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ABSTRACT: Oxidative damage has been reported to be involved in the pathogenesis of diabetic neuropathy and neurodegenerative diseases. Recent evidence suggests that the antidiabetic drug metformin prevents oxidative stress-related cellular death in non-neuronal cell lines. In this report, we point to the direct neuroprotective effect of metformin, using the etoposide-induced cell death model. The exposure of intact primary neurons to this cytotoxic insult induced permeability transition pore (PTP) opening, the dissipation of mitochondrial membrane potential (DeltaPsim), cytochrome c release, and subsequent death. More importantly, metformin, together with the PTP classical inhibitor cyclosporin A (CsA), strongly mitigated the activation of this apoptotic cascade. Furthermore, the general antioxidant N-acetyl-L: -cysteine also prevented etoposide-promoted neuronal death. In addition, metformin was shown to delay CsA-sensitive PTP opening in permeabilized neurons, as triggered by a calcium overload, probably through its mild inhibitory effect on the respiratory chain complex I. We conclude that (1) etoposide-induced neuronal death is partly attributable to PTP opening and the disruption of DeltaPsim, in association with the emergence of oxidative stress, and (2) metformin inhibits this PTP opening-driven commitment to death. We thus propose that metformin, beyond its antihyperglycemic role, can also function as a new therapeutic tool for diabetes-associated neurodegenerative disorders.
Journal of Molecular Neuroscience 02/2008; 34(1):77-87. · 2.50 Impact Factor
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ABSTRACT: The flavonoid silibinin has been reported to be beneficial in several hepatic disorders. Recent evidence also suggests that silibinin could be beneficial in the treatment of type 2 diabetes, owing to its anti-hyperglycemic properties. However, the mechanism(s) underlying these metabolic effects remains unknown.
The effects of silibinin on liver gluconeogenesis were studied by titrating hepatocytes from starved rats with sub-saturating concentrations of various exogenous substrates in a perifusion system. Hepatocytes from fed rats were also used to investigate glycogenolysis from endogenous glycogen. The effect of silibinin on glucose-6-phosphatase kinetics was determined in intact and permeabilized rat liver microsomes.
Silibinin induced a dose-dependent inhibition of gluconeogenesis associated with a potent decrease in glucose-6-phosphate hydrolysis. This effect was demonstrated whatever the gluconeogenic substrates used, i.e. dihydroxyacetone, lactate/pyruvate, glycerol and fructose. In addition, silibinin decreased the glucagon-induced stimulation of both gluconeogenesis and glycogenolysis, this being associated with a reduction of glucose-6-phosphate hydrolysis. Silibinin inhibits glucose-6-phosphatase in rat liver microsomes in a concentration-dependent manner that could explain the decrease in glucose-6-phosphate hydrolysis seen in intact cells.
The inhibitory effect of silibinin on both hepatic glucose-6-phosphatase and gluconeogenesis suggests that its use may be interesting in treatment of type 2 diabetes.
Cellular Physiology and Biochemistry 02/2007; 20(6):925-34. · 2.86 Impact Factor
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ABSTRACT: MOCP (maternal obstructive cholestasis during pregnancy) induces a reversible impairment in bile formation in young rats born to these mothers. The aim of the present study was to gain information on the effects of MOCP on the maturation of pathways involved in protein secretion into bile in young (4-week-old) rats. The amount of hepatic alpha-tubulin and the structure of the microtubular network were apparently not affected by MOCP. HRP (horseradish peroxidase) was used as a model protein, and its secretion into bile after administration through the jugular vein was measured. In adult (8-week-old) rats, two peaks of HRP output into bile were observed following administration: an early peak presumably due to paracellular transfer, and a late peak presumably due to transcytosis. In young rats (4 weeks old), the early peak was similar to that of adult animals, and was not affected by MOCP. However, the late peak was markedly smaller in young control rats, and was further reduced by MOCP. Brefeldin A decreased, whereas taurocholate did not change, the early peak, whereas both affected the transcytotic transport of HRP. Brefeldin A delayed HRP secretion (similarly in control and MOCP groups), without affecting cumulative output, whereas taurocholate accelerated the transcytotic transport of HRP in the control group, but not in the MOCP group. These results suggest that MOCP affects the maturation of hepatocyte mechanisms involved in the transcytotic secretion of HRP into bile.
Clinical Science 10/2003; 105(3):347-53. · 4.61 Impact Factor
