High Blood Glucose Levels Associated with Depression Risk in Patients with Type 1 Diabetes

The brains of hyperglycemic patients with Type 1 diabetes produce elevated levels of the neurotransmitter glutamate, which may increase their risk of depression.

Study results presented at ICE/ENDO 2014, the joint meeting of the International Society of Endocrinology and The Endocrine Society, show that patients with Type 1 diabetes with elevated blood sugar levels may be at higher risk for developing depression due to increased levels of glutamate, which is linked to depression at higher levels, and weakened connections between regions of the brain that control emotions.

Researchers studied 19 adults (8 with Type 1 diabetes and 11 healthy controls) using functional magnetic resonance imaging (MRI) scans and magnetic resonance spectroscopy to measure brain activity and glutamate levels in patients when their blood glucose levels were at normal levels, and again when their blood glucose was elevated.

According to a news release from The Endocrine Society, “raising the blood sugar level reduced the strength of the connections among regions of the brain involved in self-perception and emotions to a greater degree in diabetic patients than in healthy control subjects. The strength of these connections in the brain was reportedly also lower in diabetic patients with poor long-term glucose control, as shown by a high hemoglobin A1c level, compared with diabetic subjects in good control, who had a low hemoglobin A1c.”

Study authors Nicolas Bolo, PhD, from Beth Israel-Deaconess Medical Center, and Donald Simonson, MD, MPH, ScD, from Brigham and Women's Hospital, said It was traditionally thought that patients with Type 1 or Type 2 diabetes have higher rates of depression than their nondiabetic peers because of the increased stress of managing a complex chronic disease… Our results suggest that high blood glucose levels may predispose patients with Type 1 diabetes to depression through biological mechanisms in the brain.”

According to the authors, raising blood glucose levels in patients with Type 1 diabetes resulted in elevated levels of the neurotransmitter glutamate in an area of the brain responsible for controlling emotions, an effect that was not seen in the healthy controls. These changes in the brain increase the risk of developing depression, which led to diabetic participants reporting worse scores on a depression questionnaire compared to healthy controls.