Over a century ago, the revolutionary discovery of insulin transformed the lives of diabetic patients. Today, new research from the University of Toronto suggests that insulin may hold promise for other conditions, too.
The study, which examined the effects of insulin on brain cognition across various conditions, was published in PLOS ONE in June 2023.
Understanding insulin and its functions
Insulin, a hormone produced in the pancreas, plays a pivotal role in regulating blood glucose levels throughout the body. This is particularly important for people with diabetes, who often inject insulin as a way of managing their condition.
Until recently, the brain was considered insulin-insensitive, meaning it was thought to have minimal to no insulin receptors. However, since the discovery of widespread insulin receptors in the brain, it is now considered an insulin-sensitive organ. Specifically, insulin influences neurotransmitter levels, brain cell communication, and brain energy metabolism, and therefore, insulin is suggested to be involved in various brain functions as well.
Central administration of insulin
Central administration of insulin is a method that specifically targets brain insulin receptors. In other words, it is an approach that allows for insulin to have direct effects on brain function and metabolism. Previous research indicates that central administration of insulin promotes neuroplasticity — the brain’s remarkable ability to adapt and change over time.
Additionally, central administration of insulin has been demonstrated to benefit cognitive functions in mouse models. However, it remains unclear whether central administration of insulin also has positive affects on human cognitive functions.
Current study
A recent systematic review and meta-analysis paper conducted by researchers from the University of Toronto and the Centre for Addiction and Mental Health sought to explore the effects of intranasal insulin (a form of central administration of insulin) on cognition in various populations. Intranasal insulin refers to the delivery of insulin through the nose (e.g., nasal spray), which allows insulin to directly bind with the brain’s olfactory receptors.
The study reviewed 26 randomized controlled trials involving diverse populations, including healthy individuals, patients with varying mental health disorders, Alzheimer’s disease, mild cognitive impairment, and metabolic disorders.
Notably, when examining studies focusing on Alzheimer’s disease and mild cognitive impairment, the researchers observed an improvement in global cognition with intranasal insulin administration. However, minimal to no effects on cognition were observed in the other populations assessed.
Future directions
This research opens avenues for further exploration, aiming to understand the mechanisms of insulin in the brain and potential interventions for neurodegenerative conditions. While further research is needed to establish the optimal protocols and long-term effects of intranasal insulin, the emerging evidence suggests promising outcomes in improving cognition, particularly in individuals with Alzheimer’s disease and mild cognitive impairment.
Continued exploration of insulin’s role in the brain may pave the way for innovative approaches to enhance cognitive health and potentially combat age-related cognitive decline. Perhaps intransal insulin administration will one day be used as a therapeutic treatment for Alzheimer’s disease, a condition that currently lacks a cure.
