Större irisinsvar efter högintensiv träning jämfört med lågintensiv

[King Grub]

Irisin is mainly released from skeletal muscle (myocytes) and promotes thermogenesis by browning of the white adipose tissue. Although exercise has been shown to increase irisin concentration in blood and myocytes via up-regulation peroxisome proliferator receptor γ coactivator-1α (PGC-1α) expression, the influence of exercise intensity on irisin secretion remains unclear. Therefore, we determined circulating irisin responses following a single bout of running at different intensities. Six sedentary males underwent treadmill running under two different conditions: a low-intensity (40% of VO2max) exercise trial (LIE) or a high-intensity (80% of VO2max) exercise trial (HIE). The exercises in LIE and HIE were lasted for 20 and 40 min, respectively. All subjects underwent the two trials on separate days, and a randomized cross-over design was used. Blood samples were collected before (Pre) and immediately after exercise, at 3, 6, and 19 h after exercise. Energy consumption during exercise did not significantly differ between the two trials. HIE significantly increased blood lactate and serum lactate dehydrogenase levels (P < 0.05). Compared with pre-exercise levels, the irisin concentrations were elevated at 6 h (18% increase) and 19 h (23% increase) after HIE, but significantly decreased after LIE. The relative irisin concentrations (compared with pre-exercise levels) were significantly greater in HIE than in LIE immediately after exercise, and at 6 and 19 h after exercise (P < 0.05). These findings suggest that irisin secretion after acute running exercise is affected by exercise intensity, independent of energy consumption.

Tohoku J Exp Med. 2014;233(2):135-40. High-Intensity Exercise Causes Greater Irisin Response Compared with Low-Intensity Exercise under Similar Energy Consumption.

[King Grub]

Background: Irisin, a recently discovered myokine, has been shown to induce white adipose tissue browning, enhancing energy expenditure and mediating some of the beneficial effects of exercise. We aimed to estimate the timeframe of changes in irisin levels after acute exercise and the effect of different exercise workloads and intensities on circulating irisin levels immediately post-exercise. Methods: In a pilot study, four healthy subjects (22.5±1.7 years) underwent maximal workload exercise (maximal oxygen consumption, VO2max) and blood was drawn at pre-specified intervals to define the timeframe pre- and post-exercise irisin changes over a 24-hr period. In the main study, 35 healthy, non-smoking (23.0±3.3 years) men and women (n=20/15) underwent three exercise protocols ≥48-hr apart, in random order: 1-maximal workload (VO2max), 2-relative workload (70% of VO2max/10 minutes) and 3-absolute workload (75W/10 minutes). Blood was drawn immediately pre-, and 3 minutes post-exercise. Results: In the pilot study, irisin levels increased by 35% 3 minutes post-exercise, then dropped and remained relatively constant. In the main study, irisin levels post-exercise were significantly higher than pre-exercise after all workloads (all, P<.001). Post-to-pre-exercise differences in irisin levels were significantly different between workloads (P=.001), with the greatest increase by 34% following maximal workload (P=.004 vs. relative and absolute). Conclusions: Circulating irisin levels were acutely elevated in response to exercise, with a greater increase after maximal workload. These findings suggest that irisin release could be a function of muscle energy demand. Future studies need to determine the underlying mechanisms of irisin release and explore irisin's therapeutic potential.

Eur J Endocrinol. 2014 Jun 11. Plasma Irisin Levels Progressively Increase in Response to Increasing Exercise Workloads in Young, Healthy, Active Subjects.

[King Grub]

Rationale:

The newly discovered myokine irisin has been proposed to affect obesity and metabolism by promoting browning of white adipose tissue. However, clinical and functional studies on the association of irisin with obesity, muscle mass and metabolic status remain controversial. Here we assessed the effect of four distinct exercise regimes on serum irisin levels in children and young adults and systematically evaluated the influence of diurnal rhythm, anthropometric, and metabolic parameters and exercise on irisin.

Results:

Serum irisin levels did not show diurnal variations, nor were they affected by meal intake or defined glucose load during oral glucose tolerance testing (oGTT). Irisin levels decreased with age. In adults, irisin levels were higher in men than in women and obese subjects had significantly higher levels than lean controls. Irisin levels were closely correlated with muscle-associated bio-impedance parameters like fat-free-mass and body-cell-mass. Of four exercise regimens that differed in duration and intensity, we identified a clear and immediate increase in serum irisin levels after acute strenuous exercise (cycling ergometry) and a 30 minute bout of intensive exercise in children and young adults, whereas longer (six weeks) or chronic (one year) increase in physical activity did not affect irisin levels.

Summary:

We show that irisin levels are affected by age, gender, obesity, and particularly muscle mass, whereas diurnal rhythm and meals do not contribute to the variation in irisin levels. Short bouts of intensive exercise, but not long-term elevation in physical activity, acutely and transiently increase serum irisin levels in children and adults.

J Clin Endocrinol Metab. 2015 Jan 27. Serum irisin levels are regulated by acute strenuous exercise.

[svenbanan]

Okej. Vad innebär "browning of white adipose tissue"? Är det samma sak som att kroppsfettet görs om till muskler? ;)

[F Ultra]

Okej. Vad innebär "browning of white adipose tissue"? Är det samma sak som att kroppsfettet görs om till muskler? ;)

Snarare att vitt fett byts ut mot brunt fett. Om jag inte aktierseglar helt så genererar brunt fett värme medan vitt fett genererar energi.

[maqan]

Snarare att vitt fett byts ut mot brunt fett. Om jag inte aktierseglar helt så genererar brunt fett värme medan vitt fett genererar energi.

Enkelt beskrivet kan man säga att brun fettväv omvandlar energi direkt till värme medan vit fettväv istället lagrar energin för senare bruk.

[Snubben]

Snarare att vitt fett byts ut mot brunt fett. Om jag inte aktierseglar helt så genererar brunt fett värme medan vitt fett genererar energi.

Är det därför jag svettas som en stucken gris, bara brunt fett som alstrar värme varpå kroppen behöver kyla ner sig? ;)