Hirasaka Katsuya, Kohno Shohei, Goto Jumpei, Furochi Harumi, Mawatari Kazuaki, Harada Nagakatsu, Hosaka Toshio, Nakaya Yutaka, Ishidoh Kazumi, Obata Toshiyuki, Ebina Yousuke, Gu Hua, Takeda Shin'ichi, Kishi Kyoichi, Nikawa Takeshi
Department of Nutritional Physiology, Institute of Health Biosciences, The University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima 770-8503, Japan.
Diabetes. 2007 Oct;56(10):2511-22. doi: 10.2337/db06-1768. Epub 2007 Jun 29.
c-Cbl plays an important role in whole-body fuel homeostasis by regulating insulin action. In the present study, we examined the role of Cbl-b, another member of the Cbl family, in insulin action.
C57BL/6 (Cbl-b(+/+)) or Cbl-b-deficient (Cbl-b(-/-)) mice were subjected to insulin and glucose tolerance tests and a hyperinsulinemic-euglycemic clamp test. Infiltration of macrophages into white adipose tissue (WAT) was assessed by immunohistochemistry and flow cytometry. We examined macrophage activation using co-cultures of 3T3-L1 adipocytes and peritoneal macrophages.
Elderly Cbl-b(-/-) mice developed glucose intolerance and peripheral insulin resistance; serum insulin concentrations after a glucose challenge were always higher in elderly Cbl-b(-/-) mice than age-matched Cbl-b(+/+) mice. Deficiency of the Cbl-b gene significantly decreased the uptake of 2-deoxyglucose into WAT and glucose infusion rate, whereas fatty liver was apparent in elderly Cbl-b(-/-) mice. Cbl-b deficiency was associated with infiltration of macrophages into the WAT and expression of cytokines, such as tumor necrosis factor-alpha, interleukin-6, and monocyte chemoattractant protein (MCP)-1. Co-culture of Cbl-b(-/-) macrophages with 3T3-L1 adipocytes induced leptin expression and dephosphorylation of insulin receptor substrate 1, leading to impaired glucose uptake in adipocytes. Furthermore, Vav1, a key factor in macrophage activation, was highly phosphorylated in peritoneal Cbl-b(-/-) macrophages compared with Cbl-b(+/+) macrophages. Treatment with a neutralizing anti-MCP-1 antibody improved peripheral insulin resistance and macrophage infiltration into WAT in elderly Cbl-b(-/-) mice.
Cbl-b is a negative regulator of macrophage infiltration and activation, and macrophage activation by Cbl-b deficiency contributes to the peripheral insulin resistance and glucose intolerance via cytokines secreted from macrophages.
c-Cbl通过调节胰岛素作用在全身能量稳态中发挥重要作用。在本研究中，我们研究了Cbl家族的另一个成员Cbl-b在胰岛素作用中的作用。
对C57BL/6（Cbl-b(+/+)）或Cbl-b基因缺陷（Cbl-b(-/-)）小鼠进行胰岛素和葡萄糖耐量试验以及高胰岛素-正常血糖钳夹试验。通过免疫组织化学和流式细胞术评估巨噬细胞向白色脂肪组织（WAT）的浸润情况。我们使用3T3-L1脂肪细胞和腹腔巨噬细胞的共培养物来检测巨噬细胞的激活情况。
老年Cbl-b(-/-)小鼠出现葡萄糖不耐受和外周胰岛素抵抗；葡萄糖刺激后，老年Cbl-b(-/-)小鼠的血清胰岛素浓度始终高于年龄匹配的Cbl-b(+/+)小鼠。Cbl-b基因缺陷显著降低了WAT对2-脱氧葡萄糖的摄取和葡萄糖输注率，而老年Cbl-b(-/-)小鼠出现明显的脂肪肝。Cbl-b基因缺陷与巨噬细胞浸润到WAT以及细胞因子如肿瘤坏死因子-α、白细胞介素-6和单核细胞趋化蛋白（MCP）-1的表达有关。Cbl-b(-/-)巨噬细胞与3T3-L1脂肪细胞共培养可诱导瘦素表达和胰岛素受体底物1的去磷酸化，导致脂肪细胞葡萄糖摄取受损。此外，与Cbl-b(+/+)巨噬细胞相比，腹腔Cbl-b(-/-)巨噬细胞中巨噬细胞激活的关键因子Vav1高度磷酸化。用中和抗MCP-1抗体治疗可改善老年Cbl-b(-/-)小鼠的外周胰岛素抵抗和巨噬细胞向WAT的浸润。
Cbl-b是巨噬细胞浸润和激活的负调节因子，Cbl-b基因缺陷导致的巨噬细胞激活通过巨噬细胞分泌的细胞因子导致外周胰岛素抵抗和葡萄糖不耐受。
