Research has revealed that insulin resistance, a key characteristic of diabetes and prediabetes, is sometimes related to symptoms of depression and anxiety. But a recent study in mice has found that metformin, a diabetes medicine, can combat these signs.
According to the Centers for Disease Control and Prevention (CDC), above 100 million adults in the U.S live with diabetes or prediabetes. This is the condition which usually precedes the type 2 diabetes development. Diabetes is a risk factor for many other health disorders, chiefly stroke, kidney disease, heart disease, and vision loss.
Surprisingly, research has also found that diabetic individuals are more likely to experience anxiety when compared with fit individuals.
For instance, a study published in 2008 discovered that anxiety had an almost “20% higher prevalence” over the lifetimes of individuals with diabetes than those without this metabolic condition.
Precisely, it is unclear what is at the origin of this association between diabetes and anxiety. However, some studies have linked one particular aspect of these metabolic disorders, insulin resistance, with mental health signs.
Insulin resistance is the body’s inability to process glucose properly, which results in excessively high blood sugar levels.
Some researchers have associated insulin resistance straight with hormonal imbalances in the brain. This leads to the development of depression and anxiety-like activities and symptoms. However, other studies have pointed out that depression and type 2 diabetes share a physical characteristic in insulin resistance.
The connection between anxiety and diabetes
Recently, a team of scientists from different institutions in France has conducted research in mice to study the association between anxiety, depression, and insulin resistance further. Moreover, they wanted to find out how they might go about addressing all these complications at the same time.
In this research, the team worked with male mice which had been fed a high-fat diet so that the researchers could simulate insulin resistance. These findings were published in The Journal of Neuroscience.
Researchers noted that the mice on this diet showed changes in the brain. They found that these changes were dependable with the presence of anxiety-like symptoms, which they call “one of the most noticeable and early signs of depression.”
The scientists conducted two types of experimentations for this. In one, they gave each mouse either metformin, a drug used to treat type 2 diabetes, or fluoxetine, a common antidepressant. The team found that metformin reduced anxiety-like conducts in the mice. This was because the diabetes drug improved the serotonin levels in the brain.
Metformin and the ‘happiness hormone’
Serotonin is a neurotransmitter and hormone which plays an important role in the regulation of feelings. This is why it is also referred to as the happiness hormone.
Metformin increased brain serotonin levels by decreasing circulating levels of branched-chain amino acids. This is a type of amino acid which reduces the tryptophan levels entering the brain.
Tryptophan is an essential amino acid. It means that humans and other mammals — including mice — can only obtain it from the food they consume. Tryptophan is particularly very important because the brain uses it for serotonin production.
Briefly, if the brain does not have enough tryptophan, it cannot make serotonin. This can cause disproportions which, in turn, may cause symptoms of anxiety and depression. Metformin provided a solution to this by permitting more tryptophan to “flow” into the brain. Thus, boosting brain levels of serotonin.
Researchers saw similar results when they altered some of the rodents’ diets, giving them feed with reduced levels of branched-chain amino acids.
The researchers are confident that, in the future, these preliminary outcomes might help healthcare professionals come up with improved ways of treating, not only metabolic illnesses but also mental health signs.