Explore the vast range of titles available.

Cachexia is a wasting syndrome associated with cancer, AIDS, multiple sclerosis, and several other disease states. It is characterized by weight loss, fatigue, loss of appetite, and skeletal muscle atrophy and is associated with poor patient prognosis, making it an important treatment target. Ghrelin is a peptide hormone that stimulates growth hormone (GH) release and positive energy balance through binding to the receptor GHSR-1a. Only acylated ghrelin (AG), but not the unacylated form (UnAG), can bind GHSR-1a; however, UnAG and AG share several GHSR-1a-independent biological activities. Here we investigated whether UnAG and AG could protect against skeletal muscle atrophy in a GHSR-1a-independent manner. We found that both AG and UnAG inhibited dexamethasone-induced skeletal muscle atrophy and atrogene expression through PI3Kβ-, mTORC2-, and p38-mediated pathways in myotubes. Upregulation of circulating UnAG in mice impaired skeletal muscle atrophy induced by either fasting or denervation without stimulating muscle hypertrophy and GHSR-1a-mediated activation of the GH/IGF-1 axis. In Ghsr-deficient mice, both AG and UnAG induced phosphorylation of Akt in skeletal muscle and impaired fasting-induced atrophy. These results demonstrate that AG and UnAG act on a common, unidentified receptor to block skeletal muscle atrophy in a GH-independent manner.

Dietary advanced glycation end-products (dAGEs) contained in high-sugar/fat and ultra-processed foods of the “Western diet” (WD) pattern predispose to several diseases by altering protein function or increasing oxidative stress and inflammation via RAGE (receptor for advanced glycation end-products). Although elevated endogenous AGEs are associated with loss of muscle mass and functionality (i.e., muscle wasting; MW), the impact of dAGEs on MW has not been elucidated. Here, we show that the most common dAGEs or their precursor, methylglyoxal (MGO), induce C2C12 myotube atrophy as endogenous AGE-derived BSA. ROS production, mitochondrial dysfunction, mitophagy, ubiquitin–proteasome activation, and inhibition of myogenic potential are common atrophying mechanisms used by MGO and AGE-BSA. Although of different origins, ROS are mainly responsible for AGE-induced myotube atrophy. However, while AGE-BSA activates the RAGE-myogenin axis, reduces anabolic mTOR, and causes mitochondrial damage, MGO induces glycolytic stress and STAT3 activation without affecting RAGE expression. Among thirty selected natural compounds, Vaccinium macrocarpon (VM), Camellia sinensis, and chlorophyll showed a surprising ability in counteracting in vitro AGE formation. However, only the standardized VM, containing anti-glycative metabolites as revealed by UHPLC-HRMS analysis, abrogates AGE-induced myotube atrophy. Collectively, our data suggest that WD-linked dAGE consumption predisposes to MW, which might be restricted by VM food supplements.

Metabolic dysfunction-associated steatohepatitis (MASH) represents a growing cause of liver cirrhosis and hepatocellular carcinoma (HCC). However, effective therapy for MASH is still lacking. Despite recent studies suggest that ketosis might improve MASH evolution, the mechanisms involved have not been explored since common ketogenic diets cause severe steatohepatitis in mice. In this study, we have investigated the capacity of a new-formulated ketogenic diet (KD) containing vegetal fat in improving liver alterations associated with experimental MASH. MASH was induced in C57BL/6 mice by feeding a cholesterol-enriched Western Diet (WD) for up to 16 weeks, followed by switching animals to KD for an additional eight weeks. We observed that KD administration greatly increased ketone body production and significantly reduced liver and body weights. Moreover, liver proteomic analysis and functional tests evidenced an improved glucose and lipid metabolism along with insulin resistance in KD-fed mice. These metabolic effects were associated with an amelioration in MASH-associated gut dysbiosis and with an improvement of hepatic steatosis, parenchymal injury and liver fibrosis. From the mechanistic point of view mice receiving KD showed a significant reduction in liver TREM2-positive monocyte-derived macrophages forming crown-like aggregates along with a lowering in the hepatic expression of pro-inflammatory/pro-fibrogenic markers such as CCL2, IL-12, CD11b, α1-procollagen, TGF-β1, osteopontin, and galectin-3. Consistently, experiments showed that β-hydroxybutyrate supplementation reduced TREM2 and galectin-3 expression by cultured Raw 264.7 macrophages. Altogether, these results indicate that ketogenic diet based on vegetal fat effectively improves MASH metabolic derangements and steatohepatitis, and it might represent a potential therapeutic strategy in this disease.

IP 3 receptor (IP 3 R)-mediated Ca 2+ transfer at the mitochondria-endoplasmic reticulum (ER) contact sites (MERCS) drives mitochondrial Ca 2+ uptake and oxidative metabolism and is linked to different pathologies, including Parkinson’s disease (PD). The dependence of Ca 2+ transfer efficiency on the ER-mitochondria distance remains unexplored. Employing molecular rulers that stabilize ER-mitochondrial distances at 5 nm resolution, and using genetically encoded Ca 2+ indicators targeting the ER lumen and the sub-mitochondrial compartments, we now show that a distance of ~20 nm is optimal for Ca 2+ transfer and mitochondrial oxidative metabolism due to enrichment of IP 3 R at MERCS. In human iPSC-derived astrocytes from PD patients, 20 nm MERCS were specifically reduced, which correlated with a reduction of mitochondrial Ca 2+ uptake. Stabilization of the ER-mitochondrial interaction at 20 nm, but not at 10 nm, fully rescued mitochondrial Ca 2+ uptake in PD astrocytes. Our work determines with precision the optimal distance for Ca 2+ flux between ER and mitochondria and suggests a new paradigm for fine control over mitochondrial function. The distance-dependence analysis of ER-mitochondria Ca 2+ transfer suggests that a distance of ∼20 nm between the organelles ensures maximal efficiency of mitochondrial Ca 2+ uptake and OXPHOS and rescues Ca 2+ uptake in Parkinson’s disease mitochondria.

A major obstacle to an effective myocardium stem cell therapy has always been the delivery and survival of implanted stem cells in the heart. Better engraftment can be achieved if cells are administered as cell aggregates, which maintain their extra-cellular matrix (ECM). We have generated spheroid aggregates in less than 24 h by seeding human cardiac progenitor cells (hCPCs) onto methylcellulose hydrogel-coated microwells. Cells within spheroids maintained the expression of stemness/mesenchymal and ECM markers, growth factors and their cognate receptors, cardiac commitment factors, and metalloproteases, as detected by immunofluorescence, q-RT-PCR and immunoarray, and expressed a higher, but regulated, telomerase activity. Compared to cells in monolayers, 3D spheroids secreted also bFGF and showed MMP2 activity. When spheroids were seeded on culture plates, the cells quickly migrated, displaying an increased wound healing ability with or without pharmacological modulation, and reached confluence at a higher rate than cells from conventional monolayers. When spheroids were injected in the heart wall of healthy mice, some cells migrated from the spheroids, engrafted, and remained detectable for at least 1 week after transplantation, while, when the same amount of cells was injected as suspension, no cells were detectable three days after injection. Cells from spheroids displayed the same engraftment capability when they were injected in cardiotoxin-injured myocardium. Our study shows that spherical in vivo ready-to-implant scaffold-less aggregates of hCPCs able to engraft also in the hostile environment of an injured myocardium can be produced with an economic, easy and fast protocol.

Dysfunctional mitochondrial metabolism has been linked to skeletal muscle loss in several physio-pathological states. Although it has been reported that vitamin D (VD) supports cellular redox homeostasis by maintaining normal mitochondrial functions, and VD deficiency often occurs in conditions associated with skeletal muscle loss, the efficacy of VD supplementation to overcome muscle wasting is debated. Investigations on the direct effects of VD metabolites on skeletal muscle using C2C12 myotubes have revealed an unexpected pro-atrophic activity of calcitriol (1,25VD), while its upstream metabolites cholecalciferol (VD3) and calcidiol (25VD) have anti-atrophic effects. Here, we investigated if the atrophic effects of 1,25VD on myotubes depend on its activity on mitochondrial metabolism. The impact of 1,25VD and its upstream metabolites VD3 and 25VD on mitochondria dynamics and the activity of C2C12 myotubes was evaluated by measuring mitochondrial content, architecture, metabolism, and reactive oxygen species (ROS) production. We found that 1,25VD induces atrophy through protein kinase C (PKC)-mediated ROS production, mainly of extramitochondrial origin. Consistent with this, cotreatment with the antioxidant N-acetylcysteine (NAC), but not with the mitochondria-specific antioxidant mitoTEMPO, was sufficient to blunt the atrophic activity of 1,25VD. In contrast, VD3 and 25VD have antioxidant properties, suggesting that the efficacy of VD supplementation might result from the balance between atrophic pro-oxidant (1,25VD) and protective antioxidant (VD3 and 25VD) metabolites.

STIM and ORAI proteins play a fundamental role in calcium signaling, allowing for calcium influx through the plasma membrane upon depletion of intracellular stores, in a process known as store-operated Ca2+ entry. Point mutations that lead to gain-of-function activity of either STIM1 or ORAI1 are responsible for a cluster of ultra-rare syndromes characterized by motor disturbances and platelet dysfunction. The prevalence of these disorders is at present unknown. In this study, we describe the generation and characterization of a knock-in mouse model (KI-STIM1I115F) that bears a clinically relevant mutation located in one of the two calcium-sensing EF-hand motifs of STIM1. The mouse colony is viable and fertile. Myotubes from these mice show an increased store-operated Ca2+ entry, as predicted. This most likely causes the dystrophic muscle phenotype observed, which worsens with age. Such histological features are not accompanied by a significant increase in creatine kinase. However, animals have significantly worse performance in rotarod and treadmill tests, showing increased susceptibility to fatigue, in analogy to the human disease. The mice also show increased bleeding time and thrombocytopenia, as well as an unexpected defect in the myeloid lineage and in natural killer cells. The present model, together with recently described models bearing the R304W mutation (located on the coiled-coil domain in the cytosolic side of STIM1), represents an ideal platform to characterize the disorder and test therapeutic strategies for patients with STIM1 mutations, currently without therapeutic solutions. This article has an associated First Person interview with Celia Cordero-Sanchez, co-first author of the paper.

Ghrelin is a circulating peptide hormone released by enteroendocrine cells of the gastrointestinal tract as two forms, acylated and unacylated. Acylated ghrelin (AG) binds to the growth hormone secretagogue receptor 1a (GHSR1a), thus stimulating food intake, growth hormone release, and gastrointestinal motility. Conversely, unacylated GHR (UnAG), through binding to a yet unidentified receptor, protects the skeletal muscle from atrophy, stimulates muscle regeneration, and protects cardiomyocytes from ischemic damage. Recently, interest about ghrelin has raised also among neuroscientists because of its effect on the nervous system, especially the stimulation of neurogenesis in spinal cord, brain stem, and hippocampus. However, few information is still available about its effectiveness on peripheral nerve regeneration. To partially fill this gap, the aim of this study was to assess the effect of UnAG on peripheral nerve regeneration after median nerve crush injury and after nerve transection immediately repaired by means of an end-to-end suture. To this end, we exploited FVB1 Myh6/Ghrl transgenic mice in which overexpression of the ghrelin gene (Ghrl) results in selective up-regulation of circulating UnAG levels, but not of AG. Regeneration was assessed by both functional evaluation (grasping test) and morphometrical analysis of regenerated myelinated axons. Results obtained lead to conclude that UnAG could have a role in development of peripheral nerves and during more severe lesions.

Pharmacological treatments for advanced hepatocellular carcinoma (HCC) have a partial efficacy. Augmented Na + content and water retention are observed in human cancers and offer unexplored targets for anticancer therapies. Na + levels are evaluated upon treatments with the antibiotic cation ionophore Monensin by fluorimetry, ICP-MS, 23 Na-MRI, NMR relaxometry, confocal or time-lapse analysis related to energy production, water fluxes and cell death, employing both murine and human HCC cell lines, primary murine hepatocytes, or HCC allografts in NSG mice. Na + levels of HCC cells and tissue are 8-10 times higher than that of healthy hepatocytes and livers. Monensin further increases Na + levels in HCC cells and in HCC allografts but not in primary hepatocytes and in normal hepatic and extrahepatic tissue. The Na + increase is associated with energy depletion, mitochondrial Na + load and inhibition of O 2 consumption. The Na + increase causes an enhancement of the intracellular water lifetime and death of HCC cells, and a regression and necrosis of allograft tumors, without affecting the proliferating activity of either HCCs or healthy tissues. These observations indicate that HCC cells are, unlike healthy cells, energetically incapable of compensating and surviving a pharmacologically induced Na + load, highlighting Na + homeostasis as druggable target for HCC therapy. The ionophore monensin is shown to have cancer-selective cytotoxic action by selectively increasing the sodium content in cultured hepatocellular carcinoma cells (HCC) and allografts, highlighting the sensitivity of HCC cells to pharmacologically induced Na+ load.

Fibrosis can affect almost all tissues and organs, it often represents the terminal stage of chronic diseases, and it is regarded as a major health issue for which efficient therapies are needed. Tissue injury, by inducing necrosis/apoptosis, triggers inflammatory response that, in turn, promotes fibroblast activation and pathological deposition of extracellular matrix. Acylated and unacylated ghrelin are the main products of the ghrelin gene. The acylated form, through its receptor GHSR-1a, stimulates appetite and growth hormone (GH) release. Although unacylated ghrelin does not bind or activate GHSR-1a, it shares with the acylated form several biological activities. Ghrelin peptides exhibit anti-inflammatory, antioxidative, and antiapoptotic activities, suggesting that they might represent an efficient approach to prevent or reduce fibrosis. The aim of this review is to summarize the available evidence regarding the effects of acylated and unacylated ghrelin on different pathologies and experimental models in which fibrosis is a predominant characteristic.