Greater myofibrillar protein synthesis following weight-bearing activity in obese old compared with non-obese old and young individuals

Figures

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  Fig. 1. Study schematic and overview of experiential procedures during the muscle protein synthesis assessment period. D2O, deuterium oxide (deuterated water); MRI, magnetic resonance imaging; CHO, carbohydrate; Pro, protein. Drawn using BioRender©

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  Fig. 2. Step count during the 7-day MPS assessment period for young non-obese (Y-NO; dark grey circles), old non-obese (O-NO; light grey circles), and old obese (O-OB; clear circles) adults. The 48-h habitual (i.e., pre-walk) and 48-h exercise (i.e. post-walk) phases are shaded in grey. Average daily step count was significantly higher in Y-NO compared with O-NO and O-OB. Step count on day 5 was significantly elevated, above habitual levels, in O-NO and O-OB but not Y-NO. Significance was set at P < 0.05. * Significantly different from O-NO; # significantly different from O-OB. Values are presented as means ± SD

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  Fig. 3. Quadriceps muscle volume (A) and peak quadriceps muscle cross sectional area (CSA, B) for young non-obese (Y-NO, dark grey bars), old non-obese (O-NO, light grey bars), and old obese (O-OB, white bars), respectively. Quadriceps muscle intramuscular thigh fat fraction (ITFF) for Y-NO, O-NO, and O-OB can be seen in C, respectively, for vastus lateralis (VL, dark grey boxes), vastus medialis (light grey boxes), and rectus femoris (white boxes). Values are presented as the median (central horizontal line), 25th and 75th percentiles (box), minimum and maximum values (vertical lines), and mean (cross). Representative CSA images at 50% of thigh length can be seen in D for Y-NO, O-NO, and O-OB, respectively. The young non-obese individual exhibits a larger quantity of skeletal muscle mass, whereas high infiltration by adipose tissue is observed in the older obese individual. Significance was set at P < 0.05. For A and B, * Significantly different from O-NO, # significantly different from O-OB. For C, * VL significantly different from Y-NO, # VM significantly different from Y-NO, $ RF significantly different from Y-NO

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  Fig. 4. Normalised quadriceps maximal voluntary contraction force (MVC, A), quadriceps MVC relative to body mass (BW, B), quadriceps MVC relative to quadriceps peak cross-sectional area (CSA, C), and quadriceps MVC relative to quadriceps muscle mass (D) for young non-obese (Y-NO, dark grey boxes), old non-obese (O-NO, light grey boxes), and old obese (O-OB, white boxes). Values are presented as the median (central horizontal line), 25th and 75th percentiles (box), minimum and maximum values (vertical lines), and mean (cross). Significance was set at P < 0.05. * Significantly different from O-NO; # significantly different from O-OB

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  Fig. 5. Integrated myofibrillar protein synthesis (iMyoPS) fractional synthetic rates (FSR) over 48 h in the habitual state (black bars) and following a 45-min treadmill walk at ~ 55% V̇O2peak (white bars) in young non-obese (Y-NO), old non-obese (O-ON), and old obese (O-OB), respectively (A). Values are presented as means ± SEM. Individual responses are shown by grey circles and grey squares for pre- and post-walk values, respectively. Delta change in integrated myofibrillar protein fractional synthesis rates (FSR) from habitual to 48 h- post-exercise is presented in B. Average electromyography (EMG) amplitude, a marker of thigh muscle activity, during the 45-min treadmill walk is presented in C and expressed as a percentage of peak EMG amplitude from the progressive walk-to-run test at visit 2. Values are presented as the median (central horizontal line), 25th and 75th percentiles (box), minimum and maximum values (vertical lines), and mean (cross). The dashed horizontal line in B represents zero change. Body water deuterium (2H) enrichment (atom percent excess; APE) for young non-obese (Y-NO; dark grey circles), old non-obese (O-NO; light grey circles), and old obese (O-OB; clear…