A four-week white bread diet does not alter plasma glucose concentrations, metabolic or vascular physiology in mourning doves, Zenaida macroura

Abstract

Birds are an enigma: their plasma glucose concentration is 1.5–2 times higher than similar-sized mammals, yet they do not normally exhibit symptoms of diabetes. We hypothesized that feeding adult mourning doves a refined carbohydrate diet (white bread: WB) for four weeks would raise plasma glucose concentrations and alter metabolic pathways and endothelial function when compared to birds receiving a nutritionally-balanced diet (bird seeds: SD). Following the four-week long diets, birds were euthanized, and cardiac blood, liver, and pectoralis muscles were collected for metabolomics analyses and biochemical assays. Cranial tibial arteries were dissected to measure acetylcholine-mediated vasodilation. Contrary to the hypothesis, WB-fed birds did not have increased plasma glucose concentrations. Principle component analysis score plots suggest minimal differences between groups. However, we identified 15 changes in individual metabolite concentrations between diet groups that, although not statistically significant, are highly predictive (area under receive operating curve, AUROC>0.90; number of highly predictive metabolites: 5 of 123 in plasma, 4 of 92 in liver, and 6 of 92 in pectoralis muscle). Moreover, pathway analyses revealed no significantly altered metabolic pathways between groups. Biochemical assays revealed no significant group differences in plasma uric acid and insulin, or pectoralis muscle glycogen concentrations. However, hepatic glycogen concentration was 2.12-fold higher in the WB group than in control doves (p = .015). Diet type did not influence vasodilation. In conclusion, a four-week long white bread diet increased liver glycogen but did not alter plasma glucose concentrations, metabolic or vascular physiology in mourning doves.