Modulatory Effects of Breed, Feeding Status, and Diet on Adipogenic, Lipogenic, and Lipolytic Gene Expression in Growing Iberian and Duroc Pigs

Meat quality depends on tissue composition which is in turn influenced by different factors, such as diet, genotype, age, or sex. We evaluated the effects of breed, 24 h fasting, and dietary energy source (HO: oleic acid versus CH: carbohydrates) on the expression of candidate genes involved in adipogenesis, lipogenesis, and lipolysis in the adipose tissue from Iberian and Duroc growing pigs. The Iberian pigs showed greater feed intake, backfat thickness, and saturated fatty acids (SFA) content in the subcutaneous fat, whereas the Duroc pigs had greater ham weight and polyunsaturated fatty acids (PUFA) content. In both breeds, the diet induced changes in the fatty acid (FA) composition of subcutaneous fat samples. The HO group had higher monounsaturated fatty acids (MUFA) and oleic acid, and lower SFA than the CH group. Regarding gene expression, breed and feeding status (fasting versus postprandial) had significant effects on gene expression, with quantitative interactions between them, while diet showed negligible effects. In general, adipogenic and lipogenic genes were upregulated in the Iberian pigs and in postprandial samples. In contrast, the expression of lipolytic genes showed complex interaction effects. Our results agree with the phenotypic differences between the Iberian and Duroc breeds and with the inhibition of lipogenesis by fasting. Quantitative interactions between breed and feeding status effects were observed, which indicates a different response to fasting of the two breeds, with the obese Iberian breed showing a more stable expression of lipogenic genes. These results highlight the complexity of lipid metabolism regulation, especially in relation to lipolysis processes.