Figure 6: STZ and Zn2+ reduce NAD+ levels in MIN6 cells which are restored by exogenous NAD+ MIN6 cells were exposed as indicated for 3 hours. Cells were lysed, NAD+ was extracted and assayed by the enzymatic micro-cycling assay, and the concentration was determined. * signifies a significant difference from control. # indicates a significant difference from 40 micromol/L Zn2+ exposure alone. $ indicates a significant difference from 10 millimol/L STZ exposure alone. & indicates a significant difference from cytokine exposure alone at P <0.05.