First a bit of trivia...In medieval Europe the French lilac plant was used to treat frequent urination. French Lilac in bloom (other wise called Goat's rue or Italian fitch)This blooming G. officinalis is rich in guanidine. The plant’s long-recognized hypoglycemic properties led eventually to the synthesis of the biguanide compound metformin.
French Lilac was also known as goat's Rue because goats didn't like to eat it. The goats steered clear of the plant because it contains a compound that acts naturally to lower blood sugar in animals who eat it. Reuben J Shaw,PhD, Asst Professor in Molecular and Cell biology at Howard Hughes Medical Institute discovered that metformin helps insulin to control blood glucose levels by binding to a "metabolic master switch" called AMPK (adenosine monophosphate-activated protein kinase) that blocks glucose production in the liver. Dr Shaw explains that HDAC's (histone deactetylases) , a group of enzymes that start glucose production when the blood glucose is low, are in liver cells and stay outside the nucleus. When blood glucose is getting low from fasting, class II HDAC's rapidly go into the liver cell nucleus to "turn on the genes needed for glucose production."
Currently,a new focus of diabetes research is to find drugs that specifically inhibit HDAC's involved in gluconeogenesis.
Metformin is now being actively studied as an anti-cancer drug. It is not completely clear by what mechanism metformin inhibits cancer cells, and which cancers would be most susceptible to it.
Michael Pollak, an oncologist at McGill University in Montreal., and his team have shown that metformin could inhibit growth of breast cancer cells in a lab dish by awakening an enzyme called AMPK. The group further found that revved-up AMPK inhibits the activity of mTOR — a protein involved in cell growth and proliferation
Here are some references for further reading. This is definitely something to keep up on as time goes by.