Figure 2.

HFD led to β-cell failure in aged mice, whereas TLR4-depletion could restore β-cell function and survival. (A–H) Young (6 weeks) and old (12 months) WT and Tlr4^−/− mice were fed a normal (ND) or high fat/high sucrose diet (“Surwit”; HFD) for 8 weeks. (A,B) Insulin secretion during an ipGTT with 2 g/kg body weight glucose in week 8 measured before (0 min) and 30 min after glucose injection (A) and calculated as stimulatory index (B). (C–E) Mice were sacrificed at week 8 and islets isolated from all 8 treatment groups, cultured overnight and subjected to an in vitro GSIS assay. (C) Insulin secretion during 1h-incubation with 2.8 mM (basal) and 16.7 mM glucose (stimulated), normalized to (D) insulin content. (E) The insulin stimulatory index denotes the ratio of secreted/basal insulin during 1h-incubation with 16.7 mM and 2.8 mM glucose, respectively. (F) β-cell mass analysed from 10 sections/mouse spanning the whole pancreas. (G,H) Results and representative microscopic images from triple staining for TUNEL, insulin and DAPI expressed as percentage of TUNEL-positive β-cells ±SE. The mean number of β-cells scored was 10,252 for each treatment condition. (H) Arrows point to four TUNEL⁺ β-cells with remaining insulin from an old HFD fed WT mouse. Scale bar, 50 μm. *p < 0.05 ND vs. HFD; **p < 0.05 young vs. old mice; ^#p < 0.05 WT vs. Tlr4^−/− mice. N = 5–9 mice per group; three independent experiments were performed.