Outcomes and clinical implications of intranasal insulin on cognition in humans: A systematic review and meta-analysis

Abstract

Background Aberrant brain insulin signaling has been posited to lie at the crossroads of several metabolic and cognitive disorders. Intranasal insulin (INI) is a non-invasive approach that allows investigation and modulation of insulin signaling in the brain while limiting peripheral side effects. Objectives The objective of this systematic review and meta-analysis is to evaluate the effects of INI on cognition in diverse patient populations and healthy individuals. Methods MEDLINE, EMBASE, PsycINFO, and Cochrane CENTRAL were systematically searched from 2000 to July 2021. Eligible studies were randomized controlled trials that studied the effects of INI on cognition. Two independent reviewers determined study eligibility and extracted relevant descriptive and outcome data. Results Twenty-nine studies (pooled N = 1,726) in healthy individuals as well as those with Alzheimer’s disease (AD)/mild cognitive impairment (MCI), mental health disorders, metabolic disorders, among others, were included in the quantitative meta-analysis. Patients with AD/MCI treated with INI were more likely to show an improvement in global cognition (SMD = 0.22, 95% CI: 0.05–0.38 p = <0.00001, N = 12 studies). Among studies with healthy individuals and other patient populations, no significant effects of INI were found for global cognition. Conclusions This review demonstrates that INI may be associated with pro-cognitive benefits for global cognition, specifically for individuals with AD/MCI. Further studies are required to better understand the neurobiological mechanisms and differences in etiology to dissect the intrinsic and extrinsic factors contributing to the treatment response of INI.

Mechanism of traditional Chinese medicine in elderly diabetes mellitus and a systematic review of its clinical application

“…Studies have found that impaired brain insulin-PI3K-AKT signaling may promote neurodegeneration in Alzheimer’s disease (AD) by downregulating O-GlcNAcylation, subsequently promoting abnormal tau hyperphosphorylation and neurofibrillary degeneration ( Liu et al, 2011b ). Intravenous or intranasal insulin administration has improved memory function in both humans and animals ( Chapman et al, 2018 ; Wu et al, 2023b ), indicating that compromised insulin signaling pathways may be a primary defect linking AD and T2D.…”