Resistance Exercise and Muscle Protein Synthesis in Obese Adults
| Status: | Completed |
|---|---|
| Conditions: | Obesity Weight Loss |
| Therapuetic Areas: | Endocrinology |
| Healthy: | No |
| Age Range: | 20 - 45 |
| Updated: | 5/3/2018 |
| Start Date: | January 1, 2017 |
| End Date: | May 1, 2018 |
Resistance Exercise as a Strategy to Enhance Postprandial Muscle Protein Synthesis in Obese Adults
Obesity has numerous comorbidities that are associated with exceedingly high healthcare
costs. In addition to well- characterized impairments in lipid and glucose metabolism,
obesity is associated with altered protein metabolism. We have recently observed that obese
individuals are essentially nonresponsive to protein ingestion with respect to myofibrillar
protein synthesis. This suggests that skeletal muscle remodeling in obese individuals is
impaired possibly contributing to a poor metabolic quality of muscle. Resistance exercise is
known to strongly augment muscle protein synthesis in response to protein ingestion. The
purpose of this research is to determine the muscle protein synthetic response during
post-exercise recovery in obese individuals. Using stable isotope methodology, we will
determine the postprandial muscle protein synthetic response in 14 male and female obese
adults (Age: 20-45, BMI: 30-39.9 kg/m2) immediately after an acute bout of resistance
exercise. Participants will be sedentary (< 60 min exercise/ week) and weight stable for a
minimum of 6 months. During the testing blood and muscle samples will be collected. In
addition participants will be asked to perform moderate intensity resistance exercise.
Completion of the proposed research will identify the role of resistance exercise in the
maintenance of skeletal muscle tissue after the consumption of a protein-dense meal in obese
people.
costs. In addition to well- characterized impairments in lipid and glucose metabolism,
obesity is associated with altered protein metabolism. We have recently observed that obese
individuals are essentially nonresponsive to protein ingestion with respect to myofibrillar
protein synthesis. This suggests that skeletal muscle remodeling in obese individuals is
impaired possibly contributing to a poor metabolic quality of muscle. Resistance exercise is
known to strongly augment muscle protein synthesis in response to protein ingestion. The
purpose of this research is to determine the muscle protein synthetic response during
post-exercise recovery in obese individuals. Using stable isotope methodology, we will
determine the postprandial muscle protein synthetic response in 14 male and female obese
adults (Age: 20-45, BMI: 30-39.9 kg/m2) immediately after an acute bout of resistance
exercise. Participants will be sedentary (< 60 min exercise/ week) and weight stable for a
minimum of 6 months. During the testing blood and muscle samples will be collected. In
addition participants will be asked to perform moderate intensity resistance exercise.
Completion of the proposed research will identify the role of resistance exercise in the
maintenance of skeletal muscle tissue after the consumption of a protein-dense meal in obese
people.
Baseline procedures:
A parallel group design will be used for this study. Prior to the infusion trial,
participants will reported to the laboratory on two separate occasions in the morning. On the
first visit, we will determine participants' body weight and height as well as body
composition by dual-energy X-ray absorptiometry. Finally, participants will be familiarized
with unilateral leg extension and the ten repetition maximum (10RM) procedure. On a separate
occasion, each subject will arrive to the lab after an overnight fast for the determination
of oral glucose tolerance in response to the consumption of 75 g glucose dissolved in 500 mL
of water. At the end of this visit, we will assess participant's unilateral 10RM for leg
extension. In addition, participants will be instructed to refrain from vigorous physical
activity and alcohol for three days prior to the tracer infusion.
Infusion protocol On the day of the infusion trial, participants will report to the
laboratory at ~0700 h after a 10 h fast. An intravenous catheter will be inserted into an
antecubital vein for baseline blood sample collection, after which a primed (2 μmol·kg-1),
continuous infusion (0.05 μmol·kg Lean Body Mass-1·min-1) of L-[ring-13C6]phenylalanine will
be initiated (t=-180 min) and maintained until the end of the trial. A second intravenous
catheter placed in a contralateral dorsal hand vein will be placed in a heated blanket for
repeated arterialized blood sampling. In the post-absorptive state, muscle biopsies of the
vastus lateralis are to be collected at 0 min of infusion from a non-exercised control leg
(CON). Subsequently, participants will perform moderate intensity unilateral leg extension
exercise. Upon completion, participants will consume 170 g of lean ground pork (36 g
protein). Additional muscle biopsies will be collected from both the exercised (EX) and CON
legs at 120 and 300 min after pork ingestion. Arterialized blood samples will be collected
every 30 or 60 min during the post-absorptive and postprandial-states and placed in
pre-chilled EDTA tubes.
A parallel group design will be used for this study. Prior to the infusion trial,
participants will reported to the laboratory on two separate occasions in the morning. On the
first visit, we will determine participants' body weight and height as well as body
composition by dual-energy X-ray absorptiometry. Finally, participants will be familiarized
with unilateral leg extension and the ten repetition maximum (10RM) procedure. On a separate
occasion, each subject will arrive to the lab after an overnight fast for the determination
of oral glucose tolerance in response to the consumption of 75 g glucose dissolved in 500 mL
of water. At the end of this visit, we will assess participant's unilateral 10RM for leg
extension. In addition, participants will be instructed to refrain from vigorous physical
activity and alcohol for three days prior to the tracer infusion.
Infusion protocol On the day of the infusion trial, participants will report to the
laboratory at ~0700 h after a 10 h fast. An intravenous catheter will be inserted into an
antecubital vein for baseline blood sample collection, after which a primed (2 μmol·kg-1),
continuous infusion (0.05 μmol·kg Lean Body Mass-1·min-1) of L-[ring-13C6]phenylalanine will
be initiated (t=-180 min) and maintained until the end of the trial. A second intravenous
catheter placed in a contralateral dorsal hand vein will be placed in a heated blanket for
repeated arterialized blood sampling. In the post-absorptive state, muscle biopsies of the
vastus lateralis are to be collected at 0 min of infusion from a non-exercised control leg
(CON). Subsequently, participants will perform moderate intensity unilateral leg extension
exercise. Upon completion, participants will consume 170 g of lean ground pork (36 g
protein). Additional muscle biopsies will be collected from both the exercised (EX) and CON
legs at 120 and 300 min after pork ingestion. Arterialized blood samples will be collected
every 30 or 60 min during the post-absorptive and postprandial-states and placed in
pre-chilled EDTA tubes.
1. Inclusion criteria
- Healthy-weight adults: BMI 18-24.9 kg/m2
- Obese adults: BMI 30-39.9 kg/m2
- Aged between 20-45 years
- Healthy
- Sedentary
2. Exclusion criteria
- Smoking
- Allergies to pork consumption
- Unusually high protein consumption
- Vegetarians
- Phenylketonuria (PKU)
- Diagnosed GI tract diseases
- Arthritic conditions
- A history of neuromuscular problems
- Previous participation in amino acid tracer studies
- Predisposition to hypertrophic scarring or keloid formation
- Individuals on any medications known to affect protein metabolism (i.e.
corticosteroids, non-steroidal anti-inflammatories, or prescription strength acne
medications).
- Irregular menstrual cycles during the previous year
- Pregnancy
- High BMI that is not representative of being obese (e.g. resistance trained
individuals, football players)
- Contraindications for exercise
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