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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: 11 Jan 2009 17:22 Naslov sporočila: Aerobna vadba boljša pri zaviranju apetita kot brez nje |
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60-minutna aktivnost vpliva na sprostitev dveh ključnih hormonov apetita, grelin in peptid YY, medtem ko se 90 minut aktivnost vpliva na dviganje ravni le grelin, glede na nove študije. Če povzamemo; raziskave kažejo, da je aerobna telovadba boljša pri zaviranja apetita kot brez aerobne vadbe in določa možno razlago o tem, kako se to zgodi.
This line of research may eventually lead to more effective ways to use exercise to help control weight, according to the senior author, David J. Stensel of Loughborough University in the United Kingdom.
Treadmill versus weight lifting
There are several hormones that help regulate appetite, but the researchers looked at two of the major ones, ghrelin and peptide YY. Ghrelin is the only hormone known to stimulate appetite. Peptide YY suppresses appetite.
Ghrelin was discovered by researchers in Japan only about 10 years ago and was originally identified for its role as a growth hormone. Only later did its role in stimulating appetite become known. Peptide YY was discovered less than 25 years ago.
In this experiment, 11 male university students did three eight-hour sessions. During one session they ran for 60 minutes on a treadmill, and then rested for seven hours. During another session they did 90 minutes of weight lifting, and then rested for six hours and 30 minutes. During another session, the participants did not exercise at all.
During each of the sessions, the participants filled out surveys in which they rated how hungry they felt at various points. They also received two meals during each session. The researchers measured ghrelin and peptide YY levels at multiple points along the way.
They found that the treadmill (aerobic) session caused ghrelin levels to drop and peptide YY levels to increase, indicating the hormones were suppressing appetite. However, a weight-lifting (non-aerobic) session produced a mixed result. Ghrelin levels dropped, indicating appetite suppression, but peptide YY levels did not change significantly.
Based on the hunger ratings the participants filled out, both aerobic and resistance exercise suppressed hunger, but aerobic exercise produced a greater suppression of hunger. The changes the researchers observed were short term for both types of exercise, lasting about two hours, including the time spent exercising, Stensel reported.
“The finding that hunger is suppressed during and immediately after vigorous treadmill running is consistent with previous studies indicating that strenuous aerobic exercise transiently suppresses appetite,” Stensel said. “The findings suggest a similar, although slightly attenuated response, for weight lifting exercise.”
Focus on active ghrelin
Previous studies have been inconclusive about whether exercise decreases ghrelin levels, but this study may help explain those mixed results, according to the researchers.
Ghrelin comes in two forms, acylated and non-acylated. The researchers measured acylated ghrelin, also called active ghrelin, because it can cross the blood-brain barrier and reach the appetite center in the brain. Stensel suggests that future research concentrate on active ghrelin.
While the study showed that exercise suppresses appetite hormones, the next step is to establish whether this change actually causes the suppression of eating.
Vir: Broom et al. The influence of resistance and aerobic exercise on hunger, circulating levels of acylated ghrelin and peptide YY in healthy males. AJP
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Mitch
Administrator foruma
Pridružen/-a: 11.09. 2008, 06:27
Prispevkov: 2136
Kraj: Nova Gorica
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| Objavljeno: 13 Jan 2009 10:31 Naslov sporočila: |
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Grelin in peptid YY sta gastrointestinalna hormona.
Grelin se v največji meri izloča iz oksintičnih celic želodca, v majhnih količinah pa tudi iz dvanajstnika, ozkega črevesa in debelega črevesa. Je endogeni ligand sekretornih receptorjev rastnega hormona (GHS-R) tipa 1a v hipotalamusu, ter tako povzroči izločanje rastnega hormona v hipofizi. Sestavlja ga 28 aminokislin, na kislinskem delu peptida pa ima vezano n-oktanojsko kislino. Oktanojska kislina je ključna za vezavo na GHS-R in njegov učinek na hranjenje.
Koncentracija plazemskega grelina je regulirana preko endogenega dnevnega ritma in vnosa hrane. V človeškem telesu nivo grelina niha skupaj z dnevnim nihanjem leptina, ki je visok zjutraj in nizek ponoči. Pri ljudeh, ki se hranijo ob enakih časih, je koncentracija grelina v krvi največja, ko so tešči in pade po jedi. Znižanje po jedi je regulirano tako z vnosom energije (kalorije) kot tudi s kroženjem hranljivih snovi po krvi (npr. glukoza).
Zanimivo je, da nivo plazemskega grelina ne pade po pitju vode, torej raztegnitev želodca ne zavira sproščanje grelina. Po drugi strani so visoke plazemske količine grelina opazili pri ljudeh z anoreksijo in kaheksijo ter ob pomanjkanju spanja. Zanimivo, da količino grelina poviša že samo pričakovanje hranjenja.
Peptid YY (PYY) izločajo L-celice GI-trakta (gastrointestinalni trak) in sicer v največjih količinah distalni deli le-tega (ileum, colon in rectum). Sproščanje PYY v krvni obtok je pogojeno s kalorično vrednostjo in količino zaužite hrane. Pri vnosu maščob v telo se v krvni obtok sprosti več PYY kot pri energetsko enaki količini ogljikovih hidratov ali beljakovin. Sproščanje vzpodbujajo še: želodčna kislina, holecistokinin (CCK) in soli žolčnih kislin, zavira pa ga GLP-1 (glukagonu-podoben peptid), medtem ko napetost želodca ne vpliva na sproščanje. Do izločanja PYY pride že zelo kmalu po vnosu hrane, preden pridejo hranila v stik z L-celicami GI-trakta. Znanstveniki predvidevajo, da začetno izločanje PYY sprožijo drugi nevralni refleksi, ki so povezani s samim pričakovanjem hranjenja.
V krvnem obtoku PYY obstaja v dveh glavnih oblikah: PYY1-36 in PYY3-36. PYY3-36 se v največji meri veže na presinaptične inhibitorne Y2 receptorje v arkuatnem jedru hipotalamusa, ki nato inhibirajo delovanje NPY/AgRP nevronov (NPY-nevropeptid Y; AgRP-agutiju soroden peptid). Tako zavira željo po hranjenju. Periferno zavira praznjenje želodca, zavira želodčno in pankreatično izločanje ter vzpodbuja absorpcijo tekočine in elektrolitov.[1]
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E-mail: triatlon.moci@gmail.com
Nazadnje urejal/a Mitch 13 Jan 2009 10:54; skupaj popravljeno 1 krat |
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Mitch
Administrator foruma
Pridružen/-a: 11.09. 2008, 06:27
Prispevkov: 2136
Kraj: Nova Gorica
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| Objavljeno: 13 Jan 2009 10:36 Naslov sporočila: |
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Leptin (grško: leptos, kar pomeni vitek) je polipeptidni hormon sitosti, ki zavira vnos hrane, poveča energijsko porabo in termogenezo (s tem pospešuje izgubo teže). Njegova primarna ekspresija in sekrecija potekata v belem adipoznem tkivu, deloma se izloča tudi v želodcu, placenti in skeletnih mišicah. Med funkcije leptina spadajo:
-vpliv na homeostazno ravnotežje,
-sodeluje pri normalnem spolnem dozorevanju in reprodukciji,
-sodeluje pri metabolizmu glukoze in lipidov,
-delna kontrola imunskega odziva,
-interakcija z nevroendokrinimi peptidi in rastnim hormonom.
Leptin in njegovo delovanje
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