NONRUMINANT NUTRITION SYMPOSIUM I
By: Ronald Trotta
The nonruminant nutrition symposium began with opening remarks and introductions from Dr. Shengfa Liao. The first speaker was Dr. Artmenis Simopoulus, the founder and president of The Center for Genetics, Nutrition, and Health in Washington DC. Relationships between genes, environment, and development are dynamic and understanding genetic variation is essential to understanding interactions with diet and the environment. Historically, improvements in agricultural and food production have led to increases in the dietary intake of omega-6 fatty acids and decreases in the dietary intake of omega-3 fatty acids, leading to an imbalance of the omega-6:omega-3 in humans. For example, omega-6 and omega-3 fatty acids are metabolized similarly yet, there are variations in the desaturase and elonagase enzymes. Dr. Simopoulus explained that increases in the omega-6:omega-3 were associated with greater desaturase activity and greater incidences of coronary heart disease. Nutrigenetics is the study of how genetic variants influences dietary response. Nutrigenomics is the study of nutrients influencing gene expression. A combination of nutrigenetics and nutrigenomics is necessary to determine the healthiest food option of an individual or a population of individuals. Dr. Simopoulus concluded that identification of relationships between genes, transcripts, proteins, and metabolites are essential components to integrative metabolism. The effects of diet on whole-body metabolism and the influence of genotype on nutritionally related disease must be considered for the target goal of personalized nutrition to be realized.
Dr. Shengfa Liao, an Associate Professor from Mississippi State University, was the second speaker in the symposium. He explained that improvements in animal genetics and nutrition are necessary for improving animal feed efficiency to increase animal production for the growing human population. Nutrients from the diet can regulate changes in DNA replication and transcription, RNA translation, and protein synthesis and post-translational modifications. Transcriptomics is the pool of RNAs that shift in response to dietary nutrient supply. The RNA-sequencing technique can be used to study the effects of nutrition on transcriptomics. This process has three principal steps: laboratory analysis, bioinformatics analysis, and biological interpretation. This technique can be applied to issues in animal nutrition to obtain total/differential gene expression analyses that can identify affected pathways, novel transcripts, and potential biomarkers for associated phenotypes of interest. In a recent study, pigs fed a lysine-deficient diet for 8 weeks had a decrease in final body weight, average daily gain, and feed efficiency. Transcriptomics analysis revealed that dietary lysine restriction changed the gene expression profile in the longissimus dorsi muscle of growing pigs. Dr. Liao explained that dietary lysine restriction may inhibit or activate some upstream regulators which are critically for protein and lipid metabolism. He speculated that the FXR/RXR and LXR/RXR signaling pathways may be activated by dietary lysine restriction, which may be responsible for altering the lipid profile in pig skeletal muscle. Future research is needed to understand how dietary lysine restriction may compromise pig growth and performance through transcriptomic regulators and associated biological processes.
The third speaker of the symposium was Dr. Maria Oczkowicz from the National Research Insitute of Animal Production in Krakow, Poland. Dietary fatty acids are important signaling molecules that may be important in modulating health and disease. In the 3’-quant mRNA-sequencing method, the quantification of gene expression is based only on the 3’ UTR fragment of genes. Dr. Oczkowicz explained that this approach contrasts traditional RNA sequencing in which the analysis is based on the entire lengths of the transcripts, which is also cheaper and claimed to be more sensitive. Liver transcriptomic profiles from pigs fed different fat supplement sources were evaluated. Pigs in this study were supplemented with rapeseed oil, beef tallow, or coconut oil. The amount of differentially expressed genes in the liver were greatest between rapeseed oil and beef tallow groups. Altered expression of genes between dietary fat sources were important to pathways involving signaling, autophagy, cholesterol metabolism, oxidative stress, and RNA and protein processing. Dr. Oczkowicz went on to explain that differentially expressed genes in the beef tallow group were related to neurodegenerative, cardiovascular, endocrine, metabolic, and infectious diseases and cancer. Data analyzed in this study with the 3’-quant mRNA-sequencing method support other observations that this method may be more sensitive than traditional methods. Addition of different sources of fat strongly changed transcriptomic profiles of the liver of pigs. Liver transcriptomic profiles from pigs supplemented with coconut oil were more similar to beef tallow than rapeseed oil. Dr. Oczkowicz concluded that the results support the ideas of common pathogenesis of civilization disease and the important role of diet. She speculated that coconut oil is less pro-inflammatory than beef tallow based on dysregulation of certain metabolic pathways in the liver.
The final speaker of the symposium was Dr. Nares Trakooljul, a post-doctoral researcher from the Leibniz Institute for Farm Animal Biology in Dummerstorf, Germany. Dr. Trakooljul began his talk by explaining how maternal diet can influence fetal growth and development by epigenetic mechanisms, including DNA methylation and histone modifications. Epigenetic reprogramming occurs during the peri-implantation and germ cell development stages. Intrauterine and post-natal environments influence epigenome reprogramming which can influence the phenotype of an animal. Dietary supplementation of one-carbon metabolites such as methionine could potentially influence fetal programming via epigenetic modification. Pregnant sows were fed a standard diet or a standard diet supplemented with methionine. Methionine supplementation increased fetal weight at day 91 post-conception. Insulin growth factor signaling pathway was affected by methionine supplementation, based on microarray analysis of fetal muscle. In a second experiment, Dr. Trakooljul found that oncogenetic stage, sex, breed, and maternal diet influenced differential gene expression based on RNA sequencing and bisulfate-sequencing analyses. Pathway analyses revealed that genes involved in nucleic acid and lipid metabolism were altered by methionine supplementation. Dr. Trakooljul concluded that methionine supplementation had an immediate effect on nucleic acid metabolism pathways in the fetal liver and suggested that changes in lipid metabolism modulated by methionine may be accompanied by reduced backfat thickness in adult offspring.