Associations of heart and adipocyte fatty acid-binding protein gene expression with intramuscular fat content in pigs

Intramuscular fat content is a major determinant of meat quality in pigs. Previously, polymorphisms in the adipocyte and heart fatty acid-binding protein genes, A-FABP and H-FABP, have been significantly associated with genetic variation of intramuscular fat content in a Duroc pig population. Further support for the role of H-FABP but not for A-FABP was found in a Meishan crossbred population. However, the effect of closely linked genes could not be excluded in these analyses. To validate the role of A-FABP and H-FABP in intramuscular fat accretion, 153 pigs of a crossbred genotype were evaluated for the A-FABP and H-FABP polymorphisms, mRNA, and protein expression levels of both FABP genes and intramuscular fat content in the longissimus lumborum muscle. For H-FABP, statistical analyses showed significant differences in mRNA but not protein expression levels between H-FABP Hae III PCR-RFLP genotype classes. Between these genotype classes, significant differences in intramuscular fat content were found within barrows but not in gilts. Moreover, H-FABP mRNA but not protein expression levels were significantly related to intramuscular fat content. For A-FABP genotype classes, no significant differences in mRNA and protein expression levels were found. However, a significant difference in intramuscular fat content was found within barrows but not in gilts. In addition, a significant relationship between A-FABP mRNA but not protein expression levels and intramuscular fat content was found. In conclusion, variation of intramuscular fat content could not be explained by differences in A-FABP and H-FABP mRNA and protein expression levels. However this may be due to limitations of the assays used and(or) the inappropriateness of the time of sampling. Finally, results suggest that A-FABP and H-FABP expression are translationally rather than transcriptionally regulated.