Expression of genes related to liver fatty acid metabolism in fat-tailed and thin-tailed lambs during negative and positive energy balances.

Fat-tailed sheep breeds can tolerate periods of negative energy balance without suffering from elevated concentration of plasma non-esterified fatty acid (NEFA). This ability was attributed to unique metabolism of fat-tailed adipose depot, whereas role of liver as an influential organ in fatty acid metabolism was not evaluated yet. Hence, current study was conducted to evaluate the effects of negative and positive energy balances on liver expression of genes related to fatty acid metabolism in fat-tailed and thin-tailed lambs. Lambs experienced negative (21 days) and positive (21 days) energy balances and were slaughtered at the beginning and end of negative energy balance and at the end of positive energy balance. Real-time quantitative polymerase chain reaction (RT-Q-PCR) was conducted to evaluate changes in gene expression. Expression of diglyceride acyltransferase 1 (DGAT1), 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2) and apolipoprotein B (APOB) was not affected by genotype, energy balance and their interaction. Expression of carnitine palmitoyltransferase 1 (CPT1) was significantly higher in liver of fat-tailed comparing to thin-tailed lambs regardless of energy balance (p < 0.02). Catalase mRNA abundance was increased in response to negative energy balance (p < 0.02), and severity of this enhancement was higher in fat-tailed lambs (p < 0.06). Expression of CPT1 was positively correlated with expression of HMGCS2 in both fat-tailed (p < 0.05) and thin-tailed lambs (p < 0.002); however, the correlation was weaker in fat-tailed lambs (0.72 vs. 0.57, respectively, for thin-tailed and fat-tailed lambs). There was a positive correlation between DGAT1 and APOB genes expression in fat-tailed lambs (0.94; p < 0.001), whereas this correlation was not observed in thin-tailed lambs. Results demonstrate that liver of fat-tailed lambs has higher capacity for metabolism of mobilized NEFA exposed to liver during negative energy balance.