CH. 11-12 PROTEINS
Why does pre-sleep exercise + protein ingestion lead to greater muscle protein synthesis?
1. Increased blood flow: Exercise increases blood flow to the muscles, which can enhance the delivery of nutrients, including amino acids, to the muscle cells. This can help to promote protein synthesis. 2. Increased sensitivity to protein: Exercise can also increase the sensitivity of muscle cells to the effects of protein ingestion, allowing them to more effectively utilize the amino acids from the protein to build new muscle tissue. 3. Extended period of protein availability: Protein ingestion before sleep provides a sustained availability of amino acids throughout the night, which can help to counteract the natural decline in muscle protein synthesis that occurs during sleep. 4. Leucine trigger: Protein sources that are high in leucine, such as whey protein, can activate the mTOR signaling pathway, which is a key regulator of muscle protein synthesis. Consuming protein before sleep provides a sustained elevation of leucine levels in the blood, which can enhance muscle protein synthesis. Overall, combining pre-sleep exercise with protein ingestion can create a synergistic effect that enhances muscle protein synthesis, leading to greater gains in muscle mass and strength over time. However, it's important to note that individual factors such as age, training status, and nutritional habits can influence the effectiveness of this strategy.
What kind of recommendations would you make to an athlete trying to build muscle for protein intake: what kind of protein should they consume (and why), how much, how often?
1. Protein source: The athlete should consume high-quality protein sources such as lean meat, poultry, fish, eggs, dairy products, and plant-based sources such as soy, legumes, and nuts. These sources provide all essential amino acids required for muscle building and repair. 2. Protein intake: The athlete should consume an adequate amount of protein to support muscle building and recovery. Generally, it is recommended to consume between 1.4-2.0 grams of protein per kilogram of body weight per day for strength athletes. 3. Protein distribution: The athlete should aim to distribute protein intake evenly throughout the day, with 20-30 grams of protein per meal. This helps to maximize muscle protein synthesis and minimize muscle protein breakdown. 4. Timing: The athlete should consume protein before and after exercise to optimize muscle protein synthesis. Consuming protein before exercise can help provide amino acids for muscle building during exercise, while consuming protein after exercise can help promote muscle recovery and repair. 5. Supplementation: Athletes may also consider protein supplementation such as whey protein, casein, or plant-based protein powders to meet their protein needs. However, it is important to note that whole food sources should be the primary source of protein. It is recommended to consult with a registered dietitian or a healthcare professional to determine individual protein needs based on body weight, training status, and other factors.
What are 3 general purposes of protein breakdown?
1. Removal of damaged or abnormal proteins: Protein breakdown helps to remove abnormal, damaged or misfolded proteins that may be harmful to the body, as well as those that are no longer needed. 2. Regulation of protein levels: Protein breakdown helps to regulate the levels of specific proteins in the body, ensuring that they are maintained within the appropriate range for optimal function. 3. Amino acid supply: Protein breakdown provides a source of amino acids for use in protein synthesis and other metabolic processes. These amino acids can be used to build new proteins, to produce energy, or to synthesize other important molecules such as hormones and neurotransmitters.
Give a general overview of amino acid metabolism - What is transamination? What is deamination? What happens to the nitrogen? Describe the glucose-alanine cycle: what purpose does it serve? Where do amino acids enter oxidative metabolism?
1. Transamination is the transfer of an amino group from an amino acid to a keto acid, resulting in the formation of a new amino acid and a new keto acid. 2. Deamination is the removal of an amino group from an amino acid, resulting in the formation of a keto acid and ammonia. The ammonia is converted to urea in the liver and excreted in the urine. 3. The glucose-alanine cycle is a process by which skeletal muscle releases alanine into the bloodstream, which is taken up by the liver and converted to glucose via gluconeogenesis. This cycle helps to maintain blood glucose levels during prolonged exercise or fasting. 4. Amino acids can enter oxidative metabolism via several pathways, including the pyruvate dehydrogenase complex, the citric acid cycle, and the electron transport chain. Amino acids can also be converted to glucose via gluconeogenesis or used for fatty acid synthesis.
Give a general description of amino acids.
Amino acids are the building blocks of proteins, which are essential molecules for the structure and function of cells, tissues, and organs in the body. They are small organic molecules composed of an amino group (-NH2), a carboxyl group (-COOH), and a unique side chain (-R group) attached to a central carbon atom. There are 20 different types of amino acids commonly found in proteins, each with a unique side chain that determines its chemical properties and function. Amino acids can be classified as essential or non-essential, depending on whether they need to be obtained from the diet or can be synthesized by the body.
11 T.H. Which of the following proteins would you expect to have the fastest turnover?
Creatine kinase
Discuss the effect of exercise and feeding on protein synthesis and breakdown
During exercise, there is an increase in protein breakdown, which can lead to a negative protein balance if protein intake is insufficient. However, exercise also stimulates protein synthesis, especially if resistance exercise is performed. The magnitude and duration of the increase in protein synthesis depend on the type, intensity, and duration of the exercise. Feeding can also affect protein synthesis and breakdown. Consuming protein stimulates protein synthesis, which can last for several hours after feeding. The type and amount of protein consumed also play a role, with high-quality protein sources (e.g., whey protein) being more effective at stimulating protein synthesis than lower-quality sources. Combining exercise and feeding can have a synergistic effect on protein synthesis. Consuming protein after exercise can increase protein synthesis and improve muscle recovery and adaptation. Additionally, performing resistance exercise before feeding can enhance the anabolic response to feeding, further stimulating protein synthesis. Overall, it is important to consume adequate protein to support protein synthesis and prevent excessive protein breakdown, especially during periods of increased physical activity or training. Timing of protein intake, both in relation to exercise and throughout the day, can also play a role in optimizing protein synthesis and recovery.
11 T.H. Researchers use measurements of arterial and venous phenylalanine across a muscle to determine whether muscle synthesis, or muscle breakdown, predominates.If there is a net EFFLUX of phenylalanine, this tells us that:
Muscle protein breakdown predominates over synthesis
Explain why certain physiological conditions are associated with positive, and negative, nitrogen balance.
Nitrogen balance is a measure of the difference between the amount of nitrogen ingested in protein-containing foods and the amount excreted in urine and feces. A positive nitrogen balance occurs when nitrogen intake exceeds nitrogen excretion, indicating that there is a net retention of protein in the body. This is typically seen during periods of growth, such as childhood or pregnancy, and during recovery from injury or illness when the body is building new tissues. In these situations, protein synthesis exceeds protein breakdown, resulting in an increase in muscle mass. Conversely, a negative nitrogen balance occurs when nitrogen excretion exceeds nitrogen intake, indicating that the body is breaking down more protein than it is building. This is typically seen during periods of starvation, illness, or injury, as the body breaks down its own proteins to use as an energy source. Negative nitrogen balance can also occur during periods of high protein turnover, such as during intense exercise, when protein breakdown exceeds protein synthesis. Overall, the body aims to maintain nitrogen balance, as protein is a critical component of many tissues and organs. In order to maintain nitrogen balance, it is important to consume an adequate amount of dietary protein to support protein synthesis and to prevent excessive protein breakdown.
Discuss the contribution of protein to energy expenditure at rest and during exercise
Protein contributes to energy expenditure at rest and during exercise, but to a much lesser extent compared to carbohydrates and fats. At rest, protein accounts for about 5-10% of total energy expenditure. During exercise, the contribution of protein to energy expenditure increases slightly, depending on the intensity and duration of the exercise. During exercise, the primary sources of energy are carbohydrates and fats. Carbohydrates are the primary fuel source during high-intensity exercise, while fats become the primary fuel source during low- to moderate-intensity exercise. Protein oxidation can also increase during exercise, particularly during prolonged exercise or when carbohydrate stores are low. However, the contribution of protein to energy expenditure during exercise is generally low, ranging from 1-5% of total energy expenditure. It is important to note that the primary role of protein in the body is not to provide energy but to support growth, maintenance, and repair of tissues such as muscle, bone, and skin. Therefore, it is recommended that protein intake be adequate to meet these needs, rather than relying on protein as a primary source of energy during exercise.
Compare protein intake and excretion with actual proteinturnover
Protein turnover is the balance between protein synthesis and protein breakdown in the body. Protein intake is the amount of protein that is consumed through the diet, while protein excretion refers to the amount of protein that is eliminated from the body through urine and feces. Actual protein turnover refers to the net balance between protein synthesis and breakdown in the body, taking into account both protein intake and excretion. If protein intake is greater than protein excretion, the body is in a positive protein balance, and actual protein turnover is increased. On the other hand, if protein excretion is greater than protein intake, the body is in a negative protein balance, and actual protein turnover is decreased. It is important to note that protein turnover occurs at different rates depending on the body tissue. For example, muscle tissue has a relatively high turnover rate, while connective tissue has a relatively low turnover rate. Overall, protein turnover in the body occurs at a relatively fast rate, with estimates ranging from several days to weeks depending on the tissue type.
What is protein turnover? How fast does it occur?
Protein turnover is the continuous process of protein synthesis and degradation in the body. It refers to the balance between the rate of protein synthesis and the rate of protein breakdown. Protein turnover occurs at different rates for different proteins and tissues in the body. The average rate of protein turnover in the human body is about 250 to 300 g per day, which means that about 1-2% of the body's protein is synthesized and degraded each day.
Describe the leucine trigger concept
The leucine trigger concept is a nutritional theory that suggests that the amino acid leucine, which is abundant in protein-rich foods such as meat, poultry, fish, eggs, and dairy, can act as a key signal for muscle protein synthesis. According to this theory, when you consume protein, the leucine in that protein is metabolized by your body and triggers a cascade of signaling pathways that promote muscle protein synthesis, which is the process by which your body builds new muscle tissue. The leucine trigger concept suggests that in order to maximize muscle growth, you need to consume sufficient amounts of protein, with a high proportion of leucine. This is because leucine is believed to be the most potent of the three branched-chain amino acids (leucine, isoleucine, and valine) in terms of its ability to stimulate muscle protein synthesis. Therefore, the leucine trigger concept suggests that consuming high-quality protein sources with a sufficient amount of leucine, along with regular resistance training, can help to promote muscle growth and improve overall body composition.
Why is the nitrogen balance method not an optimal way to measure protein synthesis is muscle?
The nitrogen balance method is not an optimal way to measure protein synthesis in muscle because it does not distinguish between nitrogen intake and output from different sources. Nitrogen balance is calculated as nitrogen intake minus nitrogen output, where nitrogen intake is typically estimated from dietary protein intake, and nitrogen output is estimated from urine and fecal nitrogen excretion. However, this method does not account for nitrogen incorporation into protein or for losses of nitrogen due to other metabolic processes. In muscle, protein synthesis is the key process of interest, and nitrogen balance does not provide information about the specific contribution of protein synthesis to nitrogen balance. Therefore, other methods such as stable isotope tracer techniques are more appropriate for studying muscle protein synthesis.
Describe the recommendations for protein intake generally given for strength and endurance athletes
The recommendations for protein intake generally given for strength and endurance athletes are: 1. Strength athletes: 1.2-1.7 grams of protein per kilogram of body weight per day 20-40 grams of protein per meal, consumed every 3-4 hours Higher protein intake may be necessary during periods of intense training or when in a caloric deficit for weight loss purposes. 2. Endurance athletes: 1.2-1.4 grams of protein per kilogram of body weight per day Timing of protein intake is less critical than for strength athletes, but consuming protein immediately following a workout may aid in recovery and adaptation. It is important to note that individual protein needs may vary depending on factors such as body composition, training volume, and goals. In addition, consuming protein in combination with carbohydrates before and after exercise may enhance muscle protein synthesis and recovery.
How can we measure whether a given muscle is in an anabolic or catabolic state?
There are several methods to assess whether a muscle is in an anabolic or catabolic state: 1. Muscle protein synthesis (MPS) rate: MPS can be measured using stable isotope tracer techniques, such as the primed-continuous infusion of labeled amino acids. An increase in MPS indicates an anabolic state, while a decrease suggests a catabolic state. 2. Muscle protein breakdown (MPB) rate: MPB can be measured using tracer techniques, such as the infusion of a labeled amino acid. An increase in MPB indicates a catabolic state, while a decrease suggests an anabolic state. 3. Net protein balance (NPB): NPB is the difference between MPS and MPB. A positive NPB indicates an anabolic state, while a negative NPB suggests a catabolic state. 4. Muscle biopsies: Muscle biopsies can be used to measure the levels of specific proteins or enzymes involved in muscle protein synthesis and breakdown. For example, an increase in the expression of the mTOR signaling pathway suggests an anabolic state, while an increase in the expression of the ubiquitin-proteasome pathway suggests a catabolic state. 5. Functional assessments: Changes in muscle strength or size can also indicate whether a muscle is in an anabolic or catabolic state. An increase in muscle strength or size suggests an anabolic state, while a decrease suggests a catabolic state. Overall, a combination of these methods can provide a more comprehensive understanding of whether a muscle is in an anabolic or catabolic state.
Where do we obtain amino acids for most of the protein synthesis that occurs daily?
We obtain amino acids for most of the protein synthesis that occurs daily through the diet, particularly from dietary protein sources such as meat, fish, eggs, dairy products, and plant-based sources such as legumes, grains, and nuts.
What is mTOR? Name some factors that stimulate it and some that inhibit it.
mTOR (mechanistic target of rapamycin) is a protein kinase that regulates cell growth, protein synthesis, and autophagy. It is activated by a variety of factors, including growth factors (e.g., insulin, insulin-like growth factor 1), amino acids (especially leucine), and mechanical stress (e.g., resistance exercise). mTOR is inhibited by stress (e.g., nutrient deprivation, hypoxia), energy depletion (e.g., AMP-activated protein kinase), and some drugs (e.g., rapamycin). In summary: Factors that stimulate mTOR: Growth factors (insulin, IGF-1) Amino acids (especially leucine) Mechanical stress (e.g., resistance exercise) Factors that inhibit mTOR: Stress (e.g., nutrient deprivation, hypoxia) Energy depletion (e.g., AMP-activated protein kinase) Some drugs (e.g., rapamycin)
