ATP, the currency of cellular energy metabolism, can be produced during aerobic and an-aerobic oxidation of metabolic substrates. The aerobic oxidation yields CO2 + H2O as metabolic end products while ATP is produced by oxidative phosphorylation in the mitochondria. Carbohydrate, protein and fat provide a similar amount of 12-13 ATP/MJ ME when the ME is based on their value as body constituent. The energetic efficiency is 42-43 percent. In the anaerobic mode, for glucose only, ATP is produced by substrate level phosphorylation during cytoplasmic glycolysis, the normal first step in the aerobic oxidation of glucose. However, under an-aerobic conditions cytoplasmic glycolysis produces lactate which requires one of two ways of aerobic clearance to avoid lactic acidosis. The 'ketogenic clearance' re-channels the lactate in aerobic oxidation of glucose, but elsewhere in the body. This ketogenic clearance can contribute to the normal ATP-requirement of the whole body, but causes a move to carbohydrate as energy substrate. If necessary these carbohydrates can be produced from body protein, with a decrease in the energetic efficiency to 29 percent. The "glucogenic clearance" re-cycles the lactate to glucose. This glucogenic pathway (Cori cycle) further lowers the energetic efficiency of ATP-production for peripheral use to 14.1 percent. The Cori cycle requires extra ATP and causes a move to fat as energy substrate. This desk study shows that the energetic efficiency of ATP-production for peripheral use will range between 14-43 percent depending on the need and availability of glucose. It is suggested that these results could be used to develop specific nutritional, physiological and environmental strategies to benefit physical fitness and weight management in daily practice.
|Journal||Agro Food Industry Hi-Tech|
|Publication status||Published - 2007|