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Mitch
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Pridružen/-a: 11.09. 2008, 06:27
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Kraj: Nova Gorica
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 Objavljeno: 29 Avg 2011 10:12 Naslov sporočila: Prosti radikali v hipotalamusu zaviranjo apetit |
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Debelost se povečuje z zaskrbljujočo hitrostjo po vsem svetu in največji krivec je prenajedanje. V študiji, ki so jo napravili na možganih, ki so ugotavljali nadzor lakote in sitosti, so ugotovili, da so molekularni mehanizmi nadzora prostih radikalov (molekul, vezanih na staranje in poškodbe tkiva) povezani z povečavo apetita v prehrani, ki povzroča debelost.
Ta slika prikazuje spodbujanje sitosti melanocortin nevronov (zelena) v hipotalamusu, od katerih so nekateri aktivirajo (rdeča jedra) po zdravljenju. (Tamas Horvath, Yale University)
V študiji, ki je bila objavljena v spletni izdaji Nature Medicine, dne 28. avgusta je pokazala, da dvig ravni prostih radikalov v hipotalamusu neposredno ali posredno zavira apetit pri debelih miših z aktiviranjem sitosti, spodbujajo melanocortin nevroni. Prosti radikali pa so, prav tako mislil, da vozi proces staranja.
Published Aug. 28 in the advanced online issue of Nature Medicine, the study found that elevating free radical levels in the hypothalamus directly or indirectly suppresses appetite in obese mice by activating satiety-promoting melanocortin neurons. Free radicals, however, are also thought to drive the aging process.
"It's a catch-22," said senior author Tamas Horvath, the Jean and David W. Wallace Professor of Biomedical Research, chair of comparative medicine and director of the Yale Program on Integrative Cell Signaling and Neurobiology of Metabolism. "On one hand, you must have these critical signaling molecules to stop eating. On the other hand, if exposed to them chronically, free radicals damage cells and promote aging."
"That's why, in response to continuous overeating, a cellular mechanism kicks in to suppress the generation of these free radicals," added lead author Sabrina Diano, associate professor of Ob/Gyn, neurobiology and comparative medicine. "While this free radical-suppressing mechanism -- promoted by growth of intracellular organelles, called peroxisomes -- protects the cells from damage, this same process will decrease the ability to feel full after eating."
After the mice ate, the team saw that the neurons responsible for stopping overeating had high levels of free radicals. This process is driven by the hormone leptin and glucose, which signal the brain to modulate food intake. When mice eat, leptin and glucose levels go up, as does free radical levels. However, in mice with diet-induced obesity, these same neurons display impaired firing and activity (leptin resistance); in these mice, levels of free radicals were buffered by peroxisomes, preventing the activation of these neurons and thus the ability to feel sated after eating.
According to Horvath and Diano, the crucial role of free radicals in promoting satiety as well as degenerative processes associated with aging may explain why it has been difficult to develop successful therapeutic strategies for obesity without major side effects. Current studies address the question of whether, under any circumstance, satiety could be promoted without sustained elevation of free radicals in the brain and periphery.
The study was supported by grants form the National Institutes of Health and the American Diabetes Association.
Vir: Yale University (2011, August 28 ). Free radicals crucial to suppressing appetite. ScienceDaily. Retrieved August 29, 2011, from http://www.sciencedaily.com /releases/2011/08/110828140931.htm?utm_source=feedburner&utm_medium=email&utm_campaign=Feed%3A+sciencedaily%2Fhealth_medicine%2Fdiet_and_weight_loss+%28ScienceDaily%3A+Health+%26+Medicine+News+--+Diet+and+Weight+Loss%29
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