Hi there,
ok here's my take on it. We know that glucose is an osmotic agent because in Type II diabetes, which is characterized by hyperglycemia, patients will tend to go into a hyperosmolar coma.
So, if there is hyperinsulinemia present, there will be hypoglycemia, and a resultant hypo-osmolar plasma which will tend to decrease plasma volume. This decreased volume will then activate the RAA system, resulting in sodium retention to correct the hypoglycemia-induced hypovolemia.
Hope that was enough.