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Objective: Acetylcarnitine plays an important role in fat metabolism and can be detected in proton magnetic resonance spectra in skeletal muscle. An inverse relationship of acetylcarnitine to intramyocellular lipids and metabolic markers of chronic hyperglycemia has been suggested. This study aimed to compare the acetylcarnitine concentrations and intramyocellular lipids measured noninvasively by proton magnetic resonance spectroscopy ( 1 H MRS) in the tibialis anterior and the soleus of three different groups of volunteers with a broad range of glycemic control., Methods: Acetylcarnitine and intramyocellular lipid concentrations were measured in 35 individuals stratified into three groups according to glucose tolerance and/or manifestation of type 2 diabetes mellitus. All MRS measurements were performed on a 3-T MR system., Results: The differences in patient phenotype were mirrored by increased intramyocellular lipids in the tibialis anterior and decreased acetylcarnitine concentrations in the soleus muscle of type 2 diabetes patients when compared with normal glucose-tolerant individuals. Results suggest that intramyocellular lipids mirror whole-body glucose tolerance better in the tibialis anterior muscle, whereas acetylcarnitine is a better discriminator in the soleus muscle., Conclusions: This muscle-specific behavior of metabolites could represent different fiber compositions in the examined muscles and should be considered when planning future metabolic studies., (© 2020 The Authors. Obesity published by Wiley Periodicals LLC on behalf of The Obesity Society (TOS).)

Brain-derived neurotrophic factor (BDNF) participates in orchestrating the adaptive response to exercise. However, the importance of transient changes in circulating BDNF for eliciting whole-body and skeletal muscle exercise benefits in humans remains relatively unexplored. Here, we investigated effects of acute aerobic exercise and 3-month aerobic-strength training on serum, plasma and skeletal muscle BDNF in twenty-two sedentary older individuals (69.0 ± 8.0 yrs., 9 M/13F). BDNF response to acute exercise was additionally evaluated in young trained individuals (25.1 ± 2.1 yrs., 3 M/5F). Acute aerobic exercise transiently increased serum BDNF in sedentary (16%, p = .007) but not in trained elderly or young individuals. Resting serum or plasma BDNF was not regulated by exercise training in the elderly. However, subtle training-related changes of serum BDNF positively correlated with improvements in walking speed (R = 0.59, p = .005), muscle mass (R = 0.43, p = .04) and cognitive performance (R = 0.41, p = .05) and negatively with changes in body fat (R = -0.43, p = .04) and triglyceridemia (R = -0.53, p = .01). Individuals who increased muscle BDNF protein in response to 3-month training (responders) displayed stronger acute exercise-induced increase in serum BDNF than non-responders (p = .006). In addition, muscle BDNF protein content positively correlated with type II-to-type I muscle fiber ratio (R = 0.587, p = .008) and with the rate of post-exercise muscle ATP re-synthesis (R = 0.703, p = .005). Contrary to serum, acute aerobic exercise resulted in a decline of plasma BDNF 1 h post-exercise in both elderly-trained (-34%, p = .002) and young-trained individuals (-48%, p = .034). Acute circulating BDNF regulation by exercise was dependent on the level of physical fitness and correlated with training-induced improvements in metabolic and cognitive functions. Our observations provide an indirect evidence that distinct exercise-induced changes in serum and plasma BDNF as well as training-related increase in muscle BDNF protein, paralleled by improvements in muscle and whole-body clinical phenotypes, are involved in the coordinated adaptive response to exercise in humans., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Objectives: The aims of this study were to detect the acetylcarnitine resonance line at 2.13 ppm in the human vastus lateralis and soleus muscles, assess T1 and T2 relaxation times, and investigate the diurnal and exercise-related changes in absolute concentration noninvasively, using proton magnetic resonance spectroscopy at 7 T., Materials and Methods: All measurements were performed on a 7 T whole-body Magnetom MR system with a 28-channel knee coil. Five healthy, moderately trained volunteers participated in the assessment of the detectability, repeatability, and relaxation times of acetylcarnitine. For the evaluation of the effect of training status, another 5 healthy, normally active volunteers were examined. In addition, normally active volunteers underwent a day-long protocol to estimate diurnal changes and response to the exercise., Results: Using a long echo time of 350 milliseconds, we were able to detect the acetylcarnitine resonance line at 2.13 ppm in both muscle groups without significant lipid contamination. The T1 of acetylcarnitine in the vastus lateralis muscle was found to be 1807.2 ± 513.1 milliseconds and T2 was found to be 129.9 ± 44.9 milliseconds. Concentrations of acetylcarnitine from the vastus lateralis muscle in moderately trained volunteers were higher than concentrations from normally active volunteers. Acetylcarnitine concentrations changed during the day, tending to be higher in the morning after an overnight fast than after lunch. After 10 minutes of high-intensity exercise, the concentration significantly increased, and 15 minutes after cessation of exercise, a decrease could be observed., Conclusions: Our results demonstrate an effective detection of acetylcarnitine using a long TE of 350 milliseconds at 7 T in the vastus lateralis and soleus muscles with high repeatability and reliability on a 7 T scanner. Our data emphasize the need for strict standardization, physical activity, and dietary conditions for the measurement of the acetylcarnitine.