pronunciation - Should it be 'an' or 'a' in front of an abbreviation?

I am using abbreviations for well-known phrases: e.g., "Nash equilibrium" becomes NE and "neural networks" becomes NN. Should I use "an NN" or "a NN"? Does it matter whether a reader "unfolds" the abbreviation or not when reading? That is, I think it is often the case that NE is read "Nash equilibrium", then it seems appropriate to use "a NE".