Cognitive impairment in diabetes mellitus and its management by transcription factor Nrf2-mediated antioxidant defense system

Diabetes mellitus has been an epidemic in the twenty-first century and an approximately 50% risk of diabetes predisposed to cognitive decline leading to dementia in humans. There is an urgent need to understand the pathophysiology and identify molecular targets of cognitive impairment in diabetes mellitus that might lead to improved therapy. Mounting evidence indicates that nuclear factor erythroid 2-related factor 2 (Nrf2) and its regulated downstream antioxidant genes are emerging therapeutic targets. In this chapter, we introduce cognitive dysfunction in diabetes mellitus and its hallmarks, particularly its pathological mechanisms related to oxidative stress in the brain, then justify the role of the transcription factor Nrf2-mediated antioxidant defense system in attenuating cognitive decline in diabetes mellitus. Studies on Nrf2 inducers sourced from natural products (i.e., sulforaphane, astaxanthin, resveratrol, quercetin) that have shown potent cognitive improvement in diabetic models are discussed. These studies have demonstrated that Nrf2 inducers drive the antioxidant and anti-inflammatory responses in the hippocampus region and effectively improve the spatial and memory function in diabetic rats/mice. However, evidence from large and well-designed clinical trials is warranted to support Nrf2 inducers as promising therapeutic agents in the management of cognitive impairment in diabetes mellitus.