Chronic exposure to glucocorticoid hormones, resulting from either drug treatment or Cushing's syndrome, results in insulin resistance, central obesity, and symptoms similar to the metabolic syndrome. We hypothesized that the major metabolic effects of corticosteroids are mediated by changes in the key metabolic enzyme adenosine monophosphate-activated protein kinase (AMPK) activity. Activation of AMPK is known to stimulate appetite in the hypothalamus and stimulate catabolic processes in the periphery. We assessed AMPK activity and the expression of several metabolic enzymes in the hypothalamus, liver, adipose tissue, and heart of a rat glucocorticoid-excess model as well as in in vitro studies using primary human adipose and primary rat hypothalamic cell cultures, and a human hepatoma cell line treated with dexamethasone and metformin. Glucocorticoid treatment inhibited AMPK activity in rat adipose tissue and heart, while stimulating it in the liver and hypothalamus. Similar data were observed in vitro in the primary adipose and hypothalamic cells and in the liver cell line. Metformin, a known AMPK regulator, prevented the corticosteroid-induced effects on AMPK in human adipocytes and rat hypothalamic neurons. Our data suggest that glucocorticoid-induced changes in AMPK constitute a novel mechanism that could explain the increase in appetite, the deposition of lipids in visceral adipose and hepatic tissue, as well as the cardiac changes that are all characteristic of glucocorticoid excess. Our data suggest that metformin treatment could be effective in preventing the metabolic complications of chronic glucocorticoid excess.

BackgroundThe process of neurite outgrowth is the initial step in producing the neuronal processes that wire the brain. Current models about neurite outgrowth have been derived from classic two-dimensional (2D) cell culture systems, which do not recapitulate the topographical cues that are present in the extracellular matrix (ECM) in vivo. Here, we explore how ECM nanotopography influences neurite outgrowth.Methodology/Principal FindingsWe show that, when the ECM protein laminin is presented on a line pattern with nanometric size features, it leads to orientation of neurite outgrowth along the line pattern. This is also coupled with a robust increase in neurite length. The sensing mechanism that allows neurite orientation occurs through a highly stereotypical growth cone behavior involving two filopodia populations. Non-aligned filopodia on the distal part of the growth cone scan the pattern in a lateral back and forth motion and are highly unstable. Filopodia at the growth cone tip align with the line substrate, are stabilized by an F-actin rich cytoskeleton and enable steady neurite extension. This stabilization event most likely occurs by integration of signals emanating from non-aligned and aligned filopodia which sense different extent of adhesion surface on the line pattern. In contrast, on the 2D substrate only unstable filopodia are observed at the growth cone, leading to frequent neurite collapse events and less efficient outgrowth.Conclusions/SignificanceWe propose that a constant crosstalk between both filopodia populations allows stochastic sensing of nanotopographical ECM cues, leading to oriented and steady neurite outgrowth. Our work provides insight in how neuronal growth cones can sense geometric ECM cues. This has not been accessible previously using routine 2D culture systems.

Growth cone localization of MKK7 mRNA switches the classic function of MKK7 protein in transcriptional control to regulation of microtubules necessary for neuronal outgrowth.

Highlights► Ghrelin requires GHS-R1a for its effect on hypothalamic, liver and adipose tissue AMPK activity. ► An intact ghrelin signalling pathway is required for the effects of cannabinoids on AMPK activity. ► Ghrelin and cannabinoids stimulate hypothalamic but inhibit liver and visceral fat AMPK. ► Treatment with HU210 at 20 ng/g significantly inhibited inguinal fat AMPK activity. ► We report the loss of inhibitory effects of ghrelin on liver AMPK activity in GHS-R1a KO mice.

Although some evidence supports the antitumoral effects of somatostatin (SRIF) and related agonists, the available data in prostate cancer (PCa) model systems and clinical studies are few, conflicting and not conclusive. This study investigated the effects of lanreotide and new mono-and bi-specific SRIF agonists on proliferation, ligand-driven SRIF receptor (sst) dimerization and secretory pattern of the IGF system in LNCaP cells, a model of androgendependent PCa. LNCaP expressed all sst s , but sst 4. Among them, sst 1 and sst 3 were inversely regulated by serum concentration. Sst 1 /sst 2 and sst 2 /sst 5 dimers were constitutively present and further stabilized by treatment with BIM-23704 (sst 1 /sst 2) and BIM-23244 (sst 2 /sst 5), respectively. Dose-response studies showed that lanreotide and BIM-23244 were significantly more potent in inhibiting LNCaP cell proliferation than BIM-23120 (sst 2) and BIM-23206 (sst 5) alone or in combination. Treatment with BIM-23296 (sst 1) markedly reduced cell proliferation, whereas exposure to BIM-23704 resulted in a lower cell growth inhibition. The antiproliferative effects of BIM-23244, lanreotide and BIM-23704 were unchanged, reduced and abolished by the sst 2 antagonist BIM-23627, respectively. All SRIF analogs caused a significant induction in p27 KipI and p21 and down-regulation of protein expression of cyclin E, as well as reduced IGF-I and IGF-II secretion. In particular, the administration of exogenous IGF-I, at variance to IGF-II, counteracted the inhibitory effect on cell proliferation of these compounds. Moreover, SRIF agonists reduced endogenous IGFBP-3 proteolysis. These results show that, in LNCaP cells, activation of sst 1 and sst 2 /sst 5 results in relevant antiproliferative/antisecretive actions. INTRODUCTION Somatostatin (SRIF) is an inhibitory tetradecapeptide hormone with exocrine, endocrine, paracrine, and autocrine activities, which plays an important regulatory role in several cell functions, including inhibition of endocrine secretion and cell proliferation (Hejna et al., 2002; Tejeda et al., 2006). Most of the effects of SRIF and of its currently available analogs are mediated via five different G protein-coupled receptor (GPCRs), codenamed sst 1-5 (Patel 1999). Sst s are expressed in a tissue-and subtype-selective manner in both normal and neoplastic cells, and the majority of SRIF target tissues express multiple sst s (Reubi et al., 2001). Recent data suggest that when sst s are coexpressed may interact forming homo-and hetero-dimers also with other GPCRs, altering their original pharmacological and functional profiles (Krantic et al., 2004). Prostate cancer (PCa) is the most frequently diagnosed malignant neoplasm among men in the Western world and remains the second leading cause of cancer-related deaths, with an incidence estimated at 12% in the European Union and at 29% in the USA (Djavan 2007). In addition to the traditional anti-androgen hormonal therapy, commonly used in androgendependent PCa, some evidence suggest SRIF receptors as a ta...