Abstract
Objectives and studyThis study aimed at measuring the effect in normal to restricted protein diets with specific 15N natural isotopic abundance (NIA) given during gestation and/or lactation on the 15N NIA of fur, liver and muscle in dams and their offspring from birth to adulthood. The secondary aim was to study the effect of growth on the same parameters.MethodsFemale Balb/c mice were fed normal protein diet containing 22% protein or isocaloric low protein diet containing 10% protein throughout gestation. Dam’s diets were either maintained or switched to the other diet until weaning at 30 days. All animals were fed standard chow thereafter. Offspring were sacrificed at 1, 11, 30, 60, 480 days and a group of dams at d1. Growth was modeled as an exponential function on the group followed up until 480 days. Fur, liver and muscle were sampled at sacrifice and analyzed for bulk 15N NIA. Fixed effects and interactions between fixed effects and random elements were tested by three-way ANOVA.ResultsHigher 15N NIA in the diet resulted in higher organ 15N NIA. Switching from one diet to another changed 15N NIA in each organ. Although dam and offspring shared the same isotopic environment during gestation, 15N NIA at day 1 was higher in dams. Growth rate did not differ between groups after 10 days and decreased between 1 and 5 months. 15N NIA differed between organs and was affected by growth and gestation/lactation.ConclusionDietary 15N NIA is a major determinant of the 15N NIA of organs. 15N NIA depended on organ and age (i.e. growth) suggesting an effect of metabolism and/or dilution space. Post-natal normal-protein diet of lactating dams could reverse the effect of a protein-restricted diet during gestation on the offspring growth. Measuring 15N NIA in various matrices may open a field of application particularly useful in studying the pre- and post-natal origins of health and disease.
Highlights
15N is a stable isotope of nitrogen present in nature, accounting for 0.4% of N in whole body pools [1]. 15N natural isotopic abundance (NIA) in body proteins is determined by the 15N values of nutrient and by N metabolism [2].NIA values (δ15N) have been shown to be a valuable index of nutrient intake and metabolism in animals [3,4]
Dietary 15N NIA is a major determinant of the 15N NIA of organs. 15N NIA depended on organ and age suggesting an effect of metabolism and/or dilution space
They modeled body compartments involved in protein metabolism and observed that 15N NIA depended on protein turnover. 15N NIAs in tissues differed according to the protein turnover of each organ, e.g. the liver had a higher 15N NIA than the muscle [5]
Summary
15N is a stable isotope of nitrogen present in nature, accounting for 0.4% of N in whole body pools [1]. 15N natural isotopic abundance (NIA) in body proteins is determined by the 15N values of nutrient and by N metabolism [2].NIA values (δ15N) have been shown to be a valuable index of nutrient intake and metabolism in animals [3,4]. 15N natural isotopic abundance (NIA) in body proteins is determined by the 15N values of nutrient and by N metabolism [2]. Poupin et al provide robust arguments for the variation in 15N NIA according to protein metabolism in rats [4,7]. They modeled body compartments involved in protein metabolism and observed that 15N NIA depended on protein turnover. The intensity of the isotopic shift seems to depend on the liver metabolic pathways and their activity, i.e. protein turnover, whether modulated by dietary intake or pathological state [6,8]. Even if the stable state is different from the previous one, the fractionation could return to the previous level, making this marker dynamic [9]
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