Impaired inflammatory response and extracellular matrix(ECM) remodeling can restrict adipose tissue expansion, increasing fatty acid accumulation in ectopic tissues and insulin resistance. Exercise is beneficial to metabolic health but, there are few studies examining its effect on adipose tissue ECM accumulation. In our high fat diet(HFD) model we investigated the effect of exercise on ECM in subcutaneous(SAT), epididymal(EPI) and brown adipose tissue(BAT) depots.
We implemented isocaloric exercise programs (Endurance(ENDU) and High intensity interval training(HIIT)) for HFD(45% fats) and chow C57BL/6 mice fed ad libitum for 10 weeks(3sessions/week 40 min).
Both exercise programs reduced HFD changes in weight (final weight (gm)Chow=32±2;HFD=45±2;ENDU=37±2;HIIT=36±2), fat mass (total, SAT, EPI and BAT) and improved the insulin sensitivity(insulin tolerance test (HFD=411±54;ENDU=350±57; HIIT=320±66 a.u.)). ECM accumulation was prevented in SAT and EPI by exercise programs where gene expression of Collagen VI and its regulators TGFβ, CTGF, TIMP1, TIMP3 were lower than unexercised HFD (in SAT~4-15 fold by ENDU and 3-7 fold by HIIT; in EPI~2-4 fold by ENDU and HIIT). Exercise normalized these parameters to chow in SAT but not in EPI(~2-5 fold higher). The expression of PPARγ and Adiponectin were similar to chow in HFD SAT and EPI, consistent with an effect of exercise and an increase in exercise induced spontaneous physical activity(HFD=211±59;ENDU=308±76;HIIT=304±77 a.u.) and energy expenditure(kcal/kg0.75*h). In SAT exercise reduced inflammatory markers(TNFα and MCP1) and was comparable to chow. However in EPI, despite the reduction in inflammatory markers by 8-fold in ENDU and 4-fold in HIIT compared to HFD, it was higher than chow(~4-11 folds). In BAT minimal changes were observed.
There were significant differences between the adipose tissue depot responses to different exercises. But, a protective role of exercise in the metabolic parameters controlling body weight, adipose tissue ECM accumulation and inflammatory response were seen in all the fat depots.