Exercise training prevents high-fat diet-induced adipose tissue remodeling by promoting capillary density and macrophage polarization

Increasing adipose tissue capillarization is beneficial to metabolic health. The present study examined the effects of continuous training (CT) and aerobic-interval training (AIT) coinciding with a high-fat diet (HFD) on capillary density, macrophage polarization in mesenteric (mAT) and subcutaneous (sAT) adipose tissue. 48 male Wistar rats were divided into HFD and normal diet (ND) groups. After 10 weeks, each group was divided into sedentary, CT, and AIT. The animals in training groups performed 10-week matched distances of CT and AIT on a motorized treadmill (5 times/week). The results showed that HFD significantly reduced the capillary density of adipose tissue (sAT: 54% vs. mAT:49%) and increased systemic insulin resistance, mean adipocyte size, crown-like structure (CLs), and M1-macrophages with no change in the total number of adipocytes in either tissue. Exercise training reversed the HFD induced adipose tissue dysfunction. Compared to CT, AIT was more effective on increasing the capillary density of sAT (170 vs. 87%) and mAT (140 vs. 100%). Likewise, AIT increased the capillary density of both tissues even in comparison to the ND sedentary group (~25%). Compared with CT as well, AIT more significantly increased the number of M2 macrophages (181 vs. 122%) and decreased CLs (60 vs. 38%) in mAT. The findings suggest that hypertrophy is a major contributor to adipose tissue expansion in obesity. Furthermore, exercise training largely demonstrated beneficial effects on adipose tissue remodeling, where AIT is more effective than CT in reducing HFD-induced adipose tissue dysfunction.