Cognitive Dysfunction and Glucagon-like Peptide-1 Agonists

We propose to explore the effects of GLP-1 agonism on brain structure and function. We hypothesize that the administration of GLP-1 agonists may result in increased connectivity in the executive control network. Multiple clinical trials with pharmacological agents, as well as cognitive therapy, have reported that measurements of brain structure and function are correlated with cognitive performance, indicating that they are a valid biological correlate of cognitive function. To assess this hypothesis we will recruit a clinical population, represented by individuals with a measurable impairment in executive function, wherein the target of our proposed intervention was shown to be altered. We are currently not in a position to sufficiently homogenize subgroups of adults with mood disorder on the basis of any single or combinatorial biomarkers. It is also unlikely that alterations in GLP-1 receptor function, and the proposed model herein, is sufficiently explanatory to all sub-populations of adults with mood disorders. Instead, we propose that adults with mood disorders, who have co-existing metabolic disorders (e.g. type 2 diabetes mellitus), would be more likely to have a brain illness that is influenced by (i.e. cause, consequence or both) alterations in cellular bioenergetics. Moreover, convergent evidence suggest that GLP-1 receptor function may be, at least partially, dependent on glucose levels and/or insulin sensibility. It is a separate, yet testable, hypothesis that subpopulations enriched on the basis of having metabolic comorbidity (i.e. insulin resistance) may be more responsive to an intervention that targets a metabolic pathway. We plan to test the effects of adjunctive liraglutide on executive function. We will select a subpopulation of patients, with a mood disorder and impairment in executive function, as defined by a below-average (i.e. 1 standard deviation below norm) performance in the Trail Making Test-B (TMTB). Furthermore, we plan to recruit two groups of patients, with and without insulin resistance, as defined by a homeostatic model assessment for insulin resistance (HOMA-IR) above 2.5, which will allow a comparison of the effects of liraglutide in a metabolically heterogeneous population.