Characterization of Depot Development and the Role of the Novel Adipokine Relaxin in Regulating Lipid Metabolism, Endocrine Function and the Extracellular Matrix in Porcine Adipose Tissue from Lard and Meat-type Pigs

Abstract

The lard-type, Mangalica pig is a genetic model of excessive adiposity and a breed prized for its excellent pork quality. Therefore, this European heritage breed may serve as a model to improve carcass merit in modern commercial lean breeds and as a unique model to study factors regulating adipose tissue development in pigs. Currently this breed is gaining popularity within the United States swine industry. However, at this time, it is not possible to make science-based recommendations on the ideal harvest weight of Mangalica pigs due to poorly characterized growth and carcass parameters across the breeds growth curve. To resolve this issue, a growth trial was conducted to evaluate 1) growth performance, 2) adipose tissue development, 3) carcass parameters and primal cut measurements, and 4) measures of carcass merit. Previous research involving this breed revealed that porcine adipose tissue synthesizes and secretes the hormone relaxin (RLN), cells of adipose tissue express the RLN receptor, and exposing adipose tissue to exogenous RLN significantly alters the adipocyte transcriptome. To extend these observations, adipose tissue from Mangalica pigs was utilized to further study the effect of RLN on adipose tissue biology. This research demonstrates RLN’s ability to 1) decrease preadipocyte number, 2) enhance adipogenesis, 3) alter the mRNA expression of adipokine, fatty acid metabolism and extracellular matrix genes, 4) stimulate lipolysis, and 5) signal through the cAMP pathway. Overall, these data provide novel information on optimal harvest weights of the Mangalica breed and establishes a new function for RLN by supporting the hypothesis that relaxin is a novel regulator of porcine adipose tissue development.