Are you trans-phobic? (1)

I've had this paper lying around on my hard drive for some time

Trans-palmitoleic Acid Reduces Adiposity via Increased Lipolysis in a Rodent Model of Diet-Induced Obesity

I don't like it much in terms of writing style, details included/omitted and perspective of the authors but their data look okay and confirm my deepest biases, so I like this aspect.

The usual Bl/6 mice on high fat diet (around 6.5% LA, linoleic acid) vs low fat (around 3.7% LA)

Weights:

We can see that 4% of calories as trans palmitoleate partially offsets the obesogenic effect of just over 6% linoleic acid in Bl/6 mice.

In terms of adipocyte size the mean surface area on a histology section is normalised:

I would expect normal sized adipocytes to have normal basal lipolysis and not be causing excess FFA release in the presence of insulin. The study didn't look at insulin or insulin resistance but they mention various papers in passing where there are suggestions of this being the case.

You could, from isolated adipocyte studies, make a similar case for elaidic acid (ie shock horror, trans oleic acid, mmmm Crisco).

Replacing Cis Octadecenoic Acid with Trans Isomers in Media Containing Rat Adipocytes Stimulates Lipolysis and Inhibits Glucose utilization

"Compared with oleic acid, both trans isomers reduced (P < 0.01) the amount of glucose converted to cell lipid in both experiments. Glucose oxidation to carbon dioxide also was lower for both trans fatty acids in Experiments 1 (P < 0.05) and 2 (P < 0.06). Lipolytic rates were increased (P < 0.01) in both experiments by replacing oleic acid with either of the trans isomers."

You can make the same case for trans vaccenic acid using whole rats:

Diets enriched in trans-11 vaccenic acid alleviate ectopic lipid accumulation in a rat model of NAFLD and metabolic syndrome

"...and decreased adipocyte size (−44%) versus control rats."

also worth noting

"[trans vaccenic acid] supplementation also increased metabolic rate (7%)"

Trans vaccenic acid stops the development of metabolic syndrome just as trans palmitoleic acid does. For those of us who consider metabolic syndrome to be the replacement of insulin/sympathic system controlled lipolysis by elevated, uncontrolled, adipocyte size determined basal lipolysis this is exactly what you might expect.

In this next study they replaced 7.2% trans vaccenic acid and 3.4% elaidic acid (original Primex) with palmitate (Primex-Z) while maintaining 24% of the fat as LA. Much as I love palmitic acid it is not an active lipolytic agent in the way that the trans fats are.

Chronic ingestion of Primex-Z, compared with other common fat sources, drives worse liver injury and enhanced susceptibility to bacterial infections

Here are the weights at 16 and 30 weeks, first column is the control Bl/6 mice, second is the trans fat mice, third is the unopposed LA:

and here are the adiposity index results:

Sadly again no assessment of insulin function was made but with comparable adiposity to the control mice I wouldn't expect them to be insulin resistant. The corn oil group will have been pushing uncoupling levels of LA. By 30 weeks everything looks pretty much as I would expect it to.

So I might claim not to be trans-phobic. Except I support JK Rowling.

Why do Risérus*, Willet and Hu disagree?

[* That's Risérus as in The Muffin Study and Willet and Hu are the Usual Suspects]

Dietary fats and prevention of type 2 diabetes

"Taken together, the evidence suggests that replacing saturated fats and trans fatty acids with unsaturated (polyunsaturated and/or monounsaturated) fats has beneficial effects on insulin sensitivity and is likely to reduce risk of type 2 diabetes. Among polyunsaturated fats, linoleic acid from the n-6 series improves insulin sensitivity."

Which is, of course, absolute, total bollocks.

There is a reason they make this mistake but this post is too long and rambling already.

Peter