oa Editorial (Thematic Issue: Linkage of Neurodegenerative Disorders with Other Health Issues – Volume I)

Neurodegenerative disorders encompass a spectrum of illnesses, such as Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, and even schizophrenia, autism and potential mood disorders [1]. In parallel with this, a number of metabolic disorders – largely brought together under the term, metabolic syndrome (a conglomerate of several conditions, such as glucose intolerance/insulin resistance, hypertension, obesity, and dyslipidemia that, as a collection, elevate the risk of developing type 2 diabetes and cardiovascular diseases) - can negatively impact human health and life span dramatically. Type 2 diabetes, like cardiovascular and neurodegenerative diseases, tends to progressively affect people as they age, particularly those with genetic and epigenetic pre-dispositions. Furthermore, like a number of other conditions, type 2 diabetes is clearly associated with over-nutrition and physical inactivity [2]. Affected individuals can be distinguished by a defect in insulin secretion together with a reduced response to insulin-stimulated glucose uptake in target tissues, including liver and adipose tissues - a disorder termed insulin resistance. With insulin secretion no longer able to compensate for rising peripheral insulin demand, the prediabetic state advances to diabetes and, although multiple mechanisms clearly underlie defective insulin secretion and resistance (for example, glucotoxicity, oxidative stress, lipotoxicity, endoplasmic reticulum stress, changes in gut microbiota, and others) [2], the contributions of each remain largely unknown and these same mechanisms can impact and induce dysfunction in other body systems – including the brain. It is widely accepted that neurodegenerative disorders, type 2 diabetes and cardiovascular diseases are debilitating disorders impacting over one hundred million persons across the globe, regardless of continuous new discoveries in science and technology [3]. It is becoming increasingly clear that all of these disorders - and the aberrant biochemical cascades occurring in each - have the potential to promote the other disorders; and hence special attention is required by medical scientists to understand and develop strategies to remedy this. More and more links are being found almost daily between environmental factors, obesity, oxidative stress, inflammation, systemic maladies and central nervous system disorders like Alzheimer's disease, Parkinson's disease, Huntington's and even some cancers [4-8] (Fig. 1). With this at the forefront, the current thematic issue of CNS & Neurological Disorders - Drug Targets was developed, and contributing authors were requested to shed light on important features deemed critical - like abnormalities in the level of key enzymes, hormones, peptides, inflammatory modulators, microbiota, bacterial/viral infections and the insulin signaling system in their articles (whether a review, original research, case report or letter). In this way, this special issue of CNS & Neurological Disorders - Drug Targets will hopefully move towards a greater understanding of the linkage between neurodegenerative conditions and other disorders with respect to cellular, molecular neurobiology, genetics, drug development and clinical aspects to promote progress towards effective management strategies for neurodegenerative disorders.On a personal level, I wish to end this editorial by thanking Stephen D. Skaper, the Editor in Chief, as well as Hina Wahaj, the Managing Editor, and all the contributing authors who have passionately responded to my request to provide interesting articles (Table 1). I additionally extend my thanks to all peer reviewers for their time and expertise in revising individual contributions to a consistently high level of excellence. Finally, I am grateful to Nigel H. Greig (Drug Design & Development Section, Intramural Research Program, National Institute on Aging, National Institute Health, USA) for kindly editing this ‘editorial article’ and for his continuous support in relation to my own research journey in Alzheimer's disease and type 2 diabetes.