In the defence against hyperglycaemia: an avian strategy

Abstract

Birds live longer than mammals of comparable sizes, contrary to what their metabolic rates, plasma glucose concentrations and body temperatures, all of which are higher than mammalian norms, would suggest. Although these factors should predispose them to accelerated tissue degeneration, this has been shown not to happen. In this paper the possible mechanisms whereby birds limit the accelerated tissue damage that should be associated with the above characteristics are explored. Specifically, this review will focus on the relationship in chickens between the raised concentrations of plasma glucose and the lack of associated tissue complications. We propose that the role of uric acid in birds should be re-examined. Until now uric acid has been considered to be little more than an excretory by-product where its role as an antioxidant can be directly linked to the resistance of birds to glucose-mediated tissue damage. It is suggested that, compared with mammals, the lower rate of generation of reactive oxygen species in birds in association with their stronger antioxidant-defence system contributes to their longevity.

Keywords:

• Birds
• hyperglycaemia
• free radicals
• oxidative stress
• longevity
• utric acid
• AGEs
• pentosidine