支链氨基酸补充剂通过 INFGR1/JAK1/STAT1 信号通路诱导胰岛素抵抗和促炎型巨噬细胞极化。

BACKGROUND: Obesity is a global epidemic, and the low-grade chronic inflammation of adipose tissue in obese individuals can lead to insulin resistance and type 2 diabetes. Adipose tissue macrophages (ATMs) are the main source of pro-inflammatory cytokines in adipose tissue, making them an important target for therapy. While branched-chain amino acids (BCAA) have been strongly linked to obesity and type 2 diabetes in humans, the relationship between BCAA catabolism and adipose tissue inflammation is unclear. This study aims to investigate whether disrupted BCAA catabolism influences the function of adipose tissue macrophages and the secretion of pro-inflammatory cytokines in adipose tissue, and to determine the underlying mechanism. This research will help us better understand the role of BCAA catabolism in adipose tissue inflammation, obesity, and type 2 diabetes. METHODS: In vivo, we examined whether the BCAA catabolism in ATMs was altered in high-fat diet-induced obesity mice, and if BCAA supplementation would influence obesity, glucose tolerance, insulin sensitivity, adipose tissue inflammation and ATMs polarization in mice. In vitro, we isolated ATMs from standard chow and high BCAA-fed group mice, using RNA-sequencing to investigate the potential molecular pathway regulated by BCAA accumulation. Finally, we performed targeted gene silence experiment and used immunoblotting assays to verify our findings. RESULTS: We found that BCAA catabolic enzymes in ATMs were influenced by high-fat diet induced obesity mice, which caused the accumulation of both BCAA and its downstream BCKA. BCAA supplementation will cause obesity and insulin resistance compared to standard chow (STC) group. And high BCAA diet will induce pro-inflammatory cytokines including Interlukin-1beta (IL-1β), Tumor Necrosis Factor alpha (TNF-α) and monocyte chemoattractant protein-1 (MCP-1) secretion in adipose tissue as well as promoting ATMs M1 polarization (pro-inflammatory phenotype). Transcriptomic analysis revealed that a high BCAA diet would activate IFNGR1/JAK1/STAT1 pathway, and IFNGR1 specific silence can abolish the effect of BCAA supplementation-induced inflammation and ATMs M1 polarization. CONCLUSIONS: The obesity mice model reveals the catabolism of BCAA was disrupted which will cause the accumulation of BCAA, and high-level BCAA will promote ATMs M1 polarization and increase the pro-inflammatory cytokines in adipose tissue which will cause the insulin resistance in further. Therefore, reducing the circulating level of BCAA can be a therapeutic strategy in obesity and insulin resistance patients.

背景：肥胖是一种全球性的流行病，肥胖个体脂肪组织的低度慢性炎症可导致胰岛素抵抗和 2 型糖尿病。脂肪组织巨噬细胞（ATMs）是脂肪组织中促炎细胞因子的主要来源，使其成为治疗的重要靶点。尽管支链氨基酸（BCAA）与人类肥胖和 2 型糖尿病密切相关，但 BCAA 分解代谢与脂肪组织炎症之间的关系尚不清楚。本研究旨在探讨 BCAA 分解代谢紊乱是否会影响脂肪组织巨噬细胞的功能和脂肪组织中促炎细胞因子的分泌，并确定其潜在的机制。这项研究将帮助我们更好地理解 BCAA 分解代谢在脂肪组织炎症、肥胖和 2 型糖尿病中的作用。

方法：在体内，我们研究了高脂肪饮食诱导肥胖小鼠的 ATMs 中 BCAA 分解代谢是否发生改变，以及补充 BCAA 是否会影响肥胖、葡萄糖耐量、胰岛素敏感性、脂肪组织炎症和 ATMs 极化。在体外，我们从标准饲料和高 BCAA 喂养组的小鼠中分离出 ATMs，使用 RNA 测序来研究受 BCAA 积累调控的潜在分子途径。最后，我们进行了靶向基因沉默实验，并使用免疫印迹实验来验证我们的发现。

结果：我们发现，高脂肪饮食诱导肥胖小鼠的 ATMs 中的 BCAA 分解代谢酶受到影响，导致 BCAA 及其下游 BCKA 的积累。与标准饲料（STC）组相比，BCAA 补充会导致肥胖和胰岛素抵抗。高 BCAA 饮食会诱导脂肪组织中包括白细胞介素-1β（IL-1β）、肿瘤坏死因子-α（TNF-α）和单核细胞趋化蛋白-1（MCP-1）在内的促炎细胞因子的分泌，并促进 ATMs M1 极化（促炎表型）。转录组分析表明，高 BCAA 饮食会激活 IFNGR1/JAK1/STAT1 通路，IFNGR1 特异性沉默可以消除 BCAA 补充诱导的炎症和 ATMs M1 极化的作用。

结论：肥胖小鼠模型揭示了 BCAA 的分解代谢被破坏，导致 BCAA 的积累，高水平的 BCAA 会促进 ATMs M1 极化并增加脂肪组织中的促炎细胞因子，从而导致胰岛素抵抗。因此，降低循环 BCAA 水平可能是肥胖和胰岛素抵抗患者的一种治疗策略。