A team of Dutch researchers, led by Marinus F.W. te Pas,1 tested whether pigs can serve as a model for early stage metabolic syndrome biomarkers. Pigs share many metabolic similarities with humans and offer several advantages for studies focusing on dietary effects. Not only can metabolic syndrome be experimentally induced in pigs and a more complete range of biological samples be obtained, but also laboratory animals are more similar to each other and can be kept under strictly controlled environmental and dietary conditions.

This study compared the effects of two different diets on two different types of pigs: normal pigs and pigs with induced diabetes. The two diets had the same total gross energy, but differed in the proportions of unsaturated vs. saturated fat. The investigators fed half the pigs a “Mediterranean diet” high in unsaturated fat, containing canola, corn and fish oils. The other half received a “cafeteria diet” high in saturated fats like lard.

Researchers fed the pigs their respective diets for 10 weeks. They measured various physiological parameters including weight gain, body composition, fatness, metabolism and diabetic status. They then sampled plasma from each of the four groups.

The investigators found differences in glucose, insulin, cholesterol and blood lipids between the pigs that ate the Mediterranean diet versus the cafeteria diet. Both groups showed similarities in their responses to the Mediterranean diet. However, the diabetic pigs responded quite differently than the normal pigs did to the cafeteria diet.

The researchers suggested that diabetic pigs are extremely sensitive to differences in feed compositions and responded poorly to the unhealthy cafeteria diet. To detect proteomic changes, researchers fractionated the plasma samples with protein arrays, eluted them and then analyzed them using mass spectrometry.

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The researchers observed 984 protein peaks and determined their differential expression in the different pig groups. Correlation with physiological parameters showed that the cafeteria diet significantly affected the cholesterol, low-density lipoprotein and very low-density lipoprotein in diabetic pigs. The saturated fat diet also affected the protein peaks in the control pigs, but to a lesser extent.

While these scientists showed that pigs respond differently to the two diets, this does not mean they are necessarily an appropriate human model. Diet is a strong contributor to metabolic syndrome, but other factors such as genetics, stress, exercise and aging also play important roles. Whereas this and similar studies may help identify diet-related biomarker suspects, only human studies can determine the full spectrum of metabolic influences.

  1. te Pas MF, Koopmans SJ, Kruijt L, et al. Plasma proteome profiles associated with diet-induced metabolic syndrome and the early onset of metabolic syndrome in a pig model. PLoS One. 2013 Sep 23;8(9):e73087. doi: 10.1371/journal.pone.0073087. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3781149/pdf/pone.0073087.pdf