A post hoc secondary analysis of the aforementioned trial [85] found that vitamin D2 significantly decreased fasting proinsulin-to-C-peptide ratio—a biomarker of beta-cell endoplasmic reticulum stress [86]—and slowed the decrease in the area under the curve (AUC) of C-peptide in youth with newly diagnosed T1D [85]. Here, INS is linked to type 1 diabetes mellitus.