Gene expression profiles of fasting induced changes in liver and fat tissues of pigs expressing the MC4R D298N variant

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.

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Lkhagvadorj S, Qu L, Cai W, Couture OP, Barb CR, Hausman GJ, Nettleton D, Anderson LL, Dekkers JC, Tuggle CK