XBP1 and diabetes mellitus: At the single time point analyzed in this mouse model with ~ 50% reduced insulin production and prior to onset of diabetes and hyperglycemia, Ins2 mRNA levels were 1.4-fold reduced (with no Ins1 transcripts) and was associated with transcriptional and functional reductions in regulators of ER stress, including Trib3, Atf5, Ddit3, and Xbp1 splicing, leading also to an increase in β-cell proliferation [96].