Diabetes Mellitus and Energy Dysmetabolism in Alzheimer’s Disease: Understanding the Relationships and Potential Therapeutic Targets

Abstract: Over the last century, there has been a gradual but sustained increase in life expectancy globally. A consequence of increased life expectancy is an associated rise in the prevalence of agerelated chronic debilitating neurodegenerative disorders, such as Alzheimer's disease (AD), Parkinson's disease, Huntington's disease, and multiple sclerosis. These disorders, which are generally characterised by the loss of motor/sensory neurons and cognitive decline, have continued to confound researchers who are working tirelessly to define their pathogenetic mechanisms and develop effective therapies. In the last few years, there has been increasing evidence of the existence of a relationship between energy metabolism and neurodegeneration, with reports that type 2 diabetes mellitus increases the risk of AD. Evidence from preclinical and epidemiologic studies has associated dysmetabolism and dysmetabolic syndromes with the development of neurodegenerative changes. More recently, diabetes mellitus and energy dysmetabolism have been linked to the aetiopathogenesis of AD. Moreover, metabolic hormones, including ghrelin, leptin, insulin, and insulin-like growth factor (IGF)-1, have been reported to play key roles in the regulation of neuronal injury and loss in neurodegenerative diseases like AD. In this narrative review, we examine the current scientific evidence regarding the role of dysmetabolism (including diabetes mellitus and metabolic syndrome) in AD and how it impacts disease progression and the development of novel therapies in AD.