The Role Of β3-Adrenergic Receptor In High Intensity Interval Training Reducing Visceral Fat

Objective:This study aimed to compare the effects of high intensity interval training（HIIT）and moderate intensity continuous training（MICT）on the expression and function ofβ3-adrenergic receptors（β3-AR）in visceral adipocytes and to investigate the mechanism of visceral fat reduction by HIIT.Methods:Thirty-six female SD rats aged 7 weeks were randomly divided into sedentary high fat diet group（HFD）,moderate intensity continuous training group（MICT）and high intensity interval training group（HIIT）after 8 weeks of high fat feeding.MICT and HIIT groups received treadmill training（5 days per week）for 10weeks,and the HFD group remained sedentary with high fat diet.MICT:running speed corresponding to 50%～70%VO_2peak intensity,45min/day;HIIT:high intensity running for 1 min(85%～100%VO_2peak intensity)followed by low intensity exercise for 2 min(50%～70%VO_2peakintensity)repeatly.The total running distances of two groups were equal.After 10 weeks of intervention,body weight and the periuterine adipose tissue weight of the three groups were measured;HE staining was performed to calculate the mean area of visceral adipocytes;The expression ofβ3-AR protein in visceral adipose tissue was determined by western blot.Visceral adipocytes were isolated and stimulated with 0.1μM,1μM and 10μM isoprenaline respectively,to test visceral adipocyte glycerol release;The protein immunoblotting was used to test visceral adipocyte HSL phosphorylation（Phospho-HSL,p-HSL）expression.In addition,β3-AR selective antagonist SR59230A was added to 10μM of isoprenaline to test the glycerol release from visceral adipocytes.Results:（1）The effects of two types of training on body weight,adiposity and visceral adipocyte area（1）At the end of 10 weeks of intervention,the mean body weight of rats in both MICT and HIIT groups were lower than that of HFD group（p<0.01）,and there was no significant difference between the body weight of rats in MICT and HIIT groups（p>0.05）.（2）The weight of periuterine adipose tissue were lower in MICT and HIIT groups than in HFD group（p<0.05 or p<0.01）,while there was no statistical difference between the two exercise groups（p>0.05）.（3）The mean visceral adipocyte area was significantly lower in both the MICT and HIIT groups than that in HFD group（p<0.05）,while there was no statistical difference between the two exercise groups.（p>0.05）.（2）The effects of two types of training onβ3-AR protein expression in visceral adipose tissueAfter 10 weeks intervention,the expression ofβ3-AR protein in periuterine adipose tissue was higher in both MICT and HIIT groups than that in HFD group（p<0.05 or p<0.01）;there was no statistical difference between the MICT and HIIT groups（p>0.05）.（3）The effects of two types of training on catecholamine sensitivity in visceral adipocytes（1）The main effect of"exercise"on glycerol release in periuterine adipocytes was significant（p<0.05）,while the main effect of"concentration"was not significant,and there was no significant effect between"exercise"and"concentration".The glycerol release in HIIT group was significantly higher than that in MICT and HFD groups（p<0.05）,while there was no statistical difference between MICT and HFD groups（p>0.05）.（2）After stimulation with 10μM isoprenaline,p-HSL protein expression in visceral adipocytes was higher in both MICT and HIIT groups than in HFD group（p<0.05 or p<0.01）.The p-HSL protein expression in visceral adipocytes was higher in the HIIT group than in MICT group（p<0.05）.（4）Validation of the role ofβ3-AR in HIIT induced elevated catecholamine sensitivity in visceral adipocytesTheβ3-AR selective antagonist SR59230A impaired the glycerol release stimulated by 10μM Isoprenaline in HIIT group（p<0.05）,and this was not shown in MICT and HFD groups.Conclusion:HIIT inhibits visceral fat accumulation in high-fat diet rats,andβ3-AR plays an important role in HIIT in improving the sensitivity of visceral fat cells to catecholamines and promoting lipolysis.