Type 2 diabetes and prediabetes (i.e. higher than normal blood sugar levels but not high enough to be considered type 2 diabetes) have been previously linked to a higher risk of depression and cognitive impairment. Prediabetes has been also associated with a decline in the transport of insulin to brain regions, raising the question of whether insulin neuronal functions are compromised which could, in turn, lead to a negative impact on cognition and memory. On the other side, physical activity and exercise influence cognition and memory through the maintenance of gray matter volume and cerebral blood flow, among others. However, little is known about whether exercise may impact how effectively brain cells use blood glucose in older adults with prediabetes.
In a new study published in the journal of Aging Cell (Willey), a team of researchers led by Dr Steven K. Malin and Dr Dimitrios Kapogiannis from Rutgers University, New Brunswick (New Jersey, US) and National Institute on Aging, Baltimore (Maryland, US) investigated whether short-term exercise raises neuronal insulin signalling in cells that respond to insulin in prediabetes. The researchers involved a group of 21 participants who were in their 60s, sedentary and had prediabetes. The participants engaged in 12 individual and supervised 60-minute exercise training sessions of moderate to high intensity. All of them took a glucose drink before and after their training.
The researchers collected blood samples from all the participants at the start and end of exercise training, and measured the level of proteins involved in insulin sensitivity carried within neuronal extracellular vesicles (i.e. vesicles released by brain cells). The team found that, in older adults with prediabetes, short-term exercise training increased the level of neuronal extracellular vesicles containing tAkt (an insulin signalling protein) in response to glucose ingestion in older adults with prediabetes. Although this study has some limitations (e.g. relatively small size of participants, unknown potential impact of sex on the outcomes and lack of a true control group), these data suggest that exercise may improve the brain’s capacity to respond to insulin. More studies are needed to understand how insulin signalling proteins carried within neuronal extracellular vesicles relate to brain function and the future development of dementia in people at risk for type 2 diabetes.