In 2006, scientists in Toronto reported that they could cure diabetic mice by eliminating the nerves to the beta cells. They did this by adding capsaicin, the substance that makes hot peppers hot.
Especially interesting was the finding that the treatment reduced insulin resistance, and the researchers postulated that insulin resistance may play a large role in type 1 as well as type 2 diabetes, suggesting that the two types share more factors than once thought.
The news blanketed cyberspace, and people were excited. Unfortunately, diabetic mice have been cured hundreds of times, and in this case as well, an exciting discovery did not lead to an instant cure.
Now another exciting research report from Toronto researchers has appeared in the Proceedings of the National Academy of Sciences. In this case, they prevented diabetes and even reversed it in some mice by injecting them with gamma-aminobutyric acid, usually referred to by its acronym, GABA. In the mice, the GABA not only made the beta cells grow and survive, but it reduced the autoimmune attack on the beta cells that is so important in causing type 1 diabetes.
GABA is a well-known neurotransmitter, meaning the body uses it to transmit signals in the nervous system. But it turns out that beta cells produce GABA as well. Alpha cells, the cells that produce glucagon, contain GABA receptors, and when the beta cells secrete GABA, the production of glucagon is suppressed.
When you have no functioning beta cells, they can't produce GABA, the alpha cells keep secreting glucagon, and your blood glucose levels keep going up and up.
Beta cells also contain GABA receptors, and when GABA reacts with these beta cell receptors, the secretion of insulin is increased.
In other words, GABA turns down glucagon and turns up insulin, both of which reduce blood glucose levels.
The GABA also appears to be anti-inflammatory and suppressed the autoimmune attack on the mouse beta cells. It not only prevented diabetes but actually reversed it in some of the mice that had already developed it.
However, the GABA did not reverse diabetes in mice that had had diabetes for a long time. The authors suggested that these mice didn't have enough beta cells left to regenerate. And the reversal of diabetes was not permanent. Some of the mice eventually reverted to a diabetic state.
The authors used several different types of diabetic mice that are supposed to be models of type 1, but of course none of them are exactly the same. So, like so many mouse studies, this work has not solved the diabetes puzzle. But it's an exciting new approach.
One thing that is interesting is that GABA is produced from an amino acid called glutamic acid. The enzyme that produces it is called glutamic acid decarboxylase, or GAD.
That might sound familiar to you. That's because testing for antibodies to one form of GAD, called GAD-65, is one way to determine if someone has an autoimmune form of diabetes. If you're GAD-65-positive, you have autoimmune diabetes, or type 1.
If you're producing antibodies to the enzyme that produces GABA, could it be that a lack of GABA really is a major cause of type 1 diabetes (and perhaps a partial cause of type 2 as well)?
Obviously, scientists (and drug companies) will want to find out. And we wish them success. Insulin was discovered in Toronto. Will a real cure eventually come from Toronto as well?
Published On: July 06, 2011