Constitutive glycogen synthase kinase-3α/β activity protects against chronic β-adrenergic remodelling of the heart

Aims - Glycogen synthase kinase 3 (GSK-3) signalling is implicated in the growth of the heart during development and in response to stress. However, its precise role remains unclear. We set out to characterize developmental growth and response to chronic isoproterenol (ISO) stress in knockin (KI) mice lacking the critical N-terminal serines, 21 of GSK-3 and 9 of GSK-3 respectively, required for inactivation by upstream kinases. Methods and results - Between 5 and 15 weeks, KI mice grew more rapidly, but normalized heart weight and contractile performance were similar to wild-type (WT) mice. Isolated hearts of both genotypes responded comparably to acute ISO infusion with increases in heart rate and contractility. In WT mice, chronic subcutaneous ISO infusion over 14 days resulted in cardiac hypertrophy, interstitial fibrosis, and impaired contractility, accompanied by foetal gene reactivation. These effects were all significantly attenuated in KI mice. Indeed, ISO-treated KI hearts demonstrated reversible physiological remodelling traits with increased stroke volume and a preserved contractile response to acute adrenergic stimulation. Furthermore, simultaneous pharmacological inhibition of GSK-3 in KI mice treated with chronic subcutaneous ISO recapitulated the adverse remodelling phenotype seen in WT hearts. Conclusion - Expression of inactivation-resistant GSK-3/does not affect eutrophic myocardial growth but protects against pathological hypertrophy induced by chronic adrenergic stimulation, maintaining cardiac function and attenuating interstitial fibrosis. Accordingly, strategies to prevent phosphorylation of Ser-21/9, and consequent inactivation of GSK-3/, may enable a sustained cardiac response to chronic-agonist stimulation while preventing pathological remodelling. © 2010 The Author.

Functional astrocyte-neuron lactate shuttle in a human stem cell-derived neuronal network

The NT2.D1 cell line is one of the most well-documented embryocarcinoma cell lines, and can be differentiated into neurons and astrocytes. Great focus has also been placed on defining the electrophysiological properties of the neuronal cells, and more recently we have investigated the functional properties of their associated astrocytes. We now show for the first time that human stem cell-derived astrocytes produce glycogen and that co-cultures of these cells demonstrate a functional astrocyte-neuron lactate shuttle (ANLS). The ANLS hypothesis proposes that during neuronal activity, glutamate released into the synaptic cleft is taken up by astrocytes and triggers glucose uptake, which is converted into lactate and released via monocarboxylate transporters for neuronal use. Using mixed cultures of NT2-derived neurons and astrocytes, we have shown that these cells modulate their glucose uptake in response to glutamate. Additionally, we demonstrate that in response to increased neuronal activity and under hypoglycaemic conditions, co-cultures modulate glycogen turnover and increase lactate production. Similar results were also shown after treatment with glutamate, potassium, isoproterenol, and dbcAMP. Together, these results demonstrate for the first time a functional ANLS in a human stem cell-derived co-culture. © 2013 ISCBFM.

Functional astrocyte-neuron lactate shuttle in a human stem cell derived neuronal network

The development of stem cell-derived neuronal networks will promote experimental system development for drug screening, toxicological testing and disease modelling, providing that they mirror closely the functional competencies of their in vivo counterparts. The NT2 cell line is one of the best documented embryocarcinoma cell lines, and can be differentiated into neurons and astrocytes. Great focus has also been placed on defining the electrophysiological properties of these cells, and more recently we have investigated the functional properties of their associated astrocytes. We now show for the first time in a human stem cell derived co-culture model that these cultures are also metabolically competent and demonstrate a functional astrocyte neuron lactate shuttle (ANLS). The ANLS hypothesis proposes that during neuronal activity, glutamate released into the synaptic cleft is taken up by astrocytes and triggers glucose uptake which is converted into lactate and released via monocarboxylate transporters for neuronal use. Using mixed cultures of NT2 derived neurons and astrocytes we have shown that these cells modulate their glucose uptake in response to glutamate, an effect that was blocked by cytochalasin B and ouabain. Additionally we demonstrate that in response to increased neuronal activity and under hypoglycaemic conditions, co-cultures modulate glycogen turnover and increase lactate production. Similar results were also shown following treatment with glutamate, potassium, Isoproterenol and dbcAMP. Together these results demonstrate for the first time a functional ANLS in a human stem cell derived co-culture.

Relations entre la lipolyse adipocytaire, la périlipine et l'obésité dans une perspective de physiopathologie telle le diabète de type II

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Relations entre la lipolyse adipocytaire, la périlipine et l'obésité dans une perspective de physiopathologie telle le diabète de type II

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.