Sunday, May 19, 2013

De Novo Lipogenesis Again (and Science and Science Reporting)

In my last post, I just posted a graphic taken from an "FYI" inset by a scientist, Marc Hellerstein, whose work I've blogged on quite a bit here. (Anyone wanting to refresh can click on the image and enlarge.)  One good post to begin with if you are not familiar with that name is Where do Triglycerides Come From? I would say that between Marc Hellerstein's No common energy currency: de novo lipogenesis as the road less traveled and the works of Eric Jequier such as Nutrient effects: post-absorptive interactions, the case that hepatic DNL is quantitatively insignificant in human energy balance/fat accumulation is strong and has not been refuted by some newer scientific findings.    

I do hope to expand on the role of adipose DNL at some future point -- teaser: I have a paper showing that reducing WAT lipolysis upregulates adipose DNL and improves glucose homeostasis in the IGT irrespective of body weight  -- but adipose DNL had not been central to the arguments of folks from Taubes to Lustig to Eades to Naughton to a list far too long to go through here.  The claim has been that excess carbs are converted in the liver to fat and sent to the fat tissue for storage.  

Does this occur?  Yes.  Is it significant?   Only if you consider a couple grams fat synthesis per day significant at the metabolic cost "wasting" one gram carb for every four grams converted to fat ... and only if you consider a few grams of fat significant in the context of consuming 100, 200 or more grams of fat that is already fat.
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