Protein Metabolism

To compare postprandial plasma amino acid availability, expressed as incremental area under the curve (iAUC), over a 6 hour period following ingestion of 25 g of different protein isolates in healthy, young adults. The primary objective is divided into the following 2 sub-studies, each with 3 comparisons: * Sub-study 1: whey protein, calcium caseinate, sodium caseinate. * Sub-study 2: calcium caseinate, magnesium caseinate, potassium caseinate.

In a crossover design, 8 participants will receive caloric drinks containing stable isotopes. In one arm of the study, participants will consume 6 hourly drinks containing two stable isotopes. Repeated blood, breath, urine, and muscle biopsies will be taken. In the second arm, participants will consume 1 drink containing 75g glucose, labeled with two stable isotopes of glucose. Periodic blood and breath will be taken over three hours.

In the present semi-crossover randomized design, 15 recreationally active young adults (19-40 y) will receive stable isotope tracer infusions and perform a single bout of resistance exercise. Immediately after exercise, participants will ingest either 1 medium russet potato with skins and 2 ounce-equivalent lean ground beef combination (274 kcals, 19.3 g protein, 5 g fat, 37 g carbohydrates, and 4 g fiber), 2 slices of white bread and beef combination (262 kcals, 19.8 g protein, 6.8 g fat, 28 g carbohydrates, and 1.8 g fiber) or 2 ounce-equivalent beef (93% lean meat/7% fat; 110 kcals, 14.8 g protein, and 5 g fat). Repeated blood and muscle biopsies will be collected to determine whole body leucine kinetics, amino acid concentrations, anabolic signaling and myofibrillar protein synthesis rates during the trials.

The purpose of this study is to assess the digestion and absorption kinetics of beef consumed alone or as part in healthy adults. In a randomized, crossover design, 10 young, healthy adult males and females aged 18-35 years, will consume a meal consisting of 25 g protein from minced beef alone or as part of a mixed-meal during two separate experimental trials. The main study endpoint is the exogenous rate of amino acid appearance in response to the ingested beef over a 10-h period.

The purpose of this study is to assess the optimal protein intake to maximize whole-body protein net balance in healthy adults. In a randomized, double-blinded, crossover design, 12 young, healthy adult males and females aged 18-35 years, will consume a test diet consisting of free amino acid mixtures based on milk protein that vary in protein content 7 separate acute metabolic trials. The main study endpoint is optimal protein intake based on the lowest protein intake that maximizes whole-body protein net balance.

The purpose of this study is to assess the amino acid oxidation dose-response relationship of ingested whole-food protein in healthy adults. In a randomized, crossover design, 20 young, healthy adult males and females aged 18-35 years, will consume a dinner consisting of 0.32, 0.74, and 1.32 g protein･kg BM-1 (corresponding to 1, 2, and 4 minced beef patties, respectively) during 3 separate experimental trials.The main study endpoint is the amino acid oxidation of ingested protein over a 24-h period.

Consuming dietary protein stimulates whole-body and muscle protein synthesis, the latter of which is typically measured using invasive primed constant infusions of stable isotopes with concurrent muscle biopsies. Alternative non-invasive methodologies have been developed (namely the indicator amino acid oxidation (IAAO) technique) to estimate the impact of protein ingestion on whole-body protein synthesis as a proxy for determining dietary protein requirements. Given that the IAAO technique is based on principles of protein metabolism which occur in the liver, it is unclear how representative the IAAO outcomes of whole-body protein synthesis is to skeletal muscle protein synthesis. Validation of the IAAO technique against gold-standard, biopsy-derived measures of muscle metabolism (i.e., muscle protein synthesis) would assist in mitigating the invasiveness of muscle physiology and nutrition research.

The muscles of the body are constantly breaking down old proteins and building new ones. These two processes, protein breakdown and protein synthesis, together are known as protein turnover. Protein turnover is essential for maintaining healthy muscle. Despite its importance, females have historically been underrepresented in protein metabolism research. A long-standing assumption has been that fluctuations in female sex hormones such as estrogen and progesterone, whether across the natural menstrual cycle or in individuals using oral contraceptives (OCs), make metabolism and training responses too variable to study. Because of this, many researchers have excluded female participants for logistical reasons. Resistance exercise, such as weightlifting, is the most effective way to increase muscle size and strength. Each resistance-training session triggers muscle protein synthesis (MPS), the process by which new muscle proteins are built. Consuming dietary protein or individual amino acids further increases the rate at which new proteins are formed. Over time, higher rates of protein synthesis support muscle growth and the maintenance of other lean tissues in the body. The purpose of this study is to examine how menstrual cycle phases and OC use influence the synthesis of proteins in both muscle tissue and the rest of the body. Improving scientific understanding in this area will support more effective, evidence-based training and nutrition recommendations for females.

Frailty is a common clinical syndrome in older adults that increases the risk for poor health outcomes including falls, disability, hospitalization, and mortality. Previous research showed increased protein needs and reduced anabolic response to meals in older adults, indicating the need for proteins with a high anabolic capacity to prevent and attenuate physical and cognitive health decline throughout the frailty cycle. Recently, more people have chosen to eliminate animal (i.e., beef) products from their diets which is concerning because of beef's anabolic properties due to high essential amino acid (EAA) levels and many other positive health effects. The Researchers' recently developed stable isotope amino acid pulse method enables measurement of the true intracellular anabolic response to a meal and bioavailability of food-derived amino acids. The research objective is to examine differences in the anabolic response and bioavailability of individual EAA and non-essential amino acids (NEAA) in beef as compared to plant protein in older adults with and without (pre-)frailty.

The researchers overall objective is to determine whether plant and animal protein based proteins affect the anabolic responses across aging populations differently due to specific changes in the essential amino acids (EAA) and non-essential amino acids (NEAA) kinetic responses. The researchers central hypothesis is that a high EAA to NEAA ratio in a protein meal is related to higher anabolic response to the meal. The researchers also hypothesize that the type of NEAA in a protein meal also affects the anabolic capacity of the meal. The researchers rationale is that finding the amino acid composition of a meal that will maximally induce protein anabolism will guide novel nutritional approaches to prevent and treat sarcopenia, thereby reducing both overall economic burden and improving individual patient outcomes.

Previous studies suggest that changes in metabolism due to the effects of aging might serve as a potential for therapeutic agents. The investigating lab developed a pulse method combining multiple stable isotopes to study multiple metabolic pathways in the same individual simultaneously. By measuring whole-body metabolism in a large group of older adults, the investigators may be able to unravel age-related deterioration in protein turnover (synthesis and breakdown) that contributes to impaired functional capacity. Metabolic profiles could explain differences in pathways in the aging process with special interest in metabolism of amino acids as they have been associated with aging-related disorders.

Given the relatively high carbon footprint and sustainability of animal-based proteins, there is a growing interest in determining the nutritional quality non-animal-based protein sources. The overall objective of this investigation is to examine the impact of different animal and microbial-based protein sources to support whole body protein synthesis in adults. To do this, investigators will employ a 'breath test' method developed in our laboratory as well as urine sampling. The results of this study will allow us to better understand the impact of dietary protein quality for maintaining health and body protein mass in adults.

Dietary protein intake is essential for tissue renewal and growth. Current recommendations for protein intake are based on studies using egg protein as reference protein. Egg protein is an animal-based protein with a high quality. Protein quality is determined by the composition of (essential) amino acids and digestibility. Therefore, different proteins have a different quality. Due to the environmental crisis, an increasing number of people consumes more plant-based proteins. These plant-based proteins often have a lower protein quality compared to animal-based proteins. Therefore, the aim of this study is to investigate whether optimal protein intake depend on protein quality. The optimal protein intake of an animal-based protein with a high quality (milk) will be compared to the optimal protein intake of a plant-based protein with a low quality (wheat).

The purpose of this study is to determine how anabolic sensitivity, in response to the ingestion of a liquid protein meal, differs across the lifespan, between biological sexes, and with varying physical activity levels.

Current recommendations for protein intake after bariatric surgery are not based on strong scientific evidence. It remains unclear how much protein should be eaten to minimize muscle loss and preserve the metabolism and function of individuals post-bariatric surgery. The objective of this study is to analyze the relationships between changes in body composition, nutrition and protein intake, and muscle function after bariatric surgery to further our understanding of the nutritional needs of patients after bariatric surgery. We intend to recruit around 75 participants, men and women, aged between 18 and 65 years. Participants will be recruited from the Bariatric Surgery Clinic, McGill University Health Center.