Vitamin E in diabetes-associated cognitive dysfunction: mechanistic rationale, current evidence and translational gaps.

Diabetes-associated cognitive dysfunction (DACD) is an increasingly recognized complication of diabetes mellitus and involves multiple interacting processes, including oxidative stress, neuroinflammation, synaptic dysfunction, impaired insulin signaling, and neurovascular dysfunction. Vitamin E, a lipid-soluble antioxidant comprising tocopherols and tocotrienols, has attracted interest because several of its biological actions are mechanistically relevant to these pathways. This mini-review provides a focused overview of the mechanistic rationale, current experimental and clinical evidence, and major translational gaps concerning vitamin E in DACD. Preclinical studies suggest that specific vitamin E isoforms and preparations may modulate oxidative stress and lipid peroxidation, inflammatory signaling and microglial activation, synaptic plasticity-related pathways, and insulin responsiveness, and may also influence neurovascular processes. However, much of this evidence derives from animal models, cellular systems, peripheral tissues, or disease settings other than DACD and therefore provides mechanistic rather than clinical efficacy evidence. Direct clinical evidence in patients with formally diagnosed DACD remains lacking. Small intervention studies in patients with type 2 diabetes have reported inconsistent cognitive outcomes, whereas observational associations between dietary vitamin E intake and cognition are largely derived from non-DACD populations and cannot establish causality. High-dose supplementation may also entail safety concerns. Thus, current evidence supports the biological plausibility of vitamin E as a candidate for further investigation but does not establish its preventive or therapeutic efficacy in DACD. DACD-specific randomized controlled trials are needed to determine whether particular vitamin E isoforms, doses, or intervention durations provide clinically meaningful cognitive benefits and to establish long-term safety.