Figure 1.

Effects of serum deprivation and reduction in ambient glucose concentrations on β-cell gene expression. INS-1 cells were grown in RPMI 1640 containing 10% FCS and 11.1 mm glucose (growth medium). At 80% confluence the cells were washed and incubated for 24 h in growth medium or in serum-free DMEM (5.5 mm glucose, 0.1% human serum albumin). RNA levels were measured by quantitative PCR. Values for cells incubated in growth medium (serum) were adjusted so that the mean equaled 1.0; values for cells in serum-free medium were calculated as a function of the mean of serum-replete values. The figures show the means ± sem of all data from three independent experiments, each of which contained four flasks per treatment group. Statistically significant differences between the experimental groups are indicated by asterisks. *, P < 0.05; **, P < 0.01; ***, P < 0.001.