In the short-term insulin resistance model: SerpinB1-deficient mice show reduced beta-cell proliferation (~40%) when challenged with S961, with similar impairment in beta-cell proliferation (~50%) when challenged with high-fat diet (HFD), though beta-cell mass was not significantly different in either condition. In the long-term insulin resistence model (longer HFD period): SerpinB1-deficient mice show reduced beta-cell proliferation as well as cell mass.