Work

Cognitive demand as a neurometabolic stress test in diabetes-associated cognitive impairment: from static metabolite pools to dynamic energy responses

Year: 2026

Type: review

Abstract: Background: Diabetes-associated cognitive impairment (DCI) is heterogeneous and cannot be explained by chronic hyperglycaemia or isolated resting metabolic abnormalities. Measurements of transporter abundance, metabolite pools, perfusion, or functional endpoints alone do not determine whether the brain can dynamically recruit energetic support when cognitive demand increases. Objective: To conceptualize cognitive demand as a neurometabolic stress test, distinguish static metabolic states from dynamic adaptive responses, and establish a falsifiable framework for activity-dependent neurometabolic failure in DCI. Methods: This concept-driven critical review used an iterative PubMed/MEDLINE-centred search updated through August 2026, supplemented by backward and forward citation tracking. Evidence was organized along the demand-to-function pathway, encompassing cognitive-task, glucose/insulin, hypoglycaemic or alternative-substrate, and neural/network challenges. Studies were prioritized when they provided information on temporal dynamics, pathway flux, cellular or regional specificity, or causal perturbation. Results: Normal cognitive function requires coordinated recruitment of vascular delivery, substrate mobilization and allocation, oxidative metabolism, phosphotransfer buffering, and ATP turnover, even when metabolite and high-energy phosphate pools remain relatively stable. Evidence from diabetes and insulin resistance demonstrates heterogeneous, challenge-dependent abnormalities that may involve reduced response amplitude, temporal misalignment, altered substrate distribution, or impaired metabolic utilization rather than uniform cerebral hypometabolism. We propose four non-exclusive within-challenge phenotypes of neurometabolic failure: blunted recruitment, mistimed recruitment, substrate misallocation, and malutilization. Neurometabolic reserve denotes recruitable adaptive capacity; its exhaustion is considered a longitudinal contraction of that capacity, not a fifth within-challenge phenotype or a conclusion warranted by a single attenuated response. However, current evidence has not yet established a complete causal chain linking cognitive demand, substrate fate, energetic support, neural computation, and cognitive performance in clinically characterized DCI. Conclusions: We propose cognitive demand as an experimental neurometabolic stress test for investigating metabolic vulnerabilities that may remain undetected at rest, rather than as a validated clinical diagnostic test. Activity-dependent neurometabolic failure should therefore be considered a testable contributor rather than an established universal mechanism of DCI. Future studies integrating challenge-locked, temporally aligned, and compartment-resolved metabolic measurements with causal perturbation and longitudinal assessment are required to define when endocrine-metabolic dysfunction translates into cognitive vulnerability.

Source: Frontiers in Endocrinology

DOI: 10.3389/fendo.2026.1991245