Leucine (symbol Leu or L) is an essential amino acid that is used in the biosynthesis of proteins. Leucine is an α-amino acid, meaning it contains an α-amino group (which is in the protonated −NH3+ form under biological conditions), an α-carboxylic acid group (which is in the deprotonated −COO− form under biological conditions), and a side chain isobutyl group, making it a non-polar aliphatic amino acid. It is essential in humans, meaning the body cannot synthesize it: it must be obtained from the diet. Human dietary sources are foods that contain protein, such as meats, dairy products, soy products, and beans and other legumes. It is encoded by the codons UUA, UUG, CUU, CUC, CUA, and CUG.
Cachexia is a complex syndrome associated with an underlying illness causing ongoing muscle loss that is not entirely reversed with nutritional supplementation. A range of diseases can cause cachexia, most commonly cancer, congestive heart failure, chronic obstructive pulmonary disease, chronic kidney disease and AIDS. Systemic inflammation from these conditions can cause detrimental changes to metabolism and body composition. In contrast to weight loss from inadequate caloric intake, cachexia causes mostly muscle loss instead of fat loss. Diagnosis of cachexia can be difficult due to the lack of well-established diagnostic criteria. Cachexia can improve with treatment of the underlying illness but other treatment approaches have limited benefit. Cachexia is associated with increased mortality and poor quality of life.
Bodybuilding supplements are dietary supplements commonly used by those involved in bodybuilding, weightlifting, mixed martial arts, and athletics for the purpose of facilitating an increase in lean body mass. The intent is to increase muscle, increase body weight, improve athletic performance, and for some sports, to simultaneously decrease percent body fat so as to create better muscle definition. Among the most widely used are high protein drinks, pre-workout blends, branched-chain amino acids (BCAA), glutamine, arginine, essential fatty acids, creatine, HMB, whey protein, ZMA and weight loss products. Supplements are sold either as single ingredient preparations or in the form of "stacks" – proprietary blends of various supplements marketed as offering synergistic advantages. While many bodybuilding supplements are also consumed by the general public the frequency of use will differ when used specifically by bodybuilders. One meta-analysis concluded that – for athletes participating in resistance exercise training and consuming protein supplements for an average of 13 weeks – total protein intake up to 1.6 g/kg of body weight per day would result in an increase in strength and fat-free mass, but that higher intakes would not further contribute.
β-Hydroxy β-methylbutyric acid (HMB), otherwise known as its conjugate base, β-hydroxyβ-methylbutyrate, is a naturally produced substance in humans that is used as a dietary supplement and as an ingredient in certain medical foods that are intended to promote wound healing and provide nutritional support for people with muscle wasting due to cancer or HIV/AIDS. In healthy adults, supplementation with HMB has been shown to increase exercise-induced gains in muscle size, muscle strength, and lean body mass, reduce skeletal muscle damage from exercise, improve aerobic exercise performance, and expedite recovery from exercise. Medical reviews and meta-analyses indicate that HMB supplementation also helps to preserve or increase lean body mass and muscle strength in individuals experiencing age-related muscle loss. HMB produces these effects in part by stimulating the production of proteins and inhibiting the breakdown of proteins in muscle tissue. No adverse effects from long-term use as a dietary supplement in adults have been found.
Sarcopenia is a type of muscle loss that occurs with aging and/or immobility. It is characterized by the degenerative loss of skeletal muscle mass, quality, and strength. The rate of muscle loss is dependent on exercise level, co-morbidities, nutrition and other factors. The muscle loss is related to changes in muscle synthesis signalling pathways. It is distinct from cachexia, in which muscle is degraded through cytokine-mediated degradation, although both conditions may co-exist. Sarcopenia is considered a component of frailty syndrome. Sarcopenia can lead to reduced quality of life, falls, fracture, and disability.
Proteasome inhibitors are drugs that block the action of proteasomes, cellular complexes that break down proteins. They are being studied in the treatment of cancer; and three are approved for use in treating multiple myeloma.
Juice Plus+ is a branded line of dietary supplements containing concentrated fruit and vegetable juice extracts fortified with added vitamins and nutrients. It is produced by Natural Alternatives International of San Marcos, California, for National Safety Associates. Introduced in 1993, the supplements are distributed by NSA via multi-level marketing.
Muscle atrophy is the loss of skeletal muscle mass. It can be caused by immobility, aging, malnutrition, medications, or a wide range of injuries or diseases that impact the musculoskeletal or nervous system. Muscle atrophy leads to muscle weakness and causes disability.
β-Hydroxybutyric acid, also known as 3-hydroxybutyric acid, is an organic compound and a beta hydroxy acid with the chemical formula CH3CH(OH)CH2CO2H; its conjugate base is β-hydroxybutyrate, also known as 3-hydroxybutyrate. β-Hydroxybutyric acid is a chiral compound with two enantiomers: D-β-hydroxybutyric acid and L-β-hydroxybutyric acid. Its oxidized and polymeric derivatives occur widely in nature. In humans, D-β-hydroxybutyric acid is one of two primary endogenous agonists of hydroxycarboxylic acid receptor 2 (HCA2), a Gi/o-coupled G protein-coupled receptor (GPCR).
Calcifediol, also known as calcidiol, 25-hydroxycholecalciferol, or 25-hydroxyvitamin D3 (abbreviated 25(OH)D3), is a form of vitamin D produced in the liver by hydroxylation of vitamin D3 (cholecalciferol) by the enzyme vitamin D 25-hydroxylase. Calcifediol can be further hydroxylated by the enzyme 25(OH)D-1α-hydroxylase, primarily in the kidney, to form calcitriol (1,25-(OH)2D3), which is the active hormonal form of vitamin D.
β-Hydroxy β-methylglutaryl-CoA (HMG-CoA), also known as 3-hydroxy-3-methylglutaryl-CoA, is an intermediate in the mevalonate and ketogenesis pathways. It is formed from acetyl CoA and acetoacetyl CoA by HMG-CoA synthase. The research of Minor J. Coon and Bimal Kumar Bachhawat in the 1950s at University of Illinois led to its discovery.
Methylcrotonyl CoA carboxylase (MCC) is a biotin-requiring enzyme located in the mitochondria. MCC uses bicarbonate as a carboxyl group source to catalyze the carboxylation of a carbon adjacent to a carbonyl group performing the fourth step in processing leucine, an essential amino acid.
Isovaleryl-coenzyme A, also known as isovaleryl-CoA, is an intermediate in the metabolism of branched-chain amino acids.
3-Methylcrotonyl-CoA or β-Methylcrotonyl-CoA is an intermediate in the metabolism of leucine.
3-Methylglutaconyl-CoA (MG-CoA), also known as β-methylglutaconyl-CoA, is an intermediate in the metabolism of leucine. It is metabolized into HMG-CoA.
3-Methylglutaconyl-CoA hydratase, also known as MG-CoA hydratase and AUH, is an enzyme encoded by the AUH gene on chromosome 19. It is a member of the enoyl-CoA hydratase/isomerase superfamily, but it is the only member of that family that is able to bind to RNA. Not only does it bind to RNA, AUH has also been observed to be involved in the metabolic enzymatic activity, making it a dual-role protein. Mutations of this gene have been found to cause a disease called 3-Methylglutaconic Acuduria Type 1.
α-Ketoisocaproic acid (α-KIC) and its conjugate base, α-ketoisocaproate, are metabolic intermediates in the metabolic pathway for L-leucine. Leucine is an essential amino acid, and its degradation is critical for many biological duties. α-KIC is produced in one of the first steps of the pathway by branched-chain amino acid aminotransferase by transferring the amine on L-leucine onto alpha ketoglutarate, and replacing that amine with a ketone. The degradation of L-leucine in the muscle to this compound allows for the production of the amino acids alanine and glutamate as well. In the liver, α-KIC can be converted to a vast number of compounds depending on the enzymes and cofactors present, including cholesterol, acetyl-CoA, isovaleryl-CoA, and other biological molecules. Isovaleryl-CoA is the main compound synthesized from ɑ-KIC. α-KIC is a key metabolite present in the urine of people with Maple syrup urine disease, along with other branched-chain amino acids. Derivatives of α-KIC have been studied in humans for their ability to improve physical performance during anaerobic exercise as a supplemental bridge between short-term and long-term exercise supplements. These studies show that α-KIC does not achieve this goal without other ergogenicsupplements present as well. α-KIC has also been observed to reduce skeletal muscle damage after eccentrically biased resistance exercises in people who do not usually perform those exercises.
β-Hydroxy β-methylbutyryl-coenzyme A (HMB-CoA), also known as 3-hydroxyisovaleryl-CoA, is a metabolite of L-leucine that is produced in the human body. Its immediate precursors are β-hydroxy β-methylbutyric acid (HMB) and β-methylcrotonoyl-CoA (MC-CoA). It can be metabolized into HMB, MC-CoA, and HMG-CoA in humans.
Juven is a medical food that is manufactured by Abbott Laboratories and used to provide nutritional support under the care of a physician in individuals with muscle wasting due to AIDS or cancer, to promote wound healing following surgery or injury, or when otherwise recommended by a medical professional. It is a powdered nutritional supplement that contains 3 grams of calcium β-hydroxy β-methylbutyrate, 14 grams of L-arginine, and 14 grams of L-glutamine per two daily servings.
Pre-workout is a generic term for a range of bodybuilding supplement products used by athletes and weightlifters to enhance athletic performance. It is taken to increase endurance, energy, and focus during a workout. Pre-workout supplements contain a variety of ingredients such as caffeine and creatine, ranging by product. It can be taken in a variety of forms including capsules and powder. The first pre-workout entered the market in 1982, and since then they have grown in popularity. Some pre-workouts contain ingredients linked to adverse effects. Although these products are not banned, the Food and Drug Administration (FDA) warns consumers to be cautious when consuming pre-workout.
