"Smart" insulin designed to automatically activate when blood sugar gets too high but switch off again when it returns to normal could offer new hope for diabetics, researchers say.

Such drugs could ease the burden on Type 1 diabetes sufferers of having to constantly monitor blood sugar levels to try and judge when to inject insulin and how much to inject, they say.

It could also remove the risk of miscalculation that can lead to blood sugar being too high, which can lead to blindness or heart disease, or too low which, can lead to coma and sometimes death, they add.

Inadequate control of blood sugar levels is the hallmark symptom of diabetes and is most severe in Type 1 diabetes, which is caused when insulin-producing beta-cells of the pancreas are destroyed.

Patients with Type 1 diabetes depend on daily insulin injections for survival.

The inherent dangers in insulin self-dosing led University of Utah biochemist Danny Chou and his colleagues to create Ins-PBA-F, a form of "smart" insulin that self-activates only when blood sugar levels rise.

The smart insulin is a chemically modified version of a naturally occurring hormone, which should make it safe enough to use on a daily basis, Chou says.

What makes the insulin "smart" is an extra set of molecules that binds it to proteins in the bloodstream. While bound, the smart insulin is in a switched-off mode, the researchers explain.

With any increase in blood sugar, glucose locks on to the smart insulin and switches it on, they say.

Tests in mice showed the smart insulin was effective for at least 14 hours, repeatedly and automatically lowering the animals' blood sugar levels when they were fed amounts of sugar similar to what they might consume at mealtimes.

"This is an important advance in insulin therapy," says Chou, co-first author of a study appearing in PNAS Early Edition. "Our insulin derivative appears to control blood sugar better than anything that is available to diabetes patients right now."

"My goal is to make life easier and safer for diabetics," he says.

The smart insulin could undergo Phase 1 human clinical trials in two to five years, the researchers say. This insulin is 'smart' in that it is glucose responsive, chemically modified from a naturally occurring hormone, making it different from previous 'smart' methods that delivered insulin differently.

"At present, there is no clinically approved glucose-responsive modified insulin," study co-author Matthew Weber says. "The development of such an approach could contribute to greater therapeutic autonomy for diabetic patients."