PDF(Pubmed)
Abstract：
OBJECTIVE: Obesity-associated chronic inflammation, aka meta-inflammation, is a key pathogenic driver for obesity-associated comorbidity. Growth hormone secretagogue receptor (GHSR) is known to mediate the effects of nutrient-sensing hormone ghrelin in food intake and fat deposition. We previously reported that global Ghsr ablation protects against diet-induced inflammation and insulin resistance, but the site(s) of action and mechanism are unknown. Macrophages are key drivers of meta-inflammation. To unravel the role of GHSR in macrophages, we generated myeloid-specific Ghsr knockout mice (LysM-Cre;Ghsrf/f).
METHODS: LysM-Cre;Ghsrf/f and control Ghsrf/f mice were subjected to 5 months of high-fat diet (HFD) feeding to induce obesity. In vivo, metabolic profiling of food intake, physical activity, and energy expenditure, as well as glucose and insulin tolerance tests (GTT and ITT) were performed. At termination, peritoneal macrophages (PMs), epididymal white adipose tissue (eWAT), and liver were analyzed by flow cytometry and histology. For ex vivo studies, bone marrow-derived macrophages (BMDMs) were generated from the mice and treated with palmitic acid (PA) or lipopolysaccharide (LPS). For in vitro studies, macrophage RAW264.7 cells with Ghsr overexpression or Insulin receptor substrate 2 (Irs2) knockdown were studied.
RESULTS: We found that Ghsr expression in PMs was increased under HFD feeding. In vivo, HFD-fed LysM-Cre;Ghsrf/f mice exhibited significantly attenuated systemic inflammation and insulin resistance without affecting food intake or body weight. Tissue analysis showed that HFD-fed LysM-Cre;Ghsrf/f mice have significantly decreased monocyte/macrophage infiltration, pro-inflammatory activation, and lipid accumulation, showing elevated lipid-associated macrophages (LAMs) in eWAT and liver. Ex vivo, Ghsr-deficient macrophages protected against PA- or LPS-induced pro-inflammatory polarization, showing reduced glycolysis, increased fatty acid oxidation, and decreased NF-κB nuclear translocation. At molecular level, GHSR metabolically programs macrophage polarization through PKA-CREB-IRS2-AKT2 signaling pathway.
CONCLUSIONS: These novel results demonstrate that macrophage GHSR plays a key role in the pathogenesis of meta-inflammation, and macrophage GHSR promotes macrophage infiltration and induces pro-inflammatory polarization. These exciting findings suggest that GHSR may serve as a novel immunotherapeutic target for the treatment of obesity and its associated comorbidity.
METHODS: LysM-Cre;Ghsrf/f and control Ghsrf/f mice were subjected to 5 months of high-fat diet (HFD) feeding to induce obesity. In vivo, metabolic profiling of food intake, physical activity, and energy expenditure, as well as glucose and insulin tolerance tests (GTT and ITT) were performed. At termination, peritoneal macrophages (PMs), epididymal white adipose tissue (eWAT), and liver were analyzed by flow cytometry and histology. For ex vivo studies, bone marrow-derived macrophages (BMDMs) were generated from the mice and treated with palmitic acid (PA) or lipopolysaccharide (LPS). For in vitro studies, macrophage RAW264.7 cells with Ghsr overexpression or Insulin receptor substrate 2 (Irs2) knockdown were studied.
RESULTS: We found that Ghsr expression in PMs was increased under HFD feeding. In vivo, HFD-fed LysM-Cre;Ghsrf/f mice exhibited significantly attenuated systemic inflammation and insulin resistance without affecting food intake or body weight. Tissue analysis showed that HFD-fed LysM-Cre;Ghsrf/f mice have significantly decreased monocyte/macrophage infiltration, pro-inflammatory activation, and lipid accumulation, showing elevated lipid-associated macrophages (LAMs) in eWAT and liver. Ex vivo, Ghsr-deficient macrophages protected against PA- or LPS-induced pro-inflammatory polarization, showing reduced glycolysis, increased fatty acid oxidation, and decreased NF-κB nuclear translocation. At molecular level, GHSR metabolically programs macrophage polarization through PKA-CREB-IRS2-AKT2 signaling pathway.
CONCLUSIONS: These novel results demonstrate that macrophage GHSR plays a key role in the pathogenesis of meta-inflammation, and macrophage GHSR promotes macrophage infiltration and induces pro-inflammatory polarization. These exciting findings suggest that GHSR may serve as a novel immunotherapeutic target for the treatment of obesity and its associated comorbidity.
摘要：
目的：肥胖相关的慢性炎症，akameta-炎症，是肥胖相关共病的关键致病驱动因素。已知生长激素促分泌素受体（GHSR）介导营养敏感激素ghrelin在食物摄入和脂肪沉积中的作用。我们先前报道了全球GHSR消融可预防饮食引起的炎症和胰岛素抵抗，但作用部位和机制未知。巨噬细胞是元炎症的关键驱动因素。为了揭示GHSR在巨噬细胞中的作用，我们产生了髓系特异性Ghsr敲除小鼠(LysM-Cre;Ghsrf/f)。
方法:LysM-Cre;Ghsrf/f和对照Ghsrf/f小鼠接受5个月的高脂饮食(HFD)喂养以诱导肥胖。在体内,食物摄入量的代谢分析，身体活动,和能量消耗，以及葡萄糖和胰岛素耐量试验(GTT和ITT).在终止时，腹膜巨噬细胞（PM），附睾白色脂肪组织(eWAT),通过流式细胞术和组织学分析肝脏。对于离体研究，从小鼠中产生骨髓来源的巨噬细胞（BMDMs），并用棕榈酸（PA）或脂多糖（LPS）处理。对于体外研究，研究了具有Ghsr过表达或胰岛素受体底物2（Irs2）敲低的巨噬细胞RAW264.7细胞。
结果：我们发现在HFD喂养下，腹膜巨噬细胞中的Ghsr表达增加。在体内,HFD喂养的LysM-Cre;Ghsrf/f小鼠表现出明显减弱的全身性炎症和胰岛素抵抗。组织分析显示，HFD喂养的LysM-Cre;Ghsrf/f小鼠的单核细胞/巨噬细胞浸润明显减少，炎症激活，和脂质积累在eWAT和肝脏。离体,Ghsr缺陷型巨噬细胞可抵抗PA或LPS诱导的促炎极化，显示糖酵解减少和脂肪酸氧化增加。在分子水平上,GHSR通过PKA-CREB-IRS2-AKT2信号通路代谢编程巨噬细胞极化。
结论：这些新的结果表明，巨噬细胞GHSR在meta-炎症的发病机制中起关键作用，和巨噬细胞GHSR促进巨噬细胞浸润并诱导促炎极化。这些令人兴奋的发现表明，GHSR可能作为治疗肥胖及其相关合并症的新型免疫治疗靶标。
方法:LysM-Cre;Ghsrf/f和对照Ghsrf/f小鼠接受5个月的高脂饮食(HFD)喂养以诱导肥胖。在体内,食物摄入量的代谢分析，身体活动,和能量消耗，以及葡萄糖和胰岛素耐量试验(GTT和ITT).在终止时，腹膜巨噬细胞（PM），附睾白色脂肪组织(eWAT),通过流式细胞术和组织学分析肝脏。对于离体研究，从小鼠中产生骨髓来源的巨噬细胞（BMDMs），并用棕榈酸（PA）或脂多糖（LPS）处理。对于体外研究，研究了具有Ghsr过表达或胰岛素受体底物2（Irs2）敲低的巨噬细胞RAW264.7细胞。
结果：我们发现在HFD喂养下，腹膜巨噬细胞中的Ghsr表达增加。在体内,HFD喂养的LysM-Cre;Ghsrf/f小鼠表现出明显减弱的全身性炎症和胰岛素抵抗。组织分析显示，HFD喂养的LysM-Cre;Ghsrf/f小鼠的单核细胞/巨噬细胞浸润明显减少，炎症激活，和脂质积累在eWAT和肝脏。离体,Ghsr缺陷型巨噬细胞可抵抗PA或LPS诱导的促炎极化，显示糖酵解减少和脂肪酸氧化增加。在分子水平上,GHSR通过PKA-CREB-IRS2-AKT2信号通路代谢编程巨噬细胞极化。
结论：这些新的结果表明，巨噬细胞GHSR在meta-炎症的发病机制中起关键作用，和巨噬细胞GHSR促进巨噬细胞浸润并诱导促炎极化。这些令人兴奋的发现表明，GHSR可能作为治疗肥胖及其相关合并症的新型免疫治疗靶标。
