Age-related impairment in anti-HMGB1 IgM response potentiates type 2 diabetes

项目摘要 2型糖尿病（T2 D）是老年人的常见疾病，也是其他年龄相关疾病的危险因素。 疾病这些疾病的一个共同联系是与年龄相关的低度慢性炎症（已知的慢性炎症）的增加。 称为“炎症”）。慢性炎症部分由损伤相关分子模式触发 （DAMP）。HMGB 1（高迁移率族蛋白1）是一种典型的DAMP，在进化上是保守的，它 与包括T2 D和心血管疾病在内的几种年龄相关疾病的发病机制有关 （CVD）。最近，在正常小鼠和健康人献血者中，我们发现了一种内源性抗- HMGB 1 IgM抗体（Ab），通过与HMGB 1的高度结合，中和HMGB 1的促炎活性。 HMGB 1的保守表位，即HMW 4。这种抗HMW 4 IgM在小鼠中上调， 高脂饮食（HFD）。重要的是，上调抗HMW 4 IgM的能力（HFD激发后） 在中年（9个月大）雄性和老年（14个月大）雌性小鼠中， 对HFD致糖尿病效应的脆弱性增加（或耐受性降低），如更多 胰岛素抵抗（IR）的快速发作。这些数据迫使我们现在测试我们的假设，即抗HMW 4 IgM 具有糖尿病保护作用，年龄相关的IgM升高障碍是其中一个因素 导致HFD致糖尿病效应的脆弱性增加，从而增加IR/T2 D的风险。 我们提出两个具体目标。具体目标#1是确定抗HMW 4 IgM是否是糖尿病， 保护性的我们将使用两种互补的方法：1）确定是否输注抗HMW 4 IgM 进入年轻、中年和老年小鼠（“功能获得”）赋予针对HFD诱导的IR的保护， 炎症2)确定是否通过消耗产生抗HMW 4 IgM的 年轻小鼠中的B-1细胞（“功能丧失”）损害了它们对HFD的耐受性。具体目标#2是确定年龄- HMW 4反应性B-1细胞的相关缺陷损害抗HMW 4 IgM反应，重点是 TLR 4信号轴。我们将使用两种方法：1）分析腹膜HMW 4反应性 来自年轻、中年和老年小鼠的B-1细胞，以确定中年和老年小鼠是否具有 TLR 4信号传导的缺陷。2)用TLR 4激动剂MPLA处理中年和老年小鼠以确定 增强的TLR 4刺激是否恢复其抗HMW 4 IgM应答和对HFD的耐受性。 本研究的意义在于几个方面。这些研究将确定一个与年龄有关的 调节慢性炎症和身体对脂肪食物的耐受性的机制。他们将提供 对代谢挑战中免疫-代谢相互作用的宝贵见解。预计他们会写出一部小说 免疫治疗的靶点（即，产生抗HMW 4 IgM的B细胞）和“可注射”治疗剂（即，反对 HMW 4 IgM）用于年龄相关疾病，包括T2 D和CVD。

PROJECT SUMMARY Type 2 diabetes (T2D) is a common disease in older adults and also a risk factor for other age-related diseases. A common link of these diseases is age-related increase in low-grade chronic inflammation (known as “inflammaging”). Chronic inflammation is triggered partly by damage-associated molecular patterns (DAMPs). HMGB1 (High-Mobility Group Box 1) is a prototypical DAMP that is evolutionarily conserved, and it is implicated in the pathogenesis of several age-related diseases including T2D and cardiovascular disease (CVD). Recently, in both normal mice and healthy human blood donors, we identified an endogenous anti- HMGB1 IgM antibody (Ab) that neutralizes the proinflammatory activity of HMGB1, via binding to a highly conserved epitope of HMGB1, namely HMW4. This anti-HMW4 IgM was upregulated in mice in response to challenge with high fat diet (HFD). Critically, the ability to upregulate anti-HMW4 IgM (upon HFD challenge) was impaired in middle-aged (9-month-old) male and older (14-month-old) female mice, which correlated with the increase in vulnerability (or decrease in tolerance) to the diabetogenic effect of HFD, as reflected by more rapid onset of insulin resistance (IR). These data compel us now to test our hypothesis that anti-HMW4 IgM plays a diabeto-protective role, and the age-related impairment in raising this IgM represents one of the factors contributing to the increase in vulnerability to the diabetogenic effect of HFD and, thus, the risk of IR/T2D. We propose two specific aims. Specific Aim #1 is to determine whether anti-HMW4 IgM is diabeto- protective. We will use two complementary approaches: 1) Determining whether infusion of anti-HMW4 IgM into young, middle-aged, and age mice (“gain-of-function”) confers protection against HFD-induced IR and inflammation. 2) Determining whether diminishing this IgM response by depletion of anti-HMW4 IgM-producing B-1 cells in young mice (“loss-of-function”) impairs their tolerance to HFD. Specific Aim #2 is to identify age- related defects in HMW4-reactive B-1 cells that impair the anti-HMW4 IgM response, with the focus on the TLR4 signaling axis. We will use two approaches: 1) Analyzing TLR4 activation in peritoneal HMW4-reactive B-1 cells from young, middle-aged, and aged mice to determine whether middle-aged and aged mice have a defect in TLR4 signaling. 2) Treating middle-aged and aged mice with the TLR4 agonist MPLA to determine whether enhanced TLR4 stimulation restores their anti-HMW4 IgM response and tolerance to HFD. The significance of our studies lies in a few aspects. The studies will identify an age-related mechanism for regulating chronic inflammation and the body’s tolerance to fatty foods. They will provide valuable insight into the immune-metabolic interplay in metabolic challenge. They are expected to yield a novel target for immunotherapy (i.e., anti-HMW4 IgM-producing B cells) and an “injectable” therapeutic (i.e., anti- HMW4 IgM) for age-related diseases including T2D and CVD.