![[Feedback]](/icons/banner/feedbackACT.gif){kind=icon}
![[For Subscribers]](/icons/banner/subscriberACT.gif){kind=icon}
![[Archive]](/icons/banner/archiveACT.gif){kind=icon}
![[Search]](/icons/banner/searchACT.gif){kind=icon}
![[Contents]](/icons/banner/tocACT.gif){kind=icon}
|
|
|
|
|
||
INRA, Unité Mixte de Recherches sur le Veau et le Porc, 35590 Saint-Gilles, France
2To whom correspondence should be addressed. E-mail: jaap{at}st-gilles.rennes.inra.fr.
A framework representing the major biochemical pathways of nutrient metabolism is developed allowing quantification of the energy efficiency of different nutritional scenarios. The model is based on a number of carbon chain pivots (glucose, pyruvate, acetyl coenzyme A, 
-ketoglutarate, oxaloacetate and serine) and cofactors involved in metabolism. Excess pivots yield acetyl coenzyme A, which may be used for ATP or lipid synthesis. In contrast to previous work of this kind, the framework was constructed so that new insights in nutrient metabolism can be easily incorporated. Traditionally, integral values have been used to quantify mitochondrial ATP synthesis from cofactors (i.e., 3 ATP/NADH and 2 ATP/FADH2), but current estimates are approximately 0.20 lower than previously assumed. Based on the latter, the energy expenditure for ATP synthesis from glucose was 91.0 kJ/ATP. For lipid (tripalmitin), 96.3 kJ/ATP was required whereas for amino acids energy expenditures varied between 99.2 (glutamate) and 153.2 kJ/ATP (cysteine). Energy derived from amino acid catabolism is stored and transferred either via carbon chain pivots or cofactors. It is hypothesized that this may affect the ultimate utilization of this energy (e.g., for ATP or lipid synthesis). The energy cost of nitrogen transport appeared relatively modest for most nonessential amino acids. Likewise, the net cost of using dietary glutamate and glutamine for ATP synthesis (e.g., in the viscera) and de novo synthesis of these amino acids in muscle is relatively minor and of similar magnitude as the cost of storing glucose energy as glycogen.
KEY WORDS: • energy efficiency • nutritional models • nutrient utilization • biochemistry
This article has been cited by other articles:
|
|
 |
|
  S. Lemosquet, G. Raggio, G. E. Lobley, H. Rulquin, J. Guinard-Flament, and H. Lapierre Whole-body glucose metabolism and mammary energetic nutrient metabolism in lactating dairy cows receiving digestive infusions of casein and propionic acid J Dairy Sci, December 1, 2009; 92(12): 6068 - 6082. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Hochstenbach-Waelen, M. S. Westerterp-Plantenga, M. A. B. Veldhorst, and K. R. Westerterp Single-Protein Casein and Gelatin Diets Affect Energy Expenditure Similarly but Substrate Balance and Appetite Differently in Adults J. Nutr., December 1, 2009; 139(12): 2285 - 2292. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. A. Veldhorst, M. S Westerterp-Plantenga, and K. R Westerterp Gluconeogenesis and energy expenditure after a high-protein, carbohydrate-free diet Am. J. Clinical Nutrition, September 1, 2009; 90(3): 519 - 526. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Lemosquet, E. Delamaire, H. Lapierre, J. W. Blum, and J. L. Peyraud Effects of glucose, propionic acid, and nonessential amino acids on glucose metabolism and milk yield in Holstein dairy cows J Dairy Sci, July 1, 2009; 92(7): 3244 - 3257. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. M. Ross-Inta, Y.-F. Zhang, A. Almendares, and C. Giulivi Threonine-deficient diets induced changes in hepatic bioenergetics Am J Physiol Gastrointest Liver Physiol, May 1, 2009; 296(5): G1130 - G1139. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Noblet and J. van Milgen Energy value of pig feeds: Effect of pig body weight and energy evaluation system J Anim Sci, January 1, 2004; 82(13_suppl): E229 - 238. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. van Milgen and J. Noblet Partitioning of energy intake to heat, protein, and fat in growing pigs J Anim Sci, February 1, 2003; 81(14_suppl_2): E86 - 93. [Abstract] [Full Text] [PDF]
|
|
