High blood sugar is generally considered to be a bad thing, unless you are a bird. ‘Birds have outstandingly high blood glucose levels in normal physiological state, on average two to four times higher than that of similar-sized mammals’, says Csongor Vágási from Babeş-Bolyai University, Romania, who explains that humans with similar blood sugar levels are at risk of diabetes, which can damage many organs and tissues. But how do songbirds avoid the physiological risks of their surprisingly high blood sugar? ‘Researchers think that species with high blood sugar levels are better equipped to protect themselves from the cellular damages that high levels of blood glucose might otherwise cause’, says Vágási. So, he and his colleagues decided to measure the blood sugar levels and the quantities of antioxidant chemicals – including uric acid and glutathione – in the blood of 51 European songbird species, ranging from common rosefinches (Carpodacus erythrinus) to bearded reedlings (Panurus biarmicus), to find out whether species with particularly high blood sugar levels require more antioxidants for protection.
However, after almost a decade of gently catching over 1700 birds in the Czech Republic and Romania – with the help of an army of volunteers – painstakingly collecting minute blood samples before releasing the unharmed birds back into the wild, it was clear that the species with higher blood glucose levels did not necessarily have higher quantities of antioxidants for protection. In addition, they did not seem to suffer the elevated levels of cell damage that would be expected for creatures with high blood sugar.
‘The results of this research are in agreement with the idea that birds can avoid the adverse consequences of high blood glucose and hence do not need better antioxidant protection’, says Vágási. And he adds that the mechanisms that offer birds protection from the damaging effects of high blood sugar could also have allowed them to evolve their lengthy lifespans, which are far longer than you would expect for creatures of their size.
