Generation of animal model of diabetes by disrupting the ADP-ribosyl cyclase (CD38) gene

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1. We produced CD38 (+/-) mice by homologous recombination in ES cells and subsequent Cre-lox P recombination. By crosses between heterozygous mutants (+/-), homozygotes (-/-) were yielded in the F2 generation in a distribution following Mendelian rules ; hence CD38-/- mice seemed to survive fetal development normally.2.RT-PCR and Western blot analysis showed that there was no detectable CD38 mRNA and protein in pancreatic islets from CD38-/- mice, suggesting that the gene disruption resulted in a null mutation of CD38.3. As compared with CD38+/+ islet homogenates, the ADP-ribosyl cy clase, cADPR hydrolase and NAD+-glycohydrolase activities of CD38-/- islet homogenates were greatly reduced, indicating that CD38 is mainly responsible for the synthesis and hydrolysis of cADPR in pancreatic beta cells.4. By radioimmunoassay, the cADPR content in CD38+/+ islets was greatly increased by high glucose stimulation. Although some amounts of cADPR were detected in CD3 8-I- islets when incubated … More in low glucose, the cADPR content was not at all increased by high glucose stimulation.5. The glucose-stimulated [Ca2+]i rise in CD38-/- islets was much lower than that in CD38+/+ islets in the digital imaging of fura-2 fluorescence.6. Although there were no significant differences in insulin secretion between CD38+/+ and CD38-/- islets at 2.5 and 10 mM glucose, insulin secretion from CD38-/- islets at 20 and 30 mM glucose was more than 50% decreased compared with CD38+/+ islets.7. In glucose-tolerance test, At 30 and 60 min after glucose injection, CD38-/- mice had much higher glucose levels than CD38+/+ mice. In CD38-/- mice, serum insulin levels at 15 ruin after glucose injection were significantly lower than those of CD38+/+ mice.8. CD38-/- mice carrying the human CD38 transgene were generated. The human CD38 transgene ameliorated the glucose intolerance and the decreased insulin secretion.9. Overall results indicate that the CD38-/- mice are suitable animal model of noninsulin-dependent diabetes mellitus. In fact, we found CD38 missense mutation and autoantibodies against CD38 in noninsulin-dependent diabetic patients. Less