Would it be safe to inject pure insulin to increase anabolism?
Safe, no. Incredibly Anabolic? Yes.
Safety is relative... it is life threatening to cross the street, or drive to work on a daily basis - however we subscribe to certain behaviors and patterns such as looking both ways or obeying the speed limit and wearing a seat restraint.
Insulin, much like DNP, are both vilified in an unfair and intellectually dishonest light. If you are an educated and calculating bodybuilder who is exacting in all their efforts with a solid set of cumulative years of consistent training who is fervent about making progress once that physiological wall is encountered rendering us all at an anabolic stale mate - then Insulin can be used wisely and with utmost efficacy by those who run it concurrently with other AAS and thyroid potentiating drugs to mitigate adipogenesis.
I can understand and even uphold (to a point) the horrendous collection of disinformation circulating in the cyber sphere regarding Insulin, because every eighteen year old with a gym membership who over hears Johnny Benchpress mention steroids, wants to immediately board the fast train to magazine cover worthy proportions. If pouring gasoline on yourself and then inviting friends over to have a bonfire was purported to build slabs of muscle by some meat head with their arms out to the side doing their best impersonation of a 747 coming in for the landing, someone would try it.
Insulin is an irrefutable powerhouse of limitless potential, but never underestimate the just-as-powerful (and dangerous) philosophy of more = better being enacted by an unlearned teenager who jabs himself in the stomach with 100iu's of Humulin because he didn't know normal syringes couldn't be used.