Key Laboratory of Aquaculture Nutrition and Feed (Ministry of Agriculture and Rural Affairs) and Key Laboratory of Mariculture (Ministry of Education), Ocean University of China, Qingdao, Shandong, China.
Key Laboratory of Aquaculture Nutrition and Feed (Ministry of Agriculture and Rural Affairs) and Key Laboratory of Mariculture (Ministry of Education), Ocean University of China, Qingdao, Shandong, China.
J Nutr. 2024 May;154(5):1505-1516. doi: 10.1016/j.tjnut.2024.02.031. Epub 2024 Mar 7.
Sterol regulatory element binding protein (SREBP) 1 is considered to be a crucial regulator for lipid synthesis in vertebrates. However, whether SREBP1 could regulate hepatic gluconeogenesis under high-fat diet (HFD) condition is still unknown, and the underlying mechanism is also unclear.
This study aimed to determine gluconeogenesis-related gene and protein expressions in response to HFD in large yellow croaker and explore the role and mechanism of SREBP1 in regulating the related transcription and signaling.
Croakers (mean weight, 15.61 ± 0.10 g) were fed with diets containing 12% crude lipid [control diet (ND)] or 18% crude lipid (HFD) for 10 weeks. The glucose tolerance, insulin tolerance, hepatic gluconeogenesis-related genes, and proteins expressions were determined. To explore the role of SREBP1 in HFD-induced gluconeogenesis, SREBP1 was inhibited by pharmacologic inhibitor (fatostatin) or genetic knockdown in croaker hepatocytes under palmitic acid (PA) condition. To explore the underlying mechanism, luciferase reporter and chromatin immunoprecipitation assays were conducted in HEK293T cells. Data were analyzed using analysis of variance or Student t test.
Compared with ND, HFD increased the mRNA expressions of gluconeogenesis genes (2.40-fold to 2.60-fold) (P < 0.05) and reduced protein kinase B (AKT) phosphorylation levels (0.28-fold to 0.34-fold) (P < 0.05) in croakers. However, inhibition of SREBP1 by fatostatin addition or SREBP1 knockdown reduced the mRNA expressions of gluconeogenesis genes (P < 0.05) and increased AKT phosphorylation levels (P < 0.05) in hepatocytes, compared with that by PA treatment. Moreover, fatostatin addition or SREBP1 knockdown also increased the mRNA expressions of irs1 (P < 0.05) and reduced serine phosphorylation of IRS1 (P < 0.05). Furthermore, SREBP1 inhibited IRS1 transcriptions by binding to its promoter and induced IRS1 serine phosphorylation by activating diacylglycerol-protein kinase Cε signaling.
This study reveals the role of SREBP1 in hepatic gluconeogenesis under HFD condition in croakers, which may provide a potential strategy for improving HFD-induced glucose intolerance.
固醇调节元件结合蛋白 1（SREBP1）被认为是脊椎动物脂质合成的关键调节因子。然而，SREBP1 是否可以在高脂肪饮食（HFD）条件下调节肝糖异生尚不清楚，其潜在机制也不清楚。
本研究旨在确定大黄鱼对 HFD 的反应中与肝糖异生相关的基因和蛋白表达，并探讨 SREBP1 在调节相关转录和信号中的作用和机制。
用含 12%粗脂肪的饲料（对照饮食，ND）或 18%粗脂肪的饲料（HFD）喂养平均体重为 15.61±0.10 g 的大黄鱼 10 周。测定葡萄糖耐量、胰岛素耐量、肝糖异生相关基因和蛋白的表达。为了探讨 SREBP1 在 HFD 诱导的糖异生中的作用，在棕榈酸（PA）条件下，用药理抑制剂（脂肪抑素）或基因敲低抑制大黄鱼肝细胞中的 SREBP1。为了探讨其潜在机制，在 HEK293T 细胞中进行了荧光素酶报告和染色质免疫沉淀测定。采用方差分析或学生 t 检验进行数据分析。
与 ND 相比，HFD 增加了大黄鱼的糖异生基因的 mRNA 表达（2.40 倍至 2.60 倍）（P<0.05），降低了蛋白激酶 B（AKT）磷酸化水平（0.28 倍至 0.34 倍）（P<0.05）。然而，与 PA 处理相比，脂肪抑素的添加或 SREBP1 敲低抑制了肝细胞中糖异生基因的 mRNA 表达（P<0.05），并增加了 AKT 磷酸化水平（P<0.05）。此外，脂肪抑素的添加或 SREBP1 敲低也增加了 IRS1 的 mRNA 表达（P<0.05），并降低了 IRS1 的丝氨酸磷酸化（P<0.05）。此外，SREBP1 通过结合其启动子抑制 IRS1 的转录，并通过激活二酰基甘油-蛋白激酶 Cε 信号诱导 IRS1 的丝氨酸磷酸化。
本研究揭示了 SREBP1 在大黄鱼 HFD 条件下肝糖异生中的作用，这可能为改善 HFD 诱导的葡萄糖不耐受提供一种潜在策略。
