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Alain Géloën

Publications and source records attributed to Alain Géloën.

5 recordsLinked to original sources
PubMed2005

Lipolytic activity of cirsimarin extracted from Microtea debilis.

This study explores the ability of cirsimarin, a plant flavonoid, to trigger lipid mobilization. Cirsimarin was extracted from Microtea debilis Swartz (Phytolaccaceae) and purified by preparative HPLC. Its lipolytic activity was assessed on isolated adipocytes from rats and compared to that of caffeine, a well known lipolytic agent. The results show an EC (50) = 0.025 +/- 0.01 mM for cirsimarin (n = 4) and of 0.49 +/- 0.08 mM for caffeine (n = 4). Furthermore, we show that cirsimarin inhibits phosphodiesterase, the enzyme that modulates cyclic nucleotide signalling. In conclusion, our results demonstrate that cirsimarin exerts strong lipolytic properties being 20 times more potent than caffeine to stimulate lipolysis, at least in part through cyclic nucleotide preservation.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2003

Sympathetic and brain monoaminergic regulation of energy balance in obesity-resistant rats (Lou/C).

In contrast to the Wistar rat, the Lou/C rat does not develop obesity with age. To determine the role of sympathetic output and brain monoamines in the different energy balance of Lou/C rats, the monoamine contents and activity of rate-limiting enzymes in catecholamine and serotonin biosynthesis were assessed in brain structures involved in energy balance regulation, i.e., brainstem noradrenergic (A6, A5, A2) and serotonergic cell groups (dorsal raphe, and median raphe), and two hypothalamic nuclei (ventromedial nucleus and paraventricular nucleus). In vivo tyrosine hydroxylase activity and noradrenaline content were measured in sympathetic target organs storing fuel substrates, the liver, white adipose and brown adipose tissues in the Lou/C rat and compared to the Wistar rat. In Lou/C rats, indirect calorimetric measurements showed a higher energy expenditure despite a reduced food intake. The Lou/C rat displayed selective monoamine features. The catecholaminergic activity was higher in the white adipose tissue and interscapular brown adipose tissue but lower in the liver and adrenal gland of Lou/C rats. The noradrenergic activity in A2, A6 and ventromedial nucleus, and the serotonergic pattern in A6, dorsal raphe and median raphe were lower in Lou/C. The metabolic particularities of Lou/C rats are associated with (i) a selectively enhanced sympathetic activity restricted to the white adipose tissue and brown adipose tissue, (ii) a reduced noradrenergic activity in selective brainstem and hypothalamic areas, which control the energy expenditure and food intake.

Adipose Tissue↗
PubMed2003

Fibroblast cells: a sensing bioelement for glucose detection by impedance spectroscopy.

Modifying the electrical properties of fibroblasts against various glucose concentrations can serve as a basis for a new, original sensing device. The aim of the present study is to test a new biosensor based on impedancemetry measurement using eukaryote cells. Fibroblast cells were grown on a small optically transparent indium tin oxide semiconductor electrode. Electrochemical impedance spectroscopy (EIS) was used to measure the effect of D-glucose on the electrical properties of fibroblast cells. Further analyses of the EIS results were performed using equivalent circuits in order to model the electrical flow through the interface. The linear calibration curve was established in the range 0-14 mM. The specification of the biosensors was verified using cytochalasin B as an inhibitor agent of the glucose transporters. The nonreactivity to sugars other than glucose was demonstrated. Such a biosensor could be applied to a more fundamental study of cell metabolism.

3T3 Cells↗
PubMed2002

IGF-1 receptor regulates lifespan and resistance to oxidative stress in mice.

Studies in invertebrates have led to the identification of a number of genes that regulate lifespan, some of which encode components of the insulin or insulin-like signalling pathways. Examples include the related tyrosine kinase receptors InR (Drosophila melanogaster) and DAF-2 (Caenorhabditis elegans) that are homologues of the mammalian insulin-like growth factor type 1 receptor (IGF-1R). To investigate whether IGF-1R also controls longevity in mammals, we inactivated the IGF-1R gene in mice (Igf1r). Here, using heterozygous knockout mice because null mutants are not viable, we report that Igf1r(+/-) mice live on average 26% longer than their wild-type littermates (P < 0.02). Female Igf1r(+/-) mice live 33% longer than wild-type females (P < 0.001), whereas the equivalent male mice show an increase in lifespan of 16%, which is not statistically significant. Long-lived Igf1r(+/-) mice do not develop dwarfism, their energy metabolism is normal, and their nutrient uptake, physical activity, fertility and reproduction are unaffected. The Igf1r(+/-) mice display greater resistance to oxidative stress, a known determinant of ageing. These results indicate that the IGF-1 receptor may be a central regulator of mammalian lifespan.

Aging↗