Two things need to happen for insulin receptors (or really any receptors) to work. 1) The receptors need to be expressed. This is the actual production (transcription/translation)of the protein. There are a lot of steps between transcription and getting the insulin receptors to the cell membrane. Any of them could be disrupted and then there's always post translational modifications such as glycosylation that can muck things up. 2) Binding of the insulin receptor has result in an intracellular signal cascade, leading to glucose receptors being transported to the cell membrane. I think what is meant by cytosolic signal impedence is that something gets interrupted between insulin receptor binding to glucose receptor translocation. Or even cell signaling to initiate insulin receptor expression.

It's hard to accurately describe the process of insulin resistance as being linear or having a single inciting event. It's more of a breakdown of the entire, circular(ish) system. But I suppose I think of insulin resistance "starting" in the cells that have the most insulin receptors like fat cells.