A-15 Free Communication/Slide - Immunology: MAY 27, 2009 9:30 AM - 11:00 AM ROOM: 4C4
The expansion of white adipose tissue (WAT) requires a parallel increase in angiogenesis. In obesity, WAT expansion precedes angiogenesis resulting in hypoxia, WAT inflammation, insulin resistance (IR), and hepatic steatosis (HS). Exercise training (EX) may increase WAT angiogenesis thereby improving IR and HS.
PURPOSE: To determine if EX increases angiogenesis in WAT and if this is related to improvements in WAT inflammation, IR, and/or HS associated with obesity.
METHODS: Mice (n=54) fed a 45% fat diet (HFD) for 6 wks were randomly assigned to an EX (treadmill running, 5d/wk X 12 wks; 40 min/d; 12m/min; 12% grade; 65-70%VO2) or sedentary (SED) group. Mice remained on HFD or were placed on a 10% fat diet (LFD) for a 12 wk intervention. Following the intervention, WAT and liver tissue samples were weighed, frozen in liquid N2 and stored at -80°C. Relative epididymal fat pad weight was used to assess adiposity. HS was assessed by total TG content, and IR by HOMA-IR. Rt-PCR was used to determine WAT gene expression (VEGF, angiogenesis; TNF-a and F480, inflammation). Comparisons were made using two-way (EX, LFD, EXxLFD) ANOVA; data are mean±SEM.
RESULTS: EX and LFD decreased adiposity by 33% (F(1,53)=27.4; p<0.001) and 43% (F(1,52)=60.7; p<0.001), respectively. Compared to SED, EX decreased HS (22.1±4.8 vs. 54.7±4.8 mgTG/g liver, F(1,53)=22.9; p<0.001), and tended to decrease IR by 27% (F(1,52)=3.4; p=0.07). Compared to HFD, LFD decreased IR by 48% (F(1,52)=13.2; p=0.001), but not HS (p=0.17). Compared to SED, EX increased VEGF gene expression by 213 % (F(1,41)=9.8; p=0.003). EX and LFD decreased TNF-a gene expression by 50 and 71%, respectively (EXxLFD interaction: F(1,52)=6.1; p=0.017). EX and LFD decreased F480 gene expression by 71 and 100%, respectively (EXxLFD interaction: F(1,43)=5.1; p=0.029). Regression analyses revealed EX (p=0.006), adiposity (p<0.001), F480 (p<0.001) and VEGF (p=0.017) to be independent predictors of IR (R2=.63, F(7,39)=7.8; p<0.001) while LFD (p=0.01) and adiposity (p=0.006) were independent predictors of HS (R2=.63, F(7,39)=7.8; p<0.001).
CONCLUSION: EX independently increases WAT VEGF gene expression. EX-related increases in WAT angiogenesis may contribute to improvements in adipose tissue physiology and systemic IR.