Clinical significance of auto natural anti-insulin antibodies in normal cats

研究发现猫血清中存在抗胰岛素的天然自身抗胰岛素抗体，即IgG。为了阐明抗胰岛素igg的意义，我们开发了一种夹心ELISA法测定猫血清中的igg。ELISA的准确度足以测定胰岛素结合IgG的浓度。采用该ELISA法测定了130只家猫和11种其他猫科动物（狮子、豹子、雪豹、山猫和猞猁）血浆中抗胰岛素IgG的浓度。抗胰岛素igg在所有个体中检测到80 ~ 4884 μg/ml。瘦猫体内抗胰岛素IgG浓度较高，且与总IgG浓度呈正相关，与血浆葡萄糖和胰岛素浓度不相关。糖尿病猫的血浆抗胰岛素IgG浓度略高，但在正常猫的范围内。新生幼猫脐带血中未检测到抗胰岛素igg，哺乳后呈升高趋势。这些母源抗体在哺乳期逐渐下降，在断奶时逆转下降趋势。用牛胰岛素固定柱亲和层析法分离抗胰岛素igg。利用牛胰岛素的部分肽进行表位定位。抗原识别部分是外推胰岛素分子A链和B链的亲水末端。采用高效液相色谱法将血清抗胰岛素igg分为4个组分。通过使用峰值分数，我们在培养的来源于猫的脂肪细胞中检测到磷酸化的酪氨酸蛋白。与游离胰岛素相比，加入IgG结合胰岛素后的磷酸化作用更强，提示抗胰岛素IgG可能增强了胰岛素的作用。

It has been revealed that there have been anti-insulin natural auto anti-insulin antibodies in serum of cats, and those were the IgG. To clarify the significance of anti-insulin IgGs, we developed a sandwich ELISA for determination of the IgGs in serum of cats. The accuracy of the ELISA was sufficient for determination of insulin-bound IgG concentrations. By used of this ELISA, we determined plasma anti-insulin IgG concentrations in 130 domestic cats and 11 other felidae(lions, leopards, snow leopards, bobcats and lynx). Anti-insulin IgGs were detected in ranges from 80 to 4, 884μg/ml in all individuals. Anti-insulin IgG concentrations were high in lean cats, and correlated positively with total IgG concentrations, but not with plasma glucose and insulin concentrations. In cats with diabetes mellitus, plasma anti-insulin IgG concentrations were slightly high, but within the range of normal cats. Anti-insulin IgGs were not detected in cord blood of newborn kittens, and increased after suckling. These maternal antibodies decreased gradually during suckling period, and reversed the falling trend at weaning.Anti-insulin IgGs were fractionated by affinity chromatography with a column fixed bovine insulin. Epitope mapping was carried out by use of partial peptides of bovine insulin. The antigen-recognition parts were extrapolated hydrophilic terminals of A and B chains of insulin molecule.Serum anti-insulin IgGs were divided into 4 fractions by high performance liquid chromatography. By use of a fraction with highest peak, we detected a phosphorylated tyrosine proteins in cultured adipocytes derived from the cat. The phospholylation was stronger after addition of the IgG-binding insulin than free insulin, suggesting that the anti-insulin IgG might enhance the action of insulin.