Recent evidence regarding the cardioprotective benefits of soy isoflavones has stimulated an increase in consumption of soy protein powders.
Structured Lipids- Increased Protein SynthesisAdvances in the technology behind lipid synthesis led to the development of structured lipids (SLs). A structured lipid (SL) is a triglyceride that includes both medium (8-12 carbons) and long-chain fatty acids (14-22 carbons) within the same triglyceride. Emulsions including SL have demonstrated increased protein synthesis and increased nitrogen balance (NB) in burned animals The SL has also been superior to medium-chain triglyceride (MCT) and long-chain triglyceride (LCT) emulsions in stimulating muscle protein synthesis in animal studies. The use of SLs has been primarily limited to clinical and experimental settings whereby it has become necessary to develop medical nutrition therapies that minimize the adverse effects of high lipid feedings and maximize the positive outcomes. Such positive outcomes include increased protein synthesis, enhanced immune function, decreased risk for cardiovascular disease, and improved glucose homeostasis. The ability to increase protein synthesis, maintain the health of the immune system, and stabilize blood glucose are factors that can also play a role in improving athletic performance. Research on the application of this clinical technology to athletic performance is not available at this time. Peptides- To Provide Glutamine to TPN PatientsIn an effort to provide glutamine to TPN patients in a form that can remain stable in liquid, the amino acid has been bonded with other amino acids, such as the dipeptide alanyl-glutamine. This combination can preserve muscle glutamine levels and muscle protein synthesis after surgery and improve whole-body nitrogen balance. This finding is supported by research on rats with peritonitis Alanylglutamine increased protein synthesis in the liver and skeletal muscle, protected the morphology of the intestinal mucosa, and improved survival in protracted bacterial peritonitis. The researchers concluded that alanylglutamine supplementation may be useful in septic patients.Role of Glutamine as Glucose Regulation The role of glutamine regarding glucose regulation may be important in exercise-trained individuals. Its function in gluconeogenesis (formation of glucose) and glycogen repletion may serve as a useful function during and after exercise. Gluconeogenesis from glutamine can occur without changes in plasma insulin and glucagon levels, providing evidence that glutamine itself can regulate gluconeogenesis.Nurjhan et al. compared the contribution of alanine and glutamine to glucose formation in postabsorptive (fasted) normal human volunteers and found that the amount of glucose carbon that came from proteinderived glutamine was 100% greater than from alanine. Varnier et al. studied the effects of glutamine, alanine plus glycine, and saline infusion on glycogen accumulation in subjects who cycled for 90 minutes. Two hours postexercise, glutamine infusion resulted in a twofold greater concentration of muscle glycogen than either saline or alanine plus glycine infusion. In postabsorptive humans, glutamine could be more important than alanine for glucose formation derived from proteolysis. Further, glutamine carbon can be directed to glycogen accumulation in skeletal muscle that had been previously glycogen depleted. In mice that were genetically predisposed to being overweight and hyperglycemic, the administration of glutamine in conjunction with a high-fat diet resulted in a reduction of body weight and a drop in hyperglycemia and hyperinsulinemia. The mechanism for a glutamineinduced weight reduction is not known, though it may be related to the ability of glutamine to lessen the insulin resistance induced by a high-fat diet. Further, the administration of glutamine to lipid-based TPN can prevent glucose intolerance and insulin resistance.