Fig. 1. Isolated pancreatic islets display rhythmic insulin secretion and transcription of secretory genes in mice and humans.

(A) Glucose and KCl-stimulated insulin secretion in synchronized WT mouse islets across either 3 or 2 consecutive days, respectively (n=3 replicate sets of islets pooled from 6–9 mice each) (bottom). Bioluminescence monitoring (counts/sec) in islets from Per2^Luc reporter mice was performed in parallel (top). (B) Glucose-stimulated insulin secretion in ethanol- or tamoxifen-treated islets from PdxCreER;Bmal1^flx/flx mice at the nadir (36 hr post-forskolin shock) and zenith (48 hr post-forskolin shock) of cyclic insulin secretion in wild-type islets from Fig. 1A (n=4 islet pools per time point, 3 replicates per islet pool). Of note, ethanol-treated islets displayed significant difference in GSIS comparing 36- to 48-hrs (p=0.038), whereas tamoxifen-treated islets did not (p=0.974). (C) Bmal1 and Rev-erbα RNA expression (top) and heatmap of all cycling genes identified by eJTK_CYCLE analysis (middle). Significantly enriched KEGG ontology pathways shown within the cycling gene set (bottom). (D) Peak phase expression (hrs post-forskolin shock) of cycling genes in synchronized WT islets (left) that were also altered in PdxCre;Bmal1^flx/flx islets at ZT2. Log₂ fold change in expression in PdxCre;Bmal1^flx/flx (KO) islets compared to Bmal1^flx/flx (control) at ZT2 (right) for subset of genes relevant to insulin secretion. (E) Heatmap showing expression patterns of cycling trafficking and exocytosis genes in synchronized human islets. (F) Mapping of cycling RNAs in both human and mouse islets onto the “Insulin Secretion” KEGG pathway. All values represent mean ± SEM. *p<0.05, ***p<0.001.