The main objective of this project is to study the diurnal variation of the effect of exercise on glycemic metabolism and fat oxidation in humans.
Strong scientific evidence supports the beneficial effects of exercise on cardiovascular health, the regulation of glucose metabolism, and fat oxidation. Physical performance capacity is known to fluctuate throughout the day, however, it is unknown whether there is an optimal time of day to maximize the effects of exercise on health, and specifically on blood glucose metabolism and fat oxidation. Finding the ideal time to perform physical exercise is of clinical and public health interest. Likewise, optimizing the timing of physical exercise to coincide with the greater physiological response of each individual would mean increasing the potential of exercise as a therapeutic tool. Specific aims of this project are a) to describe possible differences dependent on sex in the diurnal variation of the effect of exercise on glycemic metabolism and fat oxidation, and b) to characterize the molecular mechanisms implicated. 18 men and 17 women with normal weight will be randomized into two conditions (morning and evening) with at least 3 days of separation in between. Each evaluation will conform the following tests: 1. Basal metabolic rate assessment through indirect calorimetry during 30 minutes. 2. Fuel oxidation and energy expenditure assesment during a 60 minutes bout of aerobic steady-state exercise (cycling), through indirect calorimetry. 3. Fuel oxidation and energy expenditure assesment after exercise during 30 minutes, through indirect calorimetry. 4. Blood samples assesment before, inmediately after, and 90 minutes after exercise. 5. Quadriceps biopsies before, and inmediately after exercise. \*This will be done only in a sub-cohort. 6. Visual analog scales to assess appetite before, inmediately after, and 90 minutes after exercise. 7. Continous glucose monitoring from the previous 24 hrs to first session day, until 48 hrs after the last exercise session. Previous to this, participants' body composition and fitness level will be assesed via densitometry and a maximal exercise test, respectively.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
PREVENTION
Masking
SINGLE
Enrollment
35
Aerobic exercise
University of Granada - Instituto Mixto Universitario Deporte y Salud
Granada, Spain
Change from resting blood glucose to 48 hours after exercise
A continuous glucose monitor inserted into the skin of the arm upper forearm area will be used to record and store blood glucose levels every 15 minutes, for 24 hours, 14 consecutive days. Within this time range both exercise conditions will be performed. The monitor will be placed 24 hours before the first exercise session and will be removed 48 hours after the second exercise session. Therefore, change from resting blood glucose 24 hours previous to 48 hours after exercise will be obtained for each condition.
Time frame: 4 days. Pre exercise day, exercise day, post-24hrs exercise day, post-48hrs exercise day.
Change from resting fat oxidation to 90 minutes after exercise
Participants will lay down for 60 minutes where resting gas exchange was measured (using a canopy hood for gases collection) for 30 minutes in two separated 15 minutes stages, corresponding to 45 to 60 and 75 to 90 minutes after exercise, respectively
Time frame: 210 minutes
Change from resting markers of glucose metabolism to 90 minutes after exercise
Blood samples will be taken after exercise, immediately after exercise and 90 minutes after exercise, in order to measure change in plasma concentration of markers of glucose metabolism from resting to 90 minutes after exercise.
Time frame: 180 minutes
Change from resting markers of fatty acid metabolism to 90 minutes after exercise
Blood samples will be taken to measure plasma concentration of markers of fatty acid metabolism before, immediately after and 90 minutes after exercise.
Time frame: 180 minutes
Gene expression
Muscular biopsies will be taken from the vastus lateralis' distal part of the quadriceps in a sub-sample before and immediately after the exercise. Biopsies will be performed by an experienced surgeon using microbiopsy needles (Achieve Automatic Needle 16G x 15 cm), obtaining \~30 mg per biopsy after previous local anaesthesia with 2% lidocaine. From each time point (Pre and Post), 1 skeletal muscle samples will be collected and immersed in liquid nitrogen and stored at -80ºC until further analysis (i.e.: transcriptomics). RNA from skeletal muscle will be extracted using Trizol (Invitrogen).
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Time frame: 90 minutes
Protein expression
Muscular biopsies will be taken from the vastus lateralis' distal part of the quadriceps in a sub-sample before and immediately after the exercise. Biopsies will be performed by an experienced surgeon using microbiopsy needles (Achieve Automatic Needle 16G x 15 cm), obtaining \~30 mg per biopsy after previous local anaesthesia with 2% lidocaine. From each time point (Pre and Post), 1 skeletal muscle samples will be collected and immersed in liquid nitrogen and stored at -80ºC until further analysis (i.e.: proteomics).
Time frame: 90 minutes
Mitochondrial breathing
Muscular biopsies will be taken from the vastus lateralis' distal part of the quadriceps in a sub-sample before and immediately after the exercise. Biopsies will be performed by an experienced surgeon using microbiopsy needles (Achieve Automatic Needle 16G x 15 cm), obtaining \~30 mg per biopsy after previous local anaesthesia with 2% lidocaine. From each time point (Pre and Post), 1 skeletal muscle samples will be collected and treated fresh to study mitochondrial respiration.
Time frame: 90 minutes
Mitochondrial supercomplexes
Muscular biopsies will be taken from the vastus lateralis' distal part of the quadriceps in a sub-sample before and immediately after the exercise. Biopsies will be performed by an experienced surgeon using microbiopsy needles (Achieve Automatic Needle 16G x 15 cm), obtaining \~30 mg per biopsy after previous local anaesthesia with 2% lidocaine. From each time point (Pre and Post), 1 skeletal muscle samples will be collected and immersed in liquid nitrogen and stored at -80ºC until further analysis (i.e.: mitochondrial protein supercomplexes by blue-native PAGE).
Time frame: 90 minutes
Change from resting appetite to 90 minutes after exercise
Measures of appetite before, immediately after and 90 minutes after exercise using an appetite visual analog scale (appetite VAS) scoring from 0 to 10, where 0 is the minimum punctuation for appetite and 10 is the maximum punctuation for appetite.
Time frame: 180 minutes