The influence of genetic background on the induction of oxidative stress and impaired insulin secretion in mouse islets

Aims/hypothesis We determined whether high-glucose-induced beta cell dysfunction is associated with oxidative stress in the DBA/2 mouse, a mouse strain susceptible to islet failure.

Materials and methods Glucose- and non-glucose-mediated insulin secretion from the islets of DBA/2 and control C57BL/6 mice was determined following a 48-h exposure to high glucose. Flux via the hexosamine biosynthesis pathway was assessed by determining O-glycosylated protein levels. Oxidative stress was determined by measuring hydrogen peroxide levels and the expression of anti-oxidant enzymes.

Results Exposure to high glucose levels impaired glucose-stimulated insulin secretion in DBA/2 islets but not C57BL/6 islets, and this was associated with reduced islet insulin content and lower ATP levels than in C57BL/6 islets. Exposure of islets to glucosamine for 48 h mimicked the effects of high glucose on insulin secretion in the DBA/2 islets. High glucose exposure elevated O-glycosylated proteins; however, this occurred in islets from both strains, excluding a role for O-glycosylation in the impairment of DBA/2 insulin secretion. Additionally, both glucosamine and high glucose caused an increase in hydrogen peroxide in DBA/2 islets but not in C57BL/6 islets, an effect prevented by the antioxidant N-acetyl-l-cysteine. Interestingly, while glutathione peroxidase and catalase expression was comparable between the two strains, the antioxidant enzyme manganese superoxide dismutase, which converts superoxide to hydrogen peroxide, was increased in DBA/2 islets, possibly explaining the increase in hydrogen peroxide levels.

Conclusions/interpretation Chronic high glucose culture caused an impairment in glucose-stimulated insulin secretion in DBA/2 islets, which have a genetic predisposition to failure, and this may be the result of oxidative stress.

Lower whole blood glutathione peroxidase (GPX) activity in depression, but not in myalgic encephalomyelitis / chronic fatigue syndrome: another pathway that may be associated with coronary artery disease and neuroprogression in depression

BAKGROUND: Major depression and myalgic encephalomyelitis / chronic fatigue syndrome (ME/CFS) are two disorders accompanied by an upregulation of the inflammatory and oxidative and nitrosative (IO&NS) pathways and a decreased antioxidant status. Moreover, depression is accompanied by disorders in inflammatory and neuroprogressive (IN-PRO) pathways.

METHODS: This study examines whole blood glutathione peroxidase (GPX) in depression and in ME/CFS; GPX is an enzyme that reduces hydroperoxides by oxidizing glutathione and consequently protects the cells from oxidative damage. Blood was sampled in 39 patients with depression, 40 patients with ME/CFS and 24 normal volunteers. Whole blood was analysed for GPX activity using the Ransel assay (Randox). Severity of illness was measured by means of the Hamilton Depression Rating Scale (HDRS) and the Fibromyalgia and Chronic Fatigue Syndrome Rating Scale (FF scale).

RESULTS: We found that whole blood GPX activity was significantly (p=0.001) lower in depressed patients than in normal controls and that there were no significant differences between ME/CFS and controls. In depression and ME/CFS, there were significant and inverse relationships between GPX activity and the FF items, depressed mood and autonomic symptoms. In depression, there were significant and negative correlations between whole blood GPX and the HDRS score and autonomic symptoms.

DISCUSSION: The results show that lowered whole blood GPX activity contributes to the lowered antioxidant status in depression. Since GPX activity is a predictor of neuroprogression and coronary artery disease (CAD), lowered GPX activity in depression contributes to the IN-PRO pathways and the comorbidity between depression and CAD. Our results suggest that patients with depression would benefit from Ebselen or a supplementation with glutathione, N-Acetyl-l-Cysteine and selenium.

Glutathione peroxidase-1 reduces influenza A virus-induced lung inflammation

Oxidative stress caused by excessive reactive oxygen species production is implicated in influenza A virus–induced lung disease. Glutathione peroxidase (GPx)-1 is an antioxidant enzyme that may protect lungs from  such damage. The objective of this study was to determine if GPx-1 protects the lung against influenza A virus–induced lung inflammation in vivo.

A review of recent advances in chemiluminescence detection using nano-colloidal manganese(IV)

The application of 'soluble' (colloidal) manganese(IV) for chemiluminescence detection is reviewed, focussing on papers published since the last comprehensive review of the subject in 2008. Advances in this reagent system include: the on-line formation of manganese(IV); new insight into the light-producing pathway and selectivity of the reagent; its application to assess total antioxidants in plant derived samples and oxidative stress in biological fluids and tissues; and the replacement of the formaldehyde enhancer with ethanol.