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Appettite regulation Magdalena Warchoł, Msc, PhD Department of Physiology Plan of what you will know after class What is appetite? Brain control of appetite Hormones that regulate appetite, and their basic modes of action Other factors regulating food intake How is it in obesity? Why do we eat? Energy hemeostasis CARBOHYDRATES PROTEINS FATS • FOOD INTAKE metabolism • ENERGY BODY FUNCTIONS STORE • UNDERNUTRION /OBESITY The use of consumed food 73% HEAT protein metabolism, muscles activity 27% for cells activities of various organs and tissues of the body Energy balance is the key What are adipocytes? Adipose tissue is an anatomical term for loose connective tissue composed of fat storing cells (adipocytes) White adipose tissue - store fatty acids in the form of triglycerides food reserve - thermally insulates the organism - like any tissue - source of first messengers (hormones and cytokines) that diffuse into the body Leptin is produced by adipose tissue Adipocytes also produce: inflammatory cytokines: TNF-α and IL-6 - an excess of adipose tissue - chronic mild inflammatory state referred to as the “metabolic syndrome” - an excess of fully loaded adipocytes the release of free fatty acids - rise to insulin resistance contributing to the late onset diabetes (type II) in obese people Obesity and leptin 9.3 calories of excess energy - 1 gram of fat is stored studies have shown that new adipocytes can differentiate from fibroblast-like preadipocytes at any period of life An extremely obese person - 4x adipocytes, each containing 2x more lipids How much food do we need? variability in the amount of energy storage (i.e., fat mass) an adequate energy supply is necessary for survival powerful physiological control systems - adequate energy intake deficits of energy stores activate mechanisms that cause hunger athletes 6000/7000 kcal/day Sedentary individuals 2000kcal/day Appetite Appetite – desire for food, felt as hunger • Regulate adequate energy intake to maintain metabolic needs Appetite is different from hunger • Hunger – physical need to eat When we lose weight – our body response is to conserve energy and boost appetite – yo-yo effect The Hypothalamus Contains Hunger and Satiety Centers Control of food intake • Lateral nuclei of the hypothalamus – hunger center • Stimulation of this area – hyperphagia • Destruction of LHA - inanition • Ventromedial nuclei/paraventricular nuclei – satiety center • Stimulation – aphagia • Destruction – voracious eating THIS CENTERS REGULATES FOOD INTAKE AND ENERGY EXPENDITURE hunger FROM: Gross P., Jean-Baptiste F., Siba Lemba T.A., Zoror K., Singaling by ghrelin, insulin and leptin in hyphothalamus. Obesity Project 2009 – Universite Bordeaux. Feedback mechanisms for control of food intake 1. Neural signals from gastrointestinal tract – sensory information about stomach filling 2. Chemical signals from nutrients in the blood – glucose, amino acids, fatty acids – signify satiety 3. Signals from gastrointestinal hormones 4. Signals from hormones released by adipose tissue 5. Signals from the cerebral cortex - sight, smell, taste The hypothalamic melanocortin system • POMC neurons release α- MSH • α- MSH acts on melanocortin receptors(MCR) • at least 5 subtypes of MCR exist • MCR-3 and MCR-4 – important in food intake • reduced food intake, increased energy expenditure • increased food intake, reduced energy expenditure • mutations of MCR-4 – most common genetic cause of obesity, 5-6% severe obesity in children • excesive activation – may be associated with anorexia Regulation of the Quantity of Food Intake short-term – prevents overaeting at each meal Gastrointestinal Filling Inhibits Feeding Mechanoreceptors and Chemoreceptors of gastrointestinal tract Leptin-Ghrelin „tango” „oral factors” long-term – maintains energy stores in body Fat stores – leptin from adipocytes Glucose metabolism - Insulin from β-cells Ghrelin – when the fat stores are too low Why do we need both, short- and long-term regulation? LONG-TERM SHORT-TERM • maintain constant stores of nutrients in the tissues • preventing from being too low or too high • eating the right amount at each meal • prevent from eating too much important for metabolic storage systems Grelin mainly released by oxintic cells of stomach Blood levles rise during fasting Peak just before eating rapidly after meal Orexigenic hormone The physiological role – still discussed, some studies about ghrelin role in the early development Tacheoesophageal fistula food intake inhibition despite the gastrointestinal tract is not filled at all „oral factors” – chewing, salivation, swallowing, tasting – measure food intake After a certain amount passes – hypothalamic feeding centers are inhibited Intermediate- and long-term regulation – energy stores can modulate food intake at meal Long-term regulation - summary When the energy stores of the body fall below normal, the feeding centers of the hypothalamus and other areas of the brain become highly active, and the person exhibits increased hunger, as well as the behavior of searching for food. Conversely, when the energy stores (mainly the fat stores) are already abundant, the person usually loses the sensation of hunger and develops a state of satiety. Thank you for your attention!