NEFAs Influence the Inflammatory and Insulin Signaling Pathways Through TLR4 in Primary Calf Hepatocytes in vitro.

Qinghua Deng,Guowen Liu,Yuming Zhang,Liyin Du

doi:10.3389/fvets.2021.755505

Qinghua Deng, Guowen Liu + Show 2 more

Open Access

https://doi.org/10.3389/fvets.2021.755505

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Abstract

Transition dairy cows are often in a state of negative energy balance because of decreased dry matter intake and increased energy requirements, initiating lipid mobilization and leading to high serum β-hydroxybutyrate (BHBA) and non-esterified fatty acid (NEFAs) levels, which can induce ketosis and fatty liver in dairy cows. Inflammation and insulin resistance are also common diseases in the perinatal period of dairy cows. What is the relationship between negative energy balance, insulin resistance and inflammation in dairy cows? To study the role of non-esterified fatty acids in the nuclear factor kappa beta (NF-κB) inflammatory and insulin signaling pathways through Toll-like receptor 4 (TLR4), we cultured primary calf hepatocytes and added different concentrations of NEFAs to assess the mRNA and protein levels of inflammatory and insulin signaling pathways. Our experiments indicated that NEFAs could activate the NF-κB inflammatory signaling pathway and influence insulin resistance through TLR4. However, an inhibitor of TLR4 alleviated the inhibitory effects of NEFAs on the insulin pathway. In conclusion, all of these results indicate that high-dose NEFAs (2.4 mM) can activate the TLR4/NF-κB inflammatory signaling pathway and reduce the sensitivity of the insulin pathway through the TLR4/PI3K/AKT metabolic axis.

Highlights

Ketosis and fatty liver, common nutritional, and metabolic diseases in perinatal dairy cows, are characterized by negative energy balance (NEB), often accompanied by insulin resistance and inflammation [1,2,3]
We assumed that non-esterified fatty acids (NEFAs) can bind Toll-like receptor 4 (TLR4) on the cell membrane of hepatocytes and influence the NF-κB and insulin signaling pathways
We found that NEFAs obviously increased the initial calf hepatocyte TLR4 protein expression level, and with increasing concentrations of NEFAs, the P65 phosphorylation level gradually increased (Figure 1)

Summary

Introduction

Common nutritional, and metabolic diseases in perinatal dairy cows, are characterized by negative energy balance (NEB), often accompanied by insulin resistance and inflammation [1,2,3]. Under NEB conditions, dairy cows mobilize their body fat to produce a large amount of non-esterified fatty acids (NEFAs) into the blood. Studies in obese or high-fat diet-fed mice have demonstrated that NEFAs are closely related to inflammation and insulin resistance and act as signaling molecules that can directly regulate lipid metabolism in hepatocytes [5]. Insulin resistance is a serious disease that can lead to complications such as hyperglycemia and hyperlipidemia throughout the body, including the NEFAs Influence Inflammatory and Insulin liver, and other tissues. The mechanisms by which NEFAs induce insulin resistance and inflammatory are not clear

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Conclusion