PPARs and Mitochondrial Metabolism: From NAFLD to HCC

Metabolic related diseases, such as type 2 diabetes, metabolic syndrome, and nonalcoholic fatty liver disease (NAFLD), are widespread threats which bring about a significant burden of deaths worldwide, mainly due to cardiovascular events and cancer. The pathogenesis of these diseases is extremely complex, multifactorial, and only partially understood. As the main metabolic organ, the liver is central to maintain whole body energetic homeostasis. At the cellular level, mitochondria are the metabolic hub connecting and integrating all the main biochemical, hormonal, and inflammatory signaling pathways to fulfill the energetic and biosynthetic demand of the cell. In the liver, mitochondria metabolism needs to cope with the energetic regulation of the whole body. The nuclear receptors PPARs orchestrate lipid and glucose metabolism and are involved in a variety of diseases, from metabolic disorders to cancer. In this review, focus is placed on the roles of PPARs in the regulation of liver mitochondrial metabolism in physiology and pathology, from NAFLD to HCC

Molecular biology of Paget’s Disease of Bone: role of p62 and novel genes

Paget’s disease of bone (PDB) is an age-related metabolic bone disease characterized by focal lesions of increased bone resorption and formation, eventually leading to bone deformities. The cause of PDB and the mechanisms that give rise to focal lesions are yet to be understood, but findings suggest that the disease is driven by aberrant, highly nucleated, osteoclasts (OCs). In recent years evidences of a genetic involvement were found: mutations in UBA domain of SQSTM1, which encodes for p62, have been reported in both familial and sporadic cases of PDB (P392L most commonly). Although, their actual pathogenicity has been controversial in experimental studies. Moreover, mutations only involve a part of PDB cases and, although some novel genes have been more recently associated to PDB (e.g.ZNF687), the genetic background of PDB remains in part unknown. In an attempt to establish an experimental model of PDB and better understand p62 role in the disease, we compared two genetically modified murine models, systemic p62 knock-out (p62KO) and mutated p62-P394L (P394L) mice. To further characterize the genetic background of PDB we investigated PDB-associated genes and novel genes in SQSTM1-negative patients. In vitro bone marrow-derived macrophages (BMMs) showed a reduced RANKL-induced osteoclastogenesis (OCgenesis) in p62KO-mice, also seen by TRAP staining on bone sections. BMMs of P394L mice showed a higher sensitivity to RANKL and an increase in OC size and number of nuclei, resembling PDB. Such alterations did not result in a bone phenotype at 6 months of age in either model. However, we found that, with ageing, 47% of P394L mice do develop focal osteolytic lesions. Surprisingly, 78% of p62KO mice developed severe lesions. Although further histological characterization is needed, both animals showed focal, PDB-like, osteolytic/sclerotic features. In vitro analysis of aged p62KO BMMs no longer showed a reduction in OCgenesis potential. Taken together, our findings suggest that p62 mutations in UBA cause a loss of function mechanism in PDB, further exacerbated by total loss of the protein. In support of our hypothesis, proteomics showed that aged p62KO and P394L BMMs are primed for OCgenesis and both present similar expression profiles. Investigating possible molecular mechanisms, we found that UBA-dependent p62 functions of autophagy and NF-κB signalling are not altered in either p62KO and P394L cells. Genetic analysis of 34 patients was performed on genes SQSTM1, TNFRSF11A, VCP, ZNF687 and two variants on TM7SF4 and RIN3. The majority of our cohort was negative for rare mutations on such genes, apart from three cases, carrying TNFRSF11A_M566L, SQSTM1_S275N and ZNF687_P937R. Finally, taking advantage of a large pedigree of a severely affected PDB family we performed Exome NGS to identify novel causal gene. Analysis of impact, familial segregation and allelic frequency identified a novel mutation: PFN1_D107Rfs*3, that causes loss of C-terminal domain of PFN1. This gene encodes for profilin1, a regulator of actin polymerization and cell motility. Given the essential role of cytoskeleton reorganization in OCs biology and the previous findings of bone focal deformities in PFN1 OC-conditional knock-out mice, we started investigating its potential pathogenicity. Silencing of PFN1 in murine BMMs resulted in larger OCs with a higher number of nuclei and increased resorption activity. Screening of PFN1 mutations on other PDB cases is ongoing. Overall, our data demonstrated that both p62 depletion and P394L mutation and are sufficient to cause PDB-like disease in mice. Based on the available molecular data the likely role of p62 in PDB is UBA-dependent but autophagy and NF-κB independent. The genetic background of PDB remains largely unknown, as demonstrated by our screening. Finally, the gene discovery part of the project allowed to identify a likely novel gene for PDB, associated with an early onset and aggressive phenotype

Vescicole extracellulari e metabolismo osseo: ruolo e possibili implicazioni cliniche

Le vescicole extracellulari (EV) sono secrete da vari tipi cellulari e veicolano cargo specifici destinati alle cellule target, mediando così effetti paracrini in meccanismi fisiologici e patologici. Negli ultimi anni lo studio delle EV si è affermato in moltissimi ambiti, compreso il mondo del metabolismo osseo. In questa rassegna riportiamo i più recenti e promettenti studi sul ruolo biologico delle EV nel tessuto osseo e il loro potenziale utilizzo in strategie terapeutiche

The immunity‐malignancy equilibrium in multiple myeloma: lessons from oncogenic events in plasma cells

Multiple myeloma (MM) is a malignancy of plasma cells (PC) that grow within the bone marrow and maintain massive immunoglobulin (Ig) production. Disease evolution is driven by genetic lesions, whose effects on cell biology and fitness underlie addictions and vulnerabilities of myeloma cells. Several genes mutated in myeloma are strictly involved in dictating PC identity and antibody factory function. Here, we evaluate the impact of mutations in IRF4, PRDM1, and XBP1, essential transcription factors driving the B to PC differentiation, on MM cell biology and homeostasis. These factors are highly specialized, with limited overlap in their downstream transcriptional programs. Indeed, IRF4 sustains metabolism, survival, and proliferation, while PRDM1 and XBP1 are mainly responsible for endoplasmic reticulum expansion and sustained Ig secretion. Interestingly, IRF4 undergoes activating mutations and translocations, while PRDM1 and XBP1 are hit by loss‐of‐function events, raising the hypothesis that containment of the secretory program, but not its complete extinction, may be beneficial to malignant PCs. Finally, recent studies unveiled that also the PRDM1 target, FAM46C/TENT5C, an onco‐suppressor uniquely and frequently mutated or deleted in myeloma, is directly and potently involved in orchestrating ER homeostasis and secretory activity. Inactivating mutations found in this gene and its interactors strengthen the notion that reduced secretory capacity confers advantage to myeloma cells. We believe that dissection of the evolutionary pressure on genes driving PC‐specific functions in myeloma will disclose the cellular strategies by which myeloma cells maintain an equilibrium between antibody production and survival, thus unveiling novel therapeutic targets

The Potential Role of miRNAs as New Biomarkers for Osteoporosis

Osteoporosis is the most common metabolic bone disorder affecting up to 40% of postmenopausal women, characterized by a reduction in bone mass and strength leading to bone fragility and fractures. Despite the available tools for diagnosis and stratification of a fracture risk, bone loss occurs insidiously and osteoporosis is often diagnosed after the first fracture has occurred, with important health-related outcomes. Therefore, the need of markers that could efficiently diagnose bone fragility and osteoporosis is still necessary. Over the past few years, novel studies have focused on miRNAs, small noncoding RNAs that are differentially expressed in many pathological conditions, making them attractive biomarkers. To date, the role of miRNAs in bone disorders remains in great part unclear. In particular, limited and partly conflicting information is available concerning their use as potential biomarkers for osteoporosis, due to differences in patient selection, type of samples, and analytical methods. Despite these limits, concordant information about some specific miRNAs is now arising, making likely their use as additional tools to stratify the risk of osteoporosis and possibly fractures. In this review, we summarize the most relevant studies concerning circulating miRNAs differentially expressed in osteoporotic patients along with their function in bone cells and bone turnover

Effetto del trattamento subcronico con benzene in topi C57BL.

Abstarct accettato e incluso nella tavola rotonda "Valutazione del rischi dell'esposizione professionale ed ambientale a benzene: studio dei meccanismi di attivazione e tossicità e degli indicatori di esposizione, effetto e suscettibilità

CYP-dependent metabolism of PF9601N, a new monoamine oxidase-B inhibitor, by C57BL/6 mouse and human liver microsomes

The selective monoamine oxidase-B (MAO-B) inhibitor, ldeprenyl, is still used for treating Parkinson's patients, however, a disadvantage of its use lies in the formation of l-amphetamine and lmethamphetamine. Subsequently, this has promoted the design of a novel, more potent, MAO-B inhibitor PF9601N, which also has neuroprotective and antioxidant properties. The aim of this work was to investigate the effect of treatment with PF9601N on its own phase I hepatic metabolism. Kinetic parameters of PF9601N CYP-dependent N-dealkylation reaction was also studied and compared with those of l-deprenyl. Methods. C57BL/6 mice were treated with PF9601N for 4 days. After CYP content and related monooxygenase activities were assayed in liver microsomes of control and treated animals. Results. CYP activities, cytochrome b5 content, NADPH-cytochrome P450 reductase and various monooxygenase activities were unaffected by in vivo PF9601N treatment. With microsomes from both control and treated mice, the PF9601N-dealkylation product, FA72, was the only detected metabolite with its formation rate following an hyperbolic, Michaelis-Menten curve. Among various inhibitors, only ketoconazole inhibited the FA72 formation rate, indicating a major involvement for CYP3A. Apparent Km and Vmax values generated by human liver microsomes were similar to those found with mouse microsomes. Ketoconazole inhibition indicates that CYP3A is one of the major enzymes involved in PF9601N metabolism also by human liver microsomes. In mouse liver microsomes, the intrinsic clearance of PF9601N was significantly lower than that of ldeprenyl suggestive of an improved bioavailability for the former. Conclusion. The observed favourable metabolic profile may suggest suitability of PF9601N for clinical use