Transcriptional profiling coupled with blood metabolite analyses were used to identify porcine genes and pathways that respond to a fasting treatment or to a D298N missense mutation in the melanocortin-4 receptor (MC4R) gene. Gilts (12 homozygous for D298 and 12 homozygous for N298) were either fed ad libitum or fasted for 3 days. Fasting decreased body weight and backfat and increased serum concentrations of non-esterified fatty acid and urea. In response to fasting, 7,029 genes in fat and 1,831 genes in liver were differentially expressed (DE, q value less than 0.05). MC4R genotype did not affect gene expression, body weight, backfat depth, and any measured serum metabolite concentration. Pathway analyses of fasting-induced DE genes indicated that both liver and fat down-regulated energetically costly processes such as lipid and steroid synthesis and up-regulated efficient energy utilization pathways. Fasting increased expression of genes in involved in glucose sparing pathways in liver and extracellular matrix pathways in adipose tissue. Within the DE genes, transcription factors (TF) that regulate many DE genes were identified, confirming the involvement of TF that are known to regulate fasting response and implicating additional TF that are not known to be involved in energy homeostatic responses. Interestingly, estrogen receptor 1 transcriptionally controls fasting induced genes in fat that are involved in cell matrix morphogenesis. Our findings indicate a transcriptional response to fasting in two key metabolic tissues of pigs that was corroborated by changes in blood metabolites; and involvement of novel putative transcriptional regulators in the immediate adaptive response to fasting.
Microarray gene expression profiles of fasting induced changes in liver and adipose tissues of pigs expressing the melanocortin-4 receptor D298N variant.
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View SamplesResidual feed intake (RFI) is a measure of feed efficiency, where low RFI denotes high feed efficiency. Caloric restriction (CR) is associated with feed efficiency in livestock species and to human health benefits such as longevity and cancer prevention. We have developed pig lines that differ in RFI and are interested to identify the genes and pathways that underlie feed efficiency. Prepubertal Yorkshire gilts with low RFI (n=10) or high RFI (n=10) were fed ad libitum or at 80% of maintenance for eight days. We measured serum metabolites and generated transcriptional profiles of liver and subcutaneous adipose tissue. 6,114 genes in fat and 305 genes in liver were differentially expressed (DE) in response to CR and 311 in fat and 147 in liver were DE due to RFI differences. Pathway analyses of CR-induced DE genes indicated a switch to a conservation mode of energy by down-regulating lipogenesis and steroidogenesis in both liver and fat. Interestingly, CR in pigs altered expression of genes in immune and cell cycle/apoptotic pathways in fat, which may explain part of the CR-driven lifespan enhancement. In-silico analysis of transcription factors revealed ESR1 as a putative regulator of the adaptive response to CR and several targets of ESR1 in our DE fat genes were annotated as cell cycle/apoptosis genes. Lipid metabolic pathway was overrepresented by down-regulated genes due to both CR and low RFI. We propose a common energy conservation mechanism, which may be controlled by PPARA, PPARG, and/or CREB in both CR and feed efficient pigs.
Gene expression profiling of the short-term adaptive response to acute caloric restriction in liver and adipose tissues of pigs differing in feed efficiency.
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