Molecular vehicles for therapeutic delivery of lactate in exercise and medicine

Once thought of as a dead-end metabolite, the product of anaerobic, oxygen-limited metabolism, we now know that lactate is produced under fully oxygenated conditions, such as after consuming dietary carbohydrate and during physical exercise. Via shuttling mechanisms lactate is a preferred fuel energy source for red skeletal muscle, heart and brain. Consequently, lactate is being recognized as a major means of delivering non-insulin dependent carbohydrate-derived carbon around the body. Such recognition has led to consideration of developing enteral and parenteral means of lactate delivery. Enteral lactate delivery can be accomplished by providing fermented foods or high-glycemic index carbohydrates. Parenteral, intravenous (iv) lactate delivery can be accomplished by use of inorganic salts, such as sodium-L-lactate and other electrolyte mixtures appropriate for iv delivery. Enteral lactate delivery has been accomplished by using organic carriers that bind by electrostatic charge to zwitter ion amino acids. As well, it's possible to deliver lactate covalently bound to amino acids such as phenylalanine or glycerol. Some lactate-containing compounds such as LACTEM, sodium- and arginyl-lactate are Generally Recognized As Safe (GRAS) by the FDA for use in food, but other lactate-containing compounds are of unknown bioavailability and will need to pass FDA scrutiny. Enteral use of arginyl-lactate has been shown to be effective for improving performance of endurance athletes, and iv sodium-L-lactate for treatment of traumatic brain injury has reached Stage 2 clinical trials. Scientific background and possibilities of using lactate-containing compounds to achieve better outcomes by athletes or in illnesses and injuries is discussed.