Chicken albumin exhibits natural resistance to glycation

Glycation resistance and life-history traits: lessons from non-conventional animal models

Glycation reactions play a key role in the senescence process and are involved in numerous age-related pathologies, such as diabetes complications or Alzheimer's disease. As a result, past studies on glycation have mostly focused on human and laboratory animal models for medical purposes. Very little is known about glycation and its link to senescence in wild animal species. Yet, despite feeding on high-sugar diets, several bat and bird species are long-lived and seem to escape the toxic effects of high glycaemia. The study of these models could open new avenues both for understanding the mechanisms that coevolved with glycation resistance and for treating the damaging effects of glycations in humans. Our understanding of glycaemia's correlation to proxies of animals' pace of life is emerging in few wild species; however, virtually nothing is known about their resistance to glycation, nor on the relationship between glycation, species' life-history traits and individual fitness. Our review summarizes the scarce current knowledge on the links between glycation and life-history traits in non-conventional animal models, highlighting the predominance of avian research. We also investigate some key molecular and physiological parameters involved in glycation regulation, which hold promise for future research on fitness and senescence of individuals.

Effects of Chicken Serum Metabolite Treatment on the Blood Glucose Control and Inflammatory Response in Streptozotocin-Induced Type 2 Diabetes Mellitus Rats

Chickens can live healthy without adverse effects despite high blood glucose levels. However, the blood biomolecules responsible for maintaining chronic hyperglycemia are unknown. Here, the effects of chicken serum metabolite treatment on blood glucose control and inflammatory response in streptozotocin (STZ)-induced Type 2 Diabetes Mellitus (T2DM) rats were investigated. First, chicken serum treatment reduced the advanced glycation end-products (AGEs) and blood glucose levels in STZ-induced T2DM rats. Second, insulin/glucose-induced acute hypoglycemic/hyperglycemic chickens and the blood biomolecules were screened via nontargeted ultra-performance liquid chromatography with mass spectroscopy (UPLC-MS), identifying 366 key metabolites, including DL-arginine and taurine, as potential markers for chronic hyperglycemia in chickens. Finally, DL-arginine functions for blood glucose control and inflammatory response were evaluated. We found that DL-arginine reduced the levels of blood glucose and AGEs in STZ-induced T2DM rats. In addition, DL-arginine treatment upregulated the glucose transporter type 4 (GLUT4) expression in the muscles and downregulated the advanced glycation end products receptor-1 (AGER1) expression in the liver and nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK) expression in the pancreas and thymus tissues. Overall, these results demonstrate that serum metabolite of DL-arginine could maintain blood glucose homeostasis and suppress the inflammatory response in chickens. Therefore, DL-arginine may be a novel target for developing therapeutic agents to regulate hyperglycemia.

Effect of macronutrient and micronutrient manipulation on avian blood glucose concentration: A systematic review

Animals with natural protections against diabetes complications may provide clues to improve human health. Birds are unique in their ability to avoid hyperglycemia-associated complications (e.g., glycation and oxidative stress) despite having naturally high blood glucose (BG) concentrations. This makes them useful models to elucidate strategies to prevent and/or treat diabetes-related complications in mammals. As diet plays a key role in BG concentration and diabetes risk, this systematic review aimed to summarize the effects of macro and micronutrient manipulation on avian BG. Three databases were searched (PubMed, SCOPUS, and Web of Science) for articles that met inclusion criteria: altered at least one nutrient and measured BG in at least one avian species. The search yielded 91 articles that produced 128 datasets (i.e., one nutrient manipulation in one sample). Across all macronutrient manipulations (n = 69 datasets), 62% reported no change in BG and 23% measured an increase (p < 0.001). Within the macronutrient groups (carbohydrate, lipid, protein, and mixed) most datasets showed no change in BG (67%, 62%, 52%, and 86%, respectively). Across micronutrient manipulations (n = 59 datasets), 51% demonstrated no change and 41% decreased BG (p < 0.001). While manipulations that altered vitamin intake largely produced no change in BG (62%), 48% of datasets examining altered mineral intake found no change and 46% decreased BG. Chromium was the most studied micronutrient (n = 24 datasets), where 67% of datasets reported a decrease in BG. These results suggest birds are largely able to maintain blood glucose homeostasis in response to altered nutrient intake indicative of dietary flexibility.

Revisiting glucose regulation in birds - A negative model of diabetes complications

Birds naturally have blood glucose concentrations that are nearly double levels measured for mammals of similar body size and studies have shown that birds are resistant to insulin-mediated glucose uptake into tissues. While a combination of high blood glucose and insulin resistance is associated with diabetes-related pathologies in mammals, birds do not develop such complications. Moreover, studies have shown that birds are resistant to oxidative stress and protein glycation and in fact, live longer than similar-sized mammals. This review seeks to explore how birds regulate blood glucose as well as various theories that might explain their apparent resistance to insulin-mediated glucose uptake and adaptations that enable them to thrive in a state of relative hyperglycemia.

Resistance to glycation in the zebra finch: Mass spectrometry-based analysis and its perspectives for evolutionary studies of aging

In humans, hyperglycemia is associated with protein glycation, which may contribute to aging. Strikingly, birds usually outlive mammals of the same body mass, while exhibiting high plasma glucose levels. However, how birds succeed in escaping pro-aging effects of glycation remains unknown. Using a specific mass spectrometry-based approach in captive zebra finches of known age, we recorded high glycaemia values but no glycated hemoglobin form was found. Still, we showed that zebra finch hemoglobin can be glycated in vitro, albeit only to a limited extent compared to its human homologue. This may be due to peculiar structural features, as supported by the unusual presence of three different tetramer populations with balanced proportions and a still bound cofactor that could be inositol pentaphosphate. High levels of the glycated forms of zebra finch plasma serotransferrin, carbonic anhydrase 2, and albumin were measured. Glucose, age or body mass correlations with either plasma glycated proteins or hemoglobin isoforms suggest that those variables may be future molecular tools of choice to monitor glycation and its link with individual fitness. Our molecular advance may help determine how evolution succeeded in associating flying ability, high blood glucose and long lifespan in birds.

Reduced cellular glucose transport confers natural protection against dextrose-induced superoxide generation and endoplasmic reticulum stress in domestic hen

Normal blood glucose levels in avian species are two to fourfold higher than that in humans and the higher blood glucose levels in birds do not cause adverse effects. Endothelial cells isolated from the aorta of the domestic hen (Gallus gallus domesticus) and chicken aortic smooth muscle cells (CAOSMC) were compared to human coronary artery endothelial cells (HCAEC) and human primary aortic smooth muscle cells (HASMC). Superoxide (SO) generation was measured using a superoxide‐reactive probe. ER stress was measured using the placental alkaline phosphatase assay (ES‐TRAP). Glucose transport kinetics were determined using the ³H‐2‐deoxyglucose tracer. Dextrose‐induced SO generation and ER stress were significantly blunted in avian endothelial cells compared to human cells. The Vmax of glucose uptake (in nmoles/mg protein/min) in avian endothelial cells (0.0018 ± 0.0001) and smooth muscle cells (0.0015 ± 0.0007) was approximately 18–25 fold lower compared to the Vmax in HCAEC (0.033 ± 0.0025) and HASMC (0.038 ± 0.004) (all p < 0.0001). The Michaelis–Menten constant (Km) of transport was also significantly different (p < 0.0001) in avian species. The relative resistance of avian cells to dextrose‐induced oxidative stress and ER stress is mostly the result of reduced cellular dextrose transport.

Fewer Exposed Lysine Residues May Explain Relative Resistance of Chicken Serum Albumin to In Vitro Protein Glycation in Comparison to Bovine Serum Albumin

Protein glycation and formation of advanced glycation end products is associated with several diseases resulting from high blood glucose concentrations. Plasma albumin is directly exposed to circulating glucose concentrations and is therefore at greater risk of glycation than hemoglobin. As plasma glucose concentrations in birds are 1.5-2 times higher than mammals of similar mass, avian albumin may be particularly at risk of glycation. Thus, the goal of the present study was to compare the in vitro formation of glycated albumin in chicken serum albumin (CSA) and bovine serum albumin (BSA) exposed to a range of glucose concentrations over a 16-week period. The level of glycation for CSA and BSA was quantified using boronate affinity columns to separate glycated albumin from non-glycated albumin and calculating the difference in protein concentration of each sample. The results indicate that CSA is glycated to a lesser degree than BSA when the albumins are exposed to increasing concentrations of glucose (38.8-500 mM). This was most apparent at week sixteen (500 mM glucose) where BSA expressed a higher degree of glycation (37.8 ± 0.76%) compared to CSA (19.7 ± 1.06%, P < 0.05). Additionally, percent glycation at week sixteen was significantly higher than the glucose-free solutions for both BSA and CSA, indicating that glycation is glucose-dependent. Analyses of the protein structures suggest that the relative resistance of CSA to glycation may be due to fewer lysine residues and variations in protein folding that shield more lysine residues from the plasma. Moreover, comparisons of reconstructed ancestral albumin sequences show that the ancestor of birds had 6-8 fewer lysine residues compared to that of mammals.

Variations in native protein glycation and plasma antioxidants in several birds of prey

Birds are an anomaly among vertebrates as they are remarkably long-lived despite having naturally high blood glucose and metabolic rates. For mammals, hyperglycemia leads to oxidative stress and protein glycation. In contrast, many studies have shown that domestic and wild birds are relatively resistant to these glucose-mediated pathologies. Surprisingly very little research has examined protein glycation in birds of prey, which by nature consume a diet high in protein and fat that promotes gluconeogenesis. The purpose of this study was to evaluate protein glycation and antioxidant concentrations in serum samples from several birds of prey (bald eagle (BAEA), red-tailed hawk (RTHA), barred owl (BAOW), great horned owl (GHOW)) as protein glycation can accelerate oxidative stress and vice versa. Serum glucose was measured using a commercially available assay, native albumin glycation was measured by mass spectrometry and various antioxidants (uric acid, vitamin E, retinol and several carotenoids) were measured by high performance liquid chromatography. Although glucose concentrations were not significantly different between species (p=0.340), albumin glycation was significantly higher (p=0.004) in BAEA (23.67±1.90%) and BAOW (24.28±1.43%) compared to RTHA (14.31±0.63%). Of the antioxidants examined, lutein was significantly higher in BAOW (p=0.008). BAEA had the highest beta-cryptoxanthin and beta-carotene concentrations (p<0.005). The high concentrations of antioxidants in these birds of prey relative to other birds likely helps protect from complications that may otherwise arise from having high glucose and protein glycation.