Innate immune responses to obesity in cloned and wild-type domestic pig

Pigs are widely used as biomedical models for obesity and obesity-induced inflammation underlying the metabolic syndrome in humans because of similar physiology and metabolic features. It was the objective of this study to evaluate if pigs cloned by somatic cell nuclear transfer (n=17) could serve as a refined pig model for obesity-induced innate host responses by reducing pig-to-pig biological variation compared to wild-type (WT) pigs (n=19). Pigs were fed ad libitum with a high fat/high sucrose diet to induce obesity or kept lean on a restricted diet (60% of ad libitum intake) beginning at three months of age. mRNA expression levels were determined for 39 innate immune factors on a high-throughput qPCR system in samples from liver, abdominal fat, mesenteric fat and subcutaneous fat. Previous findings have suggested that cloning may affect certain phenotypic traits of pigs including basic concentrations and responsiveness of components of the innate immune system. Terminal body weights at 7½ - 9½ months of age were significantly higher for both (WT and cloned) obese groups compared to the lean groups. However, obese WT pigs weighed significantly more than obese cloned pigs (P<0.01). In particular, mRNA expression profiles of certain acute phase proteins were significantly affected by cloning, being expressed at higher levels in the liver of both cloned groups compared to both WT groups but at lower levels in adipose tissues of cloned lean pigs as opposed to WT lean pigs. Also there were significant differences between WT and cloned pigs in the gene response to obesity. Thus, significant phenotypic differences were established for central innate immune factors between cloned and WT pigs, including differences in the response of these factors to an obesity-promoting diet. This should be taken into consideration when using cloned animals as models for innate responses to obesity.