Overweight and obese individuals with early stage type II diabetes (T2D) tend to have more severe and progressive abnormalities in brain structure and cognition than do normal-weight people, according to new research published in the journal Diabetologia.
For the study, researchers in Korea and the US examined how being overweight or obese could impact the brain and the cognitive function of people with early stage type II diabetes
It is well-known that when T2D is chronic, patients are more susceptible to a wide range of health problems in multiple organs throughout the body. The disease may also lead to complications in the brain that accelerate cognitive dysfunction or increase the risk of dementia.
Although the exact mechanism underlying how T2D alters the brain is not fully understood, several metabolic side effects including insulin resistance, poor blood sugar control, and inflammation have been suggested as playing a role.
In addition, obesity is associated with a greater risk for T2D and can often precede its onset. Being overweight has also been linked to metabolic dysfunction, which is independently associated with brain alterations. Still, little is known about the impact on the brain of excess weight or obesity in the presence of T2D.
Researchers from the Ewha Brain Institute and the Ewha Womans University in South Korea and the Brain Institute at the University of Utah recruited 150 Koreans aged 30 to 60 to participate in the study. A total of 50 participants were overweight/obese with T2D, 50 were normal-weight with T2D, and 50 non-diabetic, normal-weight individuals acted as a control group.
Those with diabetes had been diagnosed within the previous five years and had not received stable insulin therapy. Individuals with chronic diabetic complications or major medical, neurological, or psychiatric disorders were excluded from the study.
Data about the structure of participants’ brains were acquired using magnetic resonance imaging (MRI), which allowed the mean thickness of the cerebral cortex to be measured across its entirety. Subjects also completed tests of memory, psychomotor speed, and executive function, as these are known to be affected in people with T2D.
The findings show that grey matter was significantly thinner in clusters in the temporal, prefrontoparietal, motor and occipital cortices of the brains of diabetic study participants when compared to the non-diabetic control group.
The researchers also found more extensive thinning of the temporal and motor cortices in the overweight/obese diabetic group, compared to normal-weight diabetics. There were also region-specific changes, suggesting that the temporal lobe has a particular vulnerability to the combined effects of having T2D and being overweight or obese.
Specifically, people of Asian ethnicity tend to be more vulnerable to slight increases in BMI and are at higher risk of T2D than other ethnicities. This vulnerability may be linked to differences at the cellular level as well as a tendency toward insulin resistance, even in lean individuals. The authors note that the potential for ethnic differences in brain vulnerability to T2D and/or obesity may need to be taken into account when interpreting their results.
“Our findings also highlight the need for early intervention aimed to reduce risk factors for overweight or obesity in type II diabetic individuals to preserve their brain structure and cognitive function,” said the authors. They stress that the importance of managing insulin resistance during early stage T2D may be greater than previously thought.