Mechanisms underlying the direct effects of exercise on metabolic health (independently of weight loss) are poorly understood, and very little is known about the effects of exercise on adipose tissue. The purpose of this study was to examine the effects of exercise training on the key extracellular matrix (ECM) modifiers, matrix metalloproteinase 2 (MMP2) and MMP9, in abdominal subcutaneous adipose tissue (aSAT) of obese adults. Seven obese adults (BMI=33±4 kg/m2; age=32±6) completed 12 weeks of exercise training (either 45min of steady-state exercise at 70% HRmax or 10x1min intervals at 90% HRmax with 1min recovery between intervals), and they were required to maintain body weight throughout. aSAT biopsies were collected before training (Pre) and twice after training - 1 day post exercise (1d PEX) and again 4 days post exercise (4d PEX; to wash out the acute effects of exercise). Using standard immunoblotting methods, we found no evidence for effects of training on either MMP2 or MMP9. However, using gelatin zymography (a technique with more than 100-fold higher sensitivity than immunoblotting) we found a strong trend for an increased MMP9 abundance 1d PEX (3.7±1.0 vs. 3.0±1.4 arbitrary units (AU), for 1d PEX vs. Pre; P=0.08). Interestingly, however, MMP9 returned to Pre training levels by 4d PEX (1.9±1.3 AU; P<0.05 vs. 1d PEX). Gelatin zymography can also allow for quantification of the active-form of MMPs, and we found trends for exercise training to increase MMP2 in both its active- (P=0.08 and P=0.22 for 1d PEX and 4d PEX vs. Pre, respectively) and inactive-form (P=0.13 and P=0.12 for 1d PEX and 4d PEX vs. Pre, respectively). We were unable to detect the active form of MMP9.
In summary, because increased abundance and activity of MMPs may alter the fibrotic content and composition of the ECM, exercise-induced increases in MMP2 and MMP9 within aSAT may contribute to favorable modifications within adipose tissue ECM of obese adults.
P. Varshney: None. B.J. Ryan: None. C. Ahn: None. M.W. Schleh: None. J.F. Horowitz: None.
National Institutes of Health (R01DK077966, P30DK089503, F32DK117522, UL1TR002240)