IRS-1 transgenic mice show increased epididymal fat mass and insulin resistance.

Insulin receptor substrate-1 (IRS-1) is the major substrate of both the insulin receptor and the IGF-1 receptor. In this study, we created IRS-1 transgenic (IRS-1-Tg) mice which express human IRS-1 cDNA under control of the mouse IRS-1 gene promoter. In the IRS-1-Tg mice, IRS-1 mRNA expression was significantly increased in almost all tissues, but its protein expression was increased in very limited tissues (epididymal fat and skeletal muscle). IRS-1-Tg mice showed glucose intolerance and significantly enlarged epididymal fat mass, as well as elevated serum TNF-alpha concentrations. Importantly insulin signaling was significantly attenuated in the liver of IRS-1-Tg mice, which may contribute to the glucose intolerance. Our results suggest that excess IRS-1 expression may not provide a beneficial impact on glucose homeostasis in vivo.

Undifferentiated carcinoma of the common bile duct: case report and review of the literature.

A 78-year-old Japanese man with undifferentiated carcinoma of the common bile duct is presented. Upon gross examination, the common bile duct was found to be obstructed by a nodule measuring 10 x 10 mm. Microscopically, the nodule was ill-defined and composed of atypical spindle-shaped and pleomorphic tumor cells. The spindle-shaped cells proliferated in a whirled or interlacing pattern simulating a sarcoma, and the pleomorphic tumor cells had abundant eosinophilic cytoplasm and bizarre nuclei. Histochemically, a few tumor cells contained mucosubstances stained with the alcian blue (AB) method in their cytoplasm. Immunohistochemically, the tumor cells were diffusely positive for CAM5.2 and AE1/AE3. The histological diagnosis was undifferentiated carcinoma (spindle cell carcinoma) of the common bile duct. Other than our patient, only four other cases of undifferentiated carcinoma in the extrahepatic bile duct have been reported in the literature.