酪蛋白糖基化对其胰蛋白酶消化物在免疫低下模型小鼠中免疫活性的影响

Effect of Casein Glycation on Immunoenhancing Activity of Tryptic Caseinate Digest in Immunosuppressed Mice

本研究揭示酪蛋白美拉德糖基化反应对其胰蛋白酶消化物在免疫低下小鼠中免疫活性的影响。通过酪蛋白与乳糖发生美拉德糖基化反应得到糖基化酪蛋白,利用胰蛋白酶消化分别制备酪蛋白消化物和糖基化酪蛋白消化物,并用80 mg/kg mb的环磷酰胺处理小鼠3 d以诱导其出现免疫低下;低(100 mg/kg mb)、中(200 mg/kg mb)和高(400 mg/kg mb)剂量的酪蛋白消化物灌胃小鼠25 d后,测定小鼠免疫器官指数(脾脏指数和胸腺指数)、血清生化指标、血清免疫球蛋白(immunoglobulin,Ig)质量浓度、脾淋巴细胞增殖指数和自然杀伤(natural killer,NK)细胞活力。结果表明,与生理盐水处理的正常组小鼠相比,模型组小鼠的免疫状况低下,其免疫器官指数、血清生化指标、血清中Ig质量浓度、脾淋巴细胞增殖指数和NK细胞活力等指标显著降低(P<0.05)。与模型组小鼠相比,中、高剂量酪蛋白消化物灌胃小鼠脾脏指数和胸腺指数分别增加35.9%~66.4%和50.5%~62.9%,血清IgM、IgA和IgG质量浓度分别增加21.6%~30.4%、27.1%~41.8%和37.2%~45.1%,脾淋巴细胞增殖指数及NK细胞活力分别增加34.2%~51.1%和32.1%~90.7%;中、高剂量糖基化酪蛋白消化物灌胃小鼠后脾脏指数和胸腺指数分别增加27.7%~51.9%和39.2%~52.6%,血清IgM、IgA和IgG质量浓度分别增加19.1%~29.0%、21.8%~35.3%和30.1%~41.6%,脾淋巴细胞增殖指数及NK细胞活力分别增加32.9%~41.6%和27.3%~81.1%。酪蛋白消化物和糖基化酪蛋白消化物均可明显减轻由环磷酰胺引起的上述免疫指标水平下降,且酪蛋白消化物比糖基化酪蛋白消化物具有更好的免疫指标水平提升作用。酪蛋白的美拉德糖基化反应会降低酪蛋白消化物对小鼠免疫状况的提升作用。

This study aimed to assess the potential effect of casein glycation via the Maillard reaction on in vivo immunoenhancing efficacy of tryptic casein digest in immunosuppressed mice. Glycated casein was prepared by the Maillard reaction of casein with lactose. Glycated and native casein were digested with trypsin to generate glycated casein digest and casein digest, respectively. Mice were treated with cyclophosphamide at 80 mg/kg mb for 3 days to induce immunosuppression, and then were given the two digests, separately at dose levels of 100, 200, and 400 mg/kg mb for 25 days. Afterwards, immune organ(spleen and thymus) indices, serum biochemical indices, immunoglobulin(IgM, IgA, and IgG) levels, lymphocyte proliferation capacity, and natural killer(NK) cell viability were evaluated. Results indicated that the immune status of mice in the model group was lower than that in the control group treated with normal saline as manifested by a significant decrease in immune organ indices, serum biochemical indices, serum Ig levels, spleen lymphocyte proliferation index and NK cell viability(P < 0.05). Compared with the immunosuppressed mice, spleen and thymus indices, serum IgM, IgA and IgG levels, spleen lymphocyte proliferation index, and NK cell viability increased by 35.9%–66.4%, 50.5%–62.9%, 21.6%–30.4%, 27.1%–41.8%, 37.2%–45.1%, 34.2%–51.1%, and 32.1%–90.7% in the mice treated with casein digest at the medium and high doses, and by 27.7%–51.9%, 39.2%–52.6%, 19.1%–29.0%, 21.8%–35.3%, 30.1%–41.6%, 32.9%–41.6%, and 27.3%–81.1% in the mice treated with glycated casein digest at the medium and high doses, respectively. Both digests were able to attenuate the decrease in immune indices of immune suppressed mice induced by cyclophosphamide, while casein digest showed higher immuno enhancing efficacy than glycated casein digest. Therefore, casein glycation via the Maillard reaction could decrease the immunoenhancing activity of its tryptic digest on mice.