Biology subjects

Moreno Borrallo, A.

Publications and source records attributed to Moreno Borrallo, A..

5 recordsLinked to original sources

bioRxiv2026

Glucose and methylglyoxal alter plasma protein dynamics, immune traits and glucose homeostasis in a sex- and season-dependent manner in zebra finches

Birds maintain unusually high circulating glucose levels compared with other vertebrates without developing the diabetic complications observed in mammals, yet the mechanisms underlying this resistance remain unclear. We investigated the effects of chronic glucose and methylglyoxal supplementation on physiological condition in zebra finches (Taeniopygia guttata), with particular emphasis on sex- and season-dependent variation in plasma biochemistry, haematology and immune traits. Ninety zebra finches (45 males, 45 females) were randomly assigned to control, glucose-supplemented (50 g/L), or methylglyoxal (8.33 g/L) drinking treatments. Over one year, we analysed plasma proteins, metabolites (glucose, uric acid, bile acids), tissue damage markers (AST, CK), electrolytes, and immune parameters (leukocyte profiles). Both supplementations increased plasma glucose concentrations, with methylglyoxal producing the strongest effect. More importantly, both treatments disrupted seasonal plasma protein dynamics, preventing the increase in total proteins and globulins normally observed in females during the reproductive period, which suggests alterations in reproductive-related protein metabolism. Glucose supplementation elevated the heterophil-to-lymphocyte (H/L) ratio in May and August, consistent with elevated physiological stress. In contrast, methylglyoxal supplementation reduced the H/L ratio in November and unexpectedly lowered plasma AST and CK concentrations in May, suggesting context-dependent protective effects on tissue integrity despite its well-established pro-oxidative properties, potentially through hormetic mechanisms. Supplementation also modified the calcium/phosphate balance, further supporting treatment effects on seasonal (reproductive) physiology. Overall, our findings demonstrate that glucose and methylglyoxal reshape physiological regulation in zebra finches in a strongly sex- and season-dependent manner rather than simply inducing generalized metabolic damage. These results provide new insights into avian resistance to glucose-associated physiological challenges and highlight the importance of considering both biological context and standardized haematological reference values when investigating glucose metabolism in birds.

physiology↗

bioRxiv2026

Contrasting effects of glucose and methylglyoxal supplementation on blood oxidative status, blood cells' telomere dynamics and apoptosis in birds

Birds exhibit longer lifespans than similarly sized mammals, despite having higher mass-adjusted blood glucose levels. This makes them a valuable model for the comparative study of the metabolic and physiological aspects of aging. Circulating glucose contributes to multiple pathological processes, primarily through glycation reactions and the formation of advanced glycation end-products (AGEs), as well as by promoting oxidative stress. These mechanisms are interconnected by feedback loops and play a key role in the development of age-related pathologies. To explore the causal role of glycaemia in avian ageing, we conducted a one-year dietary supplementation experiment in captive zebra finches. Birds received either glucose- or methylglyoxal-enriched water. Previously, we observed that chronic glucose supplementation in zebra finches increased mortality, an effect that did not appear to be mediated by the associated increase in plasma protein glycation or AGE levels. Therefore, the mechanisms underlying increased mortality in the glucose group remained unclear. In the present study, we investigated how glucose and methylglyoxal supplementation affect blood oxidative status and red blood cell telomere dynamics and apoptosis. We found that methylglyoxal supplementation decreased the non-enzymatic antioxidant capacity (OXY) of plasma and increased DNA damage, while glucose supplementation had no significant effect on oxidative stress, although circulating glucose levels influenced oxidative status in a sex-dependent manner. Males exhibited a positive correlation between glucose levels and organic hydroperoxides and protein carbonyls. Additionally, we report, for the first time in birds, a seasonal variation in telomere length, which was more pronounced in glucose-supplemented individuals, yet seemed independent of oxidative status. Apoptosis probability increased with both treatments, particularly with the methylglyoxal supplementation. These results highlight that glucose and methylglyoxal trigger different glucotoxicity-related pathways, with distinct effects on bird health and aging. However, the relationship between glucose supplementation and mortality remains still unclear and warrants further investigation.

physiology↗

bioRxiv2026

Decoupling glycation from mortality: glucose, but not methylglyoxal, reduces survival in zebra finches

Birds provide a unique model for ageing research, with greater longevity and slower senescence compared to mammals of similar body size, despite a higher mass-adjusted metabolic rate and blood glucose levels than other vertebrate groups. While the effects of glucose, glycation, and advanced glycation end-products (AGE) on ageing are well-documented in biomedical research, their impact on avian physiology and ageing remains poorly understood. Although birds may possess adaptations mitigating the potential detrimental effects of glucose, elevated glucose still predicts reduced lifespan, and protein glycation varies with age and can influence survival and some fitness-related traits, implying that glycation or AGE accumulation may have relevant effects on avian longevity. In this study, we experimentally investigated how one year of dietary supplementation with glucose or methylglyoxal affects survival and physiology (metabolic rate, flying performance, and beak coloration) in captive zebra finches (Taeniopygia guttata). We reveal a significant increase in mortality exclusively in glucose-supplemented birds, with also an elevated albumin glycation rate and AGE formation. However, these variables did not directly explain the increased mortality, which was also absent in methylglyoxal-treated individuals, despite similar AGE accumulation. Additionally, we observed some other effects, like an age-related constraint on seasonal metabolic adjustment, a treatment-influenced age decline in secondary sexual traits expression, and a decline in flight performance during the peak mortality period, suggesting a broader deterioration of health. Thus, although we demonstrate glucose supplementation to be more deleterious than methylglyoxal, the underlying mechanisms for the increase in mortality induced by the treatment remain unresolved.

physiology↗

bioRxiv2024

Glycaemia and albumin glycation rates as fitness mediators in the wild: the case of a long-lived bird

Glucose is a vital metabolic component in the functioning of organisms, but it can also bind to biomolecules through non-enzymatic glycation reactions that result in loss of functions. While the effects of glycation on health have been well demonstrated in biomedical research, little is known about the effects of glycation in wild animals. Here, we studied how plasma glucose levels and albumin glycation rates vary with age and are related to fitness in a relatively hyperglycaemic long-lived bird, the Alpine swift (Tachymarptis melba). We measured plasma glucose and albumin glycation levels before and after reproduction in adult females of known age (2-14 years), showing that, while glucose levels increased in parallel with body mass, albumin glycation rates decreased within this period. Albumin glycation, but not glucose, varies with age, peaking at 5 years, consistently with other age-related parameters previously reported in this species. Interestingly, higher plasma glucose levels before reproduction were related to increased fledging success up to a certain threshold. In addition, in terms of dynamics, females gaining more mass lowered more their glycation levels, while those gaining less mass and lowering the more their glycation levels laid more eggs. Finally, higher body mass and plasma glucose levels after reproduction predicted a higher survival probability to the next season, whereas higher albumin glycation predicted lower survival, although in an age-dependent manner. Our study highlights adult plasma glucose and glycated albumin levels as new potential markers of ageing and fitness that should be further explored in this species.

evolutionary biology↗

bioRxiv2024

Understanding glycaemia and glycation levels in birds: diet and life history traits associations

The pace of life syndrome hypothesis (POLS) suggests that organisms life history, 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 when 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 to 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.

evolutionary biology↗