The effect of glucose is dependent on uptake rather than insulin signaling. (A) Levels of ATP, pyruvate, and lactate in whole-embryo lysates increased significantly in response to glucose (t test, ATP, pyruvate: *P < .02; lactate: **P < .05, n = 3). (B) Measurement of total embryo glucose content by enzymatic assay revealed significantly elevated glucose levels at 36 hpf after exposure to 1% glucose in the fish water from 12 to 36 hpf, which declined back to baseline by 72 hpf (analysis of variance [ANOVA], *P < .05, n = 3). (C) Glucose uptake, measured by radioisotope labeling, was significantly enhanced in the embryo after 60 minutes of exposure in the fish water (ANOVA, P = .012, n = 3). (D) Confocal microscopy of lmo2:dsRed transgenic reporter embryos at 36 hpf following exposure to 2-NBDG reveals green fluorescent glucose signal in the zebrafish aorta (arrowhead), colocalized with an increased number of lmo2⁺ hematopoietic cells; white dotted lines indicate the trunk of the embryo, the dashed line demarks the yolk (below) from the embryo proper (above). The inset shows GFP levels in untreated fish at the same signal amplification as 2-NBDG–treated samples (n = 5/tx). (E) FACS analysis reveals significant and selective uptake of the fluorescent glucose analog 2-NBDG (green fluorescence) by hematopoietic and endothelial lmo2⁺ cells (t test, *P < .05, n = 10). (F) MO knockdown of glut1 (40μM) inhibited the effect of glucose on runx1/cmyb⁺ HSCs. insr (40μM) knockdown did not affect runx1/cmyb expression in the presence or absence of glucose (17 normal/22). (G) Glucose exposure did not affect insulin expression prior to islet formation at 36 hpf (36 normal/36).