Association Between Plasma Metabolites and Insulin Sensitivity Indexes in Fat-Tailed and Thin-Tailed Lambs During Negative and Positive Energy Balances

BACKGROUND: Fatty acid mobilization and inflammatory response of adipose tissues vary in various depots, hence the response of fat-tailed and thin-tailed sheep breeds to different energy balances was hypothesized to be different due to differences in proportion of adipose depots. OBJECTIVES: Current study aimed to evaluated the changes in plasma metabolites in response to negative and positive energy balances and their correlation with insulin sensitivity indexes in Lori-Bakhtiari fat-tailed and Lori-Bakhtiari × Romanov cross breed thin-tailed lambs. METHODS: Lambs experienced periods of negative (21 d) and positive (21 d) energy balances. Lambs were bled weekly to measure plasma metabolites. Pearson correlation coefficients among variables were generated using Proc Corr of SAS. Results: In thin-tailed lambs, plasma NEFA showed a negative correlation with plasma glucose (R = -0.47; P 0.0003) and insulin (R = -0.46; P 0.0005) content. Plasma NEFA negatively correlated with revised quantitative insulin sensitivity check index (RQUICKI) and severity of the correlation was higher in fattailed (R = -0.58; P 0.0001) comparing to thin-tailed (R = -0.40; P 0.003) lambs. In fat-tailed lambs, plasma NEFA and insulin were the most influential factors affecting RQUICKI, whereas in thin-tailed lambs, insulin was the main factor affecting RQUICKI. CONCLUSIONS: The results demonstrate that despite higher basal and negative energy balance induced plasma NEFA content in thin-tailed lambs, the contribution of plasma NEFA to insulin resistance was higher in fat-tailed lambs, whereas negative correlation between plasma NEFA and insulin content in thin-tailed lambs demonstrates higher susceptibility of insulin secretion capacity to negative energy balance.