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Unread 10-26-2010, 10:15 PM
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lylemcd lylemcd is offline
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Originally Posted by JamesKrieger View Post
I would agree with you that too many people will accept a rat model if it supports their argument, and then automatically dismiss it if it doesn't and say, "These are rats and not humans".

However, I don't think it's disingenuous to accept rat models under certain circumstances and be extremely cautious with or dismiss them under other circumstances. It depends upon what is being examined, and the magnitude of the differences between rat and human physiology and whether those differences are relevant to the problem at hand.

For example, rats have a greater capacity for de novo lipogenesis than humans, which is why some of the high fructose feeding rodent studies are not completely relevant to humans (particularly given that the fructose contents of the diets are often ridiculously high).

However, in this particular case, I do think the rat model is relevant. It's a model examining the contribution of glucose and non-glucose sources of glycerol for triglyceride synthesis under different dietary conditions. I don't think the differences in rat and human physiology would have a great impact on the applicability of these results to humans. The low carb zealots argue that carbohydrate is required for fat synthesis as a glycerol source. This paper makes it clear that adipose tissue "finds a way". In the presence of high carbohydrate, it will synthesize glycerol from glucose. But in the presence of high fat and no carbohydrate, it will synthesize glycerol through glyceroneogenesis from the ingested triglycerides. And one pathway is not more efficient than the other.

I think it comes down to why someone is dismissing or accepting a rat model.
I think that makes it far too easy to draw a line in the sand wherever you want to in this case.
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