Glucose regulates AMP-activated protein kinase activity and gene expression in clonal, hypothalamic neurons expressing proopiomelanocortin: additive effects of leptin or insulin

Abstract

The mammalian hypothalamus comprises an array of phenotypically distinct cell types that interpret peripheral signals of energy status and, in turn, elicits an appropriate response to maintain energy homeostasis. We used a clonal representative hypothalamic cell model expressing proopiomelanocortin (POMC; N-43/5) to study changes in AMPactivated protein kinase (AMPK) activity and glucose responsiveness. We have demonstrated the presence of cellular machinery responsible for glucose sensing in the cell line, including glucokinase, glucose transporters, and appropriate ion channels. ATP-sensitive potassium channels were functional and responded to glucose. The N-43/5 POMC neurons may therefore be an appropriate cell model to study glucose-sensing mechanisms in the hypothalamus. In N-43/5 POMC neurons, increasing glucose concentrations decreased phospho-AMPK activity. As a relevant downstream effect, we found that POMC transcription increased with 2 . 8 and 16 . 7 mM glucose. Upon addition of leptin, with either no glucose or with 5 mM glucose, we found that leptin decreased AMPK activity in N-43/5 POMC neurons, but had no significant effect at 25 mM glucose, whereas insulin decreased AMPK activity at only 5 mM glucose. These results demonstrate that individual hypothalamic neuronal cell types, such as the POMC neuron, can have distinct responses to peripheral signals that relay energy status to the brain, and will therefore be activated uniquely to control neuroendocrine function.

ERK1/2 mediates glucose-regulated POMC gene expression in hypothalamic neurons

“…2). The regulatory effect of glucose on the orexigenic and anorexigenic neuropeptide expression in DIV10 neurons agrees with the results reported previously (Chang et al 2005, Lee et al 2005, Cai et al 2007, Wolfgang et al 2007, Cha et al 2008, Cheng et al 2008.…”

“…administration of glucose stimulates POMC and inhibits AgRP/NPY expression (Chang et al 2005, Wolfgang et al 2007, Cha et al 2008. Glucose-regulated AgRP or POMC expression has also been demonstrated in transformed cell lines (Lee et al 2005, Cai et al 2007, Cheng et al 2008. Because the glucose-regulated gene expression can be blunted by the non-metabolizable glucose analogue 2-deoxyglucose in vivo as well as in cell lines (Lee et al 2005, Wolfgang et al 2007, Cha et al 2008, Cheng et al 2008, the results indicate that intracellular glucose metabolism is required for the expression of these genes.…”

Effect of different glycaemic conditions on gene expression of neuropeptides involved in control of food intake in rainbow trout; interaction with stress

“…Again, there have been no similar studies carried out in fish to date. In mammals, an increase in circulating glucose levels is known to produce increased POMC expression in the hypothalamus (Lynch et al, 2000;Mobbs et al, 2005;Fekete et al, 2006;Cai et al, 2007;Stolarczyk et al, 2010) in a manner similar to that described in the present study. In fish, POMC is produced in the hypothalamus in Atlantic salmon Salmo salar and goldfish brains (Cerdá-Reverter and Canosa, 2009), and preliminary observations (J.M.C.-R., unpublished data) have also pointed to the expression of POMC in the hindbrain.…”

Cultured hypothalamic neurons are resistant to inflammation and insulin resistance induced by saturated fatty acids

“…Specific neuronal cell lines were selected for this study on the basis of evidence that GT1-7 produce Agouti-related peptide (AgRP) (15), whereas N43/5 express proopiomelanocortin (POMC) (2), and that studies using these cell lines closely mimic various aspects of hypothalamic neuronal physiology (1,19,24), including the capacity for "glucose sensing" (N43/5) (2). Our findings demonstrate that, in these cell lines, saturated fatty acid exposure fails to induce inflammatory responses, unlike what is observed in cultured muscle (C 2 C 12 ) (3) and human microvascular endothelial cells (HMECs) (14).…”