Editors' ChoiceDiabetes

Insulin: Food for Thought

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Science Translational Medicine  05 Mar 2014:
Vol. 6, Issue 226, pp. 226ec39
DOI: 10.1126/scitranslmed.3008712

Insulin is commonly prescribed to patients with type 2 diabetes to improve glycemic control, but what if insulin could also improve memory? Insulin is vital for glucose metabolism and critical for organism survival. Now, recent studies show that this hormone may also play an important role in optimizing cognitive function. Indeed, type 2 diabetes is a known risk factor for the development of dementia and Alzheimer’s disease, but the mechanisms for this phenomenon are not fully understood. One theory is that inadequate insulin delivery (or insulin resistance) in the brain may affect perfusion and neural activity in cognitive neurocircuitry. Novak et al. examined the effect of acute intranasal insulin administration on cognition and cerebral vasoreactivity in individuals with type 2 diabetes.

In a randomized, double-blind study, 15 individuals with type 2 diabetes (mean age 62) and 14 healthy individuals (mean age 60) received intranasal insulin or saline (placebo) on two separate random-order days. Vasoreactivity (vasodilatation to hypercapnea) and regional cerebral perfusion were assessed with magnetic resonance imaging, and neuropsychological testing was conducted to assess cognitive function. Acute administration of intranasal insulin improved visuospacial memory in both groups. Cognitive performance was related to regional vasoreactivity after insulin administration; specifically, improvement in visospatial memory in the group with type 2 diabetes was related to vasodilatation in the region of the middle cerebral artery. The authors suggest that administration of intranasal insulin may acutely improve cognitive function in individuals with type 2 diabetes, perhaps owing to improved vasoreactivity mechanisms (vasodilatation).

This proof-of-concept study provides evidence that in individuals with type 2 diabetes, intranasal insulin may play a role in acutely improving cognitive function. Certainly, larger studies must be conducted with administration of this medication over a longer period of time. Nevertheless, it is intriguing to speculate that intranasal insulin may be a potential pharmacologic agent for the improvement of cognitive function or perhaps for curtailing or slowing down of dementia in individuals with type 2 diabetes.

V. Novak et al., Enhancement of vasoreactivity and cognition by intranasal insulin in type 2 diabetes. Diabetes Care. 37, 751–759 (2014).[Abstract]

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