Brain Glucose Levels Drop in Patients with Obesity, Diabetes

The prevalence of obesity and type 2 diabetes (T2D) has been increasing among Americans. These conditions can increase the risk of heart disease, cancer, and other potentially life-threating diseases.

Glucose levels in the brains of patients with obesity and T2D are observed to be much lower than levels observed in lean individuals, according to a study published by JCI Insight. The authors hypothesize that these changes may lead to disordered eating among patients with the comorbidities.

Both obesity and T2D have been liked to reduced metabolism in the brain, which has also been associated with Alzheimer’s disease. The underlying causes of this relationship are currently unknown.

In the study, the authors examined brain glucose levels among patients who were lean and healthy and those who were obese or had poorly-controlled T2D. Patients received intravenous infusions of glucose for 2 hours following overnight fasting. The authors then used magnetic resonance spectroscopy to evaluate glucose levels in the brain.

Although blood glucose levels were similar for all patients, those with obesity and T2D had markedly different brain glucose levels, according to the study.

“We found decreased or blunted entry of glucose into the brain,” said first author Janice Jin Hwang, MD.

The observed decrease could be a mechanism that changes the brain’s capability of sensing glucose, according to the study.

Patients’ hunger, satisfaction, and fullness were also evaluated before and after the glucose infusions.

“The lean people who had more glucose entry into the brain also felt more full, even though they hadn’t eaten overnight,” Dr Hwang said.

The authors hypothesize that patients with obesity and T2D may not be getting enough glucose to the brain. This occurrence leads to not feeling full and can cause overeating and spikes in blood glucose levels.

“Glucose is the most primitive signal to the brain that you’ve eaten,” Dr Hwang said. “Could it be that obese individuals are not getting sugar into the brain, and not sensing it; thus, the feedback loop to stop eating could also be blunted?”

These findings highlight the significance of glucose transportation from the blood to the brain. The authors suggest brain glucose levels may present a potential treatment target for the conditions; however, more research is needed.