Blood serum retinol levels in Asinara white donkeys reflect albinism‐induced metabolic adaptation to photoperiod at Mediterranean latitudes. Issue 1 (20th December 2016)

• Record Type: Journal Article
• Authors: Cappai, Maria Grazia; Lunesu, Maria Grazia Antonietta; Accioni, Francesca; Liscia, Massimo; Pusceddu, Mauro; Burrai, Lucia; Nieddu, Maria; Dimauro, Corrado; Boatto, Gianpiero; Pinna, Walter
• Is Part Of: Ecology and evolution. Volume 7:Issue 1(2017:Jan.)
• Page Start: 390
• Page End: 398
• Publication Date: 2016-12-20
• Subjects: melanin -- skin damage -- sun radiation -- vitamin A -- β‐carotene; Ecology -- Periodicals; Evolution -- Periodicals; 577.05
• DOI: 10.1002/ece3.2613
• Languages: English
• ISSNs: 2045-7758

Abstract

Abstract: Previous works on albinism form of Asinara white donkeys ( Equus asinus ) identified the mutation leading to the peculiar phenotype spread to all specimens of the breed. Inbreeding naturally occurred under geographic isolation, on Asinara Island, in the Mediterranean Sea. Albino individuals can be more susceptible to develop health problems when exposed to natural sun radiation. Alternative metabolic pathways involved in photoprotection were explored in this trial. Nutrition‐related metabolites are believed to contribute to the conservation of Asinara donkeys, in which melanin, guaranteeing photoprotection, is lacking. Biochemical profiles with particular focus on blood serum β‐carotene and retinol levels were monitored. Identical natural grazing conditions for both Asinara (albino) and Sardo (pigmented) donkey breeds were assured on same natural pastures throughout the experimental period. A comparative metabolic screening, with emphasis on circulating retinol and nutrient‐related metabolites between the two breeds, was carried out over one year. Potential intra‐ and interspecimen fluctuations of metabolites involved in photoprotection were monitored, both during negative and positive photoperiods. Differences ( p = .064) between blood serum concentrations of retinol from Asinara versus Sardo breed donkeys (0.630 vs . 0.490 μg/ml, respectively) were found. Retinol levels of blood serum turned out to be similar in the two groups (0.523 vs . 0.493 μg/ml, respectively, p = .051) during the negative photoperiod, but markedly differed during the positive one (0.738 vs. 0.486, respectively, p = .016). Blood serum β‐carotene levels displayed to be constantly around the limit of sensitivity in all animals of both breeds. Variations in blood serum concentrations of retinol in Asinara white donkeys can reflect the need to cope with seasonal exposure to daylight at Mediterranean latitudes, as an alternative to the lack of melanin. These results may suggest that a pulsed mobilization of retinol from body stores occurs to increase circulating levels during positive photoperiod. Abstract : Beta‐carotene is converted into retinol or Vitamin A in the brush border of enterocytes. The cleavage of beta‐carotene molecules into retinol undergoes endogenous‐regulated mechanisms, based on the maintenance of constant circulating retinol levels, to prevent excessive storage in tissues. In albino donkeys of Asinara breed, levels of circulating retinol were seen to increase during positive photoperiod and set back to basal levels during negative photoperiod. This fact can be due to retinol efficiently mobilized from stores, under the need to develop efficacious photoprotection against intense and prolonged sun radiation, in the natural habitat where these animals live, at Mediterranean latitudes. Such metabolic adaptation to the environment may find an explanation in the need to protect unpigmented tissues (retina, skin, and hairs) due to the lack of melanin.