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. 2011 Oct 17;60(11):2710–2719. doi: 10.2337/db11-0132

FIG. 2.

FIG. 2.

Glucose-induced mitochondrial membrane hyperpolarization is mildly increased in UCP2BKO β-cells, while islet ATP content and uncoupled respiration rates remain unchanged. A: Representative traces of ΔΨm measurements using rhodamine123 in selected large cells (β-cells) from dispersed islets isolated from UCP2BKO and RIPCre mice. ΔΨm was measured initially in the presence of a low (2.8 mmol/L) glucose concentration. Membrane hyperpolarization was induced by the addition of high (20 mmol/L) glucose concentration, and 5 mmol/L sodium azide (NaN3) was used to completely depolarize the mitochondrial membrane to ensure membrane integrity. n = 5 mice/genotype. RFU, relative fluorescence units. B: Measurements of ΔΨm were normalized to basal fluorescence in the presence of low (2.8 mmol/L) glucose concentration and then expressed relative to RIPCre control ΔΨm levels. Δ1, the change in mitochondrial membrane hyperpolarization in response to increased glucose concentration. Δ2, the change in mitochondrial membrane depolarization in response to NaN3 above basal mitochondrial membrane potential. (20–30 cells/coverslip with 3 coverslips per animal were measured.) n = 5 mice/genotype. ***P < 0.001. C: Uncoupled OCR is unchanged in UCP2BKO islets. OCR was measured under saturating concentrations of oligomycin (5 µmol/L) with 3 or 20 mmol/L glucose. Measurements shown are after steady state was achieved. n = 3 separate experiments, with 13–15 measurements per condition. D: Basal OCR is increased in UCP2BKO islets. Measurements are steady state in 3 mmol/L glucose. **P < 0.01. n = 3 separate experiments with 27 (control) and 30 (UCP2BKO) measurements per condition. E: Glucose-stimulated oxygen consumption (expressed as a percentage of the basal OCR) is similar between UCP2BKO and RIPCre islets. Both genotypes experience a 1.5-fold increase in OCR after stimulation with glucose. OCRs were measured in 3 and 20 mmol/L glucose. Measurements were taken after steady state was achieved. n = 4 separate experiments with 18 (control) and 20 (UCP2BKO) measurements per condition. F: Islet ATP content in RIPCre and UCP2BKO islets cultured overnight and incubated in low (2.8 mmol/L) or high (16.7 mmol/L) glucose for 30 min. n = 3 mice/genotype; *P < 0.05. LG, low glucose; HG, high glucose. The error bars show the SEM.