FIG. 3.

Changes in mRNA expression of UPR genes in islets of db/db and ob/ob mice at 6 and 16 weeks of age. Islets were isolated from 9 to 10 C57BL/KsJ control and 8 db/db mice at 6 weeks of age, 13 to 16 C57BL/KsJ control and 9 to 12 db/db mice at 16 weeks of age, 6 C57BL/6J control and 6 ob/ob mice at 6 weeks of age, and 4 to 5 C57BL/6J control and 7 ob/ob mice at 16 weeks of age. Shown are changes for the indicated genes in islets of db/db (A, C, E) and ob/ob (B, D, F) mice at 6 (white bars) and 16 (black bars) weeks of age. A–D: Total RNA was extracted, reverse-transcribed, and analyzed by real-time RT-PCR. mRNA levels were expressed as fold change of the levels in respective age-matched controls (represented by the dashed line). E and F: Xbp1 cDNA was amplified by PCR and digested with PstI, which cuts unprocessed Xbp1 into fragments. Processed (activated) Xbp1 lacks the restriction site and remains intact. Processed (intact) and unprocessed (cut) Xbp1 were quantified by densitometry. The value obtained for processed Xbp1 was expressed as a ratio of the total (processed + unprocessed) Xbp1 mRNA level for each sample. These ratios are expressed as fold change of the ratio in respective age-matched controls. All results are mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001 genotype effect in each age group.