AIMS/HYPOTHESIS: Hydrogen peroxide (H2O2)-inactivating enzymes such as catalase are produced in extraordinarily low levels in beta cells. Whether this low expression might be related to a signalling function of H2O2 within the beta cell is unknown. A high level of H2O2-inactivating enzymes could potentially be incompatible with glucose-induced insulin secretion. Therefore the effect of catalase overexpression on mitochondrial function and physiological insulin secretion was studied in insulin-secreting INS-1E and primary islet cells. METHODS: INS-1E and rat islet cells were lentivirally transduced to overexpress catalase in the cytosol (CytoCat) or in mitochondria (MitoCat). Cell viability and caspase-3 activation were assessed after cytokine incubation and hypoxia. Insulin secretion was quantified and expression of the gene encoding the mitochondrial uncoupling protein 2 (Ucp2) was measured in parallel to mitochondrial membrane potential and reactive oxygen species (ROS) formation. RESULTS: The ability to secret insulin in a glucose-dependent manner was not suppressed by catalase overexpression, although the glucose-dependent increase in the mitochondrial membrane potential was attenuated in MitoCat cells along with an increased Ucp2 expression and reduced mitochondrial ROS formation. In addition, MitoCat overexpressing cells were significantly more resistant against pro-inflammatory cytokines and hypoxia than CytoCat and control cells. CONCLUSIONS/ INTERPRETATION: The results demonstrate that an improved antioxidative defence status of insulin-secreting cells allowing efficient H2O2 inactivation is not incompatible with proper insulin secretory responsiveness to glucose stimulation and provide no support for a signalling role of H2O2 in insulin-secreting cells. Interestingly, the results also document for the first time that the decreased ROS formation with increasing glucose concentrations is of mitochondrial origin.
AIMS/HYPOTHESIS: Hydrogen peroxide (H2O2)-inactivating enzymes such as catalase are produced in extraordinarily low levels in beta cells. Whether this low expression might be related to a signalling function of H2O2 within the beta cell is unknown. A high level of H2O2-inactivating enzymes could potentially be incompatible with glucose-induced insulin secretion. Therefore the effect of catalase overexpression on mitochondrial function and physiological insulin secretion was studied in insulin-secreting INS-1E and primary islet cells. METHODS: INS-1E and rat islet cells were lentivirally transduced to overexpress catalase in the cytosol (CytoCat) or in mitochondria (MitoCat). Cell viability and caspase-3 activation were assessed after cytokine incubation and hypoxia. Insulin secretion was quantified and expression of the gene encoding the mitochondrial uncoupling protein 2 (Ucp2) was measured in parallel to mitochondrial membrane potential and reactive oxygen species (ROS) formation. RESULTS: The ability to secret insulin in a glucose-dependent manner was not suppressed by catalase overexpression, although the glucose-dependent increase in the mitochondrial membrane potential was attenuated in MitoCat cells along with an increased Ucp2 expression and reduced mitochondrial ROS formation. In addition, MitoCat overexpressing cells were significantly more resistant against pro-inflammatory cytokines and hypoxia than CytoCat and control cells. CONCLUSIONS/ INTERPRETATION: The results demonstrate that an improved antioxidative defence status of insulin-secreting cells allowing efficient H2O2 inactivation is not incompatible with proper insulin secretory responsiveness to glucose stimulation and provide no support for a signalling role of H2O2 in insulin-secreting cells. Interestingly, the results also document for the first time that the decreased ROS formation with increasing glucose concentrations is of mitochondrial origin.
Authors: Timo Otonkoski; Nina Kaminen; Jarkko Ustinov; Risto Lapatto; Thomas Meissner; Ertan Mayatepek; Juha Kere; Ilkka Sipilä Journal: Diabetes Date: 2003-01 Impact factor: 9.461
Authors: Xin Gen Lei; Jian-Hong Zhu; Wen-Hsing Cheng; Yongping Bao; Ye-Shih Ho; Amit R Reddi; Arne Holmgren; Elias S J Arnér Journal: Physiol Rev Date: 2016-01 Impact factor: 37.312
Authors: K Kluckova; M Sticha; J Cerny; T Mracek; L Dong; Z Drahota; E Gottlieb; J Neuzil; J Rohlena Journal: Cell Death Dis Date: 2015-05-07 Impact factor: 8.469
Authors: Ritesh Kumar Baboota; Abhijit Babaji Shinde; Katleen Lemaire; Marc Fransen; Stefan Vinckier; Paul P Van Veldhoven; Frans Schuit; Myriam Baes Journal: Mol Metab Date: 2019-02-08 Impact factor: 7.422