Foie Gras (8) Vaughan's macrophages

Okay, back to the Vaughan paper

A High Linoleic Acid Diet does not Induce Inflammation in Mouse Liver or Adipose Tissue

and a look at their macrophages in cell culture. The pattern is consitent so I'll just run through MCP-1 gene mRNA expression. As in the last post I am going to work on the basis that these genes are, in the absence of trauma or infection, going to respond to mitochondrial/NOX ROS production. It's a graph of relative expression, the control represents the response to the ROS being produced by supplying glucose at around 30mmol/l. That will be in response to NOX-2 being activated through calmodulin kinase II as we would expect. Even without insulin, these ROS will activate the phosphorylation of AKT and translocate GLUT4s to the cell membrane. It's the black column:

Adding 50 μmol/l of stearic acid (white column) will generate ROS by reverse electron transport though complex I, via an increase FADH2:NADH ratio, physiologically to limit insulin facilitated glucose ingress. Even if there is no insulin present, it still generates the ROS, which will limit the facilitation provided by NOX-2 derived ROS. Saturated fatty acids do this at low delta psi levels, there is no multi-enzyme/complex ROS generation, they just generate neat and tidy, fully physiological RET. The cell responds appropriately with superoxide dismutase and catalase and a coincidentally extended lifespan. Okay, I can't resist it, here he is again:

Oleic acid is another whole series of posts, so I'll mostly gloss over it. Oleic acid is designed to facilitate insulin signalling as a physiological balance to palmitic acid. It generates some ROS but not enough to significantly resist insulin signalling. There are many concepts stemming from this and here is not the place to discuss them.

Linoleic acid (hatched column) utterly fails to generate enough RET to limit glucose ingress, so glucose continues to enter, while at the same time the LA provides calories in excess of what the cell needs. The problem is that LA cannot shut down glucose ingress because it fails, through its double bonds, to generate the RET facilitated ROS to limit that glucose ingress.

The cell is full of ATP and depleted of ADP so ATP synthase cannot turn. Delta psi rises and above 170mV large numbers of ROS are generated. These come from a combination of complex II, complex III, electron transporting flavoprotein dehydrogenase and mitochondrial glycerol-3-phosphate dehydrogenase. Oh, and I guess some from RET. All secondary to high delta psi.

All stemming from inadequate RET derived ROS from LA's surfeit of double bonds. A few prophylactic ROS, produced without an high delta psi, stops an awful lot of problems. I think the phrase is that a stitch in time saves nine...

I think here is a good place to point out that ROS generate a response in inflammatory gene mRNA expression, probably at any level of exposure. Low levels will result in normal physiology, high levels will result in frank inflammation,  but also will induce inflammation limiting gene expression, in which I would include multiple uncoupling protein genes. Failure to limit high levels of ROS generation clearly results in apoptosis or, given a catastrophic failure of the ETC secondary to 4-HNE and associates, necrosis.

This paper is quite unique in view of the low dose of fatty acids used. If they had chosen the standard route of 1000μmol/l FFAs in addition to glucose at 25mmol/l (utterly non physiological) then RET would have dominated, giving apoptosis/necrosis levels of ROS, meaning stearic acid would be bad (usually palmitic is used), oleic less so and LA would be almost harmless. There is an infinite supply of such papers to reinforce the stupidity of saturophobia.

Okay, the in vivo mice next.

Peter