Maternal dietary methionine restriction alters the expression of energy metabolism genes in the duckling liver

Abstract

Background: In mammals, the nutritional status experienced during embryonic development shapes key metabolic pathways and influences the health and phenotype of the future individual, a phenomenon known as nutritional programming. In farmed birds as well, the quantity and quality of feed offered to the dam can impact the phenotype of the offspring. We have previously reported that a 38% reduction in the intake of the methyl donor methionine in the diet of 30 female ducks during the growing and laying periods - from 10 to 51 weeks of age - reduced the body weight of their 180 mule ducklings compared to that of 190 ducklings from 30 control females. The maternal dietary methionine restriction also altered the hepatic energy metabolism studied in 30 of their ducklings. Thus, their plasma glucose and triglyceride concentrations were higher while their plasma free fatty acid level was lower than those measured in the plasma of 30 ducklings from the control group. The objective of this new study was to better understand how maternal dietary methionine restriction affected the livers of their newly hatched male and female ducklings by investigating the hepatic expression levels of 100 genes primarily targeting energy metabolism, amino acid transport, oxidative stress, apoptotic activity and susceptibility to liver injury.

Results: Sixteen of the genes studied were differentially expressed between the ducklings from the two groups. Maternal dietary methionine restriction affected the mRNA levels of genes involved in different pathways related to energy metabolism such as glycolysis, lipogenesis or electron transport. Moreover, the mRNA levels of the nuclear receptors PPARGC1B, PPARG and RXRA were also affected.

Conclusions: Our results show that the 38% reduction in methionine intake in the diet of female ducks during the growing and egg-laying periods impacted the liver transcriptome of their offspring, which may explain the previously observed differences in their liver energy metabolism. These changes in mRNA levels, together with the observed phenotypic data, suggest an early modulation in the establishment of metabolic pathways.

Keywords: Differentially expressed genes; Duck; Methyl donor; Nutritional programming.

Fig. 1

Exploratory data analyses of the 87 genes. The ducklings from R group and C group are represented with triangles and circles, respectively. The females are in red and the males in blue. A. Hierarchical Cluster Analysis of the gene expressions. In the heatmap, the duckling liver samples and the genes are arranged in rows and columns, respectively. The yellow, orange and red colors correspond to the low, median and high values of the qqnorm transformed normalized relative expressions of the studied genes. The clusters corresponding to duckling liver samples are named 1, 1a, 1b, 2, 2a and 2b. The clusters corresponding to genes are named A, B, B1 and B2. B. Score plot of the PCA along the 2 first principal components. The two first principal components summarized respectively 33% (horizontal axis) and 14% (vertical axis) of the whole variability

Fig. 2

Biplot of principal component analysis. PCA was performed on the data of the 16 DEGs for the diet effect. The male ducklings from the R group (MR) and the C group (MC) are represented in red crosses and grey squares, respectively and the females from the R group (FR) and the C group (FC) are in yellow triangles and blue circles, respectively. The ellipses to gather the groups were added. The two first principal components explain 53.7 and 15.1% of the whole variability, respectively. The correlation circle showed correlations between the DEGs and the two main principal components and displayed an opposite regulation pattern between the 9 down-regulated genes (on the right side of the figure) and the 7 up-regulated ones (on the left side of the figure), when compared the R group to the C group samples

Fig. 3

Correlation matrices of the transcript level of the 16 DEGs between diets and the phenotypic traits of the ducklings. The correlation matrices were plotted for the R group (n = 18), the C group (n = 17), and the males (n = 19) and the female ducklings (n = 16). Phenotypic traits are liver weight, percentages of liver lipids and liver dry mater (DM), plasma activities of ALP, ALT and AST, plasma cholesterol, glucose, triglyceride and free fatty acid (FFA) concentrations. The values used for the 16 DEGs were the imputed normalized expression and the values for the phenotypic data were the raw values. The color scale indicates the strength of the correlation; blue for a positive correlation and red for a negative one. Only the significant correlations (with a P-value < 0.05) were plotted

Fig. 4

Schematic representation of the role of DEGs assigned to energetic metabolism and their regulation in newly hatched ducklings from the R group. The main metabolic pathways impacted by the maternal methionine deficiency are noted (glycolysis, electron transport, de novo lipogenesis, etc.). Up-regulated and down-regulated DEGs in ducklings issued from dams receiving Met-restricted diet are in red and green, respectively. The genes [BMF] and [PPARA] tended to be significant for the diet effect and were added to the Figure but kept in brackets. PPARA promotes fatty acid oxidation whereas PPARG favors de novo lipogenesis (dashes of brown color). PRKAA1 drives fatty acid oxidation (dashes of brown color) and decreases de novo lipogenesis (dashes of grey color). PPARGC1B regulates mitochondrial energy transfers (dashes of brown color)