Comparative effect of high intensity interval training and moderate intensity continuous training on metabolic improvements and regulation of Cidea and Cidec in obese C57BL/6 mice.

Obesity is a chronic disease associated with increased risk of cardiovascular disease, diabetes, metabolic dysfunction associated steatotic liver disease and certain cancers. High intensity interval training (HIIT) and moderate intensity continuous training (MICT) are effective in preventing and managing obesity. However, the comparative effects of these modalities on metabolic disorders need to be better mechanistically explored. This study aimed to comprehensively assess the effects of MICT and HIIT on key metabolic organs and underlying mechanisms. C57BL/6 mice were randomized to receive either a chow diet or high fat diet for 12 weeks, followed by random assignment of high-fat-fed mice to no exercise, MICT or HIIT groups for additional 5 weeks. At the end, both HIIT and MICT significantly alleviated high-fat-induced weight gain and lipids disorder and impaired liver function. HIIT was more effective in enhancing insulin sensitivity, ameliorating hepatic steatosis, reducing adipocyte hypertrophy. Additionally, HIIT restored the high-fat-induced downregulation of Cidea, Cidec and Atgl in inguinal white adipose tissue and liver. Furthermore, HIIT resulted in upregulation of interleukin 6 (Il-6) in skeletal muscle. The exogenous addition of Il-6 to primary white adipocytes significantly downregulated Cidec, and up-regulated Atgl expression. In conclusion, HIIT is superior to MICT in improving metabolic dysfunction, likely mediated through Il-6-induced downregulation of Cidea and Cidec, thereby promoting lipolysis.