Insights into the Serum Metabolic Adaptations in Response to Inspiratory Muscle Training: A Metabolomic Approach Based on 1H NMR and UHPLC-HRMS/MS

Inspiratory muscle training (IMT) is known to promote physiological benefits and improve physical performance in endurance sports activities. However, the metabolic adaptations promoted by different IMT prescribing strategies remain unclear. In this work, a longitudinal, randomized, double-blind, sham-controlled, parallel trial was performed to investigate the effects of 11 weeks (3 days·week-1) of IMT at different exercise intensities on the serum metabolomics profile and its main regulated metabolic pathways. Twenty-eight healthy male recreational cyclists (30.4 ± 6.5 years) were randomized into three groups: sham (6 cm·H2O of inspiratory pressure, n = 7), moderate-intensity (MI group, 60% maximal inspiratory pressure (MIP), n = 11) and high-intensity (HI group, 85-90% MIP, n = 10). Blood serum samples were collected before and after 11 weeks of IMT and analyzed by 1H NMR and UHPLC-HRMS/MS. Data were analyzed using linear mixed models and metabolite set enrichment analysis. The 1H NMR and UHPLC-HRMS/MS techniques resulted in 46 and 200 compounds, respectively. These results showed that ketone body metabolism, fatty acid biosynthesis, and aminoacyl-tRNA biosynthesis were upregulated after IMT, while alpha linolenic acid and linoleic acid metabolism as well as biosynthesis of unsaturated fatty acids were downregulated. The MI group presented higher MIP, Tryptophan, and Valine levels but decreased 2-Hydroxybutyrate levels when compared to the other two studied groups. These results suggest an increase in the oxidative metabolic processes after IMT at different intensities with additional evidence for the upregulation of essential amino acid metabolism in the MI group accompanied by greater improvement in respiratory muscle strength.

Cardiorespiratory coupling as an early marker of cardiac autonomic dysfunction in type 2 diabetes mellitus patients

The aim of this study was to assess cardiorespiratory coupling (CRC) in type 2 diabetes mellitus patients (T2DM) and apparently healthy individuals, in order to test the hypothesis that this method can provide additional knowledge to the information obtained through the heart rate variability (HRV). A cross-sectional study was conducted in T2DM patients(T2DMG=32) and health controls (CON=32). For CRC analysis, the electrocardiogram, arterial pressure, and thoracic respiratory movement were recorded at rest in supine position and during active standing. Beat-to-beat series of heart period and systolic arterial pressure were analyzed with the respiratory movement signal via a traditional non-causal approach, such as squared coherence function. In this sample of T2DM, no differences in HRV were observed when compared to the CON, but the T2DMG showed a reduction in resting CRC. We conclude that in CRC in T2DM, reflected by the squared coherence may already be compromised even before HRV changes.