Exercise Decreases Marrow Adipose Tissue Through ß-Oxidation in Obese Running Mice: EXERCISE DECREASES MAT IN OBESE MICE

The relationship between marrow adipose tissue (MAT) and bone health is poorly understood. We used running exercise to ask whether obesity-associated MAT can be attenuated via exercise and whether this correlates with gains in bone quantity and quality. C57BL/6 mice were divided into diet-induced obesity (DIO, n = 14) versus low-fat diet (LFD, n = 14). After 3 months, 16-week-old mice were allocated to an exercise intervention (LFD-E, DIO-E) or a control group (LFD, DIO) for 6 weeks (4 groups, n = 7/group). Marrow adipocyte area was 44% higher with obesity (p<0.0001) and after exercise 33% lower in LFD (p<0.0001) and 39% lower in DIO (p<0.0001). In LFD, exercise did not affect adipocyte number; however, in DIO, the adipocyte number was 56% lower (p<0.0001). MAT was 44% higher in DIO measured by osmium-µCT, whereas exercise associated with reduced MAT (–23% in LFD, –48% in DIO, p<0.05). MAT was additionally quantified by 9.4TMRI, and correlated with osmium-µCT (r = 0.645; p<0.01). Consistent with higher lipid beta oxidation, perilipin 3 (PLIN3) rose with exercise in tibial mRNA (+92% in LFD,+60% in DIO, p<0.05). Tibial µCT-derived trabecular bone volume (BV/TV) was not influenced by DIO but responded to exercise with an increase of 19% (p<0.001). DIO was associated with higher cortical periosteal and endosteal volumes of 15% (p = 0.012) and 35% (p<0.01), respectively, but Ct. Ar/Tt.Ar was lower by 2.4% (p