A comprehensive comparative study indicates that certain birds have developed mechanisms to resist the detrimental effects of high blood sugar, offering valuable insights into metabolism and aging.
A large-scale study of 88 bird species has found that some birds with high blood sugar levels exhibit resistance to protein glycation, indicating they may have evolved mechanisms to mitigate the harmful effects commonly associated with glucose metabolism.
This study represents the first comprehensive comparative analysis of how blood sugar levels, glycation rates, diet, and life history interact in birds. Published as a revised Reviewed Preprint in eLife, the research provides strong evidence of a positive correlation between blood sugar levels and glycation. While the editors acknowledge some data collection limitations, they suggest these constraints likely make the statistically significant findings more conservative rather than overstated.
Understanding how different species regulate blood sugar is crucial for exploring the connections between metabolism, aging, and disease. High blood sugar is generally linked to accelerated aging and health issues, primarily due to protein glycation—a process in which sugars react with proteins, causing cellular damage.
The pace-of-life syndrome hypothesis proposes that an organism’s metabolic rate, lifespan, reproductive strategies, and behavior evolve in predictable ways. Under this framework, species with fast metabolisms, short lifespans, and high reproductive rates are expected to have higher blood sugar and glycation levels. Conversely, those with longer lifespans and slower developmental times should have lower blood sugar levels and greater resistance to glycation. However, it is unclear how glycation has coevolved with other traits across species, and so it is undetermined whether glycation fits into the framework of the pace-of-life hypothesis.
Birds as a Unique Case Study
“Birds are particularly relevant in this context, given their relatively high blood sugar levels – on average almost twice as high as similarly sized mammals,” says lead author Adrián Moreno-Borrallo, (PhD) at the Institut Pluridisciplinaire Hubert Curien, University of Strasbourg, CNRS, Strasbourg, France. “This is thought to be an adaptation allowing flight, providing birds with the fuel needed to power intense bursts of aerobic exercise. But it is also paradoxical. Despite their higher blood sugar levels, birds show remarkable longevity compared to their mammalian counterparts, living up to three times longer.”
To investigate this apparent paradox, Moreno-Borrallo and colleagues conducted an analysis of 484 individual birds from 88 different species. They compared blood sugar levels and glycation rates in relation to the birds’ life history traits – lifespan, body mass, developmental time, reproductive investment (measured by clutch mass – the total mass of their eggs), and diet. They sought to identify whether these species of birds followed the framework set by the pace-of-life syndrome hypothesis.
Their results revealed substantial variation in blood sugar levels across species. Smaller birds, such as swifts and passerines, had the highest blood sugar levels, while larger species, such as flamingos and geese, had the lowest. Glycation rates followed a similar trend, with smaller birds showing higher levels and larger birds displaying lower levels.
However, the relationship between blood sugar levels and lifespan was more complex. While longer-lived birds generally had higher blood sugar levels, this increase plateaued beyond a certain point. This suggests that some species have evolved mechanisms to prevent glycation-related damage, rather than avoiding high blood sugar levels altogether.
Another unexpected finding was that terrestrial carnivorous birds had significantly higher glycation rates than omnivorous birds, despite having similar blood sugar levels. This indicates that factors beyond blood sugar levels, such as differences in protein metabolism, antioxidant defenses, or dietary components including fiber and polyunsaturated fatty acids, may influence how different species are able to mitigate glycation-related damage.
Challenging the Pace-of-Life Hypothesis
The results challenge some predictions of the pace-of-life syndrome hypothesis. While body size showed a strong relation to blood sugar levels, reproductive investment showed no significant relationship with glycation, and glucose levels increased with lifespan instead of decreasing.
“Our results are only in minor agreement with predictions from the pace-of-life syndrome hypothesis. It holds true for body mass, but not for the other life-history variables tested,” says co-senior author Fabrice Bertile, a researcher at the Institut Pluridisciplinaire Hubert Curien, University of Strasbourg, CNRS, and the National Proteomics Infrastructure, ProFi, Strasbourg, France. “The link between blood sugar levels and lifespan may depend on species-specific factors that influence how glucose affects aging. Further research should target this area, as well as exploring other groups of birds that are underrepresented in our study due to logistical constraints.”
“These results increase our knowledge about the diversity of blood sugar levels and glycation patterns across birds, challenging conventional wisdom about metabolism, aging, and disease,” concludes co-senior author François Criscuolo, a researcher at the Institut Pluridisciplinaire Hubert Curien, University of Strasbourg, CNRS. “There is considerable variation in blood sugar levels and glycation rates between species, with those with the highest glucose levels showing greater resistance to glycation, hinting at an evolved mechanism for this resistance. Understanding how this glycation resistance arose could provide crucial insights in human health research, particularly in areas like diabetes, longevity, and metabolic disorders.”
Reference: “Variation in albumin glycation rates in birds suggests resistance to relative hyperglycaemia rather than conformity to the pace of life syndrome hypothesis” by Adrián Moreno-Borrallo, Sarahi Jaramillo-Ortiz, Christine Schaeffer-Reiss, Benoît Quintard, Benjamin Rey, Pierre Bize, Vincent A Viblanc, Thierry Boulinier, Olivier Chastel, Jorge S Gutiérrez, Jose A Masero, Fabrice Bertile and François Criscuolo, 3 December 2024, eLife.
DOI: 10.7554/eLife.103205.1
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