Methods to study protein turnover in adult and aging dogs

Abstract

Sarcopenia affects part of the elderly dog population, being characterized by the loss of lean body mass, probably resulting from decreased muscle protein synthesis. In order to further investigate protein metabolism in dogs of different ages, we propose the comparison of three methods to determine protein flux in adult and elderly dogs. The study will be carried out in a completely randomized design, in a 3x2 factorial arrangement of treatments, with three methods and two age groups. For the study of protein metabolism, the precursor method with L- [1-13C] Leucine, the [15N] Glycine end products method and the indirect oxidation method L- [1-13C] Phenylalanine will be compared. The study will include 20 dogs, male or female, 10 adults (age between 1 and 3 years) and 10 elderly (age greater than 10 years). The animals will be fed commercial feed extruded for elderly dogs in sufficient quantity to maintain body weight. Dogs will receive food for 33 days, distributed as follows: day 1 to 10 for diet adaptation, days 11 to 15 for total collection of faeces urine for the test of digestibility, nitrogen balance and elimination of urine of 24 hours by urine, days 16 to 19 for rest, days 20 to 23 for the test of phenylalanine (expired gas and urine), days 24 and 25 for the glycine (urine) test, days 26 to 32 for rest and elimination of the previous markers, day 33 for the Leucine test (expired gas and plasma). Through the collection of plasma, urine and expired gas, the parameters of isotopic enrichment will be obtained and applied in flux equations, protein synthesis and degradation. Before the comparisons of means will be verified the assumptions of homogeneity of variances and normality of the errors. The data will be submitted to analysis of variance, considering the effects of method, age and their interactions (method x age). When significance is obtained in Test F, the means will be compared by the Tukey test. The methods of evaluation of protein turnover will also be compared by Pearson correlation and Bland and Altman analysis. The value of P <0.05 will be considered significant. With the results, we hope to obtain a more in-depth view on the effect of age on the protein metabolism of dogs, as well as to study in further the three methods of determination of body protein turnover. (AU)