Adipose Tissue Lipid Accumulation Pathways in Marathon Runners

Eighteen male marathon runners (mean marathon performance: 2 h 36 min, SD = 7.0 min; V̇O2max = 64.1 ± 15.1 ml/kg·min-1) were submitted to a needle biopsy in the suprailiac region and to various measurements of body fatness: percent body fat (% fat), seven skinfold thicknesses, and mean fat cell diameter. Basal and insulin-stimulated glucose conversion into triglycerides were measured in collagenase-isolated fat cells, while heparin-releasable lipoprotein lipase activity (LPLa) was determined in intact adipose tissue. All body fatness indicators were significantly smaller in marathon runners in comparison to a sedentary control group (P < 0.001). Fat cell basal and insulin-stimulated glucose conversion into triglycerides as well as LP La were significantly higher for the runners group (P < 0.01), differences being particularly important when comparisons were performed between subjects paired for mean fat cell diameter. Pearson interclass correlations between body fatness and fat cell glucose incorporation into triglycerides were low and positive for the sedentary group (0.04 ≦ r ≦ 0.41), while they were negative for the marathon runners groups (-0.28 ≦ r ≦ -0.40) with the exception of% fat. Moreover, correlations between LPLa and indicators of body fatness were positive in the sedentary group (0.47 ≦ r ≦ 0.79), while they were negative in the marathon runners group (-0.03 ≦ r ≦ -0.63). These results indicate that long-distance runners are characterized by increased adipose tissue lipid accumulation activities, possibly as a result of their endurance training regimen.