Insulin-like proteins are naturally produced by some viruses
Insulin goes viral

Analyses of viral DNA revealed that four viruses synthesise proteins that look a lot like insulin. The viral insulin binds to rodent and human insulin receptors, and switches on all related signalling pathways within the cell to stimulate sugar uptake or cell division. The identified viruses are known to infect fish, but whether they also can infect humans, either directly or through fish consumption, is at present not known. The viruses will be used for further studies in diabetes type I research, and might help pharmaceutical industry to design new insulin-like proteins in the treatment of disease.

Read the full story: Joslin Diabetes Center
Scientific publication: pnas