The development of a low-grade, chronic, systemic inflammation observed in the elderly (inflammaing) has been associated with increased risk for skeletal muscle wasting, strength loss and functional impairments. According to studies performed in animals and cell cultures increased concentrations of pro-inflammatory cytokines such as IL-6 and TNF-α as well as increased levels of hs-CRP lead to elevated protein degradation through proteasome activation and reduced muscle protein synthesis (MPS) via downregulation of the Akt-mTOR signaling pathway. However, evidence regarding the effects of inflammaging on skeletal muscle mass in humans is lacking. Thus, the present study will compare proteasome activation and the protein synthetic response in the fasted and postprandial period between older adults with increased systemic inflammation and their healthy control counterparts.
A total number of \> 60 male, older adults aged 63-73 years will be initially screened for systemic levels of hs-CRP and IL-6. Of these, 24 individuals that will comply with the study criteria will be allocated to either a High (IL6: ≥ 1.7 pg/ml; hs-CRP: \> 1.0 mg/L) (n=12) or a Low (IL6: \< 1.7 pg/ml; hs-CRP: \< 1.0 mg/L) (n=12) systemic inflammation group. Approximately 2 weeks before the experimental trial, anthropometry, resting metabolic rate (RMR), body composition (with DXA), sarcopenia status, functional capacity and the knee-extension one repetition maximum (1RM) will be assessed in individuals from both groups. In addition, levels of habitual physical activity will be assessed using accelerometry (over a 7-day period) and daily dietary intake will be monitored through 7-day diet recalls in all participants. 1 week before the experimental day an oral glucose tolerance test (OGTT) will be also performed over a 2-hour period, with blood sampling every 15min during the first hour and every 30min during the second hour. The day before the experimental trial, participants will consume 150ml of D2O 70% atom as a bolus. In the experimental day, participants will arrive at the laboratory after an overnight fast and a baseline blood sample and a muscle biopsy from vastus lateralis muscle will be collected. Immediately after, participants will perform 8 sets with 10 repetitions at 80% of 1RM and 2 min rest between each set, on a knee-extension machine. After exercise, they will ingest 0.4 g whey protein isolate/kg body weight as single bolus and then they will remain in a sitting position over a 3-hour period. Blood samples will be collected every 30min during the 3-hour postprandial period while a second muscle biopsy will be obtained at 3h.
Study Type
INTERVENTIONAL
Allocation
NON_RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
DOUBLE
Enrollment
44
0,4 g of whey protein isolate/kg body weight will be ingested as a bolus of 250 ml immediately after the resistance exercise bout.
Exercise Biochemistry Laboratory, School of Physical Education & Sports Sciences, University of Thessaly
Trikala, Greece
Systemic inflammation
Levels of systemic inflammation will be assessed by measuring serum levels of hs-CRP, IL-6 and TNF-α.
Time frame: At baseline.
Change in muscle protein synthesis (MPS)
Using deuterium oxide (D2O) 70% atom administration. Individuals will consume a single bolus of 150ml D20 the day before the clinical trial and muscle biopsy samples, collected before and after the exercise bout and protein ingestion, will be analyzed for isotopic measurement using GC-P-IRMS.
Time frame: At baseline and 180 min following protein ingestion.
Change in intracellular signaling proteins in muscle
Phosphorylation levels of Akt, mammalian target of rapamycin (mTOR), p70S6K and ribosomal protein S6 (rpS6) will be measure using western blotting.
Time frame: At baseline and 180 min following protein ingestion.
Change in proteasome activities in muscle
Chymotrypsin-like (CT-L), caspase-like (C-L) and trypsin-like (T-L) proteasome activities will be assayed with hydrolysis of the fluorogenic peptide LLVY-AMC, LLE-AMC and LSTR-AMC, respectively.
Time frame: At baseline and 180 min following protein ingestion.
Change in protein expression level of proteasome subunits
Immunoblot analysis will be used to detect protein expression levels of proteasome (β5, β2 and β1) and immunoproteasome (β5i, β2i and β1i) subunits.
Time frame: At baseline and 180 min following protein ingestion.
Resting metabolic rate (RMR)
RMR will be assessed after an overnight fast with participants in a supine position following a 15-min stabilization period by taking 30 consecutive 1-min VO2/CO2 measurements using a portable open-circuit indirect calorimeter with a ventilated hood system following a standard calibration protocol.
Time frame: At baseline.
Physical activity
Level of habitual physical activity will be assessed using accelerometry (ActiGraph GT3X-BT accelerometer).
Time frame: Over a 7-day period at baseline.
Dietary intake
Daily dietary intake will be assessed using 7-day diet recalls.
Time frame: Over a 7-day period at baseline.
Reduced glutathione in blood
Concentration of reduced glutathione will be measured in red blood cells
Time frame: At baseline.
Oxidized glutathione in blood
Concentration of oxidized glutathione will be measured in red blood cells
Time frame: At baseline.
Protein carbonyls in serum
Concentration of protein carbonyls will be measured in serum.
Time frame: At baseline.
Total antioxidant capacity
Total antioxidant capacity will be measured in serum
Time frame: At baseline.
Malondialdehyde in serum
Concentration of malondialdehyde will be measured in serum.
Time frame: At baseline.
White blood cell count in blood
White blood cell count will be measured in blood.
Time frame: At baseline.
Insulin sensitivity
Insulin sensitivity will be assessed through an oral glucose tolerance test (OGTT) which involve ingesting glucose solution (75 g) with 5ml arterialized venous blood samples drawn at baseline and every 15 min during the first hour and every 30 min during the second hour over a 2-hour period.
Time frame: At baseline.
Glucose concentration in blood
Glucose concentration will be measured in plasma during the clinical trial.
Time frame: At baseline and at 30 min, 60 min, 90 min, 120 min, 150 min and 180 min following protein ingestion.
Insulin concentration in blood
Insulin concentration will be measured in plasma during the clinical trial.
Time frame: At baseline and at 30 min, 60 min, 90 min, 120 min, 150 min and 180 min following protein ingestion.
Body composition
Body composition will be measured using a dual-energy x-ray absorptiometry scanner (DEXA).
Time frame: At baseline
Body Mass Index (BMI)
Calculated as body mass (kg) divided by the height (m) squared.
Time frame: At baseline
Skeletal muscle index
Calculated as an appendicular lean mass (kg) divided by height (m) squared.
Time frame: At baseline
Grip strength
Using handgrip dynamometry (left and right arm) in a sitting position.
Time frame: At baseline
Functional performance
Functional performance will be assessed using the Short Physical Performance Battery (SPPB).
Time frame: At baseline
Lower limb muscle strength
Will be assessed by defining the 1 repetition maximum (1RM) on a knee-extension machine.
Time frame: At baseline
This platform is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional.