(LB03-11-25) Humans With Obesity Display Impaired Amino Acid-Induced Muscle Protein Synthesis Immediately After Aerobic Exercise

Objectives: Our previous research has shown that mixed-muscle protein (MMP) synthesis in response to amino acid infusion remains intact in humans with obesity. In this study our objective was measure MMP fractional synthesis rate (MMP-FSR) before and after amino acid infusion, which was preceded by aerobic exercise, in humans with and without obesity.

Methods: Nine subjects with obesity (BMI = 34.9 ± 2.5 kg/m2 and body fat percent = 41.4 ± 1.5%) and seven subjects without obesity (BMI = 22.7 ± 0.6 kg/m2 and body fat percent = 25.1 ± 1.7%) were infused with d10-leucine tracer for the entire duration of the study (i.e., 540 mins that included baseline, followed by exercise, followed by the amino acid infusion). Subjects performed an acute bout of aerobic exercise on a stationary bike at 65% VO2 max for 45 mins. This was followed immediately by intravenous amino acid infusion (15% Clinisol; 240 mins). The amino acid infusion (4 mg·kg·FFM^-1min^-1) started at 300 mins and continued to the end of the infusion study. Muscle biopsies from the vastus lateralis were taken at baseline, 45 mins after the start of the amino acid infusion/end of the exercise and at the end of the infusion study to determine MMP-FSR.

Results: Subjects without obesity displayed an increase in MMP-FSR from baseline (0.077 ± 0.11 %/hr) to post-exercise plus amino acid infusion (0.098 ± 0.009 %/hr; p = 0.05). However, subjects with obesity did not exhibit an increase in MMP-FSR from baseline (0.088 +/- 0.007 %/hr) to post-exercise plus amino acid infusion (0.083 ± 0.008 %/hr, p = 0.59). Further, the absolute change in MMP-FSR was greater in subjects without obesity (0.021 ± 0.003) when compared to that in subjects with obesity (-0.005 ± 0.011; p = 0.04).

Conclusions: We conclude that following acute aerobic exercise, humans with obesity exhibit impaired muscle protein synthesis in response to amino acid stimulation.

Funding Sources: This research was supported by the National Institutes of Health/ National Institute of Diabetes and Digestive and Kidney Diseases.