Abstract

A decrease in insulin sensitivity enhances adipose tissue lipolysis helping early lactation cows counteracting their energy deficit. However, excessive lipolysis poses serious health risks for cows, and its underlying mechanisms are not clearly understood. The present study used targeted ESI-LC-MS/MS-based metabolomics and indirect insulin sensitivity measurements to evaluate metabolic alterations in the serum of dairy cows of various parities experiencing variable lipolysis early postpartum. Thirty (12 primiparous and 18 multiparous) cows of Holstein Friesian and Simmental breeds, fed the same diet and kept under the same management conditions, were sampled at d 21 postpartum and classified as low (n = 10), medium (n = 8), and high (n = 12) lipolysis groups, based on serum concentration of nonesterified fatty acids. Overall, excessive lipolysis in the high group came along with impaired estimated insulin sensitivity and characteristic shifts in acylcarnitine, sphingomyelin, phosphatidylcholine and lysophospholipid metabolome profiles compared to the low group. From the detected phosphatidylcholines mainly those with diacyl-residues showed differences among lipolysis groups. Furthermore, more than half of the detected sphingomyelins were increased in cows experiencing high lipomobilization. Additionally, strong differences in serum acylcarnitines were noticed among lipolysis groups. The study suggests an altered serum phospholipidome in dairy cows associated with an increase in certain long-chain sphingomyelins and the progression of disturbed insulin function. In conclusion, the present study revealed 37 key metabolites as part of alterations in the synthesis or breakdown of sphingolipids and phospholipids associated with lowered estimated insulin sensitivity and excessive lipolysis in early-lactating cows.

Highlights

  • Early-lactating dairy cows are not able to meet their energy needs through alimentary sources

  • The greatest effect of lipid mobilization was detected for serum profiles of acylcarnitines, sphingomyelins, and phosphatidylcholines with diacyl-residues

  • High lipomobilization was associated with an increase in serum long-chain lysophosphatidylcholine C16:0 compared to the low group (P = 0.02), whereas lysophosphatidylchloine C17:0 was decreased in cows of medium and high mobilization compared to low lipomobilization (P < 0.01)

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Summary

Introduction

Early-lactating dairy cows are not able to meet their energy needs through alimentary sources. Early lactating cows mobilize triacylglycerols (TAG) from adipose tissues to generate the necessary fuels; using nonesterified fatty acids (NEFA) as an energy source [1]. Lipolysis of adipose tissues is part of the metabolic adaptation of cows to counteract the acute energy deficit, which is orchestrated by endocrine changes including a lowered insulin sensitivity in peripheral tissues, i.e. the adipose tissues and skeletal muscles [2]. The exact underlying mechanisms are not fully understood yet, it is believed that the modified peripheral insulin sensitivity accelerates adipose tissue mobilization [3], leading to excessive lipolysis in many early-lactation cows [4,5,6,7]. Postpartum NEFA has been shown to be the best predictor, i.e. compared to beta-hydroxybutyrate, of many metabolic diseases associated with excessive lipolysis in cows, including displaced abomasum, ketosis, and metritis [9]

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