Absence of Diabetes and Pancreatic Exocrine Dysfunction in a Transgenic Model of Carboxyl-Ester Lipase-MODY (Maturity-Onset Diabetes of the Young)

BackgroundCEL-MODY is a monogenic form of diabetes with exocrine pancreatic insufficiency caused by mutations in CARBOXYL-ESTER LIPASE (CEL). The pathogenic processes underlying CEL-MODY are poorly understood, and the global knockout mouse model of the CEL gene (CELKO) did not recapitulate the disease. We therefore aimed to create and phenotype a mouse model specifically over-expressing mutated CEL in the pancreas. MethodsWe established a monotransgenic floxed (flanking LOX sequences) mouse line carrying the human CEL mutation c.1686delT and crossed it with an elastase-Cre mouse to derive a bitransgenic mouse line with pancreas-specific over-expression of CEL carrying this disease-associated mutation (TgCEL). Following confirmation of murine pancreatic expression of the human transgene by real-time quantitative PCR, we phenotyped the mouse model fed a normal chow and compared it with mice fed a 60% high fat diet (HFD) as well as the effects of short-term and long-term cerulein exposure. ResultsPancreatic exocrine function was normal in TgCEL mice on normal chow as assessed by serum lipid and lipid-soluble vitamin levels, fecal elastase and fecal fat absorption, and the normoglycemic mice exhibited normal pancreatic morphology. On 60% HFD, the mice gained weight to the same extent as controls, had normal pancreatic exocrine function and comparable glucose tolerance even after resuming normal diet and follow up up to 22 months of age. The cerulein-exposed TgCEL mice gained weight and remained glucose tolerant, and there were no detectable mutation-specific differences in serum amylase, islet hormones or the extent of pancreatic tissue inflammation. ConclusionsIn this murine model of human CEL-MODY diabetes, we did not detect mutation-specific endocrine or exocrine pancreatic phenotypes, in response to altered diets or exposure to cerulein.背景：CEL-MODY是一种由羧基酯脂肪酶（CARBOXYL-ESTER LIPASE, CEL）基因突变引发的单基因糖尿病合并胰腺外分泌功能不全。目前学界对CEL-MODY的致病机制尚不清楚，且CEL基因全身敲除小鼠模型（CELKO）未能重现该疾病的表型。为此，本研究旨在构建并表型鉴定一种在胰腺中特异性过表达突变型CEL的小鼠模型。 方法：我们构建了携带人类CEL基因c.1686delT突变、floxed（侧翼携带loxP序列）的单转基因小鼠品系，并将其与弹性蛋白酶-Cre小鼠交配，获得了可在胰腺中特异性过表达该疾病相关突变型CEL的双转基因小鼠品系（TgCEL）。通过实时定量聚合酶链反应（real-time quantitative PCR）验证该人类转基因在小鼠胰腺中的表达后，我们对饲喂正常饲料的TgCEL小鼠进行表型鉴定，并将其与饲喂60%高脂饮食（high fat diet, HFD）的小鼠进行对比，同时探究了短期与长期雨蛙素（cerulein）暴露对该模型的影响。 结果：通过血清脂质与脂溶性维生素水平、粪便弹性蛋白酶活性及粪便脂肪吸收率评估发现，饲喂正常饲料的TgCEL小鼠胰腺外分泌功能正常，且血糖正常的小鼠胰腺形态学表现亦无异常。在饲喂60%高脂饮食时，TgCEL小鼠的体重增长幅度与对照组小鼠一致，胰腺外分泌功能正常，即使在恢复正常饲料并饲养至22月龄时，其糖耐量仍与对照组无显著差异。经雨蛙素暴露的TgCEL小鼠体重正常增长且糖耐量保持稳定，血清淀粉酶、胰岛激素水平及胰腺组织炎症程度均未出现与突变相关的特异性差异。 结论：在该人类CEL-MODY糖尿病的小鼠模型中，无论饲喂不同日粮或暴露于雨蛙素，我们均未检测到与该突变相关的胰腺内分泌或外分泌功能异常表型。