Chronic neurodegenerative diseases are a group of devastating neurological disorders that result in significant morbidity and mortality in the elderly population worldwide. Recent researches have shown some interesting associations of the classical antiobesity hormone leptin with two most important neurodegenerative diseases—Alzheimer’s disease (AD) and Parkinson’s disease (PD). Although several clinical studies have found the procognitive and memory-enhancing role of this peptide hormone in leptin-deficient patients, surprisingly it has not been used in any clinical trials involving patients with developing or full-blown neurodegenerative conditions. This review article is an attempt to bring together the existing information about the clinical associations of leptin with AD and PD. It starts with the basic understanding of leptin action in the brain and its derangements in these diseases and eventually discusses the potential of this hormone as a neuroprotective agent in clinical scenario. 1. Introduction Aging-related chronic neurodegenerative diseases constitute a spectrum of neurological disorders characterized by a gradual loss of neuronal functions resulting from the toxicity of accumulated misfolded proteins [1–5]. Alzheimer’s disease (AD) and Parkinson’s disease (PD) are the two most common diseases of this group inflicting mostly the elderly population worldwide. These devastating disorders of neuronal dysfunctions are characterized by cognitive decline, memory loss, autonomic disturbances, and motor impairment [6–12]. By far, although a lot of theories and therapeutic targets have been identified underlying these debilitating diseases and various risk factors have been implicated in their pathogenesis, this spectrum of challenging disorders remains an enigma to the physicians and the scientists. Aging has been accredited as the major risk factor for neurodegeneration and recently much attention has been focused simultaneously on the possible role of obesity in the pathogenesis of this group of disorders [13–15]. A possible entangled relationship among obesity, aging, and neurodegeneration has also been proposed in many studies [14, 15]. Leptin is a polypeptide hormone involved significantly in the well-established role of regulation of energy homeostasis and neuroendocrine functions of our body via its action on the hypothalamus [16, 17]. Recent studies have found an interesting role of this hormone in various neurological functions like regulation of hypothalamic neuronal excitability, inhibition of hippocampal neurons, regulation of
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