Ethanol and dietary unsaturated fat (corn oil/linoleic acid enriched) cause intestinal inflammation and impaired intestinal barrier defense in mice chronically fed alcohol
Introduction
The concept that alcohol and dietary fat both play an important interactive role in the development of alcoholic liver disease (ALD) is well documented (Nanji, 2004; Nanji & French, 1986). The majority of the evidence from rodent models supports both a protective effect of dietary saturated fatty acids against ALD, and a deleterious effects of dietary unsaturated fatty acids, linoleic acid (LA) in particular, in alcohol-mediated liver damage (Kono et al., 2000; Nanji & French, 1989; Nanji, Jokelainen, Tipoe, Rahemtulla, & Dannenberg, 2001; Nanji, Mendenhall, & French, 1989; Nanji, Yang, Fogt, Sadrzadeh, & Dannenberg, 1996; Ronis, Korourian, Zipperman, Hakkak, & Badger, 2004). Moreover, Nanji and French (1989) have shown that LA is required for the development of experimental ALD. However, the underlying molecular mechanisms are not fully elucidated. Hence, the role of fat composition in the development and progression of ALD remains an area of considerable interest.
The importance of the gut–liver axis in alcohol-mediated liver pathology has received increasing interest (Purohit et al., 2008; Szabo & Bala, 2010; Wang, Zakhari, & Jung, 2010). Clinical and experimental data have demonstrated that gut-derived endotoxin, lipopolysaccharide (LPS), plays an important role in the pathogenesis of ALD (Bode, Kugler, & Bode, 1987; Fukui, Brauner, Bode, & Bode, 1991; Keshavarzian et al., 2009; Mathurin et al., 2000; Parlesak, Schafer, Schutz, Bode, & Bode, 2000; Szabo & Bala, 2010; Tang et al., 2009). Multiple mechanisms contribute to alcohol-associated endotoxemia, including alcohol-mediated intestinal bacterial overgrowth (Bode, Kolepke, Schafer, & Bode, 1993), alterations in gut microbiota (Mutlu et al., 2009, 2012; Yan et al., 2011), as well as increased LPS translocation caused by the disruption of intestinal barrier integrity (Banan, Choudhary, Zhang, Fields, & Keshavarzian, 1999; Ma, Nguyen, Bui, Nguyen, & Hoa, 1999; Tang et al., 2008; Zhong, McClain, Cave, Kang, & Zhou, 2010).
The most recent studies from our group demonstrated that EtOH disrupts intestinal tight junctions in the ileal mucosa, followed by increased intestinal permeability, elevated blood LPS levels and consequent liver steatosis and injury (Kirpich et al., 2012; Zhong et al., 2010). Understanding the effects of EtOH, dietary fat, and their potential interactions on the intestine is critical in determining the mechanisms of alcohol-mediated multi-organ pathology. The intestine is an important component of the immune systems, and an initial organ exposed to alcohol and ingested nutrients; however, little is known about the potential effects of alcohol in combination with different dietary factors on the intestinal inflammatory response and its associations with intestinal barrier integrity.
In the present study, we used a mouse model of chronic EtOH feeding to evaluate the effects of dietary saturated and unsaturated fat on the gut pathology associated with chronic alcohol consumption. We hypothesized that dietary unsaturated fat (corn oil/linoleic acid enriched) is a cofactor in ethanol-mediated intestinal inflammatory stress and mucus layer alterations. Mice were fed liquid Lieber-DeCarli EtOH diet ad libitum for 8 weeks with two different sources of fat. Unsaturated fat (USF) diet was enriched in corn oil/linoleic acid (LA), and saturated fat (SF) was mainly comprised of medium chain triglycerides (MCT). Our findings revealed that alcohol and dietary USF triggered an intestinal pro-inflammatory response characterized by increased Tnf-α, MCP-1, and MPO activity. Further, alcohol and dietary USF, but not SF, resulted in alterations of the intestinal mucus layer and antimicrobial defense, characterized by decreased expression of Muc2 and Cramp in the ileum. Overall, these findings contribute to the understanding of the deleterious effects of dietary unsaturated fatty acids, LA in particular, in EtOH-mediated intestinal pathology.
Section snippets
Experimental animal model
C57BL/6N male mice obtained from Harlan (Indianapolis, IN) were fed a modified Lieber-DeCarli liquid diet enriched in USF (corn oil/LA) or SF (an 18:82 ratio beef tallow:MCT (Ronis et al., 2004)). The diets were purchased from the Research Diet, New Brunswick, NJ. Mice were fed control or EtOH-containing diets ad libitum for 8 weeks. Control mice were pair-fed SF or USF maltose-dextrin diets that were isocaloric with the EtOH diets. In the control group diets, the levels of protein,
Effects of alcohol and saturated and unsaturated fat diets on body weight and blood alcohol levels
The experimental animals were pair-fed liquid diets enriched in saturated fat (SF) or unsaturated fat (USF) with or without EtOH for 8 weeks. Mice fed USF + EtOH diet gained more body weight compared to mice fed SF + EtOH diet during the first 2 weeks of the experiment (15.2 + 1.7 g vs. 6.06 + 1.6 g, p < 0.05). A noticeable gradual reduction of body weight was observed in both SF + EtOH and USF + EtOH groups starting in the second month of the feeding period. There were no differences in final
Discussion
There are several known injurious effects of alcohol consumption on the gut, including alcohol induced gut permeability (Parlesak et al., 2000; Purohit et al., 2008; Rao, Seth, & Sheth, 2004), impairment of the intestinal microcirculation, macro and micronutrient malabsorption, and altered gut motility (reviewed in (Bode & Bode, 2003; Rajendram & Preedy, 2005). However, little is known about the combined effects of EtOH and dietary fat on the intestinal inflammatory response, as well as on
Funding
The work presented in this study was supported by NIH grants R21 AA020849-01A1 (IK), P01 AA017103 (CJM), R01 AA0015970 (CJM), R01 AA018016 (CJM, SB), R01 DK071765 (CJM), R37 AA010762 (CJM), R01 AA018869 (CJM), P30 AA019360 (CJM), RC2AA019385 (CJM), and the Department of Veterans Affairs (CJM).
Acknowledgments
The authors thank Hanan Farghaly, MD for help in the intestinal histological evaluation; David Barker, PhD for the qPCR primer design; and Marion McClain for manuscript proofreading.
References (60)
- et al.
Dose-dependent effect of ethanol and E. coli on gut permeability and cytokine production
Journal of Surgical Research
(2009) - et al.
Effect of alcohol consumption on the gut
Best Practice & Research Clinical Gastroenterology
(2003) - et al.
Endotoxemia in patients with alcoholic and non-alcoholic cirrhosis and in subjects with no evidence of chronic liver disease following acute alcohol excess
Journal of Hepatology
(1987) - et al.
Plasma endotoxin concentrations in patients with alcoholic and non-alcoholic liver disease: reevaluation with an improved chromogenic assay
Journal of Hepatology
(1991) - et al.
Evidence that chronic alcohol exposure promotes intestinal oxidative stress, intestinal hyperpermeability and endotoxemia prior to development of alcoholic steatohepatitis in rats
Journal of Hepatology
(2009) - et al.
Probiotics restore bowel flora and improve liver enzymes in human alcohol-induced liver injury: a pilot study
Alcohol
(2008) - et al.
Host-mediated inflammation disrupts the intestinal microbiota and promotes the overgrowth of Enterobacteriaceae
Cell Host & Microbe
(2007) - et al.
Exacerbation of alcoholic liver injury by enteral endotoxin in rats
Hepatology
(2000) Role of different dietary fatty acids in the pathogenesis of experimental alcoholic liver disease
Alcohol
(2004)- et al.
Dietary linoleic acid is required for development of experimentally induced alcoholic liver injury
Life Sciences
(1989)
Increased intestinal permeability to macromolecules and endotoxemia in patients with chronic alcohol abuse in different stages of alcohol-induced liver disease
Journal of Hepatology
Alcohol, intestinal bacterial growth, intestinal permeability to endotoxin, and medical consequences: summary of a symposium
Alcohol
Dietary saturated fat reduces alcoholic hepatotoxicity in rats by altering fatty acid metabolism and membrane composition
Journal of Nutrition
Interleukin-6 (IL-6) regulates claudin-2 expression and tight junction permeability in intestinal epithelium
The Journal of Biological Chemistry
Muc2-deficient mice spontaneously develop colitis, indicating that MUC2 is critical for colonic protection
Gastroenterology
Interferon-gamma and tumor necrosis factor-alpha synergize to induce intestinal epithelial barrier dysfunction by up-regulating myosin light chain kinase expression
The American Journal of Pathology
Chronic alcohol exposure increases circulating bioactive oxidized phospholipids
The Journal of Biological Chemistry
Mechanism of interleukin-1beta induced-increase in mouse intestinal permeability in vivo
Journal of Interferon & Cytokine Research
Linoleic acid induces interleukin-8 production by Crohn's human intestinal smooth muscle cells via arachidonic acid metabolites
American Journal of Physiology & Gastrointestinal Liver Physiology
Alcohol-induced gastritis prevents oral tolerance induction in mice
Clinical & Experimental Immunology
Ethanol-induced barrier dysfunction and its prevention by growth factors in human intestinal monolayers: evidence for oxidative and cytoskeletal mechanisms
Journal of Pharmacology & Experimental Therapeutics
Breath hydrogen excretion in patients with alcoholic liver disease–evidence of small intestinal bacterial overgrowth
Zeitschrift fur Gastroenterologie
Metagenomic Analyses of Alcohol Induced Pathogenic Alterations in the Intestinal Microbiome and the Effect of Lactobacillus rhamnosus GG Treatment
PLoS One
Metabolic endotoxemia initiates obesity and insulin resistance
Diabetes
Induction of arachidonate 12-lipoxygenase (Alox15) in intestine of iron-deficient rats correlates with the production of biologically active lipid mediators
American Journal of Physiology & Gastrointestinal Liver Physiology
Burns, inflammation, and intestinal injury: protective effects of an anti-inflammatory resuscitation strategy
The Journal of Trauma
Effects of glutamine on intestinal permeability and bacterial translocation in TPN-rats with endotoxemia
World Journal of Gastroenterology
Pro- and anti-inflammatory gene expression in the murine small intestine and liver after chronic exposure to alcohol
Alcoholism: Clinical & Experimental Research
Epithelial barrier: an interface for the cross-communication between gut flora and immune system
Immunological Reviews
Aberrant mucin assembly in mice causes endoplasmic reticulum stress and spontaneous inflammation resembling ulcerative colitis
PLoS Medicine
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2019, Liver ResearchCitation Excerpt :The evidence from preclinical animal studies underscores the importance of different types of dietary fat in EtOH-associated alterations in the gut-liver axis. Compared to a diet enriched in saturated MCFAs, a diet high in the n-6 PUFA, LA, exacerbated EtOH-induced intestinal inflammation, permeability, and endotoxemia associated with liver injury in mice.81,106 A growing body of studies suggests that dietary FAs influence the gut microbiota composition, which, in turn, may affect host metabolic health.107–109