At a high level, it is fair to say that high blood glucose accelerates aging. The various forms of diabetes involve an excessively dysregulated glucose metabolism, and diabetics do exhibit accelerated aging. In the past, prior to the present greater focus on aging, researchers have even used diabetic mice as stand-ins for naturally aged mice to save time and funding. In comparison to mammals, birds have high blood glucose and relatively long life spans for their size. Is there anything to be learned from the comparative biology of birds and mammals in this context?
In today's open access paper, researchers discuss what the data on bird blood glucose might mean in terms of underlying mechanisms. It seems likely that birds possess mechanisms not present in mammals that allow them to resist the negative consequences of high blood glucose. Obviously this sort of review of the data is a very early starting point on the road to discovery and understanding of those mechanisms, even prior to any assessment regarding whether there is a useful basis for the production of therapies to bring that resistance to humans. One should not expect this research to move rapidly, given the slow pace of progress in other portions of the comparative biology field with much greater interest and funding, such as naked mole rat resistance to cancer.
The pace of life syndrome (POLS) hypothesis suggests that organisms' life history and physiological and behavioural traits should co-evolve. In this framework, how glycaemia (i.e. blood glucose levels) and its reaction with proteins and other compounds (i.e. glycation) covary with life history traits remain relatively under-investigated, despite the well-documented consequences of glucose and glycation on ageing, and therefore potentially on life history evolution. Birds are particularly relevant in this context given that they have the highest blood glucose levels within vertebrates and still higher mass-adjusted longevity compared to organisms with similar physiology as mammals.
We thus performed a comparative analysis on glucose and albumin glycation rates of 88 bird species from 22 orders in relation to life history traits (body mass, clutch mass, maximum lifespan, and developmental time) and diet. Glucose levels correlated positively with albumin glycation rates in a non-linear fashion, suggesting resistance to glycation in species with higher glucose levels. Plasma glucose levels decreased with increasing body mass, but, contrary to what is predicted in the POLS hypothesis, glucose levels increased with maximum lifespan before reaching a plateau. Finally, terrestrial carnivores showed higher albumin glycation compared to omnivores despite not showing higher glucose, which we discuss may be related to additional factors as differential antioxidant levels or dietary composition in terms of fibres or polyunsaturated fatty acids.
These results increase our knowledge about the diversity of glycaemia and glycation patterns across birds, pointing towards the existence of glycation resistance mechanisms within comparatively high glycaemic birds.
View the full article at FightAging
