More About Big Dogs and Little Dogs

Probably from all the excitement about the report yesterday in the journal Science explaining why little dogs are little and big dogs are big, I forgot to mention a couple of things in my posting about the report. First, do you know why pigmies are short? It could be that they have the IGF-1 suppressor gene just like the little dogs.  Actually, they don’t; in the pigmies, the “problem” (I suspect the pigmies don’t consider their short stature a problem, just the normal state of affairs) is failure to respond to the IGF-1/IGFBP3 complex- they just don’t generate whatever growth factors are normally stimulated by the IGF-1/IGF-1BP3.  Just another example of what I mentioned yesterday- in nature, generally whatever can go wrong will do so sometimes.  Of course, we should be thankful that most of the time, things work just fine.

One other thing- treating people (or dogs) with IGF-1. I forgot to mention that IGF-1 must be injected, it’s very expensive,  and it causes hypoglycemia (low blood glucose levels).  Thus, treatment with IGF-1 has medical and financial risks.  The reason it causes hypoglycemia is that the structure of IGF-1 is very similar to the precursor molecule to insulin, proinsulin.  Thus, the IGF-1 acts like insulin in some ways.  I think that’s pretty interesting.

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