TLDR This is a weird study which might show the insulin sensitising effect of linoleic acid in obesity resistant rats.
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I deeply dislike this paper on so many levels. I'm not going to go through everything which is wrong with it, I'll just highlight a few aspects which strike me as interesting.
The first (unexpected) finding is that none of the groups of rats on high fat diets were significantly heavier than the chow fed rats. The PUFA fed rats were slightly lighter (you read that correctly) and the SAT fed rats were slightly heavier, but all ns at eight weeks of feeding. Who can buy rats which can eat coconut/lard and not gain weight? Korean rats? Korean lard? Who knows. But neither the safflower oil nor the lard fed rats become obese. I find this very, very odd in a set of "we bought them off the shelf" Wistar rats. But well, maybe. Just seems odd.
Second point (expected) is that not only did the SAT fed rats develop insulin resistance, but the PUFA fed rats did not, in fact they showed enhanced insulin sensitivity when compared to either chow or SAT fed rats. This is compatible with the Protons view of PUFA oxidation in non-adipocyte distended rats.
Third (expected) is that as insulin acted on muscles under PUFA those muscles developed the highest levels of stored triglycerides. This is exactly what you would expect, insulin diverts excess calories to be safely sequestered as triglycerides.
The fourth point (very unexpected) is that while triglycerides were being happily sequestered in to muscle, they weren't being sequestered in to adipocytes. Adipocyte sequestration of triglycerides (obesity) happens routinely in a huge swathe of linoleic acid feeding trials in many different species.
Sooo, can you extract anything from this mass of contradictions? I'm just wondering whether if you happened upon a generally obesity resistant rat strain you might be left viewing the insulin sensitising effect of PUFA oxidation without the insulin resistance generating effect of adipocyte distension.
Maybe it separates out the the opposing drives on the adipocyte under PUFA exposure...
Maybe.
Peter
