Characterization of Insulin Sensitivity and the Plasma Lipidome in Periparturient Dairy Cows

During the transition from gestation to lactation, dairy cows experience negative energy balance due to an increased demand for energy to support milk production coupled with inadequate energy intake. Energy deficit during the peripartum is associated with the development of insulin resistance which contributes to adipose tissue lipolysis. In turn, elevated free fatty acids (FFA) in circulation increase triacylglycerol (TAG) deposition in liver. This metabolic impairment is known to cause postpartum metabolic diseases including fatty liver and ketosis. Consequently, postpartum metabolic disease can lead to reduced milk production in early lactation, impaired reproductive performance, and increased culling rates. Moreover, cows with enhanced prepartum adiposity are at greater risk for postpartum metabolic disease, relative to lean animals. Therefore, our first objective was to evaluate the effect of adiposity on insulin and glucose tolerance in lean and overweight dairy cows during the transition from gestation to lactation. We also wanted to compare these direct measurements with several indirect measurements, including the commonly utilized revised quantitative insulin sensitivity check index (RQUICKI). For our second objective we wanted to identify novel biomarkers for the progression of postpartum metabolic disease in periparturient dairy cows. To achieve this objective, we utilized a contemporary mass spectrometry-based lipidomics approach and a bioinformatics workflow. We demonstrate (1) that excess prepartum adiposity does not influence postpartum systemic insulin sensitivity, (2) surrogate indices for insulin sensitivity do not correlate with direction measurements, and (3) biomarkers for metabolic disease include several phosphatidylcholines