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Neuroendocrine Deregulation of Food Intake, Adipose Tissue and the Gastrointestinal System in Obesity and Metabolic Syndrome

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Gabriella Garruti1, Susanna Cotecchia2, Federica Giampetruzzi1, Francesco Giorgino1, Riccardo Giorgino1

1) Unit of Internal Medicine, Endocrinology and Metabolic Diseases - Department of Emergency and Organ Transplantations (D.E.T.O.), University of Bari Medical School, Italy;
2) Department of General and Environmental Physiology, University of Bari, Italy and Département de Pharmacologie et de Toxicologie, Université de Lausanne, Suisse


Abstract

Obesity is an excess of fat mass. Fat mass is an energy depot but also an endocrine organ. A deregulation of the sympathetic nervous system (SNS) might produce obesity. Stress exaggerates diet-induced obesity. After stress, SNS fibers release neuropeptide Y (NPY) which directly increases visceral fat mass producing a metabolic syndrome (MbS)-like phenotype. Adrenergic receptors are the main regulators of lipolysis. In severe obesity, we demonstrated that the adrenergic receptor subtypes are differentially expressed in different fat depots. Liver and visceral fat share a common sympathetic pathway, which might explain the low-grade inflammation which simultaneously occurs in liver and fat of the obese with MbS. The neuroendocrine melanocortinergic system and gastric ghrelin are also greatly deregulated in obesity. A specific mutation in the type 4 melanocortin receptor induces early obesity onset, hyperphagia and insulin-resistance. Nonetheless, it was recently discovered that a mutation in the prohormone convertase 1/3 simultaneously produces severe gastrointestinal dysfunctions and obesity.

Key words
Obesity - sympathetic nervous system - metabolic syndrome - adrenergic receptors - prohormone convertase 1/3 - type 4 melanocortin receptor