Influence of adiposity (genetic or hormonal) on the metabolism of amino acids and nutritional responses.

The data published on the modifications of amino-acid metabolism associated with variations of obesity from genetic or hormonal origin have been reviewed. In the first part monogenic models of mice and rats are described. Obesity in humans is analysed in the second part. Lastly, non-ruminant genotypes or hormone-treated ones (chickens and pigs) are reviewed in the third part. Although different mechanisms are probably at the origin of these differences, many similarities can be drawn. Obesity is always associated with: 1) less efficient utilization of dietary amino acid; 2) a high concentration of branched-chain amino acids in plasma; 3) a deviation of carbon from amino acid towards gluconeogenis and lipogenesis; and 4) a less pronounced sensitivity to amino-acid imbalance in the diet.