Aberrancy in CNS Signals and other Factors Related to Altered Homeostasis, Obesity and Metabolic Syndrome

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Introduction: ‘The Obese-Obese World’: The obesity and metabolic syndrome (MetS) are a global epidemic of such magnitude that the today’s health scenario can be summed up as the ‘Obese-obese World’*. Obesity and MetS deteriorate quality of life and alter course of various chronic diseases, and on their own, are risk factors for diabetes, hypertension, cardiovascular disease and stroke, neurological degenerative diseases and cancers. Modern day lifestyle drives for excess calorie intake, comparatively reduced energy expenditure and storage of surplus energy in adipose tissue, an accentuated evolutionary need to fill body nutrients stores, leading to obesity, appended by pathophysiological alterations termed MetS. Cns Regulation of Energy Intake: Specialised neurons in hypothalamus and brainstem primarily regulate energy homeostasis, food intake and body weight, and integrate multiple peripheral metabolic inputs, such as nutrients, gut-derived hormones, and adiposity-related signals. There are several neuropeptides involved, including melanin concentrating hormone (MCH) and the orexins. An abnormal alteration in ghrelin and leptin levels can lead to weight gain and Obesity. Increase in adipose tissue leads to overproduction of leptin and hypothalamus becoming resistant to leptin action. The reward circuitry involves interactions between several systems including opioids, endocannabinoids, serotonin and dopamine. The obese individuals appear to have abnormalities in dopaminergic activity, and an imbalance in the brain circuits promoting reward seeking and those governing cognitive control leads to an overriding stimulus to feeding, even in the absence of an energy deficit. Dorsal striatum is hyperactive in obese and may contribute aberrancy of satiety signals. The genetics involving various mutations contributes up to 70% towards a person’s vulnerability to obesity. Regulation of Energy Expenditure: Energy is consumed in processes of physical activity, basal metabolism, and adaptive thermogenesis, which are modulated by brain, especially hypothalamic melanocortin system. Brown adipose tissue (BAT) plays a major role in thermogenesis. Central regulation of BAT thermogenesis is dependent on sympathetic outflow to BAT. Norepinephrine released from sympathetic nerve terminals binds to β3-adrenergic receptors on adipocytes in BAT to promote enhanced thermogenesis. In addition, many hormonal and nutrient signals, such as glucose, insulin, leptin and GLP-1 also influence sympathetic outflow to BAT. Conclusion - Fallouts of Neurosignal Aberrancy: The obese subjects with BMI > 30 show atrophy in the frontal lobes, anterior cingulate gyrus, hippocampus, and thalamus. MetS affects various cognitive domains including executive functioning, processing speed, and overall intellectual functioning. There is impaired vascular reactivity, endothelial dysfunction, neuro-inflammation, oxidative stress and altered brain metabolism.