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French Scientists Investigating Possible Link Between Anxiety And Diabetes

Diabetes is a known risk factor for many other health conditions and events, particularly heart
disease, stroke, kidney disease, and vision loss. Perhaps more surprisingly, research has also
found that people with diabetes are more likely to experience anxiety when compared with
healthy individuals.
For example, one study published in 2008 found that anxiety had approximately "20% higher
prevalence" over the lifetimes of people with diabetes, compared with those without this
metabolic condition. It is unclear exactly what is at the root of this link.
Insulin resistance is characterized by the body's inability to process glucose (a simple sugar)
properly, which results in overly high blood sugar levels.
Some studies have linked insulin resistance directly with hormonal imbalances in the brain and,
as a result, the development of depression-like and anxiety-like behaviors and symptoms.
Other studies have simply pointed out that depression and type 2 diabetes seem to share a
physiological characteristic in insulin resistance.
Of course, the straightforward answer, that people with diabetes have more cause for worry and
depression, and therefore more of those characteristics, is never even addressed.
Recently, a team of researchers — many from the University of Toulouse, the University of
Bordeaux, and other research institutions in France — have conducted a study in mice to
investigate the link between anxiety, depression, and insulin resistance further and to find out
how they might go about addressing all these problems simultaneously.
In their research — the findings of which appear in The Journal of Neuroscience — the team
worked with male mice that had been fed a high-fat diet so that the scientists could simulate
insulin resistance.
They also noted that the mice on this type of diet showed changes in the brain that were
consistent with the presence of anxiety-like symptoms, which the researchers call one of the
most visible and early symptoms of depression."
The researchers conducted two types of experiments. In one, they gave each mouse one of two
kinds of drugs: either metformin, a common drug used to prevent and treat type 2 diabetes, or
fluoxetine, a common antidepressant.
The team — led by Bruno Guiard, Ph.D., an associate professor of neuroscience and
pharmacology at the University of Toulouse — found that metformin reduced anxiety-like
behaviors in the mice.

This, the researchers observed, was because the diabetes drug boosted levels of serotonin in the
brain.
Serotonin is a hormone and neurotransmitter that plays a key role in the regulation of emotions.
This is why people sometimes refer to it as the happiness hormone. Metformin increased brain
serotonin by reducing circulating levels of branched-chain amino acids, a type of amino acid that
decreases the levels of tryptophan entering the brain.
Tryptophan is also an amino acid, but an essential one, meaning that humans and other mammals
— including mice — can only obtain it from the food they eat. But tryptophan is especially
important in this equation because the brain uses it to produce serotonin.
In short, if the brain does not have access to enough tryptophan, it cannot make enough
serotonin, which can produce imbalances that, in turn, may facilitate symptoms of anxiety and
depression. Metformin provided a solution by allowing more tryptophan to "flow" into the brain,
thus boosting brain levels of serotonin.
Guiard and colleagues saw similar results when they changed some of the rodents' diets, giving
they feed with reduced levels of branched-chain amino acids.
The researchers are hopeful that, in the future, these preliminary findings might help healthcare
professionals come up with better ways of treating, not only metabolic conditions but also mental
health symptoms.
Perhaps they could start by cheering up diabetics and then measuring their insulin resistance. If
there is any truth to this idea whatsoever, this process should achieve immediate results and has
the added benefit of actually curing diabetics starting now, as opposed to waiting ten years for
FDA approval.
And that is certainly worth a try.