Upregulation of Fpn expression in diabetic mice and humans. (A,C,E) Fpn protein expression in the duodenum and (B,D,F) spleen of (A-B) STZ-treated mice, (C-D) db/db mice, and (E-F) KKAy mice, with glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as an internal control. The percentages of change in Fpn expression (underneath the blots) in diabetic mice over the control are shown as mean ± SEM (n = 6 for panels A-D, and n = 4 for panels E-F). (G) Representative Fpn staining of the duodenum of type 2 diabetic (T2DM) and human patients who are nondiabetic. (H) Quantified arbitrary fluorescent intensity of membrane Fpn in T2DM and control patients. Data are mean ± SEM (n = 14 human patients). For each duodenal sample, fluorescent signal was measured in 10 representative cells by ImageJ and the average was obtained. Liver Hamp1 mRNA expression was determined by quantitative reverse transcription polymerase chain reaction in (I) STZ-treated mice, (K) db/db, and (M) KKAy mice. Serum hepcidin content was determined in (J) STZ-treated and (L) db/db mice by enzyme-linked immunosorbent assay. ∗P < .01 and ∗∗P < .05 compared with the corresponding controls. Bar, 50 μm.