injury have altered bowel flora compared to healthy controls. Short-term oral supplementation with B. bifidum and L. plantarum 8PA3 was associated with restoration of the bowel flora and greater improvement in alcohol-induced liver injury than standard therapy alone.
Allicin was effective in vitro against Candida, Cryptococcus, Trichophyton, Epidermophyton, and Microsporum. The minimal inhibitory concentrations (MICs) of allicin against these organisms were 3.13 to 6.25 μg/ml by the agar dilution
method and 1.57 to 6.25 μg/ml by the broth dilution method, using Sabouraud glucose (SG) medium. However decreased activity
was demonstrated against Aspergillus. The MIC of allicin against various pathogenic fungi was affected considerably by differences in the experimental conditions,
e.g., incubation time, inoculum size, type of medium, and medium pH. The MIC of allicin against Candida, Cryptococcus, and Aspergillus remained constant after more than 3 days of incubation, and that against Dermatophytes remained constant after more than 10 days of incubation. Decreasing the inoculum size increased the susceptibility to allicin.
The antifungal activity of allicin was stronger on SG agar medium with a pH of 5.6 than on the same medium with a pH of 6.0
or higher. By microscopical observation, allicin induced morphological abnormalities in hyphae of Trichophyton mentagrophytes Morita. Percent germination of spores of the Morita strain at 24 h in SG agar medium was greatly decreased with an allicin
concentration of 3.13 μg/ml, and the lethal dose for the spores was about four times higher than the fungistatic concentration.
These results suggest that allicin inhibits both germination of spores and growth of hyphae.
Techniques are reviewed for the experimental feeding of alcohol, including a liquid diet procedure invented 25 years ago. This technique results in much higher ethanol intake than with other approaches. As a consequence, various complications observed in alcoholics can be reproduced in animal models. These include fatty liver, hyperlipemia, various metabolic and endocrine disorders, tolerance to ethanol and other drugs, physical dependence and withdrawal and, in the baboon, liver fibrosis and cirrhosis. Variations of the liquid diet formulation are compared, and adequacy of nutrition in terms of minerals, vitamins, lipotropes, carbohydrates and proteins is discussed. The importance of selecting proper controls is emphasized. The respective advantages of three standardized basic rat formulas are reviewed: (i) an all-purpose (35% fat) diet, comparable to the diet previously referred to as the "Lieber-DeCarli formula" and suitable for most experimental applications, particularly those intended to mimic the clinical situation in which the various effects of alcohol occur in the setting of hepatic changes characterized by a fatty liver; (ii) a low-fat diet comparable in all respects to the preceding diet but with a lower fat content, intended to minimize the hepatic changes, and (iii) a high-protein formula particularly useful in those circumstances in which an oversupply of dietary protein might be recommended (i.e. pregnancy). Variations of this technique, including continuous intragastric infusion, are also discussed. It is concluded that, for most experimental studies of chronic alcohol consumption, the liquid diet technique provides one of the most efficient tools to study the effects of ethanol under controlled nutritional conditions because it allows for alcohol consumption of clinical relevance and offers flexibility to adjust to special experimental or physiologic needs by allowing for various substitutions required for a particular experimental design, including changes in lipids, proteins or other dietary constituents. The technique also facilitates the comparison with controls by simplifying the pair feeding and is the best procedure available for the study of the toxic effects of alcohol and their interactions with deficiency or excess of various nutrients.
Kupffer's cells participate in alcohol-induced liver injury, and endotoxemia is observed in human alcoholics and in a rat model. This study evaluated the effect of reducing bacterial endotoxin production by intestinal sterilization on alcohol-induced liver injury.
Male Wistar rats were exposed to ethanol continuously for up to 3 weeks via intragastric feeding. The gut was sterilized with polymyxin B and neomycin.
Fecal culture of stool samples from ethanol-fed rats treated with antibiotics showed virtually no growth of gram-negative bacteria. Endotoxin levels of 80-90 pg/mL in plasma of ethanol-fed rats were reduced to < 25 pg/mL by antibiotics. Antibiotic treatment also completely prevented elevated aspartate aminotransferase levels and significantly reduced the average hepatic pathological score in rats exposed to ethanol. Oxygen tension on the surface of the liver measured in vivo was decreased significantly from control values of 48 +/- 1 to 39 +/- 1 mumol/L in ethanol-treated rats. This hypoxia was prevented by treatment with antibiotics. Moreover, the increase in rates of ethanol elimination due to long-term ethanol treatment was prevented by antibiotic treatment.
Intestinal sterilization prevented alcohol-induced liver injury in the rat, supporting the idea that hypermetabolism and consequent hypoxia caused by activation of Kupffer's cells by endotoxin is involved in the mechanism.
Ajoene, a garlic-derived sulfur-containing compound that prevents platelet aggregation, exhibited broad-spectrum antimicrobial activity. Growth of gram-positive bacteria, such as Bacillus cereus, Bacillus subtilis, Mycobacterium smegmatis, and Streptomyces griseus, was inhibited at 5 micrograms of ajoene per ml. Staphylococcus aureus and Lactobacillus plantarum also were inhibited below 20 micrograms of ajoene per ml. For gram-negative bacteria, such as Escherichia coli, Klebsiella pneumoniae, and Xanthomonas maltophilia, MICs were between 100 and 160 micrograms/ml. Ajoene also inhibited yeast growth at concentrations below 20 micrograms/ml. The microbicidal effect of ajoene on growing cells was observed at slightly higher concentrations than the corresponding MICs. B. cereus and Saccharomyces cerevisiae were killed at 30 micrograms of ajoene per ml after 24 h of cultivation when cultivation was started at 10(5) cells per ml. However, the minimal microbicidal concentrations for resting cells were at 10 to 100 times higher concentrations than the corresponding MICs. The disulfide bond in ajoene appears to be necessary for the antimicrobial activity of ajoene, since reduction by cysteine, which reacts with disulfide bonds, abolished its antimicrobial activity.
Allicin, one of the active principles of freshly crushed garlic homogenates, has a variety of antimicrobial activities. Allicin in its pure form was found to exhibit i) antibacterial activity against a wide range of Gram-negative and Gram-positive bacteria, including multidrug-resistant enterotoxicogenic strains of Escherichia coli; ii) antifungal activity, particularly against Candida albicans; iii) antiparasitic activity, including some major human intestinal protozoan parasites such as Entamoeba histolytica and Giardia lamblia; and iv) antiviral activity. The main antimicrobial effect of allicin is due to its chemical reaction with thiol groups of various enzymes, e.g. alcohol dehydrogenase, thioredoxin reductase, and RNA polymerase, which can affect essential metabolism of cysteine proteinase activity involved in the virulence of E. histolytica.
Increased gut permeability (leaky gut) and endotoxin-mediated Kupffer cell activation are proposed as the mechanisms of alcoholic liver injury. Although ethanol feeding is shown to sensitize the liver for injury induced by parental administration of lipopolysaccharide (LPS), how enteral LPS loading affects alcoholic liver injury is yet to be tested. The present study provides direct evidence for enhanced entrance to portal circulation of LPS enterally administered to the intragastric ethanol infusion model. Portal and systemic blood endotoxin levels increased to 43.0 +/- 4.1 and 6.2 +/- 4.3 pg/mL at 2 hours following enteral LPS administration (5 mg/kg) in alcohol-fed animals, while no such increases were observed in pair-fed controls. However, endotoxin levels in systemic blood of alcohol-fed rats were reduced to 0 to 1. 5 pg/mL 16 hours after LPS administration. Weekly enteral administration of LPS to the model for 9 weeks exacerbated an increase in plasma alanine transaminase (ALT) levels (227 +/- 75 vs. 140 +/- 70; P <.01), mononuclear infiltration (25 +/- 22 vs. 6.4 +/- 4.4/10 mm(2); P =.02), sinusoidal congestion, and spotty necrosis, and induced diffuse coagulative necrosis and centrilobular fibrosis in some animals. Reverse-transcription polymerase chain reaction (RT-PCR) analysis confirmed the LPS effect at the tissue level by demonstrating accentuated induction of tumor necrosis factor alpha (TNF-alpha) and Cox-2 mRNA. In conclusion, enteral LPS administration potentiates alcoholic liver necrosis, inflammation, and fibrosis despite efficient endotoxin clearance by the liver and mild systemic endotoxemia that occurs episodically following enteral LPS challenge.