Saturated Fatty Acids Do Not Stimulate Toll-Like Receptors

[Kartoffel]

Recently, there has been a lot of talk about saturated fat and the toll-like receptor proteins that are involved in immune reactions and the inflammatory cascade that follows their activation. People here on the forum and elsewhere have repeatedly cited several in vitro studies supposedly showing that saturated fatty acids serve as ligands for TLR2 and TLR4 (the one that is mostly activated by endotoxin). The story is that saturated fatty acids like palmitic, lauric, or stearic acid bind directly with the TLRs and are therefore inherently pro-inflammatory.
That would, in fact, be bad, if it were so. Luckily, these studies are, like so many, just more artefacts of scientific incompetence. As this paper shows, the saturated fatty acids do not stimulate TLR activation, even in massive quantities. As it turns out, the studies demonstrating TLR activation by saturated fatty acids used a reagent to complex with the fatty acids for use that was contaminated with significant quantities of LPS and bacterial lipopeptides. Both are known to act as ligands for TLR4 and induce inflammation.
The saturated fatty acids alone did not activate TLRs, at all, while bovine serum albumin (the reagent they used) activated the inflammatory response attributed to saturated fat. I'm not sure, if someone mentioned this study before, but since the claims about SFA and TLRs continue to pop up here, it thought it might be worth a thread.

Arterioscler Thromb Vasc Biol. 2009 Nov;29(11):1944-9.
Saturated fatty acids do not directly stimulate Toll-like receptor signaling.
Erridge C1, Samani NJ.

"Instead, we present evidence that fatty-acid–free BSA, the reagent used in previous studies to present SFAs to cells in a physiological form, can be contaminated with both LPS and lipopeptide, and therefore likely accounts for the results of these previous studies."​

"In a screen of a wide variety of cell types, including macrophages, adipocytes, smooth muscle cells, and endothelial cells, we found that SFAs did not induce expression of gene products that are typically upregulated by TLR-stimulation, such as IL-1 ,TNF-a ,CCL-2,andE-selectin. SFAs also did not promote the phosphorylation of p38 MAPK or degradation of which are established to be universal featuresof TLR-stimulation in macrophages. Finally, in transfected HEK-293 cells, which are sensitive to very low concentrations of respective TLR-ligands, SFAs, even at supraphysiological levels, neither induced nor enhanced TLR2 or TLR4 signaling"
​

The graph below shows the expression of TLR2, TLR4, and TLR4 after contact with SFA complexed with BSA (A-C), and without it (D-F)

​

They further demonstrated that BSA alone strongly stimulated TLR4 and inflammatory cytokines like TNF-a. The effect was even more pronounced than for endotoxin alone.

 

[schultz]

Good stuff. Very interesting about the BSA.

 

[yerrag]

Thanks. Now I can go back to drinking regular milk as skim milk just doesn't taste good. My cat was telling me so, but I wasn't listening. He just turns his nose away, and then looks at me with a look that says "Why?"

 

[Andman]

Thank you, this matches my n=1 experience quite well. Unfortunately the main proponent of the sat fat = lps/bacterial translocation seems to have ragequit the forum

 

[LeeLemonoil]

I see it as a positive of this forum.

It reflects how easily false narratives gain traction and become „common knowledge“ - in science in this forums case.
And we have enough users here who are critical and „perceive, think, act“ to rectify claims where necessary.

It’s a good exercise in keeping your mind and wir agile and sceptic.
Look at the „poison A“ stuff, discussions about Niacinamide, iodide, Palmitic acids... lots of controversy here, bring it on!

 

[Mufasa]

@Vinero

 

[nwo2012]

Poor Captain Rapeseed got @#$%ed.

 

[Broken man]

Haidut posted it few months ago

 

[RWilly]

A saturated fatty acid-rich diet induces an obesity-linked proinflammatory gene expression profile in adipose tissue of subjects at risk of metabol... - PubMed - NCBI

"Consumption of the SFA diet resulted in increased expression of genes involved in inflammation processes in adipose tissue, without changes in morphology or insulin sensitivity. The MUFA diet led to a more antiinflammatory gene expression profile, which was accompanied by a decrease in serum LDL-cholesterol concentrations and an increase in plasma and adipose tissue oleic acid content.

CONCLUSIONS:
Consumption of an SFA diet resulted in a proinflammatory "obesity-linked" gene expression profile, whereas consumption of a MUFA diet caused a more antiinflammatory profile. This suggests that replacement of dietary SFA with MUFA could prevent adipose tissue inflammation and may reduce the risk of inflammation-related diseases such as metabolic syndrome. "



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Palmitate, but Not Unsaturated Fatty Acids, Induces the Expression of Interleukin-6 in Human Myotubes through Proteasome-dependent Activation of Nuclear Factor-κB

"In conclusion, our data provide clear evidence that skeletal muscle cells produce considerable amounts of IL-6 in response to increasing saturated FFA concentrations."

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Postprandial serum endotoxin in healthy humans is modulated by dietary fat in a randomized, controlled, cross-over study. - PubMed - NCBI

"Healthy adults (n = 20; mean age 25 ± 3.2 S.D. years) were enrolled in this single-blind, randomized, cross-over study. Participants were randomized to treatment and reported to the laboratory, after an overnight fast, on four occasions separated by at least one week. Participants were blinded to treatment meal and consumed one of four isoenergetic meals that provided: 1) 20 % fat (control; olive oil) or 35 % fat provided from 2) n-3 (ω3) (DHA = 500 mg; fish oil); 3) n-6 (ω6) (7.4 g; grapeseed oil) or 4) saturated fat (16 g; coconut oil). Baseline and postprandial blood samples were collected. Primary outcome was defined as the effect of treatment meal on postprandial endotoxemia. Serum was analyzed for metabolites, inflammatory markers, and endotoxin. Data from all 20 participants were analyzed using repeated-measures ANCOVA.

RESULTS:
Participant serum endotoxin concentration was increased during the postprandial period after the consumption of the saturated fat meal but decreased after the n-3 meal (p < 0.05). The n-6 meal did not effect a different outcome in participant postprandial serum endotoxin concentration from that of the control meal (p > 0.05). There was no treatment meal effect on participant postprandial serum biomarkers of inflammation. Postprandial serum triacylglycerols were significantly elevated following the n-6 meal compared to the n-3 meal. Non-esterified fatty acids were significantly increased after consumption of the saturated fat meal compared to other treatment meals."

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High–Saturated Fat Diet Increases Endotoxemia

Participants were randomized to receive 1 of 4 isoenergetic diets for 12 weeks. Two of the diets provided 38% energy from fat: high–saturated fatty acid (HSFA) diet and high–monounsaturated fatty acid (HMUFA) diet. The remaining 2 were low-fat, high–complex carbohydrate (LFHCC) diets and provided 28% of energy as fat. One of these diets (LFHCC n-3) was supplemented with 1.24 g/d of long chain (n-3) PUFA.

After 12 weeks on the assigned diet the participants received a fat challenge in which they received 0.7 g/kg body weight of the same fat composition consumed during the dietary intervention phase.

There was a postprandial increase in LPS levels in participants who received the HSFA fat challenge (following consumption of the HSFA diet), but no postprandial changes were noted in the 3 other groups. In addition, there was a positive relationship between LPS levels and gene expression of IkBa and MiF1 in PMCs. Fasting levels of LPS did not differ between any of the diet groups after the 12-week intervention.

These results suggest that the consumption of the HSFA diet increases the intestinal absorption of LPS, which increases postprandial endotoxemia levels and the postprandial inflammatory response.

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Metabolic endotoxemia and saturated fat contribute to circulating NGAL concentrations in subjects with insulin resistance. - PubMed - NCBI

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Saturated Fat Is More Metabolically Harmful for the Human Liver Than Unsaturated Fat or Simple Sugars

SAT [saturated fat] induced the greatest increase in IHTG [ intrahepatic triglyceride], insulin resistance, and harmful ceramides. Decreased intakes of SAT could be beneficial in reducing IHTG and the associated risk of diabetes.

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https://pubs.acs.org/doi/abs/10.1021/acs.jafc.7b01909

"Metabolic syndrome (MetS) results in postprandial metabolic alterations that predisposes one to a state of chronic low-grade inflammation and increased oxidative stress. We aimed to assess the effect of the consumption of the quantity and quality of dietary fat on fasting and postprandial plasma lipopolysaccharides (LPS). A subgroup of 75 subjects with metabolic syndrome was randomized to receive 1 of 4 diets: HSFA, rich in saturated fat; HMUFA, rich in monounsaturated fat; LFHCC n-3, low-fat, rich in complex carbohydrate diet supplemented with n-3 polyunsaturated fatty acids; LFHCC low-fat, rich in complex carbohydrate diet supplemented with placebo, for 12 weeks each. We administered a fat challenge reflecting the fatty acid composition of the diets at postintervention. We determined the plasma lipoproteins and glucose and gene expression in peripheral blood mononuclear cells (PBMC) and adipose tissue. LPS and LPS binding protein (LBP) plasma levels were determined by ELISA, at fasting and postprandial (4 h after a fat challenge) states. We observed a postprandial increase in LPS levels after the intake of the HSFA meal, whereas we did not find any postprandial changes after the intake of the other three diets. Moreover, we found a positive relationship between the LPS plasma levels and the gene expression of IkBa and MIF1 in PBMC. No statistically significant differences in the LBP plasma levels at fasting or postprandial states were observed. Our results suggest that the consumption of HSFA diet increases the intestinal absorption of LPS which, in turn, increases postprandial endotoxemia levels and the postprandial inflammatory response."

 

[CLASH]

In regards to the captain coconut situation he mentioned that he ate a 30% coconut oil diet and claimed that it made him sick due to LPS translocation. Coconut oil doesnt seem to increase LPS translocation as it is a medium chain fat that does not require bile acids to break it down and form chylomicrons. The chylomicrons are what allows for the lipid raft to form for the endotoxin to translocate. The MCT’s in coconut oil also increase gut epithelial integrity. This essentially discredits his theory that saturated fatty acids specifically a 30% all coconut oil diet made him feel poorly due to an increased gut translocation of LPS.

Furthermore later on, on the forum, he posted that he felt better when switching to butter and olive oil... Both of these fats contain saturated fatty acids and would be much more likely than coconut oil to induce lps translocation across the gut wall via chylomicrons.

Of course this is all besides the point, the increase of LPS translocation by saturated fats is most likely beneficial as a detox mechanism and the saturated and monounsaturated fatty acids have many beneficial properties. Its also besides the point that high quantities of coconut oil are known to cause diarrhea known colloquially as disaster pants...

 

[lvysaur]

Unfortunately the main proponent of the sat fat = lps/bacterial translocation seems to have ragequit the forum

I haven't studied that one too deeply, but I do believe he was on to something. I've written before about how I often have immediate changes in my facial hair when I eat a lot of ice cream.

I also remember seeing a post along the lines of "SFA releases endotoxin short term, PUFA breeds endotoxin long term", backed with a study.

 

[yerrag]

Of course this is all besides the point, the increase of LPS translocation by saturated fats is most likely beneficial as a detox mechanism and the saturated and monounsaturated fatty acids have many beneficial properties.

Do you mind elaborating on what you meant by the LPS translocation being a detox mechanism? My vague understanding of it is that the LPS is carried by chylomicrons into the liver where the detoxification takes place, and where LPS is incorporated into bile and eventually excreted as part of feces. Is this what you mean?

 

[GorillaHead]

Mechanisms for the activation of Toll-like receptor 2/4 by saturated fatty acids and inhibition by docosahexaenoic acid

How does one explain this study where they find pufa to block it.

i also found research that says pufa lowers leptin and leptin raypeat considers inflammatory which I agree with

 

[rob]

Mechanisms for the activation of Toll-like receptor 2/4 by saturated fatty acids and inhibition by docosahexaenoic acid

How does one explain this study where they find pufa to block it.

i also found research that says pufa lowers leptin and leptin raypeat considers inflammatory which I agree with

Omega 3 enrichment of lipid rafts (LRs) causes protein and lipid relocation due to the decreased saturated nature.

TLR4 recruitment to LRs and subsequent dimerization are critical steps in triggering NF-kB.

As a side note, reason dysfunctional cholesterol efflux (ABCA1 knockout) can cause TLR hyper-responsiveness and, conversely, cholesterol-depleting drugs can downregulate TLR signalling as cholesterol is a key constituent of LRs. That said, LR destablisation can adversely effect things like tight junction proteins and, LR cholesterol depletion, has been indicated to increase P2X7 macropore formation, so not great.

On SFAs, whilst their ability to act as TLR4 ligands is unclear, there's plenty of evidence that, particularly, palmitic acid and lauric acid can yield pro-inflammatory effects – how these studies translate to the real world is another thing. Mechanistically, it might be that SFAs can directly effect LRs, which are enriched in cholesterol, sphingolipids and SFAs. Although, from what I've read, it's probably more indirect with SFAs, again palmitate notably, increasing DAG levels and, thus, PKC membrane recruitment. PKC seems to be involved in IKK (and, thus, NF-kB) and JNK activation as well as upregulating NADPH oxidase. Subquent ROS may encourage recruitment of TLRs to LRs potentiating signalling.