Different Exercise Models Affect White Adipose Browning Through Mechanism Of Irisin Molecular Pathway

Abstract

BACKGROUND: The white adipose browning can improve fat burning and accelerate fat consumption. Irisin which is cleaved by Fibronectin Type III Domain-Containing protein 5(FNDC5) derived from muscle can act on white adipose tissue to promote the expression of Uncoupling Protein 1(UCP1). However,it is unclear which exercise models is better to contribute to produce Irisin. PURPOSE: To discuss whether High-Intensity Intermittent Exercise (HIIT) is better than Medium-Intensity Continuous Exercise (MICT) on the effect of improving white fat production of UCP1 and the mechanism of molecular biology. METHODS: Thirty-two 4-week-old C57BL/6J mice were fed with high-fat diet(D12492) for 8 weeks and randomly divided into three groups: control group (GC, n=8), MICT group (GM, n=8), and HIIT group (GH, n=8). Then, GM got an 8-weeks MICT training (10min warm-up, 45min 60%VO2max speed, 6 times/per week) and GH had an 8-weeks HIIT training (10min warm-up, 1set=1min 90%VO2max speed + 2min60%VO2max speed, 12sets). 24 hours after the last training, anesthesia was dissected. Muscle tissue contained PGC-1αmRNA, FNDC5mRNA, and Irisin. It was also taken by blood index. Irisin and UCP1mRNA were measured by subcutaneous white adipose tissue. The data were compared by using one-way analysis of variance. Results and Discussions: (1) Muscle: Comparing with GC, GM and GH both have a higher expression of PGC-1α mRNA but there is no significant difference, yet FNDC5mRNA of GM is more than GC(7.53±5.36 vs. 1.00±1.13, p<0.01) and GH(7.53±5.36 vs. 1.01±1.16, p<0.01). Irisin of GM(32.22±2.88 vs. 25.99±4.50 pg/mg, p<0.05) and GH(32.10±4.04 vs. 25.99±4.50 pg/mg, p<0.05) are more than GC. (2) Serum: The Irisin level of GH is very significantly higher than GM(55.41±1.19 vs. 51.83+2.47 pg/ml, p<0.01). (3) Subcutaneous white adipose tissue: In respect of Irisin, GH is more than GM (37.68+3.55 vs. 29.77+2.89 pg/mg, p<0.01); UCP1mRNA, GH is more than GM(16.67±6.65 vs. 0.69±0.42, p<0.01). CONCLUSION: (1) Exercise can promote the production of Irisin upstream regulated factor, PGC-1α and FNDC5. (2) HIIT compared with MICT has a greater effect on improving the white adipose tissue browning through the molecular pathway of PGC-1α- FNDC5 - Irisin - UCP1.