Skeletal muscle extracellular matrix(ECM) remodeling has been proposed as a feature of obesity. Whether exercise prevents this remodeling has not been reported. This study investigated effects of 10 weeks of two isocaloric exercise programs, as endurance(END) or high intensity interval training(HIIT), in a mouse model of diet-induced obesity, on metabolic profiles and skeletal muscle ECM gene expression: Collagen-IV and -VI, matrix metalloproteinase(MMP)-3, MMP-14, and tissue inhibitor of matrix metalloproteinase(TIMP-2).
Ten week-old male C57BL/6 mice were fed HFD(45% FAT) ab libitum and underwent END or HIIT for 10 weeks(3x40min sessions/week). Chow-fed mice acted as controls.
As expected, maximal running capacity(distance in treadmill progressive test) was higher in END and HIIT groups compared to HFD alone, with END being superior to HIIT(END=2.8±0.5; HIIT=2.2±0.3 (fold-change compared to HFD);p=0.03). Compared to HFD alone, both training programs similarly protected (p<0.05) against body weight(BW) gain (p<0.05) (final weight (g) HFD=45±2;END=37±2;HIIT=36±2), preserved fat-free mass(%FFM) (HFD=58±3;END=72±6;HIIT=72±7), improved blood glucoseAUC during an insulin tolerance test(0.65IU/kg*BW) (HFD=411±54;END=350±57;HIIT=320±66 A.U.), and increased spontaneous physical activity levels measured by displacement in a metabolic cage(HFD=211±59;END=308±76;HIIT=304±77 A.U.), without differences between training programs (p>0.05). An increase in fasting blood glucose level by HFD was prevented only in END, whereas increases in EE were not prevented by exercise(HFD=21.6±1.5;END=21.1±1.7;HIIT=20.6±0.7 kcal/hr/FFM;p>0.05). HFD resulted in ~2-fold increases in quadriceps mRNA levels of MMP-3, MMP-14, TIMP-2 and Collagen-IV(p<0.05), with END and HIIT both preventing increases in TIMP-2 and Collagen-IV. Compared with END, HIIT induced higher mRNA levels of MMP-14 and Collagen-VI(p<0.01). Only END increased mRNA levels of MMP3(4-fold compared to CHOW;p<0.01).
In HFD mice HIIT did not impact fasting glucose or skeletal muscle mRNA levels in a similar fashion compared with END. Defining correlative muscle functional implications of these observed differences requires further study.