Unraveling the avian paradox: Avian resistance to protein glycation

Abstract

Avian plasma glucose (PGlu) concentrations are naturally 1.5‐2 times those of mammals of similar body mass. Avian tolerance of exceptionally high PGlu is enigmatic considering that mammals with similar values would suffer severe pathologies stemming from hyperglycemia‐induced protein glycation. What is not currently known is how birds protect circulating proteins and the vasculature from high PGlu. The purpose of this study was to explore this “avian paradox.” Because protein glycation is an exothermic chemical process, we hypothesized that the unique physiology of birds (higher body temperatures than mammals) would help protect them from protein glycation. Since PGlu concentrations are inversely correlated with body mass, we measured percent glycated albumin in the plasma of three species of birds with varying body masses and body temperatures: house finches (Haemorhous mexicanus, 16‐27g, 42.5ºC), mourning doves (Zenaida macroura, 90‐130g, 41.5ºC) and mallard ducks (Anas platyrhynchos domesticus, 981‐1492g, 40.2ºC). Using top down mass spectrometry we discerned that PGlu does not predict albumin glycation demonstrating the generic, species agnostic nature of the avian paradox. In addition, birds with the highest body temperature (finches) have the lowest albumin glycation in comparison to doves and ducks (6.17±0.95%, 11.7±1.8%, 9.70±0.7%, respectively; p=0.05). These data support the hypothesis that higher body temperatures in birds may protect from protein glycation, which will be examined further through in vitro studies comparing percent glycation of avian and mammalian albumin.