Aim: To test whether the neurogenic differentiation (NeuroD) protein could alle-viate symptoms of diabetes mellitus by its transduction activity in vivo. Methods:Type 1 diabetes mellitus in mice was induced by ip (intraperitoneal) injection of streptozotocin (150 mg/kg). One group of diabetic mice were intravenously injected with the NeuroD-EGFP (Enhanced Green Fluorescent Protein) (5 mg/kg,n=6) and the other group with EGFP (5 mg/kg, n=5). After the transduction of NeuroD-EGFP, the distribution of the protein was examined by means of frozen section under fluorescent microscope observation. We conducted RT-PCR and Real-time quantitative PCR to measure the transcription levels of insulin mRNA.Immunohistochemistry was utilized to detect the insulin protein. Radioimmu-noassay was conducted to determine the serum insulin levels. Blood glucose levels and body weights were regularly recorded after the protein administration.Results: The NeuroD protein can be transduced into cells in vivo with a high efficiency of nearly 100%. Insulin mRNA was highly expressed in NeuroD-treated diabetic mice, 38-fold higher than that of control group (P<0.05). Immunohis-tochemistry revealed enteric insulin expression in the NeuroD-treated diabetic mice. The fasting serum insulin level of the NeuroD-EGFP group (n=6) was 337±39 pg/mL, significantly higher than that of the control diabetic mice (n=5) which was 84±23 pg/mL (P<0.01, t-test). Records of blood glucose level also displayed alle-viation of hyperglycemia after NeuroD administration (P<0.01, t-test, n=6). Conclusion: In vivo-transduced NeuroD in the small intestine remained function-ally active and could ameliorate the non-fasting glucose levels of streptozotocin-induced, diabetic mice by inducing enteric insulin expression.