Type 2 diabetes is an incurable condition affecting around 350 million individuals worldwide, and it’s on the rise. It can result in all sorts of serious long-term health issues, such as blindness, kidney failure and an increased risk of developing cardiovascular disease or stroke. Although treatments exist, many have undesirable side effects, such as weight gain and liver damage. But encouragingly, scientists may have just accidentally stumbled upon a new effective agent against the disease, and we won’t have to wait years to find out whether it is safe or causes lots of side effects since it is already widely used in many over-the-counter medicines.
The candidate drug is called dextromethorphan, which is a common active ingredient in various cough remedies. Researchers found that this compound boosted the release of insulin by pancreatic cells in tissue culture studies, animal tests and even diabetic humans enrolled into a small trial. Although these results are promising, the researchers urge diabetics to not start self-medicating with cough syrup since larger trials are required to determine whether it is indeed an effective treatment. The study has been published in Nature Medicine.
Type 2 diabetes is a progressive metabolic disorder characterized by abnormally high blood sugar, or glucose, levels. This is a result of the body not producing enough insulin or cells failing to react properly to it, which is known as insulin resistance. Glucose is a major energy source for our cells and it is the job of insulin to shuttle it from the blood into muscle and fat cells for storage.
Although the exact cause of diabetes is unknown, scientists suspected that a particular type of receptor, called an NMDA receptor, may play a role. These are found throughout the nervous system, participating in cellular communication and also helping keep neurons alive. But they are also found in the pancreas on insulin-secreting cells known as beta cells, which are functionally impaired in those with diabetes, so scientists began to wonder whether their activity was contributing to the lack of insulin produced by those with type 2 diabetes.
To investigate this idea, scientists began inhibiting the activity of these receptors in mice and human pancreatic cells in a dish, which they predicted would worsen insulin production. On the contrary, this actually increased their glucose-stimulated insulin secretion and even boosted their survival.
Taking this one step further, the researchers decided to investigate whether dextromethorphan (DXM) could exert similar effects, since this drug suppresses coughs by acting on NMDA receptors in part of the brainstem. They found that long-term DXM treatment of mice with models of type 2 diabetes enhanced the insulin content of pancreatic cells, increased the number of insulin-producing cells in the pancreas and also improved blood sugar control.
Since this drug is already approved and widely used, the scientists decided to conduct a small dose trial on 20 male diabetic patients. Not only did DXM increase their insulin levels, but it also enhanced glucose tolerance. These encouraging early results therefore warrant further study, so the researchers hope to set up a larger trial to investigate their use as a treatment for diabetes.