Prepartum body conditions affect insulin signaling pathways in postpartum adipose tissues in transition dairy cows

Fanjian Zhang,Yinxu Hou,Dan Li,Wenyi Guan,Jian Sun,Qiong Wu,Yaohong Zhu,Jiufeng Wang

doi:10.1186/s40104-019-0347-4

Abstract

BackgroundOverconditioned dairy cows are susceptible to excessive lipolysis and increased insulin resistance during the transition period. The associations among body fat reserve, insulin resistance, and lipolysis in adipose tissues (AT) remain to be elucidated. Therefore, this study aimed to investigate whether excessive fat reserves influence the insulin signaling pathway in AT postpartum.ResultsTwenty multiparous dairy cows were selected and assigned to one of two groups, according to prepartum body condition score (BCS): Control group (BCS = 3.0–3.5; n = 10) and Overconditioned group (BCS ≥ 4.0; n = 10). Blood samples were collected on days −14, −7, −4, −2, −1, 0, 1, 2, 4, 7, and 14 relative to parturition. Subcutaneous AT were collected on day 2 following parturition for quantitative real-time polymerase chain reaction and western blot analyses. No differences were observed between the two groups in serum glucose, non-esterified fatty acids, β-hydroxybutyric acid, tumor necrosis factor (TNF) α, insulin, or leptin concentrations during the experimental period. Compared with the control cows, the overconditioned cows had lower serum triglyceride levels and higher adiponectin concentrations. In the AT postpartum, insulin receptor mRNA and protein levels were lower in the overconditioned cows than in the control cows, and no differences were found in glucose transporter 4 mRNA. Compared with the control cows, the overconditioned cows had lower mRNA levels of TNFα and higher mRNA levels of peroxisome proliferator-activated receptor gamma (PPARγ) in AT postpartum. The phosphorylated protein kinase B (AKT) content and phosphorylation rate of AKT were increased in the overconditioned cows compared with the control cows, which suggested that the downstream insulin signaling in AT was affected.ConclusionsIn the present study, transition dairy cows with higher BCS did not show more fat mobilization. The changes of insulin signaling pathway in AT postpartum of overconditioned cows may be partly related to the expression of PPARγ and TNFα, and the secretion of adiponectin.

Highlights

Overconditioned dairy cows are susceptible to excessive lipolysis and increased insulin resistance during the transition period
Previous studies have suggested that overfed cows or cows with a higher body condition score (BCS) are more insulin resistant [18, 19], it was reported recently that body condition did not affect adipose tissues (AT) Insulin resistance (IR) postpartum [11]
Triglycerides, non-esterified fatty acid (NEFA), beta hydroxybutyric acid (BHBA), and TNFα The BCS had no significant effect on serum glucose concentration (Fig. 1a)

Summary

Introduction

Overconditioned dairy cows are susceptible to excessive lipolysis and increased insulin resistance during the transition period. The associations among body fat reserve, insulin resistance, and lipolysis in adipose tissues (AT) remain to be elucidated. This study aimed to investigate whether excessive fat reserves influence the insulin signaling pathway in AT postpartum. The regulation of insulin signaling pathway by blood metabolites during lipolysis may be responsible for the development of IR in AT [10, 11]. Previous studies have suggested that overfed cows or cows with a higher BCS are more insulin resistant [18, 19], it was reported recently that body condition did not affect AT IR postpartum [11]. The metabolic changes of transition dairy cows with different BCS may be related to IR development

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