Glucosensing neurons in the ventromedial hypothalamic nucleus (VMN) were studied using visually guided slicepatch recording techniques in brain slices from 14-to 21-day-old male Sprague-Dawley rats. Whole-cell current-clamp recordings were made as extracellular glucose levels were increased (from 2.5 to 5 or 10 mmol/l) or decreased (from 2.5 to 0.1 mmol/l). Using these physiological conditions to define glucosensing neurons, two subtypes of VMN glucosensing neurons were directly responsive to alterations in extracellular glucose levels. Another three subtypes were not directly glucose-sensing themselves, but rather were presynaptically modulated by changes in extracellular glucose. Of the VMN neurons, 14% were directly inhibited by decreases in extracellular glucose (glucose-excited [GE]), and 3% were directly excited by decreases in extracellular glucose (glucose-inhibited [GI]). An additional 14% were presynaptically excited by decreased glucose (PED neurons). The other two subtypes of glucosensing neurons were either presynaptically inhibited (PIR; 11%) or excited (PER; 8%) when extracellular glucose was raised to >2.5 mmol/l. GE neurons sensed decreased glucose via an ATP-sensitive K ؉ (K ATP ) channel. The inhibitory effect of increased glucose on PIR neurons appears to be mediated by a presynaptic ␥-aminobutyric acid-ergic glucosensing neuron that probably originates outside the VMN. Finally, all types of glucosensing neurons were both fewer in number and showed abnormal responses to glucose in a rodent model of diet-induced obesity and type 2 diabetes.

Mesenchymal stem cells (MSCs) exhibit immune-suppressive properties, follow a pattern of multilineage differentiation, and exhibit transdifferentiation potential. Ease in expansion from adult bone marrow, as well as its separation from ethical issues, makes MSCs appealing for clinical application. MSCs treated with retinoic acid resulted in synaptic transmission, based on immunostaining of synaptophysin and electrophysiological studies. In situ hybridization indicated that the neurotransmitter gene preprotachykinin-I was expressed in these cells. However, translation of this gene only occurred after stimulation with interleukin (IL)-1α. This effect was blunted by costimulation with IL-1 receptor antagonist. This study reports on the ability of MSCs to be transdifferentiated into neurons with functional synapses with the potential to become polarized towards producing specific neurotransmitters. Stem Cells 2005;23:383-391

Sarcolipin (SLN) is an inhibitor of the sarco/endoplasmic reticulum (SR) Ca2+ ATPase (SERCA) and is abnormally elevated in the muscle of Duchenne muscular dystrophy (DMD) patients and animal models. Here we show that reducing SLN levels ameliorates dystrophic pathology in the severe dystrophin/utrophin double mutant (mdx:utr −/−) mouse model of DMD. Germline inactivation of one allele of the SLN gene normalizes SLN expression, restores SERCA function, mitigates skeletal muscle and cardiac pathology, improves muscle regeneration, and extends the lifespan. To translate our findings into a therapeutic strategy, we knock down SLN expression in 1-month old mdx:utr −/− mice via adeno-associated virus (AAV) 9-mediated RNA interference. The AAV treatment markedly reduces SLN expression, attenuates muscle pathology and improves diaphragm, skeletal muscle and cardiac function. Taken together, our findings suggest that SLN reduction is a promising therapeutic approach for DMD.

Canabal DD, Song Z, Potian JG, Beuve A, McArdle JJ, Routh VH. Glucose, insulin and leptin signaling pathways modulate nitric oxide synthesis in glucose-inhibited neurons in the ventromedial hypothalamus. Am J Physiol Regul Integr Comp Physiol 292: R1418 -R1428, 2007. First published December 24, 2006; doi:10.1152/ajpregu.00216.2006.-Glucose-sensing neurons in the ventromedial hypothalamus (VMH) are involved in the regulation of glucose homeostasis. Glucosesensing neurons alter their action potential frequency in response to physiological changes in extracellular glucose, insulin, and leptin. Glucose-excited neurons decrease, whereas glucose-inhibited (GI) neurons increase, their action potential frequency when extracellular glucose is reduced. Central nitric oxide (NO) synthesis is regulated by changes in local fuel availability, as well as insulin and leptin. NO is involved in the regulation of food intake and is altered in obesity and diabetes. Thus this study tests the hypothesis that NO synthesis is a site of convergence for glucose, leptin, and insulin signaling in VMH glucose-sensing neurons. With the use of the NO-sensitive dye 4-amino-5-methylamino-2Ј,7Ј-difluorofluorescein in conjunction with the membrane potential-sensitive dye fluorometric imaging plate reader, we found that glucose and leptin suppress, whereas insulin stimulates neuronal nitric oxide synthase (nNOS)-dependent NO production in cultured VMH GI neurons. The effects of glucose and leptin were mediated by suppression of AMP-activated protein kinase (AMPK). The AMPK activator 5-aminoimidazole-4-carboxamide-1-␤-4-ribofuranoside (AICAR) increased both NO production and neuronal activity in GI neurons. In contrast, the effects of insulin on NO production were blocked by the phosphoinositide 3-kinase inhibitors wortmannin and LY-294002. Furthermore, decreased glucose, insulin, and AICAR increase the phosphorylation of VMH nNOS, whereas leptin decreases it. Finally, VMH neurons express soluble guanylyl cyclase, a downstream mediator of NO signaling. Thus NO may mediate, in part, glucose, leptin, and insulin signaling in VMH glucose-sensing neurons. ventromedial hypothalamus; glucose-sensing neurons; leptin; insulin; nitric oxide; adenosine 5Ј-monophosphate-activated protein kinase THE VENTROMEDIAL HYPOTHALAMUS (VMH), which contains the ventromedial (VMN) and arcuate (ARC) nuclei, is critical for the regulation of glucose and energy homeostasis (34). This region contains specialized neurons whose activity is regulated by physiologically relevant changes in extracellular glucose (36,37,42). Glucose-excited (GE) neurons decrease, whereas glucose-inhibited (GI) neurons increase, their action potential frequency (APF) when extracellular glucose is reduced (36). GE neurons activate ATP-sensitive K ϩ (K ATP ) channels in response to decreased glucose. GI neurons appear to close an ATP-activated Cl Ϫ channel, although the identity of this channel is unknown (36). Glucose-sensing neurons also possess insulin and leptin receptors (22,39,40,42). Thus gluc...

Ahstr0rc.r: 2,3-Butanedione monoxime. also known as diacetyl monoxime, is a nucleophilic agent which dephosphorylates iicetylcholinesterase poisoned with organophosphates. This "chemical phosphatase" activity stimulated studies of the effect of 2.3-butanedione monoxime on phosphorylation-dependent cellular processes. As a result of these studies, we know that the drug affects a number of mechanisms including muscle contraction, ionic current flow and synaptic transmission. Furthermore. it may he used as a component of cardioplegic solutions since it protects cardiac tissue exposed to certain ischaemic conditions. While this MiniRewiev reveals the diversity of its cellular actions. there continues LO be unresolved questions regarding its molecular mechanism.