Fish Oils Increase Intestinal Permeability

Also see:
PUFA and Liver Toxicity; Protection by Saturated Fats
Endotoxin: Poisoning from the Inside Out
Ray Peat, PhD on the Benefits of the Raw Carrot
Protection from Endotoxin
Endotoxin-lipoprotein Hypothesis
Protective Bamboo Shoots
The effect of raw carrot on serum lipids and colon function
How does estrogen enhance endotoxin toxicity? Let me count the ways.
Bowel Toxins Accelerate Aging
Liver saving saturated fats

“Besides causing a general slowing of metabolism, aging and toxic PUFA have specific actions on the detoxifying system. The enzymes that help to detoxify PUFA and estrogen and serotonin are inhibited by both PUFA and estrogen. All systems, including blood vessels and the intestine, are made leaky by estrogen and the PUFA and their products.” -Ray Peat, PhD

“In the bowel, the capillary malfunction increases the absorption of endotoxin, which intensifies the systemic energy problem. (Polyunsaturated oils, especially fish oil, damage the bowel capillaries, allowing more endotoxin to be absorbed.)” -Ray Peat, PhD

J Nutr. 2011 Sep;141(9):1635-42. Epub 2011 Jul 20.
Ingestion of (n-3) fatty acids augments basal and platelet activating factor-induced permeability to dextran in the rat mesenteric vascular bed.
Dombrowsky H, Lautenschläger I, Zehethofer N, Lindner B, Schultz H, Uhlig S, Frerichs I, Weiler N.
Loss of intestinal barrier function and subsequent edema formation remains a serious clinical problem leading to hypoperfusion, anastomotic leakage, bacterial translocation, and inflammatory mediator liberation. The inflammatory mediator platelet activating factor (PAF) promotes eicosanoid-mediated edema formation and vasoconstriction. Fish oil-derived (n-3) fatty acids (FA) favor the production of less injurious eicosanoids but may also increase intestinal paracellular permeability. We hypothesized that dietary (n-3) FA would ameliorate PAF-induced vasoconstriction and enhance vascular leakage of dextran tracers. Rats were fed either an (n-3) FA-rich diet (EPA-rich diet; 4.0 g/kg EPA, 2.8 g/kg DHA) or a control diet (CON diet; 0.0 g/kg EPA and DHA) for 3 wk. Subsequently, isolated and perfused small intestines were stimulated with PAF and arterial pressure and the translocation of fluid and macromolecules from the vasculature to lumen and lymphatics were analyzed. In intestines of rats fed the EPA-rich diet, intestinal phospholipids contained up to 470% more EPA and DHA at the expense of arachidonic acid (AA). The PAF-induced increase in arterial pressure was not affected by the EPA-rich diet. However, PAF-induced fluid loss from the vascular perfusate was higher in intestines of rats fed the EPA-rich diet. This was accompanied by a greater basal loss of dextran from the vascular perfusate and a higher PAF-induced transfer of dextran from the vasculature to the lumen (P = 0.058) and lymphatics. Our data suggest that augmented intestinal barrier permeability to fluid and macromolecules is a possible side effect of (n-3) FA-rich diet supplementation.

DHA increases the leakiness of the bowel, allowing more endotoxin to enter the circulation (RoigPerez, et al., 2004). -Ray Peat, PhD

J Lipid Res. 2004 Aug;45(8):1418-28. Epub 2004 Jun 1.
Lipid peroxidation induced by DHA enrichment modifies paracellular permeability in Caco-2 cells: protective role of taurine.
Roig-Pérez S, Guardiola F, Moretó M, Ferrer R.
Dietary enrichment with docosahexaenoic acid (DHA) has numerous beneficial effects on health. However, the intake of high doses of polyunsaturated fatty acids can promote lipid peroxidation and the subsequent propagation of oxygen radicals. The purpose of this study was to evaluate the effect of DHA on lipid peroxidation and tight junction structure and permeability in Caco-2 cell cultures. Moreover, the effects of taurine, a functional ingredient with antioxidant properties, were also tested. Differentiated Caco-2 cell monolayers were maintained in DHA-supplemented conditions with or without added taurine. Incubation with 100 microM DHA increased lipid peroxidation and paracellular permeability, in parallel with a redistribution of the tight junction proteins occludin and ZO-1. Taurine partially prevented all of these effects. The participation of reactive oxygen and nitrogen species in increased paracellular permeability was also examined using various agents that modify the formation of superoxide radical, hydrogen peroxide, nitric oxide, and peroxynitrite. We conclude that hydrogen peroxide and peroxynitrite may be involved in the DHA-induced increase in paracellular permeability and that the protective role of taurine may be in part related to its capacity to counteract the effects of hydrogen peroxide.

Implications:
J Clin Gastroenterol. 2002 Apr;34(4):385-96.
Intestinal permeation and gastrointestinal disease.
DeMeo MT, Mutlu EA, Keshavarzian A, Tobin MC.
The gastrointestinal tract constitutes one of the largest sites of exposure to the outside environment. The function of the gastrointestinal tract in monitoring and sealing the host interior from intruders is called the gut barrier. A variety of specific and nonspecific mechanisms are in operation to establish the host barrier; these include luminal mechanisms and digestive enzymes, the epithelial cells together with tight junctions in between them, and the gut immune system. Disruptions in the gut barrier follow injury from various causes including nonsteroidal anti-inflammatory drugs and oxidant stress, and involve mechanisms such as adenosine triphosphate depletion and damage to epithelial cell cytoskeletons that regulate tight junctions. Ample evidence links gut barrier dysfunction to multiorgan system failure in sepsis and immune dysregulation. Additionally, contribution of gut barrier dysfunction to gastrointestinal disease is an evolving concept and is the focus of this review. An overview of the evidence for the role of gut barrier dysfunction in disorders such as Crohn’s disease, celiac disease, food allergy, acute pancreatitis, non-alcoholic fatty liver disease, and alcoholic liver disease is provided, together with critical insight into the implications of this evidence as a primary disease mechanism.

“Essential” polyunsaturated fat linoleic acid also increase intestinal permeability. Saturated fats had no such effect.
Alcohol Clin Exp Res. 2012 May;36(5):835-46. doi: 10.1111/j.1530-0277.2011.01673.x. Epub 2011 Dec 7.
The type of dietary fat modulates intestinal tight junction integrity, gut permeability, and hepatic toll-like receptor expression in a mouse model of alcoholic liver disease.
Kirpich IA, Feng W, Wang Y, Liu Y, Barker DF, Barve SS, McClain CJ.
BACKGROUND:
Interactions between the gut, immune system, and the liver, as well as the type of fat in the diet, are critical components of alcoholic liver disease (ALD). The goal of the present study was to determine the effects of saturated fat (SF) and unsaturated fat (USF) on ethanol (EtOH)-induced gut-liver interactions in a mouse model of ALD.
METHODS:
C57BL/6N mice were fed Lieber-DeCarli liquid diets containing EtOH and enriched in USF (corn oil) or SF (medium chain triglycerides:beef tallow). Control mice were pair-fed on an isocaloric basis. Liver injury and steatosis, blood endotoxin levels, intestinal permeability, and tight junction (TJ) integrity, as well as hepatic Toll-like receptor (TLR) gene expression, were evaluated.
RESULTS:
After 8 weeks of EtOH feeding, liver injury and steatosis were observed in USF + EtOH group compared with control and SF + EtOH. Significantly increased intestinal permeability in conjunction with elevated blood endotoxin levels were observed in the ileal segments of the mice fed USF + EtOH. USF diet alone resulted in down-regulation of intestinal TJ protein mRNA expression compared with SF. Importantly, alcohol further suppressed TJ proteins in USF + EtOH, but did not affect intestinal TJ in SF + EtOH group. The type of fat in the diet alone did not affect hepatic TLR expression. Compared with control animals, hepatic TLR (TLR 1, 2, 3, 4, 7, 8, 9) mRNA expression was significantly (p < 0.05) increased in USF + EtOH, but not in SF + EtOH group. Notably, TLR5 was the only up-regulated TLR in both SF + EtOH and USF + EtOH groups. CONCLUSIONS: Dietary fat is an important cofactor in alcohol-associated liver injury. We demonstrate that USF (corn oil/linoleic acid) by itself results in dysregulation of intestinal TJ integrity leading to increased gut permeability, and alcohol further exacerbates these alterations. We postulate that elevated blood endotoxin levels in response to USF and alcohol in conjunction with up-regulation of hepatic TLRs combine to cause hepatic injury in ALD.