Tumor necrosis factor-α promotes lipolysis and reduces insulin sensitivity by activating nuclear factor kappa B and c-Jun N-terminal kinase in primary bovine adipocytes.
Tumor necrosis factor-α promotes lipolysis and reduces insulin sensitivity by activating nuclear factor kappa B and c-Jun N-terminal kinase in primary bovine adipocytes.
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DOI：
10.3168/jds.2022-22009
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发表时间：
2022-08
影响因子：
3.5
通讯作者：
Xiliang Du;Mingchao Liu;Wenjun Tai;Hao Yu;Xue Hao;J. Loor;Q. Jiang;Zhiyuan Fang;Xinxing Gao-Xinx
中科院分区：
文献类型：
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作者：
Xiliang Du;Mingchao Liu;Wenjun Tai;Hao Yu;Xue Hao;J. Loor;Q. Jiang;Zhiyuan Fang;Xinxing Gao-Xinx
持续的脂肪分解和胰岛素抵抗增加了奶牛在过渡期代谢功能障碍的风险。促炎细胞因子是非反刍动物脂肪组织代谢的关键调节因子，但这些分子在反刍动物中的生物学功能还不是很清楚。因此，本研究的目的是探讨肿瘤坏死因子-α(Tumor-NectorFine-α)是否能影响牛脂肪细胞的胰岛素敏感性和脂解作用及其可能的机制。从体重相近(中位数：36.9 kg，范围：35.5~41.2 kg)的5头1日龄荷斯坦雌性犊牛的大网膜和肠系膜脂肪库取脂肪细胞进行分化，用于(1)不同浓度的肿瘤坏死因子-α(0，0.1，1，或10 ng/mL)处理12h，(2)用10μM脂解激动剂异丙肾上腺素(ISO)预处理3h，然后用或不加10 ng/mL肿瘤坏死因子-α处理12h；(3)用c-jun氨基末端激酶抑制剂SP600125(20μM作用2 h)和核因子-kappaB(NF-κB)抑制剂Bay 11-7082(10μM作用1 h)预先处理12 h，再加或不加10 ng/mL肿瘤坏死因子-α12 h，可使上清液中甘油含量增加，甘油三酯含量降低，胰岛素刺激的蛋白激酶B磷酸化，提示脂解作用被激活，胰岛素敏感性受损。肿瘤坏死因子-α降低细胞存活率，上调细胞凋亡标志物Caspase3mRNA的丰度，增加Caspase3的活性。此外，NF-κB和JNKmRNA的磷酸化增加，白介素6(IL-6)、α和细胞因子信号转导抑制物3(SOCS3)的丰度上调，提示肿瘤坏死因子-κ激活了NF-JNKB和JNK2信号通路。此外，与单独使用肿瘤坏死因子-α相比，异硫氰酸乙酯和肿瘤坏死因子-κ激活的NF-αB和JNK信号通路的激活程度更大。联合应用肿瘤坏死因子-α和异丙肾上腺素可加重肿瘤坏死因子-α诱导的细胞凋亡、胰岛素不敏感和脂解。在没有肿瘤坏死因子-α的情况下，抑制NF-κB和JNK不改变上清液中甘油含量、甘油三酯含量或胰岛素刺激的蛋白激酶B的磷酸化。在存在肿瘤坏死因子-α的情况下，抑制NF-κB和JNK可以减轻肿瘤坏死因子-α诱导的细胞凋亡、胰岛素不敏感和脂解。总之，肿瘤坏死因子-α降低了牛脂肪细胞对胰岛素的敏感性，并诱导脂肪细胞发生脂解和凋亡，其部分机制可能是通过激活核因子-κB和JNK来实现的。因此，本研究结果提示，核因子-κB和JNK可能是缓解脂肪细胞脂解失调和胰岛素抵抗的潜在治疗靶点。
Sustained lipolysis and insulin resistance increase the risk of metabolic dysfunction in dairy cows during the transition period. Proinflammatory cytokines are key regulators of adipose tissue metabolism in nonruminants, but biological functions of these molecules in ruminants are not well known. Thus, the objective of this study was to investigate whether tumor necrosis factor-α (TNF-α) could affect insulin sensitivity and lipolysis in bovine adipocytes as well as the underlying mechanisms. Bovine adipocytes (obtained from the omental and mesenteric adipose depots) isolated from 5 Holstein female calves (1 d old) with similar body weight (median: 36.9 kg, range: 35.5-41.2 kg) were differentiated and used for (1) treatment with different concentrations of TNF-α (0, 0.1, 1, or 10 ng/mL) for 12 h; (2) pretreatment with 10 μM lipolytic agonist isoproterenol (ISO) for 3 h, followed by treatment with or without 10 ng/mL TNF-α for 12 h; and (3) pretreatment with the c-Jun N-terminal kinase (JNK) inhibitor SP600125 (20 μM for 2 h) and nuclear factor kappa B (NF-κB) inhibitor BAY 11-7082 (10 μM for 1 h) followed by treatment with or without 10 ng/mL TNF-α for 12 h. The TNF-α increased glycerol content in supernatant, decreased triglyceride content and insulin-stimulated phosphorylation of protein kinase B suggesting activation of lipolysis and impairment of insulin sensitivity. The TNF-α reduced cell viability, upregulated mRNA abundance of Caspase 3 (CASP3), an apoptosis marker, and increased activity of Caspase 3. In addition, increased phosphorylation of NF-κB and JNK, upregulation of mRNA abundance of interleukin-6 (IL-6), TNFA, and suppressor of cytokine signaling 3 (SOCS3) suggested that TNF-α activated NF-κB and JNK signaling pathways. Furthermore, ISO plus TNF-α-activated NF-κB and JNK signaling pathway to a greater extent than TNF-α alone. Combining TNF-α and ISO aggravated TNF-α-induced apoptosis, insulin insensitivity and lipolysis. In the absence of TNF-α, inhibition of NF-κB and JNK did not alter glycerol content in supernatant, triglyceride content or insulin-stimulated phosphorylation of protein kinase B. In the presence of TNF-α, inhibition of NF-κB and JNK alleviated TNF-α-induced apoptosis, insulin insensitivity and lipolysis. Overall, TNF-α impairs insulin sensitivity and induces lipolysis and apoptosis in bovine adipocytes, which may be partly mediated by activation of NF-κB and JNK. Thus, the data suggested that NF-κB and JNK are potential therapeutic targets for alleviating lipolysis dysregulation and insulin resistance in adipocytes.