Mitochondrial Metabolism and Oxidative Stress in Function of the Type of Physical Exercise and Nutritional Counseling in Type 2 Diabetes Mellitus

Assessed changes in haemoglobin saturation delta

时间窗: Pre and post the 12-week intervention

A NIRO-200NX device was used to measure skeletal muscle changes on oxygenated, desoxygenated, and total haemoglobin (μmol/L) through near-infrared spectroscopy (NIRS) and the modified Beer-Lambert law. The NIRS sensor (emitter-sensor distance of 3cm) was placed at 2/3 of the distance between the major trochanter and the lateral epicondyle of the dominant leg. For parameters determined by MBLL, the reference point was set after five minutes of resting in a supine position. The NIRS data were continuously acquired throughout a resting energy expenditure test for 30 minutes, a maximal fat oxidation (MFO) test on a cycloergometer, and a maximal oxygen consumption (VO2max) test on a cycloergometer. Briefly, the MFO test consisted of an incremental task with 3-minute phases starting from 15W and increasing by 15W each phase until a respiratory exchange ratio of 1. After a 5-minute rest, the VO2max test was initiated at last MFO load with 15W increases each minute until VO2max determination.

Assessed changes in Tissue Oxygenation Index

时间窗: Pre and post the 12-week intervention

A NIRO-200NX device was used to measure skeletal muscle tissue oxygenation index (%)through near-infrared spectroscopy (NIRS), the modified Beer-Lambert law (MBLL), and spatially resolved spectroscopy. The NIRS sensor (emitter-sensor distance of 3cm) was placed at 2/3 of the distance between the major trochanter and the lateral epicondyle of the dominant leg. For parameters determined by MBLL, the reference point was set after five minutes of resting in a supine position. The NIRS data were continuously acquired throughout a resting energy expenditure test for 30 minutes, a maximal fat oxidation (MFO) test on a cycloergometer, and a maximal oxygen consumption (VO2max) test on a cycloergometer. Briefly, the MFO test consisted of an incremental task with 3-minute phases starting from 15W and increasing by 15W each phase until a respiratory exchange ratio of 1. After a 5-minute rest, the VO2max test was initiated at last MFO load with 15W increases each minute until VO2max determination.

Muscle biopsy samples: mitochondrial respiratory capacity

时间窗: Pre and post the 12-week intervention

Skin was locally anesthetized, followed by an incision of approximately 6-7mm on the dermal surface. Using sterilized Bergstrom needles, approximately 3-6 mg of skeletal muscle from the lateral vastus were extracted and placed in a BIOPS buffer for immediate analysis of mitochondrial respiration (MR) through high-resolution respirometry. Before, the fibers were mechanically separated in BIOPS buffer using sterilized needles and chemically permeabilized with a 50 μg/ml saponin solution. MR was measured in a specific buffer (Mir05) in duplicate in hyperoxygenated chambers (250-450 nmol/mL of oxygen) in an Oxygraph-2k at 37ºC (Oroboros, Innsbruck, Austria). A substrate-uncoupler titration protocol was employed by adding (final concentration): malate (2mM), pyruvate (5mM), glutamate (2mM), MgCl2 (3mM), and ADP (5mM), cytochrome C (10μM), succinate (10mM), and p-trifluoromethoxyphenylhydrazone. Oxygen flux was presented as mass-specific (pmol·s/mg wet weight) and normalized to CS activity.

Assessed changes in Oxidative Stress

时间窗: Pre and post the 12-week intervention

The level of oxidative stress was assessed by the concentration of 8-OHdG as a biomarker of DNA oxidation. A competitive ELISA detection method was employed in serum samples. Briefly, the standard and the sample were added to a pre-coated microplate along with the biotinylated detection antibody. After washing, HRP-Streptavidin was added. Then, the TMB substrate was added, and the reaction was terminated with an acid solution. The color production was measured spectrophotometrically at a wavelength of 450nm. The optical density values of samples were compared with those of the standard curve to determine the 8-OHdG concentration (ng/ml).

Muscle biopsy sample: Citrate Synthase activity

时间窗: Pre and post the 12-week intervention

2-5 mg of frozen muscle was homogenized in a 1:20 dilution of CelLytic™ MT Tissue Lysis (C3228, Sigma-Aldrich, Dorset, UK), with 1 % protease inhibitor cocktail (P8340, Sigma-Aldrich, Dorset, UK) at 4 °C. The lysate was centrifuged at 12,000 × g for 10 min at 4 °C to pellet debris, and the supernatant was stored at -80 °C. CS activity was quantified in duplicates using an assay kit following the manufacturer's instructions (CS0720: Sigma-Aldrich, Dorset, UK). Briefly, endogenous activity was recorded through color emission by DTNB, and total activity was calculated after the addition of oxalacetate. Protein concentration was determined in duplicates using a bicinchoninic acid assay kit (BCA1: Sigma-Aldrich, Dorset, UK), enabling normalization of CS activity values to total protein content (µmol/g/min). CS activity and protein concentration were measured in 96-well plates using a microplate reader at 412 nm and 562 nm, respectively (MQX200R2, Biotek instruments, Burlington, USA).