BAIBA Does Not Regulate UCP-3 Expression in Human Skeletal Muscle as a Response to Aerobic Exercise

Objective: -Aminoisobutyric acid (BAIBA) has shown to modulate uncoupling protein (UCP)-1 expression, which is mainly expressed in white adipose tissue; however, no studies to date have analyzed its potential effect on the main uncoupling protein of skeletal muscle, UCP-3. The main goal of this study was to assess the potential effect of acute aerobic exercise on serum BAIBA and skeletal muscle UCP-3. The secondary goal was to assess the potential involvement of the transcription factors proliferator-activated receptor gamma coactivator 1-alpha (PGC-1) and peroxisome proliferator-activated receptor alpha (PPAR), as well as free fatty acids (FFAs) in UCP-3 expression. A tertiary goal of the study was to evaluate the potential effect of consuming a preexercise meal on the outcome of the first 2 objectives.Methods: In a randomized crossover design, untrained participants performed 2 acute cycling sessions (350kcal at 70% of their VO2peak) after 2 experimental conditions: (1) consumption of a multi-macronutrient shake and (2) a fasting period of 8hours. Blood samples were taken at baseline, preexercise, postexercise, 1hour, and 4hours postexercise, and muscle biopsies were taken at the last 4 time points. UCP-3 protein concentration and expression, as well as the mRNA expression of PGC-1 and PPAR, were measured in muscle, and BAIBA, glucose, and FFA were measured in serum.Results: Aerobic exercise failed to induce a significant effect on serum BAIBA, PGC-1, and PPAR regardless on the feeding condition. Despite the lack of effect of exercise on the previous variables, UCP-3 expression and protein concentration significantly increased in the shake condition.Conclusion: The expression of human skeletal muscle UCP-3 as a result of exercise might be controlled by factors other than BAIBA.