INS and diabetes mellitus: Of note, insulin and IGF-1 resistance and deficiency are typically observed early in the progression of AD and the abnormal molecular and biochemical alterations parallel those seen in type 1 diabetes mellitus (T1DM)/T2DM, leading some to use the term “type 3 diabetes mellitus” (T3DM) to reflect the concept that insulin resistance within the brain may cause AD50,61,67–69.