155 Low Insulin Sensitivity Is Associated with Increased Body Fat and Changes in Gene Expression of Lipogenic Enzymes in the Adipose Tissue of Finishing Pigs

Variations in body fat (BF) among pigs can be associated with differences in insulin sensitivity given the insulin anabolic effect in lipid synthesis. The study objectives were to characterize this association and compare the relative mRNA abundance of genes associated with insulin resistance and de novo lipogenesis in the adipose tissue of fat and lean pigs. Thirty 95 kg pigs, catheterized in the jugular vein, received an oral dose of 1.75 g glucose/kg of BW after 18 hours of fasting. Blood samples were collected at -20, -10, 5, 10, 15, 20, 25, 30, 45, 60, 90, 120, 150, 180, 210, 240, 300 and 360 minutes following glucose ingestion. Insulin sensitivity indexes were calculated and analyzed. The BF (%) was estimated by dual X-ray densitometry. The 8 fattest (22 % BF) and the 8 leanest pigs (17.2 % BF) were used to determine the relative mRNA abundance of studied genes using real-time qPCR analyses. Insulin sensitivity was determined using QUICKI and Matsuda indexes, respectively, and their association with body fat was studied with Spearman correlations. Differences in gene expression and insulin sensitivity between fat and lean pigs were studied with a one-way ANOVA. The QUICKI and Matsuda indexes negatively correlated with BF (r = -0.67 and r = -0.59; P < 0.001). Fat pigs had reduced insulin sensitivity and higher relative mRNA abundance of lipogenic enzymes (ACACA, ACLY, FASN; P < 0.05) than lean pigs. The higher expression level of glucose-6-phosphate dehydrogenase (G6PD) combined with the trend (P < 0.10) of lower expression of peroxisome proliferator-activated receptor-gamma (PPAR-γ) in fat pigs may explain part of their reduced insulin sensitivity. These results suggest that an increased BF is associated with reduced insulin sensitivity and greater expression of lipogenic enzymes in pig adipose tissue.